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Date: Fri, 3 Feb 2017 23:01:04 -0600
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To: Stephen Reay <php-lists@koalephant.com>
Subject: Re: [PHP-DEV] [RFC][Discuss] Arrow Functions
From: aaron@trowski.com (Aaron Piotrowski)

Hi Stephen,

> On Feb 3, 2017, at 10:38 PM, Stephen Reay <php-lists@koalephant.com> =
wrote:
>=20
>=20
>>=20
>> I absolutely agree that it's terrible=E2=80=A6 the point is that =
types (even potential future union types) can be used with short =
closures, but it certainly doesn't mean they should be. I don't think =
confusion with a non-existent and non-recommended way of coding should =
be a reason against a particular syntax.
>=20
> Using type hints is a part of the language. It even has benefits that =
I can absolutely see being used here:
>=20
> array_map(function(Foo $x) =3D> $x->bar());=20
>=20
> If Foo is a class/interface with a method of bar, your IDE can know =
that it's a valid method to call.
>=20
> That of course is in addition to the benefit of getting useful type =
errors from PHP itself.

You raise a good point about IDEs, types might have a place with short =
closures. Still, I don't see union types, if they ever exist, being =
common here. Taking your example with the other proposed syntax:

    array_map(|Foo $x| =3D> $x->bar());

Honestly I'm not sure which is better=E2=80=A6 personal preference at =
this point, each has their merits.

>>=20
>>> As has been said before, PHP is relatively verbose compared to other =
languages. That makes it slightly more characters to type, but it also =
makes it absolutely clear what is happening.
>>=20
>> Using `function` IMO makes it more likely to confuse a short closure =
with a regular closure. Reusing the `function` keyword with different =
semantics may result in some confusion.
>>=20
>=20
> So we should instead use syntax already used for bit wise OR, and =
further confuse the situation when the function has no parameters and =
reusing the logical OR operator. Brilliant.

This is certainly a downside, though expressions cannot start with a =
logical or bitwise OR, so that will help differentiate them. However, it =
is hard to argue that `function` could be confusing when something like =
`|| =3D> $x ** 2` may be more confusing, so point taken. Regardless, I =
still prefer the visual difference since the auto-capture behavior is so =
different from other functions.

Cheers!

Aaron Piotrowski