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Date: Thu, 14 Jun 2018 10:21:25 +0100
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To: Nikita Popov <nikita.ppv@gmail.com>
Cc: Sara Golemon <pollita@php.net>, PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Strict switch statements
From: rowan.collins@gmail.com (Rowan Collins)

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On 14 June 2018 at 09:35, Nikita Popov <nikita.ppv@gmail.com> wrote:

> On Thu, Jun 14, 2018 at 6:53 AM, Sara Golemon <pollita@php.net> wrote:
>
> > Just for casual discussion at this point:
> > https://github.com/php/php-src/pull/3297
> >
> > switch ($a) {
> >   case FOO:
> >       // Works exactly as current behavior.
> >       break;
> >   case == FOO:
> >      // Nearly identical, though not using the ZEND_CASE optimization.
> >      // Can probably make this equivalent to `case FOO`, but it felt
> > like an interesting direction.
> >      break;
> >   case === FOO:
> >      // Only triggers if `$a === FOO`, no type juggling
> >      break;
> > }
> >
> > Love it? Hate it? See obvious flaws?  The implementation is just a
> > rushed proof of concept, not something I've labored over, it may well
> > have bugs.  Certainly wouldn't target anything earlier than 7.4, if at
> > all.
> >
>
> I like the general idea here (switch with strict type comparison), but not
> super fond of the particular syntax and implementation.
>
> I think if people want to use strict matching, they'll quite likely want to
> have it on all cases. Something like "strict switch ($expr) {}" or "switch
> strict ($expr) {}" or "switch (strict $expr) {}" or "switch ($expr) strict
> {}" or "switch ($expr) { strict; }" or whatever would be preferable in that
> case.
>


For ages, I've had an idea along these lines kicking around.  Like Nikita,
I was assuming that all branches would want strict comparison or none, so
was thinking of putting the operator at the top, something like "switch
($expr) use (===)". I figured it could then be extended so the "===" could
be substituted for any binary operator; for instance, you could match
values into ranges with "switch ($score) use (>=)".

That said, I can see an attraction in a form with the operator on the
branch, if operators other than "==" and "===" are supported; for the range
example, it might be handy to have cases for ">= 50", "> 0", and "=== 0".

I prefer reusing "===" in some way over the word "strict", even if no other
operators are supported, because "strict" could mean a number of things -
"strictly no fall-throughs", for instance - and I think that could cause
confusion (people already expect "strict types" to mean more than it does).

Regards,
-- 
Rowan Collins
[IMSoP]

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