How about the following - at least it looks symmetric.
$str =~ s{<td.*?>\K(.+?)\L</td>}{htmlify()}egx;
\L would perform a function similar to \K, only forward looking
On Thu, 2007-08-16 at 01:13 +0300, Yuval Yaari wrote:
> Peter Gordon wrote:
> > Wouldn't it be cute and much more intuitive if we could write this?
> >
> > s!<td.*?>(.*?)</td>!$1 =~ s/\s/ /g!eg
> >
>
> Yes. It wouldn't.
>
> These variables are read-only for very good reasons, y'know :-)
> Also notice the regex you just wrote doesn't do what you originally
> asked for.
> Assuming you wouldn't get errors for modifying a read-only variable,
> you're completely deleting <td> and </td>.
>
> I hope you don't mean you want the current behaviour that we all know
> and love to "match-but-do-not-replace-anything-that's-not-grouped" :-)
>
> So basically we:
> - *Have* to tell the engine what we want to "match-but-not-replace", as
> opposed to the current "match-and-replace"
> - *Really* want $1 to be read-only (think of you debugging experience
> when some function somewhere modifies $1 :))
>
> The cleanest solution would probably be (works starting from perl 5.9.5):
>
> $str =~ s{<td.*?> # variable-length look-behind :)
> \K # tells Perl to "keep" that <td>
> (.+?) # text that we want to s///
> (?=</td>) # look-ahead; won't be replaced
> }{htmlify()}egx;
>
> sub htmlify {local $_=$1; s/\s/ /g; $_}
>
>
> I think the substitution should have occurred in a subroutine anyway,
> even if $1 was writable.
> Maybe it would be cool if look-ahead had a backslash-thingie notation.
> Erm...
>
> And you might like this one; I personally hate it:
>
> my $text;
> $str =~ s{<td.*?> \K
> (.+?)
> (?{ $text = $^N; $text =~ s/\s/ /g; })
> (?=</td>)
> }{$text}egx;
>
> If you have any better ideas of how it could/should look (with the
> constraints I've mentioned, or a way to break them without ruining every
> Perl programmer's life by breaking the current behaviour) please share
> them :-)
>
> HTH,
>
> ~Y
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