Re: C++ Overloading Operators

From:

"Doug Harrison [MVP]" <dsh@mvps.org>

Newsgroups:

microsoft.public.vc.mfc

Date:

Fri, 22 Aug 2008 11:59:18 -0500

Message-ID:

<lirta4h7dqacsc7r9llbvvq2am6fa358us@4ax.com>

On Thu, 21 Aug 2008 10:06:47 +0200, "Giovanni Dicanio"
<gdicanio@_NOSPAM_email_DOT_it> wrote:

Operator overloading in C++ has some "strange" rules, I mean: some operator
overloads should be defined in class scope, others as global methods
(possibly defined as "friend" by the class they operate on, so the they can
access the class private data...).
Frankly speaking, I would have liked to have all operator overloads to be
part of the class, so defined as class methods.

You do need non-member functions to implement asymmetric binary operators,
e.g.

bool operator<(const TCHAR*, const CString&);

That cannot work as a member function, because TCHAR* isn't a class. For
this reason, it's customary to define binary operators as non-members,
sometimes friend functions inside the class body. I also think it makes
them stand out more, and I like seeing the argument types explicitly
specified, since I'm not going to be using the a.f(x) syntax to call it,
but rather a < b.

--
Doug Harrison
Visual C++ MVP