From: Reinder Verlinde <reinder@...>
Date: 2005-12-04T02:32:32+09:00
Subject: Re: need some Ruby magic

In article <dd3f270e4d20842e121bb970bc9a8386@ruby-forum.com>,
 Jim Weirich <jim-keyword-rforum.c88827@weirichhouse.org> wrote:

> hammed wrote:
> > I'd like to sort collections randomly. This is what I tried first:
> > 
> > my_array.sort { |a,b| rand(2) }
> 
> my_array.sort_by { rand }

A quick test seems to indicate that this works with the ruby 1.8.2 
implementation on my Mac. However, there is no guarantee that this call 
will select each of the n! permutations with equal probability.

Whether it does will depend on the exact algorithm used by 'sort'. For 
instance, if sort uses the (inefficient for large arrays) bubble sort, 
the last key will end up staying there in half the cases.

Reinder