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Thoughts on adopting Python's for/foreach else construct.

php.internals

Michael Morris

6 years ago

I don't remember if this has been discussed before, but I've been working
with some listing code and wishing for a cleaner way to do this

<?php
if (count($a) === 0) {
// code for no results
}
else {
foreach( $a as $key => $value) {
// code for iteration
}
}
?>

How difficult would it be to make the following work in the interpreter?

<?php
foreach($a as $key => $value) {
// code for iteration
}
else {
// code for no results
}
?>

The code of the else clause executes if the foreach is never entered
regardless of the reason (provided the code didn't outright crash)

Thoughts.

Christian Schneider

6 years ago

Am 25.02.2020 um 20:18 schrieb Michael Morris <tendoaki@gmail.com>:

> How difficult would it be to make the following work in the interpreter?
>
> <?php
>  foreach($a as $key => $value) {
>    // code for iteration
>  }
>  else {
>    // code for no results
>  }
> ?>
>
> The code of the else clause executes if the foreach is never entered
> regardless of the reason (provided the code didn't outright crash)

I like the idea.

And I think it makes more sense than what Python actually does:
With Python the else clause is executed if the loop is not exited with a break.
https://book.pythontips.com/en/latest/for_-_else.html

So, yes, I would like a foreach .. else but not the Python way ;-)

- Chris

Nikita Popov

6 years ago

On Tue, Feb 25, 2020 at 8:19 PM Michael Morris <tendoaki@gmail.com> wrote:

> I don't remember if this has been discussed before, but I've been working
> with some listing code and wishing for a cleaner way to do this
>
> <?php
>   if (count($a) === 0) {
>     // code for no results
>   }
>   else {
>     foreach( $a as $key => $value) {
>       // code for iteration
>     }
>   }
> ?>
>
> How difficult would it be to make the following work in the interpreter?
>
> <?php
>   foreach($a as $key => $value) {
>     // code for iteration
>   }
>   else {
>     // code for no results
>   }
> ?>
>
> The code of the else clause executes if the foreach is never entered
> regardless of the reason (provided the code didn't outright crash)
>
> Thoughts.
>

See https://wiki.php.net/rfc/loop_else and https://wiki.php.net/rfc/loop_or
for previous proposals on the topic.

I believe an important concern from previous discussions was that this
breaks BC in a really bad way, due to the dangling else conflict. Which is
why the latter proposal used "or" instead of "else".

Regards,
Nikita