Re: Non- recursive permutation of arrays.

[ariels]

Or, you could just count up to the product of the array sizes, and use the count to compute the offsets into the arrays (I think a note described this, but no code). If you have lists of lengths l₁,...,l_k, think of the numbers 0..(l₁*...*l_k-1). You want to convert them to a variable-base number system, where the first digit can be 0..l₁-1, the second digit can be 0..l₂-1,...

#!/usr/local/bin/perl -w
use strict;

my @aoa = (
       [('a'..'f')],
       [('A'..'C')],
       [(1..2)],
      );


my $iter = make_permutator(@aoa);


while (my @els = $iter->() ){
  print "@els\n";
}


# ariels' code from here
sub make_permutator {
  use integer;
  my @idx_link = (0, @_);
  return sub {
    my $idx = $idx_link[0]++;
    my @ret;
    for my $i (1..$#idx_link) {
      push @ret, $idx_link[$i][$idx % @{$idx_link[$i]}];
      $idx /= @{$idx_link[$i]};
    }
    return $idx ? () : @ret;
  }
}

[shotgunefx]

Interesting take. That way solution wouldn't have occured to me. I do think it's a bit more obfu though. I had to stare at it for a minute (Maybe just me though!). The best thing (IMHO) about Perl is how many different ways you can accomplish a single goal.

-Lee

"To be civilized is to deny one's nature."