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Date: Thu, 16 Jan 2014 11:49:17 +0100
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Subject: Re: [PHP-DEV] Introducing "Array Of" RFC
From: matthieu@mnapoli.fr (Matthieu Napoli)

Le 16/01/2014 11:01, php@tutteli.ch a écrit :
>> + 1 for the RFC
>>
>> But if i'm not completely wrong, there is performance decrease instead of
>> increase in your tests?
>> https://gist.github.com/krakjoe/8444591
>>
>> [joe@fiji php-src]$ sapi/cli/php isTest.php 10000
>> objects: 10000
>> arrayof:        0.00645113
>> instanceof:     0.00560713
>
> I gave the RFC a few more thoughts and came to the conclusion that it
> does not fit to PHP (due to the performance penalties involved).

The performance penalty is the same as if you were type-checking yourself.

And on the gist linked, we can see that the results vary a lot (not 
enough iterations probably), it's easy to take only the worst one. Here, 
I'll take the one where the numbers are inversed to "prove" my point:

[joe@fiji php-src]$ sapi/cli/php isTest.php 1000
objects: 1000
arrayof:        0.00080991
instanceof:     0.00086308

> The syntax merely hide an ugly design. If you would write the same in
> normal PHP then probably everyone would agree that it is bad design.

How is type checking a bad design?

Between:

function (array $foos) {
     foreach ($foos as $foo) {
         if (! $foo instanceof Foo) {
             throw new InvalidArgumentException("...");
         }
         $foo->bar();
     }
}

and:

function (array $foos) {
     foreach ($foos as $foo) {
         $foo->bar(); // BOOM, fatal error if not correct object given
     }
}

which one is worse?

It's the same problem than this:

function ($foo) {
     $foo->bar(); // fatal error if not correct object given
}

and this:

function (Foo $foo) {
     $foo->bar();
}

> Following an example (doesn't really make sense but outlines the bad
> design)
>
> function foo(Foo[] $foos){
>     if(count($foos) > 0){
>        $a = array_pop($foos);
>        //do something
>       foo($foos);
>     }
> }
>
> Is equivalent to
>
> function foo(array $arr){
>     foreach($arr as $v){
>        if(!($v instanceof Foo)){
>           //trigger_error
>        }
>     }
>     if(count($foos) > 0){
>        $a = array_pop($foos);
>        //do something
>       foo($foos);
>     }
> }
>
> The check adds runtime complexity to the function for each call which is
> obviously not necessary (once would be good enough). And I doubt that
> users would actually make sure that the check is only performed once and
> even if you would argue that one should write it as follows:
>
> function bar(Foo[] $foos){
>     foo($foos);
> }
> function foo(array $foos){
>     if(count($foos) > 0){
>        $a = array_pop($foos);
>        //do something
>       foo($foos);
>     }
> }
>
> Then it is still bad design compared to a collection which actually does
> the check during the addition of elements.
> Although, I like the effort to make PHP somewhat more type safe I am -1
> for this RFC, the implementation respectively. If we want typed arrays
> then the array needs to carry the type to be efficient.
>

Matthieu