# Z Combinator #

**Version:** *0.1.1*
**Master build:** [![Master branch build status][travis-master]][travis]
**Develop build:** [![Master branch build status][travis-develop]][travis]
This library provides a utility function to support the creation of self-referencing anonymous functions.
It can be installed in whichever way you prefer, but I recommend [NPM][npm]. The Z Combinator is the same, in principle, as the Y Combinator except it works in languages with applicative (eager) order of execution (arguments are evaluated before the function call) just like JavaScript. For more information about the Z Combinator please read Douglas Crockford's ["The Little JavaScripter"][little-js]. ### Basic usage ### ```js var z = require('z-combinator'); // Factorial var factorial = z(function(fn) { return function(n) { return 2 >= n ? n : n * fn(n - 1); } }); factorial(2) // => 2 factorial(3) // => 6 factorial(4) // => 24 factorial(5) // => 120 ``` ### Beware of infinite recursion! ### Just as you would with any other recursive function, make sure you include some sort of break condition. If you miss it out, the function will recur indefinitely. ```js var z = require('z-combinator'); z(function(fn) { return function(n) { return fn(n + 1); // <= Unconditional recursion }; })(0); // => Error: Maximum call stack exceeded z(function(fn) { return function(n) { return 100 <= n ? n : fn(n + 1); // <= Conditional recursion }; })(0); // => 100 ``` ### Contributing ### I accept contributions to the source via Pull Request, but passing unit tests must be included before it will be considered for merge. ```bash $ make install $ make tests ``` If you have [Vagrant][vagrant] installed, you can build the dev environment to assist development. The repository will be mounted in `/srv`. ```bash $ vagrant up $ vagrant ssh Welcome to Ubuntu 12.04 LTS (GNU/Linux 3.2.0-23-generic x86_64) $ cd /srv ``` ### License ### The content of this library is released under the **MIT License** by **Andrew Lawson**.
You can find a copy of this license at http://www.opensource.org/licenses/mit or in [`LICENSE`][license] [travis]: https://travis-ci.org/adlawson/z-combinator [travis-master]: https://travis-ci.org/adlawson/z-combinator.png?branch=master [travis-develop]: https://travis-ci.org/adlawson/z-combinator.png?branch=develop [npm]: https://npmjs.org/package/z-combinator [vagrant]: http://vagrantup.com [license]: /LICENSE [little-js]: http://www.crockford.com/javascript/little.html