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Postings from August 2010
Ben Morrow wrote: > Quoth public@khwilliamson.com (karl williamson): >> The reason is that the code always outputs the modifier, even for the >> the existing semantics, so the stringification is permanently different >> from before. That got me to thinking that it should be possible to omit >> the modifier from the stringification unless it is different from the >> default. Thus backward compatibility would not be broken, although it >> is a dangerous thing for modules to be relying on knowing all the >> possible modifiers, and someone could pass them a regex compiled with a >> new modifier that they don't know how to deal with, not just these, but >> any new ones. >> >> But there must be some reason that xism are always shown in the >> stringification, whether they are in effect or not in effect. But I >> can't think what it might be. It would have been simpler for the >> original design to only output them in the stringification when >> different from the default. So there must be a reason why the plus or >> minus of them is always output. Does that reason apply to these new >> modifiers? > > The reason is so that interpolation under different flags works > properly. Currently, if I have > > my $rx = qr/f./s; > > is stringifies to (?s-xim:f.), which means that when I interpolate it > into a pattern with different flags > > "AFx" =~ /a$rx/i; > > the /i is 'cancelled' for the duration of the interpolation (and /s > activated). If it were changed to stringify to (?s:f.) only, the match > above would change from failing to passing. > > So yes, this applies to your new modifiers as well. Every stringified > qr// should include a Cx flag of some kind. The only sane alternative > would be to break compat once, now, by changing the stringification to > something like (?~s:f.), using a new pattern which guarantees to set all > non-specified flags to the default for the duration of the group rather > than leaving them as they were outside. This would allow adding more > flags in the future without breaking compat more than is strictly > necessary. I still don't understand. I had considered interpolation, and it still seems to me that the absence of a modifier means use the underlying default for the duration of that interpolation, no matter what the outer regex says. I don't see a flaw in that thinking. > > Ben >Thread Previous | Thread Next