diff --git a/packages/components/.prettierignore b/packages/components/.prettierignore
new file mode 100644
index 00000000..5e03c80e
--- /dev/null
+++ b/packages/components/.prettierignore
@@ -0,0 +1,2 @@
+dist/
+storybook-static
diff --git a/packages/components/src/components/SquiggleChart.tsx b/packages/components/src/components/SquiggleChart.tsx
index 9553d329..534d164d 100644
--- a/packages/components/src/components/SquiggleChart.tsx
+++ b/packages/components/src/components/SquiggleChart.tsx
@@ -131,7 +131,7 @@ export interface SquiggleChartProps {
   /** variables declared before this expression */
   environment?: unknown;
   /** When the environment changes */
-  onEnvChange?(env: unknown): void;
+  onChange?(expr: squiggleExpression): void;
   /** CSS width of the element */
   width?: number;
   height?: number;
@@ -141,8 +141,7 @@ export const SquiggleChart: React.FC<SquiggleChartProps> = ({
   squiggleString = "",
   sampleCount = 1000,
   outputXYPoints = 1000,
-  environment = [],
-  onEnvChange = () => {},
+  onChange = () => {},
   height = 60,
   width = NaN,
 }: SquiggleChartProps) => {
@@ -158,8 +157,8 @@ export const SquiggleChart: React.FC<SquiggleChartProps> = ({
   let expressionResult = run(squiggleString, samplingInputs);
   let internal: JSX.Element;
   if (expressionResult.tag === "Ok") {
-    onEnvChange(environment);
     let expression = expressionResult.value;
+    onChange(expression);
     internal = (
       <SquiggleItem expression={expression} width={_width} height={height} />
     );
diff --git a/packages/components/src/components/SquiggleEditor.tsx b/packages/components/src/components/SquiggleEditor.tsx
index 4ede7891..580db580 100644
--- a/packages/components/src/components/SquiggleEditor.tsx
+++ b/packages/components/src/components/SquiggleEditor.tsx
@@ -3,6 +3,7 @@ import * as ReactDOM from "react-dom";
 import { SquiggleChart } from "./SquiggleChart";
 import { CodeEditor } from "./CodeEditor";
 import styled from "styled-components";
+import type { squiggleExpression } from "@quri/squiggle-lang";
 
 export interface SquiggleEditorProps {
   /** The input string for squiggle */
@@ -22,7 +23,7 @@ export interface SquiggleEditorProps {
   /** The environment, other variables that were already declared */
   environment?: unknown;
   /** when the environment changes. Used again for notebook magic*/
-  onEnvChange?(env: unknown): void;
+  onChange?(expr: squiggleExpression): void;
   /** The width of the element */
   width: number;
 }
@@ -43,7 +44,7 @@ export let SquiggleEditor: React.FC<SquiggleEditorProps> = ({
   diagramStart,
   diagramStop,
   diagramCount,
-  onEnvChange,
+  onChange,
   environment,
 }: SquiggleEditorProps) => {
   let [expression, setExpression] = React.useState(initialSquiggleString);
@@ -69,7 +70,7 @@ export let SquiggleEditor: React.FC<SquiggleEditorProps> = ({
         diagramStop={diagramStop}
         diagramCount={diagramCount}
         environment={environment}
-        onEnvChange={onEnvChange}
+        onChange={onChange}
       />
     </div>
   );
@@ -80,7 +81,7 @@ export function renderSquiggleEditorToDom(props: SquiggleEditorProps) {
   ReactDOM.render(
     <SquiggleEditor
       {...props}
-      onEnvChange={(env) => {
+      onChange={(expr) => {
         // Typescript complains on two levels here.
         //  - Div elements don't have a value property
         //  - Even if it did (like it was an input element), it would have to
@@ -96,10 +97,10 @@ export function renderSquiggleEditorToDom(props: SquiggleEditorProps) {
         //  viewof env = cell('normal(0,1)')
         //  to work
         // @ts-ignore
-        parent.value = env;
+        parent.value = expr;
 
         parent.dispatchEvent(new CustomEvent("input"));
-        if (props.onEnvChange) props.onEnvChange(env);
+        if (props.onChange) props.onChange(expr);
       }}
     />,
     parent
diff --git a/packages/squiggle-lang/__tests__/ReducerInterface/ReducerInterface_Distribution_test.res b/packages/squiggle-lang/__tests__/ReducerInterface/ReducerInterface_Distribution_test.res
index d4199f89..605797b9 100644
--- a/packages/squiggle-lang/__tests__/ReducerInterface/ReducerInterface_Distribution_test.res
+++ b/packages/squiggle-lang/__tests__/ReducerInterface/ReducerInterface_Distribution_test.res
@@ -20,6 +20,7 @@ describe("eval on distribution functions", () => {
   })
   describe("unaryMinus", () => {
     testEval("mean(-normal(5,2))", "Ok(-5)")
+    testEval("-normal(5,2)", "Ok(Normal(-5,2))")
   })
   describe("to", () => {
     testEval("5 to 2", "Error(Math Error: Low value must be less than high value.)")
diff --git a/packages/squiggle-lang/src/rescript/Distributions/PointSetDist/AlgebraicShapeCombination.res b/packages/squiggle-lang/src/rescript/Distributions/PointSetDist/AlgebraicShapeCombination.res
index d68a9623..39d68e6a 100644
--- a/packages/squiggle-lang/src/rescript/Distributions/PointSetDist/AlgebraicShapeCombination.res
+++ b/packages/squiggle-lang/src/rescript/Distributions/PointSetDist/AlgebraicShapeCombination.res
@@ -232,13 +232,12 @@ let combineShapesContinuousDiscrete = (
           i,
           (
             fn(continuousShape.xs[i], discreteShape.xs[j]),
-            continuousShape.ys[i] *. discreteShape.ys[j] /. discreteShape.xs[j],
+            continuousShape.ys[i] *. discreteShape.ys[j] /. Js.Math.abs_float(discreteShape.xs[j]),
           ),
         ) |> ignore
         ()
       }
       Belt.Array.set(outXYShapes, j, dxyShape) |> ignore
-      ()
     }
   }
 
@@ -246,12 +245,11 @@ let combineShapesContinuousDiscrete = (
   |> E.A.fmap(XYShape.T.fromZippedArray)
   |> E.A.fold_left(
     (acc, x) =>
-      XYShape.PointwiseCombination.combine(
-        (a, b) => Ok(a +. b),
+      XYShape.PointwiseCombination.addCombine(
         XYShape.XtoY.continuousInterpolator(#Linear, #UseZero),
         acc,
         x,
-      )->E.R.toExn("Error, unexpected failure", _),
+      ),
     XYShape.T.empty,
   )
 }
diff --git a/packages/squiggle-lang/src/rescript/Distributions/SymbolicDist/SymbolicDist.res b/packages/squiggle-lang/src/rescript/Distributions/SymbolicDist/SymbolicDist.res
index 7ce95721..92249eae 100644
--- a/packages/squiggle-lang/src/rescript/Distributions/SymbolicDist/SymbolicDist.res
+++ b/packages/squiggle-lang/src/rescript/Distributions/SymbolicDist/SymbolicDist.res
@@ -52,7 +52,7 @@ module Normal = {
     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: n1 *. n2.stdev}))
+    | #Multiply => Some(#Normal({mean: n1 *. n2.mean, stdev: Js.Math.abs_float(n1) *. n2.stdev}))
     | _ => None
     }
 
@@ -60,8 +60,8 @@ module Normal = {
     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 *. n2}))
-    | #Divide => Some(#Normal({mean: n1.mean /. n2, stdev: n1.stdev /. n2}))
+    | #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)}))
     | _ => None
     }
 }