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Date: Sat, 31 Aug 2013 02:01:12 +0200
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To: Stas Malyshev <smalyshev@sugarcrm.com>
Subject: Re: [PHP-DEV] [RFC] Argument unpacking
From: bobwei9@hotmail.com (Bob Weinand)

Hi!

Am 31.8.2013 um 01:39 schrieb Stas Malyshev <smalyshev@sugarcrm.com>:

> Hi!
>=20
>> function short (...$args) {
>>    if (count($args))
>>        return long(...$args, "some value");
>> }
>=20
> This is exactly the problem. Since $args has undefined number of
> arguments, there's no way to determine where "some value" ends up. =
Which
> means it's impossible to understand what's going on here. Now, if we =
had
> named arguments, like python had, then using "some value" as a named
> argument might work (and we'd need to see what to do with named
> arguments in this case), but as positional argument this just doesn't
> make much sense beyond some very esoteric things that nobody uses
> directly, without wrapping libraries (like partially applied =
functions)
> - at least in PHP.

That's why there is an if (count($args)) (I just forgot to add an =3D=3D =
7)

It should read:

function short (...$args) {
   if (count($args) =3D=3D 7)
       return long(...$args, "some value");
}

And when you name the example with the "esoteric things", I'd like to =
have them
in the most readable format possible, which isn't achievable with =
func_get_args().

>> And I think you are really arguing about non-issues.
>> Example: Multiple uses of unpacking syntax makes sense when you call =
a
>> function with a variadic parameter:
>>=20
>> function variadic (...$args) {
>>    // do something
>> }=20
>>=20
>> variadic(...$array1, ...$array2);
>=20
> Again, since parameters in PHP are positional, they have meaning
> depending on position. If you just wanted to pass an array, pass an
> array, you don't need to use variadic syntax for that. Variadic syntax
> makes sense only if positions there have meanings and you want to give
> specific meanings to specific arguments in specific positions. In that
> case, ...$array1, ...$array2 doesn't work since you can not have
> meaningful positions. Only case where it works if you do functional
> operations like partial application, where the meaning of the function
> is not important but only the fact that it is a function is important.
> But I don't think we need special syntax to do such things.

I mean, it looks way cleaner to use this instead of:

call_user_func_array("variadic", array_merge($array1, $array2));

And no, the order isn't always important. Example:

function variadic (...$args) {
    return array_reduce($args, function ($a, $b) { return $a*$b; }, 1);
}

Yes, this is a very simple example, but just to show the idea of it.

And even when the order is important, it may be useful:

// according to implementation, arrays are expanded in insertion order =
here
// https://github.com/nikic/php-src/compare/variadics...splat#L11R3263
$short_default_options =3D [
    "arg1" =3D> 1,
    "arg2" =3D> 3,
    "arg3" =3D> 7,
];

function short (...$extra_options) {
   global $short_default_options; // in classes, this would be a =
$this->short_options
   if (count($args) <=3D 3)
       return long(...$short_default_options, ...$extra_options);
}

function long ($arg1, $arg2, $arg3, $arg4 =3D 0, $arg5 =3D 0, $arg6 =3D =
0) {
    // do something
}

> --=20
> Stanislav Malyshev, Software Architect
> SugarCRM: http://www.sugarcrm.com/
> (408)454-6900 ext. 227



Bob Weinand