Re^5: Perlre interpretation required (perfect dequote regex)

With a bit of thought, it is quite possible to write an unbreakable regex de-quoter:

#!/usr/bin/perl -wnl
use strict;
print;
print join ' / ', map qq["$_"], m[\G (
        ' (?: \\ . | '' | [^'] ) + '
        |
        " (?: \\ . | "" | [^"] ) + "
        |
        (?: \\ . | [^'"] ) + 
) ]gx;
print "";
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It will handle even the edge cases yours breaks on. Using the (?{}) stuff to remove the redundancy is a nice idea, but for this case isn't the best solution.

sub make_dequote_rx {
    my @char = map quotemeta, @_;
    my $chars = join '', @char;
    my $rx = join(
        ' | ',
        map(qq[$_ (?: \\\\ . | $_$_ | [^$_] ) + $_], @char),
        qq[(?: \\\\ . | [^$chars] ) +],
    );
    return qr/\G ( $rx )/x;
}

my $dequote = make_dequote_rx qw(' ");
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Update: Doubled the backslashes in the second piece of code.

Makeshifts last the longest.

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Re: Re^5: Perlre interpretation required by BrowserUk (Patriarch) on May 04, 2003 at 09:43 UTC
Sorry Aristotle, but this is far from "unbreakable". In fact it doesn't even compile? You can't apply the /g modifier to qr//. Your version Read more... (3 kB) Output Read more... (4 kB)	[reply] [d/l] [select]
Re^7: Perlre interpretation required (remember kids: test all code..) by Aristotle (Chancellor) on May 04, 2003 at 13:35 UTC
Have you tried the first snippet? It is unbreakable. I didn't test the second though, sigh. I forgot that I'm using the doublequote-like op to put together a regex, so I need to double the backslash both for the regex as well as for the doublequotes, meaning I need four backslashes to begin with in order to get one literal one in the end. Let me fix that.. Makeshifts last the longest.	[reply]
Re: Re^7: Perlre interpretation required (remember kids: test all code..) by BrowserUk (Patriarch) on May 04, 2003 at 14:19 UTC
I guess I must be using it wrong, or the two routines aren't meant to acheive the same thing. As-is, yours does find and match on the quoted sections and handled the embedded quotes ok -- although it does leave the leading and trailing quotes in place -- but it also matches on the unquoted sections? I get the impression that we are both acheiving our goals adequately, they are just different goals:) Testcode Read more... (3 kB) Results Read more... (4 kB) Examine what is said, not who speaks. "Efficiency is intelligent laziness." -David Dunham "When I'm working on a problem, I never think about beauty. I think only how to solve the problem. But when I have finished, if the solution is not beautiful, I know it is wrong." -Richard Buckminster Fuller	[reply] [d/l] [select]
Re^9: Perlre interpretation required (my goals) by Aristotle (Chancellor) on May 04, 2003 at 15:35 UTC