From: "Brian Schröder" <ruby.brian@...>
Date: 2005-12-08T00:51:55+09:00
Subject: Re: Shuffling an array, sort_by{rand}'s bias (was Re: need some Ruby magic)

On 07/12/05, Michael Ulm <michael.ulm@isis-papyrus.com> wrote:
> hmassa@gmail.com wrote:
>
> > Why not
> >  a.dup.sort { 2*rand(12345) <=> 12345 }
> >
> > ? that way, we'd have NO colisions ever.
> >
>
> What you have posted does not avoid collisions.
> You probably mean something like
>
> a.sort {2*rand(12345) <=> 2 * rand(12345) + 1}
>
> [snip]
>

and then he should do us a favour and write
> a.sort { [-1, 1][rand(2)] }
instead, which gives the same skewed results but at least does not do
it as complicated.

Brian


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