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Re^3: Bug in script, regex help req extreme urgent

by Athanasius (Monsignor)
on Mar 10, 2013 at 05:48 UTC ( #1022646=note: print w/ replies, xml ) Need Help??


in reply to Re^2: Bug in script, regex help req extreme urgent
in thread Bug in script, regex help req extreme urgent

Tip #9 from the Basic debugging checklist:

Demystify regular expressions by installing and using the CPAN module YAPE::Regex::Explain

So:

#! perl use strict; use warnings; use YAPE::Regex::Explain; my $re = qr/(?<=module )$ARGV[2].*?([\\(;])/; print YAPE::Regex::Explain->new($re)->explain();

Output:

15:40 >perl 566_SoPW.pl FILE OLD NEW The regular expression: (?-imsx:(?<=module )NEW.*?([\\(;])) matches as follows: NODE EXPLANATION ---------------------------------------------------------------------- (?-imsx: group, but do not capture (case-sensitive) (with ^ and $ matching normally) (with . not matching \n) (matching whitespace and # normally): ---------------------------------------------------------------------- (?<= look behind to see if there is: ---------------------------------------------------------------------- module 'module ' ---------------------------------------------------------------------- ) end of look-behind ---------------------------------------------------------------------- NEW 'NEW' ---------------------------------------------------------------------- .*? any character except \n (0 or more times (matching the least amount possible)) ---------------------------------------------------------------------- ( group and capture to \1: ---------------------------------------------------------------------- [\\(;] any character of: '\\', '(', ';' ---------------------------------------------------------------------- ) end of \1 ---------------------------------------------------------------------- ) end of grouping ---------------------------------------------------------------------- 15:40 >

See also perlretut and perlre.

Hope that helps,

Athanasius <°(((><contra mundum Iustus alius egestas vitae, eros Piratica,


Comment on Re^3: Bug in script, regex help req extreme urgent
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Re^4: Bug in script, regex help req extreme urgent
by sid.verycool (Novice) on Mar 10, 2013 at 07:22 UTC
    ohk... i didnt knew about this feature that explains like this. Another important point i wish to make, I want to ignore // lines. Suppose somebody writes something like // module OLD(Y, A, B); would my $string not match and make script behavior wrong?? thats why i was trying to give ^module (WHICH MAKE SURE THAT ITS NOT A COMMENT). WHITESPACE AND TABS ARE OK BUT NO // BEFORE matching expression
      next if m{\A//}
      J -
Re^4: Bug in script, regex help req extreme urgent
by sid.verycool (Novice) on Mar 21, 2013 at 03:42 UTC
    It solves my issue but fails in the scenario when i have module this is in between OLD(A, B, Y); , i even want my script to change it to, module this is in between NEW(A, B, Y); hence i tried doing this (?<=module .*)$ARGV2.*?(\\(;)"; which doesnt work and shell says Variable length lookbehind not implemented in regex; marked by <-- HERE in m/(?<=module .*)NEW.*?(\(;) <-- HERE / at script.pl line 23.. How can i implement this?

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