From: "David A. Black" <dblack@...>
Date: 2008-07-04T20:40:31+09:00
Subject: Re: pseudo-randomize an array in a consistent order

On Fri, 4 Jul 2008, Max Williams wrote:

> Here's my final version in case anyone's interested:
>
> class Array
>
>  def randomize!(seed=nil)
>    srand(seed) if seed
>    i = length - 1
>    while (i > 0)
>       #have to specify Kernel::rand to avoid method name clash
>       j = Kernel::rand(i)
>       # Swap self[i] and self[j]
>       tmp = self[i]
>       self[i] = self[j]
>       self[j] = tmp
>       i -= 1
>    end
>    #reset srand
>    srand if seed
>    self
>  end
>
>  def randomize(seed=nil)
>    self.dup.randomize!(seed)
>  end
>
> end

I don't think it randomizes very well.

>> 1000.times { puts "yes!" if [1,2].randomize == [1,2] }
=> 1000

> I encountered a puzzling gotcha with rand - it turns out that Rails
> monkey-patches Array with 'rand' (no arguments) which pulls out a random
> element.

I'd describe that as a gotcha with Rails :-)


David

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