Re: reg expr...

"Sarah Thompson" <sarah@telergy.com>
11 Sep 2002 23:22:36 -0400

          From comp.compilers

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From: "Sarah Thompson" <sarah@telergy.com>
Newsgroups: comp.compilers
Date: 11 Sep 2002 23:22:36 -0400
Organization: http://groups.google.com/
References: 02-09-040
Keywords: lex
Posted-Date: 11 Sep 2002 23:22:36 EDT

> I'm looking for a regular expression that say:
>
> match the line that does not begin with the string {s}
>
> now the way i see it ... if my s = "abc" then i will have to look for
> (a & b) or (ab & not c) or (abc & not wht_spc) ...
>
> but the longer the s the longer the reg expr ... is there another way to
> do this?


For the case where {s} is 'fruitbat', the regex:


      [^f][^r][^u][^i][^t][^b][^a][^t].*|.{0-7}


should work, assuming the whole input is one line. The first term will
match any line of 8 or more characters, where the first 8 characters
are not 'fruitbat'. The second term picks up the other possible valid
lines, which are any combination of up to 7 characters.


Using POSIX syntax for line start/end matching and assuming input
containing multiple lines, something like:


      ^([^f][^r][^u][^i][^t][^b][^a][^t].*|.{0-7})$


should do the trick.


Sarah


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