Continuation in attempting to refactor SymbolicDist

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

@@ -3,19 +3,67 @@ open SymbolicDistTypes
 let normal95confidencePoint = 1.6448536269514722
 // explained in website/docs/internal/ProcessingConfidenceIntervals
 
+type normalError = NormalStandardDeviationGreaterThanZero(float)
+
+@genType
+type rec error =
+  | NotFinite(string, string, float)
+  | DivideByZero(string)
+  | NormalError(normalError)
+  | SafeMath(SafeMath.error)
+  | MultipleErrors(array<error>)
+  | NinetiethPercentileShouldBeOrdered
+
+module Error = {
+  let mapErrorArrayToError = (errors: array<error>): option<error> => {
+    switch errors {
+    | [] => None
+    | [error] => Some(error)
+    | _ => Some(MultipleErrors(errors))
+    }
+  }
+
+  let checkIsFinite = (value, fnName, propertyName) =>
+    E.Float.isFinite(value) ? None : Some(NotFinite(fnName, propertyName, value))
+
+  let divideByZero = (value, fnName) => 0.0 == value ? None : Some(DivideByZero(fnName))
+}
+
+let ifNoErrorsThanDo = (errors, fn) =>
+  errors->E.A.O.concatSomes->Error.mapErrorArrayToError->E.O.errorToResult(fn)
+
 module Normal = {
   type t = normal
-  let make = (mean: float, stdev: float): result<symbolicDist, string> =>
-    stdev > 0.0
-      ? Ok(#Normal({mean: mean, stdev: stdev}))
-      : Error("Standard deviation of normal distribution must be larger than 0")
+  let dangerouslyMake = (~mean: float, ~stdev: float) => #Normal({mean: mean, stdev: stdev})
+  let inputValidation = (~mean, ~stdev) =>
+    [
+      Error.checkIsFinite(mean, "Normal", "mean"),
+      Error.checkIsFinite(stdev, "Normal", "stdev"),
+      stdev <= 0.0 ? Some(NormalError(NormalStandardDeviationGreaterThanZero(stdev))) : None,
+    ]
+    ->E.A.O.concatSomes
+    ->Error.mapErrorArrayToError
+
+  let make = (~mean: float, ~stdev: float): result<symbolicDist, error> =>
+    inputValidation(~mean, ~stdev)->E.O.errorToResult(() => Ok(dangerouslyMake(~mean, ~stdev)))
+
   let pdf = (x, t: t) => Jstat.Normal.pdf(x, t.mean, t.stdev)
   let cdf = (x, t: t) => Jstat.Normal.cdf(x, t.mean, t.stdev)
 
   let from90PercentCI = (low, high) => {
+    let construct = () => {
       let mean = E.A.Floats.mean([low, high])
-    let stdev = (high -. low) /. (2. *. normal95confidencePoint)
-    #Normal({mean: mean, stdev: stdev})
+      let stdev =
+        SafeMath.F.divide(
+          ~num=high -. low,
+          ~denominator=2. *. normal95confidencePoint,
+        )->E.R2.errMap(r => SafeMath(r))
+      stdev->E.R.bind(stdev => make(~mean, ~stdev))
+    }
+    [
+      Error.checkIsFinite(low, "Normal", "low"),
+      Error.checkIsFinite(high, "Normal", "high"),
+    ]->ifNoErrorsThanDo(construct)
   }
   let inv = (p, t: t) => Jstat.Normal.inv(p, t.mean, t.stdev)
   let sample = (t: t) => Jstat.Normal.sample(t.mean, t.stdev)
@@ -25,20 +73,20 @@ module Normal = {
   let add = (n1: t, n2: t) => {
     let mean = n1.mean +. n2.mean
     let stdev = Js.Math.sqrt(n1.stdev ** 2. +. n2.stdev ** 2.)
-    #Normal({mean: mean, stdev: stdev})
+    dangerouslyMake(~mean, ~stdev)
   }
   let subtract = (n1: t, n2: t) => {
     let mean = n1.mean -. n2.mean
     let stdev = Js.Math.sqrt(n1.stdev ** 2. +. n2.stdev ** 2.)
-    #Normal({mean: mean, stdev: stdev})
+    dangerouslyMake(~mean, ~stdev)
   }
 
-  // TODO: is this useful here at all? would need the integral as well ...
+  // Note: This isn't being used right now
   let pointwiseProduct = (n1: t, n2: t) => {
     let mean =
       (n1.mean *. n2.stdev ** 2. +. n2.mean *. n1.stdev ** 2.) /. (n1.stdev ** 2. +. n2.stdev ** 2.)
     let stdev = 1. /. (1. /. n1.stdev ** 2. +. 1. /. n2.stdev ** 2.)
-    #Normal({mean: mean, stdev: stdev})
+    make(~mean, ~stdev)
   }
 
   let operate = (operation: Operation.Algebraic.t, n1: t, n2: t) =>
@@ -50,18 +98,27 @@ module Normal = {
 
   let operateFloatFirst = (operation: Operation.Algebraic.t, n1: float, n2: t) =>
     switch operation {
-    | #Add => Some(#Normal({mean: n1 +. n2.mean, stdev: n2.stdev}))
-    | #Subtract => Some(#Normal({mean: n1 -. n2.mean, stdev: n2.stdev}))
-    | #Multiply => Some(#Normal({mean: n1 *. n2.mean, stdev: Js.Math.abs_float(n1) *. n2.stdev}))
+    | #Add => Some(make(~mean=n1 +. n2.mean, ~stdev=n2.stdev))
+    | #Subtract => Some(make(~mean=n1 -. n2.mean, ~stdev=n2.stdev))
+    | #Multiply => Some(make(~mean=n1 *. n2.mean, ~stdev=Js.Math.abs_float(n1) *. n2.stdev))
     | _ => None
     }
 
   let operateFloatSecond = (operation: Operation.Algebraic.t, n1: t, n2: float) =>
     switch operation {
-    | #Add => Some(#Normal({mean: n1.mean +. n2, stdev: n1.stdev}))
-    | #Subtract => Some(#Normal({mean: n1.mean -. n2, stdev: n1.stdev}))
-    | #Multiply => Some(#Normal({mean: n1.mean *. n2, stdev: n1.stdev *. Js.Math.abs_float(n2)}))
-    | #Divide => Some(#Normal({mean: n1.mean /. n2, stdev: n1.stdev /. Js.Math.abs_float(n2)}))
+    | #Add => Some(make(~mean=n1.mean +. n2, ~stdev=n1.stdev))
+    | #Subtract => Some(make(~mean=n1.mean -. n2, ~stdev=n1.stdev))
+    | #Multiply => Some(make(~mean=n1.mean *. n2, ~stdev=n1.stdev *. Js.Math.abs_float(n2)))
+    | #Divide =>
+      {
+        let mean = SafeMath.F.divide(~num=n1.mean, ~denominator=n2)->E.R2.errMap(r => SafeMath(r))
+        let stdev =
+          SafeMath.F.divide(
+            ~num=n1.stdev,
+            ~denominator=Js.Math.abs_float(n2),
+          )->E.R2.errMap(r => SafeMath(r))
+        E.R.merge(mean, stdev)->E.R.bind(((mean, stdev)) => make(~mean, ~stdev))
+      }->Some
     | _ => None
     }
 }
@@ -230,9 +287,9 @@ module Float = {
 module From90thPercentile = {
   let make = (low, high) =>
     switch (low, high) {
-    | (low, high) if low <= 0.0 && low < high => Ok(Normal.from90PercentCI(low, high))
+    | (low, high) if low <= 0.0 && low < high => Normal.from90PercentCI(low, high)
     | (low, high) if low < high => Ok(Lognormal.from90PercentCI(low, high))
-    | (_, _) => Error("Low value must be less than high value.")
+    | (_, _) => Error(NinetiethPercentileShouldBeOrdered)
     }
 }
 

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

@@ -136,6 +136,13 @@ module O = {
     | None => Error(error)
     }
 
+  let errorToResult = (error: option<'a>, fn) => {
+    switch error {
+    | None => fn()
+    | Some(e) => Error(e)
+    }
+  }
+
   let compare = (compare, f1: option<float>, f2: option<float>) =>
     switch (f1, f2) {
     | (Some(f1), Some(f2)) => Some(compare(f1, f2) ? f1 : f2)
@@ -198,6 +205,13 @@ module Float = {
   let with3DigitsPrecision = Js.Float.toPrecisionWithPrecision(_, ~digits=3)
   let toFixed = Js.Float.toFixed
   let toString = Js.Float.toString
+  let isFinite = Js.Float.isFinite
+  let safeDivision = (num: float, denom: float) =>
+    if denom == 0.0 {
+      Error("Division by zero")
+    } else {
+      Ok(num /. denom)
+    }
 }
 
 module I = {

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

@@ -0,0 +1,38 @@
+@genType
+type rec error =
+  | DivideByZero
+  | IsNaN
+  | IsInfinite
+  | NotFinite(string, float)
+
+module Error = {
+  let checkIsFinite = (value, fnName) =>
+    E.Float.isFinite(value) ? None : Some(NotFinite(fnName, value))
+
+  let divideByZero = value => 0.0 == value ? None : Some(DivideByZero)
+}
+
+module Float = {
+  type t = float
+  let make = (v: t) =>
+    switch Error.checkIsFinite(v, "toSafe") {
+    | None => Ok(v)
+    | Some(e) => Error(e)
+    }
+}
+
+module F = {
+  type t = float
+  let divide = (~num: t, ~denominator: t) => {
+    if denominator == 0.0 {
+      Error(DivideByZero)
+    } else {
+      let result = num /. denominator
+      if E.Float.isFinite(result) {
+        Ok(result)
+      } else {
+        Error(NotFinite("divide", result))
+      }
+    }
+  }
+}