in reply to Re^3: Perl regular expression for amino acid sequence
in thread Perl regular expression for amino acid sequence
There's a neat trick to get around the lookbehind-thinks-backreferences-are-variable-length problem: embed a lookahead in your lookbehind. It doesn't mind if you use backreferences inside the lookahead.
Caution: Contents may have been coded under pressure.
For the problem at hand, it would go like this
This was a trick someone posted some time ago, but it was over my head at the time. Now I get it./([QGYN]{2} # First two characters of the desired class (?: # Followed by the complex expression... # Look for a trio starting two characters back (?<=(?!(.)\2\2)..) [QGYN] # Then take another of the desired class ){1,4} # ...1 to 4 times )/gx
Caution: Contents may have been coded under pressure.
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Re: Lookbehind and backreferences
by BrowserUk (Patriarch) on Dec 02, 2004 at 02:19 UTC | |
Re: Lookbehind and backreferences
by seaver (Pilgrim) on Dec 02, 2004 at 15:59 UTC | |
by Roy Johnson (Monsignor) on Dec 02, 2004 at 16:23 UTC |
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