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From: glenn@huxley.huxley.bitstream.com (Glenn P. Parker)
Newsgroups: comp.lang.c++
Subject: Re: friend operator +(l,r) vs. operator +(r)
Message-ID: <GLENN.90Nov27181143@huxley.huxley.bitstream.com>
Date: 27 Nov 90 23:11:42 GMT
References: <11759@hubcap.clemson.edu> <1990Nov21.053431.22340@actrix.co.nz>
	<FOX.90Nov22085257@papyrus.tempo.nj.att.com>
Sender: glenn@huxley.UUCP
Reply-To: <glenn@bitstream.com> (Glenn Parker)
Organization: Bitstream, Inc.
Lines: 26
In-reply-to: fox@allegra.att.com's message of 22 Nov 90 13:52:57 GMT

In article <FOX.90Nov22085257@papyrus.tempo.nj.att.com>,
fox@allegra.att.com (David Fox) writes:
> Another difference is that the member version can be virtual, while
> the friend version cannot.

Is this really a big difference?  Global overloading can make operator+
work very much like a virtual function.  If the friend function is declared
as:

    class A {
        // ...
        friend A operator+ (const A& left, const A& right);
    };

Then classes derived from A can use operator+ automatically, *or* they can
override it as follows:

    class B : public A {
        // ...
        friend B operator+ (const B& left, const B& right);
    };

--
Glenn P. Parker       glenn@bitstream.com       Bitstream, Inc.
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