Catala examples

This repository contains examples of Catala programs. It is highly recommended to locate your own Catala programs in this directory, since programs in this directory will receive first-class support during the alpha and beta stage of the Catala programming language development.

Browse examples online »

List of examples

• allocations_familiales/: computation of the French family benefits, based on the Code de la sécurité sociale.
• aides_logement: computation of the French housing benefits, based on the Code de la construction et de l'habitation. This case study is the biggest and most ambitious for Catala so far.
• tutorial_<en/fr>/: Catala language tutorial for developers of tech-savvy lawyers. The tutorial is written like a piece of legislation that gets annotated by Catala snippets.
• us_tax_code/: contains the Catala formalization of several sections of the US Tax Code.

Building and running examples

Use Clerk (it comes installed alongside catala) to build and test your examples.

Note: For now, the OCaml, Javascript and Python artifacts that are used in https://github.com/CatalaLang/french-law are generated using dune rules instead, while Clerk is getting mature enough. See the examples in aides_logement/dune and allocations_familiales/dune.

Testing examples

Unit testing is important, and we encourage Catala developers to write lots of tests for their programs. Again, the Makefile system provides a way to collect tests into a regression test suite.

In order to enjoy the benefits of this system, we recommand that you create a tests/ directory in your examples directory, for instance foo/tests. Then, create a test file foo_tests.catala_en inside that directory.

Inside foo_tests.catala_en, declare one ore more test scopes. Then, you can provide the expected output for the interpretation of these scopes or the compilation of the whole program using the standard expected by clerk test by including catala-test-inline sections in your file.

Once your tests are written, then will automatically be added to the regression suite executed using:

clerk test

You can isolate a part of the regression suite by invoking:

clerk test foo/tests/foo_tests.catala_en

Adding an example

This section describes what to do to setup a working directory for a new Catala example, as well as the development cycle. Let us suppose that you want to create a new example named foo.

First, follow the instructions to install the Catala compiler. You can also set up the syntax highlighting for your editor.

Then, create the directory examples/foo. In there, create a master source file foo.catala_en (or foo.catala_fr, etc. depending on your language) that will be the root of your Catala program. You can then start programming in foo.catala_en, or split up your example into multiple files. In the later case, foo.catala_en must only contain something like this:

# Master file

> Include: bar.catala_en

where examples/bar.catala_en is another source file containing code for your example. Make sure you start by including some content in the source files, like

Hello, world!