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From: philip@pescadero.Stanford.EDU (Philip Machanick)
Newsgroups: comp.lang.c++
Subject: Re: Base class access: by name only?
Message-ID: <1990Nov29.224455.476@Neon.Stanford.EDU>
Date: 29 Nov 90 22:44:55 GMT
References: <1990Nov19.012937.27283@Neon.Stanford.EDU> <59306@microsoft.UUCP> <1990Nov29.175741.116@Think.COM>
Sender: news@Neon.Stanford.EDU (USENET News System)
Reply-To: philip@pescadero.stanford.edu
Organization: Computer Science Department, Stanford University
Lines: 28

In article <1990Nov29.175741.116@Think.COM>, barmar@think.com (Barry Margolin) writes:
|> In article <59306@microsoft.UUCP> jimad@microsoft.UUCP (Jim ADCOCK) writes:
|> >Yes, languages that allow accessing a superclass without using its name
|> >only allow single superclasses.  If you have multiple superclasses you
|> >need to be able to specify *which* super class -- the obvious way to do
|> >this is by using the superclasses name.
|> 
|> Not necessarily.  Flavors and CLOS define a total ordering of all the
|> ancestors of a flavor/class; this total ordering is defined to be
|> consistent with the partial orderings specified by the orders in which the
|> immediate superclasses are named in the subclass definitions.  When a
|> method invokes a superclass method the next flavor/class after the current
|> one in the total order is chosen.  (In CLOS it gets a bit more complicated
|> because of multimethods, but the same basic idea is used.)
|> 
|> I don't think these systems even provide a way to bypass the ordering and
|> invoke a specific superclass's method (well, except that the data
|> structures are visible, so it's possible to do just about anything).

In C++, a partial ordering is used, so it would not be possible to allow
an unnamed base class in some cases - just as, in some cases, a named
reference to a base class is ambiguous and therefore an error. This does
not mean such a feature could never be used. Back to my original question:
would it be _useful_? (I was hoping for a response from someone who had
actually used this feature, e.g., in Smalltalk.)
-- 
Philip Machanick
philip@pescadero.stanford.edu