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Date: Wed, 29 Jun 2011 13:34:39 -0400
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To: John Crenshaw <johncrenshaw@priacta.com>
Cc: Jarrod Nettles <jarrod@squarecrow.com>, 
	"internals@lists.php.net" <internals@lists.php.net>, "neufeind@php.net" <neufeind@php.net>
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Subject: Re: [PHP-DEV] Inline Lambda Functions
From: ircmaxell@gmail.com (Anthony Ferrara)

Well, we could take python's approach and use a syntax similar to this:

array_filter($source, lambda $x: $x < 5);

array_map($source, lambda $x, $y: $x < $y);

However, I would question the need.  Pythonic lambdas cannot contain
anything but expressions.  Therefore they cannot have any meaningful
side effects.  While this is good, it also raises the question as to
the need for it.  PHP has first-class anonymous functions, something
which python does not (it has local functions, or lambdas, but no true
anonymous function, every non-lambda has a name).  So the need in PHP
for a lambda style construct is greater than PHP's.

And what's the gain for PHP?  A few less characters to type?  I'm not
sure that readability is gained, compare:

array_filter($array, function($element) { return $element < 5; });

and

array_filter($array, lambda $element: $element < 5);

I feel the first is more readable at a glance.

Anthony

On Wed, Jun 29, 2011 at 1:03 PM, John Crenshaw <johncrenshaw@priacta.com> w=
rote:
>
>> Instead of this.....
>>
>> array_filter($source, function($x){ return $x < 5; });
>>
>> Being able to do this..... (or something like it).
>>
>> array_filter($source, $x =3D> $x < 5);
>
> This really isn't clear. Deciphering the intent of the code requires look=
ing at all the surrounding stuff, because it could mean something totally d=
ifferent in an array. In other words,
>
> =A0 =A0// This would be a lambda
> =A0 =A0array_filter($source, $x =3D> $x < 5);
> =A0 =A0// This would not
> =A0 =A0array($source, $x =3D> $x < 5);
> =A0 =A0// and this would not
> =A0 =A0call_user_func_array('array_filter', array($source, $x =3D> $x < 5=
));
>
> The fact that the syntax for an expression isn't portable in places where=
 (so far) every other expression has been, is a serious concern.
>
> Additionally, the proposed syntax is unusable for functions with more tha=
n one line, making it similar in badness to if statements without braces. I=
MO the current syntax for inline functions is perfectly sufficient, even fo=
r the PLINQ example given earlier, and has massive advantages over this one=
 in terms of readability, affordance, flexibility, and language clarity.
>
> John Crenshaw
> Priacta, Inc.
>
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