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From: Barry and Jackie Schiff <schiff@netspace.net.au>
Subject: A question for compiler vendors/lang experts. redefinition of "="
Date: 1997/12/16
Message-ID: <34964C63.F97005E6@netspace.net.au>#1/1
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Date: 1997-12-16T00:00:00+00:00
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Got one answer from a large compiler vendor when another vendor's
implementation implies otherwise. Looked in the Rationale and LRM and it
was hard to find a clear answer. So here is the question for all those
language experts out there:


package Foo is

    type objects is abstract tagged record
        Some_value : some_type;
    end record;

    type class_wide_pointers is access all objects'class;

    function "="(left, right : access objects) return boolean; --
Legal??

end Foo;


The question: Is the redefinition of "=" shown above legal and if so
what are the semantics.  Specifically, is "=" a dispatching primitive
operation or is it ambiguous with the predefined equality defined for
the class_wide_pointers type.

--------------
In my reading the LRM it seems to me that the spirit of access
parameters is that the above operation is a dispatching operation. I
have had a large Ada compiler vendor tell me that the above is
ambiguous. While another compiler implements that above as a dispatching
operation. Can anyone point me to the definitive answer in the LRM.


Thanks in advance. If it is not to much trouble could you email answer.


--Barry Schiff