From: piggybox <Sky.Yin@...>
Date: 2006-11-27T18:50:06+09:00
Subject: Re: ruby and list comprehension

I've always thought list comprehension is just a bunch of
map/filter/... transformation until I saw the following version of
permutation:

in Haskell:
permutation [] = [[]]
permutation xs = [x:ys | x <- xs, ys <- permutation (delete x xs)]

in Erlang:
permutation([]) -> [[]];
permutation(L)  -> [[H|T] || H <- L, T <- permutation(L--[H])].

really neat, isn't it?