I've got this subroutine which does a permutation. It works fine. I added a data structure to the program to account for a variable number of element pairs(eg. player1, player2). All of this works fine. But in the permute sub-routine a phrase is built and printed to screen. If there is ever an example where the 2nd element of a set comes before the 1st element(ie. player2 player1), the phrase is not output.

The variable that has the data structure of element sets is '$pairs'(a hash of arrays). When I call this routine I pass it 3 args: 2 arrayrefs, and the scalar hashref. Just before the 'unless' statement, $pairs is defined and houses all the right data. Inside the branch that is executed if the condition is met, $pairs is all of a sudden empty. 

sub permute
{
    my @items = @{ $_[0] };
    my @perms = @{ $_[1] };
    my $pairs = $_[2];    # here its defined
    unless (@items) {
        my $phrase = join( " ", @perms );
        print $pairs, "\n"; exit;   # here its empty all of sudden
        my $res = check_ord( $phrase, $pairs );
        if ( !( $res ) ) {
#           $ARGV[0] ? print FH $phrase. "\n" : print $phrase, "\n";
        }
    } else {
        my(@newitems,@newperms,$i);
        foreach $i (0 .. $#items) {
            @newitems = @items;
            @newperms = @perms;
            unshift(@newperms, splice(@newitems, $i, 1));
            permute([@newitems], [@newperms]);
        }
    }
}

[download]

Any ideas?

Amel - f.k.a. - kel

In reply to Defined or Undefined - That is the question. by dsb

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