From cbc2b73b205dc8eeb3be4e705f0ae3439843c68a Mon Sep 17 00:00:00 2001
From: Umur Ozkul <umur@hightechmind.io>
Date: Mon, 25 Apr 2022 16:01:02 +0200
Subject: [PATCH] Evaluate ternary operator (tested)

---
 .../Reducer/Reducer_ternaryOperator_test.res    |  2 +-
 .../Reducer_Dispatch_BuiltInMacros.res          | 17 +++++++++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/packages/squiggle-lang/__tests__/Reducer/Reducer_ternaryOperator_test.res b/packages/squiggle-lang/__tests__/Reducer/Reducer_ternaryOperator_test.res
index b04944b9..940ff3c7 100644
--- a/packages/squiggle-lang/__tests__/Reducer/Reducer_ternaryOperator_test.res
+++ b/packages/squiggle-lang/__tests__/Reducer/Reducer_ternaryOperator_test.res
@@ -6,7 +6,7 @@ describe("Parse ternary operator", () => {
   testParseToBe("2>1 ? 'YES' : 'NO'", "Ok((:$$ternary (:larger 2 1) 'YES' 'NO'))")
 })
 
-Skip.describe("Evaluate ternary operator", () => {
+describe("Evaluate ternary operator", () => {
   testEvalToBe("true ? 'YES' : 'NO'", "Ok('YES')")
   testEvalToBe("false ? 'YES' : 'NO'", "Ok('NO')")
 })
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 5facc9e7..7174a5f7 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
@@ -158,6 +158,21 @@ let dispatchMacroCall = (
     | _ => replaceSymbols(expression, bindings)
     }
 
+  let doTernary = (
+    conditionExpr: expression,
+    trueExpression: expression,
+    falseExpression: expression,
+    bindings: ExpressionT.bindings,
+  ) => {
+    let rCondition = conditionExpr->reduceExpression(bindings)
+    rCondition->Result.flatMap(condition =>
+      switch condition {
+      | EvBool(true) => trueExpression->Ok
+      | EvBool(false) => falseExpression->Ok
+      | _ => RESyntaxError("Boolean value expected for conditional")->Error
+      }
+    )
+  }
   switch list {
   | list{ExpressionT.EValue(EvCall("$$bindings"))} => bindings->ExpressionT.EBindings->Ok
 
@@ -173,6 +188,8 @@ let dispatchMacroCall = (
       expression,
     } =>
     doBindExpression(expression, bindings)
+  | list{ExpressionT.EValue(EvCall("$$ternary")), conditionExpr, trueExpr, falseExpr} =>
+    doTernary(conditionExpr, trueExpr, falseExpr, bindings)
   | _ => list->ExpressionT.EList->Ok
   }
 }