most of the refactor based on @OAGr's comments

packages/squiggle-lang/__tests__/Symbolic_test.res

@@ -8,23 +8,27 @@ let makeTest = (~only=false, str, item1, item2) =>
     ? Only.test(str, () => expect(item1) -> toEqual(item2))
     : test(str, () => expect(item1) -> toEqual(item2))
 
-let normalParams1: SymbolicDistTypes.normal = {mean: 5.0, stdev: 2.0}
-// let normalParams2: SymbolicDistTypes.normal = {mean: 10.0, stdev: 2.0}
-let normalParams3: SymbolicDistTypes.normal = {mean: 20.0, stdev: 2.0}
-let range20 = [0.0,1.0,2.0,3.0,4.0,5.0,6.0,7.0,8.0,9.0,10.0,11.0,12.0,13.0,14.0,15.0,16.0,17.0,18.0,19.0,20.0]
-let forSparkline = (thisPdf, inps) => map(thisPdf, inps)
+let pdfImage = (thePdf, inps) => map(thePdf, inps)
 
-describe("Normal with Sparklines", () => {
-  let pdf1 = x => Normal.pdf(x, normalParams1)
-  let forSparkline1 = forSparkline(pdf1, range20)
-  makeTest("mean=5", Sparklines.sparkly(forSparkline1, ~options={minimum: None, maximum: None}), `▁▂▃▅███▅▃▂▁▁▁▁▁▁▁▁▁▁▁`)
-
-  let normal4 = Normal.add(normalParams1, normalParams3)
-  let normalParams4 = switch normal4 {
-      | #Normal(params) => params
-      | _ => {mean: 0.0, stdev: 1.0}
+let parameterWiseAdditionHelper = (n1: SymbolicDistTypes.normal, n2: SymbolicDistTypes.normal) => {
+  let normalDistAtSumMeanConstr = Normal.add(n1, n2)
+  let normalDistAtSumMean: SymbolicDistTypes.normal = switch normalDistAtSumMeanConstr {
+    | #Normal(params) => params
   }
-  let pdf4 = x => Normal.pdf(x, normalParams4)
-  let forSparkline4 = forSparkline(pdf4, range20)
-  makeTest("mixture of two normals", Sparklines.sparkly(forSparkline4, ~options={minimum: None, maximum: None}), `▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▂▅█`)
+  x => Normal.pdf(x, normalDistAtSumMean)
+}
+
+describe("Normal distribution with sparklines", () => {
+
+  let normalDistAtMean5: SymbolicDistTypes.normal = {mean: 5.0, stdev: 2.0}
+  let normalDistAtMean10: SymbolicDistTypes.normal = {mean: 10.0, stdev: 2.0}
+  let range20Float = [0.0,1.0,2.0,3.0,4.0,5.0,6.0,7.0,8.0,9.0,10.0,11.0,12.0,13.0,14.0,15.0,16.0,17.0,18.0,19.0,]
+
+  let pdfNormalDistAtMean5 = x => Normal.pdf(x, normalDistAtMean5)
+  let sparklineMean5 = pdfImage(pdfNormalDistAtMean5, range20Float)
+  makeTest("mean=5", Sparklines.create(sparklineMean5, ()), `▁▂▃▅███▅▃▂▁▁▁▁▁▁▁▁▁▁`)
+
+  let sparklineMean15 = normalDistAtMean5 -> parameterWiseAdditionHelper(normalDistAtMean10) -> pdfImage(range20Float)
+  // let sparklineMean15 = pdfImage(pdfNormalDistAtMean15, range20Float)
+  makeTest("parameter-wise addition of two normal distributions", Sparklines.create(sparklineMean15, ()), `▁▁▁▁▁▁▁▁▁▁▂▃▅▇███▇▅▃`)
 })

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

@@ -323,6 +323,7 @@ module A = {
         }
     )
   let filter = (o, e) => Js.Array.filter(o, e)
+  let joinWith = (fill, arr) => Js.Array.joinWith(fill, arr)
 
   module O = {
     let concatSomes = (optionals: array<option<'a>>): array<'a> =>

packages/squiggle-lang/src/rescript/utility/Sparklines.res

@@ -2,31 +2,28 @@
 // reference implementation: https://github.com/sindresorhus/sparkly
 // Omitting rgb "fire" style, so no `chalk` dependency
 
-type sparklyConfig = {
-  minimum: option<float>,
-  maximum: option<float>
-}
-
-let sparkly = (
+let create = (
   numbers: array<float>,
-  ~options = {minimum: None, maximum: None}
+  ~minimum=?,
+  ~maximum=?,
+  ()
 ) => {
   // Unlike reference impl, we assume that all numbers are finite, i.e. no NaN.
 
   let ticks = [`▁`, `▂`, `▃`, `▄`, `▅`, `▆`, `▇`, `█`]
 
-  let minimum = E.O.default(Js.Math.minMany_float(numbers), options.minimum)
-  let maximum = E.O.default(Js.Math.maxMany_float(numbers), options.maximum)
+  let minimum = E.O.default(Js.Math.minMany_float(numbers), minimum)
+  let maximum = E.O.default(Js.Math.maxMany_float(numbers), maximum)
 
-  // Use a high tick if data is constant and max is not equal
-  let ticks = if minimum == maximum && maximum != 0.0 {
-    [ticks[4]]
-  } else {
-    ticks
-  }
+//  // Use a high tick if data is constant and max is not equal to min or zero
+//  let ticks = if minimum == maximum && maximum != 0.0 {
+//    [ticks[4]]
+//  } else {
+//    ticks
+//  }
 
-  let toMapWith = (number: float) => {
-    let tickIndex = Js.Math.ceil_int((number /. maximum) *. Belt.Int.toFloat(Belt.Array.length(ticks))) - 1
+  let toHeight = (number: float) => {
+    let tickIndex = Js.Math.ceil_int((number /. maximum) *. (ticks -> Belt.Array.length -> Belt.Int.toFloat)) - 1
 
     let tickIndex = if maximum == 0.0 || tickIndex < 0 {
         0
@@ -36,5 +33,5 @@ let sparkly = (
 
     ticks[tickIndex]
   }
-  Js.Array.joinWith("", Belt.Array.map(numbers, toMapWith))
+  toHeight -> E.A.fmap(numbers) -> (arr => E.A.joinWith("", arr))
 }