Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!uunet!microsoft!jimad
From: jimad@microsoft.UUCP (Jim ADCOCK)
Newsgroups: comp.lang.c++
Subject: Re: asking an object for its type
Message-ID: <71199@microsoft.UUCP>
Date: 11 Mar 91 20:05:47 GMT
References: <70902@microsoft.UUCP> <6900@mace.cc.purdue.edu> <71034@microsoft.UUCP> <27D572F6.2A70@tct.uucp>
Reply-To: jimad@microsoft.UUCP (Jim ADCOCK)
Organization: Microsoft Corp., Redmond WA
Lines: 17

In article <27D572F6.2A70@tct.uucp> chip@tct.uucp (Chip Salzenberg) writes:
|According to jimad@microsoft.UUCP (Jim ADCOCK):
|>...what is really needed is neither the ability to test whether an 
|>object supports some particular method, nor the ability to test whether
|>an object is some exact type, but rather, what is needed is the ability
|>to test whether an object supports some particular protocol. 
|
|Even that isn't enough.  Two unrelated types can both implement "void
|foo(int)".  That doesn't mean that the two foos are equivalent.  The
|"isKindOf" test is the minimum for reasonable dynamic typing in the
|C++ type forest.

I think you and I have different meanings for "protocol."  You seem
to use "protocol" to mean the signature of one method.  I use "protocol" 
to mean that an object has to support a *set* of methods correctly
matching both in signature and meaning.  Thus, I think your call for
an "isKindOf" test is the same requirement as I'm calling for.