Very simple implementation of pointset mapY

packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_Pointset.res

@@ -23,6 +23,31 @@ let inputsTodist = (inputs: array<FunctionRegistry_Core.frValue>, makeDist) => {
   expressionValue
 }
 
+module Internal = {
+  type t = PointSetDist.t
+
+  let toType = (r): result<
+    ReducerInterface_InternalExpressionValue.t,
+    Reducer_ErrorValue.errorValue,
+  > =>
+    switch r {
+    | Ok(r) => Ok(Wrappers.evDistribution(PointSet(r)))
+    | Error(err) => Error(REOperationError(err))
+    }
+
+  let doLambdaCall = (aLambdaValue, list, environment, reducer) =>
+    switch Reducer_Expression_Lambda.doLambdaCall(aLambdaValue, list, environment, reducer) {
+    | Ok(IEvNumber(f)) => Ok(f)
+    | _ => Error(Operation.SampleMapNeedsNtoNFunction)
+    }
+
+  let mapY = (pointSetDist: t, aLambdaValue, env, reducer) => {
+    let fn = r => doLambdaCall(aLambdaValue, list{IEvNumber(r)}, env, reducer)
+    let foo = PointSetDist.T.mapYResult(~fn, pointSetDist)
+    foo->toType
+  }
+}
+
 let library = [
   Function.make(
     ~name="fromDist",
@@ -53,6 +78,26 @@ let library = [
     ],
     (),
   ),
+  Function.make(
+    ~name="mapY",
+    ~nameSpace,
+    ~requiresNamespace=true,
+    ~examples=[`PointSet.mapY(mx(normal(5,2)), {|x| x + 1})`],
+    ~output=ReducerInterface_InternalExpressionValue.EvtDistribution,
+    ~definitions=[
+      FnDefinition.make(
+        ~name="mapY",
+        ~inputs=[FRTypeDist, FRTypeLambda],
+        ~run=(inputs, _, env, reducer) =>
+          switch inputs {
+          | [IEvDistribution(PointSet(dist)), IEvLambda(lambda)] => Internal.mapY(dist, lambda, env, reducer)->E.R2.errMap(_ => "")
+          | _ => Error(impossibleError)
+          },
+        (),
+      ),
+    ],
+    (),
+  ),
   Function.make(
     ~name="makeContinuous",
     ~nameSpace,