JuDePom / algooo

Language designed to introduce algorithmics to French CS students, compiles to JS

Compiler for a programming language designed to introduce French budding programmers to algorithmics. Meant to be integrated within a web app.

Live demo: http://www.algooo.fr

(may take a couple seconds to load at first, I use a very cheap hosting plan)

Backstory

I attended a CS program at IUT Nancy-Charlemagne, France which uses an in-house "pseudo-code" programming language to teach the basics of algorithmics. It's a simplified form of Pascal with French keywords. For the final year's "big" project, I presented a compiler for this programming language.

Why bother writing a compiler from scratch when there are compiler compilers these days? For fun! And to learn how compilers work. It's not meant to be a super serious project. I learned a ton of stuff working on it -- both about general computer science and about Python and JavaScript.

Technical overview

• Compiler written in Python 3

• Compiles "LDA" to JavaScript (LDA stands for Langage de Description d'Algorithmes, i.e. algorithm description language. This was the 'working title' during development)

• Meant to be run as a web app:

  1. enter your code in the browser

  2. the compiler does its thing on the server side and responds with compiled JavaScript

  3. your browser can execute the JavaScript

• Also works just fine on the command line (read caveats below)

• The programming language is in French, but the source code is in English, and the keywords can be easily translated to pretty much any human language (see kw.py)

Getting a taste of the language

As mentioned before, it's basically simplified Pascal with French keywords and a few tweaks.

A couple runnable examples are available at www.algooo.fr (look for the pane that says 'Exemples' on the left).

You can also have a look around the snippets directory, which contains hundreds of small snippets of the language. The snippets are used as a compiler torture test within the test suite (test_snippets.py). But, each snippet is self-contained. Many snippets are correct LDA and may be compiled -- but many other snippets explicitly test the compiler's proper response to syntax or semantic errors.

Standalone JavaScript shell (SpiderMonkey)

You will need a standalone JavaScript shell to run all the unit tests and execute the resulting JS from the command line. During development, Mozilla SpiderMonkey (aka jsshell) was used.

For best results, SpiderMonkey 27+, is recommended. Versions earlier than 27 may work, albeit with poor Unicode support.

Download a binary for your architecture there (scroll down and look for jsshell): https://ftp.mozilla.org/pub/mozilla.org/firefox/nightly/latest-trunk/

Command line usage

usage: ldac.py [-h] [--format FORMAT] [--output-file OUTPUT_FILE]
			   [--no-output] [--ignore-case] [--execute] INPUT_FILE

Parameter	Description
-h	Get help
--format FORMAT	Output format. Can be js (JavaScript, default) or lda (re-formatted LDA).
--no-output	Only checks syntactic and semantic correctness, does not output any code.
--ignore-case	Ignore case in identifiers and keywords.
--execute	Attempt to run the program with a JS runtime if no errors are found