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From: barmar@think.com (Barry Margolin)
Newsgroups: comp.lang.c++
Subject: Re: Base class access: by name only?
Message-ID: <1990Nov29.175741.116@Think.COM>
Date: 29 Nov 90 17:57:41 GMT
References: <1990Nov19.012937.27283@Neon.Stanford.EDU> <59306@microsoft.UUCP>
Sender: news@Think.COM
Organization: Thinking Machines Corporation, Cambridge MA, USA
Lines: 22

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).
--
Barry Margolin, Thinking Machines Corp.

barmar@think.com
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