use Perl

• three regexen (Score:2)

  by wickline (135)

  > Changing my $person to
  >    qr/[\x08\x09](G[A-Z]{7})/
  > or
  >    qr/[\x08\x09](S[A-Z]{7})/
  > gives me a bunch of different records. But why would
  >    (S[A-Z]{7})
  > give different results than
  >    ([A-Z]{8})
  > ?. I'm stumped.

  I'm not sure if I'm misreading this, but it looks like you have three different regular expressions there:

      qr/  G [A-Z]{7}  /x
      qr/  S [A-Z]{7}  /x
      qr/   
  • Re:three regexen (Score:2)

    by gav (2710)

    > I would expect the three of them to match different values. The first one matches eight-letter uc words starting with 'G'. The second matches eight letter uc words starting with 'S'. The final regex matches eight letter uc words starting with any letter.
    
    Sorry for not being clear. I'd expect /S[A-Z]{7}/ to be a subset of the matches from /[A-Z]{8}/ but instead the latter isn't returning some of the results the former does.
    • Re:three regexen (Score:1)

      by n1vux (1492) on 2004.10.18 10:08 (#35283) Homepage Journal

      Glad to see /x modifier there. /S[A-Z]{7}/ should be a subset of /[A-Z]{7}/, in particular the subset /(?=S)[A-Z]{7}/. If it isn't, it could be a bug in the backtracking logic ... or an issue with binmode?
      
      If there is any possibility of accented 'national' characters (which there always is in unconstrained data) '\w' is much preferred to [A-Za-z] or [A-Z]/i.
      
      I'd worry that some 'persons' might actually be shorter than 8 chars, or have spaces or lower case in some systems. (van Helsing etc)
      
      What strings(1) shows you isn't quite what Perl sees. Try xd(1) or od(1) to see details. If on Windows (or VMS?) set binmode(3) on your filehandle. (For portability, set binmode anytime reading binary data.)
      
      good luck, we'll be interested to hear what the results are.
      

      --
      Bill
      # I had a sig when sigs were cool
      use Sig;

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