Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!cs.utexas.edu!milano!pp!riunite!rfg
From: rfg@riunite.ACA.MCC.COM (Ron Guilmette)
Newsgroups: comp.lang.c++
Subject: Re: cant use virtuals in base constructors
Message-ID: <198@riunite.ACA.MCC.COM>
Date: 8 May 89 15:35:00 GMT
References: <DOVE.89May4223113@rocket.stars.flab.Fujitsu.JUNET> <11492@ulysses.homer.nj.att.com>
Reply-To: rfg@riunite.UUCP (Ron Guilmette)
Distribution: comp
Organization: MCC  Austin, Texas
Lines: 38

In article <11492@ulysses.homer.nj.att.com> jss@hector.UUCP (Jerry Schwarz) writes:
>
>In the pre-release of 2.0 there is a way to detect this at compile
>time.
>
>class B {
>public: virtual void f() = 0 ; // f must be supplanted in all
>			       // derived classes.  Allocation of
>			       // a B (directly or via new) is not
>			       // allowed.  
>} ;

That's terrific!  I mean it!  We have been needing a feature like this!

One question.  You said that "f must be supplanted" in all derived classes.
Supplanted how?  Will this be legal?  (I hope so!)

	class base {
	public:
		virtual void f() = 0;
	};

	class middle : public base {
	public:
		virtual void f() = 0;	// force leaves to supplant f()
	};

	class derived : public middle {
	public:
		virtual void f() {}	// finally!
	};


-- 
// Ron Guilmette  -  MCC  -  Experimental Systems Kit Project
// 3500 West Balcones Center Drive,  Austin, TX  78759  -  (512)338-3740
// ARPA: rfg@mcc.com
// UUCP: {rutgers,uunet,gatech,ames,pyramid}!cs.utexas.edu!pp!rfg