From: Max Williams <toastkid.williams@...>
Date: 2008-07-04T20:09:04+09:00
Subject: Re: pseudo-randomize an array in a consistent order

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

j = rand(i)

was giving me a 'too many arguments' error, as it thought i was wanting 
Array::rand.  So, i just specify that i want Kernel::rand and it's fine.

thanks again
max
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