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Date: Sat, 26 Sep 2015 12:31:46 -0600
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To: Rowan Collins <rowan.collins@gmail.com>
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Subject: Re: [PHP-DEV] Arrow function expressions in PHP
From: levim@php.net (Levi Morrison)

On Sat, Sep 26, 2015 at 11:07 AM, Rowan Collins <rowan.collins@gmail.com> w=
rote:
> On 26/09/2015 17:17, Levi Morrison wrote:
>>
>> What concerns do you have about `fn($x) =3D> $x * 2` or `function($x) =
=3D>
>> $x * 2`? I will be writing a proper RFC later but I wanted to get
>> discussion going now.
>
>
> If a keyword is required next to the parameters, having the =3D> as a sep=
arate
> token looks a bit weird. It no longer matches other languages, so how abo=
ut
> thinking a bit further outside the box?

Thank you for the feedback. I feel like the rest of what you proposed
was a bit too far outside of the box. For what it is worth no token
after the paren is necessary =E2=80=93 you could do `fn($x) $x * 2` (or
`function($x) $x * 2`). I think this is a case where more syntax
helps.

On Sat, Sep 26, 2015 at 11:07 AM, Rowan Collins <rowan.collins@gmail.com> w=
rote:
> On 26/09/2015 17:17, Levi Morrison wrote:
>>
>> What concerns do you have about `fn($x) =3D> $x * 2` or `function($x) =
=3D>
>> $x * 2`? I will be writing a proper RFC later but I wanted to get
>> discussion going now.
>
>
> If a keyword is required next to the parameters, having the =3D> as a sep=
arate
> token looks a bit weird. It no longer matches other languages, so how abo=
ut
> thinking a bit further outside the box?
>
> One of the random thoughts that popped into my head during the previous
> discussion was to base the syntax on the C for-loop, which would also giv=
e a
> place for bound variables without the "use" keyword. e.g. your example co=
uld
> become fn($x;; $x * 2)
>
> I picked "lambda" as the keyword before, and gave these examples:
>
> # lambda(params; bound vars; expression)
> $double =3D lambda($a;; 2*$a)
> $x=3D3; $triple =3D lambda($a; $x; $x * $a)
>
> function sumEventScores($events, $scores) {
>     $types =3D array_map(lambda($event;; $event['type']), $events);
>     return array_reduce($types, lambda($sum, $type; $scores; $sum +
> $scores[$type]));
> }
>
>
> Adding in the type information, we'd get this:
>
> lambda(int $sum, string $type; $scores; $sum + $scores[$type])
> # or with fn() if you prefer:
> fn(int $sum, string $type; $scores; $sum + $scores[$type])
>
>
> If return typehints are also required, I'm not sure where they'd best be
> placed. If they're outside the parens, they end up after the expression,
> which might look odd:
> fn(int $sum, string $type; $scores; $sum + $scores[$type]): int
>
> A few other possibilities:
> fn(int $sum, string $type; $scores; $sum + $scores[$type]; int)
> fn(int $sum, string $type: int; $scores; $sum + $scores[$type])
> fn:int(int $sum, string $type; $scores; $sum + $scores[$type])
>
>
> All of this assumes that the shorthand is only available for simple
> expressions, not function bodies, but it seems a bit rendundant to allow
> both of these:
> function($x) { foo(); bar(); baz(); }
> fn($x) =3D> { foo(); bar(); baz(); }
>
> And only marginally more useful if variables are auto-captured, with all =
the
> downsides of that which have already been raised:
> function($x) use ($y) { foo($x); bar($x, $y); }
> fn($x) =3D> { foo($x); bar($x, $y); }
>
> Regards,
>
> --
> Rowan Collins
> [IMSoP]
>
>
> --
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