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From: zu@astbe.UUCP (Olaf Zurth)
Newsgroups: gnu.g++,comp.lang.c++
Subject: Re: initialization question
Message-ID: <822@astbe.UUCP>
Date: 12 Sep 89 14:31:17 GMT
References: <QYzIoRy00iQJM8JkZb@andrew.cmu.edu>
Reply-To: zu@astbe.UUCP (Olaf Zurth)
Organization: GEI Software Technik Berlin, Germany
Lines: 33

In article <QYzIoRy00iQJM8JkZb@andrew.cmu.edu> ct13+@andrew.cmu.edu (Chris Thewalt) writes:
>if I have a class X, and a constructor X(X&) defined, and abc is an
>instance of X,then
>  X a = abc
>works as described in the book.
>However, if I have abc and def as instances of X, and operator + defined
>as: X& operator+(X&, X&), then the following:
>  X a = abc + def
>does not call the constructor when creating a (I get bitwise copy of result).
>Is this behavior correct?
>[note: using GNU g++ version 1.35]

	You have an assigment and therefor you need an 

		operator=(X&)

	for your class. Bitwise copy is default for assigment.
	The best way is to build "save classes", which looks like

		class X {
		    // some stuff
		    X(something);
		    X(X&);
		    operator=(X&);
		    ~X();
		};

	--Olaf Zurth
	[see Stroustrup, p.180]
-- 
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