diff --git a/src/distPlus/expressionTree/ExpressionTreeEvaluator.re b/src/distPlus/expressionTree/ExpressionTreeEvaluator.re
index 1047fb8d..c1220506 100644
--- a/src/distPlus/expressionTree/ExpressionTreeEvaluator.re
+++ b/src/distPlus/expressionTree/ExpressionTreeEvaluator.re
@@ -20,68 +20,18 @@ module AlgebraicCombination = {
     | _ => Ok(`AlgebraicCombination((operation, t1, t2)))
     };
 
-  let combinationBySampling = (n, algebraicOp, t1: node, t2: node) => {
-    let sampleN =
-      mapRenderable(Shape.sampleNRendered(n), SymbolicDist.T.sampleN(n));
-    switch (sampleN(t1), sampleN(t2)) {
-    | (Some(a), Some(b)) =>
-      Some(
-        Belt.Array.zip(a, b)
-        |> E.A.fmap(((a, b)) => Operation.Algebraic.toFn(algebraicOp, a, b)),
-      )
-    | _ => None
-    };
-  };
-
   let combinationByRendering =
       (evaluationParams, algebraicOp, t1: node, t2: node)
       : result(node, string) => {
     E.R.merge(
-      renderAndGetShape(evaluationParams, t1),
-      renderAndGetShape(evaluationParams, t2),
+      Render.ensureIsRenderedAndGetShape(evaluationParams, t1),
+      Render.ensureIsRenderedAndGetShape(evaluationParams, t2),
     )
     |> E.R.fmap(((a, b)) =>
          `RenderedDist(Shape.combineAlgebraically(algebraicOp, a, b))
        );
   };
 
-  let combineShapesUsingSampling =
-      (evaluationParams: evaluationParams, algebraicOp, t1: node, t2: node) => {
-    let i1 = renderIfNotRenderable(evaluationParams, t1);
-    let i2 = renderIfNotRenderable(evaluationParams, t2);
-    E.R.merge(i1, i2)
-    |> E.R.bind(
-         _,
-         ((a, b)) => {
-           let samples =
-             combinationBySampling(
-               evaluationParams.samplingInputs.sampleCount,
-               algebraicOp,
-               a,
-               b,
-             );
-           let shape =
-             samples
-             |> E.O.fmap(
-                  Samples.T.fromSamples(
-                    ~samplingInputs={
-                      sampleCount:
-                        Some(evaluationParams.samplingInputs.sampleCount),
-                      outputXYPoints:
-                        Some(evaluationParams.samplingInputs.outputXYPoints),
-                      kernelWidth: evaluationParams.samplingInputs.kernelWidth,
-                    },
-                  ),
-                )
-             |> E.O.bind(_, (r: RenderTypes.ShapeRenderer.Sampling.outputs) =>
-                  r.shape
-                )
-             |> E.O.toResult("No response");
-           shape |> E.R.fmap(r => `Normalize(`RenderedDist(r)));
-         },
-       );
-  };
-
   let operationToLeaf =
       (
         evaluationParams: evaluationParams,
@@ -107,7 +57,7 @@ module VerticalScaling = {
     let fn = Operation.Scale.toFn(scaleOp);
     let integralSumCacheFn = Operation.Scale.toIntegralSumCacheFn(scaleOp);
     let integralCacheFn = Operation.Scale.toIntegralCacheFn(scaleOp);
-    let renderedShape = render(evaluationParams, t);
+    let renderedShape = Render.render(evaluationParams, t);
 
     switch (renderedShape, scaleBy) {
     | (Ok(`RenderedDist(rs)), `SymbolicDist(`Float(sm))) =>
@@ -129,7 +79,7 @@ module VerticalScaling = {
 
 module PointwiseCombination = {
   let pointwiseAdd = (evaluationParams: evaluationParams, t1: t, t2: t) => {
-    switch (render(evaluationParams, t1), render(evaluationParams, t2)) {
+    switch (Render.render(evaluationParams, t1), Render.render(evaluationParams, t2)) {
     | (Ok(`RenderedDist(rs1)), Ok(`RenderedDist(rs2))) =>
       Ok(
         `RenderedDist(
@@ -184,7 +134,7 @@ module Truncate = {
     switch (leftCutoff, rightCutoff, t) {
     | (None, None, t) => `Solution(t)
     | (Some(lc), Some(rc), t) when lc > rc =>
-      `Error("Left truncation bound must be smaller than right bound.")
+      `Error("Left truncation bound must be smaller than right truncation bound.")
     | (lc, rc, `SymbolicDist(`Uniform(u))) =>
       `Solution(
         `SymbolicDist(`Uniform(SymbolicDist.Uniform.truncate(lc, rc, u))),
@@ -197,7 +147,7 @@ module Truncate = {
       (evaluationParams: evaluationParams, leftCutoff, rightCutoff, t) => {
     // TODO: use named args for xMin/xMax in renderToShape; if we're lucky we can at least get the tail
     // of a distribution we otherwise wouldn't get at all
-    switch (render(evaluationParams, t)) {
+    switch (Render.ensureIsRendered(evaluationParams, t)) {
     | Ok(`RenderedDist(rs)) =>
       Ok(`RenderedDist(Shape.T.truncate(leftCutoff, rightCutoff, rs)))
     | Error(e) => Error(e)
diff --git a/src/distPlus/expressionTree/ExpressionTypes.re b/src/distPlus/expressionTree/ExpressionTypes.re
index 2cee4630..a76aee74 100644
--- a/src/distPlus/expressionTree/ExpressionTypes.re
+++ b/src/distPlus/expressionTree/ExpressionTypes.re
@@ -37,61 +37,42 @@ module ExpressionTree = {
   let evaluateNode = (evaluationParams: evaluationParams) =>
     evaluationParams.evaluateNode(evaluationParams);
 
-  let render = (evaluationParams: evaluationParams, r) =>
-    evaluateNode(evaluationParams, `Render(r));
-
-  let renderable =
-    fun
-    | `SymbolicDist(_) => true
-    | `RenderedDist(_) => true
-    | _ => false;
-
-  let renderIfNotRenderable = (params, t) =>
-    !renderable(t)
-      ? switch (render(params, t)) {
-        | Ok(r) => Ok(r)
-        | Error(e) => Error(e)
-        }
-      : Ok(t);
-
-  let renderIfNotRendered = (params, t) =>
-    switch (t) {
-    | `RenderedDist(_) => Ok(t)
-    | _ =>
-      switch (render(params, t)) {
-      | Ok(r) => Ok(r)
-      | Error(e) => Error(e)
-      }
-    };
-
   let evaluateAndRetry = (evaluationParams, fn, node) =>
     node
     |> evaluationParams.evaluateNode(evaluationParams)
     |> E.R.bind(_, fn(evaluationParams));
 
-  let renderedShape = (item: node) =>
-    switch (item) {
-    | `RenderedDist(r) => Some(r)
-    | _ => None
-    };
+  module Render = {
+    type t = node;
 
-  let renderAndGetShape = (params, t) =>
-    switch (renderIfNotRendered(params, t)) {
-    | Ok(`RenderedDist(r)) => Ok(r)
-    | Error(r) =>
-      Js.log(r);
-      Error(r);
-    | Ok(l) =>
-      Js.log(l);
-      Error("Did not render as requested");
-    };
+    let render = (evaluationParams: evaluationParams, r) =>
+      `Render(r) |> evaluateNode(evaluationParams);
+
+    let ensureIsRendered = (params, t) =>
+      switch (t) {
+      | `RenderedDist(_) => Ok(t)
+      | _ =>
+        switch (render(params, t)) {
+        | Ok(`RenderedDist(r)) => Ok(`RenderedDist(r))
+        | Ok(_) => Error("Did not render as requested")
+        | Error(e) => Error(e)
+        }
+      };
+
+    let ensureIsRenderedAndGetShape = (params, t) =>
+      switch (ensureIsRendered(params, t)) {
+      | Ok(`RenderedDist(r)) => Ok(r)
+      | Ok(_) => Error("Did not render as requested")
+      | Error(e) => Error(e)
+      };
+
+    let getShape = (item: node) =>
+      switch (item) {
+      | `RenderedDist(r) => Some(r)
+      | _ => None
+      };
+  };
 
-  let mapRenderable = (renderedFn, symFn, item: node) =>
-    switch (item) {
-    | `SymbolicDist(s) => Some(symFn(s))
-    | `RenderedDist(r) => Some(renderedFn(r))
-    | _ => None
-    };
 };
 
 type simplificationResult = [
diff --git a/src/distPlus/expressionTree/SamplingDistribution.re b/src/distPlus/expressionTree/SamplingDistribution.re
new file mode 100644
index 00000000..60886b40
--- /dev/null
+++ b/src/distPlus/expressionTree/SamplingDistribution.re
@@ -0,0 +1,80 @@
+open ExpressionTypes.ExpressionTree;
+
+let isSamplingDistribution: node => bool =
+  fun
+  | `SymbolicDist(_) => true
+  | `RenderedDist(_) => true
+  | _ => false;
+
+let renderIfIsNotSamplingDistribution = (params, t) =>
+  !isSamplingDistribution(t)
+    ? switch (Render.render(params, t)) {
+      | Ok(r) => Ok(r)
+      | Error(e) => Error(e)
+      }
+    : Ok(t);
+
+let map = (~renderedDistFn, ~symbolicDistFn, node: node) =>
+  node
+  |> (
+    fun
+    | `RenderedDist(r) => Some(renderedDistFn(r))
+    | `SymbolicDist(s) => Some(symbolicDistFn(s))
+    | _ => None
+  );
+
+let sampleN = n =>
+  map(
+    ~renderedDistFn=Shape.sampleNRendered(n),
+    ~symbolicDistFn=SymbolicDist.T.sampleN(n),
+  );
+
+let getCombinationSamples = (n, algebraicOp, t1: node, t2: node) => {
+  switch (sampleN(n, t1), sampleN(n, t2)) {
+  | (Some(a), Some(b)) =>
+    Some(
+      Belt.Array.zip(a, b)
+      |> E.A.fmap(((a, b)) => Operation.Algebraic.toFn(algebraicOp, a, b)),
+    )
+  | _ => None
+  };
+};
+
+let combineShapesUsingSampling =
+    (evaluationParams: evaluationParams, algebraicOp, t1: node, t2: node) => {
+  let i1 = renderIfIsNotSamplingDistribution(evaluationParams, t1);
+  let i2 = renderIfIsNotSamplingDistribution(evaluationParams, t2);
+  E.R.merge(i1, i2)
+  |> E.R.bind(
+       _,
+       ((a, b)) => {
+         let samples =
+           getCombinationSamples(
+             evaluationParams.samplingInputs.sampleCount,
+             algebraicOp,
+             a,
+             b,
+           );
+
+         //  todo: This bottom part should probably be somewhere else.
+         let shape =
+           samples
+           |> E.O.fmap(
+                Samples.T.fromSamples(
+                  ~samplingInputs={
+                    sampleCount:
+                      Some(evaluationParams.samplingInputs.sampleCount),
+                    outputXYPoints:
+                      Some(evaluationParams.samplingInputs.outputXYPoints),
+                    kernelWidth: evaluationParams.samplingInputs.kernelWidth,
+                  },
+                ),
+              )
+           |> E.O.bind(_, (r: RenderTypes.ShapeRenderer.Sampling.outputs) =>
+                r.shape
+              )
+           |> E.O.toResult("No response");
+         shape |> E.R.fmap(r => `Normalize(`RenderedDist(r)));
+       },
+     );
+};