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
new file mode 100644
index 00000000..a106a188
--- /dev/null
+++ b/packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_ToExpression_void_test.res
@@ -0,0 +1,20 @@
+open Jest
+open Reducer_Peggy_TestHelpers
+
+describe("Peggy void", () => {
+  //literal
+  testToExpression("()", "{()}", ~v="()", ())
+  testToExpression(
+    "fn()=1",
+    "{(:$_let_$ :fn (:$$_lambda_$$ [_] {1}))}",
+    ~v="@{fn: lambda(_=>internal code)}",
+    (),
+  )
+  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)}",
+    (),
+  )
+})
diff --git a/packages/squiggle-lang/package.json b/packages/squiggle-lang/package.json
index 75531a28..1c4ba3ac 100644
--- a/packages/squiggle-lang/package.json
+++ b/packages/squiggle-lang/package.json
@@ -31,6 +31,7 @@
     "format:prettier": "prettier --write .",
     "format": "yarn format:rescript && yarn format:prettier",
     "prepack": "yarn build && yarn test && yarn bundle",
+    "all:rescript": "yarn build:rescript && yarn test:rescript && yarn format:rescript",
     "all": "yarn build && yarn bundle && yarn test"
   },
   "keywords": [
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_ExpressionBuilder.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_ExpressionBuilder.res
index 14ffe685..9cc25725 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_ExpressionBuilder.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_ExpressionBuilder.res
@@ -82,3 +82,5 @@ let eIdentifier = (name: string): expression =>
 
 let eTypeIdentifier = (name: string): expression =>
   name->BInternalExpressionValue.IEvTypeIdentifier->BExpressionT.EValue
+
+let eVoid: expression = BInternalExpressionValue.IEvVoid->BExpressionT.EValue
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 f4acd4a3..befda109 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
@@ -5,13 +5,12 @@
 }}
 
 start
-  // = _nl start:typeExpression _nl finalComment?  {return start}
   = _nl start:outerBlock _nl finalComment?  {return start}
 
 zeroOMoreArgumentsBlockOrExpression = innerBlockOrExpression / lambda
 
 outerBlock 
-	= statements:array_statements  finalExpression: (statementSeparator @expression)?
+  = statements:array_statements  finalExpression: (statementSeparator @expression)?
     { if (finalExpression != null) { statements.push(finalExpression) }
         return h.nodeBlock(statements) }
   / finalExpression: expression
@@ -24,25 +23,31 @@ innerBlockOrExpression
 
 quotedInnerBlock  
   = '{' _nl statements:array_statements  finalExpression: (statementSeparator @expression)  _nl '}'
-	  { statements.push(finalExpression) 
-    	return h.nodeBlock(statements) }
+      { statements.push(finalExpression) 
+        return h.nodeBlock(statements) }
   / '{' _nl finalExpression: expression  _nl '}'
-	  { return h.nodeBlock([finalExpression]) }
+      { return h.nodeBlock([finalExpression]) }
 
 array_statements
   = head:statement tail:(statementSeparator @array_statements )
     { return [head, ...tail] }
   / head:statement
-  	{ return [head] }
+      { return [head] }
 
 statement 
   = letStatement
   / defunStatement
   / typeStatement
+  / voidStatement
+
+voidStatement 
+  = "call" _nl value:zeroOMoreArgumentsBlockOrExpression
+    { var variable = h.nodeIdentifier("_", location());
+      return h.nodeLetStatement(variable, value); }
 
 letStatement 
   = variable:identifier _ assignmentOp _nl value:zeroOMoreArgumentsBlockOrExpression
-  { return h.nodeLetStatement(variable, value) }
+    { return h.nodeLetStatement(variable, value) }
 
 defunStatement
   = variable:identifier '(' _nl args:array_parameters _nl ')' _ assignmentOp _nl body:innerBlockOrExpression
@@ -53,13 +58,15 @@ defunStatement
 
 array_parameters 
   = head:dollarIdentifier tail:(_ ',' _nl @dollarIdentifier)* 
-  { return [head, ...tail]; }
+    { return [head, ...tail]; }
+  / ""
+    { return [h.nodeIdentifier("_", location())]; }
 
 expression = ifthenelse / ternary / logicalAdditive
 
 ifthenelse 
   = 'if' __nl condition:logicalAdditive 
-  	__nl 'then' __nl trueExpression:innerBlockOrExpression 
+      __nl 'then' __nl trueExpression:innerBlockOrExpression 
     __nl 'else' __nl falseExpression:(ifthenelse/innerBlockOrExpression)
     { return h.nodeTernary(condition, trueExpression, falseExpression) }
   
@@ -88,8 +95,8 @@ equality
   = left:relational _ operator:equalityOp _nl right:relational 
   { return h.makeFunctionCall(h.toFunction[operator], [left, right])}
   / relational  
- 
- equalityOp "operator" = '=='/'!='
+  
+  equalityOp "operator" = '=='/'!='
 
 relational
   = left:additive _ operator:relationalOp _nl right:additive 
@@ -172,19 +179,25 @@ collectionElement
     array_functionArguments 
       = head:expression tail:(_ ',' _nl @expression)* 
       { return [head, ...tail]; }
+  / ""
+      {return [h.nodeVoid()];}
 
 atom
   = '(' _nl expression:expression _nl ')' {return expression}
   / basicValue
 
 basicValue = valueConstructor / basicLiteral
- 
+
 basicLiteral
   = string
   / number
   / boolean
   / dollarIdentifierWithModule
   / dollarIdentifier
+  / voidLiteral
+
+voidLiteral 'void'
+  = "()" {return h.nodeVoid();}
 
 dollarIdentifierWithModule 'identifier'
   = head:$moduleIdentifier 
@@ -195,7 +208,7 @@ dollarIdentifierWithModule 'identifier'
     modifiers.unshift(head)
     modifiers.push(final)
     let modifiedIdentifier = modifiers.join('.')
-    return h.nodeIdentifier(modifiedIdentifier)
+    return h.nodeIdentifier(modifiedIdentifier, location())
   }
 
 identifier 'identifier'
@@ -232,8 +245,8 @@ float 'float'
   = $(((d+ "\." d*) / ("\." d+)) floatExponent? / d+ floatExponent)
   { return h.nodeFloat(parseFloat(text()))} 
 
-	floatExponent = [e]i '-'? d+
-	d = [0-9]
+    floatExponent = [e]i '-'? d+
+    d = [0-9]
     
 boolean 'boolean'
   = ('true'/'false') 
@@ -247,10 +260,10 @@ valueConstructor
 
 lambda  
   = '{' _nl '|' _nl args:array_parameters _nl '|' _nl statements:array_statements  finalExpression: (statementSeparator @expression)  _nl '}'
-	  { statements.push(finalExpression) 
-    	return h.nodeLambda(args, h.nodeBlock(statements)) }
+      { statements.push(finalExpression) 
+        return h.nodeLambda(args, h.nodeBlock(statements)) }
   / '{' _nl '|' _nl args:array_parameters _nl '|' _nl finalExpression: expression  _nl '}'
-	  { return h.nodeLambda(args, h.nodeBlock([finalExpression])) }
+      { return h.nodeLambda(args, h.nodeBlock([finalExpression])) }
 
 arrayConstructor 'array'
   = '[' _nl ']'
@@ -289,7 +302,7 @@ __nl 'whitespace or newline'
   = (whiteSpaceCharactersOrComment / commentOrNewLine )+
 
 statementSeparator 'statement separator'
-	= _ (';'/ commentOrNewLine)+ _nl
+    = _ (';'/ commentOrNewLine)+ _nl
 
   commentOrNewLine = finalComment? newLine 
 
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 a38c66e9..193cb893 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
@@ -34,6 +34,7 @@ type nodeModuleIdentifier = {...node, "value": string}
 type nodeString = {...node, "value": string}
 type nodeTernary = {...node, "condition": node, "trueExpression": node, "falseExpression": node}
 type nodeTypeIdentifier = {...node, "value": string}
+type nodeVoid = node
 
 type peggyNode =
   | PgNodeBlock(nodeBlock)
@@ -50,6 +51,7 @@ type peggyNode =
   | PgNodeString(nodeString)
   | PgNodeTernary(nodeTernary)
   | PgNodeTypeIdentifier(nodeTypeIdentifier)
+  | PgNodeVoid(nodeVoid)
 
 external castNodeBlock: node => nodeBlock = "%identity"
 external castNodeBoolean: node => nodeBoolean = "%identity"
@@ -65,6 +67,7 @@ external castNodeModuleIdentifier: node => nodeModuleIdentifier = "%identity"
 external castNodeString: node => nodeString = "%identity"
 external castNodeTernary: node => nodeTernary = "%identity"
 external castNodeTypeIdentifier: node => nodeTypeIdentifier = "%identity"
+external castNodeVoid: node => nodeVoid = "%identity"
 
 exception UnsupportedPeggyNodeType(string) // This should never happen; programming error
 let castNodeType = (node: node) =>
@@ -83,6 +86,7 @@ let castNodeType = (node: node) =>
   | "String" => node->castNodeString->PgNodeString
   | "Ternary" => node->castNodeTernary->PgNodeTernary
   | "TypeIdentifier" => node->castNodeTypeIdentifier->PgNodeTypeIdentifier
+  | "Void" => node->castNodeVoid->PgNodeVoid
   | _ => raise(UnsupportedPeggyNodeType(node["type"]))
   }
 
@@ -116,6 +120,7 @@ let rec pgToString = (peggyNode: peggyNode): string => {
     " " ++
     toString(node["falseExpression"]) ++ ")"
   | PgNodeTypeIdentifier(node) => `#${node["value"]}`
+  | PgNodeVoid(_node) => "()"
   }
 }
 and toString = (node: node): string => node->castNodeType->pgToString
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_ToExpression.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_ToExpression.res
index 6e04a55d..73247a8e 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_ToExpression.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_ToExpression.res
@@ -48,5 +48,6 @@ let rec fromNode = (node: Parse.node): expression => {
     )
   | PgNodeTypeIdentifier(nodeTypeIdentifier) =>
     ExpressionBuilder.eTypeIdentifier(nodeTypeIdentifier["value"])
+  | PgNodeVoid(_) => ExpressionBuilder.eVoid
   }
 }
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/helpers.ts b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/helpers.ts
index 57b85f9e..94975233 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/helpers.ts
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/helpers.ts
@@ -213,3 +213,7 @@ export function nodeTernary(
 export function nodeTypeIdentifier(typeValue: string) {
   return { type: "TypeIdentifier", value: typeValue };
 }
+
+export function nodeVoid() {
+  return { type: "Void" };
+}
diff --git a/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_ExternalExpressionValue.res b/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_ExternalExpressionValue.res
index b21ba3c6..a4d6e713 100644
--- a/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_ExternalExpressionValue.res
+++ b/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_ExternalExpressionValue.res
@@ -25,6 +25,7 @@ type rec externalExpressionValue =
   | EvTypeIdentifier(string)
   | EvModule(record)
   | EvType(record)
+  | EvVoid
 and record = Js.Dict.t<externalExpressionValue>
 and externalBindings = record
 and lambdaValue = {
@@ -63,6 +64,7 @@ let rec toString = aValue =>
   | EvTimeDuration(t) => DateTime.Duration.toString(t)
   | EvType(t) => `type${t->toStringRecord}`
   | EvTypeIdentifier(id) => `#${id}`
+  | EvVoid => `()`
   }
 and toStringRecord = aRecord => {
   let pairs =
diff --git a/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_InternalExpressionValue.res b/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_InternalExpressionValue.res
index 4523b02a..39019fba 100644
--- a/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_InternalExpressionValue.res
+++ b/packages/squiggle-lang/src/rescript/ReducerInterface/ReducerInterface_InternalExpressionValue.res
@@ -23,6 +23,7 @@ type rec t =
   | IEvTimeDuration(float)
   | IEvType(map)
   | IEvTypeIdentifier(string)
+  | IEvVoid
 and map = Belt.Map.String.t<t>
 and nameSpace = NameSpace(Belt.Map.String.t<t>)
 and lambdaValue = {
@@ -60,6 +61,7 @@ let rec toString = aValue =>
   | IEvType(aMap) => aMap->toStringMap
   | IEvTimeDuration(t) => DateTime.Duration.toString(t)
   | IEvTypeIdentifier(id) => `#${id}`
+  | IEvVoid => `()`
   }
 and toStringMap = aMap => {
   let pairs =
@@ -92,6 +94,7 @@ let toStringWithType = aValue =>
   | IEvTimeDuration(_) => `Date::${toString(aValue)}`
   | IEvType(_) => `Type::${toString(aValue)}`
   | IEvTypeIdentifier(_) => `TypeIdentifier::${toString(aValue)}`
+  | IEvVoid => `Void`
   }
 
 let argsToString = (args: array<t>): string => {
@@ -135,6 +138,7 @@ type internalExpressionValueType =
   | EvtTimeDuration
   | EvtType
   | EvtTypeIdentifier
+  | EvtVoid
 
 type functionCallSignature = CallSignature(string, array<internalExpressionValueType>)
 type functionDefinitionSignature =
@@ -158,6 +162,7 @@ let valueToValueType = value =>
   | IEvTimeDuration(_) => EvtTimeDuration
   | IEvType(_) => EvtType
   | IEvTypeIdentifier(_) => EvtTypeIdentifier
+  | IEvVoid => EvtVoid
   }
 
 let functionCallToCallSignature = (functionCall: functionCall): functionCallSignature => {
@@ -183,6 +188,7 @@ let valueTypeToString = (valueType: internalExpressionValueType): string =>
   | EvtTimeDuration => `Duration`
   | EvtType => `Type`
   | EvtTypeIdentifier => `TypeIdentifier`
+  | EvtVoid => `Void`
   }
 
 let functionCallSignatureToString = (functionCallSignature: functionCallSignature): string => {
@@ -212,6 +218,7 @@ let rec toExternal = (iev: t): ExternalExpressionValue.t => {
   | IEvType(v) => v->mapToExternal->EvType
   | IEvTypeIdentifier(v) => EvTypeIdentifier(v)
   | IEvBindings(v) => v->nameSpaceToTypeScriptBindings->EvModule
+  | IEvVoid => EvVoid
   }
 }
 and mapToExternal = v =>
@@ -251,6 +258,7 @@ let rec toInternal = (ev: ExternalExpressionValue.t): t => {
   | EvTimeDuration(v) => IEvTimeDuration(v)
   | EvType(v) => v->recordToInternal->IEvType
   | EvTypeIdentifier(v) => IEvTypeIdentifier(v)
+  | EvVoid => IEvVoid
   }
 }
 and recordToInternal = v =>