squiggle/packages/squiggle-lang/README.md

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# Squiggle language

_An estimation language_

# Use the `npm` package

For instance, in a javascript project, you can

```sh
yarn add @quri/squiggle-lang
```

The `@quri/squiggle-lang` package exports a single function, `run`, which given
a string of Squiggle code, will execute the code and return any exports and the
environment created from the squiggle code.

```js
import { run } from "@quri/squiggle-lang";
run(
  "normal(0, 1) * SampleSet.fromList([-3, 2,-1,1,2,3,3,3,4,9])"
).value.value.toSparkline().value;
```

**However, for most use cases you'll prefer to use our [library of react components](https://www.npmjs.com/package/@quri/squiggle-components)**, and let your app transitively depend on `@quri/squiggle-lang`.

`run` has two optional arguments. The first optional argument allows you to set
sampling settings for Squiggle when representing distributions. The second optional
argument allows you to pass an environment previously created by another `run`
call. Passing this environment will mean that all previously declared variables
in the previous environment will be made available.

The return type of `run` is a bit complicated, and comes from auto generated `js`
code that comes from rescript. We highly recommend using typescript when using
this library to help navigate the return type.

# Build for development

We assume that you ran `yarn` at the monorepo level.

```sh
yarn build
```

`yarn bundle` is needed for a deployment.

Other:

```sh
yarn start  # listens to files and recompiles at every mutation
yarn test

# where o := open in osx and o := xdg-open in linux,
yarn coverage:rescript; o _coverage/index.html  # produces coverage report and opens it in browser
```

# Distributing this package or using this package from other monorepo packages

As it says in the other `packages/*/README.md`s, building this package is an essential step of building other packages.

# Information

Squiggle is a language for representing probability distributions, as well as functions that return probability distributions. Its original intended use is for improving epistemics around EA decisions.

This package, `@quri/squiggle-lang`, contains the core language of squiggle. The main feature revolves around evaluating squiggle expressions. Currently the package only exports a single function, named "run", which from a squiggle string returns an object representing the result of the evaluation.

If using this package for tests or as a dependency, typescript typings are available and recommended to be used.

This package is mainly written in [ReScript](https://rescript-lang.org/), but has a typescript interface.

ReScript has an interesting philosophy of not providing much in the way of effective build tools. Every ReScript file is compiled into `.bs.js` and `.gen.ts` files with the same name and same location, and then you can use these files in other `.js` files to create your program. To generate these files to build the package, you run `yarn build`.

`.gen.ts` files are created by the [`@genType`](https://rescript-lang.org/docs/gentype/latest/getting-started) decorator, which creates typescript typings for needed parts of the codebase so that they can be easily used in typescript. These .gen.ts files reference the .bs.js files generated by rescript.