Simple additions of first, last, cumulative sum, diff

packages/squiggle-lang/src/rescript/FunctionRegistry/FunctionRegistry_Helpers.res

@@ -236,7 +236,16 @@ module OneArgDist = {
 module ArrayNumberDist = {
   let make = (name, fn) => {
     FnDefinition.make(~name, ~inputs=[FRTypeArray(FRTypeNumber)], ~run=(inputs, _) =>
-      Prepare.ToTypedArray.numbers(inputs)->E.R2.fmap(fn)
+      Prepare.ToTypedArray.numbers(inputs)
+      ->E.R.bind(r => E.A.length(r) === 0 ? Error("List is empty") : Ok(r))
+      ->E.R.bind(fn)
+    )
+  }
+  let make2 = (name, fn) => {
+    FnDefinition.make(~name, ~inputs=[FRTypeArray(FRTypeAny)], ~run=(inputs, _) =>
+      Prepare.ToTypedArray.numbers(inputs)
+      ->E.R.bind(r => E.A.length(r) === 0 ? Error("List is empty") : Ok(r))
+      ->E.R.bind(fn)
     )
   }
 }

packages/squiggle-lang/src/rescript/FunctionRegistry/FunctionRegistry_Library.res

@@ -147,41 +147,63 @@ let registry = [
   Function.make(~name="Round", ~definitions=[NumberToNumber.make("round", Js.Math.round)]),
   Function.make(
     ~name="Sum",
-    ~definitions=[ArrayNumberDist.make("sum", r => r->E.A.Floats.sum->Wrappers.evNumber)],
+    ~definitions=[ArrayNumberDist.make("sum", r => r->E.A.Floats.sum->Wrappers.evNumber->Ok)],
   ),
   Function.make(
     ~name="Product",
-    ~definitions=[ArrayNumberDist.make("product", r => r->E.A.Floats.product->Wrappers.evNumber)],
+    ~definitions=[
+      ArrayNumberDist.make("product", r => r->E.A.Floats.product->Wrappers.evNumber->Ok),
+    ],
   ),
   Function.make(
     ~name="Min",
-    ~definitions=[ArrayNumberDist.make("min", r => r->E.A.Floats.min->Wrappers.evNumber)],
+    ~definitions=[ArrayNumberDist.make("min", r => r->E.A.Floats.min->Wrappers.evNumber->Ok)],
   ),
   Function.make(
     ~name="Max",
-    ~definitions=[ArrayNumberDist.make("max", r => r->E.A.Floats.max->Wrappers.evNumber)],
+    ~definitions=[ArrayNumberDist.make("max", r => r->E.A.Floats.max->Wrappers.evNumber->Ok)],
   ),
   Function.make(
     ~name="Mean",
-    ~definitions=[ArrayNumberDist.make("mean", r => r->E.A.Floats.mean->Wrappers.evNumber)],
+    ~definitions=[ArrayNumberDist.make("mean", r => r->E.A.Floats.mean->Wrappers.evNumber->Ok)],
   ),
   Function.make(
     ~name="Geometric Mean",
-    ~definitions=[ArrayNumberDist.make("geomean", r => r->E.A.Floats.geomean->Wrappers.evNumber)],
+    ~definitions=[
+      ArrayNumberDist.make("geomean", r => r->E.A.Floats.geomean->Wrappers.evNumber->Ok),
+    ],
   ),
   Function.make(
     ~name="Standard Deviation",
-    ~definitions=[ArrayNumberDist.make("stdev", r => r->E.A.Floats.stdev->Wrappers.evNumber)],
+    ~definitions=[ArrayNumberDist.make("stdev", r => r->E.A.Floats.stdev->Wrappers.evNumber->Ok)],
   ),
   Function.make(
     ~name="Variance",
-    ~definitions=[ArrayNumberDist.make("variance", r => r->E.A.Floats.stdev->Wrappers.evNumber)],
+    ~definitions=[
+      ArrayNumberDist.make("variance", r => r->E.A.Floats.stdev->Wrappers.evNumber->Ok),
+    ],
+  ),
+  Function.make(
+    ~name="First",
+    ~definitions=[
+      ArrayNumberDist.make2("first", r =>
+        r->E.A.first |> E.O.toResult(impossibleError) |> E.R.fmap(Wrappers.evNumber)
+      ),
+    ],
+  ),
+  Function.make(
+    ~name="Last",
+    ~definitions=[
+      ArrayNumberDist.make2("last", r =>
+        r->E.A.last |> E.O.toResult(impossibleError) |> E.R.fmap(Wrappers.evNumber)
+      ),
+    ],
   ),
   Function.make(
     ~name="Sort",
     ~definitions=[
       ArrayNumberDist.make("sort", r =>
-        r->E.A.Floats.sort->E.A2.fmap(Wrappers.evNumber)->Wrappers.evArray
+        r->E.A.Floats.sort->E.A2.fmap(Wrappers.evNumber)->Wrappers.evArray->Ok
       ),
     ],
   ),
@@ -189,7 +211,23 @@ let registry = [
     ~name="Reverse",
     ~definitions=[
       ArrayNumberDist.make("reverse", r =>
-        r->Belt_Array.reverse->E.A2.fmap(Wrappers.evNumber)->Wrappers.evArray
+        r->Belt_Array.reverse->E.A2.fmap(Wrappers.evNumber)->Wrappers.evArray->Ok
+      ),
+    ],
+  ),
+  Function.make(
+    ~name="Cumulative Sum",
+    ~definitions=[
+      ArrayNumberDist.make("cumsum", r =>
+        r->E.A.Floats.cumsum->E.A2.fmap(Wrappers.evNumber)->Wrappers.evArray->Ok
+      ),
+    ],
+  ),
+  Function.make(
+    ~name="Diff",
+    ~definitions=[
+      ArrayNumberDist.make("diff", r =>
+        r->E.A.Floats.diff->E.A2.fmap(Wrappers.evNumber)->Wrappers.evArray->Ok
       ),
     ],
   ),
@@ -296,7 +334,8 @@ let registry = [
           ->E.A.R.firstErrorOrOpen
           ->E.R2.fmap(Js.Dict.fromArray)
           ->E.R2.fmap(Wrappers.evRecord)
-        inputs->E.A.unsafe_get(0)->Prepare.ToValueArray.Array.arrayOfArrays |> E.R2.bind(convertInternalItems)
+        inputs->E.A.unsafe_get(0)->Prepare.ToValueArray.Array.arrayOfArrays
+          |> E.R2.bind(convertInternalItems)
       }),
     ],
   ),

packages/squiggle-lang/src/rescript/Utility/E.res

@@ -751,6 +751,9 @@ module A = {
     let diff = (t: t): array<float> =>
       Belt.Array.zipBy(t, Belt.Array.sliceToEnd(t, 1), (left, right) => right -. left)
 
+    let cumsum = (t: t): array<float> => accumulate((a, b) => a +. b, t)
+    let cumProd = (t: t): array<float> => accumulate((a, b) => a *. b, t)
+
     exception RangeError(string)
     let range = (min: float, max: float, n: int): array<float> =>
       switch n {