Implement generic sparklines with tests

packages/squiggle-lang/__tests__/GenericDist/GenericDistSparkline_Test.res

@@ -0,0 +1,35 @@
+open Jest
+open Expect
+
+let env: DistributionOperation.env = {
+  sampleCount: 100,
+  xyPointLength: 100,
+}
+
+let normalDist: GenericDist_Types.genericDist = Symbolic(#Normal({mean: 5.0, stdev: 2.0}))
+let uniformDist: GenericDist_Types.genericDist = Symbolic(#Uniform({low: 9.0, high: 10.0}))
+let betaDist: GenericDist_Types.genericDist = Symbolic(#Beta({alpha: 2.0, beta: 5.0}))
+let lognormalDist: GenericDist_Types.genericDist = Symbolic(#Lognormal({mu: 0.0, sigma: 1.0}))
+let cauchyDist: GenericDist_Types.genericDist = Symbolic(#Cauchy({local: 1.0, scale: 1.0}))
+let triangularDist: GenericDist_Types.genericDist = Symbolic(#Triangular({low: 1.0, medium: 2.0, high: 3.0}))
+let exponentialDist: GenericDist_Types.genericDist = Symbolic(#Exponential({rate: 2.0}))
+
+let runTest = (name: string, dist : GenericDist_Types.genericDist, expected: string) => {
+  test(name, () => {
+    let result = GenericDist.toSparkline(~xyPointLength=100, ~sampleCount=100, ~buckets=20, dist)
+    switch result {
+    | Ok(sparkline) => expect(sparkline)->toEqual(expected)
+    | Error(err) => expect("Error")->toEqual(expected)
+  }
+  })
+}
+
+describe("sparkline of generic distribution", () => {
+  runTest("normal", normalDist, `▁▁▁▁▂▃▄▆▇██▇▆▄▃▂▁▁▁`)
+  runTest("uniform", uniformDist, `████████████████████`)
+  runTest("beta", uniformDist, `████████████████████`)
+  runTest("lognormal", lognormalDist, `█▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁`)
+  runTest("cauchy", cauchyDist, `▁▁▁▁▁▁▁▁▁██▁▁▁▁▁▁▁▁▁`)
+  runTest("triangular", triangularDist, `▁▂▃▄▄▅▆▇████▇▆▅▄▄▃▂▁`)
+  runTest("exponential", exponentialDist, `█▆▄▃▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁`)
+})

packages/squiggle-lang/src/rescript/Distributions/GenericDist/GenericDist.res

@@ -49,7 +49,7 @@ let toFloatOperation = (
   }
 }
 
-//Todo: If it's a pointSet, but the xyPointLenght is different from what it has, it should change.
+//Todo: If it's a pointSet, but the xyPointLength is different from what it has, it should change.
 // This is tricky because the case of discrete distributions.
 // Also, change the outputXYPoints/pointSetDistLength details
 let toPointSet = (~xyPointLength, ~sampleCount, t): result<PointSetTypes.pointSetDist, error> => {
@@ -75,6 +75,9 @@ let toPointSet = (~xyPointLength, ~sampleCount, t): result<PointSetTypes.pointSe
   }
 }
 
+let toSparkline = (~xyPointLength: int, ~sampleCount: int, ~buckets: int = 20, t: t) : result<string, error> => 
+  toPointSet(~xyPointLength, ~sampleCount, t) -> E.R2.fmap(PointSetDist.toSparkline(buckets))
+
 module Truncate = {
   let trySymbolicSimplification = (leftCutoff, rightCutoff, t: t): option<t> =>
     switch (leftCutoff, rightCutoff, t) {

packages/squiggle-lang/src/rescript/Distributions/GenericDist/GenericDist.resi

@@ -24,6 +24,12 @@ let toPointSet: (
   ~sampleCount: int,
   t,
 ) => result<PointSetTypes.pointSetDist, error>
+let toSparkline: (
+  ~xyPointLength: int,
+  ~sampleCount: int,
+  ~buckets: int=?,
+  t,
+) => result<string, error>
 
 let truncate: (
   t,

packages/squiggle-lang/src/rescript/Distributions/PointSetDist/PointSetDist.res

@@ -168,6 +168,22 @@ let pdf = (f: float, t: t) => {
 let inv = T.Integral.yToX
 let cdf = T.Integral.xToY
 
+let diff = (arr: array<float>): array<float> =>
+  Belt.Array.zipBy(arr, Belt.Array.sliceToEnd(arr, 1), (left, right) => right -. left)
+
+let rec rangeByFloat = (start : float, end: float, step: float) => 
+  start > end ?
+    []
+    : Belt.Array.concat([start], rangeByFloat(start +. step, end, step))
+
+@genType
+let toSparkline = (buckets: int, t: t ): string => {
+  let size : float = T.maxX(t) -. T.minX(t)
+  let stepSize = size /. Belt.Int.toFloat(buckets)
+  let cdf = rangeByFloat(T.minX(t), T.maxX(t), stepSize) -> Belt.Array.map(val => cdf(val,t))
+  Sparklines.create(diff(cdf), ())
+}
+
 let doN = (n, fn) => {
   let items = Belt.Array.make(n, 0.0)
   for x in 0 to n - 1 {