contracts.coffee is a dialect of CoffeeScript with contract support.

Contracts allow you to write powerful runtime assertions about your code. Like types but less painful, like assert but more useful.

square :: (Num) -> Num
square = (x) -> x * x
# throws a run-time error
square "a string"   

Documentation, usage, and more examples: https://disnetdev.com/contracts.coffee/

Note: I am no longer actively maintaining contracts.coffee. Check out contracts.js instead which has great contracts.coffee inspired syntax thanks to sweet.js macros.

Install via npm:

npm install -g contracts.coffee

Use the compiler:

coffee -c --contracts /path/to/script.coffee

An alternative to using the --contracts flag is setting this env variable:

export CONTRACTS_COFFEE_ENABLED=1

If you are running in the browser then you'll need to load the contracts library (found in lib/contracts/contracts.js)

<script type="text/javascript" src="contracts.js"></script>

There is also experimental support for require.js. See here for an example.

If you are running in node.js then you'll need to install the contracts.js package

npm install contracts.js

Note that contracts.coffee requires some pretty new features of JavaScript (Proxies in particular) so it currently only works on Firefox 4+, node.js 0.8.0+, and recent versions of Chrome (though you'll need to enable the experimental JavaScript flag in about:flags).

• 0.3.2 (September 5, 2012)
  • disabling contracts for arrays (see issue 54)
  • various bug fixes
• 0.3.1 (July 15th, 2012)
  • support for stable node.js (v0.8.0+)
  • some bug fixes
• 0.3.0 (March 15th, 2012)
  • change to dependent function contracts
  • various contracts.coffee bug fixes: #27, #41, #33, #31,
  • various contracts.js bug fixes: #9, #8, #7, #6, #5, #4
  • experimental support for require.js (see here for example use)
  • based off CoffeeScript 1.3.1
• 0.2.0 (January 4th, 2012)
  • removed .use(), now using Contracts.exports and Contracts.use
  • various bug fixes
  • based off CoffeeScript 1.2.0
• 0.1.0 (August 29th, 2011)
  • initial release
  • based off CoffeeScript 1.1.2