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Re: Massive regexp search and replace

by grinder (Bishop)
on Feb 10, 2005 at 15:08 UTC ( #429761=note: print w/ replies, xml ) Need Help??


in reply to Massive regexp search and replace

Can anyone help me find an efficient implementation.

If the cost of a subroutine call is cheaper than scanning the list (which I suspect is the case), then you can assemble all the target patterns into one, perform a single match, and then dispatch to the sub that gives you what you want to substitute:

#! /usr/local/bin/perl -w use strict; use Regexp::Assemble; my $ra; my %dispatch = ( 'food' => sub { 'pizza' }, 'water' => sub { 'beer' }, 'like' => sub { 'enjoy' }, '(\d+)F' => sub { int(($ra->mvar(1) - 32 ) * 5/9 ) . 'C' }, ); $ra = Regexp::Assemble->new( track => 1 )->add( keys %dispatch ); while( <DATA> ) { while( $ra->match($_) ) { my $m = $ra->matched; s/$m/&{$dispatch{$m}}/e; } print; } __DATA__ I'd like a glass of water with my food, it's 92F in here!

... produces...

I'd enjoy a glass of beer with my pizza, it's 33C in here!

Generating the dispatch table from a data file is left as an exercise to the reader (but a pretty fun one, I might say).

- another intruder with the mooring in the heart of the Perl


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Re^2: Massive regexp search and replace
by albert.llorens (Initiate) on Feb 10, 2005 at 16:01 UTC
    Thanks grinder.

    I had already used module Regexp::Assemble for another quite similar script, and I had thought of using it with track=>1 for my replacement script. But I could not because my new script hanged whenever I created a Regexp::Assemble object with track=>1.

    The exact line in my code where the script hanged:
    my $Rpatt = Regexp::Assemble->new( chomp=>1, track=>1 )->add( keys(%PA +TTS) );
    Where %PATTS is a hash with elements of the form 'pattern->replacement'. Any idea why it hanged?
      Any idea why it hanged?

      Without seeing %PATTS, no idea. Maybe you have uncovered a bug! If you're interested in resolving the problem, I now have a mailing list for the module. If you care to join up we can maybe get to the bottom of the problem.

      - another intruder with the mooring in the heart of the Perl

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