Re: [FWP] Perl Card Games

[Bennett Todd <bet@newritz.mordor.net>]

1999-08-03-21:18:18 Chip Turner:
> @cards = (0 .. 51); # or any number of them
> $passes = 1; # one pass should be sufficient for all but the most paranoid
> $cards[$_ % @cards] = $cards[rand(@cards) % @cards] foreach 0 .. ($passes * @cards - 1);

Cool! But not quite correct, I don't think; in your assignment you are
generally overwriting one card with another, so in just one pass when I just
tested that squashed down to 20 distict cards, with many duplicates. You need
a swap if you want to do it in-place. And rather than leaving the domain of
the swap open, I'd rather have it be "from the remainder". Hence my preferred
shuffling copy, or the swap version:

  @cards = (0 .. 30);
  for my $i (0 .. $#cards-1) {
  	@cards[$i, $_] = @cards[$_, $i] for $i + rand(@cards-$i);
  }

-Bennett

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