calendar powered by Bloglendar

Chat with Andy (if online)
Live chat by Bold chat

News Feeds:
Atom 0.3
RSS 1.0
RSS 2.0
Comment Feed:
RSS 0.91
Subscribe Here:
Subscribe with Bloglines

The Hacker Emblem



Copyright (c) FOX
Google GMail

Monday, September 26, 2005

Y combinator in Javascript  

As you might know the fix point combinator of a function is another function that is left unchanged by further applications of the fix point combinator. This is also known as the Y combinator.

A function, often denoted Y, which computes a fixed point of any function it is given. Y is a function with the property that f(Y(f)) = Y(f) for all functions f.

In JavaScript, it is:

function Y(le) {
return function (f) {
return f(f);
}(function (f) {
return le(function (x) {
return f(f)(x);

With this, factorial can be defined as:

var factorial = Y(function (factorial) {
return function (n) {
return n <= 2 ? n : n * factorial(n - 1);

var number120 = factorial(5);

More info at The Little JavaScripter.

This page is powered by Blogger. Isn't yours? Weblog Commenting and Trackback by