Hi Monks,

this one is certainly a little difficult/hairy/tricky and I'm aware, that there probably can't be a definitive answer. In fact, I had a hard time of even deciding whether to put this into Seekers or Meditations.

I'll need a function that will return either a "genericity" - or - "specifity" of a regular expression. The idea is, that according to a measure of "specifity", the following regular expressions are sorted from the most specific to the most generic:

1) \AHi\z
2) \AHi
3) Hi
4) \b(Hi(ya)?|Hello|Greetings)\b
5) (Hi(ya)?|Hello|Greetings)
6) .*

[download]

So in other words, a regular expression is more specific than another, if it "matches less" than that other rx. (well - and there's the problem - it is questionable if 4) isn't more specific than 3) )

Any creative ideas how to achieve this? Oh - yes and the computation of the "genericity/specifity" should be fast. The best I could come up so far was to dissect each regular expression with other regular expressions and adding/subtracting "weight" at the occurence of different metacharacters with very limited success so far.

So if anyone has a good idea or maybe a pointer to something similar that has been done before, I'd love to see that.

Bye
 PetaMem     All Perl:   MT, NLP, NLU

In reply to Analysis of Regular Expressions by PetaMem

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.