diff --git a/packages/squiggle-lang/__tests__/Reducer/Reducer_Dispatch/Reducer_Dispatch_BuiltIn_test.res b/packages/squiggle-lang/__tests__/Reducer/Reducer_Dispatch/Reducer_Dispatch_BuiltIn_test.res
index f3c92f78..4932af3b 100644
--- a/packages/squiggle-lang/__tests__/Reducer/Reducer_Dispatch/Reducer_Dispatch_BuiltIn_test.res
+++ b/packages/squiggle-lang/__tests__/Reducer/Reducer_Dispatch/Reducer_Dispatch_BuiltIn_test.res
@@ -1,10 +1,14 @@
-module ExpressionValue = ReducerInterface.ExternalExpressionValue
+module ExpressionValue = ReducerInterface.InternalExpressionValue
+module Expression = Reducer_Expression
 
 open Jest
 open Expect
 
-let expectEvalToBe = (expr: string, answer: string) =>
-  Reducer.evaluate(expr)->ExpressionValue.toStringResult->expect->toBe(answer)
+let expectEvalToBe = (sourceCode: string, answer: string) =>
+  Expression.BackCompatible.evaluateString(sourceCode)
+  ->ExpressionValue.toStringResult
+  ->expect
+  ->toBe(answer)
 
 let testEval = (expr, answer) => test(expr, () => expectEvalToBe(expr, answer))
 
diff --git a/packages/squiggle-lang/__tests__/Reducer/Reducer_Helpers.res b/packages/squiggle-lang/__tests__/Reducer/Reducer_Helpers.res
index 05eb1b01..e915bfc1 100644
--- a/packages/squiggle-lang/__tests__/Reducer/Reducer_Helpers.res
+++ b/packages/squiggle-lang/__tests__/Reducer/Reducer_Helpers.res
@@ -1,6 +1,5 @@
 // Reducer_Helpers
 module ErrorValue = Reducer_ErrorValue
-module ExternalExpressionValue = ReducerInterface.ExternalExpressionValue
 module InternalExpressionValue = ReducerInterface.InternalExpressionValue
 module Bindings = Reducer_Bindings
 
@@ -15,8 +14,4 @@ let removeDefaultsInternal = (iev: InternalExpressionValue.t) => {
   }
 }
 
-let removeDefaultsExternal = (ev: ExternalExpressionValue.t): ExternalExpressionValue.t =>
-  ev->InternalExpressionValue.toInternal->removeDefaultsInternal->InternalExpressionValue.toExternal
-
 let rRemoveDefaultsInternal = r => Belt.Result.map(r, removeDefaultsInternal)
-let rRemoveDefaultsExternal = r => Belt.Result.map(r, removeDefaultsExternal)
diff --git a/packages/squiggle-lang/__tests__/Reducer/Reducer_MathJs/Reducer_MathJsEval_test.res b/packages/squiggle-lang/__tests__/Reducer/Reducer_MathJs/Reducer_MathJsEval_test.res
index ed00e957..e56c04d7 100644
--- a/packages/squiggle-lang/__tests__/Reducer/Reducer_MathJs/Reducer_MathJsEval_test.res
+++ b/packages/squiggle-lang/__tests__/Reducer/Reducer_MathJs/Reducer_MathJsEval_test.res
@@ -1,5 +1,5 @@
 module MathJs = Reducer_MathJs
-module ErrorValue = Reducer.ErrorValue
+module ErrorValue = Reducer_ErrorValue
 
 open Jest
 open ExpectJs
diff --git a/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_Parse_test.res b/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_Parse_test.res
index f17fe9aa..80093afb 100644
--- a/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_Parse_test.res
+++ b/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_Parse_test.res
@@ -3,359 +3,464 @@ open Reducer_Peggy_TestHelpers
 
 describe("Peggy parse", () => {
   describe("float", () => {
-    testParse("1.", "{1}")
-    testParse("1.1", "{1.1}")
-    testParse(".1", "{0.1}")
-    testParse("0.1", "{0.1}")
-    testParse("1e1", "{10}")
-    testParse("1e-1", "{0.1}")
-    testParse(".1e1", "{1}")
-    testParse("0.1e1", "{1}")
+    testParse("1.", "{(::$_endOfOuterBlock_$ () 1)}")
+    testParse("1.1", "{(::$_endOfOuterBlock_$ () 1.1)}")
+    testParse(".1", "{(::$_endOfOuterBlock_$ () 0.1)}")
+    testParse("0.1", "{(::$_endOfOuterBlock_$ () 0.1)}")
+    testParse("1e1", "{(::$_endOfOuterBlock_$ () 10)}")
+    testParse("1e-1", "{(::$_endOfOuterBlock_$ () 0.1)}")
+    testParse(".1e1", "{(::$_endOfOuterBlock_$ () 1)}")
+    testParse("0.1e1", "{(::$_endOfOuterBlock_$ () 1)}")
   })
 
   describe("literals operators parenthesis", () => {
     // Note that there is always an outer block. Otherwise, external bindings are ignrored at the first statement
-    testParse("1", "{1}")
-    testParse("'hello'", "{'hello'}")
-    testParse("true", "{true}")
-    testParse("1+2", "{(::add 1 2)}")
-    testParse("add(1,2)", "{(::add 1 2)}")
-    testParse("(1)", "{1}")
-    testParse("(1+2)", "{(::add 1 2)}")
+    testParse("1", "{(::$_endOfOuterBlock_$ () 1)}")
+    testParse("'hello'", "{(::$_endOfOuterBlock_$ () 'hello')}")
+    testParse("true", "{(::$_endOfOuterBlock_$ () true)}")
+    testParse("1+2", "{(::$_endOfOuterBlock_$ () (::add 1 2))}")
+    testParse("add(1,2)", "{(::$_endOfOuterBlock_$ () (::add 1 2))}")
+    testParse("(1)", "{(::$_endOfOuterBlock_$ () 1)}")
+    testParse("(1+2)", "{(::$_endOfOuterBlock_$ () (::add 1 2))}")
   })
 
   describe("unary", () => {
-    testParse("-1", "{(::unaryMinus 1)}")
-    testParse("!true", "{(::not true)}")
-    testParse("1 + -1", "{(::add 1 (::unaryMinus 1))}")
-    testParse("-a[0]", "{(::unaryMinus (::$_atIndex_$ :a 0))}")
-    testParse("!a[0]", "{(::not (::$_atIndex_$ :a 0))}")
+    testParse("-1", "{(::$_endOfOuterBlock_$ () (::unaryMinus 1))}")
+    testParse("!true", "{(::$_endOfOuterBlock_$ () (::not true))}")
+    testParse("1 + -1", "{(::$_endOfOuterBlock_$ () (::add 1 (::unaryMinus 1)))}")
+    testParse("-a[0]", "{(::$_endOfOuterBlock_$ () (::unaryMinus (::$_atIndex_$ :a 0)))}")
+    testParse("!a[0]", "{(::$_endOfOuterBlock_$ () (::not (::$_atIndex_$ :a 0)))}")
   })
 
   describe("multiplicative", () => {
-    testParse("1 * 2", "{(::multiply 1 2)}")
-    testParse("1 / 2", "{(::divide 1 2)}")
-    testParse("1 * 2 * 3", "{(::multiply (::multiply 1 2) 3)}")
-    testParse("1 * 2 / 3", "{(::divide (::multiply 1 2) 3)}")
-    testParse("1 / 2 * 3", "{(::multiply (::divide 1 2) 3)}")
-    testParse("1 / 2 / 3", "{(::divide (::divide 1 2) 3)}")
-    testParse("1 * 2 + 3 * 4", "{(::add (::multiply 1 2) (::multiply 3 4))}")
-    testParse("1 * 2 - 3 * 4", "{(::subtract (::multiply 1 2) (::multiply 3 4))}")
-    testParse("1 * 2 .+ 3 * 4", "{(::dotAdd (::multiply 1 2) (::multiply 3 4))}")
-    testParse("1 * 2 .- 3 * 4", "{(::dotSubtract (::multiply 1 2) (::multiply 3 4))}")
-    testParse("1 * 2 + 3 .* 4", "{(::add (::multiply 1 2) (::dotMultiply 3 4))}")
-    testParse("1 * 2 + 3 / 4", "{(::add (::multiply 1 2) (::divide 3 4))}")
-    testParse("1 * 2 + 3 ./ 4", "{(::add (::multiply 1 2) (::dotDivide 3 4))}")
-    testParse("1 * 2 - 3 .* 4", "{(::subtract (::multiply 1 2) (::dotMultiply 3 4))}")
-    testParse("1 * 2 - 3 / 4", "{(::subtract (::multiply 1 2) (::divide 3 4))}")
-    testParse("1 * 2 - 3 ./ 4", "{(::subtract (::multiply 1 2) (::dotDivide 3 4))}")
-    testParse("1 * 2 - 3 * 4^5", "{(::subtract (::multiply 1 2) (::multiply 3 (::pow 4 5)))}")
+    testParse("1 * 2", "{(::$_endOfOuterBlock_$ () (::multiply 1 2))}")
+    testParse("1 / 2", "{(::$_endOfOuterBlock_$ () (::divide 1 2))}")
+    testParse("1 * 2 * 3", "{(::$_endOfOuterBlock_$ () (::multiply (::multiply 1 2) 3))}")
+    testParse("1 * 2 / 3", "{(::$_endOfOuterBlock_$ () (::divide (::multiply 1 2) 3))}")
+    testParse("1 / 2 * 3", "{(::$_endOfOuterBlock_$ () (::multiply (::divide 1 2) 3))}")
+    testParse("1 / 2 / 3", "{(::$_endOfOuterBlock_$ () (::divide (::divide 1 2) 3))}")
+    testParse(
+      "1 * 2 + 3 * 4",
+      "{(::$_endOfOuterBlock_$ () (::add (::multiply 1 2) (::multiply 3 4)))}",
+    )
+    testParse(
+      "1 * 2 - 3 * 4",
+      "{(::$_endOfOuterBlock_$ () (::subtract (::multiply 1 2) (::multiply 3 4)))}",
+    )
+    testParse(
+      "1 * 2 .+ 3 * 4",
+      "{(::$_endOfOuterBlock_$ () (::dotAdd (::multiply 1 2) (::multiply 3 4)))}",
+    )
+    testParse(
+      "1 * 2 .- 3 * 4",
+      "{(::$_endOfOuterBlock_$ () (::dotSubtract (::multiply 1 2) (::multiply 3 4)))}",
+    )
+    testParse(
+      "1 * 2 + 3 .* 4",
+      "{(::$_endOfOuterBlock_$ () (::add (::multiply 1 2) (::dotMultiply 3 4)))}",
+    )
+    testParse(
+      "1 * 2 + 3 / 4",
+      "{(::$_endOfOuterBlock_$ () (::add (::multiply 1 2) (::divide 3 4)))}",
+    )
+    testParse(
+      "1 * 2 + 3 ./ 4",
+      "{(::$_endOfOuterBlock_$ () (::add (::multiply 1 2) (::dotDivide 3 4)))}",
+    )
+    testParse(
+      "1 * 2 - 3 .* 4",
+      "{(::$_endOfOuterBlock_$ () (::subtract (::multiply 1 2) (::dotMultiply 3 4)))}",
+    )
+    testParse(
+      "1 * 2 - 3 / 4",
+      "{(::$_endOfOuterBlock_$ () (::subtract (::multiply 1 2) (::divide 3 4)))}",
+    )
+    testParse(
+      "1 * 2 - 3 ./ 4",
+      "{(::$_endOfOuterBlock_$ () (::subtract (::multiply 1 2) (::dotDivide 3 4)))}",
+    )
+    testParse(
+      "1 * 2 - 3 * 4^5",
+      "{(::$_endOfOuterBlock_$ () (::subtract (::multiply 1 2) (::multiply 3 (::pow 4 5))))}",
+    )
     testParse(
       "1 * 2 - 3 * 4^5^6",
-      "{(::subtract (::multiply 1 2) (::multiply 3 (::pow (::pow 4 5) 6)))}",
+      "{(::$_endOfOuterBlock_$ () (::subtract (::multiply 1 2) (::multiply 3 (::pow (::pow 4 5) 6))))}",
+    )
+    testParse(
+      "1 * -a[-2]",
+      "{(::$_endOfOuterBlock_$ () (::multiply 1 (::unaryMinus (::$_atIndex_$ :a (::unaryMinus 2)))))}",
     )
-    testParse("1 * -a[-2]", "{(::multiply 1 (::unaryMinus (::$_atIndex_$ :a (::unaryMinus 2))))}")
   })
 
   describe("multi-line", () => {
-    testParse("x=1; 2", "{:x = {1}; 2}")
-    testParse("x=1; y=2", "{:x = {1}; :y = {2}}")
+    testParse("x=1; 2", "{:x = {1}; (::$_endOfOuterBlock_$ () 2)}")
+    testParse("x=1; y=2", "{:x = {1}; :y = {2}; (::$_endOfOuterBlock_$ () ())}")
   })
 
   describe("variables", () => {
-    testParse("x = 1", "{:x = {1}}")
-    testParse("x", "{:x}")
-    testParse("x = 1; x", "{:x = {1}; :x}")
+    testParse("x = 1", "{:x = {1}; (::$_endOfOuterBlock_$ () ())}")
+    testParse("x", "{(::$_endOfOuterBlock_$ () :x)}")
+    testParse("x = 1; x", "{:x = {1}; (::$_endOfOuterBlock_$ () :x)}")
   })
 
   describe("functions", () => {
-    testParse("identity(x) = x", "{:identity = {|:x| {:x}}}") // Function definitions become lambda assignments
-    testParse("identity(x)", "{(::identity :x)}")
+    testParse("identity(x) = x", "{:identity = {|:x| {:x}}; (::$_endOfOuterBlock_$ () ())}") // Function definitions become lambda assignments
+    testParse("identity(x)", "{(::$_endOfOuterBlock_$ () (::identity :x))}")
   })
 
   describe("arrays", () => {
-    testParse("[]", "{(::$_constructArray_$ ())}")
-    testParse("[0, 1, 2]", "{(::$_constructArray_$ (0 1 2))}")
-    testParse("['hello', 'world']", "{(::$_constructArray_$ ('hello' 'world'))}")
-    testParse("([0,1,2])[1]", "{(::$_atIndex_$ (::$_constructArray_$ (0 1 2)) 1)}")
+    testParse("[]", "{(::$_endOfOuterBlock_$ () (::$_constructArray_$ ()))}")
+    testParse("[0, 1, 2]", "{(::$_endOfOuterBlock_$ () (::$_constructArray_$ (0 1 2)))}")
+    testParse(
+      "['hello', 'world']",
+      "{(::$_endOfOuterBlock_$ () (::$_constructArray_$ ('hello' 'world')))}",
+    )
+    testParse(
+      "([0,1,2])[1]",
+      "{(::$_endOfOuterBlock_$ () (::$_atIndex_$ (::$_constructArray_$ (0 1 2)) 1))}",
+    )
   })
 
   describe("records", () => {
-    testParse("{a: 1, b: 2}", "{(::$_constructRecord_$ ('a': 1 'b': 2))}")
-    testParse("{1+0: 1, 2+0: 2}", "{(::$_constructRecord_$ ((::add 1 0): 1 (::add 2 0): 2))}") // key can be any expression
-    testParse("record.property", "{(::$_atIndex_$ :record 'property')}")
+    testParse(
+      "{a: 1, b: 2}",
+      "{(::$_endOfOuterBlock_$ () (::$_constructRecord_$ ('a': 1 'b': 2)))}",
+    )
+    testParse(
+      "{1+0: 1, 2+0: 2}",
+      "{(::$_endOfOuterBlock_$ () (::$_constructRecord_$ ((::add 1 0): 1 (::add 2 0): 2)))}",
+    ) // key can be any expression
+    testParse("record.property", "{(::$_endOfOuterBlock_$ () (::$_atIndex_$ :record 'property'))}")
   })
 
   describe("post operators", () => {
     //function call, array and record access are post operators with higher priority than unary operators
-    testParse("a==!b(1)", "{(::equal :a (::not (::b 1)))}")
-    testParse("a==!b[1]", "{(::equal :a (::not (::$_atIndex_$ :b 1)))}")
-    testParse("a==!b.one", "{(::equal :a (::not (::$_atIndex_$ :b 'one')))}")
+    testParse("a==!b(1)", "{(::$_endOfOuterBlock_$ () (::equal :a (::not (::b 1))))}")
+    testParse("a==!b[1]", "{(::$_endOfOuterBlock_$ () (::equal :a (::not (::$_atIndex_$ :b 1))))}")
+    testParse(
+      "a==!b.one",
+      "{(::$_endOfOuterBlock_$ () (::equal :a (::not (::$_atIndex_$ :b 'one'))))}",
+    )
   })
 
   describe("comments", () => {
-    testParse("1 # This is a line comment", "{1}")
-    testParse("1 // This is a line comment", "{1}")
-    testParse("1 /* This is a multi line comment */", "{1}")
-    testParse("/* This is a multi line comment */ 1", "{1}")
+    testParse("1 # This is a line comment", "{(::$_endOfOuterBlock_$ () 1)}")
+    testParse("1 // This is a line comment", "{(::$_endOfOuterBlock_$ () 1)}")
+    testParse("1 /* This is a multi line comment */", "{(::$_endOfOuterBlock_$ () 1)}")
+    testParse("/* This is a multi line comment */ 1", "{(::$_endOfOuterBlock_$ () 1)}")
     testParse(
       `
-    /* This is 
-    a multi line 
-    comment */
-    1`,
-      "{1}",
+  /* This is 
+  a multi line 
+  comment */
+  1`,
+      "{(::$_endOfOuterBlock_$ () 1)}",
     )
   })
 
   describe("ternary operator", () => {
-    testParse("true ? 2 : 3", "{(::$$_ternary_$$ true 2 3)}")
+    testParse("true ? 2 : 3", "{(::$_endOfOuterBlock_$ () (::$$_ternary_$$ true 2 3))}")
     testParse(
       "false ? 2 : false ? 4 : 5",
-      "{(::$$_ternary_$$ false 2 (::$$_ternary_$$ false 4 5))}",
+      "{(::$_endOfOuterBlock_$ () (::$$_ternary_$$ false 2 (::$$_ternary_$$ false 4 5)))}",
     ) // nested ternary
   })
 
   describe("if then else", () => {
-    testParse("if true then 2 else 3", "{(::$$_ternary_$$ true {2} {3})}")
-    testParse("if false then {2} else {3}", "{(::$$_ternary_$$ false {2} {3})}")
+    testParse(
+      "if true then 2 else 3",
+      "{(::$_endOfOuterBlock_$ () (::$$_ternary_$$ true {2} {3}))}",
+    )
+    testParse(
+      "if false then {2} else {3}",
+      "{(::$_endOfOuterBlock_$ () (::$$_ternary_$$ false {2} {3}))}",
+    )
     testParse(
       "if false then {2} else if false then {4} else {5}",
-      "{(::$$_ternary_$$ false {2} (::$$_ternary_$$ false {4} {5}))}",
+      "{(::$_endOfOuterBlock_$ () (::$$_ternary_$$ false {2} (::$$_ternary_$$ false {4} {5})))}",
     ) //nested if
   })
 
   describe("logical", () => {
-    testParse("true || false", "{(::or true false)}")
-    testParse("true && false", "{(::and true false)}")
-    testParse("a * b + c", "{(::add (::multiply :a :b) :c)}") // for comparison
-    testParse("a && b || c", "{(::or (::and :a :b) :c)}")
-    testParse("a && b || c && d", "{(::or (::and :a :b) (::and :c :d))}")
-    testParse("a && !b || c", "{(::or (::and :a (::not :b)) :c)}")
-    testParse("a && b==c || d", "{(::or (::and :a (::equal :b :c)) :d)}")
-    testParse("a && b!=c || d", "{(::or (::and :a (::unequal :b :c)) :d)}")
-    testParse("a && !(b==c) || d", "{(::or (::and :a (::not (::equal :b :c))) :d)}")
-    testParse("a && b>=c || d", "{(::or (::and :a (::largerEq :b :c)) :d)}")
-    testParse("a && !(b>=c) || d", "{(::or (::and :a (::not (::largerEq :b :c))) :d)}")
-    testParse("a && b<=c || d", "{(::or (::and :a (::smallerEq :b :c)) :d)}")
-    testParse("a && b>c || d", "{(::or (::and :a (::larger :b :c)) :d)}")
-    testParse("a && b<c || d", "{(::or (::and :a (::smaller :b :c)) :d)}")
-    testParse("a && b<c[i] || d", "{(::or (::and :a (::smaller :b (::$_atIndex_$ :c :i))) :d)}")
-    testParse("a && b<c.i || d", "{(::or (::and :a (::smaller :b (::$_atIndex_$ :c 'i'))) :d)}")
-    testParse("a && b<c(i) || d", "{(::or (::and :a (::smaller :b (::c :i))) :d)}")
-    testParse("a && b<1+2 || d", "{(::or (::and :a (::smaller :b (::add 1 2))) :d)}")
+    testParse("true || false", "{(::$_endOfOuterBlock_$ () (::or true false))}")
+    testParse("true && false", "{(::$_endOfOuterBlock_$ () (::and true false))}")
+    testParse("a * b + c", "{(::$_endOfOuterBlock_$ () (::add (::multiply :a :b) :c))}") // for comparison
+    testParse("a && b || c", "{(::$_endOfOuterBlock_$ () (::or (::and :a :b) :c))}")
+    testParse("a && b || c && d", "{(::$_endOfOuterBlock_$ () (::or (::and :a :b) (::and :c :d)))}")
+    testParse("a && !b || c", "{(::$_endOfOuterBlock_$ () (::or (::and :a (::not :b)) :c))}")
+    testParse("a && b==c || d", "{(::$_endOfOuterBlock_$ () (::or (::and :a (::equal :b :c)) :d))}")
+    testParse(
+      "a && b!=c || d",
+      "{(::$_endOfOuterBlock_$ () (::or (::and :a (::unequal :b :c)) :d))}",
+    )
+    testParse(
+      "a && !(b==c) || d",
+      "{(::$_endOfOuterBlock_$ () (::or (::and :a (::not (::equal :b :c))) :d))}",
+    )
+    testParse(
+      "a && b>=c || d",
+      "{(::$_endOfOuterBlock_$ () (::or (::and :a (::largerEq :b :c)) :d))}",
+    )
+    testParse(
+      "a && !(b>=c) || d",
+      "{(::$_endOfOuterBlock_$ () (::or (::and :a (::not (::largerEq :b :c))) :d))}",
+    )
+    testParse(
+      "a && b<=c || d",
+      "{(::$_endOfOuterBlock_$ () (::or (::and :a (::smallerEq :b :c)) :d))}",
+    )
+    testParse("a && b>c || d", "{(::$_endOfOuterBlock_$ () (::or (::and :a (::larger :b :c)) :d))}")
+    testParse(
+      "a && b<c || d",
+      "{(::$_endOfOuterBlock_$ () (::or (::and :a (::smaller :b :c)) :d))}",
+    )
+    testParse(
+      "a && b<c[i] || d",
+      "{(::$_endOfOuterBlock_$ () (::or (::and :a (::smaller :b (::$_atIndex_$ :c :i))) :d))}",
+    )
+    testParse(
+      "a && b<c.i || d",
+      "{(::$_endOfOuterBlock_$ () (::or (::and :a (::smaller :b (::$_atIndex_$ :c 'i'))) :d))}",
+    )
+    testParse(
+      "a && b<c(i) || d",
+      "{(::$_endOfOuterBlock_$ () (::or (::and :a (::smaller :b (::c :i))) :d))}",
+    )
+    testParse(
+      "a && b<1+2 || d",
+      "{(::$_endOfOuterBlock_$ () (::or (::and :a (::smaller :b (::add 1 2))) :d))}",
+    )
     testParse(
       "a && b<1+2*3 || d",
-      "{(::or (::and :a (::smaller :b (::add 1 (::multiply 2 3)))) :d)}",
+      "{(::$_endOfOuterBlock_$ () (::or (::and :a (::smaller :b (::add 1 (::multiply 2 3)))) :d))}",
     )
     testParse(
       "a && b<1+2*-3+4 || d",
-      "{(::or (::and :a (::smaller :b (::add (::add 1 (::multiply 2 (::unaryMinus 3))) 4))) :d)}",
+      "{(::$_endOfOuterBlock_$ () (::or (::and :a (::smaller :b (::add (::add 1 (::multiply 2 (::unaryMinus 3))) 4))) :d))}",
     )
     testParse(
       "a && b<1+2*3 || d ? true : false",
-      "{(::$$_ternary_$$ (::or (::and :a (::smaller :b (::add 1 (::multiply 2 3)))) :d) true false)}",
+      "{(::$_endOfOuterBlock_$ () (::$$_ternary_$$ (::or (::and :a (::smaller :b (::add 1 (::multiply 2 3)))) :d) true false))}",
     )
   })
 
   describe("pipe", () => {
-    testParse("1 -> add(2)", "{(::add 1 2)}")
-    testParse("-1 -> add(2)", "{(::add (::unaryMinus 1) 2)}")
-    testParse("-a[1] -> add(2)", "{(::add (::unaryMinus (::$_atIndex_$ :a 1)) 2)}")
-    testParse("-f(1) -> add(2)", "{(::add (::unaryMinus (::f 1)) 2)}")
-    testParse("1 + 2 -> add(3)", "{(::add 1 (::add 2 3))}")
-    testParse("1 -> add(2) * 3", "{(::multiply (::add 1 2) 3)}")
-    testParse("1 -> subtract(2)", "{(::subtract 1 2)}")
-    testParse("-1 -> subtract(2)", "{(::subtract (::unaryMinus 1) 2)}")
-    testParse("1 -> subtract(2) * 3", "{(::multiply (::subtract 1 2) 3)}")
+    testParse("1 -> add(2)", "{(::$_endOfOuterBlock_$ () (::add 1 2))}")
+    testParse("-1 -> add(2)", "{(::$_endOfOuterBlock_$ () (::add (::unaryMinus 1) 2))}")
+    testParse(
+      "-a[1] -> add(2)",
+      "{(::$_endOfOuterBlock_$ () (::add (::unaryMinus (::$_atIndex_$ :a 1)) 2))}",
+    )
+    testParse("-f(1) -> add(2)", "{(::$_endOfOuterBlock_$ () (::add (::unaryMinus (::f 1)) 2))}")
+    testParse("1 + 2 -> add(3)", "{(::$_endOfOuterBlock_$ () (::add 1 (::add 2 3)))}")
+    testParse("1 -> add(2) * 3", "{(::$_endOfOuterBlock_$ () (::multiply (::add 1 2) 3))}")
+    testParse("1 -> subtract(2)", "{(::$_endOfOuterBlock_$ () (::subtract 1 2))}")
+    testParse("-1 -> subtract(2)", "{(::$_endOfOuterBlock_$ () (::subtract (::unaryMinus 1) 2))}")
+    testParse(
+      "1 -> subtract(2) * 3",
+      "{(::$_endOfOuterBlock_$ () (::multiply (::subtract 1 2) 3))}",
+    )
   })
 
   describe("elixir pipe", () => {
     //handled together with -> so there is no need for seperate tests
-    testParse("1 |> add(2)", "{(::add 1 2)}")
+    testParse("1 |> add(2)", "{(::$_endOfOuterBlock_$ () (::add 1 2))}")
   })
 
   describe("to", () => {
-    testParse("1 to 2", "{(::credibleIntervalToDistribution 1 2)}")
-    testParse("-1 to -2", "{(::credibleIntervalToDistribution (::unaryMinus 1) (::unaryMinus 2))}") // lower than unary
+    testParse("1 to 2", "{(::$_endOfOuterBlock_$ () (::credibleIntervalToDistribution 1 2))}")
+    testParse(
+      "-1 to -2",
+      "{(::$_endOfOuterBlock_$ () (::credibleIntervalToDistribution (::unaryMinus 1) (::unaryMinus 2)))}",
+    ) // lower than unary
     testParse(
       "a[1] to a[2]",
-      "{(::credibleIntervalToDistribution (::$_atIndex_$ :a 1) (::$_atIndex_$ :a 2))}",
+      "{(::$_endOfOuterBlock_$ () (::credibleIntervalToDistribution (::$_atIndex_$ :a 1) (::$_atIndex_$ :a 2)))}",
     ) // lower than post
     testParse(
       "a.p1 to a.p2",
-      "{(::credibleIntervalToDistribution (::$_atIndex_$ :a 'p1') (::$_atIndex_$ :a 'p2'))}",
+      "{(::$_endOfOuterBlock_$ () (::credibleIntervalToDistribution (::$_atIndex_$ :a 'p1') (::$_atIndex_$ :a 'p2')))}",
     ) // lower than post
-    testParse("1 to 2 + 3", "{(::add (::credibleIntervalToDistribution 1 2) 3)}") // higher than binary operators
+    testParse(
+      "1 to 2 + 3",
+      "{(::$_endOfOuterBlock_$ () (::add (::credibleIntervalToDistribution 1 2) 3))}",
+    ) // higher than binary operators
     testParse(
       "1->add(2) to 3->add(4) -> add(4)",
-      "{(::credibleIntervalToDistribution (::add 1 2) (::add (::add 3 4) 4))}",
+      "{(::$_endOfOuterBlock_$ () (::credibleIntervalToDistribution (::add 1 2) (::add (::add 3 4) 4)))}",
     ) // lower than chain
   })
 
   describe("inner block", () => {
     // inner blocks are 0 argument lambdas. They can be used whenever a value is required.
     // Like lambdas they have a local scope.
-    testParse("x={y=1; y}; x", "{:x = {:y = {1}; :y}; :x}")
+    testParse("x={y=1; y}; x", "{:x = {:y = {1}; :y}; (::$_endOfOuterBlock_$ () :x)}")
   })
 
   describe("lambda", () => {
-    testParse("{|x| x}", "{{|:x| {:x}}}")
-    testParse("f={|x| x}", "{:f = {{|:x| {:x}}}}")
-    testParse("f(x)=x", "{:f = {|:x| {:x}}}") // Function definitions are lambda assignments
-    testParse("f(x)=x ? 1 : 0", "{:f = {|:x| {(::$$_ternary_$$ :x 1 0)}}}") // Function definitions are lambda assignments
+    testParse("{|x| x}", "{(::$_endOfOuterBlock_$ () {|:x| {:x}})}")
+    testParse("f={|x| x}", "{:f = {{|:x| {:x}}}; (::$_endOfOuterBlock_$ () ())}")
+    testParse("f(x)=x", "{:f = {|:x| {:x}}; (::$_endOfOuterBlock_$ () ())}") // Function definitions are lambda assignments
+    testParse(
+      "f(x)=x ? 1 : 0",
+      "{:f = {|:x| {(::$$_ternary_$$ :x 1 0)}}; (::$_endOfOuterBlock_$ () ())}",
+    ) // Function definitions are lambda assignments
   })
 
   describe("Using lambda as value", () => {
     testParse(
       "myadd(x,y)=x+y; z=myadd; z",
-      "{:myadd = {|:x,:y| {(::add :x :y)}}; :z = {:myadd}; :z}",
+      "{:myadd = {|:x,:y| {(::add :x :y)}}; :z = {:myadd}; (::$_endOfOuterBlock_$ () :z)}",
     )
     testParse(
       "myadd(x,y)=x+y; z=[myadd]; z",
-      "{:myadd = {|:x,:y| {(::add :x :y)}}; :z = {(::$_constructArray_$ (:myadd))}; :z}",
+      "{:myadd = {|:x,:y| {(::add :x :y)}}; :z = {(::$_constructArray_$ (:myadd))}; (::$_endOfOuterBlock_$ () :z)}",
     )
     testParse(
       "myaddd(x,y)=x+y; z={x: myaddd}; z",
-      "{:myaddd = {|:x,:y| {(::add :x :y)}}; :z = {(::$_constructRecord_$ ('x': :myaddd))}; :z}",
+      "{:myaddd = {|:x,:y| {(::add :x :y)}}; :z = {(::$_constructRecord_$ ('x': :myaddd))}; (::$_endOfOuterBlock_$ () :z)}",
+    )
+    testParse("f({|x| x+1})", "{(::$_endOfOuterBlock_$ () (::f {|:x| {(::add :x 1)}}))}")
+    testParse(
+      "map(arr, {|x| x+1})",
+      "{(::$_endOfOuterBlock_$ () (::map :arr {|:x| {(::add :x 1)}}))}",
     )
-    testParse("f({|x| x+1})", "{(::f {|:x| {(::add :x 1)}})}")
-    testParse("map(arr, {|x| x+1})", "{(::map :arr {|:x| {(::add :x 1)}})}")
     testParse(
       "map([1,2,3], {|x| x+1})",
-      "{(::map (::$_constructArray_$ (1 2 3)) {|:x| {(::add :x 1)}})}",
+      "{(::$_endOfOuterBlock_$ () (::map (::$_constructArray_$ (1 2 3)) {|:x| {(::add :x 1)}}))}",
     )
     testParse(
       "[1,2,3]->map({|x| x+1})",
-      "{(::map (::$_constructArray_$ (1 2 3)) {|:x| {(::add :x 1)}})}",
+      "{(::$_endOfOuterBlock_$ () (::map (::$_constructArray_$ (1 2 3)) {|:x| {(::add :x 1)}}))}",
     )
   })
   describe("unit", () => {
-    testParse("1m", "{(::fromUnit_m 1)}")
-    testParse("1M", "{(::fromUnit_M 1)}")
-    testParse("1m+2cm", "{(::add (::fromUnit_m 1) (::fromUnit_cm 2))}")
+    testParse("1m", "{(::$_endOfOuterBlock_$ () (::fromUnit_m 1))}")
+    testParse("1M", "{(::$_endOfOuterBlock_$ () (::fromUnit_M 1))}")
+    testParse("1m+2cm", "{(::$_endOfOuterBlock_$ () (::add (::fromUnit_m 1) (::fromUnit_cm 2)))}")
   })
   describe("Module", () => {
-    testParse("x", "{:x}")
-    testParse("Math.pi", "{:Math.pi}")
+    testParse("x", "{(::$_endOfOuterBlock_$ () :x)}")
+    testParse("Math.pi", "{(::$_endOfOuterBlock_$ () :Math.pi)}")
   })
 })
 
 describe("parsing new line", () => {
   testParse(
     `
-  a + 
-  b`,
-    "{(::add :a :b)}",
+ a + 
+ b`,
+    "{(::$_endOfOuterBlock_$ () (::add :a :b))}",
   )
   testParse(
     `
-  x=
-  1`,
-    "{:x = {1}}",
+ x=
+ 1`,
+    "{:x = {1}; (::$_endOfOuterBlock_$ () ())}",
   )
   testParse(
     `
-  x=1
-  y=2`,
-    "{:x = {1}; :y = {2}}",
+ x=1
+ y=2`,
+    "{:x = {1}; :y = {2}; (::$_endOfOuterBlock_$ () ())}",
   )
   testParse(
     `
-  x={
-   y=2;
-   y }
-  x`,
-    "{:x = {:y = {2}; :y}; :x}",
+ x={
+  y=2;
+  y }
+ x`,
+    "{:x = {:y = {2}; :y}; (::$_endOfOuterBlock_$ () :x)}",
   )
   testParse(
     `
-  x={
-   y=2
-   y }
-  x`,
-    "{:x = {:y = {2}; :y}; :x}",
+ x={
+  y=2
+  y }
+ x`,
+    "{:x = {:y = {2}; :y}; (::$_endOfOuterBlock_$ () :x)}",
   )
   testParse(
     `
-  x={
-   y=2
-   y 
-   }
-  x`,
-    "{:x = {:y = {2}; :y}; :x}",
+ x={
+  y=2
+  y 
+  }
+ x`,
+    "{:x = {:y = {2}; :y}; (::$_endOfOuterBlock_$ () :x)}",
   )
   testParse(
     `
+ x=1
+ y=2
+ z=3
+ `,
+    "{:x = {1}; :y = {2}; :z = {3}; (::$_endOfOuterBlock_$ () ())}",
+  )
+  testParse(
+    `
+ f={
   x=1
   y=2
   z=3
-  `,
-    "{:x = {1}; :y = {2}; :z = {3}}",
+  x+y+z
+ }
+ `,
+    "{:f = {:x = {1}; :y = {2}; :z = {3}; (::add (::add :x :y) :z)}; (::$_endOfOuterBlock_$ () ())}",
   )
   testParse(
     `
-  f={
-    x=1
-    y=2
-    z=3
-    x+y+z
+ f={
+  x=1
+  y=2
+  z=3
+  x+y+z
+ }
+ g=f+4
+ g
+ `,
+    "{:f = {:x = {1}; :y = {2}; :z = {3}; (::add (::add :x :y) :z)}; :g = {(::add :f 4)}; (::$_endOfOuterBlock_$ () :g)}",
+  )
+  testParse(
+    `
+ f =
+  {
+   x=1; //x
+   y=2 //y
+   z=
+    3
+   x+
+    y+
+    z
   }
-  `,
-    "{:f = {:x = {1}; :y = {2}; :z = {3}; (::add (::add :x :y) :z)}}",
+ g =
+  f +
+   4
+ g ->
+  h ->
+  p ->
+  q 
+ `,
+    "{:f = {:x = {1}; :y = {2}; :z = {3}; (::add (::add :x :y) :z)}; :g = {(::add :f 4)}; (::$_endOfOuterBlock_$ () (::q (::p (::h :g))))}",
   )
   testParse(
     `
-  f={
-    x=1
-    y=2
-    z=3
-    x+y+z
-  }
-  g=f+4
-  g
-  `,
-    "{:f = {:x = {1}; :y = {2}; :z = {3}; (::add (::add :x :y) :z)}; :g = {(::add :f 4)}; :g}",
+  a |>
+  b |>
+  c |>
+  d 
+ `,
+    "{(::$_endOfOuterBlock_$ () (::d (::c (::b :a))))}",
   )
   testParse(
     `
-  f =
-    {
-      x=1; //x
-      y=2  //y
-      z=
-        3
-      x+
-        y+
-        z
-    }
-  g =
-    f +
-      4
-  g ->
-    h ->
-    p ->
-    q 
-  `,
-    "{:f = {:x = {1}; :y = {2}; :z = {3}; (::add (::add :x :y) :z)}; :g = {(::add :f 4)}; (::q (::p (::h :g)))}",
-  )
-  testParse(
-    `
-    a |>
-    b |>
-    c |>
-    d 
-  `,
-    "{(::d (::c (::b :a)))}",
-  )
-  testParse(
-    `
-    a |>
-    b |>
-    c |>
-    d +
-    e
-  `,
-    "{(::add (::d (::c (::b :a))) :e)}",
+  a |>
+  b |>
+  c |>
+  d +
+  e
+ `,
+    "{(::$_endOfOuterBlock_$ () (::add (::d (::c (::b :a))) :e))}",
   )
 })
diff --git a/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_Parse_type_test.res b/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_Parse_type_test.res
index 4f7dabdc..010486be 100644
--- a/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_Parse_type_test.res
+++ b/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_Parse_type_test.res
@@ -3,77 +3,83 @@ open Reducer_Peggy_TestHelpers
 
 describe("Peggy parse type", () => {
   describe("type of", () => {
-    testParse("p: number", "{(::$_typeOf_$ :p #number)}")
+    testParse("p: number", "{(::$_typeOf_$ :p #number); (::$_endOfOuterBlock_$ () ())}")
   })
   describe("type alias", () => {
-    testParse("type index=number", "{(::$_typeAlias_$ #index #number)}")
+    testParse(
+      "type index=number",
+      "{(::$_typeAlias_$ #index #number); (::$_endOfOuterBlock_$ () ())}",
+    )
   })
   describe("type or", () => {
     testParse(
       "answer: number|string",
-      "{(::$_typeOf_$ :answer (::$_typeOr_$ (::$_constructArray_$ (#number #string))))}",
+      "{(::$_typeOf_$ :answer (::$_typeOr_$ (::$_constructArray_$ (#number #string)))); (::$_endOfOuterBlock_$ () ())}",
     )
   })
   describe("type function", () => {
     testParse(
       "f: number=>number=>number",
-      "{(::$_typeOf_$ :f (::$_typeFunction_$ (::$_constructArray_$ (#number #number #number))))}",
+      "{(::$_typeOf_$ :f (::$_typeFunction_$ (::$_constructArray_$ (#number #number #number)))); (::$_endOfOuterBlock_$ () ())}",
     )
   })
   describe("high priority contract", () => {
     testParse(
       "answer: number<-min<-max(100)|string",
-      "{(::$_typeOf_$ :answer (::$_typeOr_$ (::$_constructArray_$ ((::$_typeModifier_max_$ (::$_typeModifier_min_$ #number) 100) #string))))}",
+      "{(::$_typeOf_$ :answer (::$_typeOr_$ (::$_constructArray_$ ((::$_typeModifier_max_$ (::$_typeModifier_min_$ #number) 100) #string)))); (::$_endOfOuterBlock_$ () ())}",
     )
     testParse(
       "answer: number<-memberOf([1,3,5])",
-      "{(::$_typeOf_$ :answer (::$_typeModifier_memberOf_$ #number (::$_constructArray_$ (1 3 5))))}",
+      "{(::$_typeOf_$ :answer (::$_typeModifier_memberOf_$ #number (::$_constructArray_$ (1 3 5)))); (::$_endOfOuterBlock_$ () ())}",
     )
   })
   describe("low priority contract", () => {
     testParse(
       "answer: number | string $ opaque",
-      "{(::$_typeOf_$ :answer (::$_typeModifier_opaque_$ (::$_typeOr_$ (::$_constructArray_$ (#number #string)))))}",
+      "{(::$_typeOf_$ :answer (::$_typeModifier_opaque_$ (::$_typeOr_$ (::$_constructArray_$ (#number #string))))); (::$_endOfOuterBlock_$ () ())}",
     )
   })
   describe("type array", () => {
-    testParse("answer: [number]", "{(::$_typeOf_$ :answer (::$_typeArray_$ #number))}")
+    testParse(
+      "answer: [number]",
+      "{(::$_typeOf_$ :answer (::$_typeArray_$ #number)); (::$_endOfOuterBlock_$ () ())}",
+    )
   })
   describe("type record", () => {
     testParse(
       "answer: {a: number, b: string}",
-      "{(::$_typeOf_$ :answer (::$_typeRecord_$ (::$_constructRecord_$ ('a': #number 'b': #string))))}",
+      "{(::$_typeOf_$ :answer (::$_typeRecord_$ (::$_constructRecord_$ ('a': #number 'b': #string)))); (::$_endOfOuterBlock_$ () ())}",
     )
   })
   describe("type constructor", () => {
     testParse(
       "answer: Age(number)",
-      "{(::$_typeOf_$ :answer (::$_typeConstructor_$ #Age (::$_constructArray_$ (#number))))}",
+      "{(::$_typeOf_$ :answer (::$_typeConstructor_$ #Age (::$_constructArray_$ (#number)))); (::$_endOfOuterBlock_$ () ())}",
     )
     testParse(
       "answer: Complex(number, number)",
-      "{(::$_typeOf_$ :answer (::$_typeConstructor_$ #Complex (::$_constructArray_$ (#number #number))))}",
+      "{(::$_typeOf_$ :answer (::$_typeConstructor_$ #Complex (::$_constructArray_$ (#number #number)))); (::$_endOfOuterBlock_$ () ())}",
     )
     testParse(
       "answer: Person({age: number, name: string})",
-      "{(::$_typeOf_$ :answer (::$_typeConstructor_$ #Person (::$_constructArray_$ ((::$_typeRecord_$ (::$_constructRecord_$ ('age': #number 'name': #string)))))))}",
+      "{(::$_typeOf_$ :answer (::$_typeConstructor_$ #Person (::$_constructArray_$ ((::$_typeRecord_$ (::$_constructRecord_$ ('age': #number 'name': #string))))))); (::$_endOfOuterBlock_$ () ())}",
     )
     testParse(
       "weekend: Saturday | Sunday",
-      "{(::$_typeOf_$ :weekend (::$_typeOr_$ (::$_constructArray_$ ((::$_typeConstructor_$ #Saturday (::$_constructArray_$ ())) (::$_typeConstructor_$ #Sunday (::$_constructArray_$ ()))))))}",
+      "{(::$_typeOf_$ :weekend (::$_typeOr_$ (::$_constructArray_$ ((::$_typeConstructor_$ #Saturday (::$_constructArray_$ ())) (::$_typeConstructor_$ #Sunday (::$_constructArray_$ ())))))); (::$_endOfOuterBlock_$ () ())}",
     )
   })
   describe("type parenthesis", () => {
     //$ is introduced to avoid parenthesis
     testParse(
       "answer: (number|string)<-opaque",
-      "{(::$_typeOf_$ :answer (::$_typeModifier_opaque_$ (::$_typeOr_$ (::$_constructArray_$ (#number #string)))))}",
+      "{(::$_typeOf_$ :answer (::$_typeModifier_opaque_$ (::$_typeOr_$ (::$_constructArray_$ (#number #string))))); (::$_endOfOuterBlock_$ () ())}",
     )
   })
   describe("squiggle expressions in type contracts", () => {
     testParse(
       "odds1 = [1,3,5]; odds2 = [7, 9]; type odds = number<-memberOf(concat(odds1, odds2))",
-      "{:odds1 = {(::$_constructArray_$ (1 3 5))}; :odds2 = {(::$_constructArray_$ (7 9))}; (::$_typeAlias_$ #odds (::$_typeModifier_memberOf_$ #number (::concat :odds1 :odds2)))}",
+      "{:odds1 = {(::$_constructArray_$ (1 3 5))}; :odds2 = {(::$_constructArray_$ (7 9))}; (::$_typeAlias_$ #odds (::$_typeModifier_memberOf_$ #number (::concat :odds1 :odds2))); (::$_endOfOuterBlock_$ () ())}",
     )
   })
 })
diff --git a/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_TestHelpers.res b/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_TestHelpers.res
index b434fdb9..303f66ee 100644
--- a/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_TestHelpers.res
+++ b/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_TestHelpers.res
@@ -23,13 +23,7 @@ let expectToExpressionToBe = (expr, answer, ~v="_", ()) => {
   } else {
     let a2 =
       rExpr
-      ->Result.flatMap(expr =>
-        Expression.reduceExpression(
-          expr,
-          ReducerInterface_StdLib.internalStdLib,
-          ExpressionValue.defaultEnvironment,
-        )
-      )
+      ->Result.flatMap(expr => Expression.BackCompatible.evaluate(expr))
       ->Reducer_Helpers.rRemoveDefaultsInternal
       ->ExpressionValue.toStringResultOkless
     (a1, a2)->expect->toEqual((answer, v))
diff --git a/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_ToExpression_outerBlock_test.res b/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_ToExpression_outerBlock_test.res
new file mode 100644
index 00000000..951005c2
--- /dev/null
+++ b/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_ToExpression_outerBlock_test.res
@@ -0,0 +1,23 @@
+module Bindings = Reducer_Bindings
+module InternalExpressionValue = ReducerInterface_InternalExpressionValue
+
+open Jest
+open Reducer_Peggy_TestHelpers
+
+describe("Peggy Outer Block", () => {
+  testToExpression("1", "{(:$_endOfOuterBlock_$ () 1)}", ~v="1", ())
+  testToExpression("x=1", "{(:$_let_$ :x {1}); (:$_endOfOuterBlock_$ () ())}", ~v="()", ())
+  testToExpression(
+    "x=1; y=2",
+    "{(:$_let_$ :x {1}); (:$_let_$ :y {2}); (:$_endOfOuterBlock_$ () ())}",
+    ~v="()",
+    (),
+  )
+  testToExpression("x=1; 2", "{(:$_let_$ :x {1}); (:$_endOfOuterBlock_$ () 2)}", ~v="2", ())
+  testToExpression(
+    "x={a=1; a}; x",
+    "{(:$_let_$ :x {(:$_let_$ :a {1}); :a}); (:$_endOfOuterBlock_$ () :x)}",
+    ~v="1",
+    (),
+  )
+})
diff --git a/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_ToExpression_test.res b/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_ToExpression_test.res
index b8a81f25..3b20fafc 100644
--- a/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_ToExpression_test.res
+++ b/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_ToExpression_test.res
@@ -7,101 +7,138 @@ open Reducer_Peggy_TestHelpers
 describe("Peggy to Expression", () => {
   describe("literals operators parenthesis", () => {
     // Note that there is always an outer block. Otherwise, external bindings are ignored at the first statement
-    testToExpression("1", "{1}", ~v="1", ())
-    testToExpression("'hello'", "{'hello'}", ~v="'hello'", ())
-    testToExpression("true", "{true}", ~v="true", ())
-    testToExpression("1+2", "{(:add 1 2)}", ~v="3", ())
-    testToExpression("add(1,2)", "{(:add 1 2)}", ~v="3", ())
-    testToExpression("(1)", "{1}", ())
-    testToExpression("(1+2)", "{(:add 1 2)}", ())
+    testToExpression("1", "{(:$_endOfOuterBlock_$ () 1)}", ~v="1", ())
+    testToExpression("'hello'", "{(:$_endOfOuterBlock_$ () 'hello')}", ~v="'hello'", ())
+    testToExpression("true", "{(:$_endOfOuterBlock_$ () true)}", ~v="true", ())
+    testToExpression("1+2", "{(:$_endOfOuterBlock_$ () (:add 1 2))}", ~v="3", ())
+    testToExpression("add(1,2)", "{(:$_endOfOuterBlock_$ () (:add 1 2))}", ~v="3", ())
+    testToExpression("(1)", "{(:$_endOfOuterBlock_$ () 1)}", ())
+    testToExpression("(1+2)", "{(:$_endOfOuterBlock_$ () (:add 1 2))}", ())
   })
 
   describe("unary", () => {
-    testToExpression("-1", "{(:unaryMinus 1)}", ~v="-1", ())
-    testToExpression("!true", "{(:not true)}", ~v="false", ())
-    testToExpression("1 + -1", "{(:add 1 (:unaryMinus 1))}", ~v="0", ())
-    testToExpression("-a[0]", "{(:unaryMinus (:$_atIndex_$ :a 0))}", ())
+    testToExpression("-1", "{(:$_endOfOuterBlock_$ () (:unaryMinus 1))}", ~v="-1", ())
+    testToExpression("!true", "{(:$_endOfOuterBlock_$ () (:not true))}", ~v="false", ())
+    testToExpression("1 + -1", "{(:$_endOfOuterBlock_$ () (:add 1 (:unaryMinus 1)))}", ~v="0", ())
+    testToExpression("-a[0]", "{(:$_endOfOuterBlock_$ () (:unaryMinus (:$_atIndex_$ :a 0)))}", ())
   })
 
   describe("multi-line", () => {
-    testToExpression("x=1; 2", "{(:$_let_$ :x {1}); 2}", ~v="2", ())
-    testToExpression("x=1; y=2", "{(:$_let_$ :x {1}); (:$_let_$ :y {2})}", ~v="@{x: 1,y: 2}", ())
+    testToExpression("x=1; 2", "{(:$_let_$ :x {1}); (:$_endOfOuterBlock_$ () 2)}", ~v="2", ())
+    testToExpression(
+      "x=1; y=2",
+      "{(:$_let_$ :x {1}); (:$_let_$ :y {2}); (:$_endOfOuterBlock_$ () ())}",
+      (),
+    )
   })
 
   describe("variables", () => {
-    testToExpression("x = 1", "{(:$_let_$ :x {1})}", ~v="@{x: 1}", ())
-    testToExpression("x", "{:x}", ~v=":x", ()) //TODO: value should return error
-    testToExpression("x = 1; x", "{(:$_let_$ :x {1}); :x}", ~v="1", ())
+    testToExpression("x = 1", "{(:$_let_$ :x {1}); (:$_endOfOuterBlock_$ () ())}", ())
+    testToExpression("x", "{(:$_endOfOuterBlock_$ () :x)}", ~v="Error(x is not defined)", ()) //TODO: value should return error
+    testToExpression("x = 1; x", "{(:$_let_$ :x {1}); (:$_endOfOuterBlock_$ () :x)}", ~v="1", ())
   })
 
   describe("functions", () => {
     testToExpression(
       "identity(x) = x",
-      "{(:$_let_$ :identity (:$$_lambda_$$ [x] {:x}))}",
-      ~v="@{identity: lambda(x=>internal code)}",
+      "{(:$_let_$ :identity (:$$_lambda_$$ [x] {:x})); (:$_endOfOuterBlock_$ () ())}",
       (),
     ) // Function definitions become lambda assignments
-    testToExpression("identity(x)", "{(:identity :x)}", ()) // Note value returns error properly
+    testToExpression("identity(x)", "{(:$_endOfOuterBlock_$ () (:identity :x))}", ()) // Note value returns error properly
     testToExpression(
       "f(x) = x> 2 ? 0 : 1; f(3)",
-      "{(:$_let_$ :f (:$$_lambda_$$ [x] {(:$$_ternary_$$ (:larger :x 2) 0 1)})); (:f 3)}",
+      "{(:$_let_$ :f (:$$_lambda_$$ [x] {(:$$_ternary_$$ (:larger :x 2) 0 1)})); (:$_endOfOuterBlock_$ () (:f 3))}",
       ~v="0",
       (),
     )
   })
 
   describe("arrays", () => {
-    testToExpression("[]", "{(:$_constructArray_$ ())}", ~v="[]", ())
-    testToExpression("[0, 1, 2]", "{(:$_constructArray_$ (0 1 2))}", ~v="[0,1,2]", ())
+    testToExpression("[]", "{(:$_endOfOuterBlock_$ () (:$_constructArray_$ ()))}", ~v="[]", ())
+    testToExpression(
+      "[0, 1, 2]",
+      "{(:$_endOfOuterBlock_$ () (:$_constructArray_$ (0 1 2)))}",
+      ~v="[0,1,2]",
+      (),
+    )
     testToExpression(
       "['hello', 'world']",
-      "{(:$_constructArray_$ ('hello' 'world'))}",
+      "{(:$_endOfOuterBlock_$ () (:$_constructArray_$ ('hello' 'world')))}",
       ~v="['hello','world']",
       (),
     )
-    testToExpression("([0,1,2])[1]", "{(:$_atIndex_$ (:$_constructArray_$ (0 1 2)) 1)}", ~v="1", ())
+    testToExpression(
+      "([0,1,2])[1]",
+      "{(:$_endOfOuterBlock_$ () (:$_atIndex_$ (:$_constructArray_$ (0 1 2)) 1))}",
+      ~v="1",
+      (),
+    )
   })
 
   describe("records", () => {
     testToExpression(
       "{a: 1, b: 2}",
-      "{(:$_constructRecord_$ (('a' 1) ('b' 2)))}",
+      "{(:$_endOfOuterBlock_$ () (:$_constructRecord_$ (('a' 1) ('b' 2))))}",
       ~v="{a: 1,b: 2}",
       (),
     )
     testToExpression(
       "{1+0: 1, 2+0: 2}",
-      "{(:$_constructRecord_$ (((:add 1 0) 1) ((:add 2 0) 2)))}",
+      "{(:$_endOfOuterBlock_$ () (:$_constructRecord_$ (((:add 1 0) 1) ((:add 2 0) 2))))}",
       (),
     ) // key can be any expression
-    testToExpression("record.property", "{(:$_atIndex_$ :record 'property')}", ())
+    testToExpression(
+      "record.property",
+      "{(:$_endOfOuterBlock_$ () (:$_atIndex_$ :record 'property'))}",
+      (),
+    )
     testToExpression(
       "record={property: 1}; record.property",
-      "{(:$_let_$ :record {(:$_constructRecord_$ (('property' 1)))}); (:$_atIndex_$ :record 'property')}",
+      "{(:$_let_$ :record {(:$_constructRecord_$ (('property' 1)))}); (:$_endOfOuterBlock_$ () (:$_atIndex_$ :record 'property'))}",
       ~v="1",
       (),
     )
   })
 
   describe("comments", () => {
-    testToExpression("1 # This is a line comment", "{1}", ~v="1", ())
-    testToExpression("1 // This is a line comment", "{1}", ~v="1", ())
-    testToExpression("1 /* This is a multi line comment */", "{1}", ~v="1", ())
-    testToExpression("/* This is a multi line comment */ 1", "{1}", ~v="1", ())
+    testToExpression("1 # This is a line comment", "{(:$_endOfOuterBlock_$ () 1)}", ~v="1", ())
+    testToExpression("1 // This is a line comment", "{(:$_endOfOuterBlock_$ () 1)}", ~v="1", ())
+    testToExpression(
+      "1 /* This is a multi line comment */",
+      "{(:$_endOfOuterBlock_$ () 1)}",
+      ~v="1",
+      (),
+    )
+    testToExpression(
+      "/* This is a multi line comment */ 1",
+      "{(:$_endOfOuterBlock_$ () 1)}",
+      ~v="1",
+      (),
+    )
   })
 
   describe("ternary operator", () => {
-    testToExpression("true ? 1 : 0", "{(:$$_ternary_$$ true 1 0)}", ~v="1", ())
-    testToExpression("false ? 1 : 0", "{(:$$_ternary_$$ false 1 0)}", ~v="0", ())
+    testToExpression(
+      "true ? 1 : 0",
+      "{(:$_endOfOuterBlock_$ () (:$$_ternary_$$ true 1 0))}",
+      ~v="1",
+      (),
+    )
+    testToExpression(
+      "false ? 1 : 0",
+      "{(:$_endOfOuterBlock_$ () (:$$_ternary_$$ false 1 0))}",
+      ~v="0",
+      (),
+    )
     testToExpression(
       "true ? 1 : false ? 2 : 0",
-      "{(:$$_ternary_$$ true 1 (:$$_ternary_$$ false 2 0))}",
+      "{(:$_endOfOuterBlock_$ () (:$$_ternary_$$ true 1 (:$$_ternary_$$ false 2 0)))}",
       ~v="1",
       (),
     ) // nested ternary
     testToExpression(
       "false ? 1 : false ? 2 : 0",
-      "{(:$$_ternary_$$ false 1 (:$$_ternary_$$ false 2 0))}",
+      "{(:$_endOfOuterBlock_$ () (:$$_ternary_$$ false 1 (:$$_ternary_$$ false 2 0)))}",
       ~v="0",
       (),
     ) // nested ternary
@@ -109,21 +146,21 @@ describe("Peggy to Expression", () => {
       testToExpression(
         // expression binding
         "f(a) = a > 5 ? 1 : 0; f(6)",
-        "{(:$_let_$ :f (:$$_lambda_$$ [a] {(:$$_ternary_$$ (:larger :a 5) 1 0)})); (:f 6)}",
+        "{(:$_let_$ :f (:$$_lambda_$$ [a] {(:$$_ternary_$$ (:larger :a 5) 1 0)})); (:$_endOfOuterBlock_$ () (:f 6))}",
         ~v="1",
         (),
       )
       testToExpression(
         // when true binding
         "f(a) = a > 5 ? a : 0; f(6)",
-        "{(:$_let_$ :f (:$$_lambda_$$ [a] {(:$$_ternary_$$ (:larger :a 5) :a 0)})); (:f 6)}",
+        "{(:$_let_$ :f (:$$_lambda_$$ [a] {(:$$_ternary_$$ (:larger :a 5) :a 0)})); (:$_endOfOuterBlock_$ () (:f 6))}",
         ~v="6",
         (),
       )
       testToExpression(
         // when false binding
         "f(a) = a < 5 ? 1 : a; f(6)",
-        "{(:$_let_$ :f (:$$_lambda_$$ [a] {(:$$_ternary_$$ (:smaller :a 5) 1 :a)})); (:f 6)}",
+        "{(:$_let_$ :f (:$$_lambda_$$ [a] {(:$$_ternary_$$ (:smaller :a 5) 1 :a)})); (:$_endOfOuterBlock_$ () (:f 6))}",
         ~v="6",
         (),
       )
@@ -131,23 +168,41 @@ describe("Peggy to Expression", () => {
   })
 
   describe("if then else", () => {
-    testToExpression("if true then 2 else 3", "{(:$$_ternary_$$ true {2} {3})}", ())
-    testToExpression("if true then {2} else {3}", "{(:$$_ternary_$$ true {2} {3})}", ())
+    testToExpression(
+      "if true then 2 else 3",
+      "{(:$_endOfOuterBlock_$ () (:$$_ternary_$$ true {2} {3}))}",
+      (),
+    )
+    testToExpression(
+      "if true then {2} else {3}",
+      "{(:$_endOfOuterBlock_$ () (:$$_ternary_$$ true {2} {3}))}",
+      (),
+    )
     testToExpression(
       "if false then {2} else if false then {4} else {5}",
-      "{(:$$_ternary_$$ false {2} (:$$_ternary_$$ false {4} {5}))}",
+      "{(:$_endOfOuterBlock_$ () (:$$_ternary_$$ false {2} (:$$_ternary_$$ false {4} {5})))}",
       (),
     ) //nested if
   })
 
   describe("pipe", () => {
-    testToExpression("1 -> add(2)", "{(:add 1 2)}", ~v="3", ())
-    testToExpression("-1 -> add(2)", "{(:add (:unaryMinus 1) 2)}", ~v="1", ()) // note that unary has higher priority naturally
-    testToExpression("1 -> add(2) * 3", "{(:multiply (:add 1 2) 3)}", ~v="9", ())
+    testToExpression("1 -> add(2)", "{(:$_endOfOuterBlock_$ () (:add 1 2))}", ~v="3", ())
+    testToExpression(
+      "-1 -> add(2)",
+      "{(:$_endOfOuterBlock_$ () (:add (:unaryMinus 1) 2))}",
+      ~v="1",
+      (),
+    ) // note that unary has higher priority naturally
+    testToExpression(
+      "1 -> add(2) * 3",
+      "{(:$_endOfOuterBlock_$ () (:multiply (:add 1 2) 3))}",
+      ~v="9",
+      (),
+    )
   })
 
   describe("elixir pipe", () => {
-    testToExpression("1 |> add(2)", "{(:add 1 2)}", ~v="3", ())
+    testToExpression("1 |> add(2)", "{(:$_endOfOuterBlock_$ () (:add 1 2))}", ~v="3", ())
   })
 
   // see testParse for priorities of to and credibleIntervalToDistribution
@@ -157,30 +212,31 @@ describe("Peggy to Expression", () => {
     // Like lambdas they have a local scope.
     testToExpression(
       "y=99; x={y=1; y}",
-      "{(:$_let_$ :y {99}); (:$_let_$ :x {(:$_let_$ :y {1}); :y})}",
-      ~v="@{x: 1,y: 99}",
+      "{(:$_let_$ :y {99}); (:$_let_$ :x {(:$_let_$ :y {1}); :y}); (:$_endOfOuterBlock_$ () ())}",
       (),
     )
   })
 
   describe("lambda", () => {
-    testToExpression("{|x| x}", "{(:$$_lambda_$$ [x] {:x})}", ~v="lambda(x=>internal code)", ())
+    testToExpression(
+      "{|x| x}",
+      "{(:$_endOfOuterBlock_$ () (:$$_lambda_$$ [x] {:x}))}",
+      ~v="lambda(x=>internal code)",
+      (),
+    )
     testToExpression(
       "f={|x| x}",
-      "{(:$_let_$ :f {(:$$_lambda_$$ [x] {:x})})}",
-      ~v="@{f: lambda(x=>internal code)}",
+      "{(:$_let_$ :f {(:$$_lambda_$$ [x] {:x})}); (:$_endOfOuterBlock_$ () ())}",
       (),
     )
     testToExpression(
       "f(x)=x",
-      "{(:$_let_$ :f (:$$_lambda_$$ [x] {:x}))}",
-      ~v="@{f: lambda(x=>internal code)}",
+      "{(:$_let_$ :f (:$$_lambda_$$ [x] {:x})); (:$_endOfOuterBlock_$ () ())}",
       (),
     ) // Function definitions are lambda assignments
     testToExpression(
       "f(x)=x ? 1 : 0",
-      "{(:$_let_$ :f (:$$_lambda_$$ [x] {(:$$_ternary_$$ :x 1 0)}))}",
-      ~v="@{f: lambda(x=>internal code)}",
+      "{(:$_let_$ :f (:$$_lambda_$$ [x] {(:$$_ternary_$$ :x 1 0)})); (:$_endOfOuterBlock_$ () ())}",
       (),
     )
   })
@@ -188,12 +244,12 @@ describe("Peggy to Expression", () => {
   describe("module", () => {
     // testToExpression("Math.pi", "{:Math.pi}", ~v="3.141592653589793", ())
     // Only.test("stdlibrary", () => {
-    //   ReducerInterface_StdLib.internalStdLib
-    //   ->IEvBindings
-    //   ->InternalExpressionValue.toString
-    //   ->expect
-    //   ->toBe("")
+    //  ReducerInterface_StdLib.internalStdLib
+    //  ->IEvBindings
+    //  ->InternalExpressionValue.toString
+    //  ->expect
+    //  ->toBe("")
     // })
-    testToExpression("Math.pi", "{:Math.pi}", ~v="3.141592653589793", ())
+    testToExpression("Math.pi", "{(:$_endOfOuterBlock_$ () :Math.pi)}", ~v="3.141592653589793", ())
   })
 })
diff --git a/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_ToExpression_type_test.res b/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_ToExpression_type_test.res
index 9849adb0..b0cfb676 100644
--- a/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_ToExpression_type_test.res
+++ b/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_ToExpression_type_test.res
@@ -5,92 +5,92 @@ describe("Peggy Types to Expression", () => {
   describe("type of", () => {
     testToExpression(
       "p: number",
-      "{(:$_typeOf_$ :p #number)}",
-      ~v="@{_typeReferences_: {p: #number}}",
+      "{(:$_typeOf_$ :p #number); (:$_endOfOuterBlock_$ () ())}",
+      // ~v="@{_typeReferences_: {p: #number}}",
       (),
     )
   })
   describe("type alias", () => {
     testToExpression(
       "type index=number",
-      "{(:$_typeAlias_$ #index #number)}",
-      ~v="@{_typeAliases_: {index: #number}}",
+      "{(:$_typeAlias_$ #index #number); (:$_endOfOuterBlock_$ () ())}",
+      // ~v="@{_typeAliases_: {index: #number}}",
       (),
     )
   })
   describe("type or", () => {
     testToExpression(
       "answer: number|string|distribution",
-      "{(:$_typeOf_$ :answer (:$_typeOr_$ (:$_constructArray_$ (#number #string #distribution))))}",
-      ~v="@{_typeReferences_: {answer: {typeOr: [#number,#string,#distribution],typeTag: 'typeOr'}}}",
+      "{(:$_typeOf_$ :answer (:$_typeOr_$ (:$_constructArray_$ (#number #string #distribution)))); (:$_endOfOuterBlock_$ () ())}",
+      // ~v="@{_typeReferences_: {answer: {typeOr: [#number,#string,#distribution],typeTag: 'typeOr'}}}",
       (),
     )
   })
   describe("type function", () => {
     testToExpression(
       "f: number=>number=>number",
-      "{(:$_typeOf_$ :f (:$_typeFunction_$ (:$_constructArray_$ (#number #number #number))))}",
-      ~v="@{_typeReferences_: {f: {inputs: [#number,#number],output: #number,typeTag: 'typeFunction'}}}",
+      "{(:$_typeOf_$ :f (:$_typeFunction_$ (:$_constructArray_$ (#number #number #number)))); (:$_endOfOuterBlock_$ () ())}",
+      // ~v="@{_typeReferences_: {f: {inputs: [#number,#number],output: #number,typeTag: 'typeFunction'}}}",
       (),
     )
     testToExpression(
       "f: number=>number",
-      "{(:$_typeOf_$ :f (:$_typeFunction_$ (:$_constructArray_$ (#number #number))))}",
-      ~v="@{_typeReferences_: {f: {inputs: [#number],output: #number,typeTag: 'typeFunction'}}}",
+      "{(:$_typeOf_$ :f (:$_typeFunction_$ (:$_constructArray_$ (#number #number)))); (:$_endOfOuterBlock_$ () ())}",
+      // ~v="@{_typeReferences_: {f: {inputs: [#number],output: #number,typeTag: 'typeFunction'}}}",
       (),
     )
   })
   describe("high priority contract", () => {
     testToExpression(
       "answer: number<-min(1)<-max(100)|string",
-      "{(:$_typeOf_$ :answer (:$_typeOr_$ (:$_constructArray_$ ((:$_typeModifier_max_$ (:$_typeModifier_min_$ #number 1) 100) #string))))}",
-      ~v="@{_typeReferences_: {answer: {typeOr: [{max: 100,min: 1,typeIdentifier: #number,typeTag: 'typeIdentifier'},#string],typeTag: 'typeOr'}}}",
+      "{(:$_typeOf_$ :answer (:$_typeOr_$ (:$_constructArray_$ ((:$_typeModifier_max_$ (:$_typeModifier_min_$ #number 1) 100) #string)))); (:$_endOfOuterBlock_$ () ())}",
+      // ~v="@{_typeReferences_: {answer: {typeOr: [{max: 100,min: 1,typeIdentifier: #number,typeTag: 'typeIdentifier'},#string],typeTag: 'typeOr'}}}",
       (),
     )
     testToExpression(
       "answer: number<-memberOf([1,3,5])",
-      "{(:$_typeOf_$ :answer (:$_typeModifier_memberOf_$ #number (:$_constructArray_$ (1 3 5))))}",
-      ~v="@{_typeReferences_: {answer: {memberOf: [1,3,5],typeIdentifier: #number,typeTag: 'typeIdentifier'}}}",
+      "{(:$_typeOf_$ :answer (:$_typeModifier_memberOf_$ #number (:$_constructArray_$ (1 3 5)))); (:$_endOfOuterBlock_$ () ())}",
+      // ~v="@{_typeReferences_: {answer: {memberOf: [1,3,5],typeIdentifier: #number,typeTag: 'typeIdentifier'}}}",
       (),
     )
     testToExpression(
       "answer: number<-min(1)",
-      "{(:$_typeOf_$ :answer (:$_typeModifier_min_$ #number 1))}",
-      ~v="@{_typeReferences_: {answer: {min: 1,typeIdentifier: #number,typeTag: 'typeIdentifier'}}}",
+      "{(:$_typeOf_$ :answer (:$_typeModifier_min_$ #number 1)); (:$_endOfOuterBlock_$ () ())}",
+      // ~v="@{_typeReferences_: {answer: {min: 1,typeIdentifier: #number,typeTag: 'typeIdentifier'}}}",
       (),
     )
     testToExpression(
       "answer: number<-max(10)",
-      "{(:$_typeOf_$ :answer (:$_typeModifier_max_$ #number 10))}",
-      ~v="@{_typeReferences_: {answer: {max: 10,typeIdentifier: #number,typeTag: 'typeIdentifier'}}}",
+      "{(:$_typeOf_$ :answer (:$_typeModifier_max_$ #number 10)); (:$_endOfOuterBlock_$ () ())}",
+      // ~v="@{_typeReferences_: {answer: {max: 10,typeIdentifier: #number,typeTag: 'typeIdentifier'}}}",
       (),
     )
     testToExpression(
       "answer: number<-min(1)<-max(10)",
-      "{(:$_typeOf_$ :answer (:$_typeModifier_max_$ (:$_typeModifier_min_$ #number 1) 10))}",
-      ~v="@{_typeReferences_: {answer: {max: 10,min: 1,typeIdentifier: #number,typeTag: 'typeIdentifier'}}}",
+      "{(:$_typeOf_$ :answer (:$_typeModifier_max_$ (:$_typeModifier_min_$ #number 1) 10)); (:$_endOfOuterBlock_$ () ())}",
+      // ~v="@{_typeReferences_: {answer: {max: 10,min: 1,typeIdentifier: #number,typeTag: 'typeIdentifier'}}}",
       (),
     )
     testToExpression(
       "answer: number<-max(10)<-min(1)",
-      "{(:$_typeOf_$ :answer (:$_typeModifier_min_$ (:$_typeModifier_max_$ #number 10) 1))}",
-      ~v="@{_typeReferences_: {answer: {max: 10,min: 1,typeIdentifier: #number,typeTag: 'typeIdentifier'}}}",
+      "{(:$_typeOf_$ :answer (:$_typeModifier_min_$ (:$_typeModifier_max_$ #number 10) 1)); (:$_endOfOuterBlock_$ () ())}",
+      // ~v="@{_typeReferences_: {answer: {max: 10,min: 1,typeIdentifier: #number,typeTag: 'typeIdentifier'}}}",
       (),
     )
   })
   describe("low priority contract", () => {
     testToExpression(
       "answer: number | string $ opaque",
-      "{(:$_typeOf_$ :answer (:$_typeModifier_opaque_$ (:$_typeOr_$ (:$_constructArray_$ (#number #string)))))}",
-      ~v="@{_typeReferences_: {answer: {opaque: true,typeOr: [#number,#string],typeTag: 'typeOr'}}}",
+      "{(:$_typeOf_$ :answer (:$_typeModifier_opaque_$ (:$_typeOr_$ (:$_constructArray_$ (#number #string))))); (:$_endOfOuterBlock_$ () ())}",
+      // ~v="@{_typeReferences_: {answer: {opaque: true,typeOr: [#number,#string],typeTag: 'typeOr'}}}",
       (),
     )
   })
   describe("squiggle expressions in type contracts", () => {
     testToExpression(
       "odds1 = [1,3,5]; odds2 = [7, 9]; type odds = number<-memberOf(concat(odds1, odds2))",
-      "{(:$_let_$ :odds1 {(:$_constructArray_$ (1 3 5))}); (:$_let_$ :odds2 {(:$_constructArray_$ (7 9))}); (:$_typeAlias_$ #odds (:$_typeModifier_memberOf_$ #number (:concat :odds1 :odds2)))}",
-      ~v="@{_typeAliases_: {odds: {memberOf: [1,3,5,7,9],typeIdentifier: #number,typeTag: 'typeIdentifier'}},odds1: [1,3,5],odds2: [7,9]}",
+      "{(:$_let_$ :odds1 {(:$_constructArray_$ (1 3 5))}); (:$_let_$ :odds2 {(:$_constructArray_$ (7 9))}); (:$_typeAlias_$ #odds (:$_typeModifier_memberOf_$ #number (:concat :odds1 :odds2))); (:$_endOfOuterBlock_$ () ())}",
+      // ~v="@{_typeAliases_: {odds: {memberOf: [1,3,5,7,9],typeIdentifier: #number,typeTag: 'typeIdentifier'}},odds1: [1,3,5],odds2: [7,9]}",
       (),
     )
   })
diff --git a/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_ToExpression_void_test.res b/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_ToExpression_void_test.res
index a106a188..f46d387f 100644
--- a/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_ToExpression_void_test.res
+++ b/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_ToExpression_void_test.res
@@ -3,18 +3,23 @@ open Reducer_Peggy_TestHelpers
 
 describe("Peggy void", () => {
   //literal
-  testToExpression("()", "{()}", ~v="()", ())
+  testToExpression("()", "{(:$_endOfOuterBlock_$ () ())}", ~v="()", ())
   testToExpression(
     "fn()=1",
-    "{(:$_let_$ :fn (:$$_lambda_$$ [_] {1}))}",
-    ~v="@{fn: lambda(_=>internal code)}",
+    "{(:$_let_$ :fn (:$$_lambda_$$ [_] {1})); (:$_endOfOuterBlock_$ () ())}",
+    // ~v="@{fn: lambda(_=>internal code)}",
+    (),
+  )
+  testToExpression(
+    "fn()=1; fn()",
+    "{(:$_let_$ :fn (:$$_lambda_$$ [_] {1})); (:$_endOfOuterBlock_$ () (:fn ()))}",
+    ~v="1",
     (),
   )
-  testToExpression("fn()=1; fn()", "{(:$_let_$ :fn (:$$_lambda_$$ [_] {1})); (:fn ())}", ~v="1", ())
   testToExpression(
     "fn(a)=(); call fn(1)",
-    "{(:$_let_$ :fn (:$$_lambda_$$ [a] {()})); (:$_let_$ :_ {(:fn 1)})}",
-    ~v="@{_: (),fn: lambda(a=>internal code)}",
+    "{(:$_let_$ :fn (:$$_lambda_$$ [a] {()})); (:$_let_$ :_ {(:fn 1)}); (:$_endOfOuterBlock_$ () ())}",
+    // ~v="@{_: (),fn: lambda(a=>internal code)}",
     (),
   )
 })
diff --git a/packages/squiggle-lang/__tests__/Reducer/Reducer_TestHelpers.res b/packages/squiggle-lang/__tests__/Reducer/Reducer_TestHelpers.res
index 736c9c2f..34a21573 100644
--- a/packages/squiggle-lang/__tests__/Reducer/Reducer_TestHelpers.res
+++ b/packages/squiggle-lang/__tests__/Reducer/Reducer_TestHelpers.res
@@ -1,6 +1,7 @@
-module ExpressionT = Reducer_Expression_T
-module ExternalExpressionValue = ReducerInterface.ExternalExpressionValue
 module ErrorValue = Reducer_ErrorValue
+module Expression = Reducer_Expression
+module ExpressionT = Reducer_Expression_T
+module InternalExpressionValue = ReducerInterface.InternalExpressionValue
 
 open Jest
 open Expect
@@ -8,30 +9,26 @@ open Expect
 let unwrapRecord = rValue =>
   rValue->Belt.Result.flatMap(value =>
     switch value {
-    | ExternalExpressionValue.EvRecord(aRecord) => Ok(aRecord)
-    | _ => ErrorValue.RETodo("TODO: External bindings must be returned")->Error
+    | InternalExpressionValue.IEvRecord(aRecord) => Ok(aRecord)
+    | _ => ErrorValue.RETodo("TODO: Internal bindings must be returned")->Error
     }
   )
 
-let expectParseToBe = (expr: string, answer: string) =>
-  Reducer.parse(expr)->ExpressionT.toStringResult->expect->toBe(answer)
+let expectParseToBe = (code: string, answer: string) =>
+  Expression.BackCompatible.parse(code)->ExpressionT.toStringResult->expect->toBe(answer)
 
-let expectEvalToBe = (expr: string, answer: string) =>
-  Reducer.evaluate(expr)
-  ->Reducer_Helpers.rRemoveDefaultsExternal
-  ->ExternalExpressionValue.toStringResult
+let expectEvalToBe = (code: string, answer: string) =>
+  Expression.BackCompatible.evaluateString(code)
+  ->Reducer_Helpers.rRemoveDefaultsInternal
+  ->InternalExpressionValue.toStringResult
   ->expect
   ->toBe(answer)
 
-let expectEvalError = (expr: string) =>
-  Reducer.evaluate(expr)->ExternalExpressionValue.toStringResult->expect->toMatch("Error\(")
-
-let expectEvalBindingsToBe = (expr: string, bindings: Reducer.externalBindings, answer: string) =>
-  Reducer.evaluateUsingOptions(expr, ~externalBindings=Some(bindings), ~environment=None)
-  ->Reducer_Helpers.rRemoveDefaultsExternal
-  ->ExternalExpressionValue.toStringResult
+let expectEvalError = (code: string) =>
+  Expression.BackCompatible.evaluateString(code)
+  ->InternalExpressionValue.toStringResult
   ->expect
-  ->toBe(answer)
+  ->toMatch("Error\(")
 
 let testParseToBe = (expr, answer) => test(expr, () => expectParseToBe(expr, answer))
 let testDescriptionParseToBe = (desc, expr, answer) =>
@@ -40,18 +37,12 @@ let testDescriptionParseToBe = (desc, expr, answer) =>
 let testEvalError = expr => test(expr, () => expectEvalError(expr))
 let testEvalToBe = (expr, answer) => test(expr, () => expectEvalToBe(expr, answer))
 let testDescriptionEvalToBe = (desc, expr, answer) => test(desc, () => expectEvalToBe(expr, answer))
-let testEvalBindingsToBe = (expr, bindingsList, answer) =>
-  test(expr, () => expectEvalBindingsToBe(expr, bindingsList->Js.Dict.fromList, answer))
 
 module MySkip = {
   let testParseToBe = (expr, answer) => Skip.test(expr, () => expectParseToBe(expr, answer))
   let testEvalToBe = (expr, answer) => Skip.test(expr, () => expectEvalToBe(expr, answer))
-  let testEvalBindingsToBe = (expr, bindingsList, answer) =>
-    Skip.test(expr, () => expectEvalBindingsToBe(expr, bindingsList->Js.Dict.fromList, answer))
 }
 module MyOnly = {
   let testParseToBe = (expr, answer) => Only.test(expr, () => expectParseToBe(expr, answer))
   let testEvalToBe = (expr, answer) => Only.test(expr, () => expectEvalToBe(expr, answer))
-  let testEvalBindingsToBe = (expr, bindingsList, answer) =>
-    Only.test(expr, () => expectEvalBindingsToBe(expr, bindingsList->Js.Dict.fromList, answer))
 }
diff --git a/packages/squiggle-lang/__tests__/Reducer/Reducer_TestMacroHelpers.res b/packages/squiggle-lang/__tests__/Reducer/Reducer_TestMacroHelpers.res
index ffd5d964..752cc9c7 100644
--- a/packages/squiggle-lang/__tests__/Reducer/Reducer_TestMacroHelpers.res
+++ b/packages/squiggle-lang/__tests__/Reducer/Reducer_TestMacroHelpers.res
@@ -1,14 +1,14 @@
 open Jest
 open Expect
 
+module Bindings = Reducer_Bindings
 module BindingsReplacer = Reducer_Expression_BindingsReplacer
 module Expression = Reducer_Expression
-// module ExpressionValue = ReducerInterface.ExpressionValue
-module InternalExpressionValue = ReducerInterface.InternalExpressionValue
 module ExpressionWithContext = Reducer_ExpressionWithContext
+module InternalExpressionValue = ReducerInterface.InternalExpressionValue
 module Macro = Reducer_Expression_Macro
+module ProjectAccessorsT = ReducerProject_ProjectAccessors_T
 module T = Reducer_Expression_T
-module Bindings = Reducer_Bindings
 
 let testMacro_ = (
   tester,
@@ -21,8 +21,8 @@ let testMacro_ = (
     expr
     ->Macro.expandMacroCall(
       bindings,
-      InternalExpressionValue.defaultEnvironment,
-      Expression.reduceExpression,
+      ProjectAccessorsT.identityAccessors,
+      Expression.reduceExpressionInProject,
     )
     ->ExpressionWithContext.toStringResult
     ->expect
@@ -41,8 +41,8 @@ let testMacroEval_ = (
     expr
     ->Macro.doMacroCall(
       bindings,
-      InternalExpressionValue.defaultEnvironment,
-      Expression.reduceExpression,
+      ProjectAccessorsT.identityAccessors,
+      Expression.reduceExpressionInProject,
     )
     ->InternalExpressionValue.toStringResult
     ->expect
diff --git a/packages/squiggle-lang/__tests__/Reducer/Reducer_Type/Reducer_Type_Compile_test.res b/packages/squiggle-lang/__tests__/Reducer/Reducer_Type/Reducer_Type_Compile_test.res
index 71f90373..55ed36bd 100644
--- a/packages/squiggle-lang/__tests__/Reducer/Reducer_Type/Reducer_Type_Compile_test.res
+++ b/packages/squiggle-lang/__tests__/Reducer/Reducer_Type/Reducer_Type_Compile_test.res
@@ -8,7 +8,7 @@ open Jest
 open Expect
 
 let myIevEval = (aTypeSourceCode: string) =>
-  TypeCompile.ievFromTypeExpression(aTypeSourceCode, Expression.reduceExpression)
+  TypeCompile.ievFromTypeExpression(aTypeSourceCode, Expression.reduceExpressionInProject)
 let myIevEvalToString = (aTypeSourceCode: string) =>
   myIevEval(aTypeSourceCode)->InternalExpressionValue.toStringResult
 
@@ -19,7 +19,7 @@ let myIevTest = (test, aTypeSourceCode, answer) =>
   test(aTypeSourceCode, () => myIevExpectEqual(aTypeSourceCode, answer))
 
 let myTypeEval = (aTypeSourceCode: string) =>
-  TypeCompile.fromTypeExpression(aTypeSourceCode, Expression.reduceExpression)
+  TypeCompile.fromTypeExpression(aTypeSourceCode, Expression.reduceExpressionInProject)
 let myTypeEvalToString = (aTypeSourceCode: string) => myTypeEval(aTypeSourceCode)->T.toStringResult
 
 let myTypeExpectEqual = (aTypeSourceCode, answer) =>
diff --git a/packages/squiggle-lang/__tests__/Reducer/Reducer_Type/Reducer_Type_TypeChecker_arguments_test.res b/packages/squiggle-lang/__tests__/Reducer/Reducer_Type/Reducer_Type_TypeChecker_arguments_test.res
index 07da15bb..29fa8249 100644
--- a/packages/squiggle-lang/__tests__/Reducer/Reducer_Type/Reducer_Type_TypeChecker_arguments_test.res
+++ b/packages/squiggle-lang/__tests__/Reducer/Reducer_Type/Reducer_Type_TypeChecker_arguments_test.res
@@ -1,8 +1,9 @@
+module Bindings = Reducer_Bindings
+module ErrorValue = Reducer_ErrorValue
 module Expression = Reducer_Expression
 module ExpressionT = Reducer_Expression_T
-module ErrorValue = Reducer_ErrorValue
 module InternalExpressionValue = ReducerInterface_InternalExpressionValue
-module Bindings = Reducer_Bindings
+module ProjectAccessorsT = ReducerProject_ProjectAccessors_T
 module T = Reducer_Type_T
 module TypeChecker = Reducer_Type_TypeChecker
 
@@ -13,10 +14,10 @@ let checkArgumentsSourceCode = (aTypeSourceCode: string, sourceCode: string): re
   'v,
   ErrorValue.t,
 > => {
-  let reducerFn = Expression.reduceExpression
+  let reducerFn = Expression.reduceExpressionInProject
   let rResult =
-    Reducer.parse(sourceCode)->Belt.Result.flatMap(expr =>
-      reducerFn(expr, Bindings.emptyBindings, InternalExpressionValue.defaultEnvironment)
+    Expression.BackCompatible.parse(sourceCode)->Belt.Result.flatMap(expr =>
+      reducerFn(expr, Bindings.emptyBindings, ProjectAccessorsT.identityAccessors)
     )
   rResult->Belt.Result.flatMap(result =>
     switch result {
diff --git a/packages/squiggle-lang/__tests__/Reducer/Reducer_Type/Reducer_Type_TypeChecker_test.res b/packages/squiggle-lang/__tests__/Reducer/Reducer_Type/Reducer_Type_TypeChecker_test.res
index a3ee2712..fccff738 100644
--- a/packages/squiggle-lang/__tests__/Reducer/Reducer_Type/Reducer_Type_TypeChecker_test.res
+++ b/packages/squiggle-lang/__tests__/Reducer/Reducer_Type/Reducer_Type_TypeChecker_test.res
@@ -5,6 +5,7 @@ module InternalExpressionValue = ReducerInterface_InternalExpressionValue
 module Bindings = Reducer_Bindings
 module T = Reducer_Type_T
 module TypeChecker = Reducer_Type_TypeChecker
+module ProjectAccessorsT = ReducerProject_ProjectAccessors_T
 
 open Jest
 open Expect
@@ -16,10 +17,10 @@ let isTypeOfSourceCode = (aTypeSourceCode: string, sourceCode: string): result<
   'v,
   ErrorValue.t,
 > => {
-  let reducerFn = Expression.reduceExpression
+  let reducerFn = Expression.reduceExpressionInProject
   let rResult =
-    Reducer.parse(sourceCode)->Belt.Result.flatMap(expr =>
-      reducerFn(expr, Bindings.emptyBindings, InternalExpressionValue.defaultEnvironment)
+    Expression.BackCompatible.parse(sourceCode)->Belt.Result.flatMap(expr =>
+      reducerFn(expr, Bindings.emptyBindings, ProjectAccessorsT.identityAccessors)
     )
   rResult->Belt.Result.flatMap(result => TypeChecker.isTypeOf(aTypeSourceCode, result, reducerFn))
 }
diff --git a/packages/squiggle-lang/__tests__/Reducer/Reducer_Type/Reducer_Type_switch_replacement_test.res b/packages/squiggle-lang/__tests__/Reducer/Reducer_Type/Reducer_Type_switch_replacement_test.res
index 16f0f118..9dbe08c5 100644
--- a/packages/squiggle-lang/__tests__/Reducer/Reducer_Type/Reducer_Type_switch_replacement_test.res
+++ b/packages/squiggle-lang/__tests__/Reducer/Reducer_Type/Reducer_Type_switch_replacement_test.res
@@ -4,8 +4,11 @@ open Expect
 module DispatchT = Reducer_Dispatch_T
 module Expression = Reducer_Expression
 module ExpressionT = Reducer_Expression_T
-module TypeCompile = Reducer_Type_Compile
+module ProjectAccessorsT = ReducerProject_ProjectAccessors_T
+module ProjectReducerFnT = ReducerProject_ReducerFn_T
 module TypeChecker = Reducer_Type_TypeChecker
+module TypeCompile = Reducer_Type_Compile
+
 open ReducerInterface_InternalExpressionValue
 
 type errorValue = Reducer_ErrorValue.errorValue
@@ -14,13 +17,14 @@ type errorValue = Reducer_ErrorValue.errorValue
 // In dispatchChainPiece, we execute an return the result of execution if there is a type match.
 // Otherwise we return None so that the call chain can continue.
 // So we want to build a function like
-// dispatchChainPiece = (call: functionCall, environment): option<result<internalExpressionValue, errorValue>>
+// dispatchChainPiece = (call: functionCall, accessors): option<result<internalExpressionValue, errorValue>>
+// Use accessors.environment to get the environment finally.
 
 // Now lets make the dispatchChainPiece itself.
 // Note that I am not passing the reducer to the dispatchChainPiece as an argument because it is in the context anyway.
 // Keep in mind that reducerFn is necessary for map/reduce so dispatchChainPiece should have a reducerFn in context.
 
-let makeMyDispatchChainPiece = (reducer: ExpressionT.reducerFn): DispatchT.dispatchChainPiece => {
+let makeMyDispatchChainPiece = (reducer: ProjectReducerFnT.t): DispatchT.dispatchChainPiece => {
   // Let's have a pure implementations
   module Implementation = {
     let stringConcat = (a: string, b: string): string => Js.String2.concat(a, b)
@@ -45,15 +49,15 @@ let makeMyDispatchChainPiece = (reducer: ExpressionT.reducerFn): DispatchT.dispa
 
   // Let's bridge the pure implementation to expression values
   module Bridge = {
-    let stringConcat: DispatchT.genericIEvFunction = (args, _environment) => {
+    let stringConcat: DispatchT.genericIEvFunction = (args, _accessors: ProjectAccessorsT.t) => {
       let (a, b) = extractStringString(args)
       Implementation.stringConcat(a, b)->IEvString->Ok
     }
-    let arrayConcat: DispatchT.genericIEvFunction = (args, _environment) => {
+    let arrayConcat: DispatchT.genericIEvFunction = (args, _accessors: ProjectAccessorsT.t) => {
       let (a, b) = extractArrayArray(args)
       Implementation.arrayConcat(a, b)->IEvArray->Ok
     }
-    let plot: DispatchT.genericIEvFunction = (args, _environment) => {
+    let plot: DispatchT.genericIEvFunction = (args, _accessors: ProjectAccessorsT.t) => {
       switch args {
       // Just assume that we are doing the business of extracting and converting the deep record
       | [IEvRecord(_)] => Implementation.plot({"title": "This is a plot"})->IEvString->Ok
@@ -98,12 +102,12 @@ let makeMyDispatchChainPiece = (reducer: ExpressionT.reducerFn): DispatchT.dispa
 // Exactly the same as the one used in real life
 let _dispatch = (
   call: functionCall,
-  environment,
-  reducer: Reducer_Expression_T.reducerFn,
+  accessors: ProjectAccessorsT.t,
+  reducer: ProjectReducerFnT.t,
   chain,
 ): result<internalExpressionValue, 'e> => {
   let dispatchChainPiece = makeMyDispatchChainPiece(reducer)
-  dispatchChainPiece(call, environment)->E.O2.defaultFn(() => chain(call, environment, reducer))
+  dispatchChainPiece(call, accessors)->E.O2.defaultFn(() => chain(call, accessors, reducer))
 }
 
 // What is important about this implementation?
@@ -112,12 +116,12 @@ let _dispatch = (
 // B) Complicated recursive record types are not a problem.
 
 describe("Type Dispatch", () => {
-  let reducerFn = Expression.reduceExpression
+  let reducerFn = Expression.reduceExpressionInProject
   let dispatchChainPiece = makeMyDispatchChainPiece(reducerFn)
   test("stringConcat", () => {
     let call: functionCall = ("concat", [IEvString("hello"), IEvString("world")])
 
-    let result = dispatchChainPiece(call, defaultEnvironment)
+    let result = dispatchChainPiece(call, ProjectAccessorsT.identityAccessors)
     expect(result)->toEqual(Some(Ok(IEvString("helloworld"))))
   })
 })
diff --git a/packages/squiggle-lang/__tests__/Reducer/Reducer_externalBindings_test.res b/packages/squiggle-lang/__tests__/Reducer/Reducer_externalBindings_test.res
deleted file mode 100644
index bb1a4d35..00000000
--- a/packages/squiggle-lang/__tests__/Reducer/Reducer_externalBindings_test.res
+++ /dev/null
@@ -1,14 +0,0 @@
-open Jest
-open Reducer_TestHelpers
-
-describe("Eval with Bindings", () => {
-  testEvalBindingsToBe("x", list{("x", ExternalExpressionValue.EvNumber(1.))}, "Ok(1)")
-  testEvalBindingsToBe("x+1", list{("x", ExternalExpressionValue.EvNumber(1.))}, "Ok(2)")
-  testParseToBe("y = x+1; y", "Ok({(:$_let_$ :y {(:add :x 1)}); :y})")
-  testEvalBindingsToBe("y = x+1; y", list{("x", ExternalExpressionValue.EvNumber(1.))}, "Ok(2)")
-  testEvalBindingsToBe(
-    "y = x+1",
-    list{("x", ExternalExpressionValue.EvNumber(1.))},
-    "Ok(@{x: 1,y: 2})",
-  )
-})
diff --git a/packages/squiggle-lang/__tests__/Reducer/Reducer_functionAssignment_test.res b/packages/squiggle-lang/__tests__/Reducer/Reducer_functionAssignment_test.res
index 30725cfe..a2abb85d 100644
--- a/packages/squiggle-lang/__tests__/Reducer/Reducer_functionAssignment_test.res
+++ b/packages/squiggle-lang/__tests__/Reducer/Reducer_functionAssignment_test.res
@@ -2,8 +2,14 @@ open Jest
 open Reducer_TestHelpers
 
 describe("Parse function assignment", () => {
-  testParseToBe("f(x)=x", "Ok({(:$_let_$ :f (:$$_lambda_$$ [x] {:x}))})")
-  testParseToBe("f(x)=2*x", "Ok({(:$_let_$ :f (:$$_lambda_$$ [x] {(:multiply 2 :x)}))})")
+  testParseToBe(
+    "f(x)=x",
+    "Ok({(:$_let_$ :f (:$$_lambda_$$ [x] {:x})); (:$_endOfOuterBlock_$ () ())})",
+  )
+  testParseToBe(
+    "f(x)=2*x",
+    "Ok({(:$_let_$ :f (:$$_lambda_$$ [x] {(:multiply 2 :x)})); (:$_endOfOuterBlock_$ () ())})",
+  )
   //MathJs does not allow blocks in function definitions
 })
 
diff --git a/packages/squiggle-lang/__tests__/Reducer/Reducer_functionTricks_test.res b/packages/squiggle-lang/__tests__/Reducer/Reducer_functionTricks_test.res
index 68614f89..9b111354 100644
--- a/packages/squiggle-lang/__tests__/Reducer/Reducer_functionTricks_test.res
+++ b/packages/squiggle-lang/__tests__/Reducer/Reducer_functionTricks_test.res
@@ -39,33 +39,27 @@ describe("symbol not defined", () => {
 })
 
 describe("call and bindings", () => {
-  testEvalToBe("f(x)=x+1", "Ok(@{f: lambda(x=>internal code)})")
+  testEvalToBe("f(x)=x+1; f(0)", "Ok(1)")
   testEvalToBe("f(x)=x+1; f(1)", "Ok(2)")
-  testEvalToBe("f=1;y=2", "Ok(@{f: 1,y: 2})")
-  testEvalToBe("f(x)=x+1; y=f(1)", "Ok(@{f: lambda(x=>internal code),y: 2})")
+  testEvalToBe("f=1;y=2", "Ok(())")
+  testEvalToBe("f(x)=x+1; y=f(1); y", "Ok(2)")
   testEvalToBe("f(x)=x+1; y=f(1); f(1)", "Ok(2)")
-  testEvalToBe("f(x)=x+1; y=f(1); z=f(1)", "Ok(@{f: lambda(x=>internal code),y: 2,z: 2})")
-  testEvalToBe(
-    "f(x)=x+1; g(x)=f(x)+1",
-    "Ok(@{f: lambda(x=>internal code),g: lambda(x=>internal code)})",
-  )
+  testEvalToBe("f(x)=x+1; y=f(1); z=f(1); z", "Ok(2)")
+  testEvalToBe("f(x)=x+1; g(x)=f(x)+1; g(0)", "Ok(2)")
   testParseToBe(
     "f=99; g(x)=f; g(2)",
-    "Ok({(:$_let_$ :f {99}); (:$_let_$ :g (:$$_lambda_$$ [x] {:f})); (:g 2)})",
+    "Ok({(:$_let_$ :f {99}); (:$_let_$ :g (:$$_lambda_$$ [x] {:f})); (:$_endOfOuterBlock_$ () (:g 2))})",
   )
   testEvalToBe("f=99; g(x)=f; g(2)", "Ok(99)")
   testEvalToBe("f(x)=x; g(x)=f(x); g(2)", "Ok(2)")
-  testEvalToBe(
-    "f(x)=x+1; g(x)=f(x)+1; y=g(2)",
-    "Ok(@{f: lambda(x=>internal code),g: lambda(x=>internal code),y: 4})",
-  )
+  testEvalToBe("f(x)=x+1; g(x)=f(x)+1; y=g(2); y", "Ok(4)")
   testEvalToBe("f(x)=x+1; g(x)=f(x)+1; g(2)", "Ok(4)")
 })
 
 describe("function tricks", () => {
   testEvalError("f(x)=f(y)=2; f(2)") //Error because chain assignment is not allowed
   testEvalToBe("y=2;g(x)=y+1;g(2)", "Ok(3)")
-  testEvalToBe("y=2;g(x)=inspect(y)+1", "Ok(@{g: lambda(x=>internal code),y: 2})")
+  testEvalToBe("y=2;g(x)=inspect(y)+1;y", "Ok(2)")
   MySkip.testEvalToBe("f(x) = x(x); f(f)", "????") // TODO: Infinite loop. Any solution? Catching proper exception or timeout?
   MySkip.testEvalToBe("f(x, x)=x+x; f(1,2)", "????") // TODO: Duplicate parameters
   testEvalToBe("myadd(x,y)=x+y; z=myadd; z", "Ok(lambda(x,y=>internal code))")
@@ -73,10 +67,7 @@ describe("function tricks", () => {
 })
 
 describe("lambda in structures", () => {
-  testEvalToBe(
-    "myadd(x,y)=x+y; z=[myadd]",
-    "Ok(@{myadd: lambda(x,y=>internal code),z: [lambda(x,y=>internal code)]})",
-  )
+  testEvalToBe("myadd(x,y)=x+y; z=[myadd]", "Ok(())")
   testEvalToBe("myadd(x,y)=x+y; z=[myadd]; z[0]", "Ok(lambda(x,y=>internal code))")
   testEvalToBe("myadd(x,y)=x+y; z=[myadd]; z[0](3,2)", "Ok(5)")
   testEvalToBe("myaddd(x,y)=x+y; z={x: myaddd}; z", "Ok({x: lambda(x,y=>internal code)})")
diff --git a/packages/squiggle-lang/__tests__/Reducer/Reducer_ternaryOperator_test.res b/packages/squiggle-lang/__tests__/Reducer/Reducer_ternaryOperator_test.res
index 22fa8328..c86f4bca 100644
--- a/packages/squiggle-lang/__tests__/Reducer/Reducer_ternaryOperator_test.res
+++ b/packages/squiggle-lang/__tests__/Reducer/Reducer_ternaryOperator_test.res
@@ -2,7 +2,10 @@ open Jest
 open Reducer_TestHelpers
 
 describe("Parse ternary operator", () => {
-  testParseToBe("true ? 'YES' : 'NO'", "Ok({(:$$_ternary_$$ true 'YES' 'NO')})")
+  testParseToBe(
+    "true ? 'YES' : 'NO'",
+    "Ok({(:$_endOfOuterBlock_$ () (:$$_ternary_$$ true 'YES' 'NO'))})",
+  )
 })
 
 describe("Evaluate ternary operator", () => {
diff --git a/packages/squiggle-lang/__tests__/Reducer/Reducer_test.res b/packages/squiggle-lang/__tests__/Reducer/Reducer_test.res
index dc403e7d..f70aa934 100644
--- a/packages/squiggle-lang/__tests__/Reducer/Reducer_test.res
+++ b/packages/squiggle-lang/__tests__/Reducer/Reducer_test.res
@@ -48,7 +48,7 @@ describe("eval", () => {
     testEvalToBe("x=1; y=x+1; y+1", "Ok(3)")
     testEvalError("1; x=1")
     testEvalError("1; 1")
-    testEvalToBe("x=1; x=1", "Ok(@{x: 1})")
+    testEvalToBe("x=1; x=1; x", "Ok(1)")
   })
 })
 
diff --git a/packages/squiggle-lang/__tests__/ReducerInterface/ReducerInterface_Distribution_test.res b/packages/squiggle-lang/__tests__/ReducerInterface/ReducerInterface_Distribution_test.res
index 3083b71b..4adb363f 100644
--- a/packages/squiggle-lang/__tests__/ReducerInterface/ReducerInterface_Distribution_test.res
+++ b/packages/squiggle-lang/__tests__/ReducerInterface/ReducerInterface_Distribution_test.res
@@ -118,28 +118,40 @@ describe("eval on distribution functions", () => {
 
 describe("parse on distribution functions", () => {
   describe("power", () => {
-    testParse("normal(5,2) ^ normal(5,1)", "Ok({(:pow (:normal 5 2) (:normal 5 1))})")
-    testParse("3 ^ normal(5,1)", "Ok({(:pow 3 (:normal 5 1))})")
-    testParse("normal(5,2) ^ 3", "Ok({(:pow (:normal 5 2) 3)})")
+    testParse(
+      "normal(5,2) ^ normal(5,1)",
+      "Ok({(:$_endOfOuterBlock_$ () (:pow (:normal 5 2) (:normal 5 1)))})",
+    )
+    testParse("3 ^ normal(5,1)", "Ok({(:$_endOfOuterBlock_$ () (:pow 3 (:normal 5 1)))})")
+    testParse("normal(5,2) ^ 3", "Ok({(:$_endOfOuterBlock_$ () (:pow (:normal 5 2) 3))})")
   })
   describe("subtraction", () => {
-    testParse("10 - normal(5,1)", "Ok({(:subtract 10 (:normal 5 1))})")
-    testParse("normal(5,1) - 10", "Ok({(:subtract (:normal 5 1) 10)})")
+    testParse("10 - normal(5,1)", "Ok({(:$_endOfOuterBlock_$ () (:subtract 10 (:normal 5 1)))})")
+    testParse("normal(5,1) - 10", "Ok({(:$_endOfOuterBlock_$ () (:subtract (:normal 5 1) 10))})")
   })
   describe("pointwise arithmetic expressions", () => {
     testParse(~skip=true, "normal(5,2) .+ normal(5,1)", "Ok((:dotAdd (:normal 5 2) (:normal 5 1)))")
     testParse(
       ~skip=true,
       "normal(5,2) .- normal(5,1)",
-      "Ok((:$$_block_$$ (:dotSubtract (:normal 5 2) (:normal 5 1))))",
+      "Ok((:$_endOfOuterBlock_$ () (:$$_block_$$ (:dotSubtract (:normal 5 2) (:normal 5 1)))))",
       // TODO: !!! returns "Ok({(:dotPow (:normal 5 2) (:normal 5 1))})"
     )
-    testParse("normal(5,2) .* normal(5,1)", "Ok({(:dotMultiply (:normal 5 2) (:normal 5 1))})")
-    testParse("normal(5,2) ./ normal(5,1)", "Ok({(:dotDivide (:normal 5 2) (:normal 5 1))})")
-    testParse("normal(5,2) .^ normal(5,1)", "Ok({(:dotPow (:normal 5 2) (:normal 5 1))})")
+    testParse(
+      "normal(5,2) .* normal(5,1)",
+      "Ok({(:$_endOfOuterBlock_$ () (:dotMultiply (:normal 5 2) (:normal 5 1)))})",
+    )
+    testParse(
+      "normal(5,2) ./ normal(5,1)",
+      "Ok({(:$_endOfOuterBlock_$ () (:dotDivide (:normal 5 2) (:normal 5 1)))})",
+    )
+    testParse(
+      "normal(5,2) .^ normal(5,1)",
+      "Ok({(:$_endOfOuterBlock_$ () (:dotPow (:normal 5 2) (:normal 5 1)))})",
+    )
   })
   describe("equality", () => {
-    testParse("5 == normal(5,2)", "Ok({(:equal 5 (:normal 5 2))})")
+    testParse("5 == normal(5,2)", "Ok({(:$_endOfOuterBlock_$ () (:equal 5 (:normal 5 2)))})")
   })
   describe("pointwise adding two normals", () => {
     testParse(~skip=true, "normal(5,2) .+ normal(5,1)", "Ok((:dotAdd (:normal 5 2) (:normal 5 1)))")
diff --git a/packages/squiggle-lang/__tests__/ReducerInterface/ReducerInterface_ExpressionValue_test.res b/packages/squiggle-lang/__tests__/ReducerInterface/ReducerInterface_ExpressionValue_test.res
index b09e20ae..71fd9f61 100644
--- a/packages/squiggle-lang/__tests__/ReducerInterface/ReducerInterface_ExpressionValue_test.res
+++ b/packages/squiggle-lang/__tests__/ReducerInterface/ReducerInterface_ExpressionValue_test.res
@@ -1,11 +1,11 @@
-open ReducerInterface.ExternalExpressionValue
+open ReducerInterface.InternalExpressionValue
 open Jest
 open Expect
 
 describe("ExpressionValue", () => {
-  test("argsToString", () => expect([EvNumber(1.), EvString("a")]->argsToString)->toBe("1,'a'"))
+  test("argsToString", () => expect([IEvNumber(1.), IEvString("a")]->argsToString)->toBe("1,'a'"))
 
   test("toStringFunctionCall", () =>
-    expect(("fn", [EvNumber(1.), EvString("a")])->toStringFunctionCall)->toBe("fn(1,'a')")
+    expect(("fn", [IEvNumber(1.), IEvString("a")])->toStringFunctionCall)->toBe("fn(1,'a')")
   )
 })
diff --git a/packages/squiggle-lang/__tests__/ReducerProject/ReducerProject_includes_test.res b/packages/squiggle-lang/__tests__/ReducerProject/ReducerProject_includes_test.res
new file mode 100644
index 00000000..bce7c84b
--- /dev/null
+++ b/packages/squiggle-lang/__tests__/ReducerProject/ReducerProject_includes_test.res
@@ -0,0 +1,33 @@
+@@warning("-44")
+module InternalExpressionValue = ReducerInterface_InternalExpressionValue
+module Project = ForTS_ReducerProject
+module Bindings = Reducer_Bindings
+
+open Jest
+open Expect
+open Expect.Operators
+
+Only.describe("Parse includes", () => {
+  let project = Project.createProject()
+  Project.setSource(
+    project,
+    "main",
+    `
+#include 'common'
+x=1`,
+  )
+  Project.parseIncludes(project, "main")
+  test("dependencies", () => {
+    expect(Project.getDependencies(project, "main")) == ["common"]
+  })
+  test("dependents", () => {
+    expect(Project.getDependents(project, "main")) == []
+  })
+  test("getIncludes", () => {
+    let mainIncludes = Project.getIncludes(project, "main")
+    switch mainIncludes {
+    | Ok(includes) => expect(includes) == ["common"]
+    | Error(error) => fail(error->Reducer_ErrorValue.errorToString)
+    }
+  })
+})
diff --git a/packages/squiggle-lang/__tests__/ReducerProject/ReducerProject_test.res b/packages/squiggle-lang/__tests__/ReducerProject/ReducerProject_test.res
new file mode 100644
index 00000000..d258d71a
--- /dev/null
+++ b/packages/squiggle-lang/__tests__/ReducerProject/ReducerProject_test.res
@@ -0,0 +1,174 @@
+@@warning("-44")
+module InternalExpressionValue = ReducerInterface_InternalExpressionValue
+module Project = ForTS_ReducerProject
+module Bindings = Reducer_Bindings
+
+open Jest
+open Expect
+open Expect.Operators
+
+// test("", () => expect(1)->toBe(1))
+
+let runFetchResult = (project, sourceId) => {
+  Project.run(project, sourceId)
+  Project.getResult(project, sourceId)->InternalExpressionValue.toStringResult
+}
+
+let runFetchBindings = (project, sourceId) => {
+  Project.run(project, sourceId)
+  Project.getBindings(project, sourceId)
+  ->InternalExpressionValue.IEvBindings
+  ->InternalExpressionValue.toString
+}
+
+test("setting continuation", () => {
+  let project = Project.createProject()
+  let privateProject = project->Project.T.Private.castToInternalProject
+  let sampleBindings = Bindings.emptyBindings->Bindings.set("test", IEvVoid)
+  Project.Private.setContinuation(privateProject, "main", sampleBindings)
+  let answer = Project.Private.getContinuation(privateProject, "main")
+  expect(answer)->toBe(sampleBindings)
+})
+
+test("test result true", () => {
+  let project = Project.createProject()
+  Project.setSource(project, "main", "true")
+  runFetchResult(project, "main")->expect->toBe("Ok(true)")
+})
+
+test("test result false", () => {
+  let project = Project.createProject()
+  Project.setSource(project, "main", "false")
+  runFetchResult(project, "main")->expect->toBe("Ok(false)")
+})
+
+test("test library", () => {
+  let project = Project.createProject()
+  Project.setSource(project, "main", "x=Math.pi; x")
+  runFetchResult(project, "main")->expect->toBe("Ok(3.141592653589793)")
+})
+
+test("test bindings", () => {
+  let project = Project.createProject()
+  Project.setSource(project, "variables", "myVariable=666")
+  runFetchBindings(project, "variables")->expect->toBe("@{myVariable: 666}")
+})
+
+describe("project1", () => {
+  let project = Project.createProject()
+  Project.setSource(project, "first", "x=1")
+  Project.setSource(project, "main", "x")
+  Project.setContinues(project, "main", ["first"])
+
+  test("runOrder", () => {
+    expect(Project.getRunOrder(project)) == ["first", "main"]
+  })
+  test("dependents first", () => {
+    expect(Project.getDependents(project, "first")) == ["main"]
+  })
+  test("dependencies first", () => {
+    expect(Project.getDependencies(project, "first")) == []
+  })
+  test("dependents main", () => {
+    expect(Project.getDependents(project, "main")) == []
+  })
+  test("dependencies main", () => {
+    expect(Project.getDependencies(project, "main")) == ["first"]
+  })
+  test("test result", () => {
+    runFetchResult(project, "main")->expect->toBe("Ok(1)")
+  })
+  test("test bindings", () => {
+    runFetchBindings(project, "main")->expect->toBe("@{x: 1}")
+  })
+})
+
+describe("project2", () => {
+  let project = Project.createProject()
+  Project.setContinues(project, "main", ["second"])
+  Project.setContinues(project, "second", ["first"])
+  Project.setSource(project, "first", "x=1")
+  Project.setSource(project, "second", "y=2")
+  Project.setSource(project, "main", "y")
+
+  test("runOrder", () => {
+    expect(Project.getRunOrder(project)) == ["first", "second", "main"]
+  })
+  test("runOrderFor", () => {
+    expect(Project.getRunOrderFor(project, "first")) == ["first"]
+  })
+  test("dependencies first", () => {
+    expect(Project.getDependencies(project, "first")) == []
+  })
+  test("dependents first", () => {
+    expect(Project.getDependents(project, "first")) == ["second", "main"]
+  })
+  test("dependents main", () => {
+    expect(Project.getDependents(project, "main")) == []
+  })
+  test("dependencies main", () => {
+    expect(Project.getDependencies(project, "main")) == ["first", "second"]
+  })
+  test("test result", () => {
+    runFetchResult(project, "main")->expect->toBe("Ok(2)")
+  })
+  test("test bindings", () => {
+    runFetchBindings(project, "main")->expect->toBe("@{x: 1,y: 2}")
+  })
+})
+
+describe("project with include", () => {
+  let project = Project.createProject()
+  Project.setContinues(project, "main", ["second"])
+  Project.setContinues(project, "second", ["first"])
+
+  Project.setSource(
+    project,
+    "first",
+    `
+  #include 'common'
+  x=1`,
+  )
+  Project.parseIncludes(project, "first")
+  Project.parseIncludes(project, "first") //The only way of setting includes
+  //Don't forget to parse includes after changing the source
+
+  Project.setSource(project, "common", "common=0")
+  Project.setSource(
+    project,
+    "second",
+    `
+  #include 'common'
+  y=2`,
+  )
+  Project.parseIncludes(project, "second") //The only way of setting includes
+
+  Project.setSource(project, "main", "y")
+
+  test("runOrder", () => {
+    expect(Project.getRunOrder(project)) == ["common", "first", "second", "main"]
+  })
+
+  test("runOrderFor", () => {
+    expect(Project.getRunOrderFor(project, "first")) == ["common", "first"]
+  })
+
+  test("dependencies first", () => {
+    expect(Project.getDependencies(project, "first")) == ["common"]
+  })
+  test("dependents first", () => {
+    expect(Project.getDependents(project, "first")) == ["second", "main"]
+  })
+  test("dependents main", () => {
+    expect(Project.getDependents(project, "main")) == []
+  })
+  test("dependencies main", () => {
+    expect(Project.getDependencies(project, "main")) == ["common", "first", "second"]
+  })
+  test("test result", () => {
+    runFetchResult(project, "main")->expect->toBe("Ok(2)")
+  })
+  test("test bindings", () => {
+    runFetchBindings(project, "main")->expect->toBe("@{common: 0,x: 1,y: 2}")
+  })
+})
diff --git a/packages/squiggle-lang/__tests__/ReducerProject/ReducerProject_tutorial_0_test.res b/packages/squiggle-lang/__tests__/ReducerProject/ReducerProject_tutorial_0_test.res
new file mode 100644
index 00000000..d6f43904
--- /dev/null
+++ b/packages/squiggle-lang/__tests__/ReducerProject/ReducerProject_tutorial_0_test.res
@@ -0,0 +1,109 @@
+@@warning("-44")
+module InternalExpressionValue = ReducerInterface_InternalExpressionValue
+module Project = ForTS_ReducerProject
+module Bindings = Reducer_Bindings
+
+open Jest
+open Expect
+open Expect.Operators
+
+describe("ReducerProject Tutorial", () => {
+  describe("Single source", () => {
+    /*
+Case "Running a single source". 
+*/
+    test("run", () => {
+      /* Let's start with running a single source and getting Result as well as the Bindings 
+       First you need to create a project. A project is a collection of sources. 
+       Project takes care of the dependencies between the sources, correct compilation and run order. 
+       You can run any source in the project. It will be compiled and run if it is not already done else already existing results will be presented.
+       The dependencies will be automatically compiled and run. So you don't need to worry about that in a multi source project.
+       In summary you issue a run command on the whole project or on a specific source to ensure that there is a result for that source.
+ */
+      let project = Project.createProject()
+      /* Every source has a name. This is used for debugging, dependencies and error messages. */
+      Project.setSource(project, "main", "1 + 2")
+      /* Let's run "main" source. */
+      project->Project.run("main")
+      /* Now you have a result for "main" source. 
+       Running one by one is necessary for UI to navigate among the sources and to see the results by source. 
+       And you're free to run any source you want. 
+       You will look at the results of this source and you don't want to run the others if not required.
+ */
+
+      /* However, you could also run the whole project.
+       If you have all the sources, you can always run the whole project. 
+       Dependencies and recompiling on demand will be taken care of by the project. 
+ */
+      project->Project.runAll
+
+      /* Either with run or runAll you executed the project. 
+       You can get the result of a specific source by calling getResult for that source. 
+       You can get the bindings of a specific source by calling getBindings for that source. 
+       If there is any runtime error, getResult will return the error.
+
+       Note that getResult returns None if the source has not been run.
+       Getting None means you have forgotten to run the source.
+ */
+      let result = project->Project.getResult("main")
+      let bindings = project->Project.getBindings("main")
+
+      /* Let's display the result and bindings */
+      (
+        result->InternalExpressionValue.toStringResult,
+        bindings->InternalExpressionValue.IEvBindings->InternalExpressionValue.toString,
+      )->expect == ("Ok(3)", "@{}")
+      /* You've got 3 with empty bindings. */
+    })
+
+    test("run summary", () => {
+      let project = Project.createProject()
+      Project.setSource(project, "main", "1 + 2")
+      Project.runAll(project)
+      let result = Project.getResult(project, "main")
+      let bindings = Project.getBindings(project, "main")
+      /* Now you have external bindings and external result. */
+      (
+        result->InternalExpressionValue.toStringResult,
+        bindings->InternalExpressionValue.IEvBindings->InternalExpressionValue.toString,
+      )->expect == ("Ok(3)", "@{}")
+    })
+
+    test("run with an environment", () => {
+      /* Running the source code like above allows you to set a custom environment */
+      let project = Project.createProject()
+
+      /* Optional. Set your custom environment anytime before running */
+      Project.setEnvironment(project, InternalExpressionValue.defaultEnvironment)
+
+      Project.setSource(project, "main", "1 + 2")
+      Project.runAll(project)
+      let result = Project.getResult(project, "main")
+      let _bindings = Project.getBindings(project, "main")
+      result->InternalExpressionValue.toStringResult->expect == "Ok(3)"
+    })
+
+    test("shortcut", () => {
+      /* If you are running single source without includes and you don't need a custom environment, you can use the shortcut. */
+      /* Examples above was to prepare you for the multi source tutorial. */
+      let (result, bindings) = Project.evaluate("1+2")
+      (
+        result->InternalExpressionValue.toStringResult,
+        bindings->InternalExpressionValue.IEvBindings->InternalExpressionValue.toString,
+      )->expect == ("Ok(3)", "@{}")
+    })
+  })
+})
+
+//TODO multiple sources
+//TODO multiple sources with includes. Introduction to includes
+//TODO multiple sources with multi level includes. Cycle detection
+//TODO
+//TODO: Implement a runOrder consideration - clean results based on run order.
+//TODO: runOrder vs setSource/touchSource
+//TODO: Advanced details: (below)
+//TODO  runOrder. includes vs continues. Run order based reexecution
+//TODO: dependents and reexecution
+//TODO: dependencies and reexecution
+//TODO: cleanAllResults clean
+//TODO: cleanAll clean 
diff --git a/packages/squiggle-lang/__tests__/ReducerProject/ReducerProject_tutorial_1_multisource_test.res b/packages/squiggle-lang/__tests__/ReducerProject/ReducerProject_tutorial_1_multisource_test.res
new file mode 100644
index 00000000..4362fcf6
--- /dev/null
+++ b/packages/squiggle-lang/__tests__/ReducerProject/ReducerProject_tutorial_1_multisource_test.res
@@ -0,0 +1,112 @@
+@@warning("-44")
+module InternalExpressionValue = ReducerInterface_InternalExpressionValue
+module Project = ForTS_ReducerProject
+module Bindings = Reducer_Bindings
+
+open Jest
+open Expect
+open Expect.Operators
+
+describe("ReducerProject Tutorial", () => {
+  describe("Multi source", () => {
+    /*
+     Case "Running multiple sources" */
+    test("Chaining", () => {
+      let project = Project.createProject()
+      /* This time let's add 3 sources and chain them together */
+      Project.setSource(project, "source1", "x=1")
+
+      Project.setSource(project, "source2", "y=2")
+      /* To run, source2 depends on source1 */
+      Project.setContinues(project, "source2", ["source1"])
+
+      Project.setSource(project, "source3", "z=3")
+      /* To run, source3 depends on source2 */
+      Project.setContinues(project, "source3", ["source2"])
+
+      /* Now we can run the project */
+      Project.runAll(project)
+
+      /* And let's check the result and bindings of source3 */
+      let result3 = Project.getResult(project, "source3")
+      let bindings3 = Project.getBindings(project, "source3")
+
+      (
+        result3->InternalExpressionValue.toStringResult,
+        bindings3->InternalExpressionValue.IEvBindings->InternalExpressionValue.toString,
+      )->expect == ("Ok(())", "@{x: 1,y: 2,z: 3}")
+    })
+
+    test("Depending", () => {
+      /* Instead of chaining the sources, we could have a dependency tree */
+      /* The point here is that any source can depend on multiple sources */
+      let project = Project.createProject()
+
+      /* This time source1 and source2 are not depending on anything */
+      Project.setSource(project, "source1", "x=1")
+      Project.setSource(project, "source2", "y=2")
+
+      Project.setSource(project, "source3", "z=3")
+      /* To run, source3 depends on source1 and source3 together */
+      Project.setContinues(project, "source3", ["source1", "source2"])
+
+      /* Now we can run the project */
+      Project.runAll(project)
+
+      /* And let's check the result and bindings of source3 */
+      let result3 = Project.getResult(project, "source3")
+      let bindings3 = Project.getBindings(project, "source3")
+
+      (
+        result3->InternalExpressionValue.toStringResult,
+        bindings3->InternalExpressionValue.IEvBindings->InternalExpressionValue.toString,
+      )->expect == ("Ok(())", "@{x: 1,y: 2,z: 3}")
+    })
+
+    test("Intro to including", () => {
+      /* Though it would not be practical for a storybook, 
+        let's write the same project above with includes.
+        You will see that parsing includes is setting the dependencies the same way as before. */
+      let project = Project.createProject()
+
+      /* This time source1 and source2 are not depending on anything */
+      Project.setSource(project, "source1", "x=1")
+      Project.setSource(project, "source2", "y=2")
+
+      Project.setSource(
+        project,
+        "source3",
+        `
+      #include "source1"
+      #include "source2"
+      z=3`,
+      )
+      /* We need to parse the includes to set the dependencies */
+      Project.parseIncludes(project, "source3")
+
+      /* Now we can run the project */
+      Project.runAll(project)
+
+      /* And let's check the result and bindings of source3 
+      This time you are getting all the variables because we are including the other sources 
+      Behind the scenes parseIncludes is setting the dependencies */
+      let result3 = Project.getResult(project, "source3")
+      let bindings3 = Project.getBindings(project, "source3")
+
+      (
+        result3->InternalExpressionValue.toStringResult,
+        bindings3->InternalExpressionValue.IEvBindings->InternalExpressionValue.toString,
+      )->expect == ("Ok(())", "@{x: 1,y: 2,z: 3}")
+      /*
+      Doing it like this is too verbose for a storybook 
+      But I hope you have seen the relation of setContinues and parseIncludes */
+      /*
+         Dealing with includes needs more. 
+         - There are parse errors
+         - There are cyclic includes
+         - And the depended source1 and source2 is not already there in the project
+         - If you knew the includes before hand there would not be point of the include directive.
+         More on those on the next section. */
+    })
+  })
+})
diff --git a/packages/squiggle-lang/__tests__/ReducerProject/ReducerProject_tutorial_2_includes_test.res b/packages/squiggle-lang/__tests__/ReducerProject/ReducerProject_tutorial_2_includes_test.res
new file mode 100644
index 00000000..a4c2e0a3
--- /dev/null
+++ b/packages/squiggle-lang/__tests__/ReducerProject/ReducerProject_tutorial_2_includes_test.res
@@ -0,0 +1,156 @@
+@@warning("-44")
+module InternalExpressionValue = ReducerInterface_InternalExpressionValue
+module Project = ForTS_ReducerProject
+module Bindings = Reducer_Bindings
+
+open Jest
+open Expect
+open Expect.Operators
+
+describe("ReducerProject Tutorial", () => {
+  /* Case: Includes
+In the previous tutorial we have set the similarity between setContinues and parseIncludes.
+Here we will finally proceed to a real life scenario. */
+
+  describe("parseIncludes", () => {
+    /* Here we investigate the details about parseIncludes, before setting up a real life senario in the next section. */
+    /* Everything happens inside a project, so let's have a project */
+    let project = Project.createProject()
+    Project.setSource(
+      project,
+      "main",
+      `
+    #include "common"
+    x=1
+    `,
+    )
+    /* We need to parse includes after changing the source */
+    Project.parseIncludes(project, "main")
+    test("getDependencies", () => {
+      /* Parse includes has set the dependencies */
+      Project.getDependencies(project, "main")->expect == ["common"]
+      /* If there were no includes than there would be no dependencies */
+      /* However if there was a syntax error at includes then would be no dependencies also */
+      /* Therefore looking at dependencies is not the right way to load includes */
+      /* getDependencies does not distinguish between setContinues or parseIncludes */
+    })
+    test("getIncludes", () => {
+      /* Parse includes has set the includes */
+      switch Project.getIncludes(project, "main") {
+      | Ok(includes) => includes->expect == ["common"]
+      | Error(err) => err->Reducer_ErrorValue.errorToString->fail
+      }
+      /* If the includes cannot be parsed then you get a syntax error.
+      Otherwise you get the includes.
+      If there is no syntax error then you can load that file and use setSource to add it to the project.
+      And so on recursively... */
+    })
+    test("getDependents", () => {
+      /* For any reason, you are able to query what other sources
+        include or depend on the current source.
+        But you don't need to use this to execute the projects.
+        It is provided for completeness of information. */
+      Project.getDependents(project, "main")->expect == []
+      /* Nothing is depending on or including main */
+    })
+
+    describe("Real Like", () => {
+      /* Now let's look at recursive and possibly cyclic includes */
+      /* There is no function provided to load the include files.
+    Because we have no idea if will it be an ordinary function or will it use promises.
+    Therefore one has to write a function to load sources recursively and and setSources
+    while checking for dependencies */
+
+      /* Let's make a dummy loader */
+      let loadSource = (sourceName: string) =>
+        switch sourceName {
+        | "source1" => "x=1"
+        | "source2" => `
+            #include "source1"
+            y=2`
+        | "source3" => `
+            #include "source2"
+            z=3`
+        | _ => `source ${sourceName} not found`->Js.Exn.raiseError
+        }
+
+      /* let's recursively load the sources */
+      let rec loadIncludesRecursively = (project, sourceName, visited) => {
+        if Js.Array2.includes(visited, sourceName) {
+          /* Oh we have already visited this source. There is an include cycle */
+          "Cyclic include ${sourceName}"->Js.Exn.raiseError
+        } else {
+          let newVisited = Js.Array2.copy(visited)
+          let _ = Js.Array2.push(newVisited, sourceName)
+          /* Let's parse the includes and dive into them */
+          Project.parseIncludes(project, sourceName)
+          let rIncludes = Project.getIncludes(project, sourceName)
+          switch rIncludes {
+          /* Maybe there is an include syntax error */
+          | Error(err) => err->Reducer_ErrorValue.errorToString->Js.Exn.raiseError
+
+          | Ok(includes) =>
+            Belt.Array.forEach(includes, newIncludeName => {
+              /* We have got one of the new includes.
+               Let's load it and add it to the project */
+              let newSource = loadSource(newIncludeName)
+              Project.setSource(project, newIncludeName, newSource)
+              /* The new source is loaded and added to the project. */
+              /* Of course the new source might have includes too. */
+              /* Let's recursively load them */
+              loadIncludesRecursively(project, newIncludeName, newVisited)
+            })
+          }
+        }
+      }
+      /* As we have a fake source loader and a recursive include handler,
+       We can not set up a real project */
+
+      /* * Here starts our real life project! * */
+
+      let project = Project.createProject()
+
+      /* main includes source3 which includes source2 which includes source1 */
+      Project.setSource(
+        project,
+        "main",
+        `
+        #include "source3"
+        x+y+z
+        `,
+      )
+      /* Setting source requires parsing and loading the includes recursively */
+      loadIncludesRecursively(project, "main", []) //No visited yet
+
+      /* Let's salt it more. Let's have another source in the project which also has includes */
+      /* doubleX includes source1 which is eventually included by main as well */
+      Project.setSource(
+        project,
+        "doubleX",
+        `
+        #include "source1"
+        doubleX = x * 2
+        `,
+      )
+      loadIncludesRecursively(project, "doubleX", [])
+      /* Remember, any time you set a source, you need to load includes recursively */
+
+      /* As doubleX is not included by main, it is not loaded recursively.
+       So we link it to the project as a dependency */
+      Project.setContinues(project, "main", ["doubleX"])
+
+      /* Let's run the project */
+      Project.runAll(project)
+      let result = Project.getResult(project, "main")
+      let bindings = Project.getBindings(project, "main")
+      /* And see the result and bindings.. */
+      test("recursive includes", () => {
+        (
+          result->InternalExpressionValue.toStringResult,
+          bindings->InternalExpressionValue.IEvBindings->InternalExpressionValue.toString,
+        )->expect == ("Ok(6)", "@{doubleX: 2,x: 1,y: 2,z: 3}")
+        /* Everything as expected */
+      })
+    })
+  })
+})
diff --git a/packages/squiggle-lang/__tests__/ReducerProject/ReducerProject_tutorial_3_injecting_user_values.res b/packages/squiggle-lang/__tests__/ReducerProject/ReducerProject_tutorial_3_injecting_user_values.res
new file mode 100644
index 00000000..38d655c1
--- /dev/null
+++ b/packages/squiggle-lang/__tests__/ReducerProject/ReducerProject_tutorial_3_injecting_user_values.res
@@ -0,0 +1,39 @@
+@@warning("-44")
+module InternalExpressionValue = ReducerInterface_InternalExpressionValue
+module Project = ForTS_ReducerProject
+module Bindings = Reducer_Bindings
+
+open Jest
+open Expect
+open Expect.Operators
+
+describe("ReducerProject Tutorial", () => {
+  /* Let's build a project that depends on values from the UI */
+  let project = Project.createProject()
+  Project.setSource(project, "main", "x+y+z")
+  /* x, y and z is not defined in the project but they has to come from the user */
+  test("Injecting user values", () => {
+    /* User has input the values */
+    let x = 1
+    let y = 2
+    let z = 3
+    /* Then we construct a source code to define those values */
+    let userCode = `
+      x = ${x->Js.Int.toString}
+      y = ${y->Js.Int.toString}
+      z = ${z->Js.Int.toString}
+    `
+    /* We inject the user code into the project */
+    Project.setSource(project, "userCode", userCode)
+    /* "main" is depending on the user code */
+    Project.setContinues(project, "main", ["userCode"])
+    /* We can now run the project */
+    Project.runAll(project)
+    let result = Project.getResult(project, "main")
+    result->InternalExpressionValue.toStringResult->expect == "Ok(6)"
+  })
+})
+
+/* Note that this is not final version of the project */
+/* In the future, for safety, we will provide a way to inject values instead of a source code */
+/* But time is limited for now... */
diff --git a/packages/squiggle-lang/__tests__/ReducerProject/ReducerProject_tutorial_4_calling_functions.res b/packages/squiggle-lang/__tests__/ReducerProject/ReducerProject_tutorial_4_calling_functions.res
new file mode 100644
index 00000000..7e2471b5
--- /dev/null
+++ b/packages/squiggle-lang/__tests__/ReducerProject/ReducerProject_tutorial_4_calling_functions.res
@@ -0,0 +1,39 @@
+@@warning("-44")
+module InternalExpressionValue = ReducerInterface_InternalExpressionValue
+module Project = ForTS_ReducerProject
+module Bindings = Reducer_Bindings
+
+open Jest
+open Expect
+open Expect.Operators
+
+describe("ReducerProject Tutorial", () => {
+  /* Let's build a project to provide a function. */
+  /* But we will call that function on an array of user input. */
+  let project = Project.createProject()
+  Project.setSource(project, "library", "double(x) = x * 2")
+  /* userCode is not here yet but its dependency is fixed. So we can set it once and for all */
+  Project.setContinues(project, "userCode", ["library"])
+
+  let userValues = [1, 2, 3, 4, 5]
+
+  let userResults = Belt.Array.map(userValues, aUserValue => {
+    let userCode = `double(${aUserValue->Js.Int.toString})`
+    /* Put the constructed source in the project */
+    /* We have already set that it depends on "library" */
+    Project.setSource(project, "userCode", userCode)
+    /* Run the project */
+    Project.runAll(project)
+    /* Get the result */
+    Project.getResult(project, "userCode")
+    /* I have to remind you that the "library" is run only once and for all.
+     The library is not run for each user value. */
+  })
+
+  test("userResults", () => {
+    let userResultsAsString = Belt.Array.map(userResults, aResult =>
+      aResult->InternalExpressionValue.toStringResult
+    )
+    userResultsAsString->expect == ["Ok(2)", "Ok(4)", "Ok(6)", "Ok(8)", "Ok(10)"]
+  })
+})
diff --git a/packages/squiggle-lang/__tests__/SquiggleLibrary/SquiggleLibrary_FunctionRegistryLibrary_test.res b/packages/squiggle-lang/__tests__/SquiggleLibrary/SquiggleLibrary_FunctionRegistryLibrary_test.res
index 2418b4d8..693dffa5 100644
--- a/packages/squiggle-lang/__tests__/SquiggleLibrary/SquiggleLibrary_FunctionRegistryLibrary_test.res
+++ b/packages/squiggle-lang/__tests__/SquiggleLibrary/SquiggleLibrary_FunctionRegistryLibrary_test.res
@@ -2,8 +2,12 @@ open Jest
 open Expect
 open Reducer_TestHelpers
 
-let expectEvalToBeOk = (expr: string) =>
-  Reducer.evaluate(expr)->Reducer_Helpers.rRemoveDefaultsExternal->E.R.isOk->expect->toBe(true)
+let expectEvalToBeOk = (code: string) =>
+  Reducer_Expression.BackCompatible.evaluateString(code)
+  ->Reducer_Helpers.rRemoveDefaultsInternal
+  ->E.R.isOk
+  ->expect
+  ->toBe(true)
 
 let registry = FunctionRegistry_Library.registry
 let examples = E.A.to_list(FunctionRegistry_Core.Registry.allExamples(registry))
@@ -88,8 +92,8 @@ describe("FunctionRegistry Library", () => {
       ((fn, example)) => {
         let responseType =
           example
-          ->Reducer.evaluate
-          ->E.R2.fmap(ReducerInterface_InternalExpressionValue.externalValueToValueType)
+          ->Reducer_Expression.BackCompatible.evaluateString
+          ->E.R2.fmap(ReducerInterface_InternalExpressionValue.valueToValueType)
         let expectedOutputType = fn.output |> E.O.toExn("")
         expect(responseType)->toEqual(Ok(expectedOutputType))
       },
diff --git a/packages/squiggle-lang/src/js/index.ts b/packages/squiggle-lang/src/js/index.ts
index acee005c..c5f66eed 100644
--- a/packages/squiggle-lang/src/js/index.ts
+++ b/packages/squiggle-lang/src/js/index.ts
@@ -1,3 +1,15 @@
+/* Some of the types have moved to ForTS__Types.
+Needs to be reimported here if necessary and distribution related 
+
+We only need distribution related extras for back compatibility. Umur
+
+Instead of a global function namespace we should use modules under ForTS directly maybe renaming them for ease.
+
+.e.g. Project.run(project)
+.e.g. Distribution.makeSampleSetDist
+
+*/
+
 import * as _ from "lodash";
 import type {
   environment,
@@ -44,162 +56,164 @@ export let defaultSamplingInputs: environment = {
   xyPointLength: 10000,
 };
 
-export function run(
-  squiggleString: string,
-  bindings?: externalBindings,
-  environment?: environment,
-  imports?: jsImports
-): result<squiggleExpression, errorValue> {
-  let b = bindings ? bindings : defaultBindings;
-  let i = imports ? imports : defaultImports;
-  let e = environment ? environment : defaultEnvironment;
-  let res: result<expressionValue, errorValue> = evaluateUsingOptions(
-    { externalBindings: mergeImportsWithBindings(b, i), environment: e },
-    squiggleString
-  );
-  return resultMap(res, (x) => createTsExport(x, e));
-}
+/* Umur: All the functions below are invalid. ForTS_Reducer project is the new way to do this. */
 
-// Run Partial. A partial is a block of code that doesn't return a value
-export function runPartial(
-  squiggleString: string,
-  bindings?: externalBindings,
-  environment?: environment,
-  imports?: jsImports
-): result<externalBindings, errorValue> {
-  let b = bindings ? bindings : defaultBindings;
-  let i = imports ? imports : defaultImports;
-  let e = environment ? environment : defaultEnvironment;
+// export function run(
+//   squiggleString: string,
+//   bindings?: externalBindings,
+//   environment?: environment,
+//   imports?: jsImports
+// ): result<squiggleExpression, errorValue> {
+//   let b = bindings ? bindings : defaultBindings;
+//   let i = imports ? imports : defaultImports;
+//   let e = environment ? environment : defaultEnvironment;
+//   let res: result<expressionValue, errorValue> = evaluateUsingOptions(
+//     { externalBindings: mergeImportsWithBindings(b, i), environment: e },
+//     squiggleString
+//   );
+//   return resultMap(res, (x) => createTsExport(x, e));
+// }
 
-  return evaluatePartialUsingExternalBindings(
-    squiggleString,
-    mergeImportsWithBindings(b, i),
-    e
-  );
-}
+// // Run Partial. A partial is a block of code that doesn't return a value
+// export function runPartial(
+//   squiggleString: string,
+//   bindings?: externalBindings,
+//   environment?: environment,
+//   imports?: jsImports
+// ): result<externalBindings, errorValue> {
+//   let b = bindings ? bindings : defaultBindings;
+//   let i = imports ? imports : defaultImports;
+//   let e = environment ? environment : defaultEnvironment;
 
-export function runForeign(
-  fn: lambdaValue,
-  args: jsValue[],
-  environment?: environment
-): result<squiggleExpression, errorValue> {
-  let e = environment ? environment : defaultEnvironment;
-  let res: result<expressionValue, errorValue> = foreignFunctionInterface(
-    fn,
-    args.map(jsValueToExpressionValue),
-    e
-  );
-  return resultMap(res, (x) => createTsExport(x, e));
-}
+//   return evaluatePartialUsingExternalBindings(
+//     squiggleString,
+//     mergeImportsWithBindings(b, i),
+//     e
+//   );
+// }
 
-function mergeImportsWithBindings(
-  bindings: externalBindings,
-  imports: jsImports
-): externalBindings {
-  let transformedImports = Object.fromEntries(
-    Object.entries(imports).map(([key, value]) => [
-      "$" + key,
-      jsValueToBinding(value),
-    ])
-  );
-  return _.merge(bindings, transformedImports);
-}
+// export function runForeign(
+//   fn: lambdaValue,
+//   args: jsValue[],
+//   environment?: environment
+// ): result<squiggleExpression, errorValue> {
+//   let e = environment ? environment : defaultEnvironment;
+//   let res: result<expressionValue, errorValue> = foreignFunctionInterface(
+//     fn,
+//     args.map(jsValueToExpressionValue),
+//     e
+//   );
+//   return resultMap(res, (x) => createTsExport(x, e));
+// }
 
-type jsImports = { [key: string]: jsValue };
+// function mergeImportsWithBindings(
+//   bindings: externalBindings,
+//   imports: jsImports
+// ): externalBindings {
+//   let transformedImports = Object.fromEntries(
+//     Object.entries(imports).map(([key, value]) => [
+//       "$" + key,
+//       jsValueToBinding(value),
+//     ])
+//   );
+//   return _.merge(bindings, transformedImports);
+// }
 
-export let defaultImports: jsImports = {};
-export let defaultBindings: externalBindings = {};
+// type jsImports = { [key: string]: jsValue };
 
-export function mergeBindings(
-  allBindings: externalBindings[]
-): externalBindings {
-  return allBindings.reduce((acc, x) => ({ ...acc, ...x }));
-}
+// export let defaultImports: jsImports = {};
+// export let defaultBindings: externalBindings = {};
 
-function createTsExport(
-  x: expressionValue,
-  environment: environment
-): squiggleExpression {
-  switch (x) {
-    case "EvVoid":
-      return tag("void", "");
-    default: {
-      switch (x.tag) {
-        case "EvArray":
-          // genType doesn't convert anything more than 2 layers down into {tag: x, value: x}
-          // format, leaving it as the raw values. This converts the raw values
-          // directly into typescript values.
-          //
-          // The casting here is because genType is about the types of the returned
-          // values, claiming they are fully recursive when that's not actually the
-          // case
-          return tag(
-            "array",
-            x.value.map(
-              (arrayItem): squiggleExpression =>
-                convertRawToTypescript(
-                  arrayItem as unknown as rescriptExport,
-                  environment
-                )
-            )
-          );
-        case "EvArrayString":
-          return tag("arraystring", x.value);
-        case "EvBool":
-          return tag("boolean", x.value);
-        case "EvCall":
-          return tag("call", x.value);
-        case "EvLambda":
-          return tag("lambda", x.value);
-        case "EvDistribution":
-          return tag("distribution", new Distribution(x.value, environment));
-        case "EvNumber":
-          return tag("number", x.value);
-        case "EvRecord":
-          // genType doesn't support records, so we have to do the raw conversion ourself
-          let result: tagged<"record", { [key: string]: squiggleExpression }> =
-            tag(
-              "record",
-              _.mapValues(x.value, (x: unknown) =>
-                convertRawToTypescript(x as rescriptExport, environment)
-              )
-            );
-          return result;
-        case "EvString":
-          return tag("string", x.value);
-        case "EvSymbol":
-          return tag("symbol", x.value);
-        case "EvDate":
-          return tag("date", x.value);
-        case "EvTimeDuration":
-          return tag("timeDuration", x.value);
-        case "EvDeclaration":
-          return tag("lambdaDeclaration", x.value);
-        case "EvTypeIdentifier":
-          return tag("typeIdentifier", x.value);
-        case "EvType":
-          let typeResult: tagged<
-            "type",
-            { [key: string]: squiggleExpression }
-          > = tag(
-            "type",
-            _.mapValues(x.value, (x: unknown) =>
-              convertRawToTypescript(x as rescriptExport, environment)
-            )
-          );
-          return typeResult;
-        case "EvModule":
-          let moduleResult: tagged<
-            "module",
-            { [key: string]: squiggleExpression }
-          > = tag(
-            "module",
-            _.mapValues(x.value, (x: unknown) =>
-              convertRawToTypescript(x as rescriptExport, environment)
-            )
-          );
-          return moduleResult;
-      }
-    }
-  }
-}
+// export function mergeBindings(
+//   allBindings: externalBindings[]
+// ): externalBindings {
+//   return allBindings.reduce((acc, x) => ({ ...acc, ...x }));
+// }
+
+// function createTsExport(
+//   x: expressionValue,
+//   environment: environment
+// ): squiggleExpression {
+//   switch (x) {
+//     case "EvVoid":
+//       return tag("void", "");
+//     default: {
+//       switch (x.tag) {
+//         case "EvArray":
+//           // genType doesn't convert anything more than 2 layers down into {tag: x, value: x}
+//           // format, leaving it as the raw values. This converts the raw values
+//           // directly into typescript values.
+//           //
+//           // The casting here is because genType is about the types of the returned
+//           // values, claiming they are fully recursive when that's not actually the
+//           // case
+//           return tag(
+//             "array",
+//             x.value.map(
+//               (arrayItem): squiggleExpression =>
+//                 convertRawToTypescript(
+//                   arrayItem as unknown as rescriptExport,
+//                   environment
+//                 )
+//             )
+//           );
+//         case "EvArrayString":
+//           return tag("arraystring", x.value);
+//         case "EvBool":
+//           return tag("boolean", x.value);
+//         case "EvCall":
+//           return tag("call", x.value);
+//         case "EvLambda":
+//           return tag("lambda", x.value);
+//         case "EvDistribution":
+//           return tag("distribution", new Distribution(x.value, environment));
+//         case "EvNumber":
+//           return tag("number", x.value);
+//         case "EvRecord":
+//           // genType doesn't support records, so we have to do the raw conversion ourself
+//           let result: tagged<"record", { [key: string]: squiggleExpression }> =
+//             tag(
+//               "record",
+//               _.mapValues(x.value, (x: unknown) =>
+//                 convertRawToTypescript(x as rescriptExport, environment)
+//               )
+//             );
+//           return result;
+//         case "EvString":
+//           return tag("string", x.value);
+//         case "EvSymbol":
+//           return tag("symbol", x.value);
+//         case "EvDate":
+//           return tag("date", x.value);
+//         case "EvTimeDuration":
+//           return tag("timeDuration", x.value);
+//         case "EvDeclaration":
+//           return tag("lambdaDeclaration", x.value);
+//         case "EvTypeIdentifier":
+//           return tag("typeIdentifier", x.value);
+//         case "EvType":
+//           let typeResult: tagged<
+//             "type",
+//             { [key: string]: squiggleExpression }
+//           > = tag(
+//             "type",
+//             _.mapValues(x.value, (x: unknown) =>
+//               convertRawToTypescript(x as rescriptExport, environment)
+//             )
+//           );
+//           return typeResult;
+//         case "EvModule":
+//           let moduleResult: tagged<
+//             "module",
+//             { [key: string]: squiggleExpression }
+//           > = tag(
+//             "module",
+//             _.mapValues(x.value, (x: unknown) =>
+//               convertRawToTypescript(x as rescriptExport, environment)
+//             )
+//           );
+//           return moduleResult;
+//       }
+//     }
+//   }
+// }
diff --git a/packages/squiggle-lang/src/js/rescript_interop.ts b/packages/squiggle-lang/src/js/rescript_interop.ts
index 3dca8165..1031dd3e 100644
--- a/packages/squiggle-lang/src/js/rescript_interop.ts
+++ b/packages/squiggle-lang/src/js/rescript_interop.ts
@@ -1,269 +1,279 @@
-import * as _ from "lodash";
-import type {
-  expressionValue,
-  mixedShape,
-  sampleSetDist,
-  genericDist,
-  environment,
-  symbolicDist,
-  discreteShape,
-  continuousShape,
-  lambdaValue,
-  lambdaDeclaration,
-  declarationArg,
-} from "../rescript/TypescriptInterface.gen";
-import { Distribution } from "./distribution";
-import { tagged, tag } from "./types";
+/** 
+ Umur: Delete this file! There is nothing left to see here.
+**/
+
+// import * as _ from "lodash";
+// import type {
+//   // expressionValue,
+//   mixedShape,
+//   sampleSetDist,
+//   genericDist,
+//   // environment,
+//   symbolicDist,
+//   discreteShape,
+//   continuousShape,
+//   // lambdaValue,
+//   // lambdaDeclaration,
+//   // declarationArg,
+// } from "../rescript/TypescriptInterface.gen";
+// import { Distribution } from "./distribution";
+// import { tagged, tag } from "./types";
 // This file is here to compensate for genType not fully recursively converting types
 
 // Raw rescript types.
-export type rescriptExport =
-  | 0 // EvVoid
-  | {
-      TAG: 0; // EvArray
-      _0: rescriptExport[];
-    }
-  | {
-      TAG: 1; // EvString
-      _0: string[];
-    }
-  | {
-      TAG: 2; // EvBool
-      _0: boolean;
-    }
-  | {
-      TAG: 3; // EvCall
-      _0: string;
-    }
-  | {
-      TAG: 4; // EvDistribution
-      _0: rescriptDist;
-    }
-  | {
-      TAG: 5; // EvLambda
-      _0: lambdaValue;
-    }
-  | {
-      TAG: 6; // EvNumber
-      _0: number;
-    }
-  | {
-      TAG: 7; // EvRecord
-      _0: { [key: string]: rescriptExport };
-    }
-  | {
-      TAG: 8; // EvString
-      _0: string;
-    }
-  | {
-      TAG: 9; // EvSymbol
-      _0: string;
-    }
-  | {
-      TAG: 10; // EvDate
-      _0: Date;
-    }
-  | {
-      TAG: 11; // EvTimeDuration
-      _0: number;
-    }
-  | {
-      TAG: 12; // EvDeclaration
-      _0: rescriptLambdaDeclaration;
-    }
-  | {
-      TAG: 13; // EvTypeIdentifier
-      _0: string;
-    }
-  | {
-      TAG: 14; // EvModule
-      _0: { [key: string]: rescriptExport };
-    };
+// Umur: Rescript expression values are opaque!
+// export type rescriptExport =
+//   | 0 // EvVoid
+//   | {
+//       TAG: 0; // EvArray
+//       _0: rescriptExport[];
+//     }
+//   | {
+//       TAG: 1; // EvString
+//       _0: string[];
+//     }
+//   | {
+//       TAG: 2; // EvBool
+//       _0: boolean;
+//     }
+//   | {
+//       TAG: 3; // EvCall
+//       _0: string;
+//     }
+//   | {
+//       TAG: 4; // EvDistribution
+//       _0: rescriptDist;
+//     }
+//   | {
+//       TAG: 5; // EvLambda
+//       _0: lambdaValue;
+//     }
+//   | {
+//       TAG: 6; // EvNumber
+//       _0: number;
+//     }
+//   | {
+//       TAG: 7; // EvRecord
+//       _0: { [key: string]: rescriptExport };
+//     }
+//   | {
+//       TAG: 8; // EvString
+//       _0: string;
+//     }
+//   | {
+//       TAG: 9; // EvSymbol
+//       _0: string;
+//     }
+//   | {
+//       TAG: 10; // EvDate
+//       _0: Date;
+//     }
+//   | {
+//       TAG: 11; // EvTimeDuration
+//       _0: number;
+//     }
+//   | {
+//       TAG: 12; // EvDeclaration
+//       _0: rescriptLambdaDeclaration;
+//     }
+//   | {
+//       TAG: 13; // EvTypeIdentifier
+//       _0: string;
+//     }
+//   | {
+//       TAG: 14; // EvModule
+//       _0: { [key: string]: rescriptExport };
+//     };
 
-type rescriptDist =
-  | { TAG: 0; _0: rescriptPointSetDist }
-  | { TAG: 1; _0: sampleSetDist }
-  | { TAG: 2; _0: symbolicDist };
+// Umur: opaque type
+// type rescriptDist =
+//   | { TAG: 0; _0: rescriptPointSetDist }
+//   | { TAG: 1; _0: sampleSetDist }
+//   | { TAG: 2; _0: symbolicDist };
 
-type rescriptPointSetDist =
-  | {
-      TAG: 0; // Mixed
-      _0: mixedShape;
-    }
-  | {
-      TAG: 1; // Discrete
-      _0: discreteShape;
-    }
-  | {
-      TAG: 2; // ContinuousShape
-      _0: continuousShape;
-    };
+// Umur: opaque type, no conversion
+// type rescriptPointSetDist =
+//   | {
+//       TAG: 0; // Mixed
+//       _0: mixedShape;
+//     }
+//   | {
+//       TAG: 1; // Discrete
+//       _0: discreteShape;
+//     }
+//   | {
+//       TAG: 2; // ContinuousShape
+//       _0: continuousShape;
+//     };
 
-type rescriptLambdaDeclaration = {
-  readonly fn: lambdaValue;
-  readonly args: rescriptDeclarationArg[];
-};
+// type rescriptLambdaDeclaration = {
+//   readonly fn: lambdaValue;
+//   readonly args: rescriptDeclarationArg[];
+// };
 
-type rescriptDeclarationArg =
-  | {
-      TAG: 0; // Float
-      min: number;
-      max: number;
-    }
-  | {
-      TAG: 1; // Date
-      min: Date;
-      max: Date;
-    };
+// type rescriptDeclarationArg =
+//   | {
+//       TAG: 0; // Float
+//       min: number;
+//       max: number;
+//     }
+//   | {
+//       TAG: 1; // Date
+//       min: Date;
+//       max: Date;
+//     };
 
-export type squiggleExpression =
-  | tagged<"symbol", string>
-  | tagged<"string", string>
-  | tagged<"call", string>
-  | tagged<"lambda", lambdaValue>
-  | tagged<"array", squiggleExpression[]>
-  | tagged<"arraystring", string[]>
-  | tagged<"boolean", boolean>
-  | tagged<"distribution", Distribution>
-  | tagged<"number", number>
-  | tagged<"date", Date>
-  | tagged<"timeDuration", number>
-  | tagged<"lambdaDeclaration", lambdaDeclaration>
-  | tagged<"record", { [key: string]: squiggleExpression }>
-  | tagged<"type", { [key: string]: squiggleExpression }>
-  | tagged<"typeIdentifier", string>
-  | tagged<"module", { [key: string]: squiggleExpression }>
-  | tagged<"void", string>;
+// Umur: Squiggle expressions are opaque!
+// export type squiggleExpression =
+//   | tagged<"symbol", string>
+//   | tagged<"string", string>
+//   | tagged<"call", string>
+//   | tagged<"lambda", lambdaValue>
+//   | tagged<"array", squiggleExpression[]>
+//   | tagged<"arraystring", string[]>
+//   | tagged<"boolean", boolean>
+//   | tagged<"distribution", Distribution>
+//   | tagged<"number", number>
+//   | tagged<"date", Date>
+//   | tagged<"timeDuration", number>
+//   | tagged<"lambdaDeclaration", lambdaDeclaration>
+//   | tagged<"record", { [key: string]: squiggleExpression }>
+//   | tagged<"type", { [key: string]: squiggleExpression }>
+//   | tagged<"typeIdentifier", string>
+//   | tagged<"module", { [key: string]: squiggleExpression }>
+//   | tagged<"void", string>;
 
-export { lambdaValue };
+// export { lambdaValue };
 
-export function convertRawToTypescript(
-  result: rescriptExport,
-  environment: environment
-): squiggleExpression {
-  if (typeof result === "number") {
-    // EvVoid
-    return tag("void", "");
-  }
-  switch (result.TAG) {
-    case 0: // EvArray
-      return tag(
-        "array",
-        result._0.map((x) => convertRawToTypescript(x, environment))
-      );
-    case 1: // EvArrayString
-      return tag("arraystring", result._0);
-    case 2: // EvBool
-      return tag("boolean", result._0);
-    case 3: // EvCall
-      return tag("call", result._0);
-    case 4: // EvDistribution
-      return tag(
-        "distribution",
-        new Distribution(
-          convertRawDistributionToGenericDist(result._0),
-          environment
-        )
-      );
-    case 5: // EvDistribution
-      return tag("lambda", result._0);
-    case 6: // EvNumber
-      return tag("number", result._0);
-    case 7: // EvRecord
-      return tag(
-        "record",
-        _.mapValues(result._0, (x) => convertRawToTypescript(x, environment))
-      );
-    case 8: // EvString
-      return tag("string", result._0);
-    case 9: // EvSymbol
-      return tag("symbol", result._0);
-    case 10: // EvDate
-      return tag("date", result._0);
-    case 11: // EvTimeDuration
-      return tag("number", result._0);
-    case 12: // EvDeclaration
-      return tag("lambdaDeclaration", {
-        fn: result._0.fn,
-        args: result._0.args.map(convertDeclaration),
-      });
-    case 13: // EvSymbol
-      return tag("typeIdentifier", result._0);
-    case 14: // EvModule
-      return tag(
-        "module",
-        _.mapValues(result._0, (x) => convertRawToTypescript(x, environment))
-      );
-  }
-}
+// Umur: Opaque type no conversion!
+// export function convertRawToTypescript(
+//   result: rescriptExport,
+//   environment: environment
+// ): squiggleExpression {
+//   if (typeof result === "number") {
+//     // EvVoid
+//     return tag("void", "");
+//   }
+//   switch (result.TAG) {
+//     case 0: // EvArray
+//       return tag(
+//         "array",
+//         result._0.map((x) => convertRawToTypescript(x, environment))
+//       );
+//     case 1: // EvArrayString
+//       return tag("arraystring", result._0);
+//     case 2: // EvBool
+//       return tag("boolean", result._0);
+//     case 3: // EvCall
+//       return tag("call", result._0);
+//     case 4: // EvDistribution
+//       return tag(
+//         "distribution",
+//         new Distribution(
+//           convertRawDistributionToGenericDist(result._0),
+//           environment
+//         )
+//       );
+//     case 5: // EvDistribution
+//       return tag("lambda", result._0);
+//     case 6: // EvNumber
+//       return tag("number", result._0);
+//     case 7: // EvRecord
+//       return tag(
+//         "record",
+//         _.mapValues(result._0, (x) => convertRawToTypescript(x, environment))
+//       );
+//     case 8: // EvString
+//       return tag("string", result._0);
+//     case 9: // EvSymbol
+//       return tag("symbol", result._0);
+//     case 10: // EvDate
+//       return tag("date", result._0);
+//     case 11: // EvTimeDuration
+//       return tag("number", result._0);
+//     case 12: // EvDeclaration
+//       return tag("lambdaDeclaration", {
+//         fn: result._0.fn,
+//         args: result._0.args.map(convertDeclaration),
+//       });
+//     case 13: // EvSymbol
+//       return tag("typeIdentifier", result._0);
+//     case 14: // EvModule
+//       return tag(
+//         "module",
+//         _.mapValues(result._0, (x) => convertRawToTypescript(x, environment))
+//       );
+//   }
+// }
 
-function convertDeclaration(
-  declarationArg: rescriptDeclarationArg
-): declarationArg {
-  switch (declarationArg.TAG) {
-    case 0: // Float
-      return tag("Float", { min: declarationArg.min, max: declarationArg.max });
-    case 1: // Date
-      return tag("Date", { min: declarationArg.min, max: declarationArg.max });
-  }
-}
+// function convertDeclaration(
+//   declarationArg: rescriptDeclarationArg
+// ): declarationArg {
+//   switch (declarationArg.TAG) {
+//     case 0: // Float
+//       return tag("Float", { min: declarationArg.min, max: declarationArg.max });
+//     case 1: // Date
+//       return tag("Date", { min: declarationArg.min, max: declarationArg.max });
+//   }
+// }
 
-function convertRawDistributionToGenericDist(
-  result: rescriptDist
-): genericDist {
-  switch (result.TAG) {
-    case 0: // Point Set Dist
-      switch (result._0.TAG) {
-        case 0: // Mixed
-          return tag("PointSet", tag("Mixed", result._0._0));
-        case 1: // Discrete
-          return tag("PointSet", tag("Discrete", result._0._0));
-        case 2: // Continuous
-          return tag("PointSet", tag("Continuous", result._0._0));
-      }
-    case 1: // Sample Set Dist
-      return tag("SampleSet", result._0);
-    case 2: // Symbolic Dist
-      return tag("Symbolic", result._0);
-  }
-}
+// Umur: opaque type no conversion!
+// function convertRawDistributionToGenericDist(
+//   result: rescriptDist
+// ): genericDist {
+//   switch (result.TAG) {
+//     case 0: // Point Set Dist
+//       switch (result._0.TAG) {
+//         case 0: // Mixed
+//           return tag("PointSet", tag("Mixed", result._0._0));
+//         case 1: // Discrete
+//           return tag("PointSet", tag("Discrete", result._0._0));
+//         case 2: // Continuous
+//           return tag("PointSet", tag("Continuous", result._0._0));
+//       }
+//     case 1: // Sample Set Dist
+//       return tag("SampleSet", result._0);
+//     case 2: // Symbolic Dist
+//       return tag("Symbolic", result._0);
+//   }
+// }
 
-export type jsValue =
-  | string
-  | number
-  | jsValue[]
-  | { [key: string]: jsValue }
-  | boolean;
+// export type jsValue =
+//   | string
+//   | number
+//   | jsValue[]
+//   | { [key: string]: jsValue }
+//   | boolean;
 
-export function jsValueToBinding(value: jsValue): rescriptExport {
-  if (typeof value === "boolean") {
-    return { TAG: 2, _0: value as boolean };
-  } else if (typeof value === "string") {
-    return { TAG: 8, _0: value as string };
-  } else if (typeof value === "number") {
-    return { TAG: 6, _0: value as number };
-  } else if (Array.isArray(value)) {
-    return { TAG: 0, _0: value.map(jsValueToBinding) };
-  } else {
-    // Record
-    return { TAG: 7, _0: _.mapValues(value, jsValueToBinding) };
-  }
-}
+// export function jsValueToBinding(value: jsValue): rescriptExport {
+//   if (typeof value === "boolean") {
+//     return { TAG: 2, _0: value as boolean };
+//   } else if (typeof value === "string") {
+//     return { TAG: 8, _0: value as string };
+//   } else if (typeof value === "number") {
+//     return { TAG: 6, _0: value as number };
+//   } else if (Array.isArray(value)) {
+//     return { TAG: 0, _0: value.map(jsValueToBinding) };
+//   } else {
+//     // Record
+//     return { TAG: 7, _0: _.mapValues(value, jsValueToBinding) };
+//   }
+// }
 
-export function jsValueToExpressionValue(value: jsValue): expressionValue {
-  if (typeof value === "boolean") {
-    return { tag: "EvBool", value: value as boolean };
-  } else if (typeof value === "string") {
-    return { tag: "EvString", value: value as string };
-  } else if (typeof value === "number") {
-    return { tag: "EvNumber", value: value as number };
-  } else if (Array.isArray(value)) {
-    return { tag: "EvArray", value: value.map(jsValueToExpressionValue) };
-  } else {
-    // Record
-    return {
-      tag: "EvRecord",
-      value: _.mapValues(value, jsValueToExpressionValue),
-    };
-  }
-}
+// export function jsValueToExpressionValue(value: jsValue): expressionValue {
+//   if (typeof value === "boolean") {
+//     return { tag: "EvBool", value: value as boolean };
+//   } else if (typeof value === "string") {
+//     return { tag: "EvString", value: value as string };
+//   } else if (typeof value === "number") {
+//     return { tag: "EvNumber", value: value as number };
+//   } else if (Array.isArray(value)) {
+//     return { tag: "EvArray", value: value.map(jsValueToExpressionValue) };
+//   } else {
+//     // Record
+//     return {
+//       tag: "EvRecord",
+//       value: _.mapValues(value, jsValueToExpressionValue),
+//     };
+//   }
+// }
diff --git a/packages/squiggle-lang/src/rescript/Distributions/DistributionTypes.res b/packages/squiggle-lang/src/rescript/Distributions/DistributionTypes.res
index 0c119ea4..93f934e1 100644
--- a/packages/squiggle-lang/src/rescript/Distributions/DistributionTypes.res
+++ b/packages/squiggle-lang/src/rescript/Distributions/DistributionTypes.res
@@ -1,4 +1,5 @@
-@genType
+//FIXME accessor methods or not opaque?
+@genType.opaque
 type genericDist =
   | PointSet(PointSetTypes.pointSetDist)
   | SampleSet(SampleSetDist.t)
@@ -6,7 +7,7 @@ type genericDist =
 
 type asAlgebraicCombinationStrategy = AsDefault | AsSymbolic | AsMonteCarlo | AsConvolution
 
-@genType
+@genType.opaque
 type error =
   | NotYetImplemented
   | Unreachable
@@ -27,7 +28,6 @@ module Error = {
 
   let fromString = (s: string): t => OtherError(s)
 
-  @genType
   let toString = (err: error): string =>
     switch err {
     | NotYetImplemented => "Function not yet implemented"
diff --git a/packages/squiggle-lang/src/rescript/Distributions/GenericDist.res b/packages/squiggle-lang/src/rescript/Distributions/GenericDist.res
index f536d54d..c2bdd299 100644
--- a/packages/squiggle-lang/src/rescript/Distributions/GenericDist.res
+++ b/packages/squiggle-lang/src/rescript/Distributions/GenericDist.res
@@ -1,4 +1,5 @@
 //TODO: multimodal, add interface, test somehow, track performance, refactor sampleSet, refactor ASTEvaluator.res.
+
 type t = DistributionTypes.genericDist
 type error = DistributionTypes.error
 type toPointSetFn = t => result<PointSetTypes.pointSetDist, error>
diff --git a/packages/squiggle-lang/src/rescript/Distributions/PointSetDist/PointSetTypes.res b/packages/squiggle-lang/src/rescript/Distributions/PointSetDist/PointSetTypes.res
index fcc796ec..76720290 100644
--- a/packages/squiggle-lang/src/rescript/Distributions/PointSetDist/PointSetTypes.res
+++ b/packages/squiggle-lang/src/rescript/Distributions/PointSetDist/PointSetTypes.res
@@ -47,7 +47,7 @@ type pointSetDistMonad<'a, 'b, 'c> =
   | Discrete('b)
   | Continuous('c)
 
-@genType
+@genType.opaque
 type pointSetDist = pointSetDistMonad<mixedShape, discreteShape, continuousShape>
 
 module ShapeMonad = {
diff --git a/packages/squiggle-lang/src/rescript/ForTS/ForTS_Distribution/ForTS_Distribution.res b/packages/squiggle-lang/src/rescript/ForTS/ForTS_Distribution/ForTS_Distribution.res
new file mode 100644
index 00000000..ca4c02ad
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ForTS/ForTS_Distribution/ForTS_Distribution.res
@@ -0,0 +1,57 @@
+// Genetic Distribution happens to be abstract distribution
+@genType type distribution = DistributionTypes.genericDist
+@genType type pointSetDistribution = ForTS_Distribution_PointSetDistribution.pointSetDistribution
+@genType type sampleSetDistribution = ForTS_Distribution_SampleSetDistribution.sampleSetDistribution
+@genType type symbolicDistribution = ForTS_Distribution_SymbolicDistribution.symbolicDistribution
+
+type environment = ForTS_Distribution_Environment.environment //use
+
+@genType
+let defaultEnvironment: environment = DistributionOperation.defaultEnv
+
+@module("ForTS_Distribution_tag") @scope("distributionTag")
+external dtPointSet_: int = "DtPointSet"
+
+@module("ForTS_Distribution_tag") @scope("distributionTag")
+external dtSampleSet_: int = "DtSampleSet"
+
+@module("ForTS_Distribution_tag") @scope("distributionTag")
+external dtSymbolic_: int = "DtSymbolic"
+
+@genType.import("./ForTS_Distribution_tag")
+type distributionTag
+
+external castEnum: int => distributionTag = "%identity"
+
+// type genericDist =
+//   | PointSet(PointSetTypes.pointSetDist)
+//   | SampleSet(SampleSetDist.t)
+//   | Symbolic(SymbolicDistTypes.symbolicDist)
+@genType
+let getTag = (variant: distribution): distributionTag =>
+  switch variant {
+  | PointSet(_) => dtPointSet_->castEnum
+  | SampleSet(_) => dtSampleSet_->castEnum
+  | Symbolic(_) => dtSymbolic_->castEnum
+  }
+
+@genType
+let getPointSet = (variant: distribution): option<pointSetDistribution> =>
+  switch variant {
+  | PointSet(dist) => dist->Some
+  | _ => None
+  }
+
+@genType
+let getSampleSet = (variant: distribution): option<sampleSetDistribution> =>
+  switch variant {
+  | SampleSet(dist) => dist->Some
+  | _ => None
+  }
+
+@genType
+let getSymbolic = (variant: distribution): option<symbolicDistribution> =>
+  switch variant {
+  | Symbolic(dist) => dist->Some
+  | _ => None
+  }
diff --git a/packages/squiggle-lang/src/rescript/ForTS/ForTS_Distribution/ForTS_Distribution_Environment.res b/packages/squiggle-lang/src/rescript/ForTS/ForTS_Distribution/ForTS_Distribution_Environment.res
new file mode 100644
index 00000000..d6f89fb9
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ForTS/ForTS_Distribution/ForTS_Distribution_Environment.res
@@ -0,0 +1 @@
+@genType type environment = GenericDist.env //re-export
diff --git a/packages/squiggle-lang/src/rescript/ForTS/ForTS_Distribution/ForTS_Distribution_Error.res b/packages/squiggle-lang/src/rescript/ForTS/ForTS_Distribution/ForTS_Distribution_Error.res
new file mode 100644
index 00000000..d228e7b2
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ForTS/ForTS_Distribution/ForTS_Distribution_Error.res
@@ -0,0 +1,4 @@
+@genType type distributionError = DistributionTypes.error
+
+@genType
+let toString = (e: distributionError) => DistributionTypes.Error.toString(e)
diff --git a/packages/squiggle-lang/src/rescript/ForTS/ForTS_Distribution/ForTS_Distribution_PointSetDistribution.res b/packages/squiggle-lang/src/rescript/ForTS/ForTS_Distribution/ForTS_Distribution_PointSetDistribution.res
new file mode 100644
index 00000000..59750a15
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ForTS/ForTS_Distribution/ForTS_Distribution_PointSetDistribution.res
@@ -0,0 +1,44 @@
+@genType type pointSetDistribution = PointSetTypes.pointSetDist
+
+@module("ForTS_Distribution_PointSetDistribution_tag") @scope("pointSetDistributionTag")
+external pstMixed_: int = "PstMixed"
+
+@module("ForTS_Distribution_PointSetDistribution_tag") @scope("pointSetDistributionTag")
+external pstDiscrete_: int = "PstDiscrete"
+
+@module("ForTS_Distribution_PointSetDistribution_tag") @scope("pointSetDistributionTag")
+external pstContinuous_: int = "PstContinuous"
+
+@genType.import("./ForTS_Distribution_PointSetDistribution_tag")
+type pointSetDistributionTag
+
+external castEnum: int => pointSetDistributionTag = "%identity"
+
+@genType
+let getTag = (variant: pointSetDistribution): pointSetDistributionTag =>
+  switch variant {
+  | Mixed(_) => pstMixed_->castEnum
+  | Discrete(_) => pstDiscrete_->castEnum
+  | Continuous(_) => pstContinuous_->castEnum
+  }
+
+@genType
+let getMixed = (variant: pointSetDistribution): 'd =>
+  switch variant {
+  | Mixed(mixed) => mixed->Some
+  | _ => None
+  }
+
+@genType
+let getDiscrete = (variant: pointSetDistribution): 'd =>
+  switch variant {
+  | Discrete(discrete) => discrete->Some
+  | _ => None
+  }
+
+@genType
+let getContinues = (variant: pointSetDistribution): 'd =>
+  switch variant {
+  | Continuous(continuous) => continuous->Some
+  | _ => None
+  }
diff --git a/packages/squiggle-lang/src/rescript/ForTS/ForTS_Distribution/ForTS_Distribution_PointSetDistribution_tag.js b/packages/squiggle-lang/src/rescript/ForTS/ForTS_Distribution/ForTS_Distribution_PointSetDistribution_tag.js
new file mode 100644
index 00000000..106c13d2
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ForTS/ForTS_Distribution/ForTS_Distribution_PointSetDistribution_tag.js
@@ -0,0 +1,15 @@
+"use strict";
+exports.__esModule = true;
+exports.pointSetDistributionTag = void 0;
+var pointSetDistributionTag;
+(function (pointSetDistributionTag) {
+  pointSetDistributionTag[(pointSetDistributionTag["PstMixed"] = 0)] =
+    "PstMixed";
+  pointSetDistributionTag[(pointSetDistributionTag["PstDiscrete"] = 1)] =
+    "PstDiscrete";
+  pointSetDistributionTag[(pointSetDistributionTag["PstContinuous"] = 2)] =
+    "PstContinuous";
+})(
+  (pointSetDistributionTag =
+    exports.pointSetDistributionTag || (exports.pointSetDistributionTag = {}))
+);
diff --git a/packages/squiggle-lang/src/rescript/ForTS/ForTS_Distribution/ForTS_Distribution_PointSetDistribution_tag.ts b/packages/squiggle-lang/src/rescript/ForTS/ForTS_Distribution/ForTS_Distribution_PointSetDistribution_tag.ts
new file mode 100644
index 00000000..e1e16d89
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ForTS/ForTS_Distribution/ForTS_Distribution_PointSetDistribution_tag.ts
@@ -0,0 +1,5 @@
+export enum pointSetDistributionTag {
+  PstMixed,
+  PstDiscrete,
+  PstContinuous,
+}
diff --git a/packages/squiggle-lang/src/rescript/ForTS/ForTS_Distribution/ForTS_Distribution_SampleSetDistribution.res b/packages/squiggle-lang/src/rescript/ForTS/ForTS_Distribution/ForTS_Distribution_SampleSetDistribution.res
new file mode 100644
index 00000000..29f0c2aa
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ForTS/ForTS_Distribution/ForTS_Distribution_SampleSetDistribution.res
@@ -0,0 +1 @@
+@genType type sampleSetDistribution = SampleSetDist.t
diff --git a/packages/squiggle-lang/src/rescript/ForTS/ForTS_Distribution/ForTS_Distribution_SymbolicDistribution.res b/packages/squiggle-lang/src/rescript/ForTS/ForTS_Distribution/ForTS_Distribution_SymbolicDistribution.res
new file mode 100644
index 00000000..32e8614b
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ForTS/ForTS_Distribution/ForTS_Distribution_SymbolicDistribution.res
@@ -0,0 +1 @@
+@genType type symbolicDistribution = SymbolicDistTypes.symbolicDist
diff --git a/packages/squiggle-lang/src/rescript/ForTS/ForTS_Distribution/ForTS_Distribution_tag.ts b/packages/squiggle-lang/src/rescript/ForTS/ForTS_Distribution/ForTS_Distribution_tag.ts
new file mode 100644
index 00000000..72466c91
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ForTS/ForTS_Distribution/ForTS_Distribution_tag.ts
@@ -0,0 +1,5 @@
+export enum distributionTag {
+  DtPointSet,
+  DtSampleSet,
+  DtSymbolic,
+}
diff --git a/packages/squiggle-lang/src/rescript/ForTS/ForTS_ReducerProject.res b/packages/squiggle-lang/src/rescript/ForTS/ForTS_ReducerProject.res
new file mode 100644
index 00000000..27302313
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ForTS/ForTS_ReducerProject.res
@@ -0,0 +1,235 @@
+@genType type reducerProject = ReducerProject_T.t //re-export
+
+type reducerErrorValue = ForTS_Reducer_ErrorValue.reducerErrorValue //use
+
+type squiggleValue = ForTS_SquiggleValue.squiggleValue //use
+type squiggleValue_Module = ForTS_SquiggleValue_Module.squiggleValue_Module //use
+
+type environment = ForTS_Distribution_Environment.environment //use
+
+module T = ReducerProject_T
+module Private = ReducerProject.Private
+
+/*
+  PUBLIC FUNCTIONS
+*/
+
+/*
+A project links and runs sources that continue or include each other.
+
+Creates a new project to hold the sources, executables, bindings, and other data. 
+The new project runs the sources according to their topological sorting because of the includes and continues.
+
+Any source can include or continue other sources. "Therefore, the project is a graph data structure."
+The difference between including and continuing is that includes are stated inside the source code while continues are stated in the project.
+
+To run a group of source codes and get results/bindings, the necessary methods are
+- setSource
+- setContinues
+- parseIncludes
+- run or runAll
+- getExternalBindings
+- getExternalResult
+
+A project has a public field tag with a constant value "reducerProject"
+project = {tag: "reducerProject"}
+*/
+@genType
+let createProject = (): reducerProject => Private.createProject()->T.Private.castFromInternalProject
+
+/*
+Answer all the source ids of all the sources in the project.
+*/
+@genType
+let getSourceIds = (project: reducerProject): array<string> =>
+  project->T.Private.castToInternalProject->Private.getSourceIds
+
+/*
+Sets the source for a given source Id.
+*/
+@genType
+let setSource = (project: reducerProject, sourceId: string, value: string): unit =>
+  project->T.Private.castToInternalProject->Private.setSource(sourceId, value)
+
+/*
+Gets the source for a given source id.
+*/
+@genType
+let getSource = (project: reducerProject, sourceId: string): option<string> =>
+  project->T.Private.castToInternalProject->Private.getSource(sourceId)
+
+/*
+Touches the source for a given source id. This and dependent, sources are set to be re-evaluated.
+*/
+@genType
+let touchSource = (project: reducerProject, sourceId: string): unit =>
+  project->T.Private.castToInternalProject->Private.touchSource(sourceId)
+
+/*
+Cleans the compilation artifacts for a given source ID. The results stay untouched, so compilation won't be run again.
+
+Normally, you would never need the compilation artifacts again as the results with the same sources would never change. However, they are needed in case of any debugging reruns
+*/
+@genType
+let clean = (project: reducerProject, sourceId: string): unit =>
+  project->T.Private.castToInternalProject->Private.clean(sourceId)
+
+/*
+Cleans all the compilation artifacts in all of the project
+*/
+@genType
+let cleanAll = (project: reducerProject): unit =>
+  project->T.Private.castToInternalProject->Private.cleanAll
+
+/*
+Cleans results. Compilation stays untouched to be able to re-run the source.
+You would not do this if you were not trying to debug the source code.
+*/
+@genType
+let cleanResults = (project: reducerProject, sourceId: string): unit =>
+  project->T.Private.castToInternalProject->Private.cleanResults(sourceId)
+
+/*
+Cleans all results. Compilations remains untouched to rerun the source.
+*/
+@genType
+let cleanAllResults = (project: reducerProject): unit =>
+  project->T.Private.castToInternalProject->Private.cleanAllResults
+
+/*
+To set the includes one first has to call "parseIncludes". The parsed includes or the parser error is returned.
+*/
+@genType
+let getIncludes = (project: reducerProject, sourceId: string): result<
+  array<string>,
+  reducerErrorValue,
+> => project->T.Private.castToInternalProject->Private.getIncludes(sourceId)
+
+/*
+Answers the source codes after which this source code is continuing
+*/
+@genType
+let getContinues = (project: reducerProject, sourceId: string): array<string> =>
+  project->T.Private.castToInternalProject->Private.getContinues(sourceId)
+
+/*
+ "continues" acts like hidden includes in the source. 
+ It is used to define a continuation that is not visible in the source code. 
+ You can chain source codes on the web interface for example
+*/
+@genType
+let setContinues = (project: reducerProject, sourceId: string, continues: array<string>): unit =>
+  project->T.Private.castToInternalProject->Private.setContinues(sourceId, continues)
+
+/*
+This source depends on the array of sources returned.
+*/
+@genType
+let getDependencies = (project: reducerProject, sourceId: string): array<string> =>
+  project->T.Private.castToInternalProject->Private.getDependencies(sourceId)
+
+/*
+The sources returned are dependent on this
+*/
+@genType
+let getDependents = (project: reducerProject, sourceId: string): array<string> =>
+  project->T.Private.castToInternalProject->Private.getDependents(sourceId)
+
+/*
+Get the run order for the sources in the project.
+*/
+@genType
+let getRunOrder = (project: reducerProject): array<string> =>
+  project->T.Private.castToInternalProject->Private.getRunOrder
+
+/*
+Get the run order to get the results of this specific source
+*/
+@genType
+let getRunOrderFor = (project: reducerProject, sourceId: string) =>
+  project->T.Private.castToInternalProject->Private.getRunOrderFor(sourceId)
+
+/*
+Parse includes so that you can load them before running. 
+Load includes by calling getIncludes which returns the includes that have been parsed. 
+It is your responsibility to load the includes before running.
+*/
+
+@genType
+let parseIncludes = (project: reducerProject, sourceId: string): unit =>
+  project->T.Private.castToInternalProject->Private.parseIncludes(sourceId)
+
+/*
+Parse the source code if it is not done already. 
+Use getRawParse to get the parse tree. 
+You would need this function if you want to see the parse tree without running the source code.
+*/
+@genType
+let rawParse = (project: reducerProject, sourceId: string): unit =>
+  project->T.Private.castToInternalProject->Private.rawParse(sourceId)
+
+/*
+Runs a specific source code if it is not done already. The code is parsed if it is not already done. It runs the dependencies if it is not already done.
+*/
+@genType
+let run = (project: reducerProject, sourceId: string): unit =>
+  project->T.Private.castToInternalProject->Private.run(sourceId)
+
+/*
+Runs all of the sources in a project. Their results and bindings will be available
+*/
+@genType
+let runAll = (project: reducerProject): unit =>
+  project->T.Private.castToInternalProject->Private.runAll
+
+/*
+Get the bindings after running this source file or the project
+*/
+@genType
+let getBindings = (project: reducerProject, sourceId: string): squiggleValue_Module =>
+  project->T.Private.castToInternalProject->Private.getBindings(sourceId)
+
+/*
+Get the result after running this source file or the project
+*/
+@genType
+let getResult = (project: reducerProject, sourceId: string): result<
+  squiggleValue,
+  reducerErrorValue,
+> => project->T.Private.castToInternalProject->Private.getResult(sourceId)
+
+/*
+This is a convenience function to get the result of a single source without creating a project. 
+However, without a project, you cannot handle include directives.
+The source has to be include free
+*/
+@genType
+let evaluate = (sourceCode: string): (
+  result<squiggleValue, reducerErrorValue>,
+  squiggleValue_Module,
+) => Private.evaluate(sourceCode)
+
+@genType
+let setEnvironment = (project: reducerProject, environment: environment): unit =>
+  project->T.Private.castToInternalProject->Private.setEnvironment(environment)
+
+/*
+Foreign function interface is intentionally demolished.
+There is another way to do that: Umur.
+Also there is no more conversion from javascript to squiggle values currently.
+If the conversion to the new project is too difficult, I can add it later.
+*/
+
+// let foreignFunctionInterface = (
+//   lambdaValue: squiggleValue_Lambda,
+//   argArray: array<squiggleValue>,
+//   environment: environment,
+// ): result<squiggleValue, reducerErrorValue> => {
+//   let accessors = ReducerProject_ProjectAccessors_T.identityAccessorsWithEnvironment(environment)
+//   Reducer_Expression_Lambda.foreignFunctionInterface(
+//     lambdaValue,
+//     argArray,
+//     accessors,
+//     Reducer_Expression.reduceExpressionInProject,
+//   )
+// }
diff --git a/packages/squiggle-lang/src/rescript/ForTS/ForTS_Reducer_ErrorValue.res b/packages/squiggle-lang/src/rescript/ForTS/ForTS_Reducer_ErrorValue.res
new file mode 100644
index 00000000..61dc3bac
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ForTS/ForTS_Reducer_ErrorValue.res
@@ -0,0 +1,12 @@
+@genType type reducerErrorValue = Reducer_ErrorValue.errorValue //alias
+@genType type syntaxErrorLocation = Reducer_ErrorValue.syntaxErrorLocation //alias
+
+@genType
+let toString = (e: reducerErrorValue): string => Reducer_ErrorValue.errorToString(e)
+
+@genType
+let getLocation = (e: reducerErrorValue): option<syntaxErrorLocation> =>
+  switch e {
+  | RESyntaxError(_, optionalLocation) => optionalLocation
+  | _ => None
+  }
diff --git a/packages/squiggle-lang/src/rescript/ForTS/ForTS_Result_tag.ts b/packages/squiggle-lang/src/rescript/ForTS/ForTS_Result_tag.ts
new file mode 100644
index 00000000..73da47b3
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ForTS/ForTS_Result_tag.ts
@@ -0,0 +1,9 @@
+export type result<a, b> =
+  | {
+      tag: "Ok";
+      value: a;
+    }
+  | {
+      tag: "Error";
+      value: b;
+    };
diff --git a/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue.res b/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue.res
new file mode 100644
index 00000000..df5510d5
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue.res
@@ -0,0 +1,213 @@
+@genType type squiggleValue = ReducerInterface_InternalExpressionValue.t //re-export
+type reducerErrorValue = ForTS_Reducer_ErrorValue.reducerErrorValue //use
+
+@genType type squiggleValue_Array = ReducerInterface_InternalExpressionValue.squiggleArray //re-export recursive type
+@genType type squiggleValue_Module = ReducerInterface_InternalExpressionValue.nameSpace //re-export recursive type
+@genType type squiggleValue_Record = ReducerInterface_InternalExpressionValue.map //re-export recursive type
+@genType type squiggleValue_Type = ReducerInterface_InternalExpressionValue.map //re-export recursive type
+type squiggleValue_Declaration = ForTS_SquiggleValue_Declaration.squiggleValue_Declaration //use
+type squiggleValue_Distribution = ForTS_SquiggleValue_Distribution.squiggleValue_Distribution //use
+type squiggleValue_Lambda = ForTS_SquiggleValue_Lambda.squiggleValue_Lambda //use
+
+// Return values are kept as they are if they are JavaScript types.
+
+@module("./ForTS_SquiggleValue_tag") @scope("squiggleValueTag")
+external svtArray_: string = "SvtArray"
+
+@module("./ForTS_SquiggleValue_tag") @scope("squiggleValueTag")
+external svtArrayString_: string = "SvtArrayString"
+
+@module("./ForTS_SquiggleValue_tag") @scope("squiggleValueTag")
+external svtBool_: string = "SvtBool"
+
+@module("./ForTS_SquiggleValue_tag") @scope("squiggleValueTag")
+external svtCall_: string = "SvtCall"
+
+@module("./ForTS_SquiggleValue_tag") @scope("squiggleValueTag")
+external svtDate_: string = "SvtDate"
+
+@module("./ForTS_SquiggleValue_tag") @scope("squiggleValueTag")
+external svtDeclaration_: string = "SvtDeclaration"
+
+@module("./ForTS_SquiggleValue_tag") @scope("squiggleValueTag")
+external svtDistribution_: string = "SvtDistribution"
+
+@module("./ForTS_SquiggleValue_tag") @scope("squiggleValueTag")
+external svtLambda_: string = "SvtLambda"
+
+@module("./ForTS_SquiggleValue_tag") @scope("squiggleValueTag")
+external svtModule_: string = "SvtModule"
+
+@module("./ForTS_SquiggleValue_tag") @scope("squiggleValueTag")
+external svtNumber_: string = "SvtNumber"
+
+@module("./ForTS_SquiggleValue_tag") @scope("squiggleValueTag")
+external svtRecord_: string = "SvtRecord"
+
+@module("./ForTS_SquiggleValue_tag") @scope("squiggleValueTag")
+external svtString_: string = "SvtString"
+
+@module("./ForTS_SquiggleValue_tag") @scope("squiggleValueTag")
+external svtSymbol_: string = "SvtSymbol"
+
+@module("./ForTS_SquiggleValue_tag") @scope("squiggleValueTag")
+external svtTimeDuration_: string = "SvtTimeDuration"
+
+@module("./ForTS_SquiggleValue_tag") @scope("squiggleValueTag")
+external svtType_: string = "SvtType"
+
+@module("./ForTS_SquiggleValue_tag") @scope("squiggleValueTag")
+external svtTypeIdentifier_: string = "SvtUndefined"
+
+@module("./ForTS_SquiggleValue_tag") @scope("squiggleValueTag")
+external svtVoid_: string = "SvtVoid"
+
+@genType.import("./ForTS_SquiggleValue_tag")
+type squiggleValueTag
+
+external castEnum: string => squiggleValueTag = "%identity"
+
+@genType
+let getTag = (variant: squiggleValue): squiggleValueTag =>
+  switch variant {
+  | IEvArray(_) => svtArray_->castEnum
+  | IEvArrayString(_) => svtArrayString_->castEnum
+  | IEvBool(_) => svtBool_->castEnum
+  | IEvCall(_) => svtCall_->castEnum //Impossible
+  | IEvDate(_) => svtDate_->castEnum
+  | IEvDeclaration(_) => svtDeclaration_->castEnum
+  | IEvDistribution(_) => svtDistribution_->castEnum
+  | IEvLambda(_) => svtLambda_->castEnum
+  | IEvBindings(_) => svtModule_->castEnum //Impossible
+  | IEvNumber(_) => svtNumber_->castEnum
+  | IEvRecord(_) => svtRecord_->castEnum
+  | IEvString(_) => svtString_->castEnum
+  | IEvSymbol(_) => svtSymbol_->castEnum
+  | IEvTimeDuration(_) => svtTimeDuration_->castEnum
+  | IEvType(_) => svtType_->castEnum
+  | IEvTypeIdentifier(_) => svtTypeIdentifier_->castEnum
+  | IEvVoid => svtVoid_->castEnum
+  }
+
+@genType
+let toString = (variant: squiggleValue) =>
+  ReducerInterface_InternalExpressionValue.toString(variant)
+
+// This is a useful method for unit tests.
+// Convert the result along with the error message to a string.
+@genType
+let toStringResult = (variantResult: result<squiggleValue, reducerErrorValue>) =>
+  ReducerInterface_InternalExpressionValue.toStringResult(variantResult)
+
+@genType
+let getArray = (variant: squiggleValue): option<squiggleValue_Array> =>
+  //FIXME: Convert
+  switch variant {
+  | IEvArray(arrayLike) => arrayLike->Some
+  | _ => None
+  }
+
+@genType
+let getArrayString = (variant: squiggleValue): option<array<string>> =>
+  switch variant {
+  | IEvArrayString(value) => value->Some
+  | _ => None
+  }
+
+@genType
+let getBool = (variant: squiggleValue): option<bool> =>
+  switch variant {
+  | IEvBool(value) => value->Some
+  | _ => None
+  }
+
+@genType
+let getCall = (variant: squiggleValue): option<string> =>
+  switch variant {
+  | IEvCall(value) => value->Some
+  | _ => None
+  }
+
+@genType
+let getDate = (variant: squiggleValue): option<Js.Date.t> =>
+  switch variant {
+  | IEvDate(value) => value->Some
+  | _ => None
+  }
+
+@genType
+let getDeclaration = (variant: squiggleValue): option<squiggleValue_Declaration> =>
+  switch variant {
+  | IEvDeclaration(value) => value->Some
+  | _ => None
+  }
+
+@genType
+let getDistribution = (variant: squiggleValue): option<squiggleValue_Distribution> =>
+  switch variant {
+  | IEvDistribution(value) => value->Some
+  | _ => None
+  }
+
+@genType
+let getLambda = (variant: squiggleValue): option<squiggleValue_Lambda> =>
+  switch variant {
+  | IEvLambda(value) => value->Some
+  | _ => None
+  }
+
+@genType
+let getModule = (variant: squiggleValue): option<squiggleValue_Module> =>
+  switch variant {
+  | IEvBindings(value) => value->Some
+  | _ => None
+  }
+
+@genType
+let getNumber = (variant: squiggleValue): option<float> =>
+  switch variant {
+  | IEvNumber(value) => value->Some
+  | _ => None
+  }
+
+@genType
+let getRecord = (variant: squiggleValue): option<squiggleValue_Record> =>
+  switch variant {
+  | IEvRecord(value) => value->Some
+  | _ => None
+  }
+
+@genType
+let getString = (variant: squiggleValue): option<string> =>
+  switch variant {
+  | IEvString(value) => value->Some
+  | _ => None
+  }
+
+@genType
+let getSymbol = (variant: squiggleValue): option<string> =>
+  switch variant {
+  | IEvSymbol(value) => value->Some
+  | _ => None
+  }
+
+@genType
+let getTimeDuration = (variant: squiggleValue): option<float> =>
+  switch variant {
+  | IEvTimeDuration(value) => value->Some
+  | _ => None
+  }
+
+@genType
+let getType = (variant: squiggleValue): option<squiggleValue_Type> =>
+  switch variant {
+  | IEvType(value) => value->Some
+  | _ => None
+  }
+
+@genType
+let getTypeIdentifier = (variant: squiggleValue): option<string> =>
+  switch variant {
+  | IEvTypeIdentifier(value) => value->Some
+  | _ => None
+  }
diff --git a/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue_Array.res b/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue_Array.res
new file mode 100644
index 00000000..61b84d74
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue_Array.res
@@ -0,0 +1,6 @@
+type squiggleValue = ForTS_SquiggleValue.squiggleValue
+@genType type squiggleValue_Array = ForTS_SquiggleValue.squiggleValue_Array //re-export recursive type
+
+@genType
+let getValues = (v: squiggleValue_Array): array<squiggleValue> =>
+  ReducerInterface_InternalExpressionValue.arrayToValueArray(v)
diff --git a/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue_Declaration.res b/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue_Declaration.res
new file mode 100644
index 00000000..b53fb4bf
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue_Declaration.res
@@ -0,0 +1 @@
+@genType type squiggleValue_Declaration = ReducerInterface_InternalExpressionValue.lambdaDeclaration //re-export
diff --git a/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue_Distribution.res b/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue_Distribution.res
new file mode 100644
index 00000000..ef20d02f
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue_Distribution.res
@@ -0,0 +1 @@
+@genType type squiggleValue_Distribution = ForTS_Distribution.distribution
diff --git a/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue_Lambda.res b/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue_Lambda.res
new file mode 100644
index 00000000..c41a5727
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue_Lambda.res
@@ -0,0 +1 @@
+@genType type squiggleValue_Lambda = ReducerInterface_InternalExpressionValue.lambdaValue //re-export
diff --git a/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue_Module.res b/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue_Module.res
new file mode 100644
index 00000000..8bb113a2
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue_Module.res
@@ -0,0 +1,6 @@
+type squiggleValue = ForTS_SquiggleValue.squiggleValue //use
+@genType type squiggleValue_Module = ForTS_SquiggleValue.squiggleValue_Module //re-export recursive type
+
+@genType
+let getKeyValuePairs = (v: squiggleValue_Module): array<(string, squiggleValue)> =>
+  ReducerInterface_InternalExpressionValue.nameSpaceToKeyValuePairs(v)
diff --git a/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue_Record.res b/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue_Record.res
new file mode 100644
index 00000000..bc226f95
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue_Record.res
@@ -0,0 +1,6 @@
+type squiggleValue = ForTS_SquiggleValue.squiggleValue //use
+@genType type squiggleValue_Record = ForTS_SquiggleValue.squiggleValue_Record //re-export recursive type
+
+@genType
+let getKeyValuePairs = (value: squiggleValue_Record): array<(string, squiggleValue)> =>
+  ReducerInterface_InternalExpressionValue.recordToKeyValuePairs(value)
diff --git a/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue_Type.res b/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue_Type.res
new file mode 100644
index 00000000..d9a18bfc
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue_Type.res
@@ -0,0 +1,6 @@
+type squiggleValue = ForTS_SquiggleValue.squiggleValue //use
+@genType type squiggleValue_Type = ForTS_SquiggleValue.squiggleValue_Type //re-export recursive type
+
+@genType
+let getKeyValuePairs = (value: squiggleValue_Type): array<(string, squiggleValue)> =>
+  ReducerInterface_InternalExpressionValue.recordToKeyValuePairs(value)
diff --git a/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue_tag.ts b/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue_tag.ts
new file mode 100644
index 00000000..f8b4a9e3
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue_tag.ts
@@ -0,0 +1,19 @@
+export enum squiggleValueTag {
+  SvtArray = "Array",
+  SvtArrayString = "ArrayString",
+  SvtBool = "Bool",
+  SvtCall = "Call",
+  SvtDate = "Date",
+  SvtDeclaration = "Declaration",
+  SvtDistribution = "Distribution",
+  SvtLambda = "Lambda",
+  SvtModule = "Module",
+  SvtNumber = "Number",
+  SvtRecord = "Record",
+  SvtString = "String",
+  SvtSymbol = "Symbol",
+  SvtTimeDuration = "TimeDuration",
+  SvtType = "Type",
+  SvtTypeIdentifier = "TypeIdentifier",
+  SvtVoid = "Void",
+}
diff --git a/packages/squiggle-lang/src/rescript/ForTS/ForTS__Types.res b/packages/squiggle-lang/src/rescript/ForTS/ForTS__Types.res
new file mode 100644
index 00000000..b97c93e0
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ForTS/ForTS__Types.res
@@ -0,0 +1,21 @@
+@genType type reducerErrorValue = ForTS_Reducer_ErrorValue.reducerErrorValue //re-export
+@genType type syntaxErrorLocation = ForTS_Reducer_ErrorValue.syntaxErrorLocation //re-export
+
+@genType type reducerProject = ForTS_ReducerProject.reducerProject //re-export
+@genType type squiggleValue = ForTS_SquiggleValue.squiggleValue //re-export
+@genType type squiggleValue_Array = ForTS_SquiggleValue_Array.squiggleValue_Array //re-export
+@genType type squiggleValue_Declaration = ForTS_SquiggleValue_Declaration.squiggleValue_Declaration //re-export
+@genType type squiggleValue_Lambda = ForTS_SquiggleValue_Lambda.squiggleValue_Lambda //re-export
+@genType type squiggleValue_Module = ForTS_SquiggleValue_Module.squiggleValue_Module //re-export
+@genType type squiggleValue_Record = ForTS_SquiggleValue_Record.squiggleValue_Record //re-export
+@genType type squiggleValue_Type = ForTS_SquiggleValue_Type.squiggleValue_Type //re-export
+
+/* Distribution related */
+@genType type squiggleValue_Distribution = ForTS_Distribution.distribution //re-export
+@genType type distribution = squiggleValue_Distribution //candid
+@genType type distributionError = ForTS_Distribution_Error.distributionError //re-export
+@genType type environment = ForTS_Distribution_Environment.environment //re-export
+
+@genType type pointSetDistribution = ForTS_Distribution_PointSetDistribution.pointSetDistribution //re-export
+@genType type sampleSetDistribution = ForTS_Distribution_SampleSetDistribution.sampleSetDistribution //re-export
+@genType type symbolicDistribution = ForTS_Distribution_SymbolicDistribution.symbolicDistribution //re-export
diff --git a/packages/squiggle-lang/src/rescript/FunctionRegistry/FunctionRegistry_Core.res b/packages/squiggle-lang/src/rescript/FunctionRegistry/FunctionRegistry_Core.res
index 4b27c221..edce5ac2 100644
--- a/packages/squiggle-lang/src/rescript/FunctionRegistry/FunctionRegistry_Core.res
+++ b/packages/squiggle-lang/src/rescript/FunctionRegistry/FunctionRegistry_Core.res
@@ -1,3 +1,5 @@
+module ProjectAccessorsT = ReducerProject_ProjectAccessors_T
+module ProjectReducerFnT = ReducerProject_ReducerFn_T
 type internalExpressionValue = ReducerInterface_InternalExpressionValue.t
 type internalExpressionValueType = ReducerInterface_InternalExpressionValue.internalExpressionValueType
 
@@ -46,8 +48,8 @@ type fnDefinition = {
   run: (
     array<internalExpressionValue>,
     array<frValue>,
-    GenericDist.env,
-    Reducer_Expression_T.reducerFn,
+    ProjectAccessorsT.t,
+    ProjectReducerFnT.t,
   ) => result<internalExpressionValue, string>,
 }
 
@@ -382,12 +384,12 @@ module FnDefinition = {
   let run = (
     t: t,
     args: array<internalExpressionValue>,
-    env: GenericDist.env,
-    reducer: Reducer_Expression_T.reducerFn,
+    accessors: ProjectAccessorsT.t,
+    reducer: ProjectReducerFnT.t,
   ) => {
     let argValues = FRType.matchWithExpressionValueArray(t.inputs, args)
     switch argValues {
-    | Some(values) => t.run(args, values, env, reducer)
+    | Some(values) => t.run(args, values, accessors, reducer)
     | None => Error("Incorrect Types")
     }
   }
@@ -493,8 +495,8 @@ module Registry = {
     ~registry: registry,
     ~fnName: string,
     ~args: array<internalExpressionValue>,
-    ~env: GenericDist.env,
-    ~reducer: Reducer_Expression_T.reducerFn,
+    ~accessors: ProjectAccessorsT.t,
+    ~reducer: ProjectReducerFnT.t,
   ) => {
     let relevantFunctions = Js.Dict.get(registry.fnNameDict, fnName) |> E.O.default([])
     let modified = {functions: relevantFunctions, fnNameDict: registry.fnNameDict}
@@ -512,7 +514,7 @@ module Registry = {
 
     switch Matcher.Registry.findMatches(modified, fnName, args) {
     | Matcher.Match.FullMatch(match) =>
-      match->matchToDef->E.O2.fmap(FnDefinition.run(_, args, env, reducer))
+      match->matchToDef->E.O2.fmap(FnDefinition.run(_, args, accessors, reducer))
     | SameNameDifferentArguments(m) => Some(Error(showNameMatchDefinitions(m)))
     | _ => None
     }
@@ -521,10 +523,10 @@ module Registry = {
   let dispatch = (
     registry,
     (fnName, args): ReducerInterface_InternalExpressionValue.functionCall,
-    env,
-    reducer: Reducer_Expression_T.reducerFn,
+    accessors: ProjectAccessorsT.t,
+    reducer: ProjectReducerFnT.t,
   ) => {
-    _matchAndRun(~registry, ~fnName, ~args, ~env, ~reducer)->E.O2.fmap(
+    _matchAndRun(~registry, ~fnName, ~args, ~accessors, ~reducer)->E.O2.fmap(
       E.R2.errMap(_, s => Reducer_ErrorValue.RETodo(s)),
     )
   }
diff --git a/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_Dist.res b/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_Dist.res
index 9e10577b..23619187 100644
--- a/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_Dist.res
+++ b/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_Dist.res
@@ -21,8 +21,8 @@ module DistributionCreation = {
       FnDefinition.make(
         ~name,
         ~inputs=[FRTypeDistOrNumber, FRTypeDistOrNumber],
-        ~run=(_, inputs, env, _) =>
-          inputs->Prepare.ToValueTuple.twoDistOrNumber->process(~fn, ~env),
+        ~run=(_, inputs, accessors, _) =>
+          inputs->Prepare.ToValueTuple.twoDistOrNumber->process(~fn, ~env=accessors.environment),
         (),
       )
     }
@@ -31,8 +31,10 @@ module DistributionCreation = {
       FnDefinition.make(
         ~name,
         ~inputs=[FRTypeRecord([("p5", FRTypeDistOrNumber), ("p95", FRTypeDistOrNumber)])],
-        ~run=(_, inputs, env, _) =>
-          inputs->Prepare.ToValueTuple.Record.twoDistOrNumber->process(~fn, ~env),
+        ~run=(_, inputs, accessors, _) =>
+          inputs
+          ->Prepare.ToValueTuple.Record.twoDistOrNumber
+          ->process(~fn, ~env=accessors.environment),
         (),
       )
     }
@@ -41,8 +43,10 @@ module DistributionCreation = {
       FnDefinition.make(
         ~name,
         ~inputs=[FRTypeRecord([("mean", FRTypeDistOrNumber), ("stdev", FRTypeDistOrNumber)])],
-        ~run=(_, inputs, env, _) =>
-          inputs->Prepare.ToValueTuple.Record.twoDistOrNumber->process(~fn, ~env),
+        ~run=(_, inputs, accessors, _) =>
+          inputs
+          ->Prepare.ToValueTuple.Record.twoDistOrNumber
+          ->process(~fn, ~env=accessors.environment),
         (),
       )
     }
@@ -58,8 +62,8 @@ module DistributionCreation = {
       FnDefinition.make(
         ~name,
         ~inputs=[FRTypeDistOrNumber],
-        ~run=(_, inputs, env, _) =>
-          inputs->Prepare.ToValueTuple.oneDistOrNumber->process(~fn, ~env),
+        ~run=(_, inputs, accessors, _) =>
+          inputs->Prepare.ToValueTuple.oneDistOrNumber->process(~fn, ~env=accessors.environment),
         (),
       )
   }
diff --git a/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_List.res b/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_List.res
index 762fe31b..e0b83d18 100644
--- a/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_List.res
+++ b/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_List.res
@@ -1,3 +1,6 @@
+// module ProjectAccessorsT = ReducerProject_ProjectAccessors_T
+// module ProjectReducerFnT = ReducerProject_ReducerFn_T
+
 open FunctionRegistry_Core
 open FunctionRegistry_Helpers
 
@@ -24,17 +27,19 @@ module Internals = {
     Belt.Array.reverse(array),
   )
 
-  let map = (array: array<internalExpressionValue>, environment, eLambdaValue, reducer): result<
-    ReducerInterface_InternalExpressionValue.t,
-    Reducer_ErrorValue.errorValue,
-  > => {
+  let map = (
+    array: array<internalExpressionValue>,
+    accessors: ProjectAccessorsT.t,
+    eLambdaValue,
+    reducer: ProjectReducerFnT.t,
+  ): result<ReducerInterface_InternalExpressionValue.t, Reducer_ErrorValue.errorValue> => {
     let rMappedList = array->E.A.reduceReverse(Ok(list{}), (rAcc, elem) =>
       rAcc->E.R.bind(_, acc => {
         let rNewElem = Reducer_Expression_Lambda.doLambdaCall(
           eLambdaValue,
           list{elem},
-          environment,
-          reducer,
+          (accessors: ProjectAccessorsT.t),
+          (reducer: ProjectReducerFnT.t),
         )
         rNewElem->E.R2.fmap(newElem => list{newElem, ...acc})
       })
@@ -42,29 +47,46 @@ module Internals = {
     rMappedList->E.R2.fmap(mappedList => mappedList->Belt.List.toArray->Wrappers.evArray)
   }
 
-  let reduce = (aValueArray, initialValue, aLambdaValue, environment, reducer) => {
+  let reduce = (
+    aValueArray,
+    initialValue,
+    aLambdaValue,
+    accessors: ProjectAccessorsT.t,
+    reducer: ProjectReducerFnT.t,
+  ) => {
     aValueArray->E.A.reduce(Ok(initialValue), (rAcc, elem) =>
       rAcc->E.R.bind(_, acc =>
-        Reducer_Expression_Lambda.doLambdaCall(aLambdaValue, list{acc, elem}, environment, reducer)
+        Reducer_Expression_Lambda.doLambdaCall(aLambdaValue, list{acc, elem}, accessors, reducer)
       )
     )
   }
 
-  let reduceReverse = (aValueArray, initialValue, aLambdaValue, environment, reducer) => {
+  let reduceReverse = (
+    aValueArray,
+    initialValue,
+    aLambdaValue,
+    accessors: ProjectAccessorsT.t,
+    reducer: ProjectReducerFnT.t,
+  ) => {
     aValueArray->Belt.Array.reduceReverse(Ok(initialValue), (rAcc, elem) =>
       rAcc->Belt.Result.flatMap(acc =>
-        Reducer_Expression_Lambda.doLambdaCall(aLambdaValue, list{acc, elem}, environment, reducer)
+        Reducer_Expression_Lambda.doLambdaCall(aLambdaValue, list{acc, elem}, accessors, reducer)
       )
     )
   }
 
-  let filter = (aValueArray, aLambdaValue, environment, reducer) => {
+  let filter = (
+    aValueArray,
+    aLambdaValue,
+    accessors: ProjectAccessorsT.t,
+    reducer: ProjectReducerFnT.t,
+  ) => {
     let rMappedList = aValueArray->Belt.Array.reduceReverse(Ok(list{}), (rAcc, elem) =>
       rAcc->E.R.bind(_, acc => {
         let rNewElem = Reducer_Expression_Lambda.doLambdaCall(
           aLambdaValue,
           list{elem},
-          environment,
+          accessors,
           reducer,
         )
         rNewElem->E.R2.fmap(newElem => {
@@ -189,10 +211,10 @@ let library = [
       FnDefinition.make(
         ~name="map",
         ~inputs=[FRTypeArray(FRTypeAny), FRTypeLambda],
-        ~run=(inputs, _, env, reducer) =>
+        ~run=(inputs, _, accessors: ProjectAccessorsT.t, reducer) =>
           switch inputs {
           | [IEvArray(array), IEvLambda(lambda)] =>
-            Internals.map(array, env, lambda, reducer)->E.R2.errMap(_ => "Error!")
+            Internals.map(array, accessors, lambda, reducer)->E.R2.errMap(_ => "Error!")
           | _ => Error(impossibleError)
           },
         (),
@@ -209,10 +231,12 @@ let library = [
       FnDefinition.make(
         ~name="reduce",
         ~inputs=[FRTypeArray(FRTypeAny), FRTypeAny, FRTypeLambda],
-        ~run=(inputs, _, env, reducer) =>
+        ~run=(inputs, _, accessors: ProjectAccessorsT.t, reducer) =>
           switch inputs {
           | [IEvArray(array), initialValue, IEvLambda(lambda)] =>
-            Internals.reduce(array, initialValue, lambda, env, reducer)->E.R2.errMap(_ => "Error!")
+            Internals.reduce(array, initialValue, lambda, accessors, reducer)->E.R2.errMap(_ =>
+              "Error!"
+            )
           | _ => Error(impossibleError)
           },
         (),
@@ -229,12 +253,16 @@ let library = [
       FnDefinition.make(
         ~name="reduceReverse",
         ~inputs=[FRTypeArray(FRTypeAny), FRTypeAny, FRTypeLambda],
-        ~run=(inputs, _, env, reducer) =>
+        ~run=(inputs, _, accessors: ProjectAccessorsT.t, reducer: ProjectReducerFnT.t) =>
           switch inputs {
           | [IEvArray(array), initialValue, IEvLambda(lambda)] =>
-            Internals.reduceReverse(array, initialValue, lambda, env, reducer)->E.R2.errMap(_ =>
-              "Error!"
-            )
+            Internals.reduceReverse(
+              array,
+              initialValue,
+              lambda,
+              accessors,
+              reducer,
+            )->E.R2.errMap(_ => "Error!")
           | _ => Error(impossibleError)
           },
         (),
@@ -251,10 +279,10 @@ let library = [
       FnDefinition.make(
         ~name="filter",
         ~inputs=[FRTypeArray(FRTypeAny), FRTypeLambda],
-        ~run=(inputs, _, env, reducer) =>
+        ~run=(inputs, _, accessors: ProjectAccessorsT.t, reducer: ProjectReducerFnT.t) =>
           switch inputs {
           | [IEvArray(array), IEvLambda(lambda)] =>
-            Internals.filter(array, lambda, env, reducer)->E.R2.errMap(_ => "Error!")
+            Internals.filter(array, lambda, accessors, reducer)->E.R2.errMap(_ => "Error!")
           | _ => Error(impossibleError)
           },
         (),
diff --git a/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_Pointset.res b/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_Pointset.res
index 44b6abd2..0d950ce5 100644
--- a/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_Pointset.res
+++ b/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_Pointset.res
@@ -58,13 +58,13 @@ let library = [
       FnDefinition.make(
         ~name="fromDist",
         ~inputs=[FRTypeDist],
-        ~run=(_, inputs, env, _) =>
+        ~run=(_, inputs, accessors, _) =>
           switch inputs {
           | [FRValueDist(dist)] =>
             GenericDist.toPointSet(
               dist,
-              ~xyPointLength=env.xyPointLength,
-              ~sampleCount=env.sampleCount,
+              ~xyPointLength=accessors.environment.xyPointLength,
+              ~sampleCount=accessors.environment.sampleCount,
               (),
             )
             ->E.R2.fmap(Wrappers.pointSet)
diff --git a/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_Sampleset.res b/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_Sampleset.res
index c40fe349..016383f5 100644
--- a/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_Sampleset.res
+++ b/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_Sampleset.res
@@ -1,3 +1,5 @@
+// module ProjectAccessorsT = ReducerProject_ProjectAccessors_T
+// module ProjectReducerFnT = ReducerProject_ReducerFn_T
 open FunctionRegistry_Core
 open FunctionRegistry_Helpers
 
@@ -6,8 +8,14 @@ let requiresNamespace = true
 
 module Internal = {
   type t = SampleSetDist.t
-  let doLambdaCall = (aLambdaValue, list, environment, reducer) =>
-    switch Reducer_Expression_Lambda.doLambdaCall(aLambdaValue, list, environment, reducer) {
+
+  let doLambdaCall = (
+    aLambdaValue,
+    list,
+    accessors: ProjectAccessorsT.t,
+    reducer: ProjectReducerFnT.t,
+  ) =>
+    switch Reducer_Expression_Lambda.doLambdaCall(aLambdaValue, list, accessors, reducer) {
     | Ok(IEvNumber(f)) => Ok(f)
     | _ => Error(Operation.SampleMapNeedsNtoNFunction)
     }
@@ -22,29 +30,26 @@ module Internal = {
     }
 
   //TODO: I don't know why this seems to need at least one input
-  let fromFn = (
-    aLambdaValue,
-    env: ReducerInterface_InternalExpressionValue.environment,
-    reducer,
-  ) => {
-    let sampleCount = env.sampleCount
-    let fn = r => doLambdaCall(aLambdaValue, list{IEvNumber(r)}, env, reducer)
+  let fromFn = (aLambdaValue, accessors: ProjectAccessorsT.t, reducer: ProjectReducerFnT.t) => {
+    let sampleCount = accessors.environment.sampleCount
+    let fn = r => doLambdaCall(aLambdaValue, list{IEvNumber(r)}, accessors, reducer)
     Belt_Array.makeBy(sampleCount, r => fn(r->Js.Int.toFloat))->E.A.R.firstErrorOrOpen
   }
 
-  let map1 = (sampleSetDist: t, aLambdaValue, env, reducer) => {
-    let fn = r => doLambdaCall(aLambdaValue, list{IEvNumber(r)}, env, reducer)
+  let map1 = (sampleSetDist: t, aLambdaValue, accessors: ProjectAccessorsT.t, reducer) => {
+    let fn = r => doLambdaCall(aLambdaValue, list{IEvNumber(r)}, accessors, reducer)
     SampleSetDist.samplesMap(~fn, sampleSetDist)->toType
   }
 
-  let map2 = (t1: t, t2: t, aLambdaValue, env, reducer) => {
-    let fn = (a, b) => doLambdaCall(aLambdaValue, list{IEvNumber(a), IEvNumber(b)}, env, reducer)
+  let map2 = (t1: t, t2: t, aLambdaValue, accessors: ProjectAccessorsT.t, reducer) => {
+    let fn = (a, b) =>
+      doLambdaCall(aLambdaValue, list{IEvNumber(a), IEvNumber(b)}, accessors, reducer)
     SampleSetDist.map2(~fn, ~t1, ~t2)->toType
   }
 
-  let map3 = (t1: t, t2: t, t3: t, aLambdaValue, env, reducer) => {
+  let map3 = (t1: t, t2: t, t3: t, aLambdaValue, accessors: ProjectAccessorsT.t, reducer) => {
     let fn = (a, b, c) =>
-      doLambdaCall(aLambdaValue, list{IEvNumber(a), IEvNumber(b), IEvNumber(c)}, env, reducer)
+      doLambdaCall(aLambdaValue, list{IEvNumber(a), IEvNumber(b), IEvNumber(c)}, accessors, reducer)
     SampleSetDist.map3(~fn, ~t1, ~t2, ~t3)->toType
   }
 
@@ -59,14 +64,19 @@ module Internal = {
     E.A.O.openIfAllSome(E.A.fmap(parseSampleSet, arr))
   }
 
-  let mapN = (aValueArray: array<internalExpressionValue>, aLambdaValue, env, reducer) => {
+  let mapN = (
+    aValueArray: array<internalExpressionValue>,
+    aLambdaValue,
+    accessors: ProjectAccessorsT.t,
+    reducer,
+  ) => {
     switch parseSampleSetArray(aValueArray) {
     | Some(t1) =>
       let fn = a =>
         doLambdaCall(
           aLambdaValue,
           list{IEvArray(E.A.fmap(x => Wrappers.evNumber(x), a))},
-          env,
+          accessors,
           reducer,
         )
       SampleSetDist.mapN(~fn, ~t1)->toType
@@ -86,10 +96,10 @@ let library = [
       FnDefinition.make(
         ~name="fromDist",
         ~inputs=[FRTypeDist],
-        ~run=(_, inputs, env, _) =>
+        ~run=(_, inputs, accessors: ProjectAccessorsT.t, _) =>
           switch inputs {
           | [FRValueDist(dist)] =>
-            GenericDist.toSampleSetDist(dist, env.sampleCount)
+            GenericDist.toSampleSetDist(dist, accessors.environment.sampleCount)
             ->E.R2.fmap(Wrappers.sampleSet)
             ->E.R2.fmap(Wrappers.evDistribution)
             ->E.R2.errMap(DistributionTypes.Error.toString)
@@ -153,10 +163,10 @@ let library = [
       FnDefinition.make(
         ~name="fromFn",
         ~inputs=[FRTypeLambda],
-        ~run=(inputs, _, env, reducer) =>
+        ~run=(inputs, _, accessors: ProjectAccessorsT.t, reducer: ProjectReducerFnT.t) =>
           switch inputs {
           | [IEvLambda(lambda)] =>
-            switch Internal.fromFn(lambda, env, reducer) {
+            switch Internal.fromFn(lambda, accessors, reducer) {
             | Ok(r) => Ok(r->Wrappers.sampleSet->Wrappers.evDistribution)
             | Error(e) => Error(Operation.Error.toString(e))
             }
@@ -177,10 +187,10 @@ let library = [
       FnDefinition.make(
         ~name="map",
         ~inputs=[FRTypeDist, FRTypeLambda],
-        ~run=(inputs, _, env, reducer) =>
+        ~run=(inputs, _, accessors: ProjectAccessorsT.t, reducer) =>
           switch inputs {
           | [IEvDistribution(SampleSet(dist)), IEvLambda(lambda)] =>
-            Internal.map1(dist, lambda, env, reducer)->E.R2.errMap(Reducer_ErrorValue.errorToString)
+            Internal.map1(dist, lambda, accessors, reducer)->E.R2.errMap(_ => "")
           | _ => Error(impossibleError)
           },
         (),
@@ -200,16 +210,14 @@ let library = [
       FnDefinition.make(
         ~name="map2",
         ~inputs=[FRTypeDist, FRTypeDist, FRTypeLambda],
-        ~run=(inputs, _, env, reducer) => {
+        ~run=(inputs, _, accessors: ProjectAccessorsT.t, reducer) => {
           switch inputs {
           | [
               IEvDistribution(SampleSet(dist1)),
               IEvDistribution(SampleSet(dist2)),
               IEvLambda(lambda),
             ] =>
-            Internal.map2(dist1, dist2, lambda, env, reducer)->E.R2.errMap(
-              Reducer_ErrorValue.errorToString,
-            )
+            Internal.map2(dist1, dist2, lambda, accessors, reducer)->E.R2.errMap(_ => "")
           | _ => Error(impossibleError)
           }
         },
@@ -230,7 +238,7 @@ let library = [
       FnDefinition.make(
         ~name="map3",
         ~inputs=[FRTypeDist, FRTypeDist, FRTypeDist, FRTypeLambda],
-        ~run=(inputs, _, env, reducer) =>
+        ~run=(inputs, _, accessors: ProjectAccessorsT.t, reducer) =>
           switch inputs {
           | [
               IEvDistribution(SampleSet(dist1)),
@@ -238,9 +246,7 @@ let library = [
               IEvDistribution(SampleSet(dist3)),
               IEvLambda(lambda),
             ] =>
-            Internal.map3(dist1, dist2, dist3, lambda, env, reducer)->E.R2.errMap(
-              Reducer_ErrorValue.errorToString,
-            )
+            Internal.map3(dist1, dist2, dist3, lambda, accessors, reducer)->E.R2.errMap(_ => "")
           | _ => Error(impossibleError)
           },
         (),
@@ -260,12 +266,12 @@ let library = [
       FnDefinition.make(
         ~name="mapN",
         ~inputs=[FRTypeArray(FRTypeDist), FRTypeLambda],
-        ~run=(inputs, _, env, reducer) =>
+        ~run=(inputs, _, accessors: ProjectAccessorsT.t, reducer) =>
           switch inputs {
           | [IEvArray(dists), IEvLambda(lambda)] =>
-            Internal.mapN(dists, lambda, env, reducer)->E.R2.errMap(
-              Reducer_ErrorValue.errorToString,
-            )
+            Internal.mapN(dists, lambda, accessors, reducer)->E.R2.errMap(_e => {
+              "AHHH doesn't work"
+            })
           | _ => Error(impossibleError)
           },
         (),
diff --git a/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_Scoring.res b/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_Scoring.res
index 972501e9..d45b1a81 100644
--- a/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_Scoring.res
+++ b/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_Scoring.res
@@ -30,16 +30,16 @@ let library = [
             ("prior", FRTypeDist),
           ]),
         ],
-        ~run=(_, inputs, env, _) => {
+        ~run=(_, inputs, accessors, _) => {
           switch FunctionRegistry_Helpers.Prepare.ToValueArray.Record.threeArgs(inputs) {
           | Ok([FRValueDist(estimate), FRValueDistOrNumber(FRValueDist(d)), FRValueDist(prior)]) =>
-            runScoring(estimate, Score_Dist(d), Some(prior), env)
+            runScoring(estimate, Score_Dist(d), Some(prior), accessors.environment)
           | Ok([
               FRValueDist(estimate),
               FRValueDistOrNumber(FRValueNumber(d)),
               FRValueDist(prior),
             ]) =>
-            runScoring(estimate, Score_Scalar(d), Some(prior), env)
+            runScoring(estimate, Score_Scalar(d), Some(prior), accessors.environment)
           | Error(e) => Error(e)
           | _ => Error(FunctionRegistry_Helpers.impossibleError)
           }
@@ -49,12 +49,12 @@ let library = [
       FnDefinition.make(
         ~name="logScore",
         ~inputs=[FRTypeRecord([("estimate", FRTypeDist), ("answer", FRTypeDistOrNumber)])],
-        ~run=(_, inputs, env, _) => {
+        ~run=(_, inputs, accessors, _) => {
           switch FunctionRegistry_Helpers.Prepare.ToValueArray.Record.twoArgs(inputs) {
           | Ok([FRValueDist(estimate), FRValueDistOrNumber(FRValueDist(d))]) =>
-            runScoring(estimate, Score_Dist(d), None, env)
+            runScoring(estimate, Score_Dist(d), None, accessors.environment)
           | Ok([FRValueDist(estimate), FRValueDistOrNumber(FRValueNumber(d))]) =>
-            runScoring(estimate, Score_Scalar(d), None, env)
+            runScoring(estimate, Score_Scalar(d), None, accessors.environment)
           | Error(e) => Error(e)
           | _ => Error(FunctionRegistry_Helpers.impossibleError)
           }
@@ -74,10 +74,10 @@ let library = [
       FnDefinition.make(
         ~name="klDivergence",
         ~inputs=[FRTypeDist, FRTypeDist],
-        ~run=(_, inputs, env, _) => {
+        ~run=(_, inputs, accessors, _) => {
           switch inputs {
           | [FRValueDist(estimate), FRValueDist(d)] =>
-            runScoring(estimate, Score_Dist(d), None, env)
+            runScoring(estimate, Score_Dist(d), None, accessors.environment)
           | _ => Error(FunctionRegistry_Helpers.impossibleError)
           }
         },
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer.res
deleted file mode 100644
index bf8c89f9..00000000
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer.res
+++ /dev/null
@@ -1,35 +0,0 @@
-module ErrorValue = Reducer_ErrorValue
-module Expression = Reducer_Expression
-module ExternalExpressionValue = ReducerInterface_ExternalExpressionValue
-module InternalExpressionValue = ReducerInterface_InternalExpressionValue
-module Lambda = Reducer_Expression_Lambda
-
-type environment = ReducerInterface_InternalExpressionValue.environment
-type errorValue = Reducer_ErrorValue.errorValue
-type expressionValue = ExternalExpressionValue.t
-type externalBindings = ReducerInterface_ExternalExpressionValue.externalBindings
-type lambdaValue = ExternalExpressionValue.lambdaValue
-
-let evaluate = Expression.evaluate
-let evaluateUsingOptions = Expression.evaluateUsingOptions
-let evaluatePartialUsingExternalBindings = Expression.evaluatePartialUsingExternalBindings
-let parse = Expression.parse
-
-let foreignFunctionInterface = (
-  lambdaValue: ExternalExpressionValue.lambdaValue,
-  argArray: array<expressionValue>,
-  environment: ExternalExpressionValue.environment,
-) => {
-  let internallambdaValue = InternalExpressionValue.lambdaValueToInternal(lambdaValue)
-  let internalArgArray = argArray->Js.Array2.map(InternalExpressionValue.toInternal)
-  Lambda.foreignFunctionInterface(
-    internallambdaValue,
-    internalArgArray,
-    environment,
-    Expression.reduceExpression,
-  )->Belt.Result.map(InternalExpressionValue.toExternal)
-}
-
-let defaultEnvironment = ExternalExpressionValue.defaultEnvironment
-
-let defaultExternalBindings = ReducerInterface_StdLib.externalStdLib
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer.resi b/packages/squiggle-lang/src/rescript/Reducer/Reducer.resi
deleted file mode 100644
index bd0c43fb..00000000
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer.resi
+++ /dev/null
@@ -1,45 +0,0 @@
-module ErrorValue = Reducer_ErrorValue
-module Expression = Reducer_Expression
-
-@genType
-type environment = ReducerInterface_ExternalExpressionValue.environment
-@genType
-type errorValue = Reducer_ErrorValue.errorValue
-@genType
-type expressionValue = ReducerInterface_ExternalExpressionValue.t
-@genType
-type externalBindings = ReducerInterface_ExternalExpressionValue.externalBindings
-@genType
-type lambdaValue = ReducerInterface_ExternalExpressionValue.lambdaValue
-
-@genType
-let evaluateUsingOptions: (
-  ~environment: option<QuriSquiggleLang.ReducerInterface_ExternalExpressionValue.environment>,
-  ~externalBindings: option<
-    QuriSquiggleLang.ReducerInterface_ExternalExpressionValue.externalBindings,
-  >,
-  string,
-) => result<expressionValue, errorValue>
-@genType
-let evaluatePartialUsingExternalBindings: (
-  string,
-  QuriSquiggleLang.ReducerInterface_ExternalExpressionValue.externalBindings,
-  QuriSquiggleLang.ReducerInterface_ExternalExpressionValue.environment,
-) => result<externalBindings, errorValue>
-@genType
-let evaluate: string => result<expressionValue, errorValue>
-
-let parse: string => result<Expression.expression, errorValue>
-
-@genType
-let foreignFunctionInterface: (
-  QuriSquiggleLang.ReducerInterface_ExternalExpressionValue.lambdaValue,
-  array<QuriSquiggleLang.ReducerInterface_ExternalExpressionValue.t>,
-  QuriSquiggleLang.ReducerInterface_ExternalExpressionValue.environment,
-) => result<expressionValue, errorValue>
-
-@genType
-let defaultEnvironment: environment
-
-@genType
-let defaultExternalBindings: externalBindings
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Bindings/Reducer_Bindings.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Bindings/Reducer_Bindings.res
index 28175d7a..0f1c2037 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Bindings/Reducer_Bindings.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Bindings/Reducer_Bindings.res
@@ -74,9 +74,10 @@ let set = (nameSpace: t, id: string, value): t => {
 
 let emptyModule: t = NameSpace(emptyMap)
 let emptyBindings = emptyModule
+let emptyNameSpace = emptyModule
 
-let fromTypeScriptBindings = ReducerInterface_InternalExpressionValue.nameSpaceFromTypeScriptBindings
-let toTypeScriptBindings = ReducerInterface_InternalExpressionValue.nameSpaceToTypeScriptBindings
+// let fromTypeScriptBindings = ReducerInterface_InternalExpressionValue.nameSpaceFromTypeScriptBindings
+// let toTypeScriptBindings = ReducerInterface_InternalExpressionValue.nameSpaceToTypeScriptBindings
 
 let toExpressionValue = (nameSpace: t): internalExpressionValue => IEvBindings(nameSpace)
 let fromExpressionValue = (aValue: internalExpressionValue): t =>
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Dispatch/Reducer_Dispatch_BuiltIn.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Dispatch/Reducer_Dispatch_BuiltIn.res
index a2ca204a..1e8b19d0 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Dispatch/Reducer_Dispatch_BuiltIn.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Dispatch/Reducer_Dispatch_BuiltIn.res
@@ -1,11 +1,15 @@
+module Bindings = Reducer_Bindings
 module BindingsReplacer = Reducer_Expression_BindingsReplacer
+module Continuation = ReducerInterface_Value_Continuation
 module ExpressionT = Reducer_Expression_T
 module ExternalLibrary = ReducerInterface.ExternalLibrary
 module Lambda = Reducer_Expression_Lambda
 module MathJs = Reducer_MathJs
-module Bindings = Reducer_Bindings
+module ProjectAccessorsT = ReducerProject_ProjectAccessors_T
+module ProjectReducerFnT = ReducerProject_ReducerFn_T
 module Result = Belt.Result
 module TypeBuilder = Reducer_Type_TypeBuilder
+
 open ReducerInterface_InternalExpressionValue
 open Reducer_ErrorValue
 
@@ -19,10 +23,11 @@ open Reducer_ErrorValue
 
 exception TestRescriptException
 
-let callInternal = (call: functionCall, environment, reducer: ExpressionT.reducerFn): result<
-  'b,
-  errorValue,
-> => {
+let callInternal = (
+  call: functionCall,
+  accessors: ProjectAccessorsT.t,
+  reducer: ProjectReducerFnT.t,
+): result<'b, errorValue> => {
   let callMathJs = (call: functionCall): result<'b, errorValue> =>
     switch call {
     | ("javascriptraise", [msg]) => Js.Exn.raiseError(toString(msg)) // For Tests
@@ -95,9 +100,17 @@ let callInternal = (call: functionCall, environment, reducer: ExpressionT.reduce
 
   let doExportBindings = (bindings: nameSpace) => bindings->Bindings.toExpressionValue->Ok
 
+  let doIdentity = (value: internalExpressionValue) => value->Ok
+
+  let doDumpBindings = (continuation: nameSpace, value: internalExpressionValue) => {
+    // let _ = Continuation.inspect(continuation, "doDumpBindings")
+    accessors.states.continuation = continuation
+    value->Ok
+  }
+
   module SampleMap = {
     let doLambdaCall = (aLambdaValue, list) =>
-      switch Lambda.doLambdaCall(aLambdaValue, list, environment, reducer) {
+      switch Lambda.doLambdaCall(aLambdaValue, list, accessors, reducer) {
       | Ok(IEvNumber(f)) => Ok(f)
       | _ => Error(Operation.SampleMapNeedsNtoNFunction)
       }
@@ -137,12 +150,14 @@ let callInternal = (call: functionCall, environment, reducer: ExpressionT.reduce
   | ("$_constructArray_$", [IEvArray(aValueArray)]) => IEvArray(aValueArray)->Ok
   | ("$_constructRecord_$", [IEvArray(arrayOfPairs)]) => constructRecord(arrayOfPairs)
   | ("$_exportBindings_$", [IEvBindings(nameSpace)]) => doExportBindings(nameSpace)
+  | ("$_exportBindings_$", [evValue]) => doIdentity(evValue)
   | ("$_setBindings_$", [IEvBindings(nameSpace), IEvSymbol(symbol), value]) =>
     doSetBindings(nameSpace, symbol, value)
   | ("$_setTypeAliasBindings_$", [IEvBindings(nameSpace), IEvTypeIdentifier(symbol), value]) =>
     doSetTypeAliasBindings(nameSpace, symbol, value)
   | ("$_setTypeOfBindings_$", [IEvBindings(nameSpace), IEvSymbol(symbol), value]) =>
     doSetTypeOfBindings(nameSpace, symbol, value)
+  | ("$_dumpBindings_$", [IEvBindings(nameSpace), _, evValue]) => doDumpBindings(nameSpace, evValue)
   | ("$_typeModifier_memberOf_$", [IEvTypeIdentifier(typeIdentifier), IEvArray(arr)]) =>
     TypeBuilder.typeModifier_memberOf(IEvTypeIdentifier(typeIdentifier), IEvArray(arr))
   | ("$_typeModifier_memberOf_$", [IEvType(typeRecord), IEvArray(arr)]) =>
@@ -182,15 +197,16 @@ let callInternal = (call: functionCall, environment, reducer: ExpressionT.reduce
 /*
   Reducer uses Result monad while reducing expressions
 */
-let dispatch = (call: functionCall, environment, reducer: ExpressionT.reducerFn): result<
-  internalExpressionValue,
-  errorValue,
-> =>
+let dispatch = (
+  call: functionCall,
+  accessors: ProjectAccessorsT.t,
+  reducer: ProjectReducerFnT.t,
+): result<internalExpressionValue, errorValue> =>
   try {
     let (fn, args) = call
     // There is a bug that prevents string match in patterns
     // So we have to recreate a copy of the string
-    ExternalLibrary.dispatch((Js.String.make(fn), args), environment, reducer, callInternal)
+    ExternalLibrary.dispatch((Js.String.make(fn), args), accessors, reducer, callInternal)
   } catch {
   | Js.Exn.Error(obj) => REJavaScriptExn(Js.Exn.message(obj), Js.Exn.name(obj))->Error
   | _ => RETodo("unhandled rescript exception")->Error
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Dispatch/Reducer_Dispatch_BuiltInMacros.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Dispatch/Reducer_Dispatch_BuiltInMacros.res
index c4c76ce3..978ca399 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Dispatch/Reducer_Dispatch_BuiltInMacros.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Dispatch/Reducer_Dispatch_BuiltInMacros.res
@@ -3,17 +3,19 @@
   they take expressions as parameters and return a new expression.
   Macros are used to define language building blocks. They are like Lisp macros.
 */
+module Bindings = Reducer_Bindings
 module BindingsReplacer = Reducer_Expression_BindingsReplacer
 module ErrorValue = Reducer_ErrorValue
 module ExpressionBuilder = Reducer_Expression_ExpressionBuilder
 module ExpressionT = Reducer_Expression_T
-module InternalExpressionValue = ReducerInterface_InternalExpressionValue
 module ExpressionWithContext = Reducer_ExpressionWithContext
-module Bindings = Reducer_Bindings
+module InternalExpressionValue = ReducerInterface_InternalExpressionValue
+module ProjectAccessorsT = ReducerProject_ProjectAccessors_T
+module ProjectReducerFnT = ReducerProject_ReducerFn_T
 module Result = Belt.Result
+
 open Reducer_Expression_ExpressionBuilder
 
-type environment = InternalExpressionValue.environment
 type errorValue = ErrorValue.errorValue
 type expression = ExpressionT.expression
 type expressionWithContext = ExpressionWithContext.expressionWithContext
@@ -21,11 +23,11 @@ type expressionWithContext = ExpressionWithContext.expressionWithContext
 let dispatchMacroCall = (
   macroExpression: expression,
   bindings: ExpressionT.bindings,
-  environment,
-  reduceExpression: ExpressionT.reducerFn,
+  accessors: ProjectAccessorsT.t,
+  reduceExpression: ProjectReducerFnT.t,
 ): result<expressionWithContext, errorValue> => {
-  let useExpressionToSetBindings = (bindingExpr: expression, environment, statement, newCode) => {
-    let rExternalBindingsValue = reduceExpression(bindingExpr, bindings, environment)
+  let useExpressionToSetBindings = (bindingExpr: expression, accessors, statement, newCode) => {
+    let rExternalBindingsValue = reduceExpression(bindingExpr, bindings, accessors)
 
     rExternalBindingsValue->Result.flatMap(nameSpaceValue => {
       let newBindings = Bindings.fromExpressionValue(nameSpaceValue)
@@ -45,16 +47,17 @@ let dispatchMacroCall = (
     | "$_let_$" => "$_setBindings_$"
     | "$_typeOf_$" => "$_setTypeOfBindings_$"
     | "$_typeAlias_$" => "$_setTypeAliasBindings_$"
+    | "$_endOfOuterBlock_$" => "$_dumpBindings_$"
     | _ => ""
     }
 
-  let doBindStatement = (bindingExpr: expression, statement: expression, environment) => {
+  let doBindStatement = (bindingExpr: expression, statement: expression, accessors) => {
     let defaultStatement = ErrorValue.REAssignmentExpected->Error
     switch statement {
     | ExpressionT.EList(list{ExpressionT.EValue(IEvCall(callName)), symbolExpr, statement}) => {
         let setBindingsFn = correspondingSetBindingsFn(callName)
         if setBindingsFn !== "" {
-          useExpressionToSetBindings(bindingExpr, environment, statement, (
+          useExpressionToSetBindings(bindingExpr, accessors, statement, (
             newBindingsExpr,
             boundStatement,
           ) => eFunction(setBindingsFn, list{newBindingsExpr, symbolExpr, boundStatement}))
@@ -66,12 +69,12 @@ let dispatchMacroCall = (
     }
   }
 
-  let doBindExpression = (bindingExpr: expression, statement: expression, environment): result<
+  let doBindExpression = (bindingExpr: expression, statement: expression, accessors): result<
     expressionWithContext,
     errorValue,
   > => {
     let defaultStatement = () =>
-      useExpressionToSetBindings(bindingExpr, environment, statement, (
+      useExpressionToSetBindings(bindingExpr, accessors, statement, (
         _newBindingsExpr,
         boundStatement,
       ) => boundStatement)
@@ -80,13 +83,13 @@ let dispatchMacroCall = (
     | ExpressionT.EList(list{ExpressionT.EValue(IEvCall(callName)), symbolExpr, statement}) => {
         let setBindingsFn = correspondingSetBindingsFn(callName)
         if setBindingsFn !== "" {
-          useExpressionToSetBindings(bindingExpr, environment, statement, (
+          useExpressionToSetBindings(bindingExpr, accessors, statement, (
             newBindingsExpr,
             boundStatement,
           ) =>
             eFunction(
               "$_exportBindings_$",
-              list{eFunction(setBindingsFn, list{newBindingsExpr, symbolExpr, boundStatement})},
+              list{eFunction(setBindingsFn, list{newBindingsExpr, symbolExpr, boundStatement})}, // expression returning bindings
             )
           )
         } else {
@@ -97,7 +100,7 @@ let dispatchMacroCall = (
     }
   }
 
-  let doBlock = (exprs: list<expression>, _bindings: ExpressionT.bindings, _environment): result<
+  let doBlock = (exprs: list<expression>, _bindings: ExpressionT.bindings, _accessors): result<
     expressionWithContext,
     errorValue,
   > => {
@@ -130,10 +133,10 @@ let dispatchMacroCall = (
     ifTrue: expression,
     ifFalse: expression,
     bindings: ExpressionT.bindings,
-    environment,
+    accessors,
   ): result<expressionWithContext, errorValue> => {
     let blockCondition = ExpressionBuilder.eBlock(list{condition})
-    let rCondition = reduceExpression(blockCondition, bindings, environment)
+    let rCondition = reduceExpression(blockCondition, bindings, accessors)
     rCondition->Result.flatMap(conditionValue =>
       switch conditionValue {
       | InternalExpressionValue.IEvBool(false) => {
@@ -149,7 +152,7 @@ let dispatchMacroCall = (
     )
   }
 
-  let expandExpressionList = (aList, bindings: ExpressionT.bindings, environment): result<
+  let expandExpressionList = (aList, bindings: ExpressionT.bindings, accessors): result<
     expressionWithContext,
     errorValue,
   > =>
@@ -159,21 +162,21 @@ let dispatchMacroCall = (
         bindingExpr: ExpressionT.expression,
         statement,
       } =>
-      doBindStatement(bindingExpr, statement, environment)
+      doBindStatement(bindingExpr, statement, accessors)
     | list{ExpressionT.EValue(IEvCall("$$_bindStatement_$$")), statement} =>
       // bindings of the context are used when there is no binding expression
-      doBindStatement(eModule(bindings), statement, environment)
+      doBindStatement(eModule(bindings), statement, accessors)
     | list{
         ExpressionT.EValue(IEvCall("$$_bindExpression_$$")),
         bindingExpr: ExpressionT.expression,
         expression,
       } =>
-      doBindExpression(bindingExpr, expression, environment)
+      doBindExpression(bindingExpr, expression, accessors)
     | list{ExpressionT.EValue(IEvCall("$$_bindExpression_$$")), expression} =>
       // bindings of the context are used when there is no binding expression
-      doBindExpression(eModule(bindings), expression, environment)
+      doBindExpression(eModule(bindings), expression, accessors)
     | list{ExpressionT.EValue(IEvCall("$$_block_$$")), ...exprs} =>
-      doBlock(exprs, bindings, environment)
+      doBlock(exprs, bindings, accessors)
     | list{
         ExpressionT.EValue(IEvCall("$$_lambda_$$")),
         ExpressionT.EValue(IEvArrayString(parameters)),
@@ -181,12 +184,12 @@ let dispatchMacroCall = (
       } =>
       doLambdaDefinition(bindings, parameters, lambdaDefinition)
     | list{ExpressionT.EValue(IEvCall("$$_ternary_$$")), condition, ifTrue, ifFalse} =>
-      doTernary(condition, ifTrue, ifFalse, bindings, environment)
+      doTernary(condition, ifTrue, ifFalse, bindings, accessors)
     | _ => ExpressionWithContext.noContext(ExpressionT.EList(aList))->Ok
     }
 
   switch macroExpression {
-  | EList(aList) => expandExpressionList(aList, bindings, environment)
+  | EList(aList) => expandExpressionList(aList, bindings, accessors)
   | _ => ExpressionWithContext.noContext(macroExpression)->Ok
   }
 }
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Dispatch/Reducer_Dispatch_ChainPiece.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Dispatch/Reducer_Dispatch_ChainPiece.res
index 6cebfef5..310f4879 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Dispatch/Reducer_Dispatch_ChainPiece.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Dispatch/Reducer_Dispatch_ChainPiece.res
@@ -1,17 +1,21 @@
-module TypeChecker = Reducer_Type_TypeChecker
+module ProjectAccessorsT = ReducerProject_ProjectAccessors_T
 module T = Reducer_Dispatch_T
+module TypeChecker = Reducer_Type_TypeChecker
 open ReducerInterface_InternalExpressionValue
 
 type errorValue = Reducer_ErrorValue.errorValue
 
 let makeFromTypes = jumpTable => {
-  let dispatchChainPiece: T.dispatchChainPiece = ((fnName, fnArgs): functionCall, environment) => {
+  let dispatchChainPiece: T.dispatchChainPiece = (
+    (fnName, fnArgs): functionCall,
+    accessors: ProjectAccessorsT.t,
+  ) => {
     let jumpTableEntry = jumpTable->Js.Array2.find(elem => {
       let (candidName, candidType, _) = elem
       candidName == fnName && TypeChecker.checkITypeArgumentsBool(candidType, fnArgs)
     })
     switch jumpTableEntry {
-    | Some((_, _, bridgeFn)) => bridgeFn(fnArgs, environment)->Some
+    | Some((_, _, bridgeFn)) => bridgeFn(fnArgs, accessors)->Some
     | _ => None
     }
   }
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Dispatch/Reducer_Dispatch_T.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Dispatch/Reducer_Dispatch_T.res
index f6234976..68b8f789 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Dispatch/Reducer_Dispatch_T.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Dispatch/Reducer_Dispatch_T.res
@@ -1,20 +1,22 @@
 module InternalExpressionValue = ReducerInterface_InternalExpressionValue
 module ExpressionT = Reducer_Expression_T
+module ProjectAccessorsT = ReducerProject_ProjectAccessors_T
+module ProjectReducerFnT = ReducerProject_ReducerFn_T
 
 // Each piece of the dispatch chain computes the result or returns None so that the chain can continue
 type dispatchChainPiece = (
   InternalExpressionValue.functionCall,
-  InternalExpressionValue.environment,
+  ProjectAccessorsT.t,
 ) => option<result<InternalExpressionValue.t, Reducer_ErrorValue.errorValue>>
 
 type dispatchChainPieceWithReducer = (
   InternalExpressionValue.functionCall,
-  InternalExpressionValue.environment,
-  ExpressionT.reducerFn,
+  ProjectAccessorsT.t,
+  ProjectReducerFnT.t,
 ) => option<result<InternalExpressionValue.t, Reducer_ErrorValue.errorValue>>
 
 // This is a switch statement case implementation: get the arguments and compute the result
 type genericIEvFunction = (
   array<InternalExpressionValue.t>,
-  InternalExpressionValue.environment,
+  ProjectAccessorsT.t,
 ) => result<InternalExpressionValue.t, Reducer_ErrorValue.errorValue>
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_ErrorValue.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_ErrorValue.res
index 211c9f53..55cde709 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_ErrorValue.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_ErrorValue.res
@@ -1,9 +1,10 @@
+//TODO: Do not export here but in ForTS__Types
 @gentype.import("peggy") @genType.as("LocationRange")
-type location
+type syntaxErrorLocation
 
-@genType
+@genType.opaque
 type errorValue =
-  | REArityError(option<string>, int, int) //TODO: Binding a lambda to a variable should record the variable name in lambda for error reporting
+  | REArityError(option<string>, int, int)
   | REArrayIndexNotFound(string, int)
   | REAssignmentExpected
   | REDistributionError(DistributionTypes.error)
@@ -17,13 +18,13 @@ type errorValue =
   | REOperationError(Operation.operationError)
   | RERecordPropertyNotFound(string, string)
   | RESymbolNotFound(string)
-  | RESyntaxError(string, option<location>)
+  | RESyntaxError(string, option<syntaxErrorLocation>)
   | RETodo(string) // To do
   | REUnitNotFound(string)
+  | RENeedToRun
 
 type t = errorValue
 
-@genType
 let errorToString = err =>
   switch err {
   | REArityError(_oFnName, arity, usedArity) =>
@@ -57,4 +58,5 @@ let errorToString = err =>
   | RETodo(msg) => `TODO: ${msg}`
   | REExpectedType(typeName, valueString) => `Expected type: ${typeName} but got: ${valueString}`
   | REUnitNotFound(unitName) => `Unit not found: ${unitName}`
+  | RENeedToRun => "Need to run"
   }
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression.res
index 6de4f74a..f2b05036 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression.res
@@ -1,3 +1,4 @@
+module Bindings = Reducer_Bindings
 module BindingsReplacer = Reducer_Expression_BindingsReplacer
 module BuiltIn = Reducer_Dispatch_BuiltIn
 module ExpressionBuilder = Reducer_Expression_ExpressionBuilder
@@ -6,30 +7,21 @@ module InternalExpressionValue = ReducerInterface_InternalExpressionValue
 module Lambda = Reducer_Expression_Lambda
 module Macro = Reducer_Expression_Macro
 module MathJs = Reducer_MathJs
-module Bindings = Reducer_Bindings
+module ProjectAccessorsT = ReducerProject_ProjectAccessors_T
 module Result = Belt.Result
 module T = Reducer_Expression_T
 
-type environment = InternalExpressionValue.environment
 type errorValue = Reducer_ErrorValue.errorValue
-type expression = T.expression
-type internalExpressionValue = InternalExpressionValue.t
-type externalExpressionValue = ReducerInterface_ExternalExpressionValue.t
-type t = expression
+type t = T.t
 
 /*
-  Converts a Squigle code to expression
+  Recursively evaluate/reduce the expression (Lisp AST/Lambda calculus)
 */
-let parse = (peggyCode: string): result<t, errorValue> =>
-  peggyCode->Reducer_Peggy_Parse.parse->Result.map(Reducer_Peggy_ToExpression.fromNode)
-
-/*
-  Recursively evaluate/reduce the expression (Lisp AST)
-*/
-let rec reduceExpression = (expression: t, bindings: T.bindings, environment: environment): result<
-  internalExpressionValue,
-  'e,
-> => {
+let rec reduceExpressionInProject = (
+  expression: t,
+  continuation: T.bindings,
+  accessors: ProjectAccessorsT.t,
+): result<InternalExpressionValue.t, 'e> => {
   // Js.log(`reduce: ${T.toString(expression)} bindings: ${bindings->Bindings.toString}`)
   switch expression {
   | T.EValue(value) => value->Ok
@@ -38,41 +30,40 @@ let rec reduceExpression = (expression: t, bindings: T.bindings, environment: en
     | list{EValue(IEvCall(fName)), ..._args} =>
       switch Macro.isMacroName(fName) {
       // A macro expands then reduces itself
-      | true => Macro.doMacroCall(expression, bindings, environment, reduceExpression)
-      | false => reduceExpressionList(list, bindings, environment)
+      | true => Macro.doMacroCall(expression, continuation, accessors, reduceExpressionInProject)
+      | false => reduceExpressionList(list, continuation, accessors)
       }
-    | _ => reduceExpressionList(list, bindings, environment)
+    | _ => reduceExpressionList(list, continuation, accessors)
     }
   }
 }
-
 and reduceExpressionList = (
   expressions: list<t>,
-  bindings: T.bindings,
-  environment: environment,
-): result<internalExpressionValue, 'e> => {
+  continuation: T.bindings,
+  accessors: ProjectAccessorsT.t,
+): result<InternalExpressionValue.t, 'e> => {
   let racc: result<
-    list<internalExpressionValue>,
+    list<InternalExpressionValue.t>,
     'e,
-  > = expressions->Belt.List.reduceReverse(Ok(list{}), (racc, each: expression) =>
+  > = expressions->Belt.List.reduceReverse(Ok(list{}), (racc, each: t) =>
     racc->Result.flatMap(acc => {
       each
-      ->reduceExpression(bindings, environment)
+      ->reduceExpressionInProject(continuation, accessors)
       ->Result.map(newNode => {
         acc->Belt.List.add(newNode)
       })
     })
   )
-  racc->Result.flatMap(acc => acc->reduceValueList(environment))
+  racc->Result.flatMap(acc => acc->reduceValueList(accessors))
 }
 
 /*
     After reducing each level of expression(Lisp AST), we have a value list to evaluate
  */
-and reduceValueList = (valueList: list<internalExpressionValue>, environment): result<
-  internalExpressionValue,
-  'e,
-> =>
+and reduceValueList = (
+  valueList: list<InternalExpressionValue.t>,
+  accessors: ProjectAccessorsT.t,
+): result<InternalExpressionValue.t, 'e> =>
   switch valueList {
   | list{IEvCall(fName), ...args} => {
       let rCheckedArgs = switch fName {
@@ -81,7 +72,10 @@ and reduceValueList = (valueList: list<internalExpressionValue>, environment): r
       }
 
       rCheckedArgs->Result.flatMap(checkedArgs =>
-        (fName, checkedArgs->Belt.List.toArray)->BuiltIn.dispatch(environment, reduceExpression)
+        (fName, checkedArgs->Belt.List.toArray)->BuiltIn.dispatch(
+          accessors,
+          reduceExpressionInProject,
+        )
       )
     }
   | list{IEvLambda(_)} =>
@@ -91,11 +85,11 @@ and reduceValueList = (valueList: list<internalExpressionValue>, environment): r
     ->Result.flatMap(reducedValueList =>
       reducedValueList->Belt.List.toArray->InternalExpressionValue.IEvArray->Ok
     )
-  | list{IEvLambda(lamdaCall), ...args} =>
+  | list{IEvLambda(lambdaCall), ...args} =>
     args
     ->Lambda.checkIfReduced
     ->Result.flatMap(checkedArgs =>
-      Lambda.doLambdaCall(lamdaCall, checkedArgs, environment, reduceExpression)
+      Lambda.doLambdaCall(lambdaCall, checkedArgs, accessors, reduceExpressionInProject)
     )
 
   | _ =>
@@ -106,53 +100,27 @@ and reduceValueList = (valueList: list<internalExpressionValue>, environment): r
     )
   }
 
-let evalUsingBindingsExpression_ = (aExpression, bindings, environment): result<
-  internalExpressionValue,
-  'e,
-> => reduceExpression(aExpression, bindings, environment)
-
-let evaluateUsingOptions = (
-  ~environment: option<ReducerInterface_ExternalExpressionValue.environment>,
-  ~externalBindings: option<ReducerInterface_ExternalExpressionValue.externalBindings>,
-  code: string,
-): result<externalExpressionValue, errorValue> => {
-  let anEnvironment = Belt.Option.getWithDefault(
-    environment,
-    ReducerInterface_ExternalExpressionValue.defaultEnvironment,
-  )
-
-  let mergedBindings: InternalExpressionValue.nameSpace = Bindings.merge(
-    ReducerInterface_StdLib.internalStdLib,
-    Belt.Option.map(externalBindings, Bindings.fromTypeScriptBindings)->Belt.Option.getWithDefault(
-      Bindings.emptyModule,
-    ),
-  )
-
-  parse(code)
-  ->Result.flatMap(expr => evalUsingBindingsExpression_(expr, mergedBindings, anEnvironment))
-  ->Result.map(ReducerInterface_InternalExpressionValue.toExternal)
+let reduceReturningBindings = (
+  expression: t,
+  continuation: T.bindings,
+  accessors: ProjectAccessorsT.t,
+): (result<InternalExpressionValue.t, 'e>, T.bindings) => {
+  let states = accessors.states
+  let result = reduceExpressionInProject(expression, continuation, accessors)
+  (result, states.continuation)
 }
 
-/*
-  IEvaluates Squiggle code and bindings via Reducer and answers the result
-*/
-let evaluate = (code: string): result<externalExpressionValue, errorValue> => {
-  evaluateUsingOptions(~environment=None, ~externalBindings=None, code)
-}
-let evaluatePartialUsingExternalBindings = (
-  code: string,
-  externalBindings: ReducerInterface_ExternalExpressionValue.externalBindings,
-  environment: ReducerInterface_ExternalExpressionValue.environment,
-): result<ReducerInterface_ExternalExpressionValue.externalBindings, errorValue> => {
-  let rAnswer = evaluateUsingOptions(
-    ~environment=Some(environment),
-    ~externalBindings=Some(externalBindings),
-    code,
-  )
-  switch rAnswer {
-  | Ok(EvModule(externalBindings)) => Ok(externalBindings)
-  | Ok(_) =>
-    Error(Reducer_ErrorValue.RESyntaxError(`Partials must end with an assignment or record`, None))
-  | Error(err) => err->Error
+module BackCompatible = {
+  // Those methods are used to support the existing tests
+  // If they are used outside limited testing context, error location reporting will fail
+  let parse = (peggyCode: string): result<t, errorValue> =>
+    peggyCode->Reducer_Peggy_Parse.parse->Result.map(Reducer_Peggy_ToExpression.fromNode)
+
+  let evaluate = (expression: t): result<InternalExpressionValue.t, errorValue> => {
+    let accessors = ProjectAccessorsT.identityAccessors
+    expression->reduceExpressionInProject(accessors.stdLib, accessors)
   }
+
+  let evaluateString = (peggyCode: string): result<InternalExpressionValue.t, errorValue> =>
+    parse(peggyCode)->Result.flatMap(evaluate)
 }
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_ExpressionWithContext.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_ExpressionWithContext.res
index 44059e2b..808a2dcd 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_ExpressionWithContext.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_ExpressionWithContext.res
@@ -1,9 +1,11 @@
+module Bindings = Reducer_Bindings
 module BindingsReplacer = Reducer_Expression_BindingsReplacer
 module ErrorValue = Reducer_ErrorValue
 module ExpressionT = Reducer_Expression_T
 module InternalExpressionValue = ReducerInterface_InternalExpressionValue
+module ProjectAccessorsT = ReducerProject_ProjectAccessors_T
+module ProjectReducerFnT = ReducerProject_ReducerFn_T
 module Result = Belt.Result
-module Bindings = Reducer_Bindings
 
 type bindings = ExpressionT.bindings
 type context = bindings
@@ -11,7 +13,6 @@ type environment = InternalExpressionValue.environment
 type errorValue = Reducer_ErrorValue.errorValue
 type expression = ExpressionT.expression
 type internalExpressionValue = InternalExpressionValue.t
-type reducerFn = ExpressionT.reducerFn
 
 type expressionWithContext =
   | ExpressionWithContext(expression, context)
@@ -20,16 +21,16 @@ type expressionWithContext =
 let callReducer = (
   expressionWithContext: expressionWithContext,
   bindings: bindings,
-  environment: environment,
-  reducer: reducerFn,
+  accessors: ProjectAccessorsT.t,
+  reducer: ProjectReducerFnT.t,
 ): result<internalExpressionValue, errorValue> => {
   switch expressionWithContext {
   | ExpressionNoContext(expr) =>
     // Js.log(`callReducer: bindings ${Bindings.toString(bindings)} expr ${ExpressionT.toString(expr)}`)
-    reducer(expr, bindings, environment)
+    reducer(expr, bindings, accessors)
   | ExpressionWithContext(expr, context) =>
     // Js.log(`callReducer: context ${Bindings.toString(context)} expr ${ExpressionT.toString(expr)}`)
-    reducer(expr, context, environment)
+    reducer(expr, context, accessors)
   }
 }
 
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_BindingsReplacer.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_BindingsReplacer.res
index 15ecfe58..6e38f833 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_BindingsReplacer.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_BindingsReplacer.res
@@ -7,7 +7,6 @@ module Bindings = Reducer_Bindings
 type errorValue = Reducer_ErrorValue.errorValue
 type expression = ExpressionT.expression
 type internalExpressionValue = InternalExpressionValue.t
-type externalBindings = ReducerInterface_ExternalExpressionValue.externalBindings
 
 let isMacroName = (fName: string): bool => fName->Js.String2.startsWith("$$")
 
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_Lambda.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_Lambda.res
index 59779484..5ab7761d 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_Lambda.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_Lambda.res
@@ -1,12 +1,13 @@
+module Bindings = Reducer_Bindings
 module BindingsReplacer = Reducer_Expression_BindingsReplacer
 module ErrorValue = Reducer_ErrorValue
 module ExpressionBuilder = Reducer_Expression_ExpressionBuilder
 module ExpressionT = Reducer_Expression_T
 module ExpressionValue = ReducerInterface_InternalExpressionValue
-module Bindings = Reducer_Bindings
+module ProjectAccessorsT = ReducerProject_ProjectAccessors_T
+module ProjectReducerFnT = ReducerProject_ReducerFn_T
 module Result = Belt.Result
 
-type environment = ReducerInterface_InternalExpressionValue.environment
 type expression = ExpressionT.expression
 type expressionOrFFI = ExpressionT.expressionOrFFI
 type internalExpressionValue = ReducerInterface_InternalExpressionValue.t
@@ -44,7 +45,13 @@ let checkIfReduced = (args: list<internalExpressionValue>) =>
     )
   )
 
-let caseNotFFI = (lambdaValue: ExpressionValue.lambdaValue, expr, args, environment, reducer) => {
+let caseNotFFI = (
+  lambdaValue: ExpressionValue.lambdaValue,
+  expr,
+  args,
+  accessors: ProjectAccessorsT.t,
+  reducer: ProjectReducerFnT.t,
+) => {
   let parameterList = lambdaValue.parameters->Belt.List.fromArray
   let zippedParameterList = parameterList->Belt.List.zip(args)
   let bindings = Belt.List.reduce(zippedParameterList, lambdaValue.context, (
@@ -52,39 +59,43 @@ let caseNotFFI = (lambdaValue: ExpressionValue.lambdaValue, expr, args, environm
     (variable, variableValue),
   ) => acc->Bindings.set(variable, variableValue))
   let newExpression = ExpressionBuilder.eBlock(list{expr})
-  reducer(newExpression, bindings, environment)
+  reducer(newExpression, bindings, accessors)
 }
 
-let caseFFI = (ffiFn: ExpressionT.ffiFn, args, environment) => {
-  ffiFn(args->Belt.List.toArray, environment)
+let caseFFI = (ffiFn: ExpressionT.ffiFn, args, accessors: ProjectAccessorsT.t) => {
+  ffiFn(args->Belt.List.toArray, accessors.environment)
 }
 
 let applyParametersToLambda = (
   lambdaValue: ExpressionValue.lambdaValue,
   args,
-  environment,
-  reducer: ExpressionT.reducerFn,
+  accessors: ProjectAccessorsT.t,
+  reducer: ProjectReducerFnT.t,
 ): result<internalExpressionValue, 'e> => {
   checkArity(lambdaValue, args)->Result.flatMap(args =>
     checkIfReduced(args)->Result.flatMap(args => {
       let exprOrFFI = castInternalCodeToExpression(lambdaValue.body)
       switch exprOrFFI {
-      | NotFFI(expr) => caseNotFFI(lambdaValue, expr, args, environment, reducer)
-      | FFI(ffiFn) => caseFFI(ffiFn, args, environment)
+      | NotFFI(expr) => caseNotFFI(lambdaValue, expr, args, accessors, reducer)
+      | FFI(ffiFn) => caseFFI(ffiFn, args, accessors)
       }
     })
   )
 }
 
-let doLambdaCall = (lambdaValue: ExpressionValue.lambdaValue, args, environment, reducer) =>
-  applyParametersToLambda(lambdaValue, args, environment, reducer)
+let doLambdaCall = (
+  lambdaValue: ExpressionValue.lambdaValue,
+  args,
+  accessors: ProjectAccessorsT.t,
+  reducer: ProjectReducerFnT.t,
+) => applyParametersToLambda(lambdaValue, args, accessors, reducer)
 
 let foreignFunctionInterface = (
   lambdaValue: ExpressionValue.lambdaValue,
   argArray: array<internalExpressionValue>,
-  environment: ExpressionValue.environment,
-  reducer: ExpressionT.reducerFn,
-): result<internalExpressionValue, 'e> => {
+  accessors: ProjectAccessorsT.t,
+  reducer: ProjectReducerFnT.t,
+): result<internalExpressionValue, Reducer_ErrorValue.errorValue> => {
   let args = argArray->Belt.List.fromArray
-  applyParametersToLambda(lambdaValue, args, environment, reducer)
+  applyParametersToLambda(lambdaValue, args, accessors, reducer)
 }
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_Macro.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_Macro.res
index 2598a9ed..003d3170 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_Macro.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_Macro.res
@@ -2,6 +2,8 @@ module ExpressionT = Reducer_Expression_T
 module InternalExpressionValue = ReducerInterface_InternalExpressionValue
 module ExpressionWithContext = Reducer_ExpressionWithContext
 module Result = Belt.Result
+module ProjectAccessorsT = ReducerProject_ProjectAccessors_T
+module ProjectReducerFnT = ReducerProject_ReducerFn_T
 
 type environment = InternalExpressionValue.environment
 type expression = ExpressionT.expression
@@ -11,34 +13,29 @@ type expressionWithContext = ExpressionWithContext.expressionWithContext
 let expandMacroCall = (
   macroExpression: expression,
   bindings: ExpressionT.bindings,
-  environment: environment,
-  reduceExpression: ExpressionT.reducerFn,
+  accessors: ProjectAccessorsT.t,
+  reduceExpression: ProjectReducerFnT.t,
 ): result<expressionWithContext, 'e> =>
   Reducer_Dispatch_BuiltInMacros.dispatchMacroCall(
     macroExpression,
     bindings,
-    environment,
+    accessors,
     reduceExpression,
   )
 
 let doMacroCall = (
   macroExpression: expression,
   bindings: ExpressionT.bindings,
-  environment: environment,
-  reduceExpression: ExpressionT.reducerFn,
+  accessors: ProjectAccessorsT.t,
+  reduceExpression: ProjectReducerFnT.t,
 ): result<internalExpressionValue, 'e> =>
   expandMacroCall(
     macroExpression,
     bindings,
-    environment,
-    reduceExpression,
+    (accessors: ProjectAccessorsT.t),
+    (reduceExpression: ProjectReducerFnT.t),
   )->Result.flatMap(expressionWithContext =>
-    ExpressionWithContext.callReducer(
-      expressionWithContext,
-      bindings,
-      environment,
-      reduceExpression,
-    )
+    ExpressionWithContext.callReducer(expressionWithContext, bindings, accessors, reduceExpression)
   )
 
 let isMacroName = (fName: string): bool => fName->Js.String2.startsWith("$$")
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_T.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_T.res
index c9739be3..61f723df 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_T.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_T.res
@@ -17,6 +17,8 @@ type rec expression =
   | EValue(internalExpressionValue) // Irreducible built-in value. Reducer should not know the internals. External libraries are responsible
 and bindings = InternalExpressionValue.nameSpace
 
+type t = expression
+
 type reducerFn = (
   expression,
   bindings,
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_GeneratedParser.peggy b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_GeneratedParser.peggy
index 15837da4..ec490c42 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_GeneratedParser.peggy
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_GeneratedParser.peggy
@@ -9,12 +9,25 @@ start
 
 zeroOMoreArgumentsBlockOrExpression = innerBlockOrExpression / lambda
 
+//   { return h.makeFunctionCall('$_typeOf_$', [identifier, typeExpression])}
+// {return [h.nodeVoid()];}
 outerBlock 
   = statements:array_statements  finalExpression: (statementSeparator @expression)?
-    { if (finalExpression != null) { statements.push(finalExpression) }
-        return h.nodeBlock(statements) }
+    { if (finalExpression != null) 
+        { 
+          var newFinalExpression = h.makeFunctionCall('$_endOfOuterBlock_$', [h.nodeVoid(), finalExpression]);
+          statements.push(newFinalExpression);
+        }
+      else 
+        {
+          var newFinalStatement = h.makeFunctionCall('$_endOfOuterBlock_$', [h.nodeVoid(), h.nodeVoid()]);
+          statements.push(newFinalStatement);
+        }
+      return h.nodeBlock(statements) }
   / finalExpression: expression
-    { return h.nodeBlock([finalExpression])}
+    { 
+      var newFinalExpression = h.makeFunctionCall('$_endOfOuterBlock_$', [h.nodeVoid(), finalExpression]);
+      return h.nodeBlock([newFinalExpression])}
     
 innerBlockOrExpression  
   = quotedInnerBlock
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_Parse.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_Parse.res
index 193cb893..8ecff48c 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_Parse.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_Parse.res
@@ -5,13 +5,12 @@ type node = {"type": string}
 
 @module("./Reducer_Peggy_GeneratedParser.js") external parse__: string => node = "parse"
 
-type withLocation = {"location": Reducer_ErrorValue.location}
+type withLocation = {"location": Reducer_ErrorValue.syntaxErrorLocation}
 external castWithLocation: Js.Exn.t => withLocation = "%identity"
 
-let syntaxErrorToLocation = (error: Js.Exn.t): Reducer_ErrorValue.location =>
+let syntaxErrorToLocation = (error: Js.Exn.t): Reducer_ErrorValue.syntaxErrorLocation =>
   castWithLocation(error)["location"]
 
-@genType
 let parse = (expr: string): result<node, errorValue> =>
   try {
     Ok(parse__(expr))
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Type/Reducer_Type_Compile.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Type/Reducer_Type_Compile.res
index 896f4a12..79153801 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Type/Reducer_Type_Compile.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Type/Reducer_Type_Compile.res
@@ -1,47 +1,44 @@
+module Bindings = Reducer_Bindings
 module ErrorValue = Reducer_ErrorValue
+module Expression = Reducer_Expression
 module ExpressionT = Reducer_Expression_T
 module InternalExpressionValue = ReducerInterface_InternalExpressionValue
-module Bindings = Reducer_Bindings
+module ProjectAccessorsT = ReducerProject_ProjectAccessors_T
+module ProjectReducerFnT = ReducerProject_ReducerFn_T
 module T = Reducer_Type_T
 
 let ievFromTypeExpression = (
   typeExpressionSourceCode: string,
-  reducerFn: ExpressionT.reducerFn,
+  reducerFn: ProjectReducerFnT.t,
 ): result<InternalExpressionValue.t, ErrorValue.t> => {
   let sIndex = "compiled"
   let sourceCode = `type ${sIndex}=${typeExpressionSourceCode}`
-  Reducer_Expression.parse(sourceCode)->Belt.Result.flatMap(expr => {
-    let rContext = reducerFn(
-      expr,
-      Bindings.emptyBindings,
-      InternalExpressionValue.defaultEnvironment,
-    )
-    Belt.Result.map(rContext, context =>
-      switch context {
-      | IEvBindings(nameSpace) =>
-        switch Bindings.getType(nameSpace, sIndex) {
-        | Some(value) => value
-        | None => raise(Reducer_Exception.ImpossibleException("Reducer_Type_Compile-none"))
-        }
-      | _ => raise(Reducer_Exception.ImpossibleException("Reducer_Type_Compile-raise"))
+  Reducer_Expression.BackCompatible.parse(sourceCode)->Belt.Result.flatMap(expr => {
+    let accessors = ProjectAccessorsT.identityAccessors
+    let result = reducerFn(expr, Bindings.emptyBindings, accessors)
+    let nameSpace = accessors.states.continuation
+
+    switch result {
+    | Ok(_) =>
+      switch Bindings.getType(nameSpace, sIndex) {
+      | Some(value) => value->Ok
+      | None => raise(Reducer_Exception.ImpossibleException("Reducer_Type_Compile-none"))
       }
-    )
+    | err => err
+    }
   })
 }
 
-let fromTypeExpression = (
-  typeExpressionSourceCode: string,
-  reducerFn: ExpressionT.reducerFn,
-): result<T.t, ErrorValue.t> => {
-  ievFromTypeExpression(
-    (typeExpressionSourceCode: string),
-    (reducerFn: ExpressionT.reducerFn),
-  )->Belt.Result.map(T.fromIEvValue)
+let fromTypeExpression = (typeExpressionSourceCode: string, reducerFn: ProjectReducerFnT.t): result<
+  T.t,
+  ErrorValue.t,
+> => {
+  ievFromTypeExpression(typeExpressionSourceCode, reducerFn)->Belt.Result.map(T.fromIEvValue)
 }
 
 let fromTypeExpressionExn = (
   typeExpressionSourceCode: string,
-  reducerFn: ExpressionT.reducerFn,
+  reducerFn: ProjectReducerFnT.t,
 ): T.t =>
   switch fromTypeExpression(typeExpressionSourceCode, reducerFn) {
   | Ok(value) => value
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Type/Reducer_Type_TypeChecker.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Type/Reducer_Type_TypeChecker.res
index 33cbbeca..c9152e3c 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Type/Reducer_Type_TypeChecker.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Type/Reducer_Type_TypeChecker.res
@@ -1,5 +1,7 @@
 module ExpressionT = Reducer_Expression_T
 module InternalExpressionValue = ReducerInterface_InternalExpressionValue
+module ProjectAccessorsT = ReducerProject_ProjectAccessors_T
+module ProjectReducerFnT = ReducerProject_ReducerFn_T
 module T = Reducer_Type_T
 module TypeContracts = Reducer_Type_Contracts
 open InternalExpressionValue
@@ -129,7 +131,7 @@ let rec isITypeOf = (anIType: T.iType, aValue): result<bool, T.typeErrorValue> =
 let isTypeOf = (
   typeExpressionSourceCode: string,
   aValue: InternalExpressionValue.t,
-  reducerFn: ExpressionT.reducerFn,
+  reducerFn: ProjectReducerFnT.t,
 ): result<InternalExpressionValue.t, ErrorValue.t> => {
   switch typeExpressionSourceCode->Reducer_Type_Compile.fromTypeExpression(reducerFn) {
   | Ok(anIType) =>
@@ -164,7 +166,7 @@ let checkITypeArgumentsBool = (anIType: T.iType, args: array<InternalExpressionV
 let checkArguments = (
   typeExpressionSourceCode: string,
   args: array<InternalExpressionValue.t>,
-  reducerFn: ExpressionT.reducerFn,
+  reducerFn: ProjectReducerFnT.t,
 ): result<InternalExpressionValue.t, ErrorValue.t> => {
   switch typeExpressionSourceCode->Reducer_Type_Compile.fromTypeExpression(reducerFn) {
   | Ok(anIType) =>
diff --git a/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface.res b/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface.res
index ef27130b..d19b93b3 100644
--- a/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface.res
+++ b/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface.res
@@ -1,4 +1,3 @@
-module ExternalExpressionValue = ReducerInterface_ExternalExpressionValue
 module ExternalLibrary = ReducerInterface_ExternalLibrary
 module InternalExpressionValue = ReducerInterface_InternalExpressionValue
 module StdLib = ReducerInterface_StdLib
diff --git a/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_ExternalExpressionValue.res b/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_ExternalExpressionValue.res
deleted file mode 100644
index d613ceb8..00000000
--- a/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_ExternalExpressionValue.res
+++ /dev/null
@@ -1,99 +0,0 @@
-/*
-  Irreducible values. Reducer does not know about those. Only used for external calls
-  This is a configuration to to make external calls of those types
-*/
-module Extra_Array = Reducer_Extra_Array
-module ErrorValue = Reducer_ErrorValue
-@genType.opaque
-type internalCode = Object
-
-@genType.opaque
-type hiddenNameSpace = Object
-
-@genType
-type rec externalExpressionValue =
-  | EvArray(array<externalExpressionValue>)
-  | EvArrayString(array<string>)
-  | EvBool(bool)
-  | EvCall(string) // External function call
-  | EvDistribution(DistributionTypes.genericDist)
-  | EvLambda(lambdaValue)
-  | EvNumber(float)
-  | EvRecord(record)
-  | EvString(string)
-  | EvSymbol(string)
-  | EvDate(Js.Date.t)
-  | EvTimeDuration(float)
-  | EvDeclaration(lambdaDeclaration)
-  | EvTypeIdentifier(string)
-  | EvModule(record)
-  | EvType(record)
-  | EvVoid
-and record = Js.Dict.t<externalExpressionValue>
-and lambdaValue = {
-  parameters: array<string>,
-  context: hiddenNameSpace,
-  body: internalCode,
-}
-and lambdaDeclaration = Declaration.declaration<lambdaValue>
-
-@genType
-type externalBindings = record
-
-@genType
-type t = externalExpressionValue
-
-type functionCall = (string, array<externalExpressionValue>)
-
-let rec toString = aValue =>
-  switch aValue {
-  | EvArray(anArray) => {
-      let args = anArray->Js.Array2.map(each => toString(each))->Js.Array2.toString
-      `[${args}]`
-    }
-  | EvArrayString(anArray) => {
-      let args = anArray->Js.Array2.toString
-      `[${args}]`
-    }
-  | EvBool(aBool) => Js.String.make(aBool)
-  | EvCall(fName) => `:${fName}`
-  | EvDate(date) => DateTime.Date.toString(date)
-  | EvDeclaration(d) => Declaration.toString(d, r => toString(EvLambda(r)))
-  | EvDistribution(dist) => GenericDist.toString(dist)
-  | EvLambda(lambdaValue) => `lambda(${Js.Array2.toString(lambdaValue.parameters)}=>internal code)`
-  | EvModule(m) => `@${m->toStringRecord}`
-  | EvNumber(aNumber) => Js.String.make(aNumber)
-  | EvRecord(aRecord) => aRecord->toStringRecord
-  | EvString(aString) => `'${aString}'`
-  | EvSymbol(aString) => `:${aString}`
-  | EvTimeDuration(t) => DateTime.Duration.toString(t)
-  | EvType(t) => `type${t->toStringRecord}`
-  | EvTypeIdentifier(id) => `#${id}`
-  | EvVoid => `()`
-  }
-and toStringRecord = aRecord => {
-  let pairs =
-    aRecord
-    ->Js.Dict.entries
-    ->Js.Array2.map(((eachKey, eachValue)) => `${eachKey}: ${toString(eachValue)}`)
-    ->Js.Array2.toString
-  `{${pairs}}`
-}
-
-let argsToString = (args: array<externalExpressionValue>): string => {
-  args->Js.Array2.map(arg => arg->toString)->Js.Array2.toString
-}
-
-let toStringFunctionCall = ((fn, args)): string => `${fn}(${argsToString(args)})`
-
-let toStringResult = x =>
-  switch x {
-  | Ok(a) => `Ok(${toString(a)})`
-  | Error(m) => `Error(${ErrorValue.errorToString(m)})`
-  }
-
-@genType
-type environment = GenericDist.env
-
-@genType
-let defaultEnvironment: environment = DistributionOperation.defaultEnv
diff --git a/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_ExternalLibrary.res b/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_ExternalLibrary.res
index 7ae6ace9..89528a32 100644
--- a/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_ExternalLibrary.res
+++ b/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_ExternalLibrary.res
@@ -1,4 +1,6 @@
 module InternalExpressionValue = ReducerInterface_InternalExpressionValue
+module ProjectAccessorsT = ReducerProject_ProjectAccessors_T
+module ProjectReducerFnT = ReducerProject_ReducerFn_T
 type internalExpressionValue = InternalExpressionValue.t
 
 /*
@@ -6,17 +8,17 @@ type internalExpressionValue = InternalExpressionValue.t
 */
 let dispatch = (
   call: InternalExpressionValue.functionCall,
-  environment,
-  reducer: Reducer_Expression_T.reducerFn,
+  accessors: ProjectAccessorsT.t,
+  reducer: ProjectReducerFnT.t,
   chain,
 ): result<internalExpressionValue, 'e> => {
   E.A.O.firstSomeFn([
-    () => ReducerInterface_GenericDistribution.dispatch(call, environment),
-    () => ReducerInterface_Date.dispatch(call, environment),
-    () => ReducerInterface_Duration.dispatch(call, environment),
-    () => ReducerInterface_Number.dispatch(call, environment),
-    () => FunctionRegistry_Library.dispatch(call, environment, reducer),
-  ])->E.O2.defaultFn(() => chain(call, environment, reducer))
+    () => ReducerInterface_GenericDistribution.dispatch(call, accessors.environment),
+    () => ReducerInterface_Date.dispatch(call, accessors.environment),
+    () => ReducerInterface_Duration.dispatch(call, accessors.environment),
+    () => ReducerInterface_Number.dispatch(call, accessors.environment),
+    () => FunctionRegistry_Library.dispatch(call, accessors, reducer),
+  ])->E.O2.defaultFn(() => chain(call, accessors, reducer))
 }
 
 /*
diff --git a/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_GenericDistribution.resi b/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_GenericDistribution.resi
index 6cccdf17..4cf8a17d 100644
--- a/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_GenericDistribution.resi
+++ b/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_GenericDistribution.resi
@@ -1,4 +1,4 @@
 let dispatch: (
   ReducerInterface_InternalExpressionValue.functionCall,
-  ReducerInterface_ExternalExpressionValue.environment,
+  ReducerInterface_InternalExpressionValue.environment,
 ) => option<result<ReducerInterface_InternalExpressionValue.t, Reducer_ErrorValue.errorValue>>
diff --git a/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_InternalExpressionValue.res b/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_InternalExpressionValue.res
index 86718b64..6a26ecd2 100644
--- a/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_InternalExpressionValue.res
+++ b/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_InternalExpressionValue.res
@@ -1,11 +1,11 @@
 module ErrorValue = Reducer_ErrorValue
-module ExternalExpressionValue = ReducerInterface_ExternalExpressionValue
 module Extra_Array = Reducer_Extra_Array
-type internalCode = ExternalExpressionValue.internalCode
-type environment = ExternalExpressionValue.environment
+type internalCode = Object
+type environment = GenericDist.env
 
-let defaultEnvironment = ExternalExpressionValue.defaultEnvironment
+let defaultEnvironment: environment = DistributionOperation.defaultEnv
 
+@genType.opaque
 type rec t =
   | IEvArray(array<t>) // FIXME: Convert to MapInt
   | IEvArrayString(array<string>)
@@ -24,42 +24,21 @@ type rec t =
   | IEvType(map)
   | IEvTypeIdentifier(string)
   | IEvVoid
-and map = Belt.Map.String.t<t>
-and nameSpace = NameSpace(Belt.Map.String.t<t>)
+@genType.opaque and squiggleArray = array<t>
+@genType.opaque and map = Belt.Map.String.t<t>
+@genType.opaque and nameSpace = NameSpace(Belt.Map.String.t<t>)
+@genType.opaque
 and lambdaValue = {
   parameters: array<string>,
   context: nameSpace,
   body: internalCode,
 }
-and lambdaDeclaration = Declaration.declaration<lambdaValue>
+@genType.opaque and lambdaDeclaration = Declaration.declaration<lambdaValue>
 
 type internalExpressionValue = t
 
 type functionCall = (string, array<t>)
 
-module Internal = {
-  module NameSpace = {
-    external castNameSpaceToHidden: nameSpace => ExternalExpressionValue.hiddenNameSpace =
-      "%identity"
-    external castHiddenToNameSpace: ExternalExpressionValue.hiddenNameSpace => nameSpace =
-      "%identity"
-  }
-  module Lambda = {
-    let toInternal = (v: ExternalExpressionValue.lambdaValue): lambdaValue => {
-      let p = v.parameters
-      let c = v.context->NameSpace.castHiddenToNameSpace
-      let b = v.body
-      {parameters: p, context: c, body: b}
-    }
-    and toExternal = (v: lambdaValue): ExternalExpressionValue.lambdaValue => {
-      let p = v.parameters
-      let c = v.context->NameSpace.castNameSpaceToHidden
-      let b = v.body
-      {parameters: p, context: c, body: b}
-    }
-  }
-}
-
 let rec toString = aValue =>
   switch aValue {
   | IEvArray(anArray) => {
@@ -132,6 +111,12 @@ let toStringResult = x =>
   | Error(m) => `Error(${ErrorValue.errorToString(m)})`
   }
 
+let toStringOptionResult = x =>
+  switch x {
+  | Some(a) => toStringResult(a)
+  | None => "None"
+  }
+
 let toStringResultOkless = (codeResult: result<t, ErrorValue.errorValue>): string =>
   switch codeResult {
   | Ok(a) => toString(a)
@@ -140,7 +125,7 @@ let toStringResultOkless = (codeResult: result<t, ErrorValue.errorValue>): strin
 
 let toStringResultRecord = x =>
   switch x {
-  | Ok(a) => `Ok(${ExternalExpressionValue.toStringRecord(a)})`
+  | Ok(a) => `Ok(${toStringMap(a)})`
   | Error(m) => `Error(${ErrorValue.errorToString(m)})`
   }
 
@@ -188,27 +173,6 @@ let valueToValueType = value =>
   | IEvVoid => EvtVoid
   }
 
-let externalValueToValueType = (value: ExternalExpressionValue.t) =>
-  switch value {
-  | EvArray(_) => EvtArray
-  | EvArrayString(_) => EvtArrayString
-  | EvBool(_) => EvtBool
-  | EvCall(_) => EvtCall
-  | EvDate(_) => EvtDate
-  | EvDeclaration(_) => EvtDeclaration
-  | EvDistribution(_) => EvtDistribution
-  | EvLambda(_) => EvtLambda
-  | EvModule(_) => EvtModule
-  | EvNumber(_) => EvtNumber
-  | EvRecord(_) => EvtRecord
-  | EvString(_) => EvtString
-  | EvSymbol(_) => EvtSymbol
-  | EvTimeDuration(_) => EvtTimeDuration
-  | EvType(_) => EvtType
-  | EvTypeIdentifier(_) => EvtTypeIdentifier
-  | EvVoid => EvtVoid
-  }
-
 let functionCallToCallSignature = (functionCall: functionCall): functionCallSignature => {
   let (fn, args) = functionCall
   CallSignature(fn, args->Js.Array2.map(valueToValueType))
@@ -240,70 +204,18 @@ let functionCallSignatureToString = (functionCallSignature: functionCallSignatur
   `${fn}(${args->Js.Array2.map(valueTypeToString)->Js.Array2.toString})`
 }
 
-let rec toExternal = (iev: t): ExternalExpressionValue.t => {
-  switch iev {
-  | IEvArray(v) => v->Belt.Array.map(e => toExternal(e))->EvArray
-  | IEvArrayString(v) => EvArrayString(v)
-  | IEvBool(v) => EvBool(v)
-  | IEvCall(v) => EvCall(v)
-  | IEvDeclaration(v) => {
-      let fn = lambdaValueToExternal(v.fn)
-      let args = v.args
-      EvDeclaration({fn: fn, args: args})
-    }
-  | IEvDistribution(v) => EvDistribution(v)
-  | IEvLambda(v) => EvLambda(lambdaValueToExternal(v))
-  | IEvNumber(v) => EvNumber(v)
-  | IEvRecord(v) => v->mapToExternal->EvRecord
-  | IEvString(v) => EvString(v)
-  | IEvSymbol(v) => EvSymbol(v)
-  | IEvDate(v) => EvDate(v)
-  | IEvTimeDuration(v) => EvTimeDuration(v)
-  | IEvType(v) => v->mapToExternal->EvType
-  | IEvTypeIdentifier(v) => EvTypeIdentifier(v)
-  | IEvBindings(v) => v->nameSpaceToTypeScriptBindings->EvModule
-  | IEvVoid => EvVoid
-  }
-}
-and mapToExternal = v =>
-  v->Belt.Map.String.map(e => toExternal(e))->Belt.Map.String.toArray->Js.Dict.fromArray
-and lambdaValueToExternal = Internal.Lambda.toExternal
-and nameSpaceToTypeScriptBindings = (
-  nameSpace: nameSpace,
-): ReducerInterface_ExternalExpressionValue.externalBindings => {
-  let NameSpace(container) = nameSpace
-  Belt.Map.String.map(container, e => toExternal(e))->Belt.Map.String.toArray->Js.Dict.fromArray
-}
+let arrayToValueArray = (arr: array<t>): array<t> => arr
 
-let rec toInternal = (ev: ExternalExpressionValue.t): t => {
-  switch ev {
-  | EvArray(v) => v->Belt.Array.map(e => toInternal(e))->IEvArray
-  | EvArrayString(v) => IEvArrayString(v)
-  | EvBool(v) => IEvBool(v)
-  | EvCall(v) => IEvCall(v)
-  | EvDate(v) => IEvDate(v)
-  | EvDeclaration(v) => {
-      let fn = lambdaValueToInternal(v.fn)
-      let args = v.args
-      IEvDeclaration({fn: fn, args: args})
-    }
-  | EvDistribution(v) => IEvDistribution(v)
-  | EvLambda(v) => IEvLambda(lambdaValueToInternal(v))
-  | EvModule(v) => v->nameSpaceFromTypeScriptBindings->IEvBindings
-  | EvNumber(v) => IEvNumber(v)
-  | EvRecord(v) => v->recordToInternal->IEvRecord
-  | EvString(v) => IEvString(v)
-  | EvSymbol(v) => IEvSymbol(v)
-  | EvTimeDuration(v) => IEvTimeDuration(v)
-  | EvType(v) => v->recordToInternal->IEvType
-  | EvTypeIdentifier(v) => IEvTypeIdentifier(v)
-  | EvVoid => IEvVoid
-  }
+let recordToKeyValuePairs = (record: map): array<(string, t)> => record->Belt.Map.String.toArray
+
+// let nameSpaceToTypeScriptBindings = (
+//   nameSpace: nameSpace,
+// ) => {
+//   let NameSpace(container) = nameSpace
+//   Belt.Map.String.map(container, e => e->Belt.Map.String.toArray->Js.Dict.fromArray)
+// }
+
+let nameSpaceToKeyValuePairs = (nameSpace: nameSpace): array<(string, t)> => {
+  let NameSpace(container) = nameSpace
+  container->Belt.Map.String.toArray
 }
-and recordToInternal = v =>
-  v->Js.Dict.entries->Belt.Map.String.fromArray->Belt.Map.String.map(e => toInternal(e))
-and lambdaValueToInternal = Internal.Lambda.toInternal
-and nameSpaceFromTypeScriptBindings = (
-  r: ReducerInterface_ExternalExpressionValue.externalBindings,
-): nameSpace =>
-  r->Js.Dict.entries->Belt.Map.String.fromArray->Belt.Map.String.map(e => toInternal(e))->NameSpace
diff --git a/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_StdLib.res b/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_StdLib.res
index ec6c4fd4..a868eeb5 100644
--- a/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_StdLib.res
+++ b/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_StdLib.res
@@ -1,7 +1,4 @@
 module Bindings = Reducer_Bindings
 
-let internalStdLib =
+let internalStdLib: Bindings.t =
   Bindings.emptyBindings->SquiggleLibrary_Math.makeBindings->SquiggleLibrary_Versions.makeBindings
-
-@genType
-let externalStdLib = internalStdLib->Bindings.toTypeScriptBindings
diff --git a/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_Value/ReducerInterface_Value_Continuation.res b/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_Value/ReducerInterface_Value_Continuation.res
new file mode 100644
index 00000000..af1c16c9
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_Value/ReducerInterface_Value_Continuation.res
@@ -0,0 +1,28 @@
+module InternalExpressionValue = ReducerInterface_InternalExpressionValue
+
+type t = InternalExpressionValue.nameSpace
+
+let toValue = nameSpace => InternalExpressionValue.IEvBindings(nameSpace)
+let toString = nameSpace => InternalExpressionValue.toString(toValue(nameSpace))
+let toStringResult = rNameSpace =>
+  Belt.Result.map(rNameSpace, toValue(_))->InternalExpressionValue.toStringResult
+let toStringOptionResult = orNameSpace =>
+  Belt.Option.map(
+    orNameSpace,
+    Belt.Result.map(_, toValue(_)),
+  )->InternalExpressionValue.toStringOptionResult
+
+let inspect = (nameSpace, label: string) => Js.log(`${label}: ${toString(nameSpace)}`)
+
+let inspectOption = (oNameSpace, label: string) =>
+  switch oNameSpace {
+  | Some(nameSpace) => inspect(nameSpace, label)
+  | None => Js.log(`${label}: None`)
+  }
+
+let minus = (NameSpace(thisContainer): t, NameSpace(thatContainer): t) => {
+  Belt.Map.String.removeMany(
+    thisContainer,
+    Belt.Map.String.keysToArray(thatContainer),
+  )->InternalExpressionValue.NameSpace
+}
diff --git a/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject.res b/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject.res
new file mode 100644
index 00000000..5f2fdce0
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject.res
@@ -0,0 +1,208 @@
+// TODO: Auto clean project based on topology
+
+module Bindings = Reducer_Bindings
+module Continuation = ReducerInterface_Value_Continuation
+module ErrorValue = Reducer_ErrorValue
+module InternalExpressionValue = ReducerInterface_InternalExpressionValue
+module ProjectAccessorsT = ReducerProject_ProjectAccessors_T
+module ProjectItem = ReducerProject_ProjectItem
+module T = ReducerProject_T
+module Topology = ReducerProject_Topology
+
+type t = T.t
+
+module Private = {
+  type internalProject = T.Private.t
+  type t = T.Private.t
+
+  let getSourceIds = T.Private.getSourceIds
+  let getItem = T.Private.getItem
+  let getDependents = Topology.getDependents
+  let getDependencies = Topology.getDependencies
+  let getRunOrder = Topology.getRunOrder
+  let getRunOrderFor = Topology.getRunOrderFor
+
+  let createProject = () => {
+    let project: t = {
+      "tag": "reducerProject",
+      "items": Belt.Map.String.empty,
+      "stdLib": ReducerInterface_StdLib.internalStdLib,
+      "environment": InternalExpressionValue.defaultEnvironment,
+    }
+    project
+  }
+
+  let rec touchSource = (project: t, sourceId: string): unit => {
+    let item = project->getItem(sourceId)
+    let newItem = ProjectItem.touchSource(item)
+    Belt.Map.String.set(project["items"], sourceId, newItem)->T.Private.setFieldItems(project, _)
+    touchDependents(project, sourceId)
+  }
+  and touchDependents = (project: t, sourceId: string): unit => {
+    let _ = getDependents(project, sourceId)->Belt.Array.forEach(_, touchSource(project, _))
+  }
+
+  let getSource = (project: t, sourceId: string): option<string> =>
+    Belt.Map.String.get(project["items"], sourceId)->Belt.Option.map(ProjectItem.getSource)
+
+  let setSource = (project: t, sourceId: string, value: string): unit => {
+    let newItem = project->getItem(sourceId)->ProjectItem.setSource(value)
+    Belt.Map.String.set(project["items"], sourceId, newItem)->T.Private.setFieldItems(project, _)
+    touchDependents(project, sourceId)
+  }
+
+  let clean = (project: t, sourceId: string): unit => {
+    let newItem = project->getItem(sourceId)->ProjectItem.clean
+    Belt.Map.String.set(project["items"], sourceId, newItem)->T.Private.setFieldItems(project, _)
+  }
+
+  let cleanAll = (project: t): unit =>
+    getSourceIds(project)->Belt.Array.forEach(sourceId => clean(project, sourceId))
+
+  let cleanResults = (project: t, sourceId: string): unit => {
+    let newItem = project->getItem(sourceId)->ProjectItem.cleanResults
+    Belt.Map.String.set(project["items"], sourceId, newItem)->T.Private.setFieldItems(project, _)
+  }
+
+  let cleanAllResults = (project: t): unit =>
+    getSourceIds(project)->Belt.Array.forEach(sourceId => cleanResults(project, sourceId))
+
+  let getIncludes = (project: t, sourceId: string): ProjectItem.T.includesType =>
+    project->getItem(sourceId)->ProjectItem.getIncludes
+
+  let setContinues = (project: t, sourceId: string, continues: array<string>): unit => {
+    let newItem = project->getItem(sourceId)->ProjectItem.setContinues(continues)
+    Belt.Map.String.set(project["items"], sourceId, newItem)->T.Private.setFieldItems(project, _)
+    touchSource(project, sourceId)
+  }
+  let getContinues = (project: t, sourceId: string): array<string> =>
+    ProjectItem.getContinues(project->getItem(sourceId))
+
+  let removeContinues = (project: t, sourceId: string): unit => {
+    let newItem = project->getItem(sourceId)->ProjectItem.removeContinues
+    Belt.Map.String.set(project["items"], sourceId, newItem)->T.Private.setFieldItems(project, _)
+    touchSource(project, sourceId)
+  }
+
+  let getContinuation = (project: t, sourceId: string): ProjectItem.T.continuationArgumentType =>
+    project->getItem(sourceId)->ProjectItem.getContinuation
+
+  let setContinuation = (
+    project: t,
+    sourceId: string,
+    continuation: ProjectItem.T.continuationArgumentType,
+  ): unit => {
+    let newItem = project->getItem(sourceId)->ProjectItem.setContinuation(continuation)
+    Belt.Map.String.set(project["items"], sourceId, newItem)->T.Private.setFieldItems(project, _)
+  }
+
+  let getResultOption = (project: t, sourceId: string): ProjectItem.T.resultType =>
+    project->getItem(sourceId)->ProjectItem.getResult
+
+  let getResult = (project: t, sourceId: string): ProjectItem.T.resultArgumentType =>
+    switch getResultOption(project, sourceId) {
+    | None => RENeedToRun->Error
+    | Some(result) => result
+    }
+
+  let setResult = (project: t, sourceId: string, value: ProjectItem.T.resultArgumentType): unit => {
+    let newItem = project->getItem(sourceId)->ProjectItem.setResult(value)
+    Belt.Map.String.set(project["items"], sourceId, newItem)->T.Private.setFieldItems(project, _)
+  }
+
+  let parseIncludes = (project: t, sourceId: string): unit => {
+    let newItem = project->getItem(sourceId)->ProjectItem.parseIncludes
+    Belt.Map.String.set(project["items"], sourceId, newItem)->T.Private.setFieldItems(project, _)
+  }
+
+  let rawParse = (project: t, sourceId): unit => {
+    let newItem = project->getItem(sourceId)->ProjectItem.rawParse
+    Belt.Map.String.set(project["items"], sourceId, newItem)->T.Private.setFieldItems(project, _)
+  }
+
+  let getStdLib = (project: t): Reducer_Bindings.t => project["stdLib"]
+  let setStdLib = (project: t, value: Reducer_Bindings.t): unit =>
+    T.Private.setFieldStdLib(project, value)
+
+  let getEnvironment = (project: t): InternalExpressionValue.environment => project["environment"]
+  let setEnvironment = (project: t, value: InternalExpressionValue.environment): unit =>
+    T.Private.setFieldEnvironment(project, value)
+
+  let getBindings = (project: t, sourceId: string): ProjectItem.T.bindingsArgumentType => {
+    let those = project->getContinuation(sourceId)
+    let these = project->getStdLib
+    let ofUser = Continuation.minus(those, these)
+    ofUser
+  }
+
+  let buildProjectAccessors = (project: t): ProjectAccessorsT.t => {
+    states: {continuation: Bindings.emptyBindings},
+    stdLib: getStdLib(project),
+    environment: getEnvironment(project),
+  }
+
+  let doRunWithContinuation = (
+    project: t,
+    sourceId: string,
+    continuation: ProjectItem.T.continuation,
+  ): unit => {
+    let accessors = buildProjectAccessors(project)
+    let states = accessors.states
+    let newItem = project->getItem(sourceId)->ProjectItem.run(continuation, accessors)
+    Belt.Map.String.set(project["items"], sourceId, newItem)->T.Private.setFieldItems(project, _)
+    setContinuation(project, sourceId, states.continuation)
+  }
+
+  type runState = (ProjectItem.T.resultArgumentType, ProjectItem.T.continuation)
+
+  let tryRunWithContinuation = (
+    project: t,
+    sourceId: string,
+    (rPrevResult: ProjectItem.T.resultArgumentType, continuation: ProjectItem.T.continuation),
+  ): (ProjectItem.T.resultArgumentType, ProjectItem.T.continuation) => {
+    switch getResultOption(project, sourceId) {
+    | Some(result) => (result, getContinuation(project, sourceId)) // already ran
+    | None =>
+      switch rPrevResult {
+      | Error(error) => {
+          setResult(project, sourceId, Error(error))
+          (Error(error), continuation)
+        }
+      | Ok(_prevResult) => {
+          doRunWithContinuation(project, sourceId, continuation)
+          (
+            getResultOption(project, sourceId)->Belt.Option.getWithDefault(rPrevResult),
+            getContinuation(project, sourceId),
+          )
+        }
+      }
+    }
+  }
+
+  let runAll = (project: t): unit => {
+    let runOrder = Topology.getRunOrder(project)
+    let initialState = (Ok(InternalExpressionValue.IEvVoid), getStdLib(project))
+    let _finalState = Belt.Array.reduce(runOrder, initialState, (currState, currId) =>
+      tryRunWithContinuation(project, currId, currState)
+    )
+  }
+
+  let run = (project: t, sourceId: string): unit => {
+    let runOrder = Topology.getRunOrderFor(project, sourceId)
+    let initialState = (Ok(InternalExpressionValue.IEvVoid), getStdLib(project))
+    let _finalState = Belt.Array.reduce(runOrder, initialState, (currState, currId) =>
+      tryRunWithContinuation(project, currId, currState)
+    )
+  }
+
+  let evaluate = (sourceCode: string) => {
+    let project = createProject()
+    setSource(project, "main", sourceCode)
+    runAll(project)
+    let those = project->getContinuation("main")
+    let these = project->getStdLib
+    let ofUser = Continuation.minus(those, these)
+
+    (getResultOption(project, "main")->Belt.Option.getWithDefault(IEvVoid->Ok), ofUser)
+  }
+}
diff --git a/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject_IncludeParser.js b/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject_IncludeParser.js
new file mode 100644
index 00000000..e04b8ba2
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject_IncludeParser.js
@@ -0,0 +1,945 @@
+// Generated by Peggy 2.0.1.
+//
+// https://peggyjs.org/
+
+"use strict";
+
+function peg$subclass(child, parent) {
+  function C() { this.constructor = child; }
+  C.prototype = parent.prototype;
+  child.prototype = new C();
+}
+
+function peg$SyntaxError(message, expected, found, location) {
+  var self = Error.call(this, message);
+  // istanbul ignore next Check is a necessary evil to support older environments
+  if (Object.setPrototypeOf) {
+    Object.setPrototypeOf(self, peg$SyntaxError.prototype);
+  }
+  self.expected = expected;
+  self.found = found;
+  self.location = location;
+  self.name = "SyntaxError";
+  return self;
+}
+
+peg$subclass(peg$SyntaxError, Error);
+
+function peg$padEnd(str, targetLength, padString) {
+  padString = padString || " ";
+  if (str.length > targetLength) { return str; }
+  targetLength -= str.length;
+  padString += padString.repeat(targetLength);
+  return str + padString.slice(0, targetLength);
+}
+
+peg$SyntaxError.prototype.format = function(sources) {
+  var str = "Error: " + this.message;
+  if (this.location) {
+    var src = null;
+    var k;
+    for (k = 0; k < sources.length; k++) {
+      if (sources[k].source === this.location.source) {
+        src = sources[k].text.split(/\r\n|\n|\r/g);
+        break;
+      }
+    }
+    var s = this.location.start;
+    var loc = this.location.source + ":" + s.line + ":" + s.column;
+    if (src) {
+      var e = this.location.end;
+      var filler = peg$padEnd("", s.line.toString().length, ' ');
+      var line = src[s.line - 1];
+      var last = s.line === e.line ? e.column : line.length + 1;
+      var hatLen = (last - s.column) || 1;
+      str += "\n --> " + loc + "\n"
+          + filler + " |\n"
+          + s.line + " | " + line + "\n"
+          + filler + " | " + peg$padEnd("", s.column - 1, ' ')
+          + peg$padEnd("", hatLen, "^");
+    } else {
+      str += "\n at " + loc;
+    }
+  }
+  return str;
+};
+
+peg$SyntaxError.buildMessage = function(expected, found) {
+  var DESCRIBE_EXPECTATION_FNS = {
+    literal: function(expectation) {
+      return "\"" + literalEscape(expectation.text) + "\"";
+    },
+
+    class: function(expectation) {
+      var escapedParts = expectation.parts.map(function(part) {
+        return Array.isArray(part)
+          ? classEscape(part[0]) + "-" + classEscape(part[1])
+          : classEscape(part);
+      });
+
+      return "[" + (expectation.inverted ? "^" : "") + escapedParts.join("") + "]";
+    },
+
+    any: function() {
+      return "any character";
+    },
+
+    end: function() {
+      return "end of input";
+    },
+
+    other: function(expectation) {
+      return expectation.description;
+    }
+  };
+
+  function hex(ch) {
+    return ch.charCodeAt(0).toString(16).toUpperCase();
+  }
+
+  function literalEscape(s) {
+    return s
+      .replace(/\\/g, "\\\\")
+      .replace(/"/g,  "\\\"")
+      .replace(/\0/g, "\\0")
+      .replace(/\t/g, "\\t")
+      .replace(/\n/g, "\\n")
+      .replace(/\r/g, "\\r")
+      .replace(/[\x00-\x0F]/g,          function(ch) { return "\\x0" + hex(ch); })
+      .replace(/[\x10-\x1F\x7F-\x9F]/g, function(ch) { return "\\x"  + hex(ch); });
+  }
+
+  function classEscape(s) {
+    return s
+      .replace(/\\/g, "\\\\")
+      .replace(/\]/g, "\\]")
+      .replace(/\^/g, "\\^")
+      .replace(/-/g,  "\\-")
+      .replace(/\0/g, "\\0")
+      .replace(/\t/g, "\\t")
+      .replace(/\n/g, "\\n")
+      .replace(/\r/g, "\\r")
+      .replace(/[\x00-\x0F]/g,          function(ch) { return "\\x0" + hex(ch); })
+      .replace(/[\x10-\x1F\x7F-\x9F]/g, function(ch) { return "\\x"  + hex(ch); });
+  }
+
+  function describeExpectation(expectation) {
+    return DESCRIBE_EXPECTATION_FNS[expectation.type](expectation);
+  }
+
+  function describeExpected(expected) {
+    var descriptions = expected.map(describeExpectation);
+    var i, j;
+
+    descriptions.sort();
+
+    if (descriptions.length > 0) {
+      for (i = 1, j = 1; i < descriptions.length; i++) {
+        if (descriptions[i - 1] !== descriptions[i]) {
+          descriptions[j] = descriptions[i];
+          j++;
+        }
+      }
+      descriptions.length = j;
+    }
+
+    switch (descriptions.length) {
+      case 1:
+        return descriptions[0];
+
+      case 2:
+        return descriptions[0] + " or " + descriptions[1];
+
+      default:
+        return descriptions.slice(0, -1).join(", ")
+          + ", or "
+          + descriptions[descriptions.length - 1];
+    }
+  }
+
+  function describeFound(found) {
+    return found ? "\"" + literalEscape(found) + "\"" : "end of input";
+  }
+
+  return "Expected " + describeExpected(expected) + " but " + describeFound(found) + " found.";
+};
+
+function peg$parse(input, options) {
+  options = options !== undefined ? options : {};
+
+  var peg$FAILED = {};
+  var peg$source = options.grammarSource;
+
+  var peg$startRuleFunctions = { start: peg$parsestart };
+  var peg$startRuleFunction = peg$parsestart;
+
+  var peg$c0 = "#include";
+  var peg$c1 = "'";
+  var peg$c2 = "\"";
+  var peg$c3 = "//";
+  var peg$c4 = "/*";
+  var peg$c5 = "*/";
+
+  var peg$r0 = /^[^']/;
+  var peg$r1 = /^[^"]/;
+  var peg$r2 = /^[^*]/;
+  var peg$r3 = /^[ \t]/;
+  var peg$r4 = /^[\n\r]/;
+  var peg$r5 = /^[^\r\n]/;
+
+  var peg$e0 = peg$literalExpectation("#include", false);
+  var peg$e1 = peg$otherExpectation("string");
+  var peg$e2 = peg$literalExpectation("'", false);
+  var peg$e3 = peg$classExpectation(["'"], true, false);
+  var peg$e4 = peg$literalExpectation("\"", false);
+  var peg$e5 = peg$classExpectation(["\""], true, false);
+  var peg$e6 = peg$literalExpectation("//", false);
+  var peg$e7 = peg$literalExpectation("/*", false);
+  var peg$e8 = peg$classExpectation(["*"], true, false);
+  var peg$e9 = peg$literalExpectation("*/", false);
+  var peg$e10 = peg$otherExpectation("white space");
+  var peg$e11 = peg$classExpectation([" ", "\t"], false, false);
+  var peg$e12 = peg$otherExpectation("newline");
+  var peg$e13 = peg$classExpectation(["\n", "\r"], false, false);
+  var peg$e14 = peg$classExpectation(["\r", "\n"], true, false);
+
+  var peg$f0 = function(head, tail) {return [head, ...tail].filter( e => e != '');};
+  var peg$f1 = function() {return [];};
+  var peg$f2 = function(characters) {return characters.join('');};
+  var peg$f3 = function(characters) {return characters.join('');};
+  var peg$f4 = function() { return '';};
+  var peg$f5 = function() { return '';};
+  var peg$currPos = 0;
+  var peg$savedPos = 0;
+  var peg$posDetailsCache = [{ line: 1, column: 1 }];
+  var peg$maxFailPos = 0;
+  var peg$maxFailExpected = [];
+  var peg$silentFails = 0;
+
+  var peg$resultsCache = {};
+
+  var peg$result;
+
+  if ("startRule" in options) {
+    if (!(options.startRule in peg$startRuleFunctions)) {
+      throw new Error("Can't start parsing from rule \"" + options.startRule + "\".");
+    }
+
+    peg$startRuleFunction = peg$startRuleFunctions[options.startRule];
+  }
+
+  function text() {
+    return input.substring(peg$savedPos, peg$currPos);
+  }
+
+  function offset() {
+    return peg$savedPos;
+  }
+
+  function range() {
+    return {
+      source: peg$source,
+      start: peg$savedPos,
+      end: peg$currPos
+    };
+  }
+
+  function location() {
+    return peg$computeLocation(peg$savedPos, peg$currPos);
+  }
+
+  function expected(description, location) {
+    location = location !== undefined
+      ? location
+      : peg$computeLocation(peg$savedPos, peg$currPos);
+
+    throw peg$buildStructuredError(
+      [peg$otherExpectation(description)],
+      input.substring(peg$savedPos, peg$currPos),
+      location
+    );
+  }
+
+  function error(message, location) {
+    location = location !== undefined
+      ? location
+      : peg$computeLocation(peg$savedPos, peg$currPos);
+
+    throw peg$buildSimpleError(message, location);
+  }
+
+  function peg$literalExpectation(text, ignoreCase) {
+    return { type: "literal", text: text, ignoreCase: ignoreCase };
+  }
+
+  function peg$classExpectation(parts, inverted, ignoreCase) {
+    return { type: "class", parts: parts, inverted: inverted, ignoreCase: ignoreCase };
+  }
+
+  function peg$anyExpectation() {
+    return { type: "any" };
+  }
+
+  function peg$endExpectation() {
+    return { type: "end" };
+  }
+
+  function peg$otherExpectation(description) {
+    return { type: "other", description: description };
+  }
+
+  function peg$computePosDetails(pos) {
+    var details = peg$posDetailsCache[pos];
+    var p;
+
+    if (details) {
+      return details;
+    } else {
+      p = pos - 1;
+      while (!peg$posDetailsCache[p]) {
+        p--;
+      }
+
+      details = peg$posDetailsCache[p];
+      details = {
+        line: details.line,
+        column: details.column
+      };
+
+      while (p < pos) {
+        if (input.charCodeAt(p) === 10) {
+          details.line++;
+          details.column = 1;
+        } else {
+          details.column++;
+        }
+
+        p++;
+      }
+
+      peg$posDetailsCache[pos] = details;
+
+      return details;
+    }
+  }
+
+  function peg$computeLocation(startPos, endPos) {
+    var startPosDetails = peg$computePosDetails(startPos);
+    var endPosDetails = peg$computePosDetails(endPos);
+
+    return {
+      source: peg$source,
+      start: {
+        offset: startPos,
+        line: startPosDetails.line,
+        column: startPosDetails.column
+      },
+      end: {
+        offset: endPos,
+        line: endPosDetails.line,
+        column: endPosDetails.column
+      }
+    };
+  }
+
+  function peg$fail(expected) {
+    if (peg$currPos < peg$maxFailPos) { return; }
+
+    if (peg$currPos > peg$maxFailPos) {
+      peg$maxFailPos = peg$currPos;
+      peg$maxFailExpected = [];
+    }
+
+    peg$maxFailExpected.push(expected);
+  }
+
+  function peg$buildSimpleError(message, location) {
+    return new peg$SyntaxError(message, null, null, location);
+  }
+
+  function peg$buildStructuredError(expected, found, location) {
+    return new peg$SyntaxError(
+      peg$SyntaxError.buildMessage(expected, found),
+      expected,
+      found,
+      location
+    );
+  }
+
+  function peg$parsestart() {
+    var s0, s1, s2, s3, s4;
+
+    var key = peg$currPos * 10 + 0;
+    var cached = peg$resultsCache[key];
+
+    if (cached) {
+      peg$currPos = cached.nextPos;
+
+      return cached.result;
+    }
+
+    s0 = peg$currPos;
+    s1 = [];
+    s2 = peg$parsenewLine();
+    if (s2 === peg$FAILED) {
+      s2 = peg$parse_();
+      if (s2 === peg$FAILED) {
+        s2 = peg$parsecomment();
+        if (s2 === peg$FAILED) {
+          s2 = peg$parsedelimitedComment();
+        }
+      }
+    }
+    while (s2 !== peg$FAILED) {
+      s1.push(s2);
+      s2 = peg$parsenewLine();
+      if (s2 === peg$FAILED) {
+        s2 = peg$parse_();
+        if (s2 === peg$FAILED) {
+          s2 = peg$parsecomment();
+          if (s2 === peg$FAILED) {
+            s2 = peg$parsedelimitedComment();
+          }
+        }
+      }
+    }
+    s2 = peg$parseincludes();
+    if (s2 !== peg$FAILED) {
+      s3 = [];
+      s4 = peg$parsenewLine();
+      while (s4 !== peg$FAILED) {
+        s3.push(s4);
+        s4 = peg$parsenewLine();
+      }
+      s4 = peg$parseignore();
+      s0 = s2;
+    } else {
+      peg$currPos = s0;
+      s0 = peg$FAILED;
+    }
+
+    peg$resultsCache[key] = { nextPos: peg$currPos, result: s0 };
+
+    return s0;
+  }
+
+  function peg$parseincludes() {
+    var s0, s1, s2, s3, s4, s5;
+
+    var key = peg$currPos * 10 + 1;
+    var cached = peg$resultsCache[key];
+
+    if (cached) {
+      peg$currPos = cached.nextPos;
+
+      return cached.result;
+    }
+
+    s0 = peg$currPos;
+    s1 = peg$parseincludeStatement();
+    if (s1 !== peg$FAILED) {
+      s2 = [];
+      s3 = peg$currPos;
+      s4 = [];
+      s5 = peg$parsenewLine();
+      if (s5 !== peg$FAILED) {
+        while (s5 !== peg$FAILED) {
+          s4.push(s5);
+          s5 = peg$parsenewLine();
+        }
+      } else {
+        s4 = peg$FAILED;
+      }
+      if (s4 !== peg$FAILED) {
+        s5 = peg$parseincludeStatement();
+        if (s5 !== peg$FAILED) {
+          s3 = s5;
+        } else {
+          peg$currPos = s3;
+          s3 = peg$FAILED;
+        }
+      } else {
+        peg$currPos = s3;
+        s3 = peg$FAILED;
+      }
+      while (s3 !== peg$FAILED) {
+        s2.push(s3);
+        s3 = peg$currPos;
+        s4 = [];
+        s5 = peg$parsenewLine();
+        if (s5 !== peg$FAILED) {
+          while (s5 !== peg$FAILED) {
+            s4.push(s5);
+            s5 = peg$parsenewLine();
+          }
+        } else {
+          s4 = peg$FAILED;
+        }
+        if (s4 !== peg$FAILED) {
+          s5 = peg$parseincludeStatement();
+          if (s5 !== peg$FAILED) {
+            s3 = s5;
+          } else {
+            peg$currPos = s3;
+            s3 = peg$FAILED;
+          }
+        } else {
+          peg$currPos = s3;
+          s3 = peg$FAILED;
+        }
+      }
+      peg$savedPos = s0;
+      s0 = peg$f0(s1, s2);
+    } else {
+      peg$currPos = s0;
+      s0 = peg$FAILED;
+    }
+    if (s0 === peg$FAILED) {
+      s0 = peg$currPos;
+      s1 = peg$parseignore();
+      peg$savedPos = s0;
+      s1 = peg$f1();
+      s0 = s1;
+    }
+
+    peg$resultsCache[key] = { nextPos: peg$currPos, result: s0 };
+
+    return s0;
+  }
+
+  function peg$parseincludeStatement() {
+    var s0, s1, s2, s3, s4, s5, s6;
+
+    var key = peg$currPos * 10 + 2;
+    var cached = peg$resultsCache[key];
+
+    if (cached) {
+      peg$currPos = cached.nextPos;
+
+      return cached.result;
+    }
+
+    s0 = peg$currPos;
+    s1 = [];
+    s2 = peg$parse_();
+    while (s2 !== peg$FAILED) {
+      s1.push(s2);
+      s2 = peg$parse_();
+    }
+    if (input.substr(peg$currPos, 8) === peg$c0) {
+      s2 = peg$c0;
+      peg$currPos += 8;
+    } else {
+      s2 = peg$FAILED;
+      if (peg$silentFails === 0) { peg$fail(peg$e0); }
+    }
+    if (s2 !== peg$FAILED) {
+      s3 = [];
+      s4 = peg$parse_();
+      while (s4 !== peg$FAILED) {
+        s3.push(s4);
+        s4 = peg$parse_();
+      }
+      s4 = peg$parsestring();
+      if (s4 !== peg$FAILED) {
+        s5 = [];
+        s6 = peg$parse_();
+        while (s6 !== peg$FAILED) {
+          s5.push(s6);
+          s6 = peg$parse_();
+        }
+        s0 = s4;
+      } else {
+        peg$currPos = s0;
+        s0 = peg$FAILED;
+      }
+    } else {
+      peg$currPos = s0;
+      s0 = peg$FAILED;
+    }
+    if (s0 === peg$FAILED) {
+      s0 = peg$parsecomment();
+      if (s0 === peg$FAILED) {
+        s0 = peg$parsedelimitedComment();
+      }
+    }
+
+    peg$resultsCache[key] = { nextPos: peg$currPos, result: s0 };
+
+    return s0;
+  }
+
+  function peg$parsestring() {
+    var s0, s1, s2, s3, s4;
+
+    var key = peg$currPos * 10 + 3;
+    var cached = peg$resultsCache[key];
+
+    if (cached) {
+      peg$currPos = cached.nextPos;
+
+      return cached.result;
+    }
+
+    peg$silentFails++;
+    s0 = peg$currPos;
+    s1 = peg$currPos;
+    if (input.charCodeAt(peg$currPos) === 39) {
+      s2 = peg$c1;
+      peg$currPos++;
+    } else {
+      s2 = peg$FAILED;
+      if (peg$silentFails === 0) { peg$fail(peg$e2); }
+    }
+    if (s2 !== peg$FAILED) {
+      s3 = [];
+      if (peg$r0.test(input.charAt(peg$currPos))) {
+        s4 = input.charAt(peg$currPos);
+        peg$currPos++;
+      } else {
+        s4 = peg$FAILED;
+        if (peg$silentFails === 0) { peg$fail(peg$e3); }
+      }
+      while (s4 !== peg$FAILED) {
+        s3.push(s4);
+        if (peg$r0.test(input.charAt(peg$currPos))) {
+          s4 = input.charAt(peg$currPos);
+          peg$currPos++;
+        } else {
+          s4 = peg$FAILED;
+          if (peg$silentFails === 0) { peg$fail(peg$e3); }
+        }
+      }
+      if (input.charCodeAt(peg$currPos) === 39) {
+        s4 = peg$c1;
+        peg$currPos++;
+      } else {
+        s4 = peg$FAILED;
+        if (peg$silentFails === 0) { peg$fail(peg$e2); }
+      }
+      if (s4 !== peg$FAILED) {
+        s1 = s3;
+      } else {
+        peg$currPos = s1;
+        s1 = peg$FAILED;
+      }
+    } else {
+      peg$currPos = s1;
+      s1 = peg$FAILED;
+    }
+    if (s1 !== peg$FAILED) {
+      peg$savedPos = s0;
+      s1 = peg$f2(s1);
+    }
+    s0 = s1;
+    if (s0 === peg$FAILED) {
+      s0 = peg$currPos;
+      s1 = peg$currPos;
+      if (input.charCodeAt(peg$currPos) === 34) {
+        s2 = peg$c2;
+        peg$currPos++;
+      } else {
+        s2 = peg$FAILED;
+        if (peg$silentFails === 0) { peg$fail(peg$e4); }
+      }
+      if (s2 !== peg$FAILED) {
+        s3 = [];
+        if (peg$r1.test(input.charAt(peg$currPos))) {
+          s4 = input.charAt(peg$currPos);
+          peg$currPos++;
+        } else {
+          s4 = peg$FAILED;
+          if (peg$silentFails === 0) { peg$fail(peg$e5); }
+        }
+        while (s4 !== peg$FAILED) {
+          s3.push(s4);
+          if (peg$r1.test(input.charAt(peg$currPos))) {
+            s4 = input.charAt(peg$currPos);
+            peg$currPos++;
+          } else {
+            s4 = peg$FAILED;
+            if (peg$silentFails === 0) { peg$fail(peg$e5); }
+          }
+        }
+        if (input.charCodeAt(peg$currPos) === 34) {
+          s4 = peg$c2;
+          peg$currPos++;
+        } else {
+          s4 = peg$FAILED;
+          if (peg$silentFails === 0) { peg$fail(peg$e4); }
+        }
+        if (s4 !== peg$FAILED) {
+          s1 = s3;
+        } else {
+          peg$currPos = s1;
+          s1 = peg$FAILED;
+        }
+      } else {
+        peg$currPos = s1;
+        s1 = peg$FAILED;
+      }
+      if (s1 !== peg$FAILED) {
+        peg$savedPos = s0;
+        s1 = peg$f3(s1);
+      }
+      s0 = s1;
+    }
+    peg$silentFails--;
+    if (s0 === peg$FAILED) {
+      s1 = peg$FAILED;
+      if (peg$silentFails === 0) { peg$fail(peg$e1); }
+    }
+
+    peg$resultsCache[key] = { nextPos: peg$currPos, result: s0 };
+
+    return s0;
+  }
+
+  function peg$parseignore() {
+    var s0, s1;
+
+    var key = peg$currPos * 10 + 4;
+    var cached = peg$resultsCache[key];
+
+    if (cached) {
+      peg$currPos = cached.nextPos;
+
+      return cached.result;
+    }
+
+    s0 = [];
+    s1 = peg$parseany();
+    if (s1 === peg$FAILED) {
+      s1 = peg$parsenewLine();
+      if (s1 === peg$FAILED) {
+        s1 = peg$parse_();
+      }
+    }
+    while (s1 !== peg$FAILED) {
+      s0.push(s1);
+      s1 = peg$parseany();
+      if (s1 === peg$FAILED) {
+        s1 = peg$parsenewLine();
+        if (s1 === peg$FAILED) {
+          s1 = peg$parse_();
+        }
+      }
+    }
+
+    peg$resultsCache[key] = { nextPos: peg$currPos, result: s0 };
+
+    return s0;
+  }
+
+  function peg$parsecomment() {
+    var s0, s1, s2, s3;
+
+    var key = peg$currPos * 10 + 5;
+    var cached = peg$resultsCache[key];
+
+    if (cached) {
+      peg$currPos = cached.nextPos;
+
+      return cached.result;
+    }
+
+    s0 = peg$currPos;
+    if (input.substr(peg$currPos, 2) === peg$c3) {
+      s1 = peg$c3;
+      peg$currPos += 2;
+    } else {
+      s1 = peg$FAILED;
+      if (peg$silentFails === 0) { peg$fail(peg$e6); }
+    }
+    if (s1 !== peg$FAILED) {
+      s2 = [];
+      s3 = peg$parseany();
+      while (s3 !== peg$FAILED) {
+        s2.push(s3);
+        s3 = peg$parseany();
+      }
+      peg$savedPos = s0;
+      s0 = peg$f4();
+    } else {
+      peg$currPos = s0;
+      s0 = peg$FAILED;
+    }
+
+    peg$resultsCache[key] = { nextPos: peg$currPos, result: s0 };
+
+    return s0;
+  }
+
+  function peg$parsedelimitedComment() {
+    var s0, s1, s2, s3;
+
+    var key = peg$currPos * 10 + 6;
+    var cached = peg$resultsCache[key];
+
+    if (cached) {
+      peg$currPos = cached.nextPos;
+
+      return cached.result;
+    }
+
+    s0 = peg$currPos;
+    if (input.substr(peg$currPos, 2) === peg$c4) {
+      s1 = peg$c4;
+      peg$currPos += 2;
+    } else {
+      s1 = peg$FAILED;
+      if (peg$silentFails === 0) { peg$fail(peg$e7); }
+    }
+    if (s1 !== peg$FAILED) {
+      s2 = [];
+      if (peg$r2.test(input.charAt(peg$currPos))) {
+        s3 = input.charAt(peg$currPos);
+        peg$currPos++;
+      } else {
+        s3 = peg$FAILED;
+        if (peg$silentFails === 0) { peg$fail(peg$e8); }
+      }
+      while (s3 !== peg$FAILED) {
+        s2.push(s3);
+        if (peg$r2.test(input.charAt(peg$currPos))) {
+          s3 = input.charAt(peg$currPos);
+          peg$currPos++;
+        } else {
+          s3 = peg$FAILED;
+          if (peg$silentFails === 0) { peg$fail(peg$e8); }
+        }
+      }
+      if (input.substr(peg$currPos, 2) === peg$c5) {
+        s3 = peg$c5;
+        peg$currPos += 2;
+      } else {
+        s3 = peg$FAILED;
+        if (peg$silentFails === 0) { peg$fail(peg$e9); }
+      }
+      if (s3 !== peg$FAILED) {
+        peg$savedPos = s0;
+        s0 = peg$f5();
+      } else {
+        peg$currPos = s0;
+        s0 = peg$FAILED;
+      }
+    } else {
+      peg$currPos = s0;
+      s0 = peg$FAILED;
+    }
+
+    peg$resultsCache[key] = { nextPos: peg$currPos, result: s0 };
+
+    return s0;
+  }
+
+  function peg$parse_() {
+    var s0, s1;
+
+    var key = peg$currPos * 10 + 7;
+    var cached = peg$resultsCache[key];
+
+    if (cached) {
+      peg$currPos = cached.nextPos;
+
+      return cached.result;
+    }
+
+    peg$silentFails++;
+    if (peg$r3.test(input.charAt(peg$currPos))) {
+      s0 = input.charAt(peg$currPos);
+      peg$currPos++;
+    } else {
+      s0 = peg$FAILED;
+      if (peg$silentFails === 0) { peg$fail(peg$e11); }
+    }
+    peg$silentFails--;
+    if (s0 === peg$FAILED) {
+      s1 = peg$FAILED;
+      if (peg$silentFails === 0) { peg$fail(peg$e10); }
+    }
+
+    peg$resultsCache[key] = { nextPos: peg$currPos, result: s0 };
+
+    return s0;
+  }
+
+  function peg$parsenewLine() {
+    var s0, s1;
+
+    var key = peg$currPos * 10 + 8;
+    var cached = peg$resultsCache[key];
+
+    if (cached) {
+      peg$currPos = cached.nextPos;
+
+      return cached.result;
+    }
+
+    peg$silentFails++;
+    if (peg$r4.test(input.charAt(peg$currPos))) {
+      s0 = input.charAt(peg$currPos);
+      peg$currPos++;
+    } else {
+      s0 = peg$FAILED;
+      if (peg$silentFails === 0) { peg$fail(peg$e13); }
+    }
+    peg$silentFails--;
+    if (s0 === peg$FAILED) {
+      s1 = peg$FAILED;
+      if (peg$silentFails === 0) { peg$fail(peg$e12); }
+    }
+
+    peg$resultsCache[key] = { nextPos: peg$currPos, result: s0 };
+
+    return s0;
+  }
+
+  function peg$parseany() {
+    var s0;
+
+    var key = peg$currPos * 10 + 9;
+    var cached = peg$resultsCache[key];
+
+    if (cached) {
+      peg$currPos = cached.nextPos;
+
+      return cached.result;
+    }
+
+    if (peg$r5.test(input.charAt(peg$currPos))) {
+      s0 = input.charAt(peg$currPos);
+      peg$currPos++;
+    } else {
+      s0 = peg$FAILED;
+      if (peg$silentFails === 0) { peg$fail(peg$e14); }
+    }
+
+    peg$resultsCache[key] = { nextPos: peg$currPos, result: s0 };
+
+    return s0;
+  }
+
+  peg$result = peg$startRuleFunction();
+
+  if (peg$result !== peg$FAILED && peg$currPos === input.length) {
+    return peg$result;
+  } else {
+    if (peg$result !== peg$FAILED && peg$currPos < input.length) {
+      peg$fail(peg$endExpectation());
+    }
+
+    throw peg$buildStructuredError(
+      peg$maxFailExpected,
+      peg$maxFailPos < input.length ? input.charAt(peg$maxFailPos) : null,
+      peg$maxFailPos < input.length
+        ? peg$computeLocation(peg$maxFailPos, peg$maxFailPos + 1)
+        : peg$computeLocation(peg$maxFailPos, peg$maxFailPos)
+    );
+  }
+}
+
+module.exports = {
+  SyntaxError: peg$SyntaxError,
+  parse: peg$parse
+};
diff --git a/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject_IncludeParser.peggy b/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject_IncludeParser.peggy
new file mode 100644
index 00000000..dc65fac4
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject_IncludeParser.peggy
@@ -0,0 +1,40 @@
+// Includes are at the start of the file, before any other code. 
+// There might be some comments before or between the includes.
+// #include "string"
+// #include "string2"
+
+start
+  = (newLine/_/comment/delimitedComment)* @includes newLine* ignore
+
+includes
+ = head:includeStatement tail:(newLine+ @includeStatement)* 
+ {return [head, ...tail].filter( e => e != '');}
+ / ignore 
+ {return [];}
+
+includeStatement
+  = _* '#include' _* @string _* 
+  / comment
+  / delimitedComment
+
+string 'string'
+  = characters:("'" @([^'])* "'") {return characters.join('');} 
+  / characters:('"' @([^"])* '"') {return characters.join('');}
+
+ignore = (any / newLine / _)*
+
+comment
+= '//'any*
+{ return '';}
+
+delimitedComment  
+= '/*' ([^*]*) '*/'
+{ return '';}
+
+_ "white space"
+  = [ \t]
+
+newLine "newline"
+  = [\n\r]
+  
+any = [^\r\n]
diff --git a/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject_ParseIncludes.res b/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject_ParseIncludes.res
new file mode 100644
index 00000000..f6b17901
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject_ParseIncludes.res
@@ -0,0 +1,15 @@
+@module("./ReducerProject_IncludeParser.js") external parse__: string => array<string> = "parse"
+
+let parseIncludes = (expr: string): result<array<string>, Reducer_ErrorValue.errorValue> =>
+  try {
+    let answer = parse__(expr)
+    // let logEntry = answer->Js.Array2.joinWith(",")
+    // `parseIncludes: ${logEntry} for expr: ${expr}`->Js.log
+    answer->Ok
+  } catch {
+  | Js.Exn.Error(obj) =>
+    RESyntaxError(
+      Belt.Option.getExn(Js.Exn.message(obj)),
+      Reducer_Peggy_Parse.syntaxErrorToLocation(obj)->Some,
+    )->Error
+  }
diff --git a/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject_ProjectAccessors_T.res b/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject_ProjectAccessors_T.res
new file mode 100644
index 00000000..9cc06e8f
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject_ProjectAccessors_T.res
@@ -0,0 +1,40 @@
+module ProjectItemT = ReducerProject_ProjectItem_T
+module Bindings = Reducer_Bindings
+module ExpressionT = Reducer_Expression_T
+module InternalExpressionValue = ReducerInterface_InternalExpressionValue
+
+type states = {mutable continuation: ProjectItemT.continuationArgumentType}
+
+type projectAccessors = {
+  stdLib: Reducer_Bindings.t,
+  environment: ExpressionT.environment,
+  states: states,
+}
+
+type t = projectAccessors
+
+let identityAccessors: t = {
+  // We need the states at the end of the runtime.
+  // Accessors can be modified but states will stay as the same pointer
+  states: {
+    continuation: Bindings.emptyBindings,
+  },
+  stdLib: ReducerInterface_StdLib.internalStdLib,
+  environment: InternalExpressionValue.defaultEnvironment,
+}
+
+let identityAccessorsWithEnvironment = (environment): t => {
+  states: {
+    continuation: Bindings.emptyBindings,
+  },
+  stdLib: ReducerInterface_StdLib.internalStdLib,
+  environment: environment,
+}
+
+// to support change of environment in runtime
+let setEnvironment = (this: t, environment: ExpressionT.environment): t => {
+  {
+    ...this,
+    environment: environment,
+  }
+}
diff --git a/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject_ProjectItem.res b/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject_ProjectItem.res
new file mode 100644
index 00000000..2608e344
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject_ProjectItem.res
@@ -0,0 +1,170 @@
+// TODO: Use actual types instead of aliases in public functions
+// TODO: Use topological sorting to prevent unnecessary runs
+module Bindings = Reducer_Bindings
+module Continuation = ReducerInterface_Value_Continuation
+module ExpressionT = Reducer_Expression_T
+module InternalExpressionValue = ReducerInterface_InternalExpressionValue
+module ProjectAccessorsT = ReducerProject_ProjectAccessors_T
+module ReducerFnT = ReducerProject_ReducerFn_T
+module T = ReducerProject_ProjectItem_T
+
+type projectItem = T.projectItem
+type t = T.t
+
+let emptyItem = T.ProjectItem({
+  source: "",
+  rawParse: None,
+  expression: None,
+  continuation: Bindings.emptyBindings,
+  result: None,
+  continues: [],
+  includes: []->Ok,
+})
+// source -> rawParse -> includes -> expression -> continuation -> result
+
+let getSource = (T.ProjectItem(r)): T.sourceType => r.source
+let getRawParse = (T.ProjectItem(r)): T.rawParseType => r.rawParse
+let getExpression = (T.ProjectItem(r)): T.expressionType => r.expression
+let getContinuation = (T.ProjectItem(r)): T.continuationArgumentType => r.continuation
+let getResult = (T.ProjectItem(r)): T.resultType => r.result
+
+let getContinues = (T.ProjectItem(r)): T.continuesType => r.continues
+let getIncludes = (T.ProjectItem(r)): T.includesType => r.includes
+
+let touchSource = (this: t): t => {
+  let T.ProjectItem(r) = emptyItem
+  T.ProjectItem({
+    ...r,
+    includes: getIncludes(this),
+    continues: getContinues(this),
+    source: getSource(this),
+  })
+}
+let touchRawParse = (this: t): t => {
+  let T.ProjectItem(r) = emptyItem
+  T.ProjectItem({
+    ...r,
+    continues: getContinues(this),
+    source: getSource(this),
+    rawParse: getRawParse(this),
+    includes: getIncludes(this),
+  })
+}
+let touchExpression = (this: t): t => {
+  let T.ProjectItem(r) = emptyItem
+  T.ProjectItem({
+    ...r,
+    continues: getContinues(this),
+    source: getSource(this),
+    rawParse: getRawParse(this),
+    includes: getIncludes(this),
+    expression: getExpression(this),
+  })
+}
+
+let setSource = (T.ProjectItem(r): t, source: T.sourceArgumentType): t =>
+  T.ProjectItem({...r, source: source})->touchSource
+
+let setRawParse = (T.ProjectItem(r): t, rawParse: T.rawParseArgumentType): t =>
+  T.ProjectItem({...r, rawParse: Some(rawParse)})->touchRawParse
+
+let setExpression = (T.ProjectItem(r): t, expression: T.expressionArgumentType): t =>
+  T.ProjectItem({...r, expression: Some(expression)})->touchExpression
+
+let setContinuation = (T.ProjectItem(r): t, continuation: T.continuationArgumentType): t => {
+  T.ProjectItem({...r, continuation: continuation})
+}
+
+let setResult = (T.ProjectItem(r): t, result: T.resultArgumentType): t => T.ProjectItem({
+  ...r,
+  result: Some(result),
+})
+
+let cleanResults = touchExpression
+
+let clean = (this: t): t => {
+  let T.ProjectItem(r) = emptyItem
+  T.ProjectItem({
+    ...r,
+    source: getSource(this),
+    continuation: getContinuation(this),
+    result: getResult(this),
+  })
+}
+
+let getImmediateDependencies = (this: t): T.includesType =>
+  getIncludes(this)->Belt.Result.map(Js.Array2.concat(_, getContinues(this)))
+
+let setContinues = (T.ProjectItem(r): t, continues: array<string>): t =>
+  T.ProjectItem({...r, continues: continues})->touchSource
+let removeContinues = (T.ProjectItem(r): t): t => T.ProjectItem({...r, continues: []})->touchSource
+
+let setIncludes = (T.ProjectItem(r): t, includes: T.includesType): t => T.ProjectItem({
+  ...r,
+  includes: includes,
+})
+
+//TODO: forward parse errors to the user
+let parseIncludes = (this: t): t =>
+  setIncludes(this, getSource(this)->ReducerProject_ParseIncludes.parseIncludes)
+
+let doRawParse = (this: t): T.rawParseArgumentType => this->getSource->Reducer_Peggy_Parse.parse
+
+let rawParse = (this: t): t =>
+  this->getRawParse->E.O2.defaultFn(() => doRawParse(this))->setRawParse(this, _)
+
+let doBuildExpression = (this: t): T.expressionType =>
+  this
+  ->getRawParse
+  ->Belt.Option.map(o => o->Belt.Result.map(r => r->Reducer_Peggy_ToExpression.fromNode))
+
+let buildExpression = (this: t): t => {
+  let withRawParse: t = this->rawParse
+  switch withRawParse->getExpression {
+  | Some(_) => withRawParse
+  | None =>
+    withRawParse
+    ->doBuildExpression
+    ->Belt.Option.map(setExpression(withRawParse, _))
+    ->E.O2.defaultFn(() => withRawParse)
+  }
+}
+
+let wrappedReducer = (
+  rExpression: T.expressionArgumentType,
+  aContinuation: T.continuation,
+  accessors: ProjectAccessorsT.t,
+): T.resultArgumentType => {
+  Belt.Result.flatMap(
+    rExpression,
+    Reducer_Expression.reduceExpressionInProject(_, aContinuation, accessors),
+  )
+}
+
+let doBuildResult = (
+  this: t,
+  aContinuation: T.continuation,
+  accessors: ProjectAccessorsT.t,
+): T.resultType =>
+  this
+  ->getExpression
+  ->Belt.Option.map(
+    Belt.Result.flatMap(
+      _,
+      Reducer_Expression.reduceExpressionInProject(_, aContinuation, accessors),
+    ),
+  )
+
+let buildResult = (this: t, aContinuation: T.continuation, accessors: ProjectAccessorsT.t): t => {
+  let withExpression: t = this->buildExpression
+  switch withExpression->getResult {
+  | Some(_) => withExpression
+  | None =>
+    withExpression
+    ->doBuildResult(aContinuation, accessors)
+    ->Belt.Option.map(setResult(withExpression, _))
+    ->E.O2.defaultFn(() => withExpression)
+  }
+}
+
+let run = buildResult
diff --git a/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject_ProjectItem_T.res b/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject_ProjectItem_T.res
new file mode 100644
index 00000000..6fe251d2
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject_ProjectItem_T.res
@@ -0,0 +1,36 @@
+module Parse = Reducer_Peggy_Parse
+module ExpressionT = Reducer_Expression_T
+module InternalExpressionValue = ReducerInterface_InternalExpressionValue
+open Reducer_ErrorValue
+
+type sourceArgumentType = string
+type sourceType = string
+type rawParseArgumentType = result<Parse.node, errorValue>
+type rawParseType = option<rawParseArgumentType>
+type expressionArgumentType = result<ExpressionT.t, errorValue>
+type expressionType = option<expressionArgumentType>
+type continuation = InternalExpressionValue.nameSpace
+type continuationArgumentType = InternalExpressionValue.nameSpace
+type continuationType = option<continuationArgumentType>
+type continuationResultType = option<result<continuationArgumentType, errorValue>>
+type bindingsArgumentType = InternalExpressionValue.nameSpace
+type bindingsType = option<bindingsArgumentType>
+type resultArgumentType = result<InternalExpressionValue.t, errorValue>
+type resultType = option<resultArgumentType>
+type continuesArgumentType = array<string>
+type continuesType = array<string>
+type includesArgumentType = string
+type includesType = result<array<string>, errorValue>
+
+type projectItem =
+  | ProjectItem({
+      source: sourceType,
+      rawParse: rawParseType,
+      expression: expressionType,
+      continuation: continuationArgumentType,
+      result: resultType,
+      continues: continuesType,
+      includes: includesType,
+    })
+
+type t = projectItem
diff --git a/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject_ReducerFn_T.res b/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject_ReducerFn_T.res
new file mode 100644
index 00000000..0b401fcb
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject_ReducerFn_T.res
@@ -0,0 +1,9 @@
+module ExpressionT = Reducer_Expression_T
+module InternalExpressionValue = ReducerInterface_InternalExpressionValue
+module ProjectAccessorsT = ReducerProject_ProjectAccessors_T
+
+type t = (
+  ExpressionT.t,
+  ExpressionT.bindings,
+  ProjectAccessorsT.t,
+) => result<InternalExpressionValue.t, Reducer_ErrorValue.errorValue>
diff --git a/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject_T.res b/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject_T.res
new file mode 100644
index 00000000..a9411c43
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject_T.res
@@ -0,0 +1,34 @@
+module ProjectItem = ReducerProject_ProjectItem
+module ExpressionT = Reducer_Expression_T
+module ProjectAccessorsT = ReducerProject_ProjectAccessors_T
+
+@genType.opaque
+type project = {"tag": string}
+//re-export
+@genType
+type t = project
+
+module Private = {
+  type internalProject = {
+    "tag": string,
+    "items": Belt.Map.String.t<ProjectItem.t>,
+    "stdLib": Reducer_Bindings.t,
+    "environment": ExpressionT.environment,
+  }
+  type t = internalProject
+
+  @set
+  external setFieldItems: (t, Belt.Map.String.t<ProjectItem.t>) => unit = "items"
+  @set
+  external setFieldStdLib: (t, Reducer_Bindings.t) => unit = "stdLib"
+  @set
+  external setFieldEnvironment: (t, ExpressionT.environment) => unit = "stdLib"
+
+  external castFromInternalProject: t => project = "%identity"
+  external castToInternalProject: project => t = "%identity"
+
+  let getSourceIds = (this: t): array<string> => Belt.Map.String.keysToArray(this["items"])
+
+  let getItem = (this: t, sourceId: string) =>
+    Belt.Map.String.getWithDefault(this["items"], sourceId, ProjectItem.emptyItem)
+}
diff --git a/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject_Topology.res b/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject_Topology.res
new file mode 100644
index 00000000..f23c19c1
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/ReducerProject/ReducerProject_Topology.res
@@ -0,0 +1,72 @@
+module ProjectItem = ReducerProject_ProjectItem
+module T = ReducerProject_T
+type t = T.Private.t
+
+let getSourceIds = T.Private.getSourceIds
+let getItem = T.Private.getItem
+
+let getImmediateDependencies = (this: t, sourceId: string): ProjectItem.T.includesType =>
+  getItem(this, sourceId)->ProjectItem.getImmediateDependencies
+
+type topologicalSortState = (Belt.Map.String.t<bool>, list<string>)
+let rec topologicalSortUtil = (
+  this: t,
+  sourceId: string,
+  state: topologicalSortState,
+): topologicalSortState => {
+  let dependencies = getImmediateDependencies(this, sourceId)->Belt.Result.getWithDefault([])
+  let (visited, stack) = state
+  let myVisited = Belt.Map.String.set(visited, sourceId, true)
+  let (newVisited, newStack) = dependencies->Belt.Array.reduce((myVisited, stack), (
+    (currVisited, currStack),
+    dependency,
+  ) => {
+    if !Belt.Map.String.getWithDefault(currVisited, dependency, false) {
+      topologicalSortUtil(this, dependency, (currVisited, currStack))
+    } else {
+      (currVisited, currStack)
+    }
+  })
+  (newVisited, list{sourceId, ...newStack})
+}
+
+let getTopologicalSort = (this: t): array<string> => {
+  let (_visited, stack) = getSourceIds(this)->Belt.Array.reduce((Belt.Map.String.empty, list{}), (
+    (currVisited, currStack),
+    currId,
+  ) =>
+    if !Belt.Map.String.getWithDefault(currVisited, currId, false) {
+      topologicalSortUtil(this, currId, (currVisited, currStack))
+    } else {
+      (currVisited, currStack)
+    }
+  )
+  Belt.List.reverse(stack)->Belt.List.toArray
+}
+
+let getTopologicalSortFor = (this: t, sourceId) => {
+  let runOrder = getTopologicalSort(this)
+  let index = runOrder->Js.Array2.indexOf(sourceId)
+  let after = Belt.Array.sliceToEnd(runOrder, index + 1)
+  let before = Js.Array2.slice(runOrder, ~start=0, ~end_=index + 1)
+  (before, after)
+}
+
+let getRunOrder = getTopologicalSort
+
+let getRunOrderFor = (this: t, sourceId: string) => {
+  let (runOrder, _) = getTopologicalSortFor(this, sourceId)
+  runOrder
+}
+
+let getDependencies = (this: t, sourceId: string): array<string> => {
+  let runOrder = getRunOrderFor(this, sourceId)
+
+  let _ = Js.Array2.pop(runOrder)
+  runOrder
+}
+
+let getDependents = (this: t, sourceId: string): array<string> => {
+  let (_, dependents) = getTopologicalSortFor(this, sourceId)
+  dependents
+}
diff --git a/packages/squiggle-lang/src/rescript/TypescriptInterface.res b/packages/squiggle-lang/src/rescript/TypescriptInterface.res
index a1f5afe6..428fb0cd 100644
--- a/packages/squiggle-lang/src/rescript/TypescriptInterface.res
+++ b/packages/squiggle-lang/src/rescript/TypescriptInterface.res
@@ -1,3 +1,4 @@
+open ForTS__Types
 /*
 This is meant as a file to contain @genType declarations as needed for Typescript.
 I would ultimately want to have all @genType declarations here, vs. other files, but
@@ -7,59 +8,32 @@ would be preferable.
 The below few seem to work fine. In the future there's definitely more work to do here.
 */
 
-@genType
-type samplingParams = GenericDist.env
+// For backwards compatibility:
+//Alternatives if one wants to keep the old habits
+@genType type samplingParams = environment
+@genType type squiggleValue_Dist = squiggleValue_Distribution //alternative
+@genType type genericDist = squiggleValue_Distribution //alternative
+@genType type sampleSetDist = sampleSetDistribution //alternative
+@genType type symbolicDist = symbolicDistribution //alternative
+@genType type resultDist = result<distribution, distributionError> //alternative
+@genType type resultFloat = result<float, distributionError> //alternative
+@genType type resultString = result<string, distributionError> //alternative
 
 @genType
-type genericDist = DistributionTypes.genericDist
+let makeSampleSetDist: array<float> => result<
+  sampleSetDist,
+  SampleSetDist.sampleSetError,
+> = SampleSetDist.make
 
+//TODO: ForTS Interface module candid
 @genType
-type sampleSetDist = SampleSetDist.t
-
-@genType
-type symbolicDist = SymbolicDistTypes.symbolicDist
-
-@genType
-type distributionError = DistributionTypes.error
-
-@genType
-type resultDist = result<genericDist, distributionError>
-
-@genType
-type resultFloat = result<float, distributionError>
-
-@genType
-type resultString = result<string, distributionError>
-
-@genType
-let makeSampleSetDist = SampleSetDist.make
-
-@genType
-let evaluate = Reducer.evaluate
-
-@genType
-let evaluateUsingOptions = Reducer.evaluateUsingOptions
-
-@genType
-let parse = Reducer_Peggy_Parse.parse
-
-@genType
-let evaluatePartialUsingExternalBindings = Reducer.evaluatePartialUsingExternalBindings
-
-@genType
-type externalBindings = Reducer.externalBindings
-
-@genType
-type expressionValue = ReducerInterface_ExternalExpressionValue.t
-
-@genType
-type recordEV = ReducerInterface_ExternalExpressionValue.record
-
-@genType
-type errorValue = Reducer_ErrorValue.errorValue
-
-@genType
-let toPointSet = GenericDist.toPointSet
+let toPointSet: (
+  squiggleValue_Distribution,
+  ~xyPointLength: int,
+  ~sampleCount: int,
+  ~xSelection: DistributionTypes.DistributionOperation.pointsetXSelection=?,
+  unit,
+) => result<PointSetTypes.pointSetDist, distributionError> = GenericDist.toPointSet
 
 @genType
 type mixedShape = PointSetTypes.mixedShape
@@ -71,31 +45,14 @@ type discreteShape = PointSetTypes.discreteShape
 type continuousShape = PointSetTypes.continuousShape
 
 @genType
-let errorValueToString = Reducer_ErrorValue.errorToString
+let distributionErrorToString = ForTS_Distribution_Error.toString
 
 @genType
-let distributionErrorToString = DistributionTypes.Error.toString
+let defaultSamplingEnv = ForTS_Distribution.defaultEnvironment
 
-@genType
-type lambdaValue = ReducerInterface_ExternalExpressionValue.lambdaValue
+// Umur: opaqe types
+// @genType
+// type declarationArg = Declaration.arg
 
-@genType
-type lambdaDeclaration = ReducerInterface_ExternalExpressionValue.lambdaDeclaration
-
-@genType
-let defaultSamplingEnv = DistributionOperation.defaultEnv
-
-@genType
-type environment = ReducerInterface_ExternalExpressionValue.environment
-
-@genType
-let defaultEnvironment = ReducerInterface_ExternalExpressionValue.defaultEnvironment
-
-@genType
-let foreignFunctionInterface = Reducer.foreignFunctionInterface
-
-@genType
-type declarationArg = Declaration.arg
-
-@genType
-type declaration<'a> = Declaration.declaration<'a>
+// @genType
+// type declaration<'a> = Declaration.declaration<'a>