Fix subtraction not commuting under pointsets

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

@@ -191,12 +191,14 @@ let combineShapesContinuousDiscrete = (
   op: Operation.convolutionOperation,
   continuousShape: PointSetTypes.xyShape,
   discreteShape: PointSetTypes.xyShape,
+  flip: bool,
 ): PointSetTypes.xyShape => {
   let t1n = continuousShape |> XYShape.T.length
   let t2n = discreteShape |> XYShape.T.length
 
   // each x pair is added/subtracted
-  let fn = Operation.Convolution.toFn(op)
+  let opFunc = Operation.Convolution.toFn(op)
+  let fn = flip ? (a, b) => opFunc(b, a) : opFunc
 
   let outXYShapes: array<array<(float, float)>> = Belt.Array.makeUninitializedUnsafe(t2n)
 

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

@@ -278,6 +278,7 @@ let combineAlgebraicallyWithDiscrete = (
   op: Operation.convolutionOperation,
   t1: t,
   t2: PointSetTypes.discreteShape,
+  flip: bool,
 ) => {
   let t1s = t1 |> getShape
   let t2s = t2.xyShape // TODO would like to use Discrete.getShape here, but current file structure doesn't allow for that
@@ -294,6 +295,7 @@ let combineAlgebraicallyWithDiscrete = (
       op,
       continuousAsLinear |> getShape,
       t2s,
+      flip,
     )
 
     let combinedIntegralSum = switch op {

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

@@ -277,8 +277,18 @@ let combineAlgebraically = (op: Operation.convolutionOperation, t1: t, t2: t): t
   // continuous (*) continuous => continuous, but also
   // discrete (*) continuous => continuous (and vice versa). We have to take care of all combos and then combine them:
   let ccConvResult = Continuous.combineAlgebraically(op, t1.continuous, t2.continuous)
-  let dcConvResult = Continuous.combineAlgebraicallyWithDiscrete(op, t2.continuous, t1.discrete)
-  let cdConvResult = Continuous.combineAlgebraicallyWithDiscrete(op, t1.continuous, t2.discrete)
+  let dcConvResult = Continuous.combineAlgebraicallyWithDiscrete(
+    op,
+    t2.continuous,
+    t1.discrete,
+    true,
+  )
+  let cdConvResult = Continuous.combineAlgebraicallyWithDiscrete(
+    op,
+    t1.continuous,
+    t2.discrete,
+    false,
+  )
   let continuousConvResult = Continuous.sum([ccConvResult, dcConvResult, cdConvResult])
 
   // ... finally, discrete (*) discrete => discrete, obviously:

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

@@ -46,9 +46,10 @@ let combineAlgebraically = (op: Operation.convolutionOperation, t1: t, t2: t): t
   switch (t1, t2) {
   | (Continuous(m1), Continuous(m2)) =>
     Continuous.combineAlgebraically(op, m1, m2) |> Continuous.T.toPointSetDist
-  | (Continuous(m1), Discrete(m2))
-  | (Discrete(m2), Continuous(m1)) =>
-    Continuous.combineAlgebraicallyWithDiscrete(op, m1, m2) |> Continuous.T.toPointSetDist
+  | (Discrete(m1), Continuous(m2)) =>
+    Continuous.combineAlgebraicallyWithDiscrete(op, m2, m1, true) |> Continuous.T.toPointSetDist
+  | (Continuous(m1), Discrete(m2)) =>
+    Continuous.combineAlgebraicallyWithDiscrete(op, m1, m2, false) |> Continuous.T.toPointSetDist
   | (Discrete(m1), Discrete(m2)) =>
     Discrete.combineAlgebraically(op, m1, m2) |> Discrete.T.toPointSetDist
   | (m1, m2) => Mixed.combineAlgebraically(op, toMixed(m1), toMixed(m2)) |> Mixed.T.toPointSetDist