Re: Strict switch statements

Den 2018-06-14 kl. 11:21, skrev Rowan Collins:

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,

Yup, I also like this idea very much. Using the === syntax is a clear message on what's it all about. Having the ability to extend it to other operators is also interesting, e.g. !== & !=. Another point is that by keeping switch keyword it would be relatively easy to upgrade legacy code, making it more robust. Of course there is a use for a new keyword like match extending the functionality even more. Maybe we can have both? I'm thinking if one should be able to have like: switch ($a)  {

    case === FOO:
        break;
    case !== BAR:
        break;

} or: switch ($a) with !== {

    case FOO:
        break;
    case BAR:
        break;
    default:
        break;

} or: switch ($a, ===)  {

    case FOO:
        break;
    case BAR:
        break;

} r//Björn Larsson