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From: haydens@natasha.juliet.ll.mit.edu (Hayden Schultz)
Newsgroups: comp.lang.c++
Subject: Re: Constructor question
Message-ID: <HAYDENS.91Apr17113619@natasha.juliet.ll.mit.edu>
Date: 17 Apr 91 16:36:19 GMT
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In-Reply-To: pal@xanadu.wpd.sgi.com's message of 15 Apr 91 16:44:35 GMT


>On reading the ARM, it appears that one must define an appropriate
>operator new in order to use placement syntax.  This is fairly trivial
>in this case:

Why do you have to redefine the operator new? Here's a simple example
which does it with a parent class and a derived child class. If
there's no inheratance relationship, you could do the same thing if
you created a conversion operator from C to P.


include <stream.h>

class P {
    int		q;
  public:
    P() {
	q = 5;
    }
    P(int i);

    virtual void x() {
	cout << "parent class\n" << flush;
    };
};

class C : public P {
  public:

    void x() {
	cout << "child class\n" << flush;
    }
};

P::P(int i) {
    this = new C;
}

main()
{
    P	p;

    p.x();
}

	Hayde Schultz (haydens@juliet.ll.mit.edu)