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To: georges <geolim4@gmail.com>
Cc: PHP Internals <internals@lists.php.net>
Date: Mon, 02 Nov 2015 17:47:50 +0100
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Subject: Re: [PHP-DEV] Friend class/function
From: johannes@schlueters.de (Johannes =?ISO-8859-1?Q?Schl=FCter?=)

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On Sun, 2015-11-01 at 17:04 +0100, georges wrote:
> I recently discovered =E2=80=8Bthe "friendship concept" in c++ and i real=
ly
> love the concept.
> And i wonder if the php internals would be interested to implements it
> in the next 7.x major version.

Could you provide use cases where this provides a better interface than
other alternatives? I think there are only very few cases ...

In C++ the primary use-case are binary operators which have to be
written as a free function but need access to private elements. i.e.

   class Complex {
       int _real, _im;
   public:
       Complex(int r, int i) : _real(r), _im(i) {}
       friend Complex operator+(int a, const Complex& b);
   };

   Complex operator+(int a, const Complex& b) {
       return Complex(a + b._real, b._im);
   }

Here the operator+(int, const Complex&) can't be part of a class as the
first operand is a built-in while logically it belongs to the class's
interface.

(note: this specific example isn't good as we could provide accessors to
the real and imaginary part of our complex number but there are cases
where this isn't possible/wanted)

We don't have this situation in PHP, though.

johannes


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