On 04/12/13 07:55, Paul Makepeace wrote:
On Tue, Dec 3, 2013 at 5:03 PM, Mark Fowler <[email protected]> wrote:
On Tue, Dec 3, 2013 at 6:54 PM, Paul Makepeace <[email protected]> wrote:
$ perl -le '($a = "aabbb") =~ s/b*$/c/g; print $a'
This is where tools like Regexp::Debugger shine. Running
perl -le 'use Regexp::Debugger; ($a = "aabbb") =~ s/b*$/c/g; print $a'
Shows exactly why it gives the output it does (if you hit "n" for next a lot)
Can't use an undefined value as an ARRAY reference at
/Library/Perl/5.16/Regexp/Debugger.pm line 499.
Glad we're not the only ones confused by it ;-) But yeah that's neat.
I don't agree it shows WHY as much as HOW.
The puzzle comes down to whether the $ is part of the first b*
capture. IMO it is (and python seems to agree). Why the engine
restarts having captured as much as it can to the very end strikes me
as counter intuitive. Almost, if not actually, bug-like.
I don't think it does come down to the meaning of $, it comes down to
the meaning of *.
Perl sees 5 b* groups in 'aabbb': the 'bbb' and one between each other
character. The edge-case is whether or not a zero-width match can follow
a non-zero-width match.
Matt
