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From: bs@alice.UUCP
Newsgroups: comp.lang.ada
Subject: Re: C++ as a way to use private types in C
Message-ID: <6735@alice.uUCp>
Date: Fri, 20-Mar-87 09:35:52 EST
Article-I.D.: alice.6735
Posted: Fri Mar 20 09:35:52 1987
Date-Received: Sun, 22-Mar-87 15:43:24 EST
References: <8703200117.AA10060@ucbvax.Berkeley.EDU>
Organization: AT&T Bell Laboratories, Murray Hill NJ
Summary: Multiple inheritance need not be expensive
List-Id: <comp.lang.ada>

In article <8703200117.AA10060@ucbvax.Berkeley.EDU>, WELTY@GE-CRD.ARPA.UUCP writes:
> 
> >C++ is very similar to Ada, except for tasking where the older C-style
> >facilities are used.
> 
> C++ contains a number of serious differences, actually ...
> 
> Objects in C++ (like objects in Flavors, CommonLoops, Smalltalk, etc.)
> may be dynamically allocated and freed -- Ada Generics are a somewhat
> weaker notion.  Also, C++ provides single inheritance (unfortunately,
> it does not support multiple inheritance; its designers feel that multiple
> inheritance has unacceptable performance penalties).

One of the ways C++ differs from Smalltalk and the object based
Lisps is in efficiency (typically differences in low-level efficiency is
measured in factors, not percents). To preserve this difference I avoid
inherently slow features like the plague. However, multiple inheritance
is not one of those. I have an experimental version of C++ with multiple
inheritance. The added overhead in calling a member function is one
memory reference plus one addition.

The snag is that I'm still not fully convinced that multiple inheritance
is a significant improvement over single inheritance. but I guess that
this is not the right newsgroup for that question.