I think I like LanX's grep/unpack approach best
May I ask why?

Well, I did only say I thought I liked it best :)

My practice in dealing with certain SoPW queries, regex-related ones in particular, is to try to formulate an answer before looking at any of the responses, then post what I have if it seems it might bring something to the table.

In quickly reading through the replies already posted before posting my own, it seemed that rjt's was closest to mine in matching to row-groups, then to a repeat within a row. (Although rjt's solution finds the rightmost repeat in a string, and you would presumably work leftward from there to pick up the others; my understanding is that you want all repeats from the string. My approach finds the leftmost repeat first, then continues working to the right.) What my approach added, it seemed to me, was a way within the regex to "re-synchronize" to a row boundary before looking for the next repeat to capture.

As I say, I only briefly glanced at the various replies before posting my own, and did no benchmarking. I was beguiled by the simplicity of some of the other replies and by the fact that I've found such approaches to be quite efficient in some other cases. I failed to notice that rjt had already done some benchmarking and found his or her regex approach to be significantly faster.

And that's the point: benchmarking tells the tale. No matter if an alternate solution is simpler, more elegant or maintainable (whatever those words really mean), if you have a need for speed and a solution's not fast enough, it's unuseable. Period.

So good luck in your quest, and I hope your experience of the Monastery has been and will continue to be productive. And please consider registering: it just makes things a bunch simpler.

In reply to Re^3: Regex matching on grid alignment by AnomalousMonk
in thread Regex matching on grid alignment 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.