From: Uwe Schmitt <schmitt@...>
Date: 2005-12-06T23:32:34+09:00
Subject: Re: Shuffling an array, sort_by{rand}'s bias (was Re: need some Ruby

|| 
|| On Tue, Dec 06, 2005 at 07:32:34PM +0900, Uwe Schmitt wrote:
|| > Hi, I'm new to ruby, but I use Python for some years now.
|| > So I suggest the following 'pythonic' solution ;-)
|| [...]
|| > Is there a shorter or more elegant way to do this 
|| > 'decorate-sort-undecorate' in ruby ?
|| 
|| arr.sort_by{rand}

that is not equivalent to my solution.
the python equivalent to yours is

  arr.sort(key = lambda x: random())

|| 
|| > In Python it is quite easy by using list comprehensions...
|| What does that look like in Python? 

from random import random

def shuffle(a):
    b = [ (random(), i) for i in a]
    b.sort()
    return [ x[1] for x in b ]

print shuffle(range(10))

|| Is it shorter than the above one? }:-)
|| 
|| -- 
|| Mauricio Fernandez

greetings, Uwe


||