Merge pull request #1231 from quantified-uncertainty/project-in-editors

Project in editors and remove warnings

.github/CODEOWNERS

@@ -24,7 +24,7 @@
 *.json @quinn-dougherty @Hazelfire @berekuk @OAGr
 *.y*ml @quinn-dougherty @berekuk @OAGr
 *.config.js @Hazelfire @berekuk @OAGr
-netlify.toml @quinn-dougherty @OAGr @berekuk @Hazelfire 
+vercel.json @OAGr @berekuk @Hazelfire
 
 # Documentation
 *.md @quinn-dougherty @OAGr @Hazelfire

.github/workflows/ci.yml

@@ -1,4 +1,4 @@
-name: Squiggle packages check
+name: Squiggle packages checks
 
 on:
   push:
@@ -9,217 +9,40 @@ on:
     branches:
       - master
       - develop
-      - reducer-dev
+
-      - epic-reducer-project
+env:
-      - epic-0.5.0
+  TURBO_TOKEN: ${{ secrets.TURBO_TOKEN }}
+  TURBO_TEAM: quantified-uncertainty
 
 jobs:
-  pre_check:
+  build-test-lint:
-    name: Precheck for skipping redundant jobs
+    name: Build, test, lint
     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@v5.2.0
-        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
-        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
-        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
-        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
-        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: Install Dependencies
+      - name: Setup Node.js environment
-        run: cd ../../ && yarn
+        uses: actions/setup-node@v3
-      - name: Check rescript lint
-        run: yarn lint:rescript
-      - name: Check javascript, typescript, and markdown lint
-        uses: creyD/prettier_action@v4.2
         with:
-          dry: true
+          node-version: 16
-          prettier_options: --check packages/squiggle-lang
+          cache: 'yarn'
+      - name: Install dependencies
+        run: yarn --frozen-lockfile
+      - name: Turbo run
+        run: npx turbo run build test lint bundle
 
-  lang-build-test-bundle:
+  coverage:
-    name: Language build, test, and bundle
+    name: Coverage
     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: Install dependencies from monorepo level
+      - name: Setup Node.js environment
-        run: cd ../../ && yarn
+        uses: actions/setup-node@v2
-      - 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:
-          dry: true
+          node-version: 16
-          prettier_options: --check packages/components --ignore-path packages/components/.prettierignore
+          cache: 'yarn'
-
+      - name: Install dependencies
-  components-bundle-build-test:
+        run: yarn
-    name: Components bundle, build and test
+      - name: Coverage
-    runs-on: ubuntu-latest
+        run: npx turbo run coverage
-    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
-      - name: Test components 
-        run: yarn test
-
-  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

.gitignore

@@ -11,3 +11,5 @@ yarn-error.log
 .vscode
 todo.txt
 result
+shell.nix
+.turbo

CHANGELOG.md

@@ -0,0 +1 @@
+See the [Changelog.mdx page](./packages/website/docs/Changelog.mdx) for the changelog.

CONTRIBUTING.md

@@ -16,7 +16,7 @@ Squiggle is currently pre-alpha.
 
 # Bug reports
 
-Anyone (with a github account) can file an issue at any time. Please allow Quinn, Sam, and Ozzie to triage, but otherwise just follow the suggestions in the issue templates.
+Anyone (with a github account) can file an issue at any time. Please allow Slava, Sam, and Ozzie to triage, but otherwise just follow the suggestions in the issue templates.
 
 # Project structure
 
@@ -28,7 +28,7 @@ Squiggle is a **monorepo** with three **packages**.
 
 # Deployment ops
 
-We use netlify, and it should only concern Quinn, Sam, and Ozzie.
+We use Vercel, and it should only concern Slava, Sam, and Ozzie.
 
 # Development environment, building, testing, dev server
 
@@ -56,9 +56,9 @@ If you absolutely must, please prefix your commit message with `hotfix: `.
 
 Please work against `develop` branch. **Do not** work against `master`.
 
-- For rescript code: Quinn and Ozzie are reviewers
+- For rescript code: Slava and Ozzie are reviewers
 - For js or typescript code: Sam and Ozzie are reviewers
-- For ops code (i.e. yaml, package.json): Quinn and Sam are reviewers
+- For ops code (i.e. yaml, package.json): Slava and Sam are reviewers
 
 Autopings are set up: if you are not autopinged, you are welcome to comment, but please do not use the formal review feature, send approvals, rejections, or merges.
 

README.md

@@ -21,10 +21,10 @@ _An estimation language_.
 
 ## Our deployments
 
-- **website/docs prod**: https://squiggle-language.com [![Netlify Status](https://api.netlify.com/api/v1/badges/2139af5c-671d-473d-a9f6-66c96077d8a1/deploy-status)](https://app.netlify.com/sites/squiggle-documentation/deploys)
+- **website/docs prod**: https://squiggle-language.com
-- **website/docs staging**: https://develop--squiggle-documentation.netlify.app/
+- **website/docs staging**: https://preview.squiggle-language.com
-- **components storybook prod**: https://squiggle-components.netlify.app/ [![Netlify Status](https://api.netlify.com/api/v1/badges/b7f724aa-6b20-4d0e-bf86-3fcd1a3e9a70/deploy-status)](https://app.netlify.com/sites/squiggle-components/deploys)
+- **components storybook prod**: https://components.squiggle-language.com
-- **components storybook staging**: https://develop--squiggle-components.netlify.app/
+- **components storybook staging**: https://preview-components.squiggle-language.com
 - **legacy (2020) playground**: https://playground.squiggle-language.com
 
 ## Packages
@@ -51,7 +51,25 @@ For any project in the repo, begin by running `yarn` in the top level
 yarn
 ```
 
-See `packages/*/README.md` to work with whatever project you're interested in.
+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).
 
 # Contributing
 

nix/squiggle-lang.nix

@@ -30,16 +30,6 @@ 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

nixos.sh

@@ -1,18 +0,0 @@
-#!/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

package.json

@@ -2,12 +2,11 @@
   "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"
+    "prettier": "^2.7.1",
+    "turbo": "^1.5.5"
   },
   "workspaces": [
     "packages/*"

packages/cli/README.md

@@ -20,3 +20,30 @@ 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.

packages/cli/package.json

@@ -7,11 +7,13 @@
   "bin": "index.js",
   "type": "module",
   "scripts": {
-    "start": "node ."
+    "start": "node .",
+    "lint": "prettier --check .",
+    "format": "prettier --write ."
   },
   "license": "MIT",
   "dependencies": {
-    "chalk": "^5.0.1",
+    "chalk": "^5.1.0",
     "chokidar": "^3.5.3",
     "commander": "^9.4.1",
     "fs": "^0.0.1-security",

packages/components/netlify.toml

@@ -1,8 +0,0 @@
-[build]
-    base = "packages/components/"
-    command = "cd ../squiggle-lang && yarn build && cd ../components && yarn build"
-    publish = "storybook-static/"
-    ignore = "node -e 'process.exitCode = process.env.BRANCH.includes(\"dependabot\") ? 0 : 1' && git diff --quiet $CACHED_COMMIT_REF $COMMIT_REF . ../squiggle-lang"
-
-[build.environment]
-    NETLIFY_USE_YARN = "true"

packages/components/package.json

@@ -10,14 +10,16 @@
     "@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": "^7.5.1",
+    "framer-motion": "^7.5.3",
     "lodash": "^4.17.21",
     "react": "^18.1.0",
     "react-ace": "^10.1.0",
-    "react-hook-form": "^7.36.1",
+    "react-hook-form": "^7.37.0",
     "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",
@@ -39,15 +41,16 @@
     "@testing-library/user-event": "^14.4.3",
     "@types/jest": "^27.5.0",
     "@types/lodash": "^4.14.186",
-    "@types/node": "^18.8.0",
+    "@types/node": "^18.8.3",
     "@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": "^29.0.3",
+    "jest-environment-jsdom": "^29.1.2",
-    "jsdom": "^20.0.0",
+    "jsdom": "^20.0.1",
     "mini-css-extract-plugin": "^2.6.1",
     "postcss-cli": "^10.0.0",
     "postcss-import": "^15.0.0",
@@ -57,11 +60,11 @@
     "react-scripts": "^5.0.1",
     "style-loader": "^3.3.1",
     "tailwindcss": "^3.1.8",
-    "ts-jest": "^29.0.2",
+    "ts-jest": "^29.0.3",
     "ts-loader": "^9.4.1",
     "tsconfig-paths-webpack-plugin": "^4.0.0",
     "typescript": "^4.8.4",
-    "web-vitals": "^3.0.2",
+    "web-vitals": "^3.0.3",
     "webpack": "^5.74.0",
     "webpack-cli": "^4.10.0",
     "webpack-dev-server": "^4.11.1"
@@ -82,7 +85,8 @@
     "format": "prettier --write .",
     "prepack": "yarn run build:cjs && yarn run bundle",
     "test": "jest",
-    "test:debug": "node --inspect-brk node_modules/.bin/jest --runInBand"
+    "test:debug": "node --inspect-brk node_modules/.bin/jest --runInBand",
+    "test:profile": "node --cpu-prof node_modules/.bin/jest --runInBand"
   },
   "eslintConfig": {
     "extends": [

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)}>
+    <div className={clsx("rounded-md p-4", backgroundColor)} role="status">
       <div className="flex">
         <Icon
           className={clsx("h-5 w-5 flex-shrink-0", iconColor)}
           aria-hidden="true"
         />
-        <div className="ml-3">
+        <div className="ml-3 grow">
           <header className={clsx("text-sm font-medium", headingColor)}>
             {heading}
           </header>

packages/components/src/components/CodeEditor.tsx

@@ -5,6 +5,8 @@ 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;
@@ -13,15 +15,17 @@ interface CodeEditorProps {
   width?: number;
   height: number;
   showGutter?: boolean;
+  errorLocations?: SqLocation[];
 }
 
 export const CodeEditor: FC<CodeEditorProps> = ({
   value,
   onChange,
   onSubmit,
+  height,
   oneLine = false,
   showGutter = false,
-  height,
+  errorLocations = [],
 }) => {
   const lineCount = value.split("\n").length;
   const id = useMemo(() => _.uniqueId(), []);
@@ -30,8 +34,11 @@ 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"
@@ -48,10 +55,7 @@ export const CodeEditor: FC<CodeEditorProps> = ({
       editorProps={{
         $blockScrolling: true,
       }}
-      setOptions={{
+      setOptions={{}}
-        enableBasicAutocompletion: false,
-        enableLiveAutocompletion: false,
-      }}
       commands={[
         {
           name: "submit",
@@ -59,6 +63,14 @@ 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",
+      }))}
     />
   );
 };

packages/components/src/components/FunctionChart.tsx

@@ -1,9 +1,15 @@
 import * as React from "react";
-import { SqLambda, environment, SqValueTag } from "@quri/squiggle-lang";
+import {
+  SqLambda,
+  environment,
+  SqValueTag,
+  SqError,
+} from "@quri/squiggle-lang";
 import { FunctionChart1Dist } from "./FunctionChart1Dist";
 import { FunctionChart1Number } from "./FunctionChart1Number";
 import { DistributionPlottingSettings } from "./DistributionChart";
-import { ErrorAlert, MessageAlert } from "./Alert";
+import { MessageAlert } from "./Alert";
+import { SquiggleErrorAlert } from "./SquiggleErrorAlert";
 
 export type FunctionChartSettings = {
   start: number;
@@ -19,6 +25,25 @@ 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,
@@ -26,7 +51,8 @@ export const FunctionChart: React.FC<FunctionChartProps> = ({
   distributionPlotSettings,
   height,
 }) => {
-  if (fn.parameters.length > 1) {
+  console.log(fn.parameters().length);
+  if (fn.parameters().length !== 1) {
     return (
       <MessageAlert heading="Function Display Not Supported">
         Only functions with one parameter are displayed.
@@ -47,9 +73,7 @@ export const FunctionChart: React.FC<FunctionChartProps> = ({
   const validResult = getValidResult();
 
   if (validResult.tag === "Error") {
-    return (
+    return <FunctionCallErrorAlert error={validResult.value} />;
-      <ErrorAlert heading="Error">{validResult.value.toString()}</ErrorAlert>
-    );
   }
 
   switch (validResult.value.tag) {

packages/components/src/components/SquiggleChart.tsx

@@ -2,23 +2,21 @@ 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 interface SquiggleChartProps {
+export type 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 */
@@ -26,7 +24,7 @@ export interface SquiggleChartProps {
   /** If the result is a function, the amount of stops sampled */
   diagramCount?: number;
   /** When the squiggle code gets reevaluated */
-  onChange?(expr: SqValue | undefined): void;
+  onChange?(expr: SqValue | undefined, sourceName: string): void;
   /** CSS width of the element */
   width?: number;
   height?: number;
@@ -53,21 +51,30 @@ export interface 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 SquiggleChart: React.FC<SquiggleChartProps> = React.memo(
+export const splitSquiggleChartSettings = (props: SquiggleChartProps) => {
-  ({
+  const {
-    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,
@@ -80,15 +87,7 @@ export const SquiggleChart: React.FC<SquiggleChartProps> = React.memo(
     title,
     xAxisType = "number",
     distributionChartActions,
-    enableLocalSettings = false,
+  } = props;
-  }) => {
-    const { result, bindings } = useSquiggle({
-      code,
-      environment,
-      jsImports,
-      onChange,
-      executionId,
-    });
 
   const distributionPlotSettings = {
     showSummary,
@@ -109,18 +108,49 @@ export const SquiggleChart: React.FC<SquiggleChartProps> = React.memo(
     count: diagramCount,
   };
 
-    const resultToRender = resultMap(result, (value) =>
+  return { distributionPlotSettings, chartSettings };
-      value.tag === SqValueTag.Void ? bindings.asValue() : value
+};
-    );
+
+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);
 
     return (
       <SquiggleViewer
-        result={resultToRender}
+        result={valueToRender}
         width={width}
         height={height}
         distributionPlotSettings={distributionPlotSettings}
         chartSettings={chartSettings}
-        environment={environment ?? defaultEnvironment}
+        environment={
+          project ? project.getEnvironment() : environment ?? defaultEnvironment
+        }
         enableLocalSettings={enableLocalSettings}
       />
     );

packages/components/src/components/SquiggleEditor.tsx

@@ -1,20 +1,29 @@
 import React from "react";
 import { CodeEditor } from "./CodeEditor";
 import { SquiggleContainer } from "./SquiggleContainer";
-import { SquiggleChart, SquiggleChartProps } from "./SquiggleChart";
+import {
-import { useMaybeControlledValue } from "../lib/hooks";
+  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";
 
 const WrappedCodeEditor: React.FC<{
   code: string;
   setCode: (code: string) => void;
-}> = ({ code, setCode }) => (
+  errorLocations?: SqLocation[];
-  <div className="border border-grey-200 p-2 m-4">
+}> = ({ code, setCode, errorLocations }) => (
+  <div className="border border-grey-200 p-2 m-4" data-testid="squiggle-editor">
     <CodeEditor
       value={code}
       onChange={setCode}
       oneLine={true}
       showGutter={false}
       height={20}
+      errorLocations={errorLocations}
     />
   </div>
 );
@@ -24,6 +33,9 @@ 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,
@@ -31,11 +43,50 @@ export const SquiggleEditor: React.FC<SquiggleEditorProps> = (props) => {
     onChange: props.onCodeChange,
   });
 
-  let chartProps = { ...props, code };
+  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);
+
   return (
     <SquiggleContainer>
-      <WrappedCodeEditor code={code} setCode={setCode} />
+      <WrappedCodeEditor
-      <SquiggleChart {...chartProps} />
+        code={code}
+        setCode={setCode}
+        errorLocations={errorLocations}
+      />
+      <SquiggleViewer
+        result={valueToRender}
+        width={width}
+        height={height}
+        distributionPlotSettings={distributionPlotSettings}
+        chartSettings={chartSettings}
+        environment={environment ?? defaultEnvironment}
+        enableLocalSettings={enableLocalSettings}
+      />
     </SquiggleContainer>
   );
 };

packages/components/src/components/SquiggleErrorAlert.tsx

@@ -1,4 +1,4 @@
-import { SqError } from "@quri/squiggle-lang";
+import { SqError, SqFrame } from "@quri/squiggle-lang";
 import React from "react";
 import { ErrorAlert } from "./Alert";
 
@@ -6,6 +6,39 @@ type Props = {
   error: SqError;
 };
 
-export const SquiggleErrorAlert: React.FC<Props> = ({ error }) => {
+const StackTraceFrame: React.FC<{ frame: SqFrame }> = ({ frame }) => {
-  return <ErrorAlert heading="Error">{error.toString()}</ErrorAlert>;
+  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>
+  );
 };

packages/components/src/components/SquigglePlayground.tsx

@@ -8,7 +8,11 @@ import React, {
 } from "react";
 import { useForm, UseFormRegister, useWatch } from "react-hook-form";
 import * as yup from "yup";
-import { useMaybeControlledValue, useRunnerState } from "../lib/hooks";
+import {
+  useMaybeControlledValue,
+  useRunnerState,
+  useSquiggle,
+} from "../lib/hooks";
 import { yupResolver } from "@hookform/resolvers/yup";
 import {
   ChartSquareBarIcon,
@@ -24,9 +28,9 @@ import {
 } from "@heroicons/react/solid";
 import clsx from "clsx";
 
-import { environment } from "@quri/squiggle-lang";
+import { environment, SqProject } from "@quri/squiggle-lang";
 
-import { SquiggleChart, SquiggleChartProps } from "./SquiggleChart";
+import { SquiggleChartProps } from "./SquiggleChart";
 import { CodeEditor } from "./CodeEditor";
 import { JsonEditor } from "./JsonEditor";
 import { ErrorAlert, SuccessAlert } from "./Alert";
@@ -40,6 +44,8 @@ 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 */
@@ -176,7 +182,7 @@ const RunControls: React.FC<{
   const CurrentPlayIcon = isRunning ? RefreshIcon : PlayIcon;
 
   return (
-    <div className="flex space-x-1 items-center">
+    <div className="flex space-x-1 items-center" data-testid="autorun-controls">
       {autorunMode ? null : (
         <button onClick={run}>
           <CurrentPlayIcon
@@ -245,6 +251,8 @@ export const SquigglePlayground: FC<PlaygroundProps> = ({
   onSettingsChange,
   showEditor = true,
   showShareButton = false,
+  continues,
+  project,
 }) => {
   const [code, setCode] = useMaybeControlledValue({
     value: controlledCode,
@@ -282,7 +290,7 @@ export const SquigglePlayground: FC<PlaygroundProps> = ({
     onSettingsChange?.(vars);
   }, [vars, onSettingsChange]);
 
-  const env: environment = useMemo(
+  const environment: environment = useMemo(
     () => ({
       sampleCount: Number(vars.sampleCount),
       xyPointLength: Number(vars.xyPointLength),
@@ -299,26 +307,53 @@ 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}
-        <SquiggleChart
+        <SquiggleViewer
-          code={renderedCode}
+          result={valueToRender}
-          executionId={executionId}
+          environment={environment}
-          environment={env}
+          height={vars.chartHeight || 150}
-          {...vars}
+          distributionPlotSettings={{
-          jsImports={imports}
+            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,
+          }}
           enableLocalSettings={true}
         />
       </div>
     );
 
+  const errorLocations = getErrorLocations(resultAndBindings.result);
+
   const firstTab = vars.showEditor ? (
-    <div className="border border-slate-200">
+    <div className="border border-slate-200" data-testid="squiggle-editor">
       <CodeEditor
+        errorLocations={errorLocations}
         value={code}
         onChange={setCode}
         onSubmit={run}
@@ -368,7 +403,9 @@ export const SquigglePlayground: FC<PlaygroundProps> = ({
       >
         {tabs}
       </div>
-      <div className="w-1/2 p-2 pl-4">{squiggleChart}</div>
+      <div className="w-1/2 p-2 pl-4" data-testid="playground-result">
+        {squiggleChart}
+      </div>
     </div>
   );
 

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, FunctionChartSettings } from "../FunctionChart";
+import { FunctionChart } from "../FunctionChart";
 import clsx from "clsx";
 import { VariableBox } from "./VariableBox";
 import { ItemSettingsMenu } from "./ItemSettingsMenu";

packages/components/src/components/SquiggleViewer/VariableBox.tsx

@@ -1,4 +1,4 @@
-import { SqValue, SqValueLocation } from "@quri/squiggle-lang";
+import { SqValue } 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>
+    <div role={isTopLevel ? "status" : undefined}>
       <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="border-l-2 border-slate-200 hover:border-indigo-600 w-4 cursor-pointer"
+              className="shrink-0 border-l-2 border-slate-200 hover:border-indigo-600 w-4 cursor-pointer"
               onClick={toggleCollapsed}
             ></div>
           ) : null}

packages/components/src/index.ts

@@ -1,3 +1,4 @@
+export { SqProject } from "@quri/squiggle-lang/";
 export { SquiggleChart } from "./components/SquiggleChart";
 export { SquiggleEditor } from "./components/SquiggleEditor";
 export { SquigglePlayground } from "./components/SquigglePlayground";

packages/components/src/lib/hooks/useSquiggle.ts

@@ -1,42 +1,97 @@
-import { environment, SqProject, SqValue } from "@quri/squiggle-lang";
+import {
+  result,
+  SqError,
+  SqProject,
+  SqRecord,
+  SqValue,
+  environment,
+} 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;
-  environment?: environment;
+  project?: SqProject;
-  onChange?: (expr: SqValue | undefined) => void;
+  continues?: string[];
+  onChange?: (expr: SqValue | undefined, sourceName: string) => void;
 };
 
-export const useSquiggle = (args: SquiggleArgs) => {
+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;
+
   const result = useMemo(
     () => {
-      const project = SqProject.create();
+      project.setSource(sourceName, args.code);
-      project.setSource("main", args.code);
+      let fullContinues = continues;
-      if (args.environment) {
-        project.setEnvironment(args.environment);
-      }
       if (args.jsImports && Object.keys(args.jsImports).length) {
         const importsSource = jsImportsToSquiggleCode(args.jsImports);
-        project.setSource("imports", importsSource);
+        project.setSource(importSourceName(sourceName), importsSource);
-        project.setContinues("main", ["imports"]);
+        fullContinues = continues.concat(importSourceName(sourceName));
       }
-      project.run("main");
+      project.setContinues(sourceName, fullContinues);
-      const result = project.getResult("main");
+      project.run(sourceName);
-      const bindings = project.getBindings("main");
+      const result = project.getResult(sourceName);
+      const bindings = project.getBindings(sourceName);
       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.environment, args.jsImports, args.executionId]
+    [
+      args.code,
+      args.jsImports,
+      args.executionId,
+      sourceName,
+      continues,
+      project,
+      env,
+    ]
   );
 
   const { onChange } = args;
 
   useEffect(() => {
-    onChange?.(result.result.tag === "Ok" ? result.result.value : undefined);
+    onChange?.(
-  }, [result, 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]);
 
   return result;
 };

packages/components/src/lib/utility.ts

@@ -1,4 +1,5 @@
-import { result } from "@quri/squiggle-lang";
+import { result, resultMap, SqValueTag } from "@quri/squiggle-lang";
+import { ResultAndBindings } from "./hooks/useSquiggle";
 
 export function flattenResult<a, b>(x: result<a, b>[]): result<a[], b> {
   if (x.length === 0) {
@@ -35,3 +36,18 @@ 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 [];
+  }
+}

packages/components/src/styles/main.css

@@ -22,3 +22,8 @@ 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;
+}

packages/components/test/autorun.test.tsx

@@ -0,0 +1,55 @@
+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")
+  );
+*/
+});

packages/components/test/basic.test.tsx

@@ -1,13 +1,53 @@
-import { render } from "@testing-library/react";
+import { render, screen } from "@testing-library/react";
 import React from "react";
 import "@testing-library/jest-dom";
-import { SquiggleChart } from "../src/index";
+import {
+  SquiggleChart,
+  SquiggleEditor,
+  SquigglePlayground,
+} from "../src/index";
+import { SqProject } from "@quri/squiggle-lang";
 
-test("Logs no warnings or errors", async () => {
+test("Chart logs nothing on render", async () => {
-  debugger;
   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");
+});

packages/components/test/cleanup.test.tsx

@@ -0,0 +1,39 @@
+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([]);
+});

packages/components/vercel.json

@@ -0,0 +1,4 @@
+{
+  "buildCommand": "cd ../.. && npx turbo run build --filter=@quri/squiggle-components",
+  "outputDirectory": "storybook-static"
+}

packages/squiggle-lang/.prettierignore

@@ -3,6 +3,8 @@ lib
 *.bs.js
 *.gen.tsx
 .nyc_output/
-_coverage/
+coverage/
 .cache/
 Reducer_Peggy_GeneratedParser.js
+ReducerProject_IncludeParser.js
+src/rescript/Reducer/Reducer_Peggy/helpers.js

packages/squiggle-lang/__tests__/Distributions/Dotwise_test.res

@@ -32,7 +32,10 @@ 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,
@@ -50,7 +53,8 @@ describe("dotSubtract", () => {
           | Ok(meanValue) => abs_float(meanValue -. meanAnalytical) /. abs_float(meanValue) < 1e-2 // 1% relative error
           | Error(err) => err === DistributionTypes.OperationError(DivisionByZeroError)
           }
-      }),
+        },
+      ),
     )
     pass
   })

packages/squiggle-lang/__tests__/Distributions/Invariants/AlgebraicCombination_test.res

@@ -40,7 +40,9 @@ 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)
@@ -49,9 +51,12 @@ 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 =
@@ -67,8 +72,11 @@ 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 =
@@ -84,7 +92,8 @@ 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.
@@ -122,7 +131,9 @@ 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
@@ -150,8 +161,11 @@ 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)
@@ -166,8 +180,11 @@ 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)
@@ -180,10 +197,14 @@ 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
@@ -212,8 +233,11 @@ 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
@@ -241,8 +265,11 @@ 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)
@@ -256,8 +283,11 @@ 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)
@@ -271,11 +301,15 @@ 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
@@ -304,8 +338,11 @@ 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
@@ -333,8 +370,11 @@ 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)
@@ -348,8 +388,11 @@ 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)
@@ -363,6 +406,7 @@ describe("(Algebraic) addition of distributions", () => {
         // sometimes it works with ~digits=2.
         | Some(x) => x->expect->toBeSoCloseTo(9.190872365862756, ~digits=0)
         }
-    })
+      },
+    )
   })
 })

packages/squiggle-lang/__tests__/Distributions/Invariants/Means_test.res

@@ -3,7 +3,7 @@ This is the most basic file in our invariants family of tests.
 
 Validate that the addition of means equals the mean of the addition, similar for subtraction and multiplication. 
 
-Details in https://develop--squiggle-documentation.netlify.app/docs/internal/invariants/
+Details in https://squiggle-language.com/docs/internal/invariants/
 
 Note: epsilon of 1e3 means the invariants are, in general, not being satisfied. 
 */
@@ -87,14 +87,22 @@ 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",
@@ -116,14 +124,22 @@ 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",
@@ -145,14 +161,22 @@ 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",

packages/squiggle-lang/__tests__/Distributions/Scoring/KlDivergence_test.res

@@ -17,10 +17,9 @@ describe("klDivergence: continuous -> continuous -> float", () => {
       let answer =
         uniformMakeR(lowAnswer, highAnswer)->E.R2.errMap(s => DistributionTypes.ArgumentError(s))
       let prediction =
-        uniformMakeR(
+        uniformMakeR(lowPrediction, highPrediction)->E.R2.errMap(
-          lowPrediction,
+          s => DistributionTypes.ArgumentError(s),
-          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)
@@ -183,9 +182,9 @@ 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(
+      uniformMakeR(lowPrediction, highPrediction)->E.R2.errMap(
-        s,
+        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)
 

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: mean, stdev: stdev}))
+let mkNormal = (mean, stdev) => DistributionTypes.Symbolic(#Normal({mean, stdev}))
 
 describe("(Symbolic) normalize", () => {
   testAll("has no impact on normal distributions", list{-1e8, -1e-2, 0.0, 1e-4, 1e16}, mean => {
@@ -47,10 +47,7 @@ describe("(Symbolic) mean", () => {
     tup => {
       let (low, medium, high) = tup
       let meanValue = run(
-        FromDist(
+        FromDist(#ToFloat(#Mean), DistributionTypes.Symbolic(#Triangular({low, medium, high}))),
-          #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/
     },
@@ -63,7 +60,7 @@ describe("(Symbolic) mean", () => {
     tup => {
       let (alpha, beta) = tup
       let meanValue = run(
-        FromDist(#ToFloat(#Mean), DistributionTypes.Symbolic(#Beta({alpha: alpha, beta: beta}))),
+        FromDist(#ToFloat(#Mean), DistributionTypes.Symbolic(#Beta({alpha, beta}))),
       )
       meanValue->unpackFloat->expect->toBeCloseTo(1.0 /. (1.0 +. beta /. alpha)) // https://en.wikipedia.org/wiki/Beta_distribution#Mean
     },
@@ -84,8 +81,8 @@ describe("(Symbolic) mean", () => {
       let (mean, stdev) = tup
       let betaDistribution = SymbolicDist.Beta.fromMeanAndStdev(mean, stdev)
       let meanValue =
-        betaDistribution->E.R2.fmap(d =>
+        betaDistribution->E.R2.fmap(
-          run(FromDist(#ToFloat(#Mean), d->DistributionTypes.Symbolic))
+          d => run(FromDist(#ToFloat(#Mean), d->DistributionTypes.Symbolic)),
         )
       switch meanValue {
       | Ok(value) => value->unpackFloat->expect->toBeCloseTo(mean)
@@ -100,7 +97,7 @@ describe("(Symbolic) mean", () => {
     tup => {
       let (mu, sigma) = tup
       let meanValue = run(
-        FromDist(#ToFloat(#Mean), DistributionTypes.Symbolic(#Lognormal({mu: mu, sigma: sigma}))),
+        FromDist(#ToFloat(#Mean), DistributionTypes.Symbolic(#Lognormal({mu, sigma}))),
       )
       meanValue->unpackFloat->expect->toBeCloseTo(Js.Math.exp(mu +. sigma ** 2.0 /. 2.0)) // https://brilliant.org/wiki/log-normal-distribution/
     },
@@ -112,7 +109,7 @@ describe("(Symbolic) mean", () => {
     tup => {
       let (low, high) = tup
       let meanValue = run(
-        FromDist(#ToFloat(#Mean), DistributionTypes.Symbolic(#Uniform({low: low, high: high}))),
+        FromDist(#ToFloat(#Mean), DistributionTypes.Symbolic(#Uniform({low, high}))),
       )
       meanValue->unpackFloat->expect->toBeCloseTo((low +. high) /. 2.0) // https://en.wikipedia.org/wiki/Continuous_uniform_distribution#Moments
     },

packages/squiggle-lang/__tests__/Reducer/Reducer_Bindings/Reducer_Bindings_test.res

@@ -33,12 +33,18 @@ 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)
-    })
+      },
+    )
   })
 })

packages/squiggle-lang/__tests__/Reducer/Reducer_Namespace_test.res

@@ -40,14 +40,23 @@ 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)
-    })
+      },
+    )
   })
 })

packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_Parse_test.res

@@ -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
   })

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)->Parse.toStringResult->expect->toBe(answer)
+  Parse.parse(expr, "test")->Parse.toStringResult->expect->toBe(answer)
 
 let testParse = (expr, answer) => test(expr, () => expectParseToBe(expr, answer))
 
-let expectToExpressionToBe = (expr, answer, ~v="_", ()) => {
+let expectExpressionToBe = (expr, answer, ~v="_", ()) => {
-  let rExpr = Parse.parse(expr)->Result.map(ToExpression.fromNode)
+  let rExpr = Parse.parse(expr, "test")->Result.map(ToExpression.fromNode)
   let a1 = rExpr->ExpressionT.toStringResultOkless
 
   if v == "_" {
@@ -22,6 +22,7 @@ let expectToExpressionToBe = (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))
@@ -29,16 +30,16 @@ let expectToExpressionToBe = (expr, answer, ~v="_", ()) => {
 }
 
 let testToExpression = (expr, answer, ~v="_", ()) =>
-  test(expr, () => expectToExpressionToBe(expr, answer, ~v, ()))
+  test(expr, () => expectExpressionToBe(expr, answer, ~v, ()))
 
 module MyOnly = {
   let testParse = (expr, answer) => Only.test(expr, () => expectParseToBe(expr, answer))
   let testToExpression = (expr, answer, ~v="_", ()) =>
-    Only.test(expr, () => expectToExpressionToBe(expr, answer, ~v, ()))
+    Only.test(expr, () => expectExpressionToBe(expr, answer, ~v, ()))
 }
 
 module MySkip = {
   let testParse = (expr, answer) => Skip.test(expr, () => expectParseToBe(expr, answer))
   let testToExpression = (expr, answer, ~v="_", ()) =>
-    Skip.test(expr, () => expectToExpressionToBe(expr, answer, ~v, ()))
+    Skip.test(expr, () => expectExpressionToBe(expr, answer, ~v, ()))
 }

packages/squiggle-lang/__tests__/Reducer/Reducer_Peggy/Reducer_Peggy_ToExpression_test.res

@@ -75,7 +75,9 @@ 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)",
@@ -97,7 +99,8 @@ describe("Peggy to Expression", () => {
           ~v="6",
           (),
         )
-    })
+      },
+    )
   })
 
   describe("if then else", () => {
@@ -135,7 +138,7 @@ 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)}}", ())
   })

packages/squiggle-lang/__tests__/Reducer/Reducer_TestHelpers.res

@@ -1,4 +1,3 @@
-module ErrorValue = Reducer_ErrorValue
 module Expression = Reducer_Expression
 module ExpressionT = Reducer_Expression_T
 
@@ -9,7 +8,7 @@ let unwrapRecord = rValue =>
   rValue->Belt.Result.flatMap(value =>
     switch value {
     | Reducer_T.IEvRecord(aRecord) => Ok(aRecord)
-    | _ => ErrorValue.RETodo("TODO: Internal bindings must be returned")->Error
+    | _ => SqError.Message.RETodo("TODO: Internal bindings must be returned")->Error
     }
   )
 
@@ -23,7 +22,7 @@ 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) =>

packages/squiggle-lang/__tests__/Reducer/Reducer_test.res

@@ -37,14 +37,16 @@ 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})",
-      )
+        ),
     )
   })
 
@@ -70,7 +72,7 @@ describe("test exceptions", () => {
   testDescriptionEvalToBe(
     "javascript exception",
     "javascriptraise('div by 0')",
-    "Error(Error: 'div by 0')",
+    "Error(JS Exception: Error: 'div by 0')",
   )
   // testDescriptionEvalToBe(
   //   "rescript exception",
@@ -78,3 +80,33 @@ 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
+`)
+  })
+})

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->Reducer_ErrorValue.errorToString)
+    | Error(error) => fail(error->SqError.toString)
     }
   })
   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->Reducer_ErrorValue.errorToString)
+    | Error(error) => fail(error->SqError.toString)
     }
   })
 
@@ -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->Reducer_ErrorValue.errorToString)
+    | Error(error) => fail(error->SqError.toString)
     }
   })
   test("direct past chain", () => {

packages/squiggle-lang/__tests__/ReducerProject/ReducerProject_tutorial_1_test.res

@@ -11,7 +11,9 @@ 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. 
@@ -51,9 +53,12 @@ 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
@@ -64,9 +69,12 @@ 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()
 
@@ -78,15 +86,19 @@ 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)", "{}")
-    })
+      },
+    )
   })
 })
 

packages/squiggle-lang/__tests__/ReducerProject/ReducerProject_tutorial_2_multisource_test.res

@@ -10,7 +10,9 @@ 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")
@@ -32,9 +34,12 @@ 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()
@@ -56,9 +61,12 @@ 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. */
@@ -99,6 +107,7 @@ 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. */
-    })
+      },
+    )
   })
 })

packages/squiggle-lang/__tests__/ReducerProject/ReducerProject_tutorial_3_includes_test.res

@@ -24,35 +24,46 @@ 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->Reducer_ErrorValue.errorToString->fail
+        | Error(err) => err->SqError.toString->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.
@@ -85,10 +96,11 @@ 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->Reducer_ErrorValue.errorToString->Js.Exn.raiseError
+            | Error(err) => err->SqError.toString->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)
@@ -97,7 +109,8 @@ 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)
-            })
+                },
+              )
             }
           }
         }
@@ -143,12 +156,18 @@ 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", () => {
+        test(
-        (result->Reducer_Value.toStringResult, bindings->Reducer_Value.toStringRecord)->expect ==
+          "recursive includes",
-          ("Ok(6)", "{a: 6,b: 2}")
+          () => {
+            (
+              result->Reducer_Value.toStringResult,
+              bindings->Reducer_Value.toStringRecord,
+            )->expect == ("Ok(6)", "{a: 6,b: 2}")
             /* Everything as expected */
-      })
+          },
-    })
+        )
+      },
+    )
   })
 
   describe("Includes myFile as myVariable", () => {
@@ -163,14 +182,20 @@ 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->Reducer_ErrorValue.errorToString->fail
+        | Error(err) => err->SqError.toString->fail
         }
-    })
+      },
+    )
   })
 })

packages/squiggle-lang/__tests__/ReducerProject/ReducerProject_tutorial_5_calling_functions.res

@@ -30,8 +30,9 @@ describe("ReducerProject Tutorial", () => {
   })
 
   test("userResults", () => {
-    let userResultsAsString = Belt.Array.map(userResults, aResult =>
+    let userResultsAsString = Belt.Array.map(
-      aResult->Reducer_Value.toStringResult
+      userResults,
+      aResult => aResult->Reducer_Value.toStringResult,
     )
     userResultsAsString->expect == ["Ok(2)", "Ok(4)", "Ok(6)", "Ok(8)", "Ok(10)"]
   })

packages/squiggle-lang/__tests__/SqError_test.res

@@ -0,0 +1,41 @@
+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
+`)
+  })
+})

packages/squiggle-lang/__tests__/SquiggleLibrary/SquiggleLibrary_FunctionRegistryLibrary_test.res

@@ -10,6 +10,8 @@ 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])")
@@ -80,6 +82,10 @@ 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(
@@ -93,15 +99,19 @@ 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, _)) =>
+        FunctionRegistry_Core.Registry.allExamplesWithFns(registry)->E.A2.filter(
-          E.O.isSome(fn.output)
+          ((fn, _)) => E.O.isSome(fn.output),
         ),
       ),
       ((fn, example)) => {

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

packages/squiggle-lang/bsconfig.json

@@ -25,7 +25,6 @@
   ],
   "suffix": ".bs.js",
   "namespace": true,
-  "bs-dependencies": ["bisect_ppx"],
   "bs-dev-dependencies": [
     "@glennsl/rescript-jest",
     "rescript-fast-check",
@@ -45,8 +44,5 @@
   "refmt": 3,
   "warnings": {
     "number": "+A-42-48-9-30-4"
-  },
+  }
-  "ppx-flags": [
-    ["../../node_modules/bisect_ppx/ppx", "--exclude-files", ".*_test\\.res$$"]
-  ]
 }

packages/squiggle-lang/jest.config.js

@@ -2,9 +2,6 @@
 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/",

packages/squiggle-lang/package.json

@@ -22,10 +22,8 @@
     "test:rescript": "jest --modulePathIgnorePatterns=__tests__/TS/*",
     "test:watch": "jest --watchAll",
     "test:fnRegistry": "jest __tests__/SquiggleLibrary/SquiggleLibrary_FunctionRegistryLibrary_test.bs.js",
-    "coverage:rescript": "rm -f *.coverage && yarn clean && BISECT_ENABLE=yes yarn build && yarn test:rescript && bisect-ppx-report html",
+    "coverage:local": "jest --coverage && echo && echo 'Open ./coverage/lcov-report/index.html to see the detailed report.'",
-    "coverage:ts": "yarn clean && yarn build && nyc --reporter=lcov yarn test:ts",
+    "coverage": "jest --coverage && codecov",
-    "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",
@@ -41,7 +39,7 @@
   ],
   "author": "Quantified Uncertainty Research Institute",
   "dependencies": {
-    "@rescript/std": "^9.1.4",
+    "@rescript/std": "^10.0.0",
     "@stdlib/stats": "^0.0.13",
     "jstat": "^1.9.5",
     "lodash": "^4.17.21",
@@ -50,24 +48,20 @@
   },
   "devDependencies": {
     "@glennsl/rescript-jest": "^0.9.2",
-    "@istanbuljs/nyc-config-typescript": "^1.0.2",
     "@types/jest": "^27.5.0",
-    "babel-plugin-transform-es2015-modules-commonjs": "^6.26.2",
+    "chalk": "^5.1.0",
-    "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": "^9.1.4",
+    "rescript": "^10.0.0",
     "rescript-fast-check": "^1.1.1",
     "rescript-js-map": "^1.1.0",
-    "ts-jest": "^27.1.4",
+    "ts-jest": "^29.0.3",
     "ts-loader": "^9.4.1",
     "ts-node": "^10.9.1",
     "typescript": "^4.8.4",

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.toString() : ""
+    result.tag === "Error" ? result.value.toStringWithFrameStack() : ""
   );
 };

packages/squiggle-lang/scripts/run.mjs

@@ -1,11 +1,18 @@
 #!/usr/bin/env node
 import { run } from "./lib.mjs";
 
-const src = process.argv[2];
+import { Command } from "commander";
+
+const program = new Command();
+
+program.arguments("<string>");
+
+const options = program.parse(process.argv);
+
+const src = program.args[0];
 if (!src) {
   throw new Error("Expected src");
 }
-console.log(`Running ${src}`);
 
 const sampleCount = process.env.SAMPLE_COUNT;
 

packages/squiggle-lang/src/js/SqError.ts

@@ -1,17 +1,48 @@
-import * as RSErrorValue from "../rescript/ForTS/ForTS_Reducer_ErrorValue.gen";
+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";
 
 export class SqError {
-  constructor(private _value: RSErrorValue.reducerErrorValue) {}
+  constructor(private _value: RSError.t) {}
 
   toString() {
-    return RSErrorValue.toString(this._value);
+    return RSError.toString(this._value);
   }
 
-  static createTodoError(v: string) {
+  toStringWithStackTrace() {
-    return new SqError(RSErrorValue.createTodoError(v));
+    return RSError.toStringWithStackTrace(this._value);
   }
 
   static createOtherError(v: string) {
-    return new SqError(RSErrorValue.createOtherError(v));
+    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);
   }
 }

packages/squiggle-lang/src/js/SqProject.ts

@@ -1,5 +1,5 @@
 import * as RSProject from "../rescript/ForTS/ForTS_ReducerProject.gen";
-import { reducerErrorValue } from "../rescript/ForTS/ForTS_Reducer_ErrorValue.gen";
+import * as RSError from "../rescript/SqError.gen";
 import { environment } from "../rescript/ForTS/ForTS_Distribution/ForTS_Distribution_Environment.gen";
 import { SqError } from "./SqError";
 import { SqRecord } from "./SqRecord";
@@ -54,7 +54,7 @@ export class SqProject {
     return resultMap2(
       RSProject.getIncludes(this._value, sourceId),
       (a) => a,
-      (v: reducerErrorValue) => new SqError(v)
+      (v: RSError.t) => new SqError(v)
     );
   }
 
@@ -108,7 +108,7 @@ export class SqProject {
             items: [],
           })
         ),
-      (v: reducerErrorValue) => new SqError(v)
+      (v: RSError.t) => new SqError(v)
     );
   }
 

packages/squiggle-lang/src/js/SqValueLocation.ts

@@ -1,4 +1,3 @@
-import { isParenthesisNode } from "mathjs";
 import { SqProject } from "./SqProject";
 
 type PathItem = string | number;

packages/squiggle-lang/src/js/index.ts

@@ -13,7 +13,7 @@ export {
   environment,
   defaultEnvironment,
 } from "../rescript/ForTS/ForTS_Distribution/ForTS_Distribution.gen";
-export { SqError } from "./SqError";
+export { SqError, SqFrame, SqLocation } from "./SqError";
 export { SqShape } from "./SqPointSetDist";
 
 export { resultMap } from "./types";

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

@@ -141,6 +141,7 @@ 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)

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

@@ -99,6 +99,7 @@ let toFloatOperation = (
         }
       }
     }
+
   | (#Stdev | #Variance | #Mode) as op =>
     switch t {
     | SampleSet(s) =>
@@ -129,7 +130,7 @@ let toPointSet = (
     SampleSetDist.toPointSetDist(
       ~samples=r,
       ~samplingInputs={
-        sampleCount: sampleCount,
+        sampleCount,
         outputXYPoints: xyPointLength,
         pointSetDistLength: xyPointLength,
         kernelWidth: None,
@@ -427,6 +428,7 @@ module AlgebraicCombination = {
           ~toSampleSetFn,
         )
       }
+
     | (None, AsMonteCarlo) =>
       StrategyCallOnValidatedInputs.monteCarlo(toSampleSetFn, arithmeticOperation, t1, t2)
     | (None, AsSymbolic) =>
@@ -443,6 +445,7 @@ module AlgebraicCombination = {
             )}`
           Error(RequestedStrategyInvalidError(errString))
         }
+
       | Some(convOp) => StrategyCallOnValidatedInputs.convolution(toPointSetFn, convOp, t1, t2)
       }
     }

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

@@ -69,7 +69,7 @@ let toDiscretePointMassesFromTriangulars = (
       ()
     }
 
-    {n: n - 2, masses: masses, means: means, variances: variances}
+    {n: n - 2, masses, means, 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: masses, means: means, variances: variances}
+    {n: n - 2, masses, means, 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: n, masses: masses, means: means, variances: variances}
+  {n, masses, means, variances}
 }
 
 type argumentPosition = First | Second

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: xyShape,
+  xyShape,
-  interpolation: interpolation,
+  interpolation,
-  integralSumCache: integralSumCache,
+  integralSumCache,
-  integralCache: integralCache,
+  integralCache,
 }
 let shapeMap = (fn, {xyShape, interpolation, integralSumCache, integralCache}: t): t => {
   xyShape: fn(xyShape),
-  interpolation: interpolation,
+  interpolation,
-  integralSumCache: integralSumCache,
+  integralSumCache,
-  integralCache: 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: integralCache}
+let updateIntegralCache = (integralCache, t: t): t => {...t, integralCache}
 
 let sum = (
   ~integralSumCachesFn: (float, float) => option<float>=(_, _) => None,

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: xyShape,
+  xyShape,
-  integralSumCache: integralSumCache,
+  integralSumCache,
-  integralCache: integralCache,
+  integralCache,
 }
 let shapeMap = (fn, {xyShape, integralSumCache, integralCache}: t): t => {
   xyShape: fn(xyShape),
-  integralSumCache: integralSumCache,
+  integralSumCache,
-  integralCache: 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.

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: continuous,
+  continuous,
-  discrete: discrete,
+  discrete,
-  integralSumCache: integralSumCache,
+  integralSumCache,
-  integralCache: 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 = (

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: continuous, discrete: 0.0}
+  let makeContinuous = (continuous: float): t => {continuous, discrete: 0.0}
-  let makeDiscrete = (discrete: float): t => {continuous: 0.0, discrete: discrete}
+  let makeDiscrete = (discrete: float): t => {continuous: 0.0, discrete}
 
   let fmap = (fn: float => float, t: t) => {
     continuous: fn(t.continuous),

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

@@ -4,13 +4,6 @@ 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
 

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: mean, stdev: stdev}))
+      ? Ok(#Normal({mean, 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: mean, stdev: stdev})
+    #Normal({mean, 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: mean, stdev: stdev})
+    #Normal({mean, stdev})
   }
   let subtract = (n1: t, n2: t) => {
     let mean = n1.mean -. n2.mean
     let stdev = Js.Math.sqrt(n1.stdev ** 2. +. n2.stdev ** 2.)
-    #Normal({mean: mean, stdev: stdev})
+    #Normal({mean, 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: mean, stdev: stdev})
+    #Normal({mean, 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: local, scale: scale}))
+      ? Ok(#Cauchy({local, 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: low, medium: medium, high: high}))
+      ? Ok(#Triangular({low, medium, 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: alpha, beta: beta}))
+      ? Ok(#Beta({alpha, 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: mu, sigma: sigma}))
+      ? Ok(#Lognormal({mu, 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: mu, sigma: sigma})
+    #Lognormal({mu, 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: mu, sigma: sigma}))
+      Ok(#Lognormal({mu, 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: mu, sigma: sigma})
+    #Lognormal({mu, 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: mu, sigma: sigma})
+    #Lognormal({mu, 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: low, high: high})) : Error("High must be larger than low")
+    high > low ? Ok(#Uniform({low, 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)
@@ -239,9 +239,7 @@ module Uniform = {
 module Logistic = {
   type t = logistic
   let make = (location, scale) =>
-    scale > 0.0
+    scale > 0.0 ? Ok(#Logistic({location, scale})) : Error("Scale must be positive")
-      ? 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)
@@ -285,7 +283,7 @@ module Gamma = {
   let make = (shape: float, scale: float) => {
     if shape > 0. {
       if scale > 0. {
-        Ok(#Gamma({shape: shape, scale: scale}))
+        Ok(#Gamma({shape, scale}))
       } else {
         Error("scale must be larger than 0")
       }
@@ -543,6 +541,6 @@ 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: xs, ys: ys}))
+      Continuous(Continuous.make(~integralSumCache=Some(1.0), {xs, ys}))
     }
 }

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, errorValue>,
+  fn: array<Reducer_T.value> => result<Reducer_T.value, errorMessage>,
 }
 
 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, errorValue>,
+  fn: array<Reducer_T.value> => result<Reducer_T.value, errorMessage>,
-) => makeFnMany(name, [{inputs: inputs, fn: fn}])
+) => makeFnMany(name, [{inputs, fn}])
 
 let library = [
   Make.ff2f(~name="add", ~fn=(x, y) => x +. y, ()), // infix + (see Reducer/Reducer_Peggy/helpers.ts)
@@ -62,6 +62,7 @@ let library = [
         let answer = Js.String2.concat(a, b)
         answer->Reducer_T.IEvString->Ok
       }
+
     | _ => Error(impossibleError)
     }
   }),
@@ -72,6 +73,7 @@ let library = [
         let _ = Js.Array2.pushMany(a, b)
         a->Reducer_T.IEvArray->Ok
       }
+
     | _ => Error(impossibleError)
     }
   }),
@@ -81,6 +83,7 @@ let library = [
         Js.log(value->Reducer_Value.toString)
         value->Ok
       }
+
     | _ => Error(impossibleError)
     }
   }),
@@ -90,6 +93,7 @@ let library = [
         Js.log(`${label}: ${value->Reducer_Value.toString}`)
         value->Ok
       }
+
     | _ => Error(impossibleError)
     }
   }),

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_Expression_Lambda.doLambdaCall(
+        let resultAsInternalExpression = Reducer_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"->Reducer_ErrorValue.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"->SqError.Message.REOther,
           )
         }
         result
@@ -135,16 +135,18 @@ 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->Reducer_ErrorValue.errorToString)
+        b->SqError.Message.toString)
-        ->Reducer_ErrorValue.REOther
+        ->SqError.Message.REOther
         ->Error
       }
       result
@@ -169,7 +171,7 @@ module Integration = {
             let result = switch inputs {
             | [_, _, _, IEvNumber(0.0)] =>
               "Integration error 4 in Danger.integrate: Increment can't be 0."
-              ->Reducer_ErrorValue.REOther
+              ->SqError.Message.REOther
               ->Error
             | [
                 IEvLambda(aLambda),
@@ -187,7 +189,7 @@ module Integration = {
               )
             | _ =>
               Error(
-                Reducer_ErrorValue.REOther(
+                SqError.Message.REOther(
                   "Integration error 5 in Danger.integrate. Remember that inputs are (function, number (min), number (max), number(increment))",
                 ),
               )
@@ -213,7 +215,7 @@ module Integration = {
             let result = switch inputs {
             | [_, _, _, IEvNumber(0.0)] =>
               "Integration error in Danger.integrate: Increment can't be 0."
-              ->Reducer_ErrorValue.REOther
+              ->SqError.Message.REOther
               ->Error
             | [IEvLambda(aLambda), IEvNumber(min), IEvNumber(max), IEvNumber(epsilon)] =>
               Helpers.integrateFunctionBetweenWithNumIntegrationPoints(
@@ -225,11 +227,11 @@ module Integration = {
                 reducer,
               )->E.R2.errMap(b =>
                 ("Integration error 7 in Danger.integrate. Something went wrong along the way: " ++
-                b->Reducer_ErrorValue.errorToString)->Reducer_ErrorValue.REOther
+                b->SqError.Message.toString)->SqError.Message.REOther
               )
             | _ =>
               "Integration error 8 in Danger.integrate. Remember that inputs are (function, number (min), number (max), number(increment))"
-              ->Reducer_ErrorValue.REOther
+              ->SqError.Message.REOther
               ->Error
             }
             result
@@ -246,7 +248,7 @@ module DiminishingReturns = {
   module Helpers = {
     type diminishingReturnsAccumulatorInner = {
       optimalAllocations: array<float>,
-      currentMarginalReturns: result<array<float>, errorValue>,
+      currentMarginalReturns: result<array<float>, errorMessage>,
     }
     let findBiggestElementIndex = (xs: array<float>) =>
       E.A.reducei(xs, 0, (acc, newElement, index) => {
@@ -255,7 +257,7 @@ module DiminishingReturns = {
         | false => acc
         }
       })
-    type diminishingReturnsAccumulator = result<diminishingReturnsAccumulatorInner, errorValue>
+    type diminishingReturnsAccumulator = result<diminishingReturnsAccumulatorInner, errorMessage>
     // 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 
@@ -290,25 +292,25 @@ module DiminishingReturns = {
       ) {
       | (false, _, _, _) =>
         Error(
-          "Error in Danger.optimalAllocationGivenDiminishingMarginalReturnsForManyFunctions, number of functions should be greater than 1."->Reducer_ErrorValue.REOther,
+          "Error in Danger.optimalAllocationGivenDiminishingMarginalReturnsForManyFunctions, number of functions should be greater than 1."->SqError.Message.REOther,
         )
       | (_, false, _, _) =>
         Error(
-          "Error in Danger.optimalAllocationGivenDiminishingMarginalReturnsForManyFunctions, funds should be greater than 0."->Reducer_ErrorValue.REOther,
+          "Error in Danger.optimalAllocationGivenDiminishingMarginalReturnsForManyFunctions, funds should be greater than 0."->SqError.Message.REOther,
         )
       | (_, _, false, _) =>
         Error(
-          "Error in Danger.optimalAllocationGivenDiminishingMarginalReturnsForManyFunctions, approximateIncrement should be greater than 0."->Reducer_ErrorValue.REOther,
+          "Error in Danger.optimalAllocationGivenDiminishingMarginalReturnsForManyFunctions, approximateIncrement should be greater than 0."->SqError.Message.REOther,
         )
       | (_, _, _, false) =>
         Error(
-          "Error in Danger.optimalAllocationGivenDiminishingMarginalReturnsForManyFunctions, approximateIncrement should be smaller than funds amount."->Reducer_ErrorValue.REOther,
+          "Error in Danger.optimalAllocationGivenDiminishingMarginalReturnsForManyFunctions, approximateIncrement should be smaller than funds amount."->SqError.Message.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_Expression_Lambda.doLambdaCall(
+            let resultAsInternalExpression = Reducer_Lambda.doLambdaCall(
               lambda,
               [pointAsInternalExpression],
               environment,
@@ -318,7 +320,7 @@ 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"->Reducer_ErrorValue.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"->SqError.Message.REOther,
               )
             }
           }
@@ -362,6 +364,7 @@ module DiminishingReturns = {
                         result[indexOfBiggestDMR] = value
                         Ok(result)
                       }
+
                     | Error(b) => Error(b)
                     }
 
@@ -371,10 +374,12 @@ module DiminishingReturns = {
                     }
                     Ok(newAcc)
                   }
+
                 | Error(b) => Error(b)
                 }
                 newAccWrapped
               }
+
             | Error(b) => Error(b)
             }
           })
@@ -411,7 +416,7 @@ module DiminishingReturns = {
                   | Reducer_T.IEvLambda(lambda) => Ok(lambda)
                   | _ =>
                     "Error in Danger.optimalAllocationGivenDiminishingMarginalReturnsForManyFunctions. A member of the array wasn't a function"
-                    ->Reducer_ErrorValue.REOther
+                    ->SqError.Message.REOther
                     ->Error
                   }
                 }, innerlambdas)
@@ -427,13 +432,15 @@ module DiminishingReturns = {
                     )
                     result
                   }
+
                 | Error(b) => Error(b)
                 }
                 result
               }
+
             | _ =>
               "Error in Danger.diminishingMarginalReturnsForTwoFunctions"
-              ->Reducer_ErrorValue.REOther
+              ->SqError.Message.REOther
               ->Error
             },
           (),

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, errorValue>,
+  fn: array<Reducer_T.value> => result<Reducer_T.value, errorMessage>,
 ) =>
   Function.make(
     ~name,
@@ -66,7 +66,7 @@ let library = [
     | [IEvNumber(year)] =>
       switch DateTime.Date.makeFromYear(year) {
       | Ok(t) => IEvDate(t)->Ok
-      | Error(e) => Reducer_ErrorValue.RETodo(e)->Error
+      | Error(e) => SqError.Message.RETodo(e)->Error
       }
     | _ => Error(impossibleError)
     }

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, errorValue> =>
+  let fromList = (items: array<Reducer_T.value>): result<Reducer_T.value, errorMessage> =>
     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->Reducer_ErrorValue.toException
+              | _ => impossibleError->SqError.Message.throw
               }
             )
             ->Internals.mergeMany

packages/squiggle-lang/src/rescript/FR/FR_Dist.res

@@ -16,13 +16,14 @@ module DistributionCreation = {
       r
       ->E.R.bind(Process.DistOrNumberToDist.twoValuesUsingSymbolicDist(~fn, ~values=_, ~env))
       ->E.R2.fmap(Wrappers.evDistribution)
-      ->E.R2.errMap(e => Reducer_ErrorValue.REOther(e))
+      ->E.R2.errMap(e => SqError.Message.REOther(e))
 
     let make = (name, fn) => {
       FnDefinition.make(
         ~name,
         ~inputs=[FRTypeDistOrNumber, FRTypeDistOrNumber],
-        ~run=(inputs, env, _) => inputs->Prepare.ToValueTuple.twoDistOrNumber->process(~fn, ~env),
+        ~run=(inputs, context, _) =>
+          inputs->Prepare.ToValueTuple.twoDistOrNumber->process(~fn, ~env=context.environment),
         (),
       )
     }
@@ -31,8 +32,10 @@ module DistributionCreation = {
       FnDefinition.make(
         ~name,
         ~inputs=[FRTypeRecord([("p5", FRTypeDistOrNumber), ("p95", FRTypeDistOrNumber)])],
-        ~run=(inputs, env, _) =>
+        ~run=(inputs, context, _) =>
-          inputs->Prepare.ToValueTuple.Record.twoDistOrNumber(("p5", "p95"))->process(~fn, ~env),
+          inputs
+          ->Prepare.ToValueTuple.Record.twoDistOrNumber(("p5", "p95"))
+          ->process(~fn, ~env=context.environment),
         (),
       )
     }
@@ -41,10 +44,10 @@ module DistributionCreation = {
       FnDefinition.make(
         ~name,
         ~inputs=[FRTypeRecord([("mean", FRTypeDistOrNumber), ("stdev", FRTypeDistOrNumber)])],
-        ~run=(inputs, env, _) =>
+        ~run=(inputs, context, _) =>
           inputs
           ->Prepare.ToValueTuple.Record.twoDistOrNumber(("mean", "stdev"))
-          ->process(~fn, ~env),
+          ->process(~fn, ~env=context.environment),
         (),
       )
     }
@@ -55,13 +58,14 @@ module DistributionCreation = {
       r
       ->E.R.bind(Process.DistOrNumberToDist.oneValueUsingSymbolicDist(~fn, ~value=_, ~env))
       ->E.R2.fmap(Wrappers.evDistribution)
-      ->E.R2.errMap(e => Reducer_ErrorValue.REOther(e))
+      ->E.R2.errMap(e => SqError.Message.REOther(e))
 
     let make = (name, fn) =>
       FnDefinition.make(
         ~name,
         ~inputs=[FRTypeDistOrNumber],
-        ~run=(inputs, env, _) => inputs->Prepare.ToValueTuple.oneDistOrNumber->process(~fn, ~env),
+        ~run=(inputs, context, _) =>
+          inputs->Prepare.ToValueTuple.oneDistOrNumber->process(~fn, ~env=context.environment),
         (),
       )
   }

packages/squiggle-lang/src/rescript/FR/FR_Fn.res

@@ -20,6 +20,7 @@ module Declaration = {
         ->E.A.R.firstErrorOrOpen
         ->E.R2.fmap(args => Reducer_T.IEvDeclaration(Declaration.make(lambda, args)))
       }
+
     | Error(r) => Error(r)
     | Ok(_) => Error(impossibleErrorString)
     }

packages/squiggle-lang/src/rescript/FR/FR_GenericDist.res

@@ -140,6 +140,7 @@ module Old = {
             | Error(err) => error(err)
             }
           }
+
         | Some(IEvNumber(_))
         | Some(IEvDistribution(_)) =>
           switch parseDistributionArray(args) {
@@ -192,6 +193,7 @@ 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)]) =>
@@ -296,7 +298,7 @@ module Old = {
 
   let genericOutputToReducerValue = (o: DistributionOperation.outputType): result<
     Reducer_T.value,
-    Reducer_ErrorValue.errorValue,
+    SqError.Message.t,
   > =>
     switch o {
     | Dist(d) => Ok(Reducer_T.IEvDistribution(d))
@@ -311,9 +313,9 @@ module Old = {
     switch dispatchToGenericOutput(call, environment) {
     | Some(o) => genericOutputToReducerValue(o)
     | None =>
-      Reducer_ErrorValue.REOther("Internal error in FR_GenericDist implementation")
+      SqError.Message.REOther(
-      ->Reducer_ErrorValue.ErrorException
+        "Internal error in FR_GenericDist implementation",
-      ->raise
+      )->SqError.Message.throw
     }
 }
 
@@ -326,7 +328,7 @@ let makeProxyFn = (name: string, inputs: array<frType>) => {
       FnDefinition.make(
         ~name,
         ~inputs,
-        ~run=(inputs, env, _) => Old.dispatch((name, inputs), env),
+        ~run=(inputs, context, _) => Old.dispatch((name, inputs), context.environment),
         (),
       ),
     ],
@@ -402,9 +404,9 @@ let library = E.A.concatMany([
 ])
 
 // FIXME - impossible to implement with FR due to arbitrary parameters length;
-let mxLambda = Reducer_Expression_Lambda.makeFFILambda((inputs, env, _) => {
+let mxLambda = Reducer_Lambda.makeFFILambda("mx", (inputs, context, _) => {
-  switch Old.dispatch(("mx", inputs), env) {
+  switch Old.dispatch(("mx", inputs), context.environment) {
   | Ok(value) => value
-  | Error(e) => e->Reducer_ErrorValue.ErrorException->raise
+  | Error(e) => e->SqError.Message.throw
   }
 })

packages/squiggle-lang/src/rescript/FR/FR_List.res

@@ -5,6 +5,10 @@ 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),
   )
@@ -26,11 +30,11 @@ module Internals = {
   let map = (
     array: array<Reducer_T.value>,
     eLambdaValue,
-    env: Reducer_T.environment,
+    context: Reducer_T.context,
     reducer: Reducer_T.reducerFn,
   ): Reducer_T.value => {
     Belt.Array.map(array, elem =>
-      Reducer_Expression_Lambda.doLambdaCall(eLambdaValue, [elem], env, reducer)
+      Reducer_Lambda.doLambdaCall(eLambdaValue, [elem], context, reducer)
     )->Wrappers.evArray
   }
 
@@ -38,11 +42,11 @@ module Internals = {
     aValueArray,
     initialValue,
     aLambdaValue,
-    env: Reducer_T.environment,
+    context: Reducer_T.context,
     reducer: Reducer_T.reducerFn,
   ) => {
     aValueArray->E.A.reduce(initialValue, (acc, elem) =>
-      Reducer_Expression_Lambda.doLambdaCall(aLambdaValue, [acc, elem], env, reducer)
+      Reducer_Lambda.doLambdaCall(aLambdaValue, [acc, elem], context, reducer)
     )
   }
 
@@ -50,22 +54,22 @@ module Internals = {
     aValueArray,
     initialValue,
     aLambdaValue,
-    env: Reducer_T.environment,
+    context: Reducer_T.context,
     reducer: Reducer_T.reducerFn,
   ) => {
     aValueArray->Belt.Array.reduceReverse(initialValue, (acc, elem) =>
-      Reducer_Expression_Lambda.doLambdaCall(aLambdaValue, [acc, elem], env, reducer)
+      Reducer_Lambda.doLambdaCall(aLambdaValue, [acc, elem], context, reducer)
     )
   }
 
   let filter = (
     aValueArray,
     aLambdaValue,
-    env: Reducer_T.environment,
+    context: Reducer_T.context,
     reducer: Reducer_T.reducerFn,
   ) => {
     Js.Array2.filter(aValueArray, elem => {
-      let result = Reducer_Expression_Lambda.doLambdaCall(aLambdaValue, [elem], env, reducer)
+      let result = Reducer_Lambda.doLambdaCall(aLambdaValue, [elem], context, reducer)
       switch result {
       | IEvBool(true) => true
       | _ => false
@@ -75,6 +79,26 @@ 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,

packages/squiggle-lang/src/rescript/FR/FR_Pointset.res

@@ -16,30 +16,31 @@ 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->Reducer_ErrorValue.toException
+          | _ => impossibleError->SqError.Message.throw
           }
         }
-      | _ => impossibleError->Reducer_ErrorValue.toException
+
+      | _ => impossibleError->SqError.Message.throw
       }
     )
     ->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->Reducer_ErrorValue.toException
+  | _ => impossibleError->SqError.Message.throw
   }
 }
 
 module Internal = {
   type t = PointSetDist.t
 
-  let toType = (r): result<Reducer_T.value, Reducer_ErrorValue.errorValue> =>
+  let toType = (r): result<Reducer_T.value, SqError.Message.t> =>
     switch r {
     | Ok(r) => Ok(Wrappers.evDistribution(PointSet(r)))
     | Error(err) => Error(REOperationError(err))
     }
 
   let doLambdaCall = (aLambdaValue, list, env, reducer) =>
-    switch Reducer_Expression_Lambda.doLambdaCall(aLambdaValue, list, env, reducer) {
+    switch Reducer_Lambda.doLambdaCall(aLambdaValue, list, env, reducer) {
     | Reducer_T.IEvNumber(f) => Ok(f)
     | _ => Error(Operation.SampleMapNeedsNtoNFunction)
     }
@@ -61,18 +62,18 @@ let library = [
       FnDefinition.make(
         ~name="fromDist",
         ~inputs=[FRTypeDist],
-        ~run=(inputs, env, _) =>
+        ~run=(inputs, context, _) =>
           switch inputs {
           | [IEvDistribution(dist)] =>
             GenericDist.toPointSet(
               dist,
-              ~xyPointLength=env.xyPointLength,
+              ~xyPointLength=context.environment.xyPointLength,
-              ~sampleCount=env.sampleCount,
+              ~sampleCount=context.environment.sampleCount,
               (),
             )
             ->E.R2.fmap(Wrappers.pointSet)
             ->E.R2.fmap(Wrappers.evDistribution)
-            ->E.R2.errMap(e => Reducer_ErrorValue.REDistributionError(e))
+            ->E.R2.errMap(e => SqError.Message.REDistributionError(e))
           | _ => Error(impossibleError)
           },
         (),

packages/squiggle-lang/src/rescript/FR/FR_Sampleset.res

@@ -10,41 +10,40 @@ module Internal = {
   let doLambdaCall = (
     aLambdaValue,
     list,
-    env: Reducer_T.environment,
+    context: Reducer_T.context,
     reducer: Reducer_T.reducerFn,
   ) =>
-    switch Reducer_Expression_Lambda.doLambdaCall(aLambdaValue, list, env, reducer) {
+    switch Reducer_Lambda.doLambdaCall(aLambdaValue, list, context, reducer) {
     | IEvNumber(f) => Ok(f)
     | _ => Error(Operation.SampleMapNeedsNtoNFunction)
     }
 
-  let toType = (r): result<Reducer_T.value, Reducer_ErrorValue.errorValue> =>
+  let toType = (r): result<Reducer_T.value, SqError.Message.t> =>
     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, environment: Reducer_T.environment, reducer: Reducer_T.reducerFn) => {
+  let fromFn = (aLambdaValue, context: Reducer_T.context, reducer: Reducer_T.reducerFn) => {
-    let sampleCount = environment.sampleCount
+    let sampleCount = context.environment.sampleCount
-    let fn = r => doLambdaCall(aLambdaValue, [IEvNumber(r)], environment, reducer)
+    let fn = r => doLambdaCall(aLambdaValue, [IEvNumber(r)], context, reducer)
     Belt_Array.makeBy(sampleCount, r => fn(r->Js.Int.toFloat))->E.A.R.firstErrorOrOpen
   }
 
-  let map1 = (sampleSetDist: t, aLambdaValue, environment: Reducer_T.environment, reducer) => {
+  let map1 = (sampleSetDist: t, aLambdaValue, context: Reducer_T.context, reducer) => {
-    let fn = r => doLambdaCall(aLambdaValue, [IEvNumber(r)], environment, reducer)
+    let fn = r => doLambdaCall(aLambdaValue, [IEvNumber(r)], context, reducer)
     SampleSetDist.samplesMap(~fn, sampleSetDist)->toType
   }
 
-  let map2 = (t1: t, t2: t, aLambdaValue, environment: Reducer_T.environment, reducer) => {
+  let map2 = (t1: t, t2: t, aLambdaValue, context: Reducer_T.context, reducer) => {
-    let fn = (a, b) =>
+    let fn = (a, b) => doLambdaCall(aLambdaValue, [IEvNumber(a), IEvNumber(b)], context, reducer)
-      doLambdaCall(aLambdaValue, [IEvNumber(a), IEvNumber(b)], environment, reducer)
     SampleSetDist.map2(~fn, ~t1, ~t2)->toType
   }
 
-  let map3 = (t1: t, t2: t, t3: t, aLambdaValue, environment: Reducer_T.environment, reducer) => {
+  let map3 = (t1: t, t2: t, t3: t, aLambdaValue, context: Reducer_T.context, reducer) => {
     let fn = (a, b, c) =>
-      doLambdaCall(aLambdaValue, [IEvNumber(a), IEvNumber(b), IEvNumber(c)], environment, reducer)
+      doLambdaCall(aLambdaValue, [IEvNumber(a), IEvNumber(b), IEvNumber(c)], context, reducer)
     SampleSetDist.map3(~fn, ~t1, ~t2, ~t3)->toType
   }
 
@@ -60,7 +59,7 @@ module Internal = {
   let mapN = (
     aValueArray: array<Reducer_T.value>,
     aLambdaValue,
-    environment: Reducer_T.environment,
+    context: Reducer_T.context,
     reducer,
   ) => {
     switch parseSampleSetArray(aValueArray) {
@@ -69,7 +68,7 @@ module Internal = {
         doLambdaCall(
           aLambdaValue,
           [IEvArray(E.A.fmap(x => Wrappers.evNumber(x), a))],
-          environment,
+          context,
           reducer,
         )
       SampleSetDist.mapN(~fn, ~t1)->toType
@@ -89,13 +88,13 @@ let libaryBase = [
       FnDefinition.make(
         ~name="fromDist",
         ~inputs=[FRTypeDist],
-        ~run=(inputs, environment, _) =>
+        ~run=(inputs, context, _) =>
           switch inputs {
           | [IEvDistribution(dist)] =>
-            GenericDist.toSampleSetDist(dist, environment.sampleCount)
+            GenericDist.toSampleSetDist(dist, context.environment.sampleCount)
             ->E.R2.fmap(Wrappers.sampleSet)
             ->E.R2.fmap(Wrappers.evDistribution)
-            ->E.R2.errMap(e => Reducer_ErrorValue.REDistributionError(e))
+            ->E.R2.errMap(e => SqError.Message.REDistributionError(e))
           | _ => Error(impossibleError)
           },
         (),
@@ -116,7 +115,7 @@ let libaryBase = [
         ~run=(inputs, _, _) => {
           let sampleSet =
             inputs->Prepare.ToTypedArray.numbers
-              |> E.R2.bind(r => SampleSetDist.make(r)->E.R2.errMap(_ => "AM I HERE? WHYERE AMI??"))
+              |> E.R2.bind(r => SampleSetDist.make(r)->E.R2.errMap(SampleSetDist.Error.toString))
           sampleSet
           ->E.R2.fmap(Wrappers.sampleSet)
           ->E.R2.fmap(Wrappers.evDistribution)
@@ -163,7 +162,7 @@ let libaryBase = [
           | [IEvLambda(lambda)] =>
             switch Internal.fromFn(lambda, environment, reducer) {
             | Ok(r) => Ok(r->Wrappers.sampleSet->Wrappers.evDistribution)
-            | Error(e) => e->Reducer_ErrorValue.REOperationError->Error
+            | Error(e) => e->SqError.Message.REOperationError->Error
             }
           | _ => Error(impossibleError)
           },
@@ -290,7 +289,7 @@ module Comparison = {
     r
     ->E.R2.fmap(r => r->Wrappers.sampleSet->Wrappers.evDistribution)
     ->E.R2.errMap(e =>
-      e->DistributionTypes.Error.sampleErrorToDistErr->Reducer_ErrorValue.REDistributionError
+      e->DistributionTypes.Error.sampleErrorToDistErr->SqError.Message.REDistributionError
     )
 
   let mkBig = (name, withDist, withFloat) =>

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 => Reducer_ErrorValue.REDistributionError(e))
+  ->E.R2.errMap(e => SqError.Message.REDistributionError(e))
 }
 
 let library = [
@@ -30,15 +30,15 @@ let library = [
             ("prior", FRTypeDist),
           ]),
         ],
-        ~run=(inputs, environment, _) => {
+        ~run=(inputs, context, _) => {
           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), environment)
+            runScoring(estimate, Score_Dist(d), Some(prior), context.environment)
           | Ok([IEvDistribution(estimate), IEvNumber(d), IEvDistribution(prior)]) =>
-            runScoring(estimate, Score_Scalar(d), Some(prior), environment)
+            runScoring(estimate, Score_Scalar(d), Some(prior), context.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, environment, _) => {
+        ~run=(inputs, context, _) => {
           switch FunctionRegistry_Helpers.Prepare.ToValueArray.Record.twoArgs(
             inputs,
             ("estimate", "answer"),
           ) {
           | Ok([IEvDistribution(estimate), IEvDistribution(d)]) =>
-            runScoring(estimate, Score_Dist(d), None, environment)
+            runScoring(estimate, Score_Dist(d), None, context.environment)
           | Ok([IEvDistribution(estimate), IEvNumber(d)]) =>
-            runScoring(estimate, Score_Scalar(d), None, environment)
+            runScoring(estimate, Score_Scalar(d), None, context.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, environment, _) => {
+        ~run=(inputs, context, _) => {
           switch inputs {
           | [IEvDistribution(estimate), IEvDistribution(d)] =>
-            runScoring(estimate, Score_Dist(d), None, environment)
+            runScoring(estimate, Score_Dist(d), None, context.environment)
           | _ => Error(FunctionRegistry_Helpers.impossibleError)
           }
         },

packages/squiggle-lang/src/rescript/ForTS/ForTS_ReducerProject.res

@@ -1,6 +1,7 @@
 @genType type reducerProject = ReducerProject_T.project //re-export
 
-type reducerErrorValue = ForTS_Reducer_ErrorValue.reducerErrorValue //use
+type error = SqError.t //use
+type errorMessage = SqError.Message.t //use
 
 type squiggleValue = ForTS_SquiggleValue.squiggleValue //use
 type squiggleValue_Record = ForTS_SquiggleValue.squiggleValue_Record //use
@@ -103,10 +104,8 @@ 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<
+let getIncludes = (project: reducerProject, sourceId: string): result<array<string>, error> =>
-  array<string>,
+  project->Private.getIncludes(sourceId)
-  reducerErrorValue,
-> => project->Private.getIncludes(sourceId)
 
 /* Other sources contributing to the global namespace of this source. */
 @genType
@@ -198,10 +197,8 @@ 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<
+let getResult = (project: reducerProject, sourceId: string): result<squiggleValue, error> =>
-  squiggleValue,
+  project->Private.getResult(sourceId)
-  reducerErrorValue,
-> => project->Private.getResult(sourceId)
 
 /*
 This is a convenience function to get the result of a single source without creating a project. 
@@ -209,10 +206,8 @@ However, without a project, you cannot handle include directives.
 The source has to be include free
 */
 @genType
-let evaluate = (sourceCode: string): (
+let evaluate = (sourceCode: string): (result<squiggleValue, error>, squiggleValue_Record) =>
-  result<squiggleValue, reducerErrorValue>,
+  Private.evaluate(sourceCode)
-  squiggleValue_Record,
-) => Private.evaluate(sourceCode)
 
 @genType
 let setEnvironment = (project: reducerProject, environment: environment): unit =>
@@ -220,24 +215,3 @@ 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,
-//   )
-// }

packages/squiggle-lang/src/rescript/ForTS/ForTS_Reducer_ErrorValue.res

@@ -1,18 +0,0 @@
-@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)

packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue.res

@@ -1,5 +1,5 @@
 @genType type squiggleValue = Reducer_T.value //re-export
-type reducerErrorValue = ForTS_Reducer_ErrorValue.reducerErrorValue //use
+type error = SqError.t //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, reducerErrorValue>) =>
+let toStringResult = (variantResult: result<squiggleValue, error>) =>
   Reducer_Value.toStringResult(variantResult)
 
 @genType

packages/squiggle-lang/src/rescript/ForTS/ForTS_SquiggleValue/ForTS_SquiggleValue_Lambda.res

@@ -1,9 +1,7 @@
 @genType type squiggleValue_Lambda = Reducer_T.lambdaValue //re-export
 
 @genType
-let toString = (v: squiggleValue_Lambda): string => Reducer_Value.toStringFunction(v)
+let toString = (v: squiggleValue_Lambda): string => Reducer_Value.toStringLambda(v)
 
 @genType
-let parameters = (v: squiggleValue_Lambda): array<string> => {
+let parameters = (v: squiggleValue_Lambda): array<string> => Reducer_Lambda.parameters(v)
-  v.parameters
-}

packages/squiggle-lang/src/rescript/ForTS/ForTS__Types.res

@@ -1,6 +1,3 @@
-@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

packages/squiggle-lang/src/rescript/FunctionRegistry/FunctionRegistry_Core.res

@@ -1,5 +1,5 @@
 type internalExpressionValueType = Reducer_Value.internalExpressionValueType
-type errorValue = Reducer_ErrorValue.errorValue
+type errorMessage = SqError.Message.t
 
 /*
   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.environment,
+    Reducer_T.context,
     Reducer_T.reducerFn,
-  ) => result<Reducer_T.value, errorValue>,
+  ) => result<Reducer_T.value, errorMessage>,
 }
 
 type function = {
@@ -61,6 +61,7 @@ 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`
@@ -122,19 +123,19 @@ module FnDefinition = {
   let run = (
     t: t,
     args: array<Reducer_T.value>,
-    env: Reducer_T.environment,
+    context: Reducer_T.context,
     reducer: Reducer_T.reducerFn,
   ) => {
     switch t->isMatch(args) {
-    | true => t.run(args, env, reducer)
+    | true => t.run(args, context, reducer)
     | false => REOther("Incorrect Types")->Error
     }
   }
 
   let make = (~name, ~inputs, ~run, ()): t => {
-    name: name,
+    name,
-    inputs: inputs,
+    inputs,
-    run: run,
+    run,
   }
 }
 
@@ -160,14 +161,14 @@ module Function = {
     ~isExperimental=false,
     (),
   ): t => {
-    name: name,
+    name,
-    nameSpace: nameSpace,
+    nameSpace,
-    definitions: definitions,
+    definitions,
-    output: output,
+    output,
-    examples: examples |> E.O.default([]),
+    examples: examples->E.O2.default([]),
-    isExperimental: isExperimental,
+    isExperimental,
-    requiresNamespace: requiresNamespace,
+    requiresNamespace,
-    description: description,
+    description,
   }
 
   let toJson = (t: t): functionJson => {
@@ -203,15 +204,19 @@ 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])
             }
-        })
+          },
+        )
       })
     )
   }
@@ -225,9 +230,9 @@ module Registry = {
     registry,
     fnName: string,
     args: array<Reducer_T.value>,
-    env: Reducer_T.environment,
+    context: Reducer_T.context,
     reducer: Reducer_T.reducerFn,
-  ): result<Reducer_T.value, errorValue> => {
+  ): result<Reducer_T.value, errorMessage> => {
     switch Belt.Map.String.get(registry.fnNameDict, fnName) {
     | Some(definitions) => {
         let showNameMatchDefinitions = () => {
@@ -241,10 +246,11 @@ module Registry = {
 
         let match = definitions->Js.Array2.find(def => def->FnDefinition.isMatch(args))
         switch match {
-        | Some(def) => def->FnDefinition.run(args, env, reducer)
+        | Some(def) => def->FnDefinition.run(args, context, reducer)
         | None => REOther(showNameMatchDefinitions())->Error
         }
       }
+
     | None => RESymbolNotFound(fnName)->Error
     }
   }

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: errorValue = impossibleErrorString->Reducer_ErrorValue.REOther
+let impossibleError: errorMessage = impossibleErrorString->SqError.Message.REOther
-let wrapError = e => Reducer_ErrorValue.REOther(e)
+let wrapError = e => SqError.Message.REOther(e)
 
 module Wrappers = {
   let symbolic = r => DistributionTypes.Symbolic(r)
@@ -34,6 +34,7 @@ module Prepare = {
             let n2 = map->Belt.Map.String.getExn(arg2)
             Ok([n1, n2])
           }
+
         | _ => Error(impossibleErrorString)
         }
 
@@ -45,6 +46,7 @@ module Prepare = {
             let n3 = map->Belt.Map.String.getExn(arg3)
             Ok([n1, n2, n3])
           }
+
         | _ => Error(impossibleErrorString)
         }
     }

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: namespace, parent: None}
+let fromNamespace = (namespace: Reducer_Namespace.t): t => {namespace, parent: None}

packages/squiggle-lang/src/rescript/Reducer/Reducer_Context.res

@@ -4,9 +4,13 @@ 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: environment,
+    environment,
+    inFunction: None,
   }
 }
 
-let createDefaultContext = (): t => createContext(SquiggleLibrary_StdLib.stdLib, defaultEnvironment)
+let currentFunctionName = (t: t): string => {
+  t.inFunction->E.O2.fmap(Reducer_Lambda_T.name)->E.O2.default(Reducer_T.topFrameName)
+}

packages/squiggle-lang/src/rescript/Reducer/Reducer_Dispatch/Reducer_Dispatch_ChainPiece.res

@@ -1,27 +0,0 @@
-// 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
-}
-
-*/

packages/squiggle-lang/src/rescript/Reducer/Reducer_Dispatch/Reducer_Dispatch_T.res

@@ -1,21 +0,0 @@
-// 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>
-

packages/squiggle-lang/src/rescript/Reducer/Reducer_ErrorValue.res

@@ -1,83 +0,0 @@
-//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))

packages/squiggle-lang/src/rescript/Reducer/Reducer_Exception.res

@@ -1,3 +0,0 @@
-// 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)

packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression.res

@@ -1,16 +1,25 @@
 module Bindings = Reducer_Bindings
-module Lambda = Reducer_Expression_Lambda
 module Result = Belt.Result
 module T = Reducer_T
 
-type errorValue = Reducer_ErrorValue.errorValue
+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),
+    ),
+  )
 
 /*
   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 {
+  switch expression.content {
   | T.EBlock(statements) => {
       let innerContext = {...context, bindings: context.bindings->Bindings.extend}
       let (value, _) =
@@ -49,7 +58,7 @@ 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")->Reducer_ErrorValue.ErrorException->raise
+          | _ => REOther("Record keys must be strings")->throwFrom(expression, context)
           }
           let (value, _) = eValue->evaluate(context)
           (keyString, value)
@@ -73,7 +82,7 @@ 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 => Reducer_ErrorValue.RESymbolNotFound(name)->Reducer_ErrorValue.ErrorException->raise
+    | None => RESymbolNotFound(name)->throwFrom(expression, context)
     }
 
   | T.EValue(value) => (value, context)
@@ -82,28 +91,40 @@ 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", "")->Reducer_ErrorValue.ErrorException->raise
+      | _ => REExpectedType("Boolean", "")->throwFrom(expression, context)
       }
     }
 
-  | T.ELambda(parameters, body) => (
+  | T.ELambda(parameters, body, name) => (
-      Lambda.makeLambda(parameters, context.bindings, body)->T.IEvLambda,
+      Reducer_Lambda.makeLambda(
+        name,
+        parameters,
+        context.bindings,
+        body,
+        expression->toLocation,
+      )->T.IEvLambda,
       context,
     )
 
   | T.ECall(fn, args) => {
       let (lambda, _) = fn->evaluate(context)
-      let argValues = Js.Array2.map(args, arg => {
+      let argValues = Belt.Array.map(args, arg => {
         let (argValue, _) = arg->evaluate(context)
         argValue
       })
       switch lambda {
-      | T.IEvLambda(lambda) => (
+      | T.IEvLambda(lambda) => {
-          Lambda.doLambdaCall(lambda, argValues, context.environment, evaluate),
+          let result = Reducer_Lambda.doLambdaCallFrom(
+            lambda,
+            argValues,
             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)->Reducer_ErrorValue.ErrorException->raise
+        }
+
+      | _ => RENotAFunction(lambda->Reducer_Value.toString)->throwFrom(expression, context)
       }
     }
   }
@@ -112,19 +133,22 @@ 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, errorValue> =>
+  let parse = (peggyCode: string): result<T.expression, Reducer_Peggy_Parse.parseError> =>
-    peggyCode->Reducer_Peggy_Parse.parse->Result.map(Reducer_Peggy_ToExpression.fromNode)
+    peggyCode->Reducer_Peggy_Parse.parse("main")->Result.map(Reducer_Peggy_ToExpression.fromNode)
 
-  let evaluate = (expression: T.expression): result<T.value, errorValue> => {
+  let createDefaultContext = () =>
-    let context = Reducer_Context.createDefaultContext()
+    Reducer_Context.createContext(SquiggleLibrary_StdLib.stdLib, Reducer_Context.defaultEnvironment)
+
+  let evaluate = (expression: T.expression): result<T.value, SqError.t> => {
+    let context = createDefaultContext()
     try {
       let (value, _) = expression->evaluate(context)
       value->Ok
     } catch {
-    | exn => Reducer_ErrorValue.fromException(exn)->Error
+    | exn => exn->SqError.fromException->Error
     }
   }
 
-  let evaluateString = (peggyCode: string): result<T.value, errorValue> =>
+  let evaluateString = (peggyCode: string): result<T.value, SqError.t> =>
-    parse(peggyCode)->Result.flatMap(evaluate)
+    parse(peggyCode)->E.R2.errMap(e => e->SqError.fromParseError)->Result.flatMap(evaluate)
 }

packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_ExpressionBuilder.res

@@ -1,16 +1,19 @@
-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>) => anArray->T.EArray
+let eArray = (anArray: array<T.expression>): expressionContent => anArray->T.EArray
 
 let eBool = aBool => aBool->T.IEvBool->T.EValue
 
-let eCall = (fn: expression, args: array<expression>): expression => T.ECall(fn, args)
+let eCall = (fn: expression, args: array<expression>): expressionContent => T.ECall(fn, args)
 
-let eLambda = (parameters: array<string>, expr: expression) => T.ELambda(parameters, expr)
+let eLambda = (
+  parameters: array<string>,
+  expr: expression,
+  name: option<string>,
+): expressionContent => T.ELambda(parameters, expr, name)
 
 let eNumber = aNumber => aNumber->T.IEvNumber->T.EValue
 
@@ -18,13 +21,13 @@ let eRecord = (aMap: array<(T.expression, T.expression)>) => aMap->T.ERecord
 
 let eString = aString => aString->T.IEvString->T.EValue
 
-let eSymbol = (name: string): expression => T.ESymbol(name)
+let eSymbol = (name: string): expressionContent => T.ESymbol(name)
 
-let eBlock = (exprs: array<expression>): expression => T.EBlock(exprs)
+let eBlock = (exprs: array<expression>): expressionContent => T.EBlock(exprs)
 
-let eProgram = (exprs: array<expression>): expression => T.EProgram(exprs)
+let eProgram = (exprs: array<expression>): expressionContent => T.EProgram(exprs)
 
-let eLetStatement = (symbol: string, valueExpression: expression): expression => T.EAssign(
+let eLetStatement = (symbol: string, valueExpression: expression): expressionContent => T.EAssign(
   symbol,
   valueExpression,
 )
@@ -33,11 +36,8 @@ let eTernary = (
   predicate: expression,
   trueCase: expression,
   falseCase: expression,
-): expression => T.ETernary(predicate, trueCase, falseCase)
+): expressionContent => T.ETernary(predicate, trueCase, falseCase)
 
-let eIdentifier = (name: string): expression => name->T.ESymbol
+let eIdentifier = (name: string): expressionContent => name->T.ESymbol
 
-// let eTypeIdentifier = (name: string): expression =>
+let eVoid: expressionContent = T.IEvVoid->T.EValue
-//   name->T.IEvTypeIdentifier->T.EValue
-
-let eVoid: expression = T.IEvVoid->T.EValue

packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_Lambda.res

@@ -1,60 +0,0 @@
-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: ["..."],
-}

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 {
+  switch expression.content {
   | EBlock(statements) =>
     `{${Js.Array2.map(statements, aValue => toString(aValue))->semicolonJoin}}`
   | EProgram(statements) => Js.Array2.map(statements, aValue => toString(aValue))->semicolonJoin
@@ -24,37 +24,23 @@ let rec toString = (expression: t) =>
     `${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_ErrorValue.errorToString(m)})`
+  | Error(m) => `Error(${Reducer_Peggy_Parse.toStringError(m)})`
   }
 
 let toStringResultOkless = codeResult =>
   switch codeResult {
   | Ok(a) => toString(a)
-  | Error(m) => `Error(${Reducer_ErrorValue.errorToString(m)})`
+  | Error(m) => `Error(${Reducer_Peggy_Parse.toStringError(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)
-  }

packages/squiggle-lang/src/rescript/Reducer/Reducer_FrameStack.res

@@ -0,0 +1,51 @@
+// This is called "frameStack" and not "callStack", because the last frame in errors is often not a function call.
+// A "frame" is a pair of a scope (function or top-level scope, currently stored as a string) and a location inside it.
+// See this comment to deconfuse about what a frame is: https://github.com/quantified-uncertainty/squiggle/pull/1172#issuecomment-1264115038
+type t = Reducer_T.frameStack
+
+module Frame = {
+  let toString = ({name, location}: Reducer_T.frame) =>
+    name ++
+    switch location {
+    | Some(location) =>
+      ` at line ${location.start.line->Js.Int.toString}, column ${location.start.column->Js.Int.toString}` // TODO - source id?
+    | None => ""
+    }
+
+  @genType
+  let getLocation = (t: Reducer_T.frame): option<Reducer_Peggy_Parse.location> => t.location
+
+  @genType
+  let getName = (t: Reducer_T.frame): string => t.name
+}
+
+let make = (): t => list{}
+
+let extend = (t: t, name: string, location: option<Reducer_Peggy_Parse.location>) =>
+  t->Belt.List.add({
+    name,
+    location,
+  })
+
+// this is useful for SyntaxErrors
+let makeSingleFrameStack = (location: Reducer_Peggy_Parse.location): t =>
+  make()->extend(Reducer_T.topFrameName, Some(location))
+
+// this includes the left offset because it's mostly used in SqError.toStringWithStackTrace
+let toString = (t: t) =>
+  t
+  ->Belt.List.map(s => "  " ++ s->Frame.toString ++ "\n")
+  ->Belt.List.toArray
+  ->Js.Array2.joinWith("")
+
+@genType
+let toFrameArray = (t: t): array<Reducer_T.frame> => t->Belt.List.toArray
+
+@genType
+let getTopFrame = (t: t): option<Reducer_T.frame> => t->Belt.List.head
+
+let isEmpty = (t: t): bool =>
+  switch t->Belt.List.head {
+  | Some(_) => true
+  | None => false
+  }

packages/squiggle-lang/src/rescript/Reducer/Reducer_Lambda.res

@@ -0,0 +1,95 @@
+type t = Reducer_T.lambdaValue
+
+// user-defined functions, i.e. `add2 = {|x, y| x + y}`, are built by this method
+let makeLambda = (
+  name: option<string>,
+  parameters: array<string>,
+  bindings: Reducer_T.bindings,
+  body: Reducer_T.expression,
+  location: Reducer_Peggy_Parse.location,
+): t => {
+  let lambda = (
+    arguments: array<Reducer_T.value>,
+    context: Reducer_T.context,
+    reducer: Reducer_T.reducerFn,
+  ) => {
+    let argsLength = arguments->E.A.length
+    let parametersLength = parameters->E.A.length
+    if argsLength !== parametersLength {
+      SqError.Message.REArityError(None, parametersLength, argsLength)->SqError.Message.throw
+    }
+
+    // create new bindings scope - technically not necessary, since bindings are immutable, but might help with debugging/new features in the future
+    let localBindings = bindings->Reducer_Bindings.extend
+
+    let localBindingsWithParameters = parameters->Belt.Array.reduceWithIndex(localBindings, (
+      currentBindings,
+      parameter,
+      index,
+    ) => {
+      currentBindings->Reducer_Bindings.set(parameter, arguments[index])
+    })
+
+    let lambdaContext: Reducer_T.context = {
+      bindings: localBindingsWithParameters, // based on bindings at the moment of lambda creation
+      environment: context.environment, // environment at the moment when lambda is called
+      frameStack: context.frameStack, // already extended in `doLambdaCall`
+      inFunction: context.inFunction, // already updated in `doLambdaCall`
+    }
+
+    let (value, _) = reducer(body, lambdaContext)
+    value
+  }
+
+  FnLambda({
+    // context: bindings,
+    name,
+    body: lambda,
+    parameters,
+    location,
+  })
+}
+
+// stdlib functions (everything in FunctionRegistry) are built by this method. Body is generated in SquiggleLibrary_StdLib.res
+let makeFFILambda = (name: string, body: Reducer_T.lambdaBody): t => FnBuiltin({
+  // Note: current bindings could be accidentally exposed here through context (compare with native lambda implementation above, where we override them with local bindings).
+  // But FunctionRegistry API is too limited for that to matter. Please take care not to violate that in the future by accident.
+  body,
+  name,
+})
+
+// this function doesn't scale to FunctionRegistry's polymorphic functions
+let parameters = (t: t): array<string> => {
+  switch t {
+  | FnLambda({parameters}) => parameters
+  | FnBuiltin(_) => ["..."]
+  }
+}
+
+let doLambdaCallFrom = (
+  t: t,
+  args: array<Reducer_T.value>,
+  context: Reducer_T.context,
+  reducer,
+  location: option<Reducer_Peggy_Parse.location>,
+) => {
+  let newContext = {
+    ...context,
+    frameStack: context.frameStack->Reducer_FrameStack.extend(
+      context->Reducer_Context.currentFunctionName,
+      location,
+    ),
+    inFunction: Some(t),
+  }
+
+  SqError.rethrowWithFrameStack(() => {
+    switch t {
+    | FnLambda({body}) => body(args, newContext, reducer)
+    | FnBuiltin({body}) => body(args, newContext, reducer)
+    }
+  }, newContext.frameStack)
+}
+
+let doLambdaCall = (t: t, args, context, reducer) => {
+  doLambdaCallFrom(t, args, context, reducer, None)
+}

packages/squiggle-lang/src/rescript/Reducer/Reducer_Lambda_T.res

@@ -0,0 +1,8 @@
+type t = Reducer_T.lambdaValue
+
+let name = (t: t): string => {
+  switch t {
+  | FnLambda({name}) => name->E.O2.default("<anonymous>")
+  | FnBuiltin({name}) => name
+  }
+}