ternary operator (tested)

packages/squiggle-lang/__tests__/Reducer/Reducer_ternaryOperator_test.res

@@ -1,12 +1,14 @@
 open Jest
 open Reducer_TestHelpers
 
-Skip.describe("Parse ternary operator", () => {
-  testParseToBe("true ? 'YES' : 'NO'", "Ok('YES')")
-  testParseToBe("false ? 'YES' : 'NO'", "Ok('NO')")
+describe("Parse ternary operator", () => {
+  testParseToBe("true ? 'YES' : 'NO'", "Ok((:$$block (:$$ternary true 'YES' 'NO')))")
 })
 
-Skip.describe("Evaluate ternary operator", () => {
+describe("Evaluate ternary operator", () => {
   testEvalToBe("true ? 'YES' : 'NO'", "Ok('YES')")
   testEvalToBe("false ? 'YES' : 'NO'", "Ok('NO')")
+  testEvalToBe("2 > 1 ? 'YES' : 'NO'", "Ok('YES')")
+  testEvalToBe("2 <= 1 ? 'YES' : 'NO'", "Ok('NO')")
+  testEvalToBe("1+1 ? 'YES' : 'NO'", "Error(Expected type: Boolean)")
 })

packages/squiggle-lang/src/rescript/Reducer/Reducer.res

@@ -19,12 +19,7 @@ let foreignFunctionInterface = (
   argArray: array<expressionValue>,
   environment: ExpressionValue.environment,
 ) => {
-  Lambda.foreignFunctionInterface(
-    lambdaValue,
-    argArray,
-    environment,
-    Expression.reduceExpression,
-  )
+  Lambda.foreignFunctionInterface(lambdaValue, argArray, environment, Expression.reduceExpression)
 }
 
 let defaultEnvironment = ExpressionValue.defaultEnvironment

packages/squiggle-lang/src/rescript/Reducer/Reducer.resi

@@ -12,7 +12,6 @@ type externalBindings = ReducerInterface_ExpressionValue.externalBindings
 @genType
 type lambdaValue = ReducerInterface_ExpressionValue.lambdaValue
 
-
 @genType
 let evaluateUsingOptions: (
   ~environment: option<QuriSquiggleLang.ReducerInterface_ExpressionValue.environment>,

packages/squiggle-lang/src/rescript/Reducer/Reducer_Dispatch/Reducer_Dispatch_BuiltInMacros.res

@@ -132,6 +132,23 @@ let dispatchMacroCall = (
       eLambda(parameters, bindings->Bindings.toExternalBindings, lambdaDefinition),
     )->Ok
 
+  let doTernary = (
+    condition: expression,
+    ifTrue: expression,
+    ifFalse: expression,
+    bindings: ExpressionT.bindings,
+    environment,
+  ): result<expressionWithContext, errorValue> => {
+    let rCondition = reduceExpression(condition, bindings, environment)
+    rCondition->Result.flatMap(conditionValue =>
+      switch conditionValue {
+      | ExpressionValue.EvBool(false) => ExpressionWithContext.noContext(ifFalse)->Ok
+      | ExpressionValue.EvBool(true) => ExpressionWithContext.noContext(ifTrue)->Ok
+      | _ => REExpectedType("Boolean")->Error
+      }
+    )
+  }
+
   let expandExpressionList = (aList, bindings: ExpressionT.bindings, environment): result<
     expressionWithContext,
     errorValue,
@@ -162,6 +179,8 @@ let dispatchMacroCall = (
         lambdaDefinition,
       } =>
       doLambdaDefinition(bindings, parameters, lambdaDefinition)
+    | list{ExpressionT.EValue(EvCall("$$ternary")), condition, ifTrue, ifFalse} =>
+      doTernary(condition, ifTrue, ifFalse, bindings, environment)
     | _ => ExpressionWithContext.noContext(ExpressionT.EList(aList))->Ok
     }
 

packages/squiggle-lang/src/rescript/Reducer/Reducer_ErrorValue.res

@@ -13,6 +13,7 @@ type errorValue =
   | RESymbolNotFound(string)
   | RESyntaxError(string)
   | RETodo(string) // To do
+  | REExpectedType(string)
 
 type t = errorValue
 
@@ -46,4 +47,5 @@ let errorToString = err =>
   | RESymbolNotFound(symbolName) => `${symbolName} is not defined`
   | RESyntaxError(desc) => `Syntax Error: ${desc}`
   | RETodo(msg) => `TODO: ${msg}`
+  | REExpectedType(typeName) => `Expected type: ${typeName}`
   }