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Postings from August 2010
Quoth public@khwilliamson.com (karl williamson):
> Ronald J Kimball wrote:
> > On Sat, Aug 14, 2010 at 09:13:06AM +0100, Zefram wrote:
> >> Ronald J Kimball wrote:
> >>> my @options_on = qw/ s a /; # where a and b are hypothetical options
> >>> my @options_off = qw/ i b /; # that are on by default
> >> No options are on by default.
> >
> > I know that's the current state, but is that a guarantee going forwards?
> > If options will always be off by default, then we probably don't need
> > (?.m-i:) at all; (?.m) would be sufficient. (And my objection to Ben's
> > proposal would be moot. :)
> >
> > I note that Karl mentioned that the new regex modifiers - /l, /u, and /d -
> > are "automatically inserted" under the appropriate conditions. I don't
> > know if that means they are "on by default" with regards to (?.)
> >
> > Ronald
> >
>
> Yes, /d is on by default.
But there is never a need to turn it off explicitly: it's not a boolean
option, but a three-way choice. The way to turn it off is (?.l:foo) or
(?.u:foo), not (?.-d:foo).
I've mentioned in passing before, and I think I should say again, that
having a /d switch at all is rather confusing. IMHO it would be much
better (if we're going to restrict ourselves to one-letter switches with
no arguments) to just have /u and /l, with the old behaviour implied by
neither of those being present. The new (?.:) syntax would mean that the
one place where /d might potentially be used, (?d-xims:foo), is better
written (?.:foo).
If you're going to introduce pragmata to turn some switches on for some
lexical scopes, the question of 'so how do they get turned off again?'
needs to be addressed in a more systematic way than just introducing a
single special-case switch that turns some other switches off. I would
be happy with either of
use unicode_strings;
/foo/U;
or
use unicode_strings;
/foo/-u;
though the latter obviously has more back-compat considerations. I would
also be happy, for now, with requiring people write
use unicode_strings;
/(?-u)foo/;
if they want to go back to the old semantics.
While we're discussing this: would you be at all open to the idea of
supplying a /a ('ASCII') switch that makes \d\s\w match what everyone
thinks they do (that is, [0-9], [ \t\n] and [a-zA-Z0-9_] respectively)?
Ben
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