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Cc: Rasmus Schultz <rasmus@mindplay.dk>,
 PHP internals <internals@lists.php.net>
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Date: Thu, 8 Jun 2017 23:20:20 +0200
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Subject: Re: [PHP-DEV] [RFC]Discuss] Syntax for Arrow Functions
From: bjorn.x.larsson@telia.com (=?UTF-8?Q?Bj=c3=b6rn_Larsson?=)

Den 2017-06-08 kl. 19:21, skrev Fleshgrinder:

> On 6/8/2017 6:28 PM, Rasmus Schultz wrote:
>>> it could be a single symbol instead of two
>> even if this can be done without parser ambiguity, it suffers from visual
>> ambiguity with the assignment operator.
>>
>> consider what this would look like if the expression itself uses the
>> assignment operator...
>>
>>      f($x) = $y = $y + $x;
>>
>> versus something like:
>>
>>      f($x) => $y = $y + $x;
>>
>> even that is visually ambiguous when used in arrays though:
>>
>>      $a = [
>>          "foo" => f($x) => $y = $y + $x,
>>      ];
>>
>> also unreadable.
>>
>> even if the parser can cope, I think we need some other symbol that isn't
>> visually ambiguous when used in these contexts?
>>
> Absolutely, yes.
>
> One thing that could work is a combination of colon and equal sign with
> an optional type in between:
>
>      f($x, &$y):= $y = $y + $x
>      f($x, &$y): int = $y = $y + $x
>
> Still, kind of ambiguous if used with a type. Earlier I used the greater
> than sign only:
>
>      f($x, $y)> $x > $y
>      f($x, $y): bool > $x > $y
>
> As we can clearly see, also not optimal. A thing that should work is a
> hyphen greater than:
>
>      f(object $o)->$o->property
>
> Looks weird without proper spacing, but with proper spacing ...
>
>      f(object $o) -> $o->property
>
> ... it looks fine, imho. Of course, we still have the other options that
> were mentioned earlier already:
>
>      f ~> 42  // bad on some keyboard layouts
>      f ==> 42 // I personally do not like this option
>
> Another possibility is to use a keyword. This would definitely avoid
> symbol soup and help visual recognition:
>
>      f do 42
>      f($x) do $x^3
>      f($x, &$y) do $y = $y + $x
>
> However, I am very unsure about this option to be honest.
>
> I'd say my choice here is `~>` but I'm on a US layout, second is `->`.
> Note that the latter is used in Java, Elixier, Erlang, Haskell, Julia,
> OCaml, F#, and probably others.
>
Well, one reason ~> came up in the earlier RFC was that ==> was not seen as
quite the best. I liked the tilde option then and do it now. For me that 
sits on
a nordic keyboard layout, I need to use Alt-gr both for $ and ~, extra 
space for
tilde though. So using tilde is no big hassle ;-)

So not all liked the syntax then, but there was other things making that RFC
fail. If type hinting had been included and variable binding had been 
slightly
different, I think it might have passed.

r//Björn