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Date: Tue, 30 May 2017 12:49:15 -0600
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To: Nikita Popov <nikita.ppv@gmail.com>
Cc: =?UTF-8?Q?Bj=C3=B6rn_Larsson?= <bjorn.x.larsson@telia.com>, 
	PHP internals <internals@lists.php.net>
Content-Type: text/plain; charset="UTF-8"
Subject: Re: [PHP-DEV] [RFC]Discuss] Syntax for Arrow Functions
From: levim@php.net (Levi Morrison)

>> You mentioned ability to explicitly specify binding as a possible extension.
>> However
>>
>>     [$var1, $var2]()
>>
>> is not necessarily failing right now, it may be a valid array callable.
>>
>> Nikita
>
> As already mentioned we must maintain a leading `=` or `&`:
>
>   [=, $var1, $var2]()
>   [=, $var1, $var2]()
>
> Sorry if that was unclear.

Oops, forgot to change the bottom line:

   [=, $var1, $var2]()
   [&, $var1, $var2]()

The first line means "bind any implicit usages of variables by value,
and also bind $var1 and $var2 by value".
The second line means "bind any implicit usages of variables by
reference, and bind $var1 and $var2 by value".

This exists in C++ but C++ allows you to drop the leading `=` or `&`.
We cannot, for precisely the reason you mentioned.