RE: Randomize an array

[Adam]

I recommend the Fisher-Yates Shuffle. See my node on the topic.

# The Fisher-Yates Shuffle 
sub Shuffle
{
    my $arrayref = shift;
    my $index = @$arrayref;
    while ( $index-- ) 
    {
        my $newloc = int rand (1+$i);
        # next if $index == $newloc; # Not needed in Perl.
        @$arrayref[$index, $newloc] = @$arrayref[$newloc, $index];
    }
}

The line I commented out is part of the Fisher-Yates Shuffle, but its a waste of time in Perl, since the swap is done correctly. (If it were an XOR swap then you would want the next in there)

[Anonymous Monk]

That code has an error and it doesn't actually randomize. Here's the correct version:

# The Fisher-Yates Shuffle 
sub Shuffle
{
    my $arrayref = shift;
    my $index = @$arrayref;
    while ( $index-- ) 
    {
        my $newloc = int rand (1+$index);
        # next if $index == $newloc; # Not needed in Perl.
        @$arrayref[$index, $newloc] = @$arrayref[$newloc, $index];
    }
}