From 9e41f0399f32670de196468ec17659aa73cd47e7 Mon Sep 17 00:00:00 2001
From: Umur Ozkul <umur@hightechmind.io>
Date: Mon, 2 May 2022 15:47:35 +0200
Subject: [PATCH] RENotAFunction

---
 .../__tests__/Reducer/Reducer_functionTricks_test.res  |  4 ++--
 .../src/rescript/Reducer/Reducer_ErrorValue.res        |  2 ++
 .../Reducer_Expression/Reducer_Expression_Bindings.res | 10 +++++++++-
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/packages/squiggle-lang/__tests__/Reducer/Reducer_functionTricks_test.res b/packages/squiggle-lang/__tests__/Reducer/Reducer_functionTricks_test.res
index 9e3e25c2..b21b14cd 100644
--- a/packages/squiggle-lang/__tests__/Reducer/Reducer_functionTricks_test.res
+++ b/packages/squiggle-lang/__tests__/Reducer/Reducer_functionTricks_test.res
@@ -34,8 +34,8 @@ describe("function trics", () => {
   testEvalToBe("f(x)=x(y); f(f)", "Error(y is not defined)")
   testEvalToBe("f(x)=x; f(f)", "Ok(lambda(x=>internal code))")
   testEvalToBe("f(x)=x(y); f(z)", "Error(z is not defined)")
-  testEvalToBe("f(x)=x(y); f(2)", "Error(y is not defined)")
-  MySkip.testEvalToBe("f(x)=x(1); f(2)", "????")
+  testEvalToBe("f(x)=x(y); f(2)", "Error(2 is not a function)")
+  testEvalToBe("f(x)=x(1); f(2)", "Error(2 is not a function)")
   MySkip.testEvalToBe("f(x)=f(y)=2; f(2)", "????") //prevent multiple assignment
   MySkip.testEvalToBe("f(x)=x+1; g(x)=f(x)+1;g(2)", "????") //TODO: f is not found
   MySkip.testEvalToBe("y=2;g(x)=y+1;g(2)", "????") //TODO : y is not found
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_ErrorValue.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_ErrorValue.res
index b9eabe28..7964c3a4 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_ErrorValue.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_ErrorValue.res
@@ -8,6 +8,7 @@ type errorValue =
   | REFunctionExpected(string)
   | REJavaScriptExn(option<string>, option<string>) // Javascript Exception
   | REMacroNotFound(string)
+  | RENotAFunction(string)
   | RERecordPropertyNotFound(string, string)
   | RESymbolNotFound(string)
   | RESyntaxError(string)
@@ -40,6 +41,7 @@ let errorToString = err =>
       answer
     }
   | REMacroNotFound(macro) => `Macro not found: ${macro}`
+  | RENotAFunction(valueString) => `${valueString} is not a function`
   | RERecordPropertyNotFound(msg, index) => `${msg}: ${index}`
   | RESymbolNotFound(symbolName) => `${symbolName} is not defined`
   | RESyntaxError(desc) => `Syntax Error: ${desc}`
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_Bindings.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_Bindings.res
index add7f614..830e93ba 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_Bindings.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_Bindings.res
@@ -1,3 +1,4 @@
+module ErrorValue = Reducer_ErrorValue
 module ExpressionT = Reducer_Expression_T
 module ExpressionValue = ReducerInterface.ExpressionValue
 module Result = Belt.Result
@@ -67,7 +68,14 @@ and replaceSymbolsOnExpressionList = (bindings, list) => {
 }
 and replaceSymbolOnValue = (bindings, evValue: expressionValue) =>
   switch evValue {
-  | EvSymbol(symbol) | EvCall(symbol) =>
+  | EvSymbol(symbol) =>
     Belt.Map.String.getWithDefault(bindings, symbol, evValue)->Ok
+  | EvCall(symbol) =>
+    Belt.Map.String.getWithDefault(bindings, symbol, evValue)->checkIfCallable
   | _ => evValue->Ok
   }
+and checkIfCallable = (evValue: expressionValue) =>
+  switch evValue {
+  | EvCall(_) | EvLambda(_) => evValue->Ok
+  | _ => ErrorValue.RENotAFunction(ExpressionValue.toString(evValue))->Error
+  }