Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!boulder!stan!garya
From: garya@Solbourne.COM (Gary Aitken)
Newsgroups: comp.lang.c++
Subject: Re: ptr to member function, even worse
Message-ID: <1018@garya.Solbourne.COM>
Date: 8 May 89 15:05:44 GMT
Organization: Solbourne Computer Inc., Longmont, Co.
Lines: 20

> Thus there is no portable solution in C++
> for the problem as you have stated it, and I believe there is no solution
> at all in AT&T C++ 2.0.  The best alternative is to be sure that dispatch
> knows at least the base class of objp, either by defining a ``universal''
> base class, or by overloading dispatch (perhaps parameterizing it).

The word we have is that 2.0 will solve the problem by passing a descriptor
for virtual functions, instead of an offset into the virtual table.  The
descriptor contains enough info to find the base class.  As described in
a previous article, there is no way I can have a "universal" base class
without putting constraints on the application program, which I don't want
to do.  The big benefit of "pointer to function" is precisely that you
don't need to know anything about the function; otherwise, it would be
just as easy to make a big jump table and pass an index (yeah, I know, in
concept, not necessarily so in practice).
-- 
Gary Aitken

Solbourne Computer Inc.    ARPA: garya@Solbourne.COM
Longmont, CO               UUCP: ...!{boulder,sun}!stan!garya