This is possible by converting a regex into some sort of finite automaton and doing a traversal on it.

Perl would be my prefered choice in this though. The use of such would be great in creating examples in how regexes get processed.

This problem is a bit underspecified. For example, if you give me any sample of, say, 10 URLs

http://www.youtube.com/user/test1 http://www.youtube.com/user/test2 http://www.youtube.com/user/test3 http://www.youtube.com/user/test4 http://www.youtube.com/user/test5:
regex created: http://www.youtube.com/user/(.*)

http://be.apple.itunes.com/blabla/blabla/id/1543285432 http://us.apple.itunes.com/blabla/blabla/id/154328545 http://uk.apple.itunes.com/blabla/blabla/id/5532424342 http://be.apple.itunes.com/blabla/blabla/id/15432 http://be.apple.itunes.com/blabla/id/4324
regex created: http://(\d)+\.apple.itunes.com/blabla/blabla/id/(.*)

In reply to Re^2: Reverse regexp a regexp? by freakingwildchild
in thread Reverse regexp a regexp? by freakingwildchild

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.