inspect and inspect with label (tested)

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

@@ -0,0 +1,12 @@
+open Jest
+open Reducer_TestHelpers
+
+/*
+    You can wrap around any expression with inspect(expr) to log the value of that expression.
+    This is useful for debugging. inspect(expr) returns the value of expr, but also prints it out.
+    There is a second version of inspect that takes a label, which will print out the label and the value.
+*/
+describe("Debugging", () => {
+    testEvalToBe("inspect(1)", "Ok(1)")
+    testEvalToBe("inspect(1, \"one\")", "Ok(1)")
+})

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

@@ -43,16 +43,25 @@ let callInternal = (call: functionCall): result<'b, errorValue> => {
     | None => RERecordPropertyNotFound("Record property not found", sIndex)->Error
     }
 
+  let inspect = (value: expressionValue) => {
+    Js.log(`${value->toString}`)
+    value->Ok
+  }
+
+  let inspectLabel = (value: expressionValue, label: string) => {
+    Js.log(`${label}: ${value->toString}`)
+    value->Ok
+  }
+
   switch call {
-  // | ("$constructRecord", pairArray)
-  // | ("$atIndex", [EvArray(anArray), EvNumber(fIndex)]) => arrayAtIndex(anArray, fIndex)
-  // | ("$atIndex", [EvRecord(aRecord), EvString(sIndex)]) => recordAtIndex(aRecord, sIndex)
-  | ("$constructRecord", [EvArray(arrayOfPairs)]) => constructRecord(arrayOfPairs)
   | ("$atIndex", [EvArray(aValueArray), EvArray([EvNumber(fIndex)])]) =>
     arrayAtIndex(aValueArray, fIndex)
   | ("$atIndex", [EvRecord(dict), EvArray([EvString(sIndex)])]) => recordAtIndex(dict, sIndex)
   | ("$atIndex", [obj, index]) =>
     (toStringWithType(obj) ++ "??~~~~" ++ toStringWithType(index))->EvString->Ok
+  | ("$constructRecord", [EvArray(arrayOfPairs)]) => constructRecord(arrayOfPairs)
+  | ("inspect", [value, EvString(label)]) => inspectLabel(value, label)
+  | ("inspect", [value]) => inspect(value)
   | call => callMathJs(call)
   }
 }