Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!mips!spool.mu.edu!uunet!microsoft!jimad
From: jimad@microsoft.UUCP (Jim ADCOCK)
Newsgroups: comp.std.c++
Subject: Re: Tags, typecodes, experience with these things.
Message-ID: <71305@microsoft.UUCP>
Date: 15 Mar 91 00:39:13 GMT
References: <1399@culhua.prg.ox.ac.uk> <27D3E544.619A@tct.uucp> <4338@lupine.NCD.COM> <1991Mar12.123811.13701@kodak.kodak.com> <9661@exodus.Eng.Sun.COM>
Reply-To: jimad@microsoft.UUCP (Jim ADCOCK)
Organization: Microsoft Corp., Redmond WA
Lines: 11

In article <9661@exodus.Eng.Sun.COM> chased@rbbb.Eng.Sun.COM (David Chase) writes:
|I also think that the language system should support these features,
|but that is probably a religious argument.  Certainly, if nifty
|features are confined to objects with vptrs the costs can be kept low.

Help me out.  The obvious implementations to me would be either to 
store such information in a given vtable slot [slot "0" say] or
indirect via a vtable function that is always automatically defined
[for classes that support runtime type info.]  Either approach would
seem to defeat the not-too-uncommon situation in C++ where two classes
can share a vtable in common.  Or am I missing something?