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Date: Fri, 3 Feb 2017 18:07:43 -0600
Cc: Levi Morrison <levim@php.net>,
 tendoaki@gmail.com
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To: internals <internals@lists.php.net>
Subject: Re: [PHP-DEV] [RFC][Discuss] Arrow Functions
From: aaron@trowski.com (Aaron Piotrowski)

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> On Feb 3, 2017, at 11:53 AM, Levi Morrison <levim@php.net> wrote:
>=20
> One more thing: I'd like to re-emphasize that the syntax that
> JavaScript uses and the one that HHVM/Hack uses are ambiguous in the
> current class of our grammar. The following will not work unless we
> move to a more powerful grammar and parser class:
>=20
>    (params) =3D> expr
>    (params) =3D=3D> expr
>=20
> This is why an un-ambiguous prefix is necessary: the prefix breaks the
> ambiguities. The syntax I have suggested in the RFC and the one I
> suggested just now are not ambiguous because distinct prefixes:
>=20
>    fn(params) =3D> expr
>    |params| =3D> expr
>=20
> I look forward to more discussion!
>=20
> --=20
> PHP Internals - PHP Runtime Development Mailing List
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I personally prefer the `|params| =3D> expr` syntax.

I like the visual separation the syntax provides between auto-capturing, =
short closures and regular closures. It gives the impression that it =
should behave differently, rather than just being a shorter way of =
declaring a closure.

Below are a couple of real-world single line closures using the proposed =
syntax:

    [1] Loop::defer(|| =3D> ($this->when)($exception, $value));
    [2] $this->watcher =3D Loop::delay($time, || =3D> =
$this->resolve($value));

IMHO, the reduced boilerplate required makes it easier to discern what =
is happening.

Regards, Aaron Piotrowski

[1] https://github.com/amphp/amp/blob/master/lib/Coroutine.php#L45-L47
[2] https://github.com/amphp/amp/blob/master/lib/Pause.php#L21-L23=

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