Re: Is it possible to override raw pointer comparison?

From:
blargg.ei3@gishpuppy.com (blargg)
Newsgroups:
comp.lang.c++
Date:
Sun, 24 May 2009 13:52:29 -0500
Message-ID:
<blargg.ei3-2405091352290001@192.168.1.4>
Ian Collins wrote:

Ash wrote:

On May 24, 6:48 am, Neelesh <neelesh.bo...@gmail.com> wrote:

On May 24, 8:26 am, Ash <ashiru...@googlemail.com> wrote:

Why is this ok:

    bool operator==(Foo* a, Foo& b) { return true; }

and if I have:

    Foo* f1; Foo* f2;

then

    f1 == *f2

is valid and calls the above function.

but the following (to try to override equality when called using two
raw pointers: f1 == f2):

    bool operator==(const Foo* a, const Foo* b) { return true; }

doesn't compile?

[...]

operator overloading is
allowed only when atleast one operand is a user defined type (either a
class or an enumeration type).

[...]

I suspected as much, but in which case I don't udnerstand why the
first case:

    bool operator==(Foo* a, Foo& b) { return true; }

is ok? Where's the logic of the C++ standards body in allowing this,
which is an operation on a pointer and not when both operands are?


Foo& is a user defined type.


(to elaborate further) and operator == has no built-in meaning for
user-defined types, thus you can provide one.

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