sub gen_seqs;
    sub gen_seqs {
        return [] if $_ [0] <= 0;
        my @s = gen_seqs $_ [0] - 1;
       (map {[0 => @$_]} @s), (map {[1 => @$_]} @s)
    }
[download]

Abigail

Why do you need both @seqs_0 and @seqs_1? They'll both hold the same thing, and you're dealing with them destructively. Unless I'm missing something, I'd think you could do

my @subseq = gen_seqs($n-1);
unshift @$seq, 0 foreach @subseq;
unshift @$seq, 1 foreach @subseq;
push @seqs, @subseq, @subseq;
[download]

Why do you need both @seqs_0 and @seqs_1? They'll both hold the same thing, and you're dealing with them destructively. Unless I'm missing something, I'd think you could do

my @subseq = gen_seqs($n-1);
unshift @$seq, 0 foreach @subseq;
unshift @$seq, 1 foreach @subseq;
push @seqs, @subseq, @subseq;
[download]

Hmm? The idea is to generate two copies of the (n-1)-sequences, prepend a 0 to everything in the first copy, and prepend a 1 to everything in the second copy. Unless I'm missing something (perhaps about $seq, which you don't declare here and which I don't use except in the code that I think you're replacing), you'll stuff a 0 onto each sequence in @subseq, then a 1 onto each sequence, and throw two copies of that into @seqs. Not the same thing.

I could easily be missing something, though. I'm in the middle of debugging some backtracking code right before a deadline, so I'm not thinking terribly clearly at the moment. :-) Thanks for taking the time to look it over.

--
F o x t r o t U n i f o r m
Found a typo in this node? /msg me
The hell with paco, vote for Erudil!

You build arrays of zeros and ones here, but usually I prefer strings. Here's an interesting way to build an iterator for all strings of length n, base b, given an appropriate b:

sub iterator {
  my($n, $b) = @_;
  my $limit = $b - 1;
  die "base out of range" unless $limit =~ /^\d$/;
  my $str;
  sub {
    return $str = "0" x $n unless defined $str;
    return $str =~ s/([^$limit])($limit*)$/($1+1)."0" x length($2)/e
      ? $str : undef;
  }
}

# Usage:
my $iterator = iterator(5, 2);
while (defined($next = $iterator->())) {
  print "next: $next\n";
}
[download]