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From: mheaney@on2.com (Matthew Heaney)
Newsgroups: comp.lang.ada
Subject: Re: Dispatching to a common most special ancestor
Date: 12 Jun 2003 08:03:16 -0700
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Stephan Heinemann <zombie@cs.tu-berlin.de> wrote in message news:<bc8cnl$in0$1@news.cs.tu-berlin.de>...
> 
> I wanted Equals to be dispatched to the common object ancestor but
> instead a constraint error is raised. How might I resolve this?

Equals is primitive for the type, which means that the tags of both
objects must match.

One solution is to make the operation dispatch on only the first
object:

function Equals 
  (O1 : access Object;
   O2 : access Object'Class) return Boolean;

Alternatively, you can make Equals a class-wide operation, and then
internally dispatch as necessary:

function Equals (O1, O2 : access Object'Class) return Boolean;