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From: lfk@athena.mit.edu (Lee F Kolakowski)
Newsgroups: comp.lang.perl
Subject: FSM's for large regex's in Perl or Awk
Message-ID: <1990Jul5.225930.13089@athena.mit.edu>
Date: 5 Jul 90 22:58:51 GMT
Sender: news@athena.mit.edu (News system)
Distribution: comp
Organization: Mass. Inst. of Tech., Dept. of Chemistry
Lines: 62



Hello out there in the land of perls.

I am thinking of moving an application from awk to perl, but wonder
what kind of speed up is possible and maybe of I am make a
pseudo-finite state machine out of problem.

I have a file with 350 regexs, which is expected to grow to 500 or
more by years end.

I want to search all of these on the input line. Currently, I read the
regexs into an array, and loop through all the regexs doing a match
each time. If it matches (I know where from the RSTART var), I cut off
the input up to that point and try match again.

so my code looks like this:

{
  if (FILENAME == "regex file") {
    accession[NR] = $1 ; regex[NR] = $2; name[NR] = $3; regex_num = NR;
  }
  else { 
    n = length($0)
    for (i = 1; i <= regex_num ; i++ ) {
      if (match($0, regex[i])) {

#	if it matches do stuff, then cut off the 
#	begining of string up to match and try again

	while (match(new,regex[i])) {

#	do some of the same stuff above

	}
      }
    }
  }
}


So the question is can I build a fsm using perl for this kind of
thing??

Wondering....


--

Frank Kolakowski 

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|lfk@athena.mit.edu                     ||      Lee F. Kolakowski    |
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