Algorithm::Loops's NestedLoops seems ideal for this task.
use Algorithm::Loops qw( NestedLoops ); sub comb { my @rv; NestedLoops(\@_, sub { push(@rv, [ @_ ]); }); return \@rv; }

Test harness:

my $comb = comb([qw(a b c)],[qw(1 2 3)],[qw(- + *)]); require Data::Dumper; print(Data::Dumper::Dumper( comb([qw(a b c)],[qw(1 2 3)],[qw(- + *)]) )); print(scalar(@$comb), "\n"); # 27

Update: What follows is a solution that doesn't require an external module. Neither it nor NestedLoops are recursive. Since they're not recursive, they're probably faster, more memory efficient, and you can use a callback instead of building the result in memory. You could even convert the code below into an iterator.

sub comb { my @idx = map { 0 } @_; my @max = map { $#$_ } @_; my @rv; for (;;) { push(@rv, [ map { $_[$_][$idx[$_]] } 0..$#idx ]); my $i = 0; for (;;) { $idx[$i]++; last if $idx[$i] <= $max[$i]; $idx[$i] = 0; $i++; return \@rv if $i == @idx; } } }

In reply to Re: cartesian product preserving order by ikegami
in thread cartesian product preserving order by Anonymous Monk

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":



  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.