Front page | perl.perl5.porters |
Postings from August 2012
On Tue, Aug 28, 2012 at 04:59:46PM -0400, David Golden wrote:
> On Tue, Aug 28, 2012 at 2:43 PM, Ricardo Signes
> <perl.p5p@rjbs.manxome.org>wrote:
>
> > given ($x) {
> > when ($y) { ... } # $x ~~ $y
> > when (4) { ... } # $x == 4
> > when ('4') { ... } # $x eq 4
> > }
> >
> > Deferred/computed values of any sort mean smart match.
> >
> > Two dead-simple special cases: Numeric literals mean ==. String literals
> > mean
> > eq.
> >
>
> I agree this solves many of the technical issues raised, but I fear that
> it's going to confuse some people or mis-set expectations.
>
> * Currently when() does smartmatch, so you have to retrain people not to
> think of when() as smartmatch, but to think of when() as a "smart switch"
> or something.
To be fair, this isn't currently true at all - when is very much a
"smart switch". Consider the behavior of "when (qr/a/ && sub { ... })",
for instance.
> * You can test a value with when() that you can't smartmatch, so if people
> don't internalize that when() is no longer smartmatch, at some point
> they'll smartmatch a literal and expect it to work like when.
>
> Since smartmatching a literal isn't ambiguous, I think that it would be
> less confusing to just add literals to the smartmatch table and let when()
> stay as smartmatch. That means *one* big change instead of two.
I think people will have fewer reservations about accepting weird
special cases like this for a keyword-based control structure
(especially considering the precedent set by while (<>), etc) than for
an infix operator (since it will be a weird special case either way -
"why can i do '$foo ~~ 1', but not '$a = 1; $foo ~~ $a'?".
> FWIW, I would still like "when {...} {...}" as a shorter way to write "when
> (sub{...}) {...}", but think that's "nice to have" and not necessary for
> fixing smartmatch.
I think it's a relatively minor gain, for a larger cost in complexity.
-doy
Thread Previous
|
Thread Next