142 changed files with 2426 additions and 4156 deletions
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@ -1,4 +1,4 @@
-name: Squiggle packages checks
+name: Squiggle packages check

 on:
  push:
@ -9,40 +9,215 @@ on:
    branches:
      - master
      - develop
-
-env:
-  TURBO_TOKEN: ${{ secrets.TURBO_TOKEN }}
-  TURBO_TEAM: quantified-uncertainty
+      - reducer-dev
+      - epic-reducer-project
+      - epic-0.5.0

 jobs:
-  build-test-lint:
-    name: Build, test, lint
+  pre_check:
+    name: Precheck for skipping redundant jobs
    runs-on: ubuntu-latest
+    outputs:
+      should_skip_lang: ${{ steps.skip_lang_check.outputs.should_skip }}
+      should_skip_components: ${{ steps.skip_components_check.outputs.should_skip }}
+      should_skip_website: ${{ steps.skip_website_check.outputs.should_skip }}
+      should_skip_vscodeext: ${{ steps.skip_vscodeext_check.outputs.should_skip }}
+      should_skip_cli: ${{ steps.skip_cli_check.outputs.should_skip }}
+    steps:
+      - id: skip_lang_check
+        name: Check if the changes are about squiggle-lang src files
+        uses: fkirc/skip-duplicate-actions@v5.1.0
+        with:
+          paths: '["packages/squiggle-lang/**"]'
+      - id: skip_components_check
+        name: Check if the changes are about components src files
+        uses: fkirc/skip-duplicate-actions@v5.1.0
+        with:
+          paths: '["packages/components/**"]'
+      - id: skip_website_check
+        name: Check if the changes are about website src files
+        uses: fkirc/skip-duplicate-actions@v5.1.0
+        with:
+          paths: '["packages/website/**"]'
+      - id: skip_vscodeext_check
+        name: Check if the changes are about vscode extension src files
+        uses: fkirc/skip-duplicate-actions@v5.1.0
+        with:
+          paths: '["packages/vscode-ext/**"]'
+      - id: skip_cli_check
+        name: Check if the changes are about cli src files
+        uses: fkirc/skip-duplicate-actions@v5.1.0
+        with:
+          paths: '["packages/cli/**"]'
+
+  lang-lint:
+    name: Language lint
+    runs-on: ubuntu-latest
+    needs: pre_check
+    if: ${{ needs.pre_check.outputs.should_skip_lang != 'true' }}
+    defaults:
+      run:
+        shell: bash
+        working-directory: packages/squiggle-lang
    steps:
      - uses: actions/checkout@v3
-      - name: Setup Node.js environment
-        uses: actions/setup-node@v3
+      - name: Install Dependencies
+        run: cd ../../ && yarn
+      - name: Check rescript lint
+        run: yarn lint:rescript
+      - name: Check javascript, typescript, and markdown lint
+        uses: creyD/prettier_action@v4.2
        with:
-          node-version: 16
-          cache: 'yarn'
-      - name: Install dependencies
-        run: yarn --frozen-lockfile
-      - name: Turbo run
-        run: npx turbo run build test lint bundle
+          dry: true
+          prettier_options: --check packages/squiggle-lang

-  coverage:
-    name: Coverage
+  lang-build-test-bundle:
+    name: Language build, test, and bundle
    runs-on: ubuntu-latest
+    needs: pre_check
+    if: ${{ needs.pre_check.outputs.should_skip_lang != 'true' }}
+    defaults:
+      run:
+        shell: bash
+        working-directory: packages/squiggle-lang
    steps:
      - uses: actions/checkout@v3
        with:
          fetch-depth: 2
-      - name: Setup Node.js environment
-        uses: actions/setup-node@v2
+      - name: Install dependencies from monorepo level
+        run: cd ../../ && yarn
+      - name: Build rescript codebase
+        run: yarn build
+      - name: Run rescript tests
+        run: yarn test:rescript
+      - name: Run typescript tests
+        run: yarn test:ts
+      - name: Run webpack
+        run: yarn bundle
+      - name: Upload rescript coverage report
+        run: yarn coverage:rescript:ci
+      - name: Upload typescript coverage report
+        run: yarn coverage:ts:ci
+
+  components-lint:
+    name: Components lint
+    runs-on: ubuntu-latest
+    needs: pre_check
+    if: ${{ needs.pre_check.outputs.should_skip_components != 'true' }}
+    defaults:
+      run:
+        shell: bash
+        working-directory: packages/components
+    steps:
+      - uses: actions/checkout@v3
+      - name: Check javascript, typescript, and markdown lint
+        uses: creyD/prettier_action@v4.2
        with:
-          node-version: 16
-          cache: 'yarn'
-      - name: Install dependencies
-        run: yarn
-      - name: Coverage
-        run: npx turbo run coverage
+          dry: true
+          prettier_options: --check packages/components --ignore-path packages/components/.prettierignore
+
+  components-bundle-build:
+    name: Components bundle and build
+    runs-on: ubuntu-latest
+    needs: pre_check
+    if: ${{ (needs.pre_check.outputs.should_skip_components != 'true') || (needs.pre_check.outputs.should_skip_lang != 'true') }}
+    defaults:
+      run:
+        shell: bash
+        working-directory: packages/components
+    steps:
+      - uses: actions/checkout@v3
+      - name: Install dependencies from monorepo level
+        run: cd ../../ && yarn
+      - name: Build rescript codebase in squiggle-lang
+        run: cd ../squiggle-lang && yarn build
+      - name: Run webpack
+        run: yarn bundle
+      - name: Build storybook
+        run: yarn build
+
+  website-lint:
+    name: Website lint
+    runs-on: ubuntu-latest
+    needs: pre_check
+    if: ${{ needs.pre_check.outputs.should_skip_website != 'true' }}
+    defaults:
+      run:
+        shell: bash
+        working-directory: packages/website
+    steps:
+      - uses: actions/checkout@v3
+      - name: Check javascript, typescript, and markdown lint
+        uses: creyD/prettier_action@v4.2
+        with:
+          dry: true
+          prettier_options: --check packages/website
+
+  website-build:
+    name: Website build
+    runs-on: ubuntu-latest
+    needs: pre_check
+    if: ${{ (needs.pre_check.outputs.should_skip_website != 'true') || (needs.pre_check.outputs.should_skip_lang != 'true')  || (needs.pre_check.outputs.should_skip_components != 'true') }}
+    defaults:
+      run:
+        shell: bash
+        working-directory: packages/website
+    steps:
+      - uses: actions/checkout@v3
+      - name: Install dependencies from monorepo level
+        run: cd ../../ && yarn
+      - name: Build rescript in squiggle-lang
+        run: cd ../squiggle-lang && yarn build
+      - name: Build components
+        run: cd ../components && yarn build
+      - name: Build website assets
+        run: yarn build
+
+  vscode-ext-lint:
+    name: VS Code extension lint
+    runs-on: ubuntu-latest
+    needs: pre_check
+    if: ${{ needs.pre_check.outputs.should_skip_vscodeext != 'true' }}
+    defaults:
+      run:
+        shell: bash
+        working-directory: packages/vscode-ext
+    steps:
+      - uses: actions/checkout@v3
+      - name: Check javascript, typescript, and markdown lint
+        uses: creyD/prettier_action@v4.2
+        with:
+          dry: true
+          prettier_options: --check packages/vscode-ext
+
+  vscode-ext-build:
+    name: VS Code extension build
+    runs-on: ubuntu-latest
+    needs: pre_check
+    if: ${{ (needs.pre_check.outputs.should_skip_components != 'true') || (needs.pre_check.outputs.should_skip_lang != 'true') }} || (needs.pre_check.outputs.should_skip_vscodeext != 'true') }}
+    defaults:
+      run:
+        shell: bash
+        working-directory: packages/vscode-ext
+    steps:
+      - uses: actions/checkout@v3
+      - name: Install dependencies from monorepo level
+        run: cd ../../ && yarn
+      - name: Build
+        run: yarn compile
+  cli-lint:
+    name: CLI lint
+    runs-on: ubuntu-latest
+    needs: pre_check
+    if: ${{ needs.pre_check.outputs.should_skip_cli != 'true' }}
+    defaults:
+      run:
+        shell: bash
+        working-directory: packages/cli
+    steps:
+      - uses: actions/checkout@v3
+      - name: Check javascript, typescript, and markdown lint
+        uses: creyD/prettier_action@v4.2
+        with:
+          dry: true
+          prettier_options: --check packages/cli
--- a/.github/workflows/release-please.yml
+++ b/.github/workflows/release-please.yml
@ -18,27 +18,27 @@ jobs:
    steps:
      - id: skip_lang_check
        name: Check if the changes are about squiggle-lang src files
-        uses: fkirc/skip-duplicate-actions@v5.2.0
+        uses: fkirc/skip-duplicate-actions@v5.1.0
        with:
          paths: '["packages/squiggle-lang/**"]'
      - id: skip_components_check
        name: Check if the changes are about components src files
-        uses: fkirc/skip-duplicate-actions@v5.2.0
+        uses: fkirc/skip-duplicate-actions@v5.1.0
        with:
          paths: '["packages/components/**"]'
      - id: skip_website_check
        name: Check if the changes are about website src files
-        uses: fkirc/skip-duplicate-actions@v5.2.0
+        uses: fkirc/skip-duplicate-actions@v5.1.0
        with:
          paths: '["packages/website/**"]'
      - id: skip_vscodeext_check
        name: Check if the changes are about vscode extension src files
-        uses: fkirc/skip-duplicate-actions@v5.2.0
+        uses: fkirc/skip-duplicate-actions@v5.1.0
        with:
          paths: '["packages/vscode-ext/**"]'
      - id: skip_cli_check
        name: Check if the changes are about cli src files
-        uses: fkirc/skip-duplicate-actions@v5.2.0
+        uses: fkirc/skip-duplicate-actions@v5.1.0
        with:
          paths: '["packages/cli/**"]'

--- a/.gitignore
+++ b/.gitignore
@ -11,5 +11,3 @@ yarn-error.log
 .vscode
 todo.txt
 result
-shell.nix
-.turbo
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@ -1 +0,0 @@
-See the [Changelog.mdx page](./packages/website/docs/Changelog.mdx) for the changelog.
--- a/README.md
+++ b/README.md
@ -51,25 +51,7 @@ For any project in the repo, begin by running `yarn` in the top level
 yarn
 ```

-Then use `turbo` to build the specific packages or the entire monorepo:
-
-```sh
-turbo run build
-```
-
-Or:
-
-```sh
-turbo run build --filter=@quri/squiggle-components
-```
-
-You can also run specific npm scripts for the package you're working on. See `packages/*/README.md` for the details.
-
-# NixOS users
-
-This repository requires the use of bundled binaries from node_modules, which
-are not linked statically. The easiest way to get them working is to enable
-[nix-ld](https://github.com/Mic92/nix-ld).
+See `packages/*/README.md` to work with whatever project you're interested in.

 # Contributing

--- a/nix/squiggle-lang.nix
+++ b/nix/squiggle-lang.nix
@ -30,6 +30,16 @@ rec {
          patchelf --replace-needed libstdc++.so.6 $THE_SO linux/ninja.exe && echo "- replaced needed for linux/ninja.exe"
        '';
      };
+      bisect_ppx = {
+        buildInputs = common.which;
+        postInstall = ''
+          echo "PATCHELF'ING BISECT_PPX EXECUTABLE"
+          THE_LD=$(patchelf --print-interpreter $(which mkdir))
+          patchelf --set-interpreter $THE_LD bin/linux/ppx
+          patchelf --set-interpreter $THE_LD bin/linux/bisect-ppx-report
+          cp bin/linux/ppx ppx
+        '';
+      };
      gentype = {
        postInstall = ''
          mv gentype.exe ELFLESS-gentype.exe
--- a/nixos.sh
+++ b/nixos.sh
@ -0,0 +1,18 @@
+#!/usr/bin/env bash
+# This script is only relevant if you're rolling nixos.
+
+# Esy (a bisect_ppx dependency/build tool) is borked on nixos without using an FHS shell. https://github.com/esy/esy/issues/858
+# We need to patchelf rescript executables. https://github.com/NixOS/nixpkgs/issues/107375
+set -x
+
+fhsShellName="squiggle-fhs-development"
+fhsShellDotNix="{pkgs ? import <nixpkgs> {} }: (pkgs.buildFHSUserEnv { name = \"${fhsShellName}\"; targetPkgs = pkgs: [pkgs.yarn pkgs.glibc]; runScript = \"yarn\"; }).env"
+nix-shell - <<<"$fhsShellDotNix"
+
+theLd=$(patchelf --print-interpreter $(which mkdir))
+patchelf --set-interpreter $theLd ./node_modules/gentype/gentype.exe
+patchelf --set-interpreter $theLd ./node_modules/rescript/linux/*.exe
+patchelf --set-interpreter $theLd ./node_modules/bisect_ppx/ppx
+patchelf --set-interpreter $theLd ./node_modules/bisect_ppx/bisect-ppx-report
+theSo=$(find /nix/store/*$fhsShellName*/lib64 -name libstdc++.so.6 | head -n 1)
+patchelf --replace-needed libstdc++.so.6 $theSo ./node_modules/rescript/linux/ninja.exe
--- a/package.json
+++ b/package.json
@ -2,11 +2,12 @@
  "private": true,
  "name": "squiggle",
  "scripts": {
-    "nodeclean": "rm -r node_modules && rm -r packages/*/node_modules"
+    "nodeclean": "rm -r node_modules && rm -r packages/*/node_modules",
+    "format:all": "prettier --write . && cd packages/squiggle-lang && yarn format",
+    "lint:all": "prettier --check . && cd packages/squiggle-lang && yarn lint:rescript"
  },
  "devDependencies": {
-    "prettier": "^2.7.1",
-    "turbo": "^1.5.5"
+    "prettier": "^2.7.1"
  },
  "workspaces": [
    "packages/*"
--- a/packages/cli/README.md
+++ b/packages/cli/README.md
@ -20,30 +20,3 @@ Runs compilation in the current directory and all of its subdirectories.
 ### `npx squiggle-cli-experimental watch`

 Watches `.squiggleU` files in the current directory (and subdirectories) and rebuilds them when they are saved. Note that this will _not_ rebuild files when their dependencies are changed, just when they are changed directly.
-
-## Further instructions
-
-The above requires having node, npm and npx. To install the first two, see [here](https://nodejs.org/en/), to install npx, run:
-
-```
-npm install -g npx
-```
-
-Alternatively, you can run the following without the need for npx:
-
-```
-npm install squiggle-cli-experimental
-node node_modules/squiggle-cli-experimental/index.js compile
-```
-
-or you can add a script to your `package.json`, like:
-
-```
- ...
- scripts: {
-  "compile": "squiggle-cli-experimental compile"
- }
- ...
-```
-
-This can be run with `npm run compile`. `npm` knows how to reach into the node_modules directly, so it's not necessary to specify that.
--- a/packages/cli/package.json
+++ b/packages/cli/package.json
@ -7,15 +7,13 @@
  "bin": "index.js",
  "type": "module",
  "scripts": {
-    "start": "node .",
-    "lint": "prettier --check .",
-    "format": "prettier --write ."
+    "start": "node ."
  },
  "license": "MIT",
  "dependencies": {
-    "chalk": "^5.1.0",
+    "chalk": "^5.0.1",
    "chokidar": "^3.5.3",
-    "commander": "^9.4.1",
+    "commander": "^9.4.0",
    "fs": "^0.0.1-security",
    "glob": "^8.0.3",
    "indent-string": "^5.0.0"
--- a/packages/components/jest.config.js
+++ b/packages/components/jest.config.js
@ -1,6 +0,0 @@
-/** @type {import('ts-jest').JestConfigWithTsJest} */
-module.exports = {
-  preset: "ts-jest",
-  setupFilesAfterEnv: ["<rootDir>/test/setup.js"],
-  testEnvironment: "jsdom",
-};
--- a/packages/components/package.json
+++ b/packages/components/package.json
@ -5,21 +5,19 @@
  "dependencies": {
    "@floating-ui/react-dom": "^1.0.0",
    "@floating-ui/react-dom-interactions": "^0.10.1",
-    "@headlessui/react": "^1.7.3",
+    "@headlessui/react": "^1.7.2",
    "@heroicons/react": "^1.0.6",
    "@hookform/resolvers": "^2.9.8",
    "@quri/squiggle-lang": "^0.5.0",
    "@react-hook/size": "^2.1.2",
-    "@types/uuid": "^8.3.4",
    "clsx": "^1.2.1",
-    "framer-motion": "^7.5.3",
+    "framer-motion": "^7.4.0",
    "lodash": "^4.17.21",
    "react": "^18.1.0",
    "react-ace": "^10.1.0",
-    "react-hook-form": "^7.37.0",
+    "react-hook-form": "^7.36.1",
    "react-use": "^17.4.0",
    "react-vega": "^7.6.0",
-    "uuid": "^9.0.0",
    "vega": "^5.22.1",
    "vega-embed": "^6.21.0",
    "vega-lite": "^5.5.0",
@ -40,17 +38,12 @@
    "@testing-library/react": "^13.4.0",
    "@testing-library/user-event": "^14.4.3",
    "@types/jest": "^27.5.0",
-    "@types/lodash": "^4.14.186",
-    "@types/node": "^18.8.3",
+    "@types/lodash": "^4.14.185",
+    "@types/node": "^18.7.22",
    "@types/react": "^18.0.21",
    "@types/styled-components": "^5.1.26",
-    "@types/uuid": "^8.3.4",
    "@types/webpack": "^5.28.0",
-    "canvas": "^2.10.1",
    "cross-env": "^7.0.3",
-    "jest": "^29.0.3",
-    "jest-environment-jsdom": "^29.1.2",
-    "jsdom": "^20.0.1",
    "mini-css-extract-plugin": "^2.6.1",
    "postcss-cli": "^10.0.0",
    "postcss-import": "^15.0.0",
@ -60,11 +53,10 @@
    "react-scripts": "^5.0.1",
    "style-loader": "^3.3.1",
    "tailwindcss": "^3.1.8",
-    "ts-jest": "^29.0.3",
    "ts-loader": "^9.4.1",
    "tsconfig-paths-webpack-plugin": "^4.0.0",
-    "typescript": "^4.8.4",
-    "web-vitals": "^3.0.3",
+    "typescript": "^4.8.3",
+    "web-vitals": "^3.0.2",
    "webpack": "^5.74.0",
    "webpack-cli": "^4.10.0",
    "webpack-dev-server": "^4.11.1"
@ -83,10 +75,7 @@
    "all": "yarn bundle && yarn build",
    "lint": "prettier --check .",
    "format": "prettier --write .",
-    "prepack": "yarn run build:cjs && yarn run bundle",
-    "test": "jest",
-    "test:debug": "node --inspect-brk node_modules/.bin/jest --runInBand",
-    "test:profile": "node --cpu-prof node_modules/.bin/jest --runInBand"
+    "prepack": "yarn run build:cjs && yarn run bundle"
  },
  "eslintConfig": {
    "extends": [
--- a/packages/components/src/components/Alert.tsx
+++ b/packages/components/src/components/Alert.tsx
@ -24,13 +24,13 @@ export const Alert: React.FC<{
  children,
 }) => {
  return (
-    <div className={clsx("rounded-md p-4", backgroundColor)} role="status">
+    <div className={clsx("rounded-md p-4", backgroundColor)}>
      <div className="flex">
        <Icon
          className={clsx("h-5 w-5 flex-shrink-0", iconColor)}
          aria-hidden="true"
        />
-        <div className="ml-3 grow">
+        <div className="ml-3">
          <header className={clsx("text-sm font-medium", headingColor)}>
            {heading}
          </header>
--- a/packages/components/src/components/CodeEditor.tsx
+++ b/packages/components/src/components/CodeEditor.tsx
@ -5,8 +5,6 @@ import AceEditor from "react-ace";
 import "ace-builds/src-noconflict/mode-golang";
 import "ace-builds/src-noconflict/theme-github";

-import { SqLocation } from "@quri/squiggle-lang";
-
 interface CodeEditorProps {
  value: string;
  onChange: (value: string) => void;
@ -15,17 +13,15 @@ interface CodeEditorProps {
  width?: number;
  height: number;
  showGutter?: boolean;
-  errorLocations?: SqLocation[];
 }

 export const CodeEditor: FC<CodeEditorProps> = ({
  value,
  onChange,
  onSubmit,
-  height,
  oneLine = false,
  showGutter = false,
-  errorLocations = [],
+  height,
 }) => {
  const lineCount = value.split("\n").length;
  const id = useMemo(() => _.uniqueId(), []);
@ -34,11 +30,8 @@ export const CodeEditor: FC<CodeEditorProps> = ({
  const onSubmitRef = useRef<typeof onSubmit | null>(null);
  onSubmitRef.current = onSubmit;

-  const editorEl = useRef<AceEditor | null>(null);
-
  return (
    <AceEditor
-      ref={editorEl}
      value={value}
      mode="golang"
      theme="github"
@ -55,7 +48,10 @@ export const CodeEditor: FC<CodeEditorProps> = ({
      editorProps={{
        $blockScrolling: true,
      }}
-      setOptions={{}}
+      setOptions={{
+        enableBasicAutocompletion: false,
+        enableLiveAutocompletion: false,
+      }}
      commands={[
        {
          name: "submit",
@ -63,14 +59,6 @@ export const CodeEditor: FC<CodeEditorProps> = ({
          exec: () => onSubmitRef.current?.(),
        },
      ]}
-      markers={errorLocations?.map((location) => ({
-        startRow: location.start.line - 1,
-        startCol: location.start.column - 1,
-        endRow: location.end.line - 1,
-        endCol: location.end.column - 1,
-        className: "ace-error-marker",
-        type: "text",
-      }))}
    />
  );
 };
--- a/packages/components/src/components/DistributionChart.tsx
+++ b/packages/components/src/components/DistributionChart.tsx
@ -83,32 +83,18 @@ export const DistributionChart: React.FC<DistributionChartProps> = (props) => {
      }
    }

-    const domain = shapes.value.flatMap((shape) =>
-      shape.discrete.concat(shape.continuous)
-    );
+    const spec = buildVegaSpec(props);

-    const spec = buildVegaSpec({
-      ...props,
-      minX: props.minX ?? Math.min(...domain.map((x) => x.x)),
-      maxX: props.minX ?? Math.max(...domain.map((x) => x.x)),
-      maxY: Math.max(...domain.map((x) => x.y)),
-    });
-
-    // I think size.width is sometimes not finite due to the component not being in a visible context
-    // This occurs during testing
-    let widthProp = width
-      ? width
-      : Number.isFinite(size.width)
-      ? size.width
-      : 400;
+    let widthProp = width ? width : size.width;
    if (widthProp < 20) {
      console.warn(
        `Width of Distribution is set to ${widthProp}, which is too small`
      );
      widthProp = 20;
    }
-
-    const vegaData = { data: shapes.value, samples };
+    const domain = shapes.value.flatMap((shape) =>
+      shape.discrete.concat(shape.continuous)
+    );

    return (
      <div style={{ width: widthProp }}>
@ -119,7 +105,7 @@ export const DistributionChart: React.FC<DistributionChartProps> = (props) => {
        ) : (
          <Vega
            spec={spec}
-            data={vegaData}
+            data={{ data: shapes.value, domain, samples }}
            width={widthProp - 10}
            height={height}
            actions={actions}
--- a/packages/components/src/components/FunctionChart.tsx
+++ b/packages/components/src/components/FunctionChart.tsx
@ -1,15 +1,9 @@
 import * as React from "react";
-import {
-  SqLambda,
-  environment,
-  SqValueTag,
-  SqError,
-} from "@quri/squiggle-lang";
+import { SqLambda, environment, SqValueTag } from "@quri/squiggle-lang";
 import { FunctionChart1Dist } from "./FunctionChart1Dist";
 import { FunctionChart1Number } from "./FunctionChart1Number";
 import { DistributionPlottingSettings } from "./DistributionChart";
-import { MessageAlert } from "./Alert";
-import { SquiggleErrorAlert } from "./SquiggleErrorAlert";
+import { ErrorAlert, MessageAlert } from "./Alert";

 export type FunctionChartSettings = {
  start: number;
@ -25,25 +19,6 @@ interface FunctionChartProps {
  height: number;
 }

-const FunctionCallErrorAlert = ({ error }: { error: SqError }) => {
-  const [expanded, setExpanded] = React.useState(false);
-  if (expanded) {
-  }
-  return (
-    <MessageAlert heading="Function Display Failed">
-      <div className="space-y-2">
-        <span
-          className="underline decoration-dashed cursor-pointer"
-          onClick={() => setExpanded(!expanded)}
-        >
-          {expanded ? "Hide" : "Show"} error details
-        </span>
-        {expanded ? <SquiggleErrorAlert error={error} /> : null}
-      </div>
-    </MessageAlert>
-  );
-};
-
 export const FunctionChart: React.FC<FunctionChartProps> = ({
  fn,
  chartSettings,
@ -51,8 +26,7 @@ export const FunctionChart: React.FC<FunctionChartProps> = ({
  distributionPlotSettings,
  height,
 }) => {
-  console.log(fn.parameters().length);
-  if (fn.parameters().length !== 1) {
+  if (fn.parameters.length > 1) {
    return (
      <MessageAlert heading="Function Display Not Supported">
        Only functions with one parameter are displayed.
@ -73,7 +47,9 @@ export const FunctionChart: React.FC<FunctionChartProps> = ({
  const validResult = getValidResult();

  if (validResult.tag === "Error") {
-    return <FunctionCallErrorAlert error={validResult.value} />;
+    return (
+      <ErrorAlert heading="Error">{validResult.value.toString()}</ErrorAlert>
+    );
  }

  switch (validResult.value.tag) {
--- a/packages/components/src/components/SquiggleChart.tsx
+++ b/packages/components/src/components/SquiggleChart.tsx
@ -2,21 +2,23 @@ import * as React from "react";
 import {
  SqValue,
  environment,
-  SqProject,
  defaultEnvironment,
+  resultMap,
+  SqValueTag,
 } from "@quri/squiggle-lang";
 import { useSquiggle } from "../lib/hooks";
 import { SquiggleViewer } from "./SquiggleViewer";
 import { JsImports } from "../lib/jsImports";
-import { getValueToRender } from "../lib/utility";

-export type SquiggleChartProps = {
+export interface SquiggleChartProps {
  /** The input string for squiggle */
-  code: string;
+  code?: string;
  /** Allows to re-run the code if code hasn't changed */
  executionId?: number;
  /** If the output requires monte carlo sampling, the amount of samples */
  sampleCount?: number;
+  /** The amount of points returned to draw the distribution */
+  environment?: environment;
  /** If the result is a function, where the function domain starts */
  diagramStart?: number;
  /** If the result is a function, where the function domain ends */
@ -24,7 +26,7 @@ export type SquiggleChartProps = {
  /** If the result is a function, the amount of stops sampled */
  diagramCount?: number;
  /** When the squiggle code gets reevaluated */
-  onChange?(expr: SqValue | undefined, sourceName: string): void;
+  onChange?(expr: SqValue | undefined): void;
  /** CSS width of the element */
  width?: number;
  height?: number;
@ -51,30 +53,21 @@ export type SquiggleChartProps = {
  /** Whether to show vega actions to the user, so they can copy the chart spec */
  distributionChartActions?: boolean;
  enableLocalSettings?: boolean;
-} & (StandaloneExecutionProps | ProjectExecutionProps);
+}

-// Props needed for a standalone execution
-type StandaloneExecutionProps = {
-  project?: undefined;
-  continues?: undefined;
-  /** The amount of points returned to draw the distribution, not needed if using a project */
-  environment?: environment;
-};
-
-// Props needed when executing inside a project.
-type ProjectExecutionProps = {
-  environment?: undefined;
-  /** The project that this execution is part of */
-  project: SqProject;
-  /** What other squiggle sources from the project to continue. Default [] */
-  continues?: string[];
-};
 const defaultOnChange = () => {};
 const defaultImports: JsImports = {};

-export const splitSquiggleChartSettings = (props: SquiggleChartProps) => {
-  const {
+export const SquiggleChart: React.FC<SquiggleChartProps> = React.memo(
+  ({
+    code = "",
+    executionId = 0,
+    environment,
+    onChange = defaultOnChange, // defaultOnChange must be constant, don't move its definition here
+    height = 200,
+    jsImports = defaultImports,
    showSummary = false,
+    width,
    logX = false,
    expY = false,
    diagramStart = 0,
@ -87,7 +80,15 @@ export const splitSquiggleChartSettings = (props: SquiggleChartProps) => {
    title,
    xAxisType = "number",
    distributionChartActions,
-  } = props;
+    enableLocalSettings = false,
+  }) => {
+    const { result, bindings } = useSquiggle({
+      code,
+      environment,
+      jsImports,
+      onChange,
+      executionId,
+    });

    const distributionPlotSettings = {
      showSummary,
@ -108,49 +109,18 @@ export const splitSquiggleChartSettings = (props: SquiggleChartProps) => {
      count: diagramCount,
    };

-  return { distributionPlotSettings, chartSettings };
-};
-
-export const SquiggleChart: React.FC<SquiggleChartProps> = React.memo(
-  (props) => {
-    const { distributionPlotSettings, chartSettings } =
-      splitSquiggleChartSettings(props);
-
-    const {
-      code,
-      jsImports = defaultImports,
-      onChange = defaultOnChange, // defaultOnChange must be constant, don't move its definition here
-      executionId = 0,
-      width,
-      height = 200,
-      enableLocalSettings = false,
-      continues,
-      project,
-      environment,
-    } = props;
-
-    const resultAndBindings = useSquiggle({
-      environment,
-      continues,
-      project,
-      code,
-      jsImports,
-      onChange,
-      executionId,
-    });
-
-    const valueToRender = getValueToRender(resultAndBindings);
+    const resultToRender = resultMap(result, (value) =>
+      value.tag === SqValueTag.Void ? bindings.asValue() : value
+    );

    return (
      <SquiggleViewer
-        result={valueToRender}
+        result={resultToRender}
        width={width}
        height={height}
        distributionPlotSettings={distributionPlotSettings}
        chartSettings={chartSettings}
-        environment={
-          project ? project.getEnvironment() : environment ?? defaultEnvironment
-        }
+        environment={environment ?? defaultEnvironment}
        enableLocalSettings={enableLocalSettings}
      />
    );
--- a/packages/components/src/components/SquiggleEditor.tsx
+++ b/packages/components/src/components/SquiggleEditor.tsx
@ -1,29 +1,20 @@
 import React from "react";
 import { CodeEditor } from "./CodeEditor";
 import { SquiggleContainer } from "./SquiggleContainer";
-import {
-  splitSquiggleChartSettings,
-  SquiggleChartProps,
-} from "./SquiggleChart";
-import { useMaybeControlledValue, useSquiggle } from "../lib/hooks";
-import { JsImports } from "../lib/jsImports";
-import { defaultEnvironment, SqLocation, SqProject } from "@quri/squiggle-lang";
-import { SquiggleViewer } from "./SquiggleViewer";
-import { getErrorLocations, getValueToRender } from "../lib/utility";
+import { SquiggleChart, SquiggleChartProps } from "./SquiggleChart";
+import { useMaybeControlledValue } from "../lib/hooks";

 const WrappedCodeEditor: React.FC<{
  code: string;
  setCode: (code: string) => void;
-  errorLocations?: SqLocation[];
-}> = ({ code, setCode, errorLocations }) => (
-  <div className="border border-grey-200 p-2 m-4" data-testid="squiggle-editor">
+}> = ({ code, setCode }) => (
+  <div className="border border-grey-200 p-2 m-4">
    <CodeEditor
      value={code}
      onChange={setCode}
      oneLine={true}
      showGutter={false}
      height={20}
-      errorLocations={errorLocations}
    />
  </div>
 );
@ -33,9 +24,6 @@ export type SquiggleEditorProps = SquiggleChartProps & {
  onCodeChange?: (code: string) => void;
 };

-const defaultOnChange = () => {};
-const defaultImports: JsImports = {};
-
 export const SquiggleEditor: React.FC<SquiggleEditorProps> = (props) => {
  const [code, setCode] = useMaybeControlledValue({
    value: props.code,
@ -43,50 +31,11 @@ export const SquiggleEditor: React.FC<SquiggleEditorProps> = (props) => {
    onChange: props.onCodeChange,
  });

-  const { distributionPlotSettings, chartSettings } =
-    splitSquiggleChartSettings(props);
-
-  const {
-    environment,
-    jsImports = defaultImports,
-    onChange = defaultOnChange, // defaultOnChange must be constant, don't move its definition here
-    executionId = 0,
-    width,
-    height = 200,
-    enableLocalSettings = false,
-    continues,
-    project,
-  } = props;
-
-  const resultAndBindings = useSquiggle({
-    environment,
-    continues,
-    code,
-    project,
-    jsImports,
-    onChange,
-    executionId,
-  });
-
-  const valueToRender = getValueToRender(resultAndBindings);
-  const errorLocations = getErrorLocations(resultAndBindings.result);
-
+  let chartProps = { ...props, code };
  return (
    <SquiggleContainer>
-      <WrappedCodeEditor
-        code={code}
-        setCode={setCode}
-        errorLocations={errorLocations}
-      />
-      <SquiggleViewer
-        result={valueToRender}
-        width={width}
-        height={height}
-        distributionPlotSettings={distributionPlotSettings}
-        chartSettings={chartSettings}
-        environment={environment ?? defaultEnvironment}
-        enableLocalSettings={enableLocalSettings}
-      />
+      <WrappedCodeEditor code={code} setCode={setCode} />
+      <SquiggleChart {...chartProps} />
    </SquiggleContainer>
  );
 };
--- a/packages/components/src/components/SquiggleErrorAlert.tsx
+++ b/packages/components/src/components/SquiggleErrorAlert.tsx
@ -1,4 +1,4 @@
-import { SqError, SqFrame } from "@quri/squiggle-lang";
+import { SqError } from "@quri/squiggle-lang";
 import React from "react";
 import { ErrorAlert } from "./Alert";

@ -6,39 +6,6 @@ type Props = {
  error: SqError;
 };

-const StackTraceFrame: React.FC<{ frame: SqFrame }> = ({ frame }) => {
-  const location = frame.location();
-  return (
-    <div>
-      {frame.name()}
-      {location
-        ? ` at line ${location.start.line}, column ${location.start.column}`
-        : ""}
-    </div>
-  );
-};
-
-const StackTrace: React.FC<Props> = ({ error }) => {
-  const frames = error.getFrameArray();
-  return frames.length ? (
-    <div>
-      <div className="font-medium">Stack trace:</div>
-      <div className="ml-4">
-        {frames.map((frame, i) => (
-          <StackTraceFrame frame={frame} key={i} />
-        ))}
-      </div>
-    </div>
-  ) : null;
-};
-
 export const SquiggleErrorAlert: React.FC<Props> = ({ error }) => {
-  return (
-    <ErrorAlert heading="Error">
-      <div className="space-y-4">
-        <div>{error.toString()}</div>
-        <StackTrace error={error} />
-      </div>
-    </ErrorAlert>
-  );
+  return <ErrorAlert heading="Error">{error.toString()}</ErrorAlert>;
 };
--- a/packages/components/src/components/SquigglePlayground.tsx
+++ b/packages/components/src/components/SquigglePlayground.tsx
@ -8,11 +8,7 @@ import React, {
 } from "react";
 import { useForm, UseFormRegister, useWatch } from "react-hook-form";
 import * as yup from "yup";
-import {
-  useMaybeControlledValue,
-  useRunnerState,
-  useSquiggle,
-} from "../lib/hooks";
+import { useMaybeControlledValue, useRunnerState } from "../lib/hooks";
 import { yupResolver } from "@hookform/resolvers/yup";
 import {
  ChartSquareBarIcon,
@ -28,9 +24,9 @@ import {
 } from "@heroicons/react/solid";
 import clsx from "clsx";

-import { environment, SqProject } from "@quri/squiggle-lang";
+import { environment } from "@quri/squiggle-lang";

-import { SquiggleChartProps } from "./SquiggleChart";
+import { SquiggleChart, SquiggleChartProps } from "./SquiggleChart";
 import { CodeEditor } from "./CodeEditor";
 import { JsonEditor } from "./JsonEditor";
 import { ErrorAlert, SuccessAlert } from "./Alert";
@ -44,8 +40,6 @@ import { HeadedSection } from "./ui/HeadedSection";
 import { defaultTickFormat } from "../lib/distributionSpecBuilder";
 import { Button } from "./ui/Button";
 import { JsImports } from "../lib/jsImports";
-import { getErrorLocations, getValueToRender } from "../lib/utility";
-import { SquiggleViewer } from "./SquiggleViewer";

 type PlaygroundProps = SquiggleChartProps & {
  /** The initial squiggle string to put in the playground */
@ -182,7 +176,7 @@ const RunControls: React.FC<{
  const CurrentPlayIcon = isRunning ? RefreshIcon : PlayIcon;

  return (
-    <div className="flex space-x-1 items-center" data-testid="autorun-controls">
+    <div className="flex space-x-1 items-center">
      {autorunMode ? null : (
        <button onClick={run}>
          <CurrentPlayIcon
@ -251,8 +245,6 @@ export const SquigglePlayground: FC<PlaygroundProps> = ({
  onSettingsChange,
  showEditor = true,
  showShareButton = false,
-  continues,
-  project,
 }) => {
  const [code, setCode] = useMaybeControlledValue({
    value: controlledCode,
@ -290,7 +282,7 @@ export const SquigglePlayground: FC<PlaygroundProps> = ({
    onSettingsChange?.(vars);
  }, [vars, onSettingsChange]);

-  const environment: environment = useMemo(
+  const env: environment = useMemo(
    () => ({
      sampleCount: Number(vars.sampleCount),
      xyPointLength: Number(vars.xyPointLength),
@ -307,53 +299,26 @@ export const SquigglePlayground: FC<PlaygroundProps> = ({
    executionId,
  } = useRunnerState(code);

-  const resultAndBindings = useSquiggle({
-    environment,
-    continues,
-    code: renderedCode,
-    project,
-    jsImports: imports,
-    executionId,
-  });
-
-  const valueToRender = getValueToRender(resultAndBindings);
-
  const squiggleChart =
    renderedCode === "" ? null : (
      <div className="relative">
        {isRunning ? (
          <div className="absolute inset-0 bg-white opacity-0 animate-semi-appear" />
        ) : null}
-        <SquiggleViewer
-          result={valueToRender}
-          environment={environment}
-          height={vars.chartHeight || 150}
-          distributionPlotSettings={{
-            showSummary: vars.showSummary ?? false,
-            logX: vars.logX ?? false,
-            expY: vars.expY ?? false,
-            format: vars.tickFormat,
-            minX: vars.minX,
-            maxX: vars.maxX,
-            title: vars.title,
-            actions: vars.distributionChartActions,
-          }}
-          chartSettings={{
-            start: vars.diagramStart ?? 0,
-            stop: vars.diagramStop ?? 10,
-            count: vars.diagramCount ?? 20,
-          }}
+        <SquiggleChart
+          code={renderedCode}
+          executionId={executionId}
+          environment={env}
+          {...vars}
+          jsImports={imports}
          enableLocalSettings={true}
        />
      </div>
    );

-  const errorLocations = getErrorLocations(resultAndBindings.result);
-
  const firstTab = vars.showEditor ? (
-    <div className="border border-slate-200" data-testid="squiggle-editor">
+    <div className="border border-slate-200">
      <CodeEditor
-        errorLocations={errorLocations}
        value={code}
        onChange={setCode}
        onSubmit={run}
@ -403,9 +368,7 @@ export const SquigglePlayground: FC<PlaygroundProps> = ({
      >
        {tabs}
      </div>
-      <div className="w-1/2 p-2 pl-4" data-testid="playground-result">
-        {squiggleChart}
-      </div>
+      <div className="w-1/2 p-2 pl-4">{squiggleChart}</div>
    </div>
  );

--- a/packages/components/src/components/SquiggleViewer/ExpressionViewer.tsx
+++ b/packages/components/src/components/SquiggleViewer/ExpressionViewer.tsx
@ -2,7 +2,7 @@ import React, { useContext } from "react";
 import { SqDistributionTag, SqValue, SqValueTag } from "@quri/squiggle-lang";
 import { NumberShower } from "../NumberShower";
 import { DistributionChart, defaultPlot, makePlot } from "../DistributionChart";
-import { FunctionChart } from "../FunctionChart";
+import { FunctionChart, FunctionChartSettings } from "../FunctionChart";
 import clsx from "clsx";
 import { VariableBox } from "./VariableBox";
 import { ItemSettingsMenu } from "./ItemSettingsMenu";
--- a/packages/components/src/components/SquiggleViewer/VariableBox.tsx
+++ b/packages/components/src/components/SquiggleViewer/VariableBox.tsx
@ -1,4 +1,4 @@
-import { SqValue } from "@quri/squiggle-lang";
+import { SqValue, SqValueLocation } from "@quri/squiggle-lang";
 import React, { useContext, useReducer } from "react";
 import { Tooltip } from "../ui/Tooltip";
 import { LocalItemSettings, MergedItemSettings } from "./utils";
@ -45,7 +45,7 @@ export const VariableBox: React.FC<VariableBoxProps> = ({
    : location.path.items[location.path.items.length - 1];

  return (
-    <div role={isTopLevel ? "status" : undefined}>
+    <div>
      <header className="inline-flex space-x-1">
        <Tooltip text={heading}>
          <span
@ -70,7 +70,7 @@ export const VariableBox: React.FC<VariableBoxProps> = ({
        <div className="flex w-full">
          {location.path.items.length ? (
            <div
-              className="shrink-0 border-l-2 border-slate-200 hover:border-indigo-600 w-4 cursor-pointer"
+              className="border-l-2 border-slate-200 hover:border-indigo-600 w-4 cursor-pointer"
              onClick={toggleCollapsed}
            ></div>
          ) : null}
--- a/packages/components/src/index.ts
+++ b/packages/components/src/index.ts
@ -1,4 +1,3 @@
-export { SqProject } from "@quri/squiggle-lang/";
 export { SquiggleChart } from "./components/SquiggleChart";
 export { SquiggleEditor } from "./components/SquiggleEditor";
 export { SquigglePlayground } from "./components/SquigglePlayground";
--- a/packages/components/src/lib/distributionSpecBuilder.ts
+++ b/packages/components/src/lib/distributionSpecBuilder.ts
@ -26,6 +26,7 @@ export const linearXScale: LinearScale = {
  range: "width",
  zero: false,
  nice: false,
+  domain: { data: "domain", field: "x" },
 };

 export const logXScale: LogScale = {
@ -36,6 +37,7 @@ export const logXScale: LogScale = {
  base: 10,
  nice: false,
  clamp: true,
+  domain: { data: "domain", field: "x" },
 };

 export const timeXScale: TimeScale = {
@ -44,6 +46,7 @@ export const timeXScale: TimeScale = {
  type: "time",
  range: "width",
  nice: false,
+  domain: { data: "domain", field: "x" },
 };

 /** Y Scales */
@ -52,6 +55,7 @@ export const linearYScale: LinearScale = {
  type: "linear",
  range: "height",
  zero: true,
+  domain: { data: "domain", field: "y" },
 };

 export const expYScale: PowScale = {
@ -61,6 +65,7 @@ export const expYScale: PowScale = {
  range: "height",
  zero: true,
  nice: false,
+  domain: { data: "domain", field: "y" },
 };

 export const defaultTickFormat = ".9~s";
@ -68,17 +73,9 @@ export const timeTickFormat = "%b %d, %Y %H:%M";
 const width = 500;

 export function buildVegaSpec(
-  specOptions: DistributionChartSpecOptions & { maxY: number }
+  specOptions: DistributionChartSpecOptions
 ): VisualizationSpec {
-  const {
-    title,
-    minX,
-    maxX,
-    logX,
-    expY,
-    xAxisType = "number",
-    maxY,
-  } = specOptions;
+  const { title, minX, maxX, logX, expY, xAxisType = "number" } = specOptions;

  const dateTime = xAxisType === "dateTime";

@ -91,15 +88,13 @@ export function buildVegaSpec(

  let xScale = dateTime ? timeXScale : logX ? logXScale : linearXScale;

-  xScale = {
-    ...xScale,
-    domain: [minX ?? 0, maxX ?? 1],
-    domainMin: minX,
-    domainMax: maxX,
-  };
+  if (minX !== undefined && Number.isFinite(minX)) {
+    xScale = { ...xScale, domainMin: minX };
+  }

-  let yScale = expY ? expYScale : linearYScale;
-  yScale = { ...yScale, domain: [0, maxY ?? 1], domainMin: 0, domainMax: maxY };
+  if (maxX !== undefined && Number.isFinite(maxX)) {
+    xScale = { ...xScale, domainMax: maxX };
+  }

  const spec: VisualizationSpec = {
    $schema: "https://vega.github.io/schema/vega/v5.json",
@ -133,7 +128,7 @@ export function buildVegaSpec(
    ],
    scales: [
      xScale,
-      yScale,
+      expY ? expYScale : linearYScale,
      {
        name: "color",
        type: "ordinal",
--- a/packages/components/src/lib/hooks/useSquiggle.ts
+++ b/packages/components/src/lib/hooks/useSquiggle.ts
@ -1,97 +1,42 @@
-import {
-  result,
-  SqError,
-  SqProject,
-  SqRecord,
-  SqValue,
-  environment,
-} from "@quri/squiggle-lang";
+import { environment, SqProject, SqValue } from "@quri/squiggle-lang";
 import { useEffect, useMemo } from "react";
 import { JsImports, jsImportsToSquiggleCode } from "../jsImports";
-import * as uuid from "uuid";

 type SquiggleArgs = {
-  environment?: environment;
  code: string;
  executionId?: number;
  jsImports?: JsImports;
-  project?: SqProject;
-  continues?: string[];
-  onChange?: (expr: SqValue | undefined, sourceName: string) => void;
+  environment?: environment;
+  onChange?: (expr: SqValue | undefined) => void;
 };

-export type ResultAndBindings = {
-  result: result<SqValue, SqError>;
-  bindings: SqRecord;
-};
-
-const importSourceName = (sourceName: string) => "imports-" + sourceName;
-const defaultContinues = [];
-
-export const useSquiggle = (args: SquiggleArgs): ResultAndBindings => {
-  const project = useMemo(() => {
-    if (args.project) {
-      return args.project;
-    } else {
-      const p = SqProject.create();
-      if (args.environment) {
-        p.setEnvironment(args.environment);
-      }
-      return p;
-    }
-  }, [args.project, args.environment]);
-
-  const sourceName = useMemo(() => uuid.v4(), []);
-
-  const env = project.getEnvironment();
-  const continues = args.continues || defaultContinues;
-
+export const useSquiggle = (args: SquiggleArgs) => {
  const result = useMemo(
    () => {
-      project.setSource(sourceName, args.code);
-      let fullContinues = continues;
+      const project = SqProject.create();
+      project.setSource("main", args.code);
+      if (args.environment) {
+        project.setEnvironment(args.environment);
+      }
      if (args.jsImports && Object.keys(args.jsImports).length) {
        const importsSource = jsImportsToSquiggleCode(args.jsImports);
-        project.setSource(importSourceName(sourceName), importsSource);
-        fullContinues = continues.concat(importSourceName(sourceName));
+        project.setSource("imports", importsSource);
+        project.setContinues("main", ["imports"]);
      }
-      project.setContinues(sourceName, fullContinues);
-      project.run(sourceName);
-      const result = project.getResult(sourceName);
-      const bindings = project.getBindings(sourceName);
+      project.run("main");
+      const result = project.getResult("main");
+      const bindings = project.getBindings("main");
      return { result, bindings };
    },
-    // This complains about executionId not being used inside the function body.
-    // This is on purpose, as executionId simply allows you to run the squiggle
-    // code again
    // eslint-disable-next-line react-hooks/exhaustive-deps
-    [
-      args.code,
-      args.jsImports,
-      args.executionId,
-      sourceName,
-      continues,
-      project,
-      env,
-    ]
+    [args.code, args.environment, args.jsImports, args.executionId]
  );

  const { onChange } = args;

  useEffect(() => {
-    onChange?.(
-      result.result.tag === "Ok" ? result.result.value : undefined,
-      sourceName
-    );
-  }, [result, onChange, sourceName]);
-
-  useEffect(() => {
-    return () => {
-      project.removeSource(sourceName);
-      if (project.getSource(importSourceName(sourceName)))
-        project.removeSource(importSourceName(sourceName));
-    };
-  }, [project, sourceName]);
+    onChange?.(result.result.tag === "Ok" ? result.result.value : undefined);
+  }, [result, onChange]);

  return result;
 };
--- a/packages/components/src/lib/utility.ts
+++ b/packages/components/src/lib/utility.ts
@ -1,5 +1,4 @@
-import { result, resultMap, SqValueTag } from "@quri/squiggle-lang";
-import { ResultAndBindings } from "./hooks/useSquiggle";
+import { result } from "@quri/squiggle-lang";

 export function flattenResult<a, b>(x: result<a, b>[]): result<a[], b> {
  if (x.length === 0) {
@ -36,18 +35,3 @@ export function all(arr: boolean[]): boolean {
 export function some(arr: boolean[]): boolean {
  return arr.reduce((x, y) => x || y, false);
 }
-
-export function getValueToRender({ result, bindings }: ResultAndBindings) {
-  return resultMap(result, (value) =>
-    value.tag === SqValueTag.Void ? bindings.asValue() : value
-  );
-}
-
-export function getErrorLocations(result: ResultAndBindings["result"]) {
-  if (result.tag === "Error") {
-    const location = result.value.location();
-    return location ? [location] : [];
-  } else {
-    return [];
-  }
-}
--- a/packages/components/src/styles/main.css
+++ b/packages/components/src/styles/main.css
@ -22,8 +22,3 @@ but this line is still necessary for proper initialization of `--tw-*` variables
 .ace_cursor {
  border-left: 2px solid !important;
 }
-
-.ace-error-marker {
-  position: absolute;
-  border-bottom: 1px solid red;
-}
--- a/packages/components/test/autorun.test.tsx
+++ b/packages/components/test/autorun.test.tsx
@ -1,55 +0,0 @@
-import { render, screen, waitFor, within } from "@testing-library/react";
-import userEvent from "@testing-library/user-event";
-import * as React from "react";
-import "@testing-library/jest-dom";
-import { SquigglePlayground } from "../src/index";
-
-test("Autorun is default", async () => {
-  render(<SquigglePlayground code="70*30" />);
-  await waitFor(() =>
-    expect(screen.getByTestId("playground-result")).toHaveTextContent("2100")
-  );
-});
-
-test("Autorun can be switched off", async () => {
-  const user = userEvent.setup();
-  render(<SquigglePlayground code="70*30" />);
-
-  expect(screen.getByTestId("autorun-controls")).toHaveTextContent("Autorun");
-
-  await waitFor(() =>
-    expect(screen.getByTestId("playground-result")).toHaveTextContent("2100")
-  );
-
-  await user.click(screen.getByText("Autorun")); // disable
-  expect(screen.getByTestId("autorun-controls")).toHaveTextContent("Paused");
-  expect(screen.getByTestId("autorun-controls")).not.toHaveTextContent(
-    "Autorun"
-  );
-
-  await user.click(screen.getByText("Paused")); // enable autorun again
-  expect(screen.getByTestId("autorun-controls")).toHaveTextContent("Autorun");
-
-  // we should replace the code here, but it's hard to update react-ace state via user events: https://github.com/securingsincity/react-ace/issues/923
-  // ...or replace react-ace with something else
-
-  // TODO:
-
-  /*
-  const editor = screen
-    .getByTestId("squiggle-editor")
-    .querySelector(".ace_editor") as HTMLElement;
-  editor.focus();
-  //   await user.clear(editor);
-  await userEvent.paste("40*40"); // https://github.com/securingsincity/react-ace/issues/923#issuecomment-755502696
-  screen.debug(editor);
-
-  // this makes the tests slower, but it's hard to test otherwise that the code _didn't_ execute
-  await new Promise((r) => setTimeout(r, 300));
-  expect(screen.getByTestId("playground-result")).toHaveTextContent("2100"); // still the old value
-
-  await waitFor(() =>
-    expect(screen.getByTestId("playground-result")).toHaveTextContent("1600")
-  );
-*/
-});
--- a/packages/components/test/basic.test.tsx
+++ b/packages/components/test/basic.test.tsx
@ -1,53 +0,0 @@
-import { render, screen } from "@testing-library/react";
-import React from "react";
-import "@testing-library/jest-dom";
-import {
-  SquiggleChart,
-  SquiggleEditor,
-  SquigglePlayground,
-} from "../src/index";
-import { SqProject } from "@quri/squiggle-lang";
-
-test("Chart logs nothing on render", async () => {
-  const { unmount } = render(<SquiggleChart code={"normal(0, 1)"} />);
-  unmount();
-
-  expect(console.log).not.toBeCalled();
-  expect(console.warn).not.toBeCalled();
-  expect(console.error).not.toBeCalled();
-});
-
-test("Editor logs nothing on render", async () => {
-  const { unmount } = render(<SquiggleEditor code={"normal(0, 1)"} />);
-  unmount();
-
-  expect(console.log).not.toBeCalled();
-  expect(console.warn).not.toBeCalled();
-  expect(console.error).not.toBeCalled();
-});
-
-test("Project dependencies work in editors", async () => {
-  const project = SqProject.create();
-
-  render(<SquiggleEditor code={"x = 1"} project={project} />);
-  const source = project.getSourceIds()[0];
-  const { container } = render(
-    <SquiggleEditor code={"x + 1"} project={project} continues={[source]} />
-  );
-  expect(container).toHaveTextContent("2");
-});
-
-test("Project dependencies work in playgrounds", async () => {
-  const project = SqProject.create();
-  project.setSource("depend", "x = 1");
-
-  render(
-    <SquigglePlayground
-      code={"x + 1"}
-      project={project}
-      continues={["depend"]}
-    />
-  );
-  // We must await here because SquigglePlayground loads results asynchronously
-  expect(await screen.findByRole("status")).toHaveTextContent("2");
-});
--- a/packages/components/test/cleanup.test.tsx
+++ b/packages/components/test/cleanup.test.tsx
@ -1,39 +0,0 @@
-import { render } from "@testing-library/react";
-import React from "react";
-import "@testing-library/jest-dom";
-import { SquiggleChart } from "../src/index";
-import { SqProject } from "@quri/squiggle-lang";
-
-test("Creates and cleans up source", async () => {
-  const project = SqProject.create();
-
-  const { unmount } = render(
-    <SquiggleChart code={"normal(0, 1)"} project={project} />
-  );
-
-  expect(project.getSourceIds().length).toBe(1);
-
-  const sourceId = project.getSourceIds()[0];
-  expect(project.getSource(sourceId)).toBe("normal(0, 1)");
-
-  unmount();
-  expect(project.getSourceIds().length).toBe(0);
-  expect(project.getSource(sourceId)).toBe(undefined);
-});
-
-test("Creates and cleans up source and imports", async () => {
-  const project = SqProject.create();
-
-  const { unmount } = render(
-    <SquiggleChart
-      code={"normal($x, 1)"}
-      project={project}
-      jsImports={{ x: 3 }}
-    />
-  );
-
-  expect(project.getSourceIds().length).toBe(2);
-
-  unmount();
-  expect(project.getSourceIds()).toStrictEqual([]);
-});
--- a/packages/components/test/setup.js
+++ b/packages/components/test/setup.js
@ -1,8 +0,0 @@
-global.console = {
-  ...console,
-  log: jest.fn(console.log),
-  debug: jest.fn(console.debug),
-  info: jest.fn(console.info),
-  warn: jest.fn(console.warn),
-  error: jest.fn(console.error),
-};
--- a/packages/components/vercel.json
+++ b/packages/components/vercel.json
@ -1,4 +1,5 @@
 {
-  "buildCommand": "cd ../.. && npx turbo run build --filter=@quri/squiggle-components",
-  "outputDirectory": "storybook-static"
+  "buildCommand": "cd ../squiggle-lang && yarn build && cd ../components && yarn build",
+  "outputDirectory": "storybook-static",
+  "installCommand": "cd ../../ && yarn"
 }
--- a/packages/squiggle-lang/.prettierignore
+++ b/packages/squiggle-lang/.prettierignore
@ -3,8 +3,6 @@ lib
 *.bs.js
 *.gen.tsx
 .nyc_output/
-coverage/
+_coverage/
 .cache/
 Reducer_Peggy_GeneratedParser.js
-ReducerProject_IncludeParser.js
-src/rescript/Reducer/Reducer_Peggy/helpers.js
--- a/packages/squiggle-lang/tests/Distributions/Dotwise_test.res
+++ b/packages/squiggle-lang/tests/Distributions/Dotwise_test.res
@ -32,10 +32,7 @@ describe("dotSubtract", () => {
 */
  Skip.test("mean of normal minus exponential (property)", () => {
    assert_(
-      property2(
-        float_(),
-        floatRange(1e-5, 1e5),
-        (mean, rate) => {
+      property2(float_(), floatRange(1e-5, 1e5), (mean, rate) => {
        // We limit ourselves to stdev=1 so that the integral is trivial
        let dotDifference = DistributionOperation.Constructors.pointwiseSubtract(
          ~env,
@ -53,8 +50,7 @@ describe("dotSubtract", () => {
        | Ok(meanValue) => abs_float(meanValue -. meanAnalytical) /. abs_float(meanValue) < 1e-2 // 1% relative error
        | Error(err) => err === DistributionTypes.OperationError(DivisionByZeroError)
        }
-        },
-      ),
+      }),
    )
    pass
  })
--- a/packages/squiggle-lang/tests/Distributions/Invariants/AlgebraicCombination_test.res
+++ b/packages/squiggle-lang/tests/Distributions/Invariants/AlgebraicCombination_test.res
@ -40,9 +40,7 @@ let algebraicPower = algebraicPower(~env)

 describe("(Algebraic) addition of distributions", () => {
  describe("mean", () => {
-    test(
-      "normal(mean=5) + normal(mean=20)",
-      () => {
+    test("normal(mean=5) + normal(mean=20)", () => {
      normalDist5
      ->algebraicAdd(normalDist20)
      ->E.R2.fmap(DistributionTypes.Constructors.UsingDists.mean)
@ -51,12 +49,9 @@ describe("(Algebraic) addition of distributions", () => {
      ->E.R.toExn("Expected float", _)
      ->expect
      ->toBe(Some(2.5e1))
-      },
-    )
+    })

-    test(
-      "uniform(low=9, high=10) + beta(alpha=2, beta=5)",
-      () => {
+    test("uniform(low=9, high=10) + beta(alpha=2, beta=5)", () => {
      // let uniformMean = (9.0 +. 10.0) /. 2.0
      // let betaMean = 1.0 /. (1.0 +. 5.0 /. 2.0)
      let received =
@ -72,11 +67,8 @@ describe("(Algebraic) addition of distributions", () => {
      // sometimes it works with ~digits=2.
      | Some(x) => x->expect->toBeSoCloseTo(9.786831807237022, ~digits=1) // (uniformMean +. betaMean)
      }
-      },
-    )
-    test(
-      "beta(alpha=2, beta=5) + uniform(low=9, high=10)",
-      () => {
+    })
+    test("beta(alpha=2, beta=5) + uniform(low=9, high=10)", () => {
      // let uniformMean = (9.0 +. 10.0) /. 2.0
      // let betaMean = 1.0 /. (1.0 +. 5.0 /. 2.0)
      let received =
@ -92,8 +84,7 @@ describe("(Algebraic) addition of distributions", () => {
      // sometimes it works with ~digits=2.
      | Some(x) => x->expect->toBeSoCloseTo(9.784290207736126, ~digits=1) // (uniformMean +. betaMean)
      }
-      },
-    )
+    })
  })
  describe("pdf", () => {
    // TEST IS WRONG. SEE STDEV ADDITION EXPRESSION.
@ -131,9 +122,7 @@ describe("(Algebraic) addition of distributions", () => {
        }
      },
    )
-    test(
-      "(normal(mean=10) + normal(mean=10)).pdf(1.9e1)",
-      () => {
+    test("(normal(mean=10) + normal(mean=10)).pdf(1.9e1)", () => {
      let received =
        normalDist20
        ->Ok
@ -161,11 +150,8 @@ describe("(Algebraic) addition of distributions", () => {
        | Some(y) => x->expect->toBeSoCloseTo(y, ~digits=1)
        }
      }
-      },
-    )
-    test(
-      "(uniform(low=9, high=10) + beta(alpha=2, beta=5)).pdf(10)",
-      () => {
+    })
+    test("(uniform(low=9, high=10) + beta(alpha=2, beta=5)).pdf(10)", () => {
      let received =
        uniformDist
        ->algebraicAdd(betaDist)
@ -180,11 +166,8 @@ describe("(Algebraic) addition of distributions", () => {
      // This value was calculated by a python script
      | Some(x) => x->expect->toBeSoCloseTo(0.979023, ~digits=0)
      }
-      },
-    )
-    test(
-      "(beta(alpha=2, beta=5) + uniform(low=9, high=10)).pdf(10)",
-      () => {
+    })
+    test("(beta(alpha=2, beta=5) + uniform(low=9, high=10)).pdf(10)", () => {
      let received =
        betaDist
        ->algebraicAdd(uniformDist)
@ -197,14 +180,10 @@ describe("(Algebraic) addition of distributions", () => {
      // This is nondeterministic.
      | Some(x) => x->expect->toBeSoCloseTo(0.979023, ~digits=0)
      }
-      },
-    )
+    })
  })
  describe("cdf", () => {
-    testAll(
-      "(normal(mean=5) + normal(mean=5)).cdf (imprecise)",
-      list{6e0, 8e0, 1e1, 1.2e1},
-      x => {
+    testAll("(normal(mean=5) + normal(mean=5)).cdf (imprecise)", list{6e0, 8e0, 1e1, 1.2e1}, x => {
      let received =
        normalDist10
        ->Ok
@ -233,11 +212,8 @@ describe("(Algebraic) addition of distributions", () => {
        | Some(y) => x->expect->toBeSoCloseTo(y, ~digits=0)
        }
      }
-      },
-    )
-    test(
-      "(normal(mean=10) + normal(mean=10)).cdf(1.25e1)",
-      () => {
+    })
+    test("(normal(mean=10) + normal(mean=10)).cdf(1.25e1)", () => {
      let received =
        normalDist20
        ->Ok
@ -265,11 +241,8 @@ describe("(Algebraic) addition of distributions", () => {
        | Some(y) => x->expect->toBeSoCloseTo(y, ~digits=2)
        }
      }
-      },
-    )
-    test(
-      "(uniform(low=9, high=10) + beta(alpha=2, beta=5)).cdf(10)",
-      () => {
+    })
+    test("(uniform(low=9, high=10) + beta(alpha=2, beta=5)).cdf(10)", () => {
      let received =
        uniformDist
        ->algebraicAdd(betaDist)
@ -283,11 +256,8 @@ describe("(Algebraic) addition of distributions", () => {
      // The value was calculated externally using a python script
      | Some(x) => x->expect->toBeSoCloseTo(0.71148, ~digits=1)
      }
-      },
-    )
-    test(
-      "(beta(alpha=2, beta=5) + uniform(low=9, high=10)).cdf(10)",
-      () => {
+    })
+    test("(beta(alpha=2, beta=5) + uniform(low=9, high=10)).cdf(10)", () => {
      let received =
        betaDist
        ->algebraicAdd(uniformDist)
@ -301,15 +271,11 @@ describe("(Algebraic) addition of distributions", () => {
      // The value was calculated externally using a python script
      | Some(x) => x->expect->toBeSoCloseTo(0.71148, ~digits=1)
      }
-      },
-    )
+    })
  })

  describe("inv", () => {
-    testAll(
-      "(normal(mean=5) + normal(mean=5)).inv (imprecise)",
-      list{5e-2, 4.2e-3, 9e-3},
-      x => {
+    testAll("(normal(mean=5) + normal(mean=5)).inv (imprecise)", list{5e-2, 4.2e-3, 9e-3}, x => {
      let received =
        normalDist10
        ->Ok
@ -338,11 +304,8 @@ describe("(Algebraic) addition of distributions", () => {
        | Some(y) => x->expect->toBeSoCloseTo(y, ~digits=-1)
        }
      }
-      },
-    )
-    test(
-      "(normal(mean=10) + normal(mean=10)).inv(1e-1)",
-      () => {
+    })
+    test("(normal(mean=10) + normal(mean=10)).inv(1e-1)", () => {
      let received =
        normalDist20
        ->Ok
@ -370,11 +333,8 @@ describe("(Algebraic) addition of distributions", () => {
        | Some(y) => x->expect->toBeSoCloseTo(y, ~digits=-1)
        }
      }
-      },
-    )
-    test(
-      "(uniform(low=9, high=10) + beta(alpha=2, beta=5)).inv(2e-2)",
-      () => {
+    })
+    test("(uniform(low=9, high=10) + beta(alpha=2, beta=5)).inv(2e-2)", () => {
      let received =
        uniformDist
        ->algebraicAdd(betaDist)
@ -388,11 +348,8 @@ describe("(Algebraic) addition of distributions", () => {
      // sometimes it works with ~digits=2.
      | Some(x) => x->expect->toBeSoCloseTo(9.179319623146968, ~digits=0)
      }
-      },
-    )
-    test(
-      "(beta(alpha=2, beta=5) + uniform(low=9, high=10)).inv(2e-2)",
-      () => {
+    })
+    test("(beta(alpha=2, beta=5) + uniform(low=9, high=10)).inv(2e-2)", () => {
      let received =
        betaDist
        ->algebraicAdd(uniformDist)
@ -406,7 +363,6 @@ describe("(Algebraic) addition of distributions", () => {
      // sometimes it works with ~digits=2.
      | Some(x) => x->expect->toBeSoCloseTo(9.190872365862756, ~digits=0)
      }
-      },
-    )
+    })
  })
 })
--- a/packages/squiggle-lang/tests/Distributions/Invariants/Means_test.res
+++ b/packages/squiggle-lang/tests/Distributions/Invariants/Means_test.res
@ -87,22 +87,14 @@ describe("Means are invariant", () => {
    let testAddInvariant = (t1, t2) =>
      E.R.liftM2(testAdditionMean, t1, t2)->E.R.toExn("Means were not invariant", _)

-    testAll(
-      "with two of the same distribution",
-      distributions,
-      dist => {
+    testAll("with two of the same distribution", distributions, dist => {
      testAddInvariant(dist, dist)
-      },
-    )
+    })

-    testAll(
-      "with two different distributions",
-      pairsOfDifferentDistributions,
-      dists => {
+    testAll("with two different distributions", pairsOfDifferentDistributions, dists => {
      let (dist1, dist2) = dists
      testAddInvariant(dist1, dist2)
-      },
-    )
+    })

    testAll(
      "with two different distributions in swapped order",
@ -124,22 +116,14 @@ describe("Means are invariant", () => {
    let testSubtractInvariant = (t1, t2) =>
      E.R.liftM2(testSubtractionMean, t1, t2)->E.R.toExn("Means were not invariant", _)

-    testAll(
-      "with two of the same distribution",
-      distributions,
-      dist => {
+    testAll("with two of the same distribution", distributions, dist => {
      testSubtractInvariant(dist, dist)
-      },
-    )
+    })

-    testAll(
-      "with two different distributions",
-      pairsOfDifferentDistributions,
-      dists => {
+    testAll("with two different distributions", pairsOfDifferentDistributions, dists => {
      let (dist1, dist2) = dists
      testSubtractInvariant(dist1, dist2)
-      },
-    )
+    })

    testAll(
      "with two different distributions in swapped order",
@ -161,22 +145,14 @@ describe("Means are invariant", () => {
    let testMultiplicationInvariant = (t1, t2) =>
      E.R.liftM2(testMultiplicationMean, t1, t2)->E.R.toExn("Means were not invariant", _)

-    testAll(
-      "with two of the same distribution",
-      distributions,
-      dist => {
+    testAll("with two of the same distribution", distributions, dist => {
      testMultiplicationInvariant(dist, dist)
-      },
-    )
+    })

-    testAll(
-      "with two different distributions",
-      pairsOfDifferentDistributions,
-      dists => {
+    testAll("with two different distributions", pairsOfDifferentDistributions, dists => {
      let (dist1, dist2) = dists
      testMultiplicationInvariant(dist1, dist2)
-      },
-    )
+    })

    testAll(
      "with two different distributions in swapped order",
--- a/packages/squiggle-lang/tests/Distributions/Scoring/KlDivergence_test.res
+++ b/packages/squiggle-lang/tests/Distributions/Scoring/KlDivergence_test.res
@ -17,9 +17,10 @@ describe("klDivergence: continuous -> continuous -> float", () => {
      let answer =
        uniformMakeR(lowAnswer, highAnswer)->E.R2.errMap(s => DistributionTypes.ArgumentError(s))
      let prediction =
-        uniformMakeR(lowPrediction, highPrediction)->E.R2.errMap(
-          s => DistributionTypes.ArgumentError(s),
-        )
+        uniformMakeR(
+          lowPrediction,
+          highPrediction,
+        )->E.R2.errMap(s => DistributionTypes.ArgumentError(s))
      // integral along the support of the answer of answer.pdf(x) times log of prediction.pdf(x) divided by answer.pdf(x) dx
      let analyticalKl = Js.Math.log((highPrediction -. lowPrediction) /. (highAnswer -. lowAnswer))
      let kl = E.R.liftJoin2(klDivergence, prediction, answer)
@ -182,9 +183,9 @@ describe("combineAlongSupportOfSecondArgument0", () => {
    let answer =
      uniformMakeR(lowAnswer, highAnswer)->E.R2.errMap(s => DistributionTypes.ArgumentError(s))
    let prediction =
-      uniformMakeR(lowPrediction, highPrediction)->E.R2.errMap(
-        s => DistributionTypes.ArgumentError(s),
-      )
+      uniformMakeR(lowPrediction, highPrediction)->E.R2.errMap(s => DistributionTypes.ArgumentError(
+        s,
+      ))
    let answerWrapped = E.R.fmap(a => run(FromDist(#ToDist(ToPointSet), a)), answer)
    let predictionWrapped = E.R.fmap(a => run(FromDist(#ToDist(ToPointSet), a)), prediction)

--- a/packages/squiggle-lang/tests/Distributions/Symbolic_test.res
+++ b/packages/squiggle-lang/tests/Distributions/Symbolic_test.res
@ -3,7 +3,7 @@ open Expect
 open TestHelpers

 // TODO: use Normal.make (but preferably after teh new validation dispatch is in)
-let mkNormal = (mean, stdev) => DistributionTypes.Symbolic(#Normal({mean, stdev}))
+let mkNormal = (mean, stdev) => DistributionTypes.Symbolic(#Normal({mean: mean, stdev: stdev}))

 describe("(Symbolic) normalize", () => {
  testAll("has no impact on normal distributions", list{-1e8, -1e-2, 0.0, 1e-4, 1e16}, mean => {
@ -47,7 +47,10 @@ describe("(Symbolic) mean", () => {
    tup => {
      let (low, medium, high) = tup
      let meanValue = run(
-        FromDist(#ToFloat(#Mean), DistributionTypes.Symbolic(#Triangular({low, medium, high}))),
+        FromDist(
+          #ToFloat(#Mean),
+          DistributionTypes.Symbolic(#Triangular({low: low, medium: medium, high: high})),
+        ),
      )
      meanValue->unpackFloat->expect->toBeCloseTo((low +. medium +. high) /. 3.0) // https://www.statology.org/triangular-distribution/
    },
@ -60,7 +63,7 @@ describe("(Symbolic) mean", () => {
    tup => {
      let (alpha, beta) = tup
      let meanValue = run(
-        FromDist(#ToFloat(#Mean), DistributionTypes.Symbolic(#Beta({alpha, beta}))),
+        FromDist(#ToFloat(#Mean), DistributionTypes.Symbolic(#Beta({alpha: alpha, beta: beta}))),
      )
      meanValue->unpackFloat->expect->toBeCloseTo(1.0 /. (1.0 +. beta /. alpha)) // https://en.wikipedia.org/wiki/Beta_distribution#Mean
    },
@ -81,8 +84,8 @@ describe("(Symbolic) mean", () => {
      let (mean, stdev) = tup
      let betaDistribution = SymbolicDist.Beta.fromMeanAndStdev(mean, stdev)
      let meanValue =
-        betaDistribution->E.R2.fmap(
-          d => run(FromDist(#ToFloat(#Mean), d->DistributionTypes.Symbolic)),
+        betaDistribution->E.R2.fmap(d =>
+          run(FromDist(#ToFloat(#Mean), d->DistributionTypes.Symbolic))
        )
      switch meanValue {
      | Ok(value) => value->unpackFloat->expect->toBeCloseTo(mean)
@ -97,7 +100,7 @@ describe("(Symbolic) mean", () => {
    tup => {
      let (mu, sigma) = tup
      let meanValue = run(
-        FromDist(#ToFloat(#Mean), DistributionTypes.Symbolic(#Lognormal({mu, sigma}))),
+        FromDist(#ToFloat(#Mean), DistributionTypes.Symbolic(#Lognormal({mu: mu, sigma: sigma}))),
      )
      meanValue->unpackFloat->expect->toBeCloseTo(Js.Math.exp(mu +. sigma ** 2.0 /. 2.0)) // https://brilliant.org/wiki/log-normal-distribution/
    },
@ -109,7 +112,7 @@ describe("(Symbolic) mean", () => {
    tup => {
      let (low, high) = tup
      let meanValue = run(
-        FromDist(#ToFloat(#Mean), DistributionTypes.Symbolic(#Uniform({low, high}))),
+        FromDist(#ToFloat(#Mean), DistributionTypes.Symbolic(#Uniform({low: low, high: high}))),
      )
      meanValue->unpackFloat->expect->toBeCloseTo((low +. high) /. 2.0) // https://en.wikipedia.org/wiki/Continuous_uniform_distribution#Moments
    },
--- a/packages/squiggle-lang/tests/Reducer/Reducer_Bindings/Reducer_Bindings_test.res
+++ b/packages/squiggle-lang/tests/Reducer/Reducer_Bindings/Reducer_Bindings_test.res
@ -33,18 +33,12 @@ describe("Bindings", () => {
    let value2 = Reducer_T.IEvNumber(5.)
    let extendedBindings = bindings->Bindings.extend->Bindings.set("value", value2)

-    test(
-      "get on extended",
-      () => {
+    test("get on extended", () => {
      expect(extendedBindings->Bindings.get("value")) == Some(value2)
-      },
-    )
+    })

-    test(
-      "get on original",
-      () => {
+    test("get on original", () => {
      expect(bindings->Bindings.get("value")) == Some(value)
-      },
-    )
+    })
  })
 })
--- a/packages/squiggle-lang/tests/Reducer/Reducer_Namespace_test.res
+++ b/packages/squiggle-lang/tests/Reducer/Reducer_Namespace_test.res
@ -40,23 +40,14 @@ describe("Namespace", () => {

    let nsMerged = Namespace.mergeMany([ns, ns1, ns2])

-    test(
-      "merge many 1",
-      () => {
+    test("merge many 1", () => {
      expect(nsMerged->Namespace.get("x1")) == Some(x1)
-      },
-    )
-    test(
-      "merge many 2",
-      () => {
+    })
+    test("merge many 2", () => {
      expect(nsMerged->Namespace.get("x4")) == Some(x4)
-      },
-    )
-    test(
-      "merge many 3",
-      () => {
+    })
+    test("merge many 3", () => {
      expect(nsMerged->Namespace.get("value")) == Some(value)
-      },
-    )
+    })
  })
 })
--- a/packages/squiggle-lang/tests/Reducer/Reducer_Peggy/Reducer_Peggy_Parse_test.res
+++ b/packages/squiggle-lang/tests/Reducer/Reducer_Peggy/Reducer_Peggy_Parse_test.res
@ -182,7 +182,7 @@ describe("Peggy parse", () => {
      "a.p1 to a.p2",
      "{(:credibleIntervalToDistribution (:$_atIndex_$ :a 'p1') (:$_atIndex_$ :a 'p2'))}",
    ) // lower than post
-    testParse("1 to 2 + 3", "{(:credibleIntervalToDistribution 1 (:add 2 3))}")
+    testParse("1 to 2 + 3", "{(:add (:credibleIntervalToDistribution 1 2) 3)}") // higher than binary operators
    testParse(
      "1->add(2) to 3->add(4) -> add(4)",
      "{(:credibleIntervalToDistribution (:add 1 2) (:add (:add 3 4) 4))}",
@ -197,7 +197,7 @@ describe("Peggy parse", () => {

  describe("lambda", () => {
    testParse("{|x| x}", "{{|:x| :x}}")
-    testParse("f={|x| x}", "{:f = {|:x| :x}}")
+    testParse("f={|x| x}", "{:f = {{|:x| :x}}}")
    testParse("f(x)=x", "{:f = {|:x| {:x}}}") // Function definitions are lambda assignments
    testParse("f(x)=x ? 1 : 0", "{:f = {|:x| {(::$$_ternary_$$ :x 1 0)}}}") // Function definitions are lambda assignments
  })
--- a/packages/squiggle-lang/tests/Reducer/Reducer_Peggy/Reducer_Peggy_TestHelpers.res
+++ b/packages/squiggle-lang/tests/Reducer/Reducer_Peggy/Reducer_Peggy_TestHelpers.res
@ -9,12 +9,12 @@ open Jest
 open Expect

 let expectParseToBe = (expr, answer) =>
-  Parse.parse(expr, "test")->Parse.toStringResult->expect->toBe(answer)
+  Parse.parse(expr)->Parse.toStringResult->expect->toBe(answer)

 let testParse = (expr, answer) => test(expr, () => expectParseToBe(expr, answer))

-let expectExpressionToBe = (expr, answer, ~v="_", ()) => {
-  let rExpr = Parse.parse(expr, "test")->Result.map(ToExpression.fromNode)
+let expectToExpressionToBe = (expr, answer, ~v="_", ()) => {
+  let rExpr = Parse.parse(expr)->Result.map(ToExpression.fromNode)
  let a1 = rExpr->ExpressionT.toStringResultOkless

  if v == "_" {
@ -22,7 +22,6 @@ let expectExpressionToBe = (expr, answer, ~v="_", ()) => {
  } else {
    let a2 =
      rExpr
-      ->E.R2.errMap(e => e->SqError.fromParseError)
      ->Result.flatMap(expr => Expression.BackCompatible.evaluate(expr))
      ->Reducer_Value.toStringResultOkless
    (a1, a2)->expect->toEqual((answer, v))
@ -30,16 +29,16 @@ let expectExpressionToBe = (expr, answer, ~v="_", ()) => {
 }

 let testToExpression = (expr, answer, ~v="_", ()) =>
-  test(expr, () => expectExpressionToBe(expr, answer, ~v, ()))
+  test(expr, () => expectToExpressionToBe(expr, answer, ~v, ()))

 module MyOnly = {
  let testParse = (expr, answer) => Only.test(expr, () => expectParseToBe(expr, answer))
  let testToExpression = (expr, answer, ~v="_", ()) =>
-    Only.test(expr, () => expectExpressionToBe(expr, answer, ~v, ()))
+    Only.test(expr, () => expectToExpressionToBe(expr, answer, ~v, ()))
 }

 module MySkip = {
  let testParse = (expr, answer) => Skip.test(expr, () => expectParseToBe(expr, answer))
  let testToExpression = (expr, answer, ~v="_", ()) =>
-    Skip.test(expr, () => expectExpressionToBe(expr, answer, ~v, ()))
+    Skip.test(expr, () => expectToExpressionToBe(expr, answer, ~v, ()))
 }
--- a/packages/squiggle-lang/tests/Reducer/Reducer_Peggy/Reducer_Peggy_ToExpression_test.res
+++ b/packages/squiggle-lang/tests/Reducer/Reducer_Peggy/Reducer_Peggy_ToExpression_test.res
@ -75,9 +75,7 @@ describe("Peggy to Expression", () => {
    testToExpression("false ? 1 : 0", "false ? (1) : (0)", ~v="0", ())
    testToExpression("true ? 1 : false ? 2 : 0", "true ? (1) : (false ? (2) : (0))", ~v="1", ()) // nested ternary
    testToExpression("false ? 1 : false ? 2 : 0", "false ? (1) : (false ? (2) : (0))", ~v="0", ()) // nested ternary
-    describe(
-      "ternary bindings",
-      () => {
+    describe("ternary bindings", () => {
      testToExpression(
        // expression binding
        "f(a) = a > 5 ? 1 : 0; f(6)",
@ -99,8 +97,7 @@ describe("Peggy to Expression", () => {
        ~v="6",
        (),
      )
-      },
-    )
+    })
  })

  describe("if then else", () => {
@ -138,7 +135,7 @@ describe("Peggy to Expression", () => {

  describe("lambda", () => {
    testToExpression("{|x| x}", "{|x| x}", ~v="lambda(x=>internal code)", ())
-    testToExpression("f={|x| x}", "f = {|x| x}", ())
+    testToExpression("f={|x| x}", "f = {{|x| x}}", ())
    testToExpression("f(x)=x", "f = {|x| {x}}", ()) // Function definitions are lambda assignments
    testToExpression("f(x)=x ? 1 : 0", "f = {|x| {x ? (1) : (0)}}", ())
  })
--- a/packages/squiggle-lang/tests/Reducer/Reducer_TestHelpers.res
+++ b/packages/squiggle-lang/tests/Reducer/Reducer_TestHelpers.res
@ -1,3 +1,4 @@
+module ErrorValue = Reducer_ErrorValue
 module Expression = Reducer_Expression
 module ExpressionT = Reducer_Expression_T

@ -8,7 +9,7 @@ let unwrapRecord = rValue =>
  rValue->Belt.Result.flatMap(value =>
    switch value {
    | Reducer_T.IEvRecord(aRecord) => Ok(aRecord)
-    | _ => SqError.Message.RETodo("TODO: Internal bindings must be returned")->Error
+    | _ => ErrorValue.RETodo("TODO: Internal bindings must be returned")->Error
    }
  )

@ -22,7 +23,7 @@ let expectEvalError = (code: string) =>
  Expression.BackCompatible.evaluateString(code)
  ->Reducer_Value.toStringResult
  ->expect
-  ->toMatch("Error\\(")
+  ->toMatch("Error\(")

 let testParseToBe = (expr, answer) => test(expr, () => expectParseToBe(expr, answer))
 let testDescriptionParseToBe = (desc, expr, answer) =>
--- a/packages/squiggle-lang/tests/Reducer/Reducer_test.res
+++ b/packages/squiggle-lang/tests/Reducer/Reducer_test.res
@ -37,16 +37,14 @@ describe("eval", () => {
    test("index", () => expectEvalToBe("r = {a: 1}; r.a", "Ok(1)"))
    test("index", () => expectEvalToBe("r = {a: 1}; r.b", "Error(Record property not found: b)"))
    testEvalError("{a: 1}.b") // invalid syntax
-    test(
-      "always the same property ending",
-      () =>
+    test("always the same property ending", () =>
      expectEvalToBe(
        `{
      a: 1, 
      b: 2,
    }`,
        "Ok({a: 1,b: 2})",
-        ),
+      )
    )
  })

@ -72,7 +70,7 @@ describe("test exceptions", () => {
  testDescriptionEvalToBe(
    "javascript exception",
    "javascriptraise('div by 0')",
-    "Error(JS Exception: Error: 'div by 0')",
+    "Error(Error: 'div by 0')",
  )
  // testDescriptionEvalToBe(
  //   "rescript exception",
@ -80,33 +78,3 @@ describe("test exceptions", () => {
  //   "Error(TODO: unhandled rescript exception)",
  // )
 })
-
-describe("stacktraces", () => {
-  test("nested calls", () => {
-    open Expect
-
-    let error =
-      Expression.BackCompatible.evaluateString(`
-  f(x) = {
-    y = "a"
-    x + y
-  }
-  g = {|x| f(x)}
-  h(x) = g(x)
-  h(5)
-`)
-      ->E.R.getError
-      ->E.O2.toExn("oops")
-      ->SqError.toStringWithStackTrace
-
-    expect(
-      error,
-    )->toBe(`Error: There are function matches for add(), but with different arguments: [add(number, number)]; [add(distribution, number)]; [add(number, distribution)]; [add(distribution, distribution)]; [add(date, duration)]; [add(duration, duration)]
-Stack trace:
-  f at line 4, column 5
-  g at line 6, column 12
-  h at line 7, column 10
-  <top> at line 8, column 3
-`)
-  })
-})
--- a/packages/squiggle-lang/tests/ReducerProject/ReducerProject_includes_test.res
+++ b/packages/squiggle-lang/tests/ReducerProject/ReducerProject_includes_test.res
@ -25,7 +25,7 @@ x=1`,
    let mainIncludes = Project.getIncludes(project, "main")
    switch mainIncludes {
    | Ok(includes) => expect(includes) == ["common"]
-    | Error(error) => fail(error->SqError.toString)
+    | Error(error) => fail(error->Reducer_ErrorValue.errorToString)
    }
  })
  test("past chain", () => {
@ -60,7 +60,7 @@ x=1`,
    let mainIncludes = Project.getIncludes(project, "main")
    switch mainIncludes {
    | Ok(includes) => expect(includes) == ["common", "myModule"]
-    | Error(error) => fail(error->SqError.toString)
+    | Error(error) => fail(error->Reducer_ErrorValue.errorToString)
    }
  })

@ -99,7 +99,7 @@ x=1`,
    let mainIncludes = Project.getIncludes(project, "main")
    switch mainIncludes {
    | Ok(includes) => expect(includes) == ["common", "common2", "myModule"]
-    | Error(error) => fail(error->SqError.toString)
+    | Error(error) => fail(error->Reducer_ErrorValue.errorToString)
    }
  })
  test("direct past chain", () => {
--- a/packages/squiggle-lang/tests/ReducerProject/ReducerProject_test.res
+++ b/packages/squiggle-lang/tests/ReducerProject/ReducerProject_test.res
@ -112,25 +112,6 @@ describe("project2", () => {
  })
 })

-describe("removing sources", () => {
-  let project = Project.createProject()
-  Project.setContinues(project, "main", ["second"])
-  Project.setContinues(project, "second", ["first"])
-  Project.setSource(project, "first", "x=1")
-  Project.setSource(project, "second", "y=2")
-  Project.setSource(project, "main", "y")
-
-  Project.removeSource(project, "main")
-
-  test("project doesn't have source", () => {
-    expect(Project.getSource(project, "main")) == None
-  })
-
-  test("dependents get updated", () => {
-    expect(Project.getDependents(project, "second")) == []
-  })
-})
-
 describe("project with include", () => {
  let project = Project.createProject()
  Project.setContinues(project, "main", ["second"])
--- a/packages/squiggle-lang/tests/ReducerProject/ReducerProject_tutorial_1_test.res
+++ b/packages/squiggle-lang/tests/ReducerProject/ReducerProject_tutorial_1_test.res
@ -11,9 +11,7 @@ describe("ReducerProject Tutorial", () => {
    /*
 Case "Running a single source". 
 */
-    test(
-      "run",
-      () => {
+    test("run", () => {
      /* Let's start with running a single source and getting Result as well as the Bindings 
       First you need to create a project. A project is a collection of sources. 
       Project takes care of the dependencies between the sources, correct compilation and run order. 
@ -53,12 +51,9 @@ Case "Running a single source".
      (result->Reducer_Value.toStringResult, bindings->Reducer_Value.toStringRecord)->expect ==
        ("Ok(3)", "{}")
      /* You've got 3 with empty bindings. */
-      },
-    )
+    })

-    test(
-      "run summary",
-      () => {
+    test("run summary", () => {
      let project = Project.createProject()
      project->Project.setSource("main", "1 + 2")
      project->Project.runAll
@ -69,12 +64,9 @@ Case "Running a single source".
        result->Reducer_Value.toStringResult,
        bindings->Reducer_T.IEvRecord->Reducer_Value.toString,
      )->expect == ("Ok(3)", "{}")
-      },
-    )
+    })

-    test(
-      "run with an environment",
-      () => {
+    test("run with an environment", () => {
      /* Running the source code like above allows you to set a custom environment */
      let project = Project.createProject()

@ -86,19 +78,15 @@ Case "Running a single source".
      let result = project->Project.getResult("main")
      let _bindings = project->Project.getBindings("main")
      result->Reducer_Value.toStringResult->expect == "Ok(3)"
-      },
-    )
+    })

-    test(
-      "shortcut",
-      () => {
+    test("shortcut", () => {
      /* If you are running single source without includes and you don't need a custom environment, you can use the shortcut. */
      /* Examples above was to prepare you for the multi source tutorial. */
      let (result, bindings) = Project.evaluate("1+2")
      (result->Reducer_Value.toStringResult, bindings->Reducer_Value.toStringRecord)->expect ==
        ("Ok(3)", "{}")
-      },
-    )
+    })
  })
 })

--- a/packages/squiggle-lang/tests/ReducerProject/ReducerProject_tutorial_2_multisource_test.res
+++ b/packages/squiggle-lang/tests/ReducerProject/ReducerProject_tutorial_2_multisource_test.res
@ -10,9 +10,7 @@ describe("ReducerProject Tutorial", () => {
  describe("Multi source", () => {
    /*
     Case "Running multiple sources" */
-    test(
-      "Chaining",
-      () => {
+    test("Chaining", () => {
      let project = Project.createProject()
      /* This time let's add 3 sources and chain them together */
      project->Project.setSource("source1", "x=1")
@ -34,12 +32,9 @@ describe("ReducerProject Tutorial", () => {

      (result3->Reducer_Value.toStringResult, bindings3->Reducer_Value.toStringRecord)->expect ==
        ("Ok(())", "{z: 3}")
-      },
-    )
+    })

-    test(
-      "Depending",
-      () => {
+    test("Depending", () => {
      /* Instead of chaining the sources, we could have a dependency tree */
      /* The point here is that any source can depend on multiple sources */
      let project = Project.createProject()
@ -61,12 +56,9 @@ describe("ReducerProject Tutorial", () => {

      (result3->Reducer_Value.toStringResult, bindings3->Reducer_Value.toStringRecord)->expect ==
        ("Ok(())", "{z: 3}")
-      },
-    )
+    })

-    test(
-      "Intro to including",
-      () => {
+    test("Intro to including", () => {
      /* Though it would not be practical for a storybook, 
        let's write the same project above with includes.
        You will see that parsing includes is setting the dependencies the same way as before. */
@ -107,7 +99,6 @@ describe("ReducerProject Tutorial", () => {
         - And the depended source1 and source2 is not already there in the project
         - If you knew the includes before hand there would not be point of the include directive.
         More on those on the next section. */
-      },
-    )
+    })
  })
 })
--- a/packages/squiggle-lang/tests/ReducerProject/ReducerProject_tutorial_3_includes_test.res
+++ b/packages/squiggle-lang/tests/ReducerProject/ReducerProject_tutorial_3_includes_test.res
@ -24,46 +24,35 @@ Here we will finally proceed to a real life scenario. */
    )
    /* We need to parse includes after changing the source */
    project->Project.parseIncludes("main")
-    test(
-      "getDependencies",
-      () => {
+    test("getDependencies", () => {
      /* Parse includes has set the dependencies */
      project->Project.getDependencies("main")->expect == ["common"]
      /* If there were no includes than there would be no dependencies */
      /* However if there was a syntax error at includes then would be no dependencies also */
      /* Therefore looking at dependencies is not the right way to load includes */
      /* getDependencies does not distinguish between setContinues or parseIncludes */
-      },
-    )
-    test(
-      "getIncludes",
-      () => {
+    })
+    test("getIncludes", () => {
      /* Parse includes has set the includes */
      switch project->Project.getIncludes("main") {
      | Ok(includes) => includes->expect == ["common"]
-        | Error(err) => err->SqError.toString->fail
+      | Error(err) => err->Reducer_ErrorValue.errorToString->fail
      }
      /* If the includes cannot be parsed then you get a syntax error.
      Otherwise you get the includes.
      If there is no syntax error then you can load that file and use setSource to add it to the project.
      And so on recursively... */
-      },
-    )
-    test(
-      "getDependents",
-      () => {
+    })
+    test("getDependents", () => {
      /* For any reason, you are able to query what other sources
        include or depend on the current source.
        But you don't need to use this to execute the projects.
        It is provided for completeness of information. */
      project->Project.getDependents("main")->expect == []
      /* Nothing is depending on or including main */
-      },
-    )
+    })

-    describe(
-      "Real Like",
-      () => {
+    describe("Real Like", () => {
      /* Now let's look at recursive and possibly cyclic includes */
      /* There is no function provided to load the include files.
    Because we have no idea if will it be an ordinary function or will it use promises.
@ -96,11 +85,10 @@ Here we will finally proceed to a real life scenario. */
          let rIncludes = project->Project.getIncludes(sourceName)
          switch rIncludes {
          /* Maybe there is an include syntax error */
-            | Error(err) => err->SqError.toString->Js.Exn.raiseError
+          | Error(err) => err->Reducer_ErrorValue.errorToString->Js.Exn.raiseError

          | Ok(includes) =>
-              includes->Belt.Array.forEach(
-                newIncludeName => {
+            includes->Belt.Array.forEach(newIncludeName => {
              /* We have got one of the new includes.
               Let's load it and add it to the project */
              let newSource = loadSource(newIncludeName)
@ -109,8 +97,7 @@ Here we will finally proceed to a real life scenario. */
              /* Of course the new source might have includes too. */
              /* Let's recursively load them */
              project->loadIncludesRecursively(newIncludeName, newVisited)
-                },
-              )
+            })
          }
        }
      }
@ -156,18 +143,12 @@ Here we will finally proceed to a real life scenario. */
      let result = project->Project.getResult("main")
      let bindings = project->Project.getBindings("main")
      /* And see the result and bindings.. */
-        test(
-          "recursive includes",
-          () => {
-            (
-              result->Reducer_Value.toStringResult,
-              bindings->Reducer_Value.toStringRecord,
-            )->expect == ("Ok(6)", "{a: 6,b: 2}")
+      test("recursive includes", () => {
+        (result->Reducer_Value.toStringResult, bindings->Reducer_Value.toStringRecord)->expect ==
+          ("Ok(6)", "{a: 6,b: 2}")
        /* Everything as expected */
-          },
-        )
-      },
-    )
+      })
+    })
  })

  describe("Includes myFile as myVariable", () => {
@ -182,20 +163,14 @@ Here we will finally proceed to a real life scenario. */
    `,
    )
    Project.parseIncludes(project, "main")
-    test(
-      "getDependencies",
-      () => {
+    test("getDependencies", () => {
      Project.getDependencies(project, "main")->expect == ["common"]
-      },
-    )
-    test(
-      "getIncludes",
-      () => {
+    })
+    test("getIncludes", () => {
      switch Project.getIncludes(project, "main") {
      | Ok(includes) => includes->expect == ["common"]
-        | Error(err) => err->SqError.toString->fail
+      | Error(err) => err->Reducer_ErrorValue.errorToString->fail
      }
-      },
-    )
+    })
  })
 })
--- a/packages/squiggle-lang/tests/ReducerProject/ReducerProject_tutorial_5_calling_functions.res
+++ b/packages/squiggle-lang/tests/ReducerProject/ReducerProject_tutorial_5_calling_functions.res
@ -30,9 +30,8 @@ describe("ReducerProject Tutorial", () => {
  })

  test("userResults", () => {
-    let userResultsAsString = Belt.Array.map(
-      userResults,
-      aResult => aResult->Reducer_Value.toStringResult,
+    let userResultsAsString = Belt.Array.map(userResults, aResult =>
+      aResult->Reducer_Value.toStringResult
    )
    userResultsAsString->expect == ["Ok(2)", "Ok(4)", "Ok(6)", "Ok(8)", "Ok(10)"]
  })
--- a/packages/squiggle-lang/tests/SqError_test.res
+++ b/packages/squiggle-lang/tests/SqError_test.res
@ -1,41 +0,0 @@
-open Jest
-open Expect
-
-describe("SqError.Message", () => {
-  test("toString", () =>
-    expect(SqError.Message.REOther("test error")->SqError.Message.toString)->toBe(
-      "Error: test error",
-    )
-  )
-})
-
-describe("SqError", () => {
-  test("fromMessage", () =>
-    expect(SqError.Message.REOther("test error")->SqError.fromMessage->SqError.toString)->toBe(
-      "Error: test error",
-    )
-  )
-
-  test("toStringWithStackTrace with empty stacktrace", () =>
-    expect(
-      SqError.Message.REOther("test error")->SqError.fromMessage->SqError.toStringWithStackTrace,
-    )->toBe("Error: test error")
-  )
-
-  test("toStringWithStackTrace", () => {
-    let frameStack =
-      Reducer_FrameStack.make()
-      ->Reducer_FrameStack.extend("frame1", None)
-      ->Reducer_FrameStack.extend("frame2", None)
-
-    expect(
-      SqError.Message.REOther("test error")
-      ->SqError.fromMessageWithFrameStack(frameStack)
-      ->SqError.toStringWithStackTrace,
-    )->toBe(`Error: test error
-Stack trace:
-  frame2
-  frame1
-`)
-  })
-})
--- a/packages/squiggle-lang/tests/SquiggleLibrary/SquiggleLibrary_FunctionRegistryLibrary_test.res
+++ b/packages/squiggle-lang/tests/SquiggleLibrary/SquiggleLibrary_FunctionRegistryLibrary_test.res
@ -10,8 +10,6 @@ let examples = E.A.to_list(FunctionRegistry_Core.Registry.allExamples(registry))

 describe("FunctionRegistry Library", () => {
  describe("Regular tests", () => {
-    testEvalToBe("List.length([3,5,8])", "Ok(3)")
-    testEvalToBe("List.length([])", "Ok(0)")
    testEvalToBe("List.make(3, 'HI')", "Ok(['HI','HI','HI'])")
    testEvalToBe("make(3, 'HI')", "Error(make is not defined)")
    testEvalToBe("List.upTo(1,3)", "Ok([1,2,3])")
@ -82,10 +80,6 @@ describe("FunctionRegistry Library", () => {
      "SampleSet.toList(SampleSet.mapN([SampleSet.fromList([1,2,3,4,5,6]), SampleSet.fromList([6, 5, 4, 3, 2, 1])], {|x| x[0] > x[1] ? x[0] : x[1]}))",
      "Ok([6,5,4,4,5,6])",
    )
-    testEvalToBe(
-      "SampleSet.fromList([1, 2, 3])",
-      "Error(Error: Too few samples when constructing sample set)",
-    )

    testEvalToBe("Dict.merge({a: 1, b: 2}, {b: 3, c: 4, d: 5})", "Ok({a: 1,b: 3,c: 4,d: 5})")
    testEvalToBe(
@ -99,19 +93,15 @@ describe("FunctionRegistry Library", () => {
  })

  describe("Fn auto-testing", () => {
-    testAll(
-      "tests of validity",
-      examples,
-      r => {
+    testAll("tests of validity", examples, r => {
      expectEvalToBeOk(r)
-      },
-    )
+    })

    testAll(
      "tests of type",
      E.A.to_list(
-        FunctionRegistry_Core.Registry.allExamplesWithFns(registry)->E.A2.filter(
-          ((fn, _)) => E.O.isSome(fn.output),
+        FunctionRegistry_Core.Registry.allExamplesWithFns(registry)->E.A2.filter(((fn, _)) =>
+          E.O.isSome(fn.output)
        ),
      ),
      ((fn, example)) => {
--- a/packages/squiggle-lang/tests/TestHelpers.res
+++ b/packages/squiggle-lang/tests/TestHelpers.res
@ -45,12 +45,12 @@ let toExtDist: option<DistributionTypes.genericDist> => DistributionTypes.generi
 let unpackFloat = x => x->toFloat->toExtFloat
 let unpackDist = y => y->toDist->toExtDist

-let mkNormal = (mean, stdev) => DistributionTypes.Symbolic(#Normal({mean, stdev}))
-let mkBeta = (alpha, beta) => DistributionTypes.Symbolic(#Beta({alpha, beta}))
+let mkNormal = (mean, stdev) => DistributionTypes.Symbolic(#Normal({mean: mean, stdev: stdev}))
+let mkBeta = (alpha, beta) => DistributionTypes.Symbolic(#Beta({alpha: alpha, beta: beta}))
 let mkExponential = rate => DistributionTypes.Symbolic(#Exponential({rate: rate}))
-let mkUniform = (low, high) => DistributionTypes.Symbolic(#Uniform({low, high}))
-let mkCauchy = (local, scale) => DistributionTypes.Symbolic(#Cauchy({local, scale}))
-let mkLognormal = (mu, sigma) => DistributionTypes.Symbolic(#Lognormal({mu, sigma}))
+let mkUniform = (low, high) => DistributionTypes.Symbolic(#Uniform({low: low, high: high}))
+let mkCauchy = (local, scale) => DistributionTypes.Symbolic(#Cauchy({local: local, scale: scale}))
+let mkLognormal = (mu, sigma) => DistributionTypes.Symbolic(#Lognormal({mu: mu, sigma: sigma}))
 let mkDelta = x => DistributionTypes.Symbolic(#Float(x))

 let normalMake = SymbolicDist.Normal.make
--- a/packages/squiggle-lang/bsconfig.json
+++ b/packages/squiggle-lang/bsconfig.json
@ -25,6 +25,7 @@
  ],
  "suffix": ".bs.js",
  "namespace": true,
+  "bs-dependencies": ["bisect_ppx"],
  "bs-dev-dependencies": [
    "@glennsl/rescript-jest",
    "rescript-fast-check",
@ -44,5 +45,8 @@
  "refmt": 3,
  "warnings": {
    "number": "+A-42-48-9-30-4"
-  }
+  },
+  "ppx-flags": [
+    ["../../node_modules/bisect_ppx/ppx", "--exclude-files", ".*_test\\.res$$"]
+  ]
 }
--- a/packages/squiggle-lang/jest.config.js
+++ b/packages/squiggle-lang/jest.config.js
@ -2,6 +2,9 @@
 module.exports = {
  preset: "ts-jest",
  testEnvironment: "node",
+  setupFilesAfterEnv: [
+    "<rootdir>/../../node_modules/bisect_ppx/src/runtime/js/jest.bs.js",
+  ],
  testPathIgnorePatterns: [
    ".*Fixtures.bs.js",
    "/node_modules/",
--- a/packages/squiggle-lang/package.json
+++ b/packages/squiggle-lang/package.json
@ -22,8 +22,10 @@
    "test:rescript": "jest --modulePathIgnorePatterns=__tests__/TS/*",
    "test:watch": "jest --watchAll",
    "test:fnRegistry": "jest __tests__/SquiggleLibrary/SquiggleLibrary_FunctionRegistryLibrary_test.bs.js",
-    "coverage:local": "jest --coverage && echo && echo 'Open ./coverage/lcov-report/index.html to see the detailed report.'",
-    "coverage": "jest --coverage && codecov",
+    "coverage:rescript": "rm -f *.coverage && yarn clean && BISECT_ENABLE=yes yarn build && yarn test:rescript && bisect-ppx-report html",
+    "coverage:ts": "yarn clean && yarn build && nyc --reporter=lcov yarn test:ts",
+    "coverage:rescript:ci": "yarn clean && BISECT_ENABLE=yes yarn build:rescript && yarn test:rescript && bisect-ppx-report send-to Codecov",
+    "coverage:ts:ci": "yarn coverage:ts && codecov",
    "lint:rescript": "./lint.sh",
    "lint:prettier": "prettier --check .",
    "lint": "yarn lint:rescript && yarn lint:prettier",
@ -39,7 +41,7 @@
  ],
  "author": "Quantified Uncertainty Research Institute",
  "dependencies": {
-    "@rescript/std": "^10.0.0",
+    "@rescript/std": "^9.1.4",
    "@stdlib/stats": "^0.0.13",
    "jstat": "^1.9.5",
    "lodash": "^4.17.21",
@ -48,23 +50,27 @@
  },
  "devDependencies": {
    "@glennsl/rescript-jest": "^0.9.2",
+    "@istanbuljs/nyc-config-typescript": "^1.0.2",
    "@types/jest": "^27.5.0",
-    "chalk": "^5.1.0",
+    "babel-plugin-transform-es2015-modules-commonjs": "^6.26.2",
+    "bisect_ppx": "^2.7.1",
+    "chalk": "^5.0.1",
    "codecov": "^3.8.3",
    "fast-check": "^3.1.4",
    "gentype": "^4.5.0",
    "jest": "^27.5.1",
    "moduleserve": "^0.9.1",
+    "nyc": "^15.1.0",
    "peggy": "^2.0.1",
    "prettier": "^2.7.1",
    "reanalyze": "^2.23.0",
-    "rescript": "^10.0.0",
+    "rescript": "^9.1.4",
    "rescript-fast-check": "^1.1.1",
    "rescript-js-map": "^1.1.0",
-    "ts-jest": "^29.0.3",
+    "ts-jest": "^27.1.4",
    "ts-loader": "^9.4.1",
    "ts-node": "^10.9.1",
-    "typescript": "^4.8.4",
+    "typescript": "^4.8.3",
    "webpack": "^5.74.0",
    "webpack-cli": "^4.10.0"
  },
--- a/packages/squiggle-lang/scripts/lib.mjs
+++ b/packages/squiggle-lang/scripts/lib.mjs
@ -36,6 +36,6 @@ export const run = (src, { output, sampleCount } = {}) => {
    "Time:",
    String(time),
    result.tag === "Error" ? red(result.tag) : green(result.tag),
-    result.tag === "Error" ? result.value.toStringWithFrameStack() : ""
+    result.tag === "Error" ? result.value.toString() : ""
  );
 };
--- a/packages/squiggle-lang/scripts/run.mjs
+++ b/packages/squiggle-lang/scripts/run.mjs
@ -1,18 +1,11 @@
 #!/usr/bin/env node
 import { run } from "./lib.mjs";

-import { Command } from "commander";
-
-const program = new Command();
-
-program.arguments("<string>");
-
-const options = program.parse(process.argv);
-
-const src = program.args[0];
+const src = process.argv[2];
 if (!src) {
  throw new Error("Expected src");
 }
+console.log(`Running ${src}`);

 const sampleCount = process.env.SAMPLE_COUNT;

--- a/packages/squiggle-lang/src/js/SqError.ts
+++ b/packages/squiggle-lang/src/js/SqError.ts
@ -1,48 +1,17 @@
-import * as RSError from "../rescript/SqError.gen";
-import * as RSReducerT from "../rescript/Reducer/Reducer_T.gen";
-
-import * as RSFrameStack from "../rescript/Reducer/Reducer_FrameStack.gen";
-
-export { location as SqLocation } from "../rescript/Reducer/Reducer_Peggy/Reducer_Peggy_Parse.gen";
+import * as RSErrorValue from "../rescript/ForTS/ForTS_Reducer_ErrorValue.gen";

 export class SqError {
-  constructor(private _value: RSError.t) {}
+  constructor(private _value: RSErrorValue.reducerErrorValue) {}

  toString() {
-    return RSError.toString(this._value);
+    return RSErrorValue.toString(this._value);
  }

-  toStringWithStackTrace() {
-    return RSError.toStringWithStackTrace(this._value);
+  static createTodoError(v: string) {
+    return new SqError(RSErrorValue.createTodoError(v));
  }

  static createOtherError(v: string) {
-    return new SqError(RSError.createOtherError(v));
-  }
-
-  getTopFrame(): SqFrame | undefined {
-    const frame = RSFrameStack.getTopFrame(RSError.getFrameStack(this._value));
-    return frame ? new SqFrame(frame) : undefined;
-  }
-
-  getFrameArray(): SqFrame[] {
-    const frames = RSError.getFrameArray(this._value);
-    return frames.map((frame) => new SqFrame(frame));
-  }
-
-  location() {
-    return this.getTopFrame()?.location();
-  }
-}
-
-export class SqFrame {
-  constructor(private _value: RSReducerT.frame) {}
-
-  name(): string {
-    return RSFrameStack.Frame.getName(this._value);
-  }
-
-  location() {
-    return RSFrameStack.Frame.getLocation(this._value);
+    return new SqError(RSErrorValue.createOtherError(v));
  }
 }
--- a/packages/squiggle-lang/src/js/SqProject.ts
+++ b/packages/squiggle-lang/src/js/SqProject.ts
@ -1,5 +1,5 @@
 import * as RSProject from "../rescript/ForTS/ForTS_ReducerProject.gen";
-import * as RSError from "../rescript/SqError.gen";
+import { reducerErrorValue } from "../rescript/ForTS/ForTS_Reducer_ErrorValue.gen";
 import { environment } from "../rescript/ForTS/ForTS_Distribution/ForTS_Distribution_Environment.gen";
 import { SqError } from "./SqError";
 import { SqRecord } from "./SqRecord";
@ -22,10 +22,6 @@ export class SqProject {
    return RSProject.setSource(this._value, sourceId, value);
  }

-  removeSource(sourceId: string) {
-    RSProject.removeSource(this._value, sourceId);
-  }
-
  getSource(sourceId: string) {
    return RSProject.getSource(this._value, sourceId);
  }
@ -54,7 +50,7 @@ export class SqProject {
    return resultMap2(
      RSProject.getIncludes(this._value, sourceId),
      (a) => a,
-      (v: RSError.t) => new SqError(v)
+      (v: reducerErrorValue) => new SqError(v)
    );
  }

@ -108,7 +104,7 @@ export class SqProject {
            items: [],
          })
        ),
-      (v: RSError.t) => new SqError(v)
+      (v: reducerErrorValue) => new SqError(v)
    );
  }

--- a/packages/squiggle-lang/src/js/SqValueLocation.ts
+++ b/packages/squiggle-lang/src/js/SqValueLocation.ts
@ -1,3 +1,4 @@
+import { isParenthesisNode } from "mathjs";
 import { SqProject } from "./SqProject";

 type PathItem = string | number;
--- a/packages/squiggle-lang/src/js/index.ts
+++ b/packages/squiggle-lang/src/js/index.ts
@ -13,7 +13,7 @@ export {
  environment,
  defaultEnvironment,
 } from "../rescript/ForTS/ForTS_Distribution/ForTS_Distribution.gen";
-export { SqError, SqFrame, SqLocation } from "./SqError";
+export { SqError } from "./SqError";
 export { SqShape } from "./SqPointSetDist";

 export { resultMap } from "./types";
--- a/packages/squiggle-lang/src/rescript/Distributions/DistributionOperation.res
+++ b/packages/squiggle-lang/src/rescript/Distributions/DistributionOperation.res
@ -141,7 +141,6 @@ let rec run = (~env: env, functionCallInfo: functionCallInfo): outputType => {
        Js.log2("Console log requested: ", dist)
        Dist(dist)
      }
-
    | #ToDist(Normalize) => dist->GenericDist.normalize->Dist
    | #ToScore(LogScore(answer, prior)) =>
      GenericDist.Score.logScore(~estimate=dist, ~answer, ~prior, ~env)
--- a/packages/squiggle-lang/src/rescript/Distributions/GenericDist.res
+++ b/packages/squiggle-lang/src/rescript/Distributions/GenericDist.res
@ -99,7 +99,6 @@ let toFloatOperation = (
        }
      }
    }
-
  | (#Stdev | #Variance | #Mode) as op =>
    switch t {
    | SampleSet(s) =>
@ -130,7 +129,7 @@ let toPointSet = (
    SampleSetDist.toPointSetDist(
      ~samples=r,
      ~samplingInputs={
-        sampleCount,
+        sampleCount: sampleCount,
        outputXYPoints: xyPointLength,
        pointSetDistLength: xyPointLength,
        kernelWidth: None,
@ -428,7 +427,6 @@ module AlgebraicCombination = {
          ~toSampleSetFn,
        )
      }
-
    | (None, AsMonteCarlo) =>
      StrategyCallOnValidatedInputs.monteCarlo(toSampleSetFn, arithmeticOperation, t1, t2)
    | (None, AsSymbolic) =>
@ -445,7 +443,6 @@ module AlgebraicCombination = {
            )}`
          Error(RequestedStrategyInvalidError(errString))
        }
-
      | Some(convOp) => StrategyCallOnValidatedInputs.convolution(toPointSetFn, convOp, t1, t2)
      }
    }
--- a/packages/squiggle-lang/src/rescript/Distributions/PointSetDist/AlgebraicShapeCombination.res
+++ b/packages/squiggle-lang/src/rescript/Distributions/PointSetDist/AlgebraicShapeCombination.res
@ -69,7 +69,7 @@ let toDiscretePointMassesFromTriangulars = (
      ()
    }

-    {n: n - 2, masses, means, variances}
+    {n: n - 2, masses: masses, means: means, variances: variances}
  } else {
    for i in 1 to n - 2 {
      // area of triangle = width * height / 2
@ -91,7 +91,7 @@ let toDiscretePointMassesFromTriangulars = (
      ) |> ignore
      ()
    }
-    {n: n - 2, masses, means, variances}
+    {n: n - 2, masses: masses, means: means, variances: variances}
  }
 }

@ -184,7 +184,7 @@ let toDiscretePointMassesFromDiscrete = (s: PointSetTypes.xyShape): pointMassesW
  let means: array<float> = Belt.Array.makeBy(n, i => xs[i])
  let variances: array<float> = Belt.Array.makeBy(n, _ => 0.0)

-  {n, masses, means, variances}
+  {n: n, masses: masses, means: means, variances: variances}
 }

 type argumentPosition = First | Second
--- a/packages/squiggle-lang/src/rescript/Distributions/PointSetDist/Continuous.res
+++ b/packages/squiggle-lang/src/rescript/Distributions/PointSetDist/Continuous.res
@ -45,16 +45,16 @@ module Analysis = {
 let getShape = (t: t) => t.xyShape
 let interpolation = (t: t) => t.interpolation
 let make = (~interpolation=#Linear, ~integralSumCache=None, ~integralCache=None, xyShape): t => {
-  xyShape,
-  interpolation,
-  integralSumCache,
-  integralCache,
+  xyShape: xyShape,
+  interpolation: interpolation,
+  integralSumCache: integralSumCache,
+  integralCache: integralCache,
 }
 let shapeMap = (fn, {xyShape, interpolation, integralSumCache, integralCache}: t): t => {
  xyShape: fn(xyShape),
-  interpolation,
-  integralSumCache,
-  integralCache,
+  interpolation: interpolation,
+  integralSumCache: integralSumCache,
+  integralCache: integralCache,
 }
 let lastY = (t: t) => t |> getShape |> XYShape.T.lastY
 let oShapeMap = (fn, {xyShape, interpolation, integralSumCache, integralCache}: t): option<
@ -135,10 +135,10 @@ let shapeFn = (fn, t: t) => t |> getShape |> fn

 let updateIntegralSumCache = (integralSumCache, t: t): t => {
  ...t,
-  integralSumCache,
+  integralSumCache: integralSumCache,
 }

-let updateIntegralCache = (integralCache, t: t): t => {...t, integralCache}
+let updateIntegralCache = (integralCache, t: t): t => {...t, integralCache: integralCache}

 let sum = (
  ~integralSumCachesFn: (float, float) => option<float>=(_, _) => None,
--- a/packages/squiggle-lang/src/rescript/Distributions/PointSetDist/Discrete.res
+++ b/packages/squiggle-lang/src/rescript/Distributions/PointSetDist/Discrete.res
@ -4,14 +4,14 @@ open Distributions
 type t = PointSetTypes.discreteShape

 let make = (~integralSumCache=None, ~integralCache=None, xyShape): t => {
-  xyShape,
-  integralSumCache,
-  integralCache,
+  xyShape: xyShape,
+  integralSumCache: integralSumCache,
+  integralCache: integralCache,
 }
 let shapeMap = (fn, {xyShape, integralSumCache, integralCache}: t): t => {
  xyShape: fn(xyShape),
-  integralSumCache,
-  integralCache,
+  integralSumCache: integralSumCache,
+  integralCache: integralCache,
 }
 let getShape = (t: t) => t.xyShape
 let oShapeMap = (fn, {xyShape, integralSumCache, integralCache}: t): option<t> =>
@ -63,12 +63,12 @@ let reduce = (

 let updateIntegralSumCache = (integralSumCache, t: t): t => {
  ...t,
-  integralSumCache,
+  integralSumCache: integralSumCache,
 }

 let updateIntegralCache = (integralCache, t: t): t => {
  ...t,
-  integralCache,
+  integralCache: integralCache,
 }

 /* This multiples all of the data points together and creates a new discrete distribution from the results.
--- a/packages/squiggle-lang/src/rescript/Distributions/PointSetDist/Mixed.res
+++ b/packages/squiggle-lang/src/rescript/Distributions/PointSetDist/Mixed.res
@ -4,10 +4,10 @@ open Distributions

 type t = PointSetTypes.mixedShape
 let make = (~integralSumCache=None, ~integralCache=None, ~continuous, ~discrete): t => {
-  continuous,
-  discrete,
-  integralSumCache,
-  integralCache,
+  continuous: continuous,
+  discrete: discrete,
+  integralSumCache: integralSumCache,
+  integralCache: integralCache,
 }

 let totalLength = (t: t): int => {
@ -35,7 +35,7 @@ let toDiscrete = ({discrete}: t) => Some(discrete)

 let updateIntegralCache = (integralCache, t: t): t => {
  ...t,
-  integralCache,
+  integralCache: integralCache,
 }

 let combinePointwise = (
--- a/packages/squiggle-lang/src/rescript/Distributions/PointSetDist/PointSetTypes.res
+++ b/packages/squiggle-lang/src/rescript/Distributions/PointSetDist/PointSetTypes.res
@ -79,8 +79,8 @@ module MixedPoint = {
  type t = mixedPoint
  let toContinuousValue = (t: t) => t.continuous
  let toDiscreteValue = (t: t) => t.discrete
-  let makeContinuous = (continuous: float): t => {continuous, discrete: 0.0}
-  let makeDiscrete = (discrete: float): t => {continuous: 0.0, discrete}
+  let makeContinuous = (continuous: float): t => {continuous: continuous, discrete: 0.0}
+  let makeDiscrete = (discrete: float): t => {continuous: 0.0, discrete: discrete}

  let fmap = (fn: float => float, t: t) => {
    continuous: fn(t.continuous),
--- a/packages/squiggle-lang/src/rescript/Distributions/SampleSetDist/SampleSetDist.res
+++ b/packages/squiggle-lang/src/rescript/Distributions/SampleSetDist/SampleSetDist.res
@ -4,6 +4,13 @@ module Error = {
  type sampleSetError =
    TooFewSamples | NonNumericInput(string) | OperationError(Operation.operationError)

+  let sampleSetErrorToString = (err: sampleSetError): string =>
+    switch err {
+    | TooFewSamples => "Too few samples when constructing sample set"
+    | NonNumericInput(err) => `Found a non-number in input: ${err}`
+    | OperationError(err) => Operation.Error.toString(err)
+    }
+
  @genType
  type pointsetConversionError = TooFewSamplesForConversionToPointSet

--- a/packages/squiggle-lang/src/rescript/Distributions/SymbolicDist/SymbolicDist.res
+++ b/packages/squiggle-lang/src/rescript/Distributions/SymbolicDist/SymbolicDist.res
@ -7,7 +7,7 @@ module Normal = {
  type t = normal
  let make = (mean: float, stdev: float): result<symbolicDist, string> =>
    stdev > 0.0
-      ? Ok(#Normal({mean, stdev}))
+      ? Ok(#Normal({mean: mean, stdev: stdev}))
      : Error("Standard deviation of normal distribution must be larger than 0")
  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)
@ -15,7 +15,7 @@ module Normal = {
  let from90PercentCI = (low, high) => {
    let mean = E.A.Floats.mean([low, high])
    let stdev = (high -. low) /. (2. *. normal95confidencePoint)
-    #Normal({mean, stdev})
+    #Normal({mean: mean, stdev: stdev})
  }
  let inv = (p, t: t) => Jstat.Normal.inv(p, t.mean, t.stdev)
  let sample = (t: t) => Jstat.Normal.sample(t.mean, t.stdev)
@ -25,12 +25,12 @@ 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, stdev})
+    #Normal({mean: mean, stdev: 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, stdev})
+    #Normal({mean: mean, stdev: stdev})
  }

  // TODO: is this useful here at all? would need the integral as well ...
@ -38,7 +38,7 @@ module Normal = {
    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, stdev})
+    #Normal({mean: mean, stdev: stdev})
  }

  let operate = (operation: Operation.Algebraic.t, n1: t, n2: t) =>
@ -88,7 +88,7 @@ module Cauchy = {
  type t = cauchy
  let make = (local, scale): result<symbolicDist, string> =>
    scale > 0.0
-      ? Ok(#Cauchy({local, scale}))
+      ? Ok(#Cauchy({local: local, scale: scale}))
      : Error("Cauchy distribution scale parameter must larger than 0.")
  let pdf = (x, t: t) => Jstat.Cauchy.pdf(x, t.local, t.scale)
  let cdf = (x, t: t) => Jstat.Cauchy.cdf(x, t.local, t.scale)
@ -102,7 +102,7 @@ module Triangular = {
  type t = triangular
  let make = (low, medium, high): result<symbolicDist, string> =>
    low < medium && medium < high
-      ? Ok(#Triangular({low, medium, high}))
+      ? Ok(#Triangular({low: low, medium: medium, high: high}))
      : Error("Triangular values must be increasing order.")
  let pdf = (x, t: t) => Jstat.Triangular.pdf(x, t.low, t.high, t.medium) // not obvious in jstat docs that high comes before medium?
  let cdf = (x, t: t) => Jstat.Triangular.cdf(x, t.low, t.high, t.medium)
@ -116,7 +116,7 @@ module Beta = {
  type t = beta
  let make = (alpha, beta) =>
    alpha > 0.0 && beta > 0.0
-      ? Ok(#Beta({alpha, beta}))
+      ? Ok(#Beta({alpha: alpha, beta: beta}))
      : Error("Beta distribution parameters must be positive")
  let pdf = (x, t: t) => Jstat.Beta.pdf(x, t.alpha, t.beta)
  let cdf = (x, t: t) => Jstat.Beta.cdf(x, t.alpha, t.beta)
@ -150,7 +150,7 @@ module Lognormal = {
  type t = lognormal
  let make = (mu, sigma) =>
    sigma > 0.0
-      ? Ok(#Lognormal({mu, sigma}))
+      ? Ok(#Lognormal({mu: mu, sigma: sigma}))
      : Error("Lognormal standard deviation must be larger than 0")
  let pdf = (x, t: t) => Jstat.Lognormal.pdf(x, t.mu, t.sigma)
  let cdf = (x, t: t) => Jstat.Lognormal.cdf(x, t.mu, t.sigma)
@ -164,7 +164,7 @@ module Lognormal = {
    let logHigh = Js.Math.log(high)
    let mu = E.A.Floats.mean([logLow, logHigh])
    let sigma = (logHigh -. logLow) /. (2.0 *. normal95confidencePoint)
-    #Lognormal({mu, sigma})
+    #Lognormal({mu: mu, sigma: sigma})
  }
  let fromMeanAndStdev = (mean, stdev) => {
    // https://math.stackexchange.com/questions/2501783/parameters-of-a-lognormal-distribution
@ -174,7 +174,7 @@ module Lognormal = {
      let meanSquared = mean ** 2.
      let mu = 2. *. Js.Math.log(mean) -. 0.5 *. Js.Math.log(variance +. meanSquared)
      let sigma = Js.Math.sqrt(Js.Math.log(variance /. meanSquared +. 1.))
-      Ok(#Lognormal({mu, sigma}))
+      Ok(#Lognormal({mu: mu, sigma: sigma}))
    } else {
      Error("Lognormal standard deviation must be larger than 0")
    }
@ -184,14 +184,14 @@ module Lognormal = {
    // https://wikiless.org/wiki/Log-normal_distribution?lang=en#Multiplication_and_division_of_independent,_log-normal_random_variables
    let mu = l1.mu +. l2.mu
    let sigma = Js.Math.sqrt(l1.sigma ** 2. +. l2.sigma ** 2.)
-    #Lognormal({mu, sigma})
+    #Lognormal({mu: mu, sigma: sigma})
  }
  let divide = (l1, l2) => {
    let mu = l1.mu -. l2.mu
    // We believe the ratiands will have covariance zero.
    // See here https://stats.stackexchange.com/questions/21735/what-are-the-mean-and-variance-of-the-ratio-of-two-lognormal-variables for details
    let sigma = Js.Math.sqrt(l1.sigma ** 2. +. l2.sigma ** 2.)
-    #Lognormal({mu, sigma})
+    #Lognormal({mu: mu, sigma: sigma})
  }
  let operate = (operation: Operation.Algebraic.t, n1: t, n2: t) =>
    switch operation {
@ -220,7 +220,7 @@ module Lognormal = {
 module Uniform = {
  type t = uniform
  let make = (low, high) =>
-    high > low ? Ok(#Uniform({low, high})) : Error("High must be larger than low")
+    high > low ? Ok(#Uniform({low: low, high: high})) : Error("High must be larger than low")

  let pdf = (x, t: t) => Jstat.Uniform.pdf(x, t.low, t.high)
  let cdf = (x, t: t) => Jstat.Uniform.cdf(x, t.low, t.high)
@ -239,7 +239,9 @@ module Uniform = {
 module Logistic = {
  type t = logistic
  let make = (location, scale) =>
-    scale > 0.0 ? Ok(#Logistic({location, scale})) : Error("Scale must be positive")
+    scale > 0.0
+      ? Ok(#Logistic({location: location, scale: scale}))
+      : Error("Scale must be positive")

  let pdf = (x, t: t) => Stdlib.Logistic.pdf(x, t.location, t.scale)
  let cdf = (x, t: t) => Stdlib.Logistic.cdf(x, t.location, t.scale)
@ -283,7 +285,7 @@ module Gamma = {
  let make = (shape: float, scale: float) => {
    if shape > 0. {
      if scale > 0. {
-        Ok(#Gamma({shape, scale}))
+        Ok(#Gamma({shape: shape, scale: scale}))
      } else {
        Error("scale must be larger than 0")
      }
@ -541,6 +543,6 @@ module T = {
    | _ =>
      let xs = interpolateXs(~xSelection, d, sampleCount)
      let ys = xs |> E.A.fmap(x => pdf(x, d))
-      Continuous(Continuous.make(~integralSumCache=Some(1.0), {xs, ys}))
+      Continuous(Continuous.make(~integralSumCache=Some(1.0), {xs: xs, ys: ys}))
    }
 }
--- a/packages/squiggle-lang/src/rescript/FR/FR_Builtin.res
+++ b/packages/squiggle-lang/src/rescript/FR/FR_Builtin.res
@ -5,7 +5,7 @@ let nameSpace = "" // no namespaced versions

 type simpleDefinition = {
  inputs: array<frType>,
-  fn: array<Reducer_T.value> => result<Reducer_T.value, errorMessage>,
+  fn: array<Reducer_T.value> => result<Reducer_T.value, errorValue>,
 }

 let makeFnMany = (name: string, definitions: array<simpleDefinition>) =>
@ -22,8 +22,8 @@ let makeFnMany = (name: string, definitions: array<simpleDefinition>) =>
 let makeFn = (
  name: string,
  inputs: array<frType>,
-  fn: array<Reducer_T.value> => result<Reducer_T.value, errorMessage>,
-) => makeFnMany(name, [{inputs, fn}])
+  fn: array<Reducer_T.value> => result<Reducer_T.value, errorValue>,
+) => makeFnMany(name, [{inputs: inputs, fn: fn}])

 let library = [
  Make.ff2f(~name="add", ~fn=(x, y) => x +. y, ()), // infix + (see Reducer/Reducer_Peggy/helpers.ts)
@ -62,7 +62,6 @@ let library = [
        let answer = Js.String2.concat(a, b)
        answer->Reducer_T.IEvString->Ok
      }
-
    | _ => Error(impossibleError)
    }
  }),
@ -73,7 +72,6 @@ let library = [
        let _ = Js.Array2.pushMany(a, b)
        a->Reducer_T.IEvArray->Ok
      }
-
    | _ => Error(impossibleError)
    }
  }),
@ -83,7 +81,6 @@ let library = [
        Js.log(value->Reducer_Value.toString)
        value->Ok
      }
-
    | _ => Error(impossibleError)
    }
  }),
@ -93,7 +90,6 @@ let library = [
        Js.log(`${label}: ${value->Reducer_Value.toString}`)
        value->Ok
      }
-
    | _ => Error(impossibleError)
    }
  }),
--- a/packages/squiggle-lang/src/rescript/FR/FR_Danger.res
+++ b/packages/squiggle-lang/src/rescript/FR/FR_Danger.res
@ -67,7 +67,7 @@ module Integration = {
      let applyFunctionAtFloatToFloatOption = (point: float) => {
        // Defined here so that it has access to environment, reducer
        let pointAsInternalExpression = FunctionRegistry_Helpers.Wrappers.evNumber(point)
-        let resultAsInternalExpression = Reducer_Lambda.doLambdaCall(
+        let resultAsInternalExpression = Reducer_Expression_Lambda.doLambdaCall(
          aLambda,
          [pointAsInternalExpression],
          environment,
@ -77,7 +77,7 @@ module Integration = {
        | Reducer_T.IEvNumber(x) => Ok(x)
        | _ =>
          Error(
-            "Error 1 in Danger.integrate. It's possible that your function doesn't return a number, try definining auxiliaryFunction(x) = mean(yourFunction(x)) and integrate auxiliaryFunction instead"->SqError.Message.REOther,
+            "Error 1 in Danger.integrate. It's possible that your function doesn't return a number, try definining auxiliaryFunction(x) = mean(yourFunction(x)) and integrate auxiliaryFunction instead"->Reducer_ErrorValue.REOther,
          )
        }
        result
@ -135,18 +135,16 @@ module Integration = {
              let wrappedResult = result->Reducer_T.IEvNumber->Ok
              wrappedResult
            }
-
          | (Error(b), _) => Error(b)
          | (_, Error(b)) => Error(b)
          }
          resultWithOuterPoints
        }
-
      | Error(b) =>
        ("Integration error 2 in Danger.integrate. It's possible that your function doesn't return a number, try definining auxiliaryFunction(x) = mean(yourFunction(x)) and integrate auxiliaryFunction instead." ++
        "Original error: " ++
-        b->SqError.Message.toString)
-        ->SqError.Message.REOther
+        b->Reducer_ErrorValue.errorToString)
+        ->Reducer_ErrorValue.REOther
        ->Error
      }
      result
@ -171,7 +169,7 @@ module Integration = {
            let result = switch inputs {
            | [_, _, _, IEvNumber(0.0)] =>
              "Integration error 4 in Danger.integrate: Increment can't be 0."
-              ->SqError.Message.REOther
+              ->Reducer_ErrorValue.REOther
              ->Error
            | [
                IEvLambda(aLambda),
@ -189,7 +187,7 @@ module Integration = {
              )
            | _ =>
              Error(
-                SqError.Message.REOther(
+                Reducer_ErrorValue.REOther(
                  "Integration error 5 in Danger.integrate. Remember that inputs are (function, number (min), number (max), number(increment))",
                ),
              )
@ -215,7 +213,7 @@ module Integration = {
            let result = switch inputs {
            | [_, _, _, IEvNumber(0.0)] =>
              "Integration error in Danger.integrate: Increment can't be 0."
-              ->SqError.Message.REOther
+              ->Reducer_ErrorValue.REOther
              ->Error
            | [IEvLambda(aLambda), IEvNumber(min), IEvNumber(max), IEvNumber(epsilon)] =>
              Helpers.integrateFunctionBetweenWithNumIntegrationPoints(
@ -227,11 +225,11 @@ module Integration = {
                reducer,
              )->E.R2.errMap(b =>
                ("Integration error 7 in Danger.integrate. Something went wrong along the way: " ++
-                b->SqError.Message.toString)->SqError.Message.REOther
+                b->Reducer_ErrorValue.errorToString)->Reducer_ErrorValue.REOther
              )
            | _ =>
              "Integration error 8 in Danger.integrate. Remember that inputs are (function, number (min), number (max), number(increment))"
-              ->SqError.Message.REOther
+              ->Reducer_ErrorValue.REOther
              ->Error
            }
            result
@ -248,7 +246,7 @@ module DiminishingReturns = {
  module Helpers = {
    type diminishingReturnsAccumulatorInner = {
      optimalAllocations: array<float>,
-      currentMarginalReturns: result<array<float>, errorMessage>,
+      currentMarginalReturns: result<array<float>, errorValue>,
    }
    let findBiggestElementIndex = (xs: array<float>) =>
      E.A.reducei(xs, 0, (acc, newElement, index) => {
@ -257,7 +255,7 @@ module DiminishingReturns = {
        | false => acc
        }
      })
-    type diminishingReturnsAccumulator = result<diminishingReturnsAccumulatorInner, errorMessage>
+    type diminishingReturnsAccumulator = result<diminishingReturnsAccumulatorInner, errorValue>
    // TODO: This is so complicated, it probably should be its own file. It might also make sense to have it work in Rescript directly, taking in a function rather than a reducer; then something else can wrap that function in the reducer/lambdas/environment.
    /*
    The key idea for this function is that 
@ -292,25 +290,25 @@ module DiminishingReturns = {
      ) {
      | (false, _, _, _) =>
        Error(
-          "Error in Danger.optimalAllocationGivenDiminishingMarginalReturnsForManyFunctions, number of functions should be greater than 1."->SqError.Message.REOther,
+          "Error in Danger.optimalAllocationGivenDiminishingMarginalReturnsForManyFunctions, number of functions should be greater than 1."->Reducer_ErrorValue.REOther,
        )
      | (_, false, _, _) =>
        Error(
-          "Error in Danger.optimalAllocationGivenDiminishingMarginalReturnsForManyFunctions, funds should be greater than 0."->SqError.Message.REOther,
+          "Error in Danger.optimalAllocationGivenDiminishingMarginalReturnsForManyFunctions, funds should be greater than 0."->Reducer_ErrorValue.REOther,
        )
      | (_, _, false, _) =>
        Error(
-          "Error in Danger.optimalAllocationGivenDiminishingMarginalReturnsForManyFunctions, approximateIncrement should be greater than 0."->SqError.Message.REOther,
+          "Error in Danger.optimalAllocationGivenDiminishingMarginalReturnsForManyFunctions, approximateIncrement should be greater than 0."->Reducer_ErrorValue.REOther,
        )
      | (_, _, _, false) =>
        Error(
-          "Error in Danger.optimalAllocationGivenDiminishingMarginalReturnsForManyFunctions, approximateIncrement should be smaller than funds amount."->SqError.Message.REOther,
+          "Error in Danger.optimalAllocationGivenDiminishingMarginalReturnsForManyFunctions, approximateIncrement should be smaller than funds amount."->Reducer_ErrorValue.REOther,
        )
      | (true, true, true, true) => {
          let applyFunctionAtPoint = (lambda, point: float) => {
            // Defined here so that it has access to environment, reducer
            let pointAsInternalExpression = FunctionRegistry_Helpers.Wrappers.evNumber(point)
-            let resultAsInternalExpression = Reducer_Lambda.doLambdaCall(
+            let resultAsInternalExpression = Reducer_Expression_Lambda.doLambdaCall(
              lambda,
              [pointAsInternalExpression],
              environment,
@ -320,7 +318,7 @@ module DiminishingReturns = {
            | Reducer_T.IEvNumber(x) => Ok(x)
            | _ =>
              Error(
-                "Error 1 in Danger.optimalAllocationGivenDiminishingMarginalReturnsForManyFunctions. It's possible that your function doesn't return a number, try definining auxiliaryFunction(x) = mean(yourFunction(x)) and integrate auxiliaryFunction instead"->SqError.Message.REOther,
+                "Error 1 in Danger.optimalAllocationGivenDiminishingMarginalReturnsForManyFunctions. It's possible that your function doesn't return a number, try definining auxiliaryFunction(x) = mean(yourFunction(x)) and integrate auxiliaryFunction instead"->Reducer_ErrorValue.REOther,
              )
            }
          }
@ -364,7 +362,6 @@ module DiminishingReturns = {
                        result[indexOfBiggestDMR] = value
                        Ok(result)
                      }
-
                    | Error(b) => Error(b)
                    }

@ -374,12 +371,10 @@ module DiminishingReturns = {
                    }
                    Ok(newAcc)
                  }
-
                | Error(b) => Error(b)
                }
                newAccWrapped
              }
-
            | Error(b) => Error(b)
            }
          })
@ -416,7 +411,7 @@ module DiminishingReturns = {
                  | Reducer_T.IEvLambda(lambda) => Ok(lambda)
                  | _ =>
                    "Error in Danger.optimalAllocationGivenDiminishingMarginalReturnsForManyFunctions. A member of the array wasn't a function"
-                    ->SqError.Message.REOther
+                    ->Reducer_ErrorValue.REOther
                    ->Error
                  }
                }, innerlambdas)
@ -432,15 +427,13 @@ module DiminishingReturns = {
                    )
                    result
                  }
-
                | Error(b) => Error(b)
                }
                result
              }
-
            | _ =>
              "Error in Danger.diminishingMarginalReturnsForTwoFunctions"
-              ->SqError.Message.REOther
+              ->Reducer_ErrorValue.REOther
              ->Error
            },
          (),
--- a/packages/squiggle-lang/src/rescript/FR/FR_Date.res
+++ b/packages/squiggle-lang/src/rescript/FR/FR_Date.res
@ -4,7 +4,7 @@ open FunctionRegistry_Helpers
 let makeFn = (
  name: string,
  inputs: array<frType>,
-  fn: array<Reducer_T.value> => result<Reducer_T.value, errorMessage>,
+  fn: array<Reducer_T.value> => result<Reducer_T.value, errorValue>,
 ) =>
  Function.make(
    ~name,
@ -66,7 +66,7 @@ let library = [
    | [IEvNumber(year)] =>
      switch DateTime.Date.makeFromYear(year) {
      | Ok(t) => IEvDate(t)->Ok
-      | Error(e) => SqError.Message.RETodo(e)->Error
+      | Error(e) => Reducer_ErrorValue.RETodo(e)->Error
      }
    | _ => Error(impossibleError)
    }
--- a/packages/squiggle-lang/src/rescript/FR/FR_Dict.res
+++ b/packages/squiggle-lang/src/rescript/FR/FR_Dict.res
@ -17,7 +17,7 @@ module Internals = {
    ->E.A2.fmap(((key, value)) => Wrappers.evArray([IEvString(key), value]))
    ->Wrappers.evArray

-  let fromList = (items: array<Reducer_T.value>): result<Reducer_T.value, errorMessage> =>
+  let fromList = (items: array<Reducer_T.value>): result<Reducer_T.value, errorValue> =>
    items
    ->E.A2.fmap(item => {
      switch (item: Reducer_T.value) {
@ -76,7 +76,7 @@ let library = [
            ->Belt.Array.map(dictValue =>
              switch dictValue {
              | IEvRecord(dict) => dict
-              | _ => impossibleError->SqError.Message.throw
+              | _ => impossibleError->Reducer_ErrorValue.toException
              }
            )
            ->Internals.mergeMany
--- a/packages/squiggle-lang/src/rescript/FR/FR_Dist.res
+++ b/packages/squiggle-lang/src/rescript/FR/FR_Dist.res
@ -16,14 +16,13 @@ module DistributionCreation = {
      r
      ->E.R.bind(Process.DistOrNumberToDist.twoValuesUsingSymbolicDist(~fn, ~values=_, ~env))
      ->E.R2.fmap(Wrappers.evDistribution)
-      ->E.R2.errMap(e => SqError.Message.REOther(e))
+      ->E.R2.errMap(e => Reducer_ErrorValue.REOther(e))

    let make = (name, fn) => {
      FnDefinition.make(
        ~name,
        ~inputs=[FRTypeDistOrNumber, FRTypeDistOrNumber],
-        ~run=(inputs, context, _) =>
-          inputs->Prepare.ToValueTuple.twoDistOrNumber->process(~fn, ~env=context.environment),
+        ~run=(inputs, env, _) => inputs->Prepare.ToValueTuple.twoDistOrNumber->process(~fn, ~env),
        (),
      )
    }
@ -32,10 +31,8 @@ module DistributionCreation = {
      FnDefinition.make(
        ~name,
        ~inputs=[FRTypeRecord([("p5", FRTypeDistOrNumber), ("p95", FRTypeDistOrNumber)])],
-        ~run=(inputs, context, _) =>
-          inputs
-          ->Prepare.ToValueTuple.Record.twoDistOrNumber(("p5", "p95"))
-          ->process(~fn, ~env=context.environment),
+        ~run=(inputs, env, _) =>
+          inputs->Prepare.ToValueTuple.Record.twoDistOrNumber(("p5", "p95"))->process(~fn, ~env),
        (),
      )
    }
@ -44,10 +41,10 @@ module DistributionCreation = {
      FnDefinition.make(
        ~name,
        ~inputs=[FRTypeRecord([("mean", FRTypeDistOrNumber), ("stdev", FRTypeDistOrNumber)])],
-        ~run=(inputs, context, _) =>
+        ~run=(inputs, env, _) =>
          inputs
          ->Prepare.ToValueTuple.Record.twoDistOrNumber(("mean", "stdev"))
-          ->process(~fn, ~env=context.environment),
+          ->process(~fn, ~env),
        (),
      )
    }
@ -58,14 +55,13 @@ module DistributionCreation = {
      r
      ->E.R.bind(Process.DistOrNumberToDist.oneValueUsingSymbolicDist(~fn, ~value=_, ~env))
      ->E.R2.fmap(Wrappers.evDistribution)
-      ->E.R2.errMap(e => SqError.Message.REOther(e))
+      ->E.R2.errMap(e => Reducer_ErrorValue.REOther(e))

    let make = (name, fn) =>
      FnDefinition.make(
        ~name,
        ~inputs=[FRTypeDistOrNumber],
-        ~run=(inputs, context, _) =>
-          inputs->Prepare.ToValueTuple.oneDistOrNumber->process(~fn, ~env=context.environment),
+        ~run=(inputs, env, _) => inputs->Prepare.ToValueTuple.oneDistOrNumber->process(~fn, ~env),
        (),
      )
  }
--- a/packages/squiggle-lang/src/rescript/FR/FR_Fn.res
+++ b/packages/squiggle-lang/src/rescript/FR/FR_Fn.res
@ -20,7 +20,6 @@ module Declaration = {
        ->E.A.R.firstErrorOrOpen
        ->E.R2.fmap(args => Reducer_T.IEvDeclaration(Declaration.make(lambda, args)))
      }
-
    | Error(r) => Error(r)
    | Ok(_) => Error(impossibleErrorString)
    }
--- a/packages/squiggle-lang/src/rescript/FR/FR_GenericDist.res
+++ b/packages/squiggle-lang/src/rescript/FR/FR_GenericDist.res
@ -140,7 +140,6 @@ module Old = {
            | Error(err) => error(err)
            }
          }
-
        | Some(IEvNumber(_))
        | Some(IEvDistribution(_)) =>
          switch parseDistributionArray(args) {
@ -193,7 +192,6 @@ module Old = {
        }
        Helpers.toFloatFn(fn, dist, ~env)
      }
-
    | ("integralSum", [IEvDistribution(dist)]) => Helpers.toFloatFn(#IntegralSum, dist, ~env)
    | ("toString", [IEvDistribution(dist)]) => Helpers.toStringFn(ToString, dist, ~env)
    | ("sparkline", [IEvDistribution(dist)]) =>
@ -298,7 +296,7 @@ module Old = {

  let genericOutputToReducerValue = (o: DistributionOperation.outputType): result<
    Reducer_T.value,
-    SqError.Message.t,
+    Reducer_ErrorValue.errorValue,
  > =>
    switch o {
    | Dist(d) => Ok(Reducer_T.IEvDistribution(d))
@ -313,9 +311,9 @@ module Old = {
    switch dispatchToGenericOutput(call, environment) {
    | Some(o) => genericOutputToReducerValue(o)
    | None =>
-      SqError.Message.REOther(
-        "Internal error in FR_GenericDist implementation",
-      )->SqError.Message.throw
+      Reducer_ErrorValue.REOther("Internal error in FR_GenericDist implementation")
+      ->Reducer_ErrorValue.ErrorException
+      ->raise
    }
 }

@ -328,7 +326,7 @@ let makeProxyFn = (name: string, inputs: array<frType>) => {
      FnDefinition.make(
        ~name,
        ~inputs,
-        ~run=(inputs, context, _) => Old.dispatch((name, inputs), context.environment),
+        ~run=(inputs, env, _) => Old.dispatch((name, inputs), env),
        (),
      ),
    ],
@ -404,9 +402,9 @@ let library = E.A.concatMany([
 ])

 // FIXME - impossible to implement with FR due to arbitrary parameters length;
-let mxLambda = Reducer_Lambda.makeFFILambda("mx", (inputs, context, _) => {
-  switch Old.dispatch(("mx", inputs), context.environment) {
+let mxLambda = Reducer_Expression_Lambda.makeFFILambda((inputs, env, _) => {
+  switch Old.dispatch(("mx", inputs), env) {
  | Ok(value) => value
-  | Error(e) => e->SqError.Message.throw
+  | Error(e) => e->Reducer_ErrorValue.ErrorException->raise
  }
 })
--- a/packages/squiggle-lang/src/rescript/FR/FR_List.res
+++ b/packages/squiggle-lang/src/rescript/FR/FR_List.res
@ -5,10 +5,6 @@ let nameSpace = "List"
 let requiresNamespace = true

 module Internals = {
-  let length = (v: array<Reducer_T.value>): Reducer_T.value => IEvNumber(
-    Belt.Int.toFloat(Array.length(v)),
-  )
-
  let makeFromNumber = (n: float, value: Reducer_T.value): Reducer_T.value => IEvArray(
    Belt.Array.make(E.Float.toInt(n), value),
  )
@ -30,11 +26,11 @@ module Internals = {
  let map = (
    array: array<Reducer_T.value>,
    eLambdaValue,
-    context: Reducer_T.context,
+    env: Reducer_T.environment,
    reducer: Reducer_T.reducerFn,
  ): Reducer_T.value => {
    Belt.Array.map(array, elem =>
-      Reducer_Lambda.doLambdaCall(eLambdaValue, [elem], context, reducer)
+      Reducer_Expression_Lambda.doLambdaCall(eLambdaValue, [elem], env, reducer)
    )->Wrappers.evArray
  }

@ -42,11 +38,11 @@ module Internals = {
    aValueArray,
    initialValue,
    aLambdaValue,
-    context: Reducer_T.context,
+    env: Reducer_T.environment,
    reducer: Reducer_T.reducerFn,
  ) => {
    aValueArray->E.A.reduce(initialValue, (acc, elem) =>
-      Reducer_Lambda.doLambdaCall(aLambdaValue, [acc, elem], context, reducer)
+      Reducer_Expression_Lambda.doLambdaCall(aLambdaValue, [acc, elem], env, reducer)
    )
  }

@ -54,22 +50,22 @@ module Internals = {
    aValueArray,
    initialValue,
    aLambdaValue,
-    context: Reducer_T.context,
+    env: Reducer_T.environment,
    reducer: Reducer_T.reducerFn,
  ) => {
    aValueArray->Belt.Array.reduceReverse(initialValue, (acc, elem) =>
-      Reducer_Lambda.doLambdaCall(aLambdaValue, [acc, elem], context, reducer)
+      Reducer_Expression_Lambda.doLambdaCall(aLambdaValue, [acc, elem], env, reducer)
    )
  }

  let filter = (
    aValueArray,
    aLambdaValue,
-    context: Reducer_T.context,
+    env: Reducer_T.environment,
    reducer: Reducer_T.reducerFn,
  ) => {
    Js.Array2.filter(aValueArray, elem => {
-      let result = Reducer_Lambda.doLambdaCall(aLambdaValue, [elem], context, reducer)
+      let result = Reducer_Expression_Lambda.doLambdaCall(aLambdaValue, [elem], env, reducer)
      switch result {
      | IEvBool(true) => true
      | _ => false
@ -79,26 +75,6 @@ module Internals = {
 }

 let library = [
-  Function.make(
-    ~name="length",
-    ~nameSpace,
-    ~output=EvtNumber,
-    ~requiresNamespace=true,
-    ~examples=[`List.length([1,4,5])`],
-    ~definitions=[
-      FnDefinition.make(
-        ~name="length",
-        ~inputs=[FRTypeArray(FRTypeAny)],
-        ~run=(inputs, _, _) =>
-          switch inputs {
-          | [IEvArray(array)] => Internals.length(array)->Ok
-          | _ => Error(impossibleError)
-          },
-        (),
-      ),
-    ],
-    (),
-  ),
  Function.make(
    ~name="make",
    ~nameSpace,
--- a/packages/squiggle-lang/src/rescript/FR/FR_Pointset.res
+++ b/packages/squiggle-lang/src/rescript/FR/FR_Pointset.res
@ -16,31 +16,30 @@ let inputsToDist = (inputs: array<Reducer_T.value>, xyShapeToPointSetDist) => {
          let yValue = map->Belt.Map.String.get("y")
          switch (xValue, yValue) {
          | (Some(IEvNumber(x)), Some(IEvNumber(y))) => (x, y)
-          | _ => impossibleError->SqError.Message.throw
+          | _ => impossibleError->Reducer_ErrorValue.toException
          }
        }
-
-      | _ => impossibleError->SqError.Message.throw
+      | _ => impossibleError->Reducer_ErrorValue.toException
      }
    )
    ->Ok
    ->E.R.bind(r => r->XYShape.T.makeFromZipped->E.R2.errMap(XYShape.Error.toString))
    ->E.R2.fmap(r => Reducer_T.IEvDistribution(PointSet(r->xyShapeToPointSetDist)))
-  | _ => impossibleError->SqError.Message.throw
+  | _ => impossibleError->Reducer_ErrorValue.toException
  }
 }

 module Internal = {
  type t = PointSetDist.t

-  let toType = (r): result<Reducer_T.value, SqError.Message.t> =>
+  let toType = (r): result<Reducer_T.value, Reducer_ErrorValue.errorValue> =>
    switch r {
    | Ok(r) => Ok(Wrappers.evDistribution(PointSet(r)))
    | Error(err) => Error(REOperationError(err))
    }

  let doLambdaCall = (aLambdaValue, list, env, reducer) =>
-    switch Reducer_Lambda.doLambdaCall(aLambdaValue, list, env, reducer) {
+    switch Reducer_Expression_Lambda.doLambdaCall(aLambdaValue, list, env, reducer) {
    | Reducer_T.IEvNumber(f) => Ok(f)
    | _ => Error(Operation.SampleMapNeedsNtoNFunction)
    }
@ -62,18 +61,18 @@ let library = [
      FnDefinition.make(
        ~name="fromDist",
        ~inputs=[FRTypeDist],
-        ~run=(inputs, context, _) =>
+        ~run=(inputs, env, _) =>
          switch inputs {
          | [IEvDistribution(dist)] =>
            GenericDist.toPointSet(
              dist,
-              ~xyPointLength=context.environment.xyPointLength,
-              ~sampleCount=context.environment.sampleCount,
+              ~xyPointLength=env.xyPointLength,
+              ~sampleCount=env.sampleCount,
              (),
            )
            ->E.R2.fmap(Wrappers.pointSet)
            ->E.R2.fmap(Wrappers.evDistribution)
-            ->E.R2.errMap(e => SqError.Message.REDistributionError(e))
+            ->E.R2.errMap(e => Reducer_ErrorValue.REDistributionError(e))
          | _ => Error(impossibleError)
          },
        (),
--- a/packages/squiggle-lang/src/rescript/FR/FR_Sampleset.res
+++ b/packages/squiggle-lang/src/rescript/FR/FR_Sampleset.res
@ -10,40 +10,41 @@ module Internal = {
  let doLambdaCall = (
    aLambdaValue,
    list,
-    context: Reducer_T.context,
+    env: Reducer_T.environment,
    reducer: Reducer_T.reducerFn,
  ) =>
-    switch Reducer_Lambda.doLambdaCall(aLambdaValue, list, context, reducer) {
+    switch Reducer_Expression_Lambda.doLambdaCall(aLambdaValue, list, env, reducer) {
    | IEvNumber(f) => Ok(f)
    | _ => Error(Operation.SampleMapNeedsNtoNFunction)
    }

-  let toType = (r): result<Reducer_T.value, SqError.Message.t> =>
+  let toType = (r): result<Reducer_T.value, Reducer_ErrorValue.errorValue> =>
    switch r {
    | Ok(r) => Ok(Wrappers.evDistribution(SampleSet(r)))
    | Error(r) => Error(REDistributionError(SampleSetError(r)))
    }

  //TODO: I don't know why this seems to need at least one input
-  let fromFn = (aLambdaValue, context: Reducer_T.context, reducer: Reducer_T.reducerFn) => {
-    let sampleCount = context.environment.sampleCount
-    let fn = r => doLambdaCall(aLambdaValue, [IEvNumber(r)], context, reducer)
+  let fromFn = (aLambdaValue, environment: Reducer_T.environment, reducer: Reducer_T.reducerFn) => {
+    let sampleCount = environment.sampleCount
+    let fn = r => doLambdaCall(aLambdaValue, [IEvNumber(r)], environment, reducer)
    Belt_Array.makeBy(sampleCount, r => fn(r->Js.Int.toFloat))->E.A.R.firstErrorOrOpen
  }

-  let map1 = (sampleSetDist: t, aLambdaValue, context: Reducer_T.context, reducer) => {
-    let fn = r => doLambdaCall(aLambdaValue, [IEvNumber(r)], context, reducer)
+  let map1 = (sampleSetDist: t, aLambdaValue, environment: Reducer_T.environment, reducer) => {
+    let fn = r => doLambdaCall(aLambdaValue, [IEvNumber(r)], environment, reducer)
    SampleSetDist.samplesMap(~fn, sampleSetDist)->toType
  }

-  let map2 = (t1: t, t2: t, aLambdaValue, context: Reducer_T.context, reducer) => {
-    let fn = (a, b) => doLambdaCall(aLambdaValue, [IEvNumber(a), IEvNumber(b)], context, reducer)
+  let map2 = (t1: t, t2: t, aLambdaValue, environment: Reducer_T.environment, reducer) => {
+    let fn = (a, b) =>
+      doLambdaCall(aLambdaValue, [IEvNumber(a), IEvNumber(b)], environment, reducer)
    SampleSetDist.map2(~fn, ~t1, ~t2)->toType
  }

-  let map3 = (t1: t, t2: t, t3: t, aLambdaValue, context: Reducer_T.context, reducer) => {
+  let map3 = (t1: t, t2: t, t3: t, aLambdaValue, environment: Reducer_T.environment, reducer) => {
    let fn = (a, b, c) =>
-      doLambdaCall(aLambdaValue, [IEvNumber(a), IEvNumber(b), IEvNumber(c)], context, reducer)
+      doLambdaCall(aLambdaValue, [IEvNumber(a), IEvNumber(b), IEvNumber(c)], environment, reducer)
    SampleSetDist.map3(~fn, ~t1, ~t2, ~t3)->toType
  }

@ -59,7 +60,7 @@ module Internal = {
  let mapN = (
    aValueArray: array<Reducer_T.value>,
    aLambdaValue,
-    context: Reducer_T.context,
+    environment: Reducer_T.environment,
    reducer,
  ) => {
    switch parseSampleSetArray(aValueArray) {
@ -68,7 +69,7 @@ module Internal = {
        doLambdaCall(
          aLambdaValue,
          [IEvArray(E.A.fmap(x => Wrappers.evNumber(x), a))],
-          context,
+          environment,
          reducer,
        )
      SampleSetDist.mapN(~fn, ~t1)->toType
@ -88,13 +89,13 @@ let libaryBase = [
      FnDefinition.make(
        ~name="fromDist",
        ~inputs=[FRTypeDist],
-        ~run=(inputs, context, _) =>
+        ~run=(inputs, environment, _) =>
          switch inputs {
          | [IEvDistribution(dist)] =>
-            GenericDist.toSampleSetDist(dist, context.environment.sampleCount)
+            GenericDist.toSampleSetDist(dist, environment.sampleCount)
            ->E.R2.fmap(Wrappers.sampleSet)
            ->E.R2.fmap(Wrappers.evDistribution)
-            ->E.R2.errMap(e => SqError.Message.REDistributionError(e))
+            ->E.R2.errMap(e => Reducer_ErrorValue.REDistributionError(e))
          | _ => Error(impossibleError)
          },
        (),
@ -115,7 +116,7 @@ let libaryBase = [
        ~run=(inputs, _, _) => {
          let sampleSet =
            inputs->Prepare.ToTypedArray.numbers
-              |> E.R2.bind(r => SampleSetDist.make(r)->E.R2.errMap(SampleSetDist.Error.toString))
+              |> E.R2.bind(r => SampleSetDist.make(r)->E.R2.errMap(_ => "AM I HERE? WHYERE AMI??"))
          sampleSet
          ->E.R2.fmap(Wrappers.sampleSet)
          ->E.R2.fmap(Wrappers.evDistribution)
@ -162,7 +163,7 @@ let libaryBase = [
          | [IEvLambda(lambda)] =>
            switch Internal.fromFn(lambda, environment, reducer) {
            | Ok(r) => Ok(r->Wrappers.sampleSet->Wrappers.evDistribution)
-            | Error(e) => e->SqError.Message.REOperationError->Error
+            | Error(e) => e->Reducer_ErrorValue.REOperationError->Error
            }
          | _ => Error(impossibleError)
          },
@ -289,7 +290,7 @@ module Comparison = {
    r
    ->E.R2.fmap(r => r->Wrappers.sampleSet->Wrappers.evDistribution)
    ->E.R2.errMap(e =>
-      e->DistributionTypes.Error.sampleErrorToDistErr->SqError.Message.REDistributionError
+      e->DistributionTypes.Error.sampleErrorToDistErr->Reducer_ErrorValue.REDistributionError
    )

  let mkBig = (name, withDist, withFloat) =>
--- a/packages/squiggle-lang/src/rescript/FR/FR_Scoring.res
+++ b/packages/squiggle-lang/src/rescript/FR/FR_Scoring.res
@ -6,7 +6,7 @@ let requiresNamespace = true
 let runScoring = (estimate, answer, prior, env) => {
  GenericDist.Score.logScore(~estimate, ~answer, ~prior, ~env)
  ->E.R2.fmap(FunctionRegistry_Helpers.Wrappers.evNumber)
-  ->E.R2.errMap(e => SqError.Message.REDistributionError(e))
+  ->E.R2.errMap(e => Reducer_ErrorValue.REDistributionError(e))
 }

 let library = [
@ -30,15 +30,15 @@ let library = [
            ("prior", FRTypeDist),
          ]),
        ],
-        ~run=(inputs, context, _) => {
+        ~run=(inputs, environment, _) => {
          switch FunctionRegistry_Helpers.Prepare.ToValueArray.Record.threeArgs(
            inputs,
            ("estimate", "answer", "prior"),
          ) {
          | Ok([IEvDistribution(estimate), IEvDistribution(d), IEvDistribution(prior)]) =>
-            runScoring(estimate, Score_Dist(d), Some(prior), context.environment)
+            runScoring(estimate, Score_Dist(d), Some(prior), environment)
          | Ok([IEvDistribution(estimate), IEvNumber(d), IEvDistribution(prior)]) =>
-            runScoring(estimate, Score_Scalar(d), Some(prior), context.environment)
+            runScoring(estimate, Score_Scalar(d), Some(prior), environment)
          | Error(e) => Error(e->FunctionRegistry_Helpers.wrapError)
          | _ => Error(FunctionRegistry_Helpers.impossibleError)
          }
@ -48,15 +48,15 @@ let library = [
      FnDefinition.make(
        ~name="logScore",
        ~inputs=[FRTypeRecord([("estimate", FRTypeDist), ("answer", FRTypeDistOrNumber)])],
-        ~run=(inputs, context, _) => {
+        ~run=(inputs, environment, _) => {
          switch FunctionRegistry_Helpers.Prepare.ToValueArray.Record.twoArgs(
            inputs,
            ("estimate", "answer"),
          ) {
          | Ok([IEvDistribution(estimate), IEvDistribution(d)]) =>
-            runScoring(estimate, Score_Dist(d), None, context.environment)
+            runScoring(estimate, Score_Dist(d), None, environment)
          | Ok([IEvDistribution(estimate), IEvNumber(d)]) =>
-            runScoring(estimate, Score_Scalar(d), None, context.environment)
+            runScoring(estimate, Score_Scalar(d), None, environment)
          | Error(e) => Error(e->FunctionRegistry_Helpers.wrapError)
          | _ => Error(FunctionRegistry_Helpers.impossibleError)
          }
@ -76,10 +76,10 @@ let library = [
      FnDefinition.make(
        ~name="klDivergence",
        ~inputs=[FRTypeDist, FRTypeDist],
-        ~run=(inputs, context, _) => {
+        ~run=(inputs, environment, _) => {
          switch inputs {
          | [IEvDistribution(estimate), IEvDistribution(d)] =>
-            runScoring(estimate, Score_Dist(d), None, context.environment)
+            runScoring(estimate, Score_Dist(d), None, environment)
          | _ => Error(FunctionRegistry_Helpers.impossibleError)
          }
        },
--- a/packages/squiggle-lang/src/rescript/ForTS/ForTS_ReducerProject.res
+++ b/packages/squiggle-lang/src/rescript/ForTS/ForTS_ReducerProject.res
@ -1,7 +1,6 @@
@genType type reducerProject = ReducerProject_T.project //re-export

-type error = SqError.t //use
-type errorMessage = SqError.Message.t //use
+type reducerErrorValue = ForTS_Reducer_ErrorValue.reducerErrorValue //use

 type squiggleValue = ForTS_SquiggleValue.squiggleValue //use
 type squiggleValue_Record = ForTS_SquiggleValue.squiggleValue_Record //use
@ -51,13 +50,6 @@ Sets the source for a given source Id.
 let setSource = (project: reducerProject, sourceId: string, value: string): unit =>
  project->Private.setSource(sourceId, value)

-/*
-Removes the source for a given source Id.
-*/
-@genType
-let removeSource = (project: reducerProject, sourceId: string): unit =>
-  project->Private.removeSource(sourceId)
-
 /*
 Gets the source for a given source id.
 */
@ -104,8 +96,10 @@ let cleanAllResults = (project: reducerProject): unit => project->Private.cleanA
 To set the includes one first has to call "parseIncludes". The parsed includes or the parser error is returned.
 */
@genType
-let getIncludes = (project: reducerProject, sourceId: string): result<array<string>, error> =>
-  project->Private.getIncludes(sourceId)
+let getIncludes = (project: reducerProject, sourceId: string): result<
+  array<string>,
+  reducerErrorValue,
+> => project->Private.getIncludes(sourceId)

 /* Other sources contributing to the global namespace of this source. */
@genType
@ -197,8 +191,10 @@ let getBindings = (project: reducerProject, sourceId: string): squiggleValue_Rec
 Get the result after running this source file or the project
 */
@genType
-let getResult = (project: reducerProject, sourceId: string): result<squiggleValue, error> =>
-  project->Private.getResult(sourceId)
+let getResult = (project: reducerProject, sourceId: string): result<
+  squiggleValue,
+  reducerErrorValue,
+> => project->Private.getResult(sourceId)

 /*
 This is a convenience function to get the result of a single source without creating a project. 
@ -206,8 +202,10 @@ However, without a project, you cannot handle include directives.
 The source has to be include free
 */
@genType
-let evaluate = (sourceCode: string): (result<squiggleValue, error>, squiggleValue_Record) =>
-  Private.evaluate(sourceCode)
+let evaluate = (sourceCode: string): (
+  result<squiggleValue, reducerErrorValue>,
+  squiggleValue_Record,
+) => Private.evaluate(sourceCode)

@genType
 let setEnvironment = (project: reducerProject, environment: environment): unit =>
@ -215,3 +213,24 @@ let setEnvironment = (project: reducerProject, environment: environment): unit =

@genType
 let getEnvironment = (project: reducerProject): environment => project->Private.getEnvironment
+
+/*
+Foreign function interface is intentionally demolished.
+There is another way to do that: Umur.
+Also there is no more conversion from javascript to squiggle values currently.
+If the conversion to the new project is too difficult, I can add it later.
+*/
+
+// let foreignFunctionInterface = (
+//   lambdaValue: squiggleValue_Lambda,
+//   argArray: array<squiggleValue>,
+//   environment: environment,
+// ): result<squiggleValue, reducerErrorValue> => {
+//   let accessors = ReducerProject_ProjectAccessors_T.identityAccessorsWithEnvironment(environment)
+//   Reducer_Expression_Lambda.foreignFunctionInterface(
+//     lambdaValue,
+//     argArray,
+//     accessors,
+//     Reducer_Expression.reduceExpressionInProject,
+//   )
+// }
--- a/packages/squiggle-lang/src/rescript/ForTS/ForTS_Reducer_ErrorValue.res
+++ b/packages/squiggle-lang/src/rescript/ForTS/ForTS_Reducer_ErrorValue.res
@ -0,0 +1,18 @@
+@genType type reducerErrorValue = Reducer_ErrorValue.errorValue //alias
+@genType type syntaxErrorLocation = Reducer_ErrorValue.syntaxErrorLocation //alias
+
+@genType
+let toString = (e: reducerErrorValue): string => Reducer_ErrorValue.errorToString(e)
+
+@genType
+let getLocation = (e: reducerErrorValue): option<syntaxErrorLocation> =>
+  switch e {
+  | RESyntaxError(_, optionalLocation) => optionalLocation
+  | _ => None
+  }
+
+@genType
+let createTodoError = (v: string) => Reducer_ErrorValue.RETodo(v)
+
+@genType
+let createOtherError = (v: string) => Reducer_ErrorValue.REOther(v)
--- a/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue.res
+++ b/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue.res
@ -1,5 +1,5 @@
@genType type squiggleValue = Reducer_T.value //re-export
-type error = SqError.t //use
+type reducerErrorValue = ForTS_Reducer_ErrorValue.reducerErrorValue //use

@genType type squiggleValue_Array = Reducer_T.arrayValue //re-export recursive type
@genType type squiggleValue_Record = Reducer_T.map //re-export recursive type
@ -69,7 +69,7 @@ let toString = (variant: squiggleValue) => Reducer_Value.toString(variant)
 // This is a useful method for unit tests.
 // Convert the result along with the error message to a string.
@genType
-let toStringResult = (variantResult: result<squiggleValue, error>) =>
+let toStringResult = (variantResult: result<squiggleValue, reducerErrorValue>) =>
  Reducer_Value.toStringResult(variantResult)

@genType
--- a/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue_Lambda.res
+++ b/packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue_Lambda.res
@ -1,7 +1,9 @@
@genType type squiggleValue_Lambda = Reducer_T.lambdaValue //re-export

@genType
-let toString = (v: squiggleValue_Lambda): string => Reducer_Value.toStringLambda(v)
+let toString = (v: squiggleValue_Lambda): string => Reducer_Value.toStringFunction(v)

@genType
-let parameters = (v: squiggleValue_Lambda): array<string> => Reducer_Lambda.parameters(v)
+let parameters = (v: squiggleValue_Lambda): array<string> => {
+  v.parameters
+}
--- a/packages/squiggle-lang/src/rescript/ForTS/ForTS__Types.res
+++ b/packages/squiggle-lang/src/rescript/ForTS/ForTS__Types.res
@ -1,3 +1,6 @@
+@genType type reducerErrorValue = ForTS_Reducer_ErrorValue.reducerErrorValue //re-export
+@genType type syntaxErrorLocation = ForTS_Reducer_ErrorValue.syntaxErrorLocation //re-export
+
@genType type reducerProject = ForTS_ReducerProject.reducerProject //re-export
@genType type squiggleValue = ForTS_SquiggleValue.squiggleValue //re-export
@genType type squiggleValue_Array = ForTS_SquiggleValue_Array.squiggleValue_Array //re-export
--- a/packages/squiggle-lang/src/rescript/FunctionRegistry/FunctionRegistry_Core.res
+++ b/packages/squiggle-lang/src/rescript/FunctionRegistry/FunctionRegistry_Core.res
@ -1,5 +1,5 @@
 type internalExpressionValueType = Reducer_Value.internalExpressionValueType
-type errorMessage = SqError.Message.t
+type errorValue = Reducer_ErrorValue.errorValue

 /*
  Function Registry "Type". A type, without any other information.
@ -30,9 +30,9 @@ type fnDefinition = {
  inputs: array<frType>,
  run: (
    array<Reducer_T.value>,
-    Reducer_T.context,
+    Reducer_T.environment,
    Reducer_T.reducerFn,
-  ) => result<Reducer_T.value, errorMessage>,
+  ) => result<Reducer_T.value, errorValue>,
 }

 type function = {
@ -61,7 +61,6 @@ module FRType = {
        let input = ((name, frType): frTypeRecordParam) => `${name}: ${toString(frType)}`
        `{${r->E.A2.fmap(input)->E.A2.joinWith(", ")}}`
      }
-
    | FRTypeArray(r) => `list(${toString(r)})`
    | FRTypeLambda => `lambda`
    | FRTypeString => `string`
@ -123,19 +122,19 @@ module FnDefinition = {
  let run = (
    t: t,
    args: array<Reducer_T.value>,
-    context: Reducer_T.context,
+    env: Reducer_T.environment,
    reducer: Reducer_T.reducerFn,
  ) => {
    switch t->isMatch(args) {
-    | true => t.run(args, context, reducer)
+    | true => t.run(args, env, reducer)
    | false => REOther("Incorrect Types")->Error
    }
  }

  let make = (~name, ~inputs, ~run, ()): t => {
-    name,
-    inputs,
-    run,
+    name: name,
+    inputs: inputs,
+    run: run,
  }
 }

@ -161,14 +160,14 @@ module Function = {
    ~isExperimental=false,
    (),
  ): t => {
-    name,
-    nameSpace,
-    definitions,
-    output,
-    examples: examples->E.O2.default([]),
-    isExperimental,
-    requiresNamespace,
-    description,
+    name: name,
+    nameSpace: nameSpace,
+    definitions: definitions,
+    output: output,
+    examples: examples |> E.O.default([]),
+    isExperimental: isExperimental,
+    requiresNamespace: requiresNamespace,
+    description: description,
  }

  let toJson = (t: t): functionJson => {
@ -204,19 +203,15 @@ module Registry = {
            fn.requiresNamespace ? [] : [def.name],
          ]->E.A.concatMany

-        names->Belt.Array.reduce(
-          acc,
-          (acc, name) => {
+        names->Belt.Array.reduce(acc, (acc, name) => {
          switch acc->Belt.Map.String.get(name) {
          | Some(fns) => {
              let _ = fns->Js.Array2.push(def) // mutates the array, no need to update acc
              acc
            }
-
          | None => acc->Belt.Map.String.set(name, [def])
          }
-          },
-        )
+        })
      })
    )
  }
@ -230,9 +225,9 @@ module Registry = {
    registry,
    fnName: string,
    args: array<Reducer_T.value>,
-    context: Reducer_T.context,
+    env: Reducer_T.environment,
    reducer: Reducer_T.reducerFn,
-  ): result<Reducer_T.value, errorMessage> => {
+  ): result<Reducer_T.value, errorValue> => {
    switch Belt.Map.String.get(registry.fnNameDict, fnName) {
    | Some(definitions) => {
        let showNameMatchDefinitions = () => {
@ -246,11 +241,10 @@ module Registry = {

        let match = definitions->Js.Array2.find(def => def->FnDefinition.isMatch(args))
        switch match {
-        | Some(def) => def->FnDefinition.run(args, context, reducer)
+        | Some(def) => def->FnDefinition.run(args, env, reducer)
        | None => REOther(showNameMatchDefinitions())->Error
        }
      }
-
    | None => RESymbolNotFound(fnName)->Error
    }
  }
--- a/packages/squiggle-lang/src/rescript/FunctionRegistry/FunctionRegistry_Helpers.res
+++ b/packages/squiggle-lang/src/rescript/FunctionRegistry/FunctionRegistry_Helpers.res
@ -2,8 +2,8 @@ open FunctionRegistry_Core
 open Reducer_T

 let impossibleErrorString = "Wrong inputs / Logically impossible"
-let impossibleError: errorMessage = impossibleErrorString->SqError.Message.REOther
-let wrapError = e => SqError.Message.REOther(e)
+let impossibleError: errorValue = impossibleErrorString->Reducer_ErrorValue.REOther
+let wrapError = e => Reducer_ErrorValue.REOther(e)

 module Wrappers = {
  let symbolic = r => DistributionTypes.Symbolic(r)
@ -34,7 +34,6 @@ module Prepare = {
            let n2 = map->Belt.Map.String.getExn(arg2)
            Ok([n1, n2])
          }
-
        | _ => Error(impossibleErrorString)
        }

@ -46,7 +45,6 @@ module Prepare = {
            let n3 = map->Belt.Map.String.getExn(arg3)
            Ok([n1, n2, n3])
          }
-
        | _ => Error(impossibleErrorString)
        }
    }
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Bindings.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Bindings.res
@ -44,4 +44,4 @@ let removeResult = ({namespace} as bindings: t): t => {

 let locals = ({namespace}: t): Reducer_T.namespace => namespace

-let fromNamespace = (namespace: Reducer_Namespace.t): t => {namespace, parent: None}
+let fromNamespace = (namespace: Reducer_Namespace.t): t => {namespace: namespace, parent: None}
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Context.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Context.res
@ -4,13 +4,9 @@ let defaultEnvironment: Reducer_T.environment = DistributionOperation.defaultEnv

 let createContext = (stdLib: Reducer_Namespace.t, environment: Reducer_T.environment): t => {
  {
-    frameStack: list{},
    bindings: stdLib->Reducer_Bindings.fromNamespace->Reducer_Bindings.extend,
-    environment,
-    inFunction: None,
+    environment: environment,
  }
 }

-let currentFunctionName = (t: t): string => {
-  t.inFunction->E.O2.fmap(Reducer_Lambda_T.name)->E.O2.default(Reducer_T.topFrameName)
-}
+let createDefaultContext = (): t => createContext(SquiggleLibrary_StdLib.stdLib, defaultEnvironment)
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Dispatch/Reducer_Dispatch_ChainPiece.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Dispatch/Reducer_Dispatch_ChainPiece.res
@ -0,0 +1,27 @@
+// types are disabled until review and rewrite for 0.5 interpreter compatibility
+/*
+module ProjectAccessorsT = ReducerProject_ProjectAccessors_T
+module T = Reducer_Dispatch_T
+module TypeChecker = Reducer_Type_TypeChecker
+open Reducer_Value
+
+type errorValue = Reducer_ErrorValue.errorValue
+
+let makeFromTypes = jumpTable => {
+  let dispatchChainPiece: T.dispatchChainPiece = (
+    (fnName, fnArgs): functionCall,
+    accessors: ProjectAccessorsT.t,
+  ) => {
+    let jumpTableEntry = jumpTable->Js.Array2.find(elem => {
+      let (candidName, candidType, _) = elem
+      candidName == fnName && TypeChecker.checkITypeArgumentsBool(candidType, fnArgs)
+    })
+    switch jumpTableEntry {
+    | Some((_, _, bridgeFn)) => bridgeFn(fnArgs, accessors)->Some
+    | _ => None
+    }
+  }
+  dispatchChainPiece
+}
+
+*/
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Dispatch/Reducer_Dispatch_T.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Dispatch/Reducer_Dispatch_T.res
@ -0,0 +1,21 @@
+// module ExpressionT = Reducer_Expression_T
+// module ProjectAccessorsT = ReducerProject_ProjectAccessors_T
+
+// // Each piece of the dispatch chain computes the result or returns None so that the chain can continue
+// type dispatchChainPiece = (
+//   Reducer_Value.functionCall,
+//   ProjectAccessorsT.t,
+// ) => option<result<Reducer_T.value, Reducer_ErrorValue.errorValue>>
+
+// type dispatchChainPieceWithReducer = (
+//   Reducer_Value.functionCall,
+//   ProjectAccessorsT.t,
+//   Reducer_T.reducerFn,
+// ) => option<result<Reducer_T.value, Reducer_ErrorValue.errorValue>>
+
+// // This is a switch statement case implementation: get the arguments and compute the result
+// type genericIEvFunction = (
+//   array<Reducer_T.value>,
+//   ProjectAccessorsT.t,
+// ) => result<Reducer_T.value, Reducer_ErrorValue.errorValue>
+
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_ErrorValue.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_ErrorValue.res
@ -0,0 +1,83 @@
+//TODO: Do not export here but in ForTS__Types
+@gentype.import("peggy") @genType.as("LocationRange")
+type syntaxErrorLocation
+
+@genType.opaque
+type errorValue =
+  | REArityError(option<string>, int, int)
+  | REArrayIndexNotFound(string, int)
+  | REAssignmentExpected
+  | REDistributionError(DistributionTypes.error)
+  | REExpectedType(string, string)
+  | REExpressionExpected
+  | REFunctionExpected(string)
+  | REFunctionNotFound(string)
+  | REJavaScriptExn(option<string>, option<string>) // Javascript Exception
+  | REMacroNotFound(string)
+  | RENotAFunction(string)
+  | REOperationError(Operation.operationError)
+  | RERecordPropertyNotFound(string, string)
+  | RESymbolNotFound(string)
+  | RESyntaxError(string, option<syntaxErrorLocation>)
+  | RETodo(string) // To do
+  | REUnitNotFound(string)
+  | RENeedToRun
+  | REOther(string)
+
+type t = errorValue
+
+exception ErrorException(errorValue)
+
+let errorToString = err =>
+  switch err {
+  | REArityError(_oFnName, arity, usedArity) =>
+    `${Js.String.make(arity)} arguments expected. Instead ${Js.String.make(
+        usedArity,
+      )} argument(s) were passed.`
+  | REArrayIndexNotFound(msg, index) => `${msg}: ${Js.String.make(index)}`
+  | REAssignmentExpected => "Assignment expected"
+  | REExpressionExpected => "Expression expected"
+  | REFunctionExpected(msg) => `Function expected: ${msg}`
+  | REFunctionNotFound(msg) => `Function not found: ${msg}`
+  | REDistributionError(err) => `Distribution Math Error: ${DistributionTypes.Error.toString(err)}`
+  | REOperationError(err) => `Math Error: ${Operation.Error.toString(err)}`
+  | REJavaScriptExn(omsg, oname) => {
+      let answer = "JS Exception:"
+      let answer = switch oname {
+      | Some(name) => `${answer} ${name}`
+      | _ => answer
+      }
+      let answer = switch omsg {
+      | Some(msg) => `${answer}: ${msg}`
+      | _ => answer
+      }
+      answer
+    }
+  | REMacroNotFound(macro) => `Macro not found: ${macro}`
+  | RENotAFunction(valueString) => `${valueString} is not a function`
+  | RERecordPropertyNotFound(msg, index) => `${msg}: ${index}`
+  | RESymbolNotFound(symbolName) => `${symbolName} is not defined`
+  | RESyntaxError(desc, _) => `Syntax Error: ${desc}`
+  | RETodo(msg) => `TODO: ${msg}`
+  | REExpectedType(typeName, valueString) => `Expected type: ${typeName} but got: ${valueString}`
+  | REUnitNotFound(unitName) => `Unit not found: ${unitName}`
+  | RENeedToRun => "Need to run"
+  | REOther(msg) => `Error: ${msg}`
+  }
+
+let fromException = exn =>
+  switch exn {
+  | ErrorException(e) => e
+  | Js.Exn.Error(e) =>
+    switch Js.Exn.message(e) {
+    | Some(message) => REOther(message)
+    | None =>
+      switch Js.Exn.name(e) {
+      | Some(name) => REOther(name)
+      | None => REOther("Unknown error")
+      }
+    }
+  | _e => REOther("Unknown error")
+  }
+
+let toException = (errorValue: t) => raise(ErrorException(errorValue))
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Exception.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Exception.res
@ -0,0 +1,3 @@
+// There are switch statement cases in the code which are impossible to reach by design.
+// ImpossibleException is a sign of programming error.
+exception ImpossibleException(string)
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression.res
@ -1,25 +1,16 @@
 module Bindings = Reducer_Bindings
+module Lambda = Reducer_Expression_Lambda
 module Result = Belt.Result
 module T = Reducer_T

-let toLocation = (expression: T.expression): Reducer_Peggy_Parse.location => {
-  expression.ast.location
-}
-
-let throwFrom = (error: SqError.Message.t, expression: T.expression, context: T.context) =>
-  error->SqError.throwMessageWithFrameStack(
-    context.frameStack->Reducer_FrameStack.extend(
-      context->Reducer_Context.currentFunctionName,
-      Some(expression->toLocation),
-    ),
-  )
+type errorValue = Reducer_ErrorValue.errorValue

 /*
  Recursively evaluate the expression
 */
 let rec evaluate: T.reducerFn = (expression, context): (T.value, T.context) => {
  // Js.log(`reduce: ${expression->Reducer_Expression_T.toString}`)
-  switch expression.content {
+  switch expression {
  | T.EBlock(statements) => {
      let innerContext = {...context, bindings: context.bindings->Bindings.extend}
      let (value, _) =
@ -58,7 +49,7 @@ let rec evaluate: T.reducerFn = (expression, context): (T.value, T.context) => {
          let (key, _) = eKey->evaluate(context)
          let keyString = switch key {
          | IEvString(s) => s
-          | _ => REOther("Record keys must be strings")->throwFrom(expression, context)
+          | _ => REOther("Record keys must be strings")->Reducer_ErrorValue.ErrorException->raise
          }
          let (value, _) = eValue->evaluate(context)
          (keyString, value)
@ -82,7 +73,7 @@ let rec evaluate: T.reducerFn = (expression, context): (T.value, T.context) => {
  | T.ESymbol(name) =>
    switch context.bindings->Bindings.get(name) {
    | Some(v) => (v, context)
-    | None => RESymbolNotFound(name)->throwFrom(expression, context)
+    | None => Reducer_ErrorValue.RESymbolNotFound(name)->Reducer_ErrorValue.ErrorException->raise
    }

  | T.EValue(value) => (value, context)
@ -91,40 +82,28 @@ let rec evaluate: T.reducerFn = (expression, context): (T.value, T.context) => {
      let (predicateResult, _) = predicate->evaluate(context)
      switch predicateResult {
      | T.IEvBool(value) => (value ? trueCase : falseCase)->evaluate(context)
-      | _ => REExpectedType("Boolean", "")->throwFrom(expression, context)
+      | _ => REExpectedType("Boolean", "")->Reducer_ErrorValue.ErrorException->raise
      }
    }

-  | T.ELambda(parameters, body, name) => (
-      Reducer_Lambda.makeLambda(
-        name,
-        parameters,
-        context.bindings,
-        body,
-        expression->toLocation,
-      )->T.IEvLambda,
+  | T.ELambda(parameters, body) => (
+      Lambda.makeLambda(parameters, context.bindings, body)->T.IEvLambda,
      context,
    )

  | T.ECall(fn, args) => {
      let (lambda, _) = fn->evaluate(context)
-      let argValues = Belt.Array.map(args, arg => {
+      let argValues = Js.Array2.map(args, arg => {
        let (argValue, _) = arg->evaluate(context)
        argValue
      })
      switch lambda {
-      | T.IEvLambda(lambda) => {
-          let result = Reducer_Lambda.doLambdaCallFrom(
-            lambda,
-            argValues,
+      | T.IEvLambda(lambda) => (
+          Lambda.doLambdaCall(lambda, argValues, context.environment, evaluate),
          context,
-            evaluate,
-            Some(expression->toLocation), // we have to pass the location of a current expression here, to put it on frameStack
        )
-          (result, context)
-        }
-
-      | _ => RENotAFunction(lambda->Reducer_Value.toString)->throwFrom(expression, context)
+      | _ =>
+        RENotAFunction(lambda->Reducer_Value.toString)->Reducer_ErrorValue.ErrorException->raise
      }
    }
  }
@ -133,22 +112,19 @@ let rec evaluate: T.reducerFn = (expression, context): (T.value, T.context) => {
 module BackCompatible = {
  // Those methods are used to support the existing tests
  // If they are used outside limited testing context, error location reporting will fail
-  let parse = (peggyCode: string): result<T.expression, Reducer_Peggy_Parse.parseError> =>
-    peggyCode->Reducer_Peggy_Parse.parse("main")->Result.map(Reducer_Peggy_ToExpression.fromNode)
+  let parse = (peggyCode: string): result<T.expression, errorValue> =>
+    peggyCode->Reducer_Peggy_Parse.parse->Result.map(Reducer_Peggy_ToExpression.fromNode)

-  let createDefaultContext = () =>
-    Reducer_Context.createContext(SquiggleLibrary_StdLib.stdLib, Reducer_Context.defaultEnvironment)
-
-  let evaluate = (expression: T.expression): result<T.value, SqError.t> => {
-    let context = createDefaultContext()
+  let evaluate = (expression: T.expression): result<T.value, errorValue> => {
+    let context = Reducer_Context.createDefaultContext()
    try {
      let (value, _) = expression->evaluate(context)
      value->Ok
    } catch {
-    | exn => exn->SqError.fromException->Error
+    | exn => Reducer_ErrorValue.fromException(exn)->Error
    }
  }

-  let evaluateString = (peggyCode: string): result<T.value, SqError.t> =>
-    parse(peggyCode)->E.R2.errMap(e => e->SqError.fromParseError)->Result.flatMap(evaluate)
+  let evaluateString = (peggyCode: string): result<T.value, errorValue> =>
+    parse(peggyCode)->Result.flatMap(evaluate)
 }
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_ExpressionBuilder.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_ExpressionBuilder.res
@ -1,19 +1,16 @@
+module BErrorValue = Reducer_ErrorValue
 module T = Reducer_T

+type errorValue = BErrorValue.errorValue
 type expression = Reducer_T.expression
-type expressionContent = Reducer_T.expressionContent

-let eArray = (anArray: array<T.expression>): expressionContent => anArray->T.EArray
+let eArray = (anArray: array<T.expression>) => anArray->T.EArray

 let eBool = aBool => aBool->T.IEvBool->T.EValue

-let eCall = (fn: expression, args: array<expression>): expressionContent => T.ECall(fn, args)
+let eCall = (fn: expression, args: array<expression>): expression => T.ECall(fn, args)

-let eLambda = (
-  parameters: array<string>,
-  expr: expression,
-  name: option<string>,
-): expressionContent => T.ELambda(parameters, expr, name)
+let eLambda = (parameters: array<string>, expr: expression) => T.ELambda(parameters, expr)

 let eNumber = aNumber => aNumber->T.IEvNumber->T.EValue

@ -21,13 +18,13 @@ let eRecord = (aMap: array<(T.expression, T.expression)>) => aMap->T.ERecord

 let eString = aString => aString->T.IEvString->T.EValue

-let eSymbol = (name: string): expressionContent => T.ESymbol(name)
+let eSymbol = (name: string): expression => T.ESymbol(name)

-let eBlock = (exprs: array<expression>): expressionContent => T.EBlock(exprs)
+let eBlock = (exprs: array<expression>): expression => T.EBlock(exprs)

-let eProgram = (exprs: array<expression>): expressionContent => T.EProgram(exprs)
+let eProgram = (exprs: array<expression>): expression => T.EProgram(exprs)

-let eLetStatement = (symbol: string, valueExpression: expression): expressionContent => T.EAssign(
+let eLetStatement = (symbol: string, valueExpression: expression): expression => T.EAssign(
  symbol,
  valueExpression,
 )
@ -36,8 +33,11 @@ let eTernary = (
  predicate: expression,
  trueCase: expression,
  falseCase: expression,
-): expressionContent => T.ETernary(predicate, trueCase, falseCase)
+): expression => T.ETernary(predicate, trueCase, falseCase)

-let eIdentifier = (name: string): expressionContent => name->T.ESymbol
+let eIdentifier = (name: string): expression => name->T.ESymbol

-let eVoid: expressionContent = T.IEvVoid->T.EValue
+// let eTypeIdentifier = (name: string): expression =>
+//   name->T.IEvTypeIdentifier->T.EValue
+
+let eVoid: expression = T.IEvVoid->T.EValue
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_Lambda.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_Lambda.res
@ -0,0 +1,60 @@
+module ErrorValue = Reducer_ErrorValue
+
+let doLambdaCall = (
+  lambdaValue: Reducer_T.lambdaValue,
+  args,
+  environment: Reducer_T.environment,
+  reducer: Reducer_T.reducerFn,
+): Reducer_T.value => {
+  lambdaValue.body(args, environment, reducer)
+}
+
+let makeLambda = (
+  parameters: array<string>,
+  bindings: Reducer_T.bindings,
+  body: Reducer_T.expression,
+): Reducer_T.lambdaValue => {
+  // TODO - clone bindings to avoid later redefinitions affecting lambdas?
+
+  // Note: with this implementation, FFI lambdas (created by other methods than calling `makeLambda`) are allowed to violate the rules, pollute the bindings, etc.
+  // Not sure yet if that's a bug or a feature.
+  // FunctionRegistry functions are unaffected by this, their API is too limited.
+
+  let lambda = (
+    arguments: array<Reducer_T.value>,
+    environment: Reducer_T.environment,
+    reducer: Reducer_T.reducerFn,
+  ) => {
+    let argsLength = arguments->Js.Array2.length
+    let parametersLength = parameters->Js.Array2.length
+    if argsLength !== parametersLength {
+      ErrorValue.REArityError(None, parametersLength, argsLength)->ErrorValue.ErrorException->raise
+    }
+
+    let localBindings = bindings->Reducer_Bindings.extend
+    let localBindingsWithParameters = parameters->Belt.Array.reduceWithIndex(localBindings, (
+      currentBindings,
+      parameter,
+      index,
+    ) => {
+      currentBindings->Reducer_Bindings.set(parameter, arguments[index])
+    })
+
+    let (value, _) = reducer(
+      body,
+      {bindings: localBindingsWithParameters, environment: environment},
+    )
+    value
+  }
+
+  {
+    // context: bindings,
+    body: lambda,
+    parameters: parameters,
+  }
+}
+
+let makeFFILambda = (body: Reducer_T.lambdaBody): Reducer_T.lambdaValue => {
+  body: body,
+  parameters: ["..."],
+}
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_T.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_T.res
@ -12,7 +12,7 @@ let semicolonJoin = values =>
  Converts the expression to String
 */
 let rec toString = (expression: t) =>
-  switch expression.content {
+  switch expression {
  | EBlock(statements) =>
    `{${Js.Array2.map(statements, aValue => toString(aValue))->semicolonJoin}}`
  | EProgram(statements) => Js.Array2.map(statements, aValue => toString(aValue))->semicolonJoin
@ -24,23 +24,37 @@ let rec toString = (expression: t) =>
    `${predicate->toString} ? (${trueCase->toString}) : (${falseCase->toString})`
  | EAssign(name, value) => `${name} = ${value->toString}`
  | ECall(fn, args) => `(${fn->toString})(${args->Js.Array2.map(toString)->commaJoin})`
-  | ELambda(parameters, body, _) => `{|${parameters->commaJoin}| ${body->toString}}`
+  | ELambda(parameters, body) => `{|${parameters->commaJoin}| ${body->toString}}`
  | EValue(aValue) => Reducer_Value.toString(aValue)
  }

 let toStringResult = codeResult =>
  switch codeResult {
  | Ok(a) => `Ok(${toString(a)})`
-  | Error(m) => `Error(${Reducer_Peggy_Parse.toStringError(m)})`
+  | Error(m) => `Error(${Reducer_ErrorValue.errorToString(m)})`
  }

 let toStringResultOkless = codeResult =>
  switch codeResult {
  | Ok(a) => toString(a)
-  | Error(m) => `Error(${Reducer_Peggy_Parse.toStringError(m)})`
+  | Error(m) => `Error(${Reducer_ErrorValue.errorToString(m)})`
  }

 let inspect = (expr: t): t => {
  Js.log(toString(expr))
  expr
 }
+
+let inspectResult = (r: result<t, Reducer_ErrorValue.errorValue>): result<
+  t,
+  Reducer_ErrorValue.errorValue,
+> => {
+  Js.log(toStringResult(r))
+  r
+}
+
+let resultToValue = (rExpression: result<t, Reducer_ErrorValue.t>): t =>
+  switch rExpression {
+  | Ok(expression) => expression
+  | Error(errorValue) => Reducer_ErrorValue.toException(errorValue)
+  }
--- a/Show More
+++ b/Show More
				`@ -1 +0,0 @@`
				`See the [Changelog.mdx page](./packages/website/docs/Changelog.mdx) for the changelog.`