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Re: whither study()?
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From:
Andy Dougherty
Date:
January 31, 2012 05:52
Subject:
Re: whither study()?
Message ID:
alpine.DEB.2.00.1201310831470.968@fractal.phys.lafayette.edu
On Mon, 30 Jan 2012, Ricardo Signes wrote:
> * demerphq <demerphq@gmail.com> [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 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.
--
Andy Dougherty doughera@lafayette.edu
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