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Postings from January 2012
Re: whither study()?
January 31, 2012 06:17
Re: whither study()?
Message ID: CANgJU+UbNQFU0FVbzMuH_8FBLQYg=whtNR6akNv+kCEXBN_4Jg@mail.gmail.com
On 31 January 2012 14:52, Andy Dougherty <email@example.com> wrote:
> On Mon, 30 Jan 2012, Ricardo Signes wrote:
>> * demerphq <firstname.lastname@example.org> [2012-01-29T04:41:33]
>> > Is it really in Perls interest that I, or anyone else with the chops,
>> > even looks at fixing the bugs related to it? Can we just no-op and
>> > deprecate it?
>> The promise of study is that everything will work the same, with some shift in
>> where cost is. What if study became a nop?
>> We could issue a "useless use of study" but do we really need a warning? The
>> change would be "fixed a bug where study caused regex matches to behave
>> incorrectly," and the performance hit would be like any other disabled bad
>> optimization. What do we know about how much real effect this would be likely
>> to have?
>> > Does anybody have any examples where it actually makes a difference?
>> I second that question, but I only care if the difference is the kind of thing
>> we want to keep around. ;)
> Yes, I've used it, and yes it has typically made a difference (around 5%
> last several times I benchmarked it). However, I've only used it for
> simple patterns of straight ASCII text. I haven't run into any corner
> cases or subtle bugs, but I haven't stressed it too much either.
If you have a case you can share I would really like to see it. My
thinking is that other strategies might provide better results.
> If the most sensible way to fix it is to turn it into a no-op, then that
> sounds like a good plan to me. I would prefer that it not issue a warning
> or be deprecated unless that is a necessary part of fixing whatever bugs
> are uncovered. This way, code that currently runs cleanly will continue
> to run cleanly without intervention.
Definitely. I was hasty when I said "deprecate". No-op is what we
want, as maybe one day it might do something useful.
perl -Mre=debug -e "/just|another|perl|hacker/"