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From: vaughan@mcc.com (Paul Vaughan)
Newsgroups: comp.lang.c++
Subject: Re: C++, Object Design Methodologies and Software Engineering
Message-ID: <12823@cadillac.CAD.MCC.COM>
Date: 3 Nov 90 20:01:59 GMT
References: <24872@uflorida.cis.ufl.EDU> <2390@lupine.NCD.COM>
Sender: news@cadillac.CAD.MCC.COM
Reply-To: vaughan@mcc.com (Paul Vaughan)
Organization: MCC VLSI CAD Program
Lines: 49
In-reply-to: rfg@NCD.COM (Ron Guilmette)


   From: rfg@NCD.COM (Ron Guilmette)

   A related question was discussed awhile back, i.e. the question of
   why C++ can't be a bit more like Ada.

   Specifically, I think that the kind of thing that you are perhaps
   looking for might be a header file that looks kinda like this:

	   class car;

		   car::car (int cost);
		   car::~car ();
		   heading car::turn (direction d);
		   next_date car::change_oil (station s);

   In other words, a sort of *abbreviated* description of the interface to
   a class which is provided to some user of the class.

   Allowing abbreviated descriptions like this (which leave out information
   about data members) could potentially cut down dramatically on the
   amount of recompilations we have to do over the lifetime of a class.

   I hope that the ANSI committee will consider this possible solution
   for an important (and as yet unresolved) problem.
 . . .

I've suggested this sort of thing for different reasons before, but it
hasn't sparked any enthusiasm.  I proposed that this sort of
declaration would help to solve severe modularity problems.  One thing
that became clear to me was that a very complete declaration is
required.  For instance if the real class definition said

class car : public virtual vehicle {
public:	
  virtual Heading heading() const;
//  . . .
};

You're going to have to declare

class car : public virtual vehicle;
public virtual Heading car::heading() const;

Anyway, I'd lend some support if anyone wants to start a ball rolling
in the ANSI committee.

 Paul Vaughan, MCC CAD Program | ARPA: vaughan@mcc.com | Phone: [512] 338-3639
 Box 200195, Austin, TX 78720  | UUCP: ...!cs.utexas.edu!milano!cadillac!vaughan