catala/README.md

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Catala is a domain-specific language for deriving
faithful-by-construction algorithms from legislative texts. To learn quickly
about the language and its features, you can jump right to the official
[Catala tutorial](https://catala-lang.org/en/examples/tutorial).
You can join the Catala community on [Zulip][chat-link]!

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<br>

<details>
  <summary>Table of Contents</summary>

<!-- vim-markdown-toc GitLab -->

* [Concepts](#concepts)
* [Getting started](#getting-started)
* [Building and installation](#building-and-installation)
* [Usage](#usage)
  * [Catala](#catala)
  * [Clerk](#clerk)
* [Documentation](#documentation)
  * [Syntax cheat sheet](#syntax-cheat-sheet)
  * [Formal semantics](#formal-semantics)
  * [Compiler documentation](#compiler-documentation)
* [Examples](#examples)
* [API](#api)
* [Contributing](#contributing)
* [Test suite](#test-suite)
* [License](#license)
* [Limitations and disclaimer](#limitations-and-disclaimer)
* [Pierre Catala](#pierre-catala)

<!-- vim-markdown-toc -->

</details>

## Concepts

Catala is a programming language adapted for socio-fiscal legislative literate
programming. By annotating each line of the legislative text with its meaning
in terms of code, one can derive an implementation of complex socio-fiscal
mechanisms that enjoys a high level of assurance regarding the code-law
faithfulness.

Concretely, you have to first gather all the laws, executive orders, previous
cases, etc. that contain information about the socio-fiscal mechanism that
you want to implement. Then, you can proceed to annotate the text article by
article, in your favorite text editor :

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<img src="https://github.com/CatalaLang/catala/raw/master/doc/images/ScreenShotVSCode.png" alt="Screenshot" height="350"/>
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Once your code is complete and tested, you can use the Catala
compiler to produce a lawyer-readable PDF version of your
implementation. The Catala language has been specially designed
in collaboration with law professionals to ensure that the code
can be reviewed and certified correct by the domain experts, which
are in this case lawyers and not programmers.

<div align="center">
<img src="https://github.com/CatalaLang/catala/raw/master/doc/images/CatalaScreenShot.png" alt="Screenshot" height="350"/>
</div>

The Catala language is special because its logical structure mimics
the logical structure of the law. Indeed, the core concept of
"definition-under-conditions" that builds on default logic has been formalized
by Professor Sarah Lawsky in her article
[A Logic for Statutes](https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3088206).
The Catala language is the only programming language to our knowledge that
embeds default logic as a first-class feature, which is why it is the only
language perfectly adapted to literate legislative programming.

## Getting started

To get started, the best place is the [tutorial](https://catala-lang.org/en/examples/tutorial)
of the language. A [French version](https://catala-lang.org/fr/examples/tutoriel)
is also available but might be out of sync with the latest language features.

> **Note:** bleeding-edge version
>
> If you are interested in the latest development version, pre-built artifacts
> including binaries and API documentation can be found at
> https://catalalang.github.io/catala

## Building and installation

Catala is available as an [opam package](https://opam.ocaml.org/packages/catala/)!
If opam is installed on your machine, simply execute:

    opam install catala

To get the cutting-edge, latest version of Catala, you
can also do

    opam pin add catala --dev-repo

However, if you wish to get the latest developments of the compiler, you probably
want to compile it from the sources of this repository or use nix. For that, see
[the dedicated readme](INSTALL.md).

## Usage

### Catala

Use `catala --help` if you have installed it to get more information about the command line
options available. The man page is also [available online](https://catala-lang.org/en/doc/catala).
To get the development version of the help, run `make help_catala`
after `make build`. The `catala` binary corresponds to the Catala compiler.

The top-level `Makefile` contains a lot of useful targets to run. To display
them, use

        make help

### Plugin backends

While the compiler has some builtin backends for Catala (Python, Ocaml, etc.),
it is also possible to add a custom backend to the Catala compiler without
having to modify its source code. This plugin solution relies on dynamic
linking: see [the dedicated README](compiler/plugins/README.md).

### Clerk

Use `clerk --help` if you have installed it to get more information about the command line
options available. To get the development version of the help, run `make help_clerk`
after `make build`. The `clerk` binary corresponds to the Catala build system,
responsible for testing among other things.

To get more information about Clerk, see [the dedicated readme](https://github.com/CatalaLang/catala/tree/master/build_system/README.md)

## Documentation

### Syntax cheat sheet

A complete and handy reference of the Catala syntax can be found in the
[cheat sheet](doc/syntax/syntax.pdf) (for French and English versions
of the syntax).

### Formal semantics

To audit the formal proof of the partial certification of the Catala compiler,
see [the dedicated readme](doc/formalization/README.md).

### Compiler documentation

The compiler documentation is auto-generated from its source code using
`dune` and `odoc`. Use

    make doc

to generate the documentation, then open the `doc/odoc.html` file in any browser.
The documentation is also accessible [online](https://catala-lang.org/ocaml_docs/).

## Examples

To explore the different programs written in Catala, see
[the dedicated readme](examples/README.md).

## API

To know how to use the code generated by the Catala compiler in your favorite
programming language, head to the [readme of the French law library](french_law/README.md)

## Contributing

To know how you can contribute to the project, see
[the dedicated readme](CONTRIBUTING.md).

## Test suite

To know how to run or improve the Catala reference test suite,
see [the dedicated readme](tests/README.md).

## License

The compiler and all the code contained in this repository is released under
the [Apache license (version 2)](LICENSE.txt) unless another license is explicited
for a sub-directory.

## Limitations and disclaimer

Catala is a research project from Inria, the French National
Research Institute for Computer Science. The compiler is yet
unstable and lacks some of its features.

## Pierre Catala

The language is named after Pierre Catala, a professor of law who
pionneered the French legaltech by creating a computer database of law cases,
Juris-Data. The research group that he led in the late 1960s, the
Centre d’études et de traitement de l’information juridique (CETIJ),
has also influenced the creation by state conselor Lucien Mehl of the
Centre de recherches et développement en informatique juridique (CENIJ),
which eventually transformed into the entity managing the LegiFrance website,
acting as the public service of legislative documentation.

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