Dear Perl experts,

I'm way too tired now to try this and would like to ask you for help. Not to implement - I'll try tomorrow again - but preferably some pointers. I'm sure this has been done before:

I need a subroutine that is given an arbitrary number of lists and returns the cartesian product of these lists - preserving the ordering. e.g.

# comb([qw(a b c)],[qw(1 2 3)],[qw(- + *)]);
# -> [[a,1,-],[a,1,+],[a,1,*],
#     [a,2,-],[a,2,+],[a,2,*],
#     [a,3,-],[a,3,+],[a,3,*],
#     [b,1,-],[b,1,+],[b,1,*],
#     [b,2,-],[b,2,+],[b,2,*],
#     [b,3,-],[b,3,+],[b,3,*],
#     [c,1,-],[c,1,+],[c,1,*],
#     [c,2,-],[c,2,+],[c,2,*],
#     [c,3,-],[c,3,+],[c,3,*]]
#

[download]

You get the idea. The problem for me is, that the number of lists given is variable and I simply don't get the required iteration/recursion to achieve that combinatorics.

Many thanks for any pointers.

Punymonk

In reply to 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.