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Date: Wed, 31 May 2017 22:40:24 +0200
To: internals <internals@lists.php.net>, Levi Morrison <levim@php.net>,
 Rowan Collins <rowan.collins@gmail.com>
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Subject: Re: [PHP-DEV] [RFC]Discuss] Syntax for Arrow Functions
From: ilija.tovilo@me.com

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My preferences: 1, 3, 4, 5, (big void), =C2=A02.
I actually like 4 the most but I get that that might not be practical if =
it leads to unexpected behaviour.

I can=E2=80=99t think of a scenario where capturing by reference would be=
 helpful in a single line closure. 5 just adds additional complexity with=
 no additional benefit IMHO.

Also, in response to=C2=A0Rowan, a Ruby-style syntax should be possible t=
hough:

=7B=7Cparam=7C expr=7D

Only caveat is that the =7C=7C would be required if there are no paramete=
rs:

=7B=7C=7C expr=7D

Levi has mentioned this one before. You could even omit the braces here.

Ilija


On 30 May 2017, 19:58 +0200, Levi Morrison <levim=40php.net>, wrote:
> Internals,
>
> The previous discussion thread has died down significantly and so I'd
> like to start a new one to refocus. This message has some redundant
> information by design so people don't have to reference the other
> thread so much.
>
> Based on the discussion there are a few different syntax choices
> people liked. Overall it's a feature that people seem to want but
> everyone seems to prefer a different syntax choice.
>
> 1. fn(params) =3D> expr
> 2. function(params) =3D> expr
>
> 3. (params) =3D=3D> expr
> 4. (params) =3D> expr
>
> Note that 3 and 4 require a more powerful grammar and parser and that
> 4 has ambiguities. I think we can work around them by rules -- only
> mentioning it because its popular because of JavaScript and do not
> prefer this at all.
>
> Note that 1 requires a new keyword.
>
> Option 2 looks the best from that perspective but is by far the
> longest; remember people are partially interested in this feature
> because they want shorter closures which this doesn't really help.
>
> This is why everyone is so divisive. All options have drawbacks.
> Additionally some people don't like binding by value and would prefer
> ref, and others really would be against by-ref.
>
> Which brings me to an option I don't think was ever discussed on list:
>
> 5.
> =5B=5D(params) =3D> expr // binds no values
> =5B=3D=5D(params) =3D> expr // binds by value
> =5B&=5D(params) =3D> expr // binds by reference
>
> It has quite a few good qualities:
>
> - No new keywords
> - Can choose between reference and value
> - Concise
> - Has precedence in C++, a major language
> - Can be done in our existing grammar and parser=5B1=5D
> - Can be extended to allow explicit binding of variables:
> // all equivalent
> // y is bound by value, array by reference
> =5B&, =24y=5D(=24x) =3D> =24array=5B=5D =3D =24x + =24y
> =5B=3D, &=24array=5D(=24x) =3D> =24array=5B=5D =3D =24x + =24y
>
> And of course it does have downsides:
>
> - Symbol soup (it uses a lot of symbols)
> - A minor BC break. Empty arrays which are invoked as functions are
> currently guaranteed to be errors at runtime and would have a new
> valid meaning. Here's an example from inside an array literal:
>
> // error at runtime previously
> =5B =5B=5D(=24x) =3D> =24x =5D
> // now an array with one item which is a closure that returns
> its parameter
>
> Sara pointed out that we'd need to keep a leading =60=3D=60 or =60&=60 =
in the
> array to disambiguate from our array closure form.
>
> Overall I'd prefer 1 or 5. What do you guys think=3F
>
>
> =5B1=5D: I'm pretty sure it can be done but until it's done I can't say=

> so confidently because sometimes there are things lurking in our
> grammar I forget about.
>
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