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From: bobduff@world.std.com (Robert A Duff)
Subject: Re: Extending A Generic Signature Package
Date: 1997/03/22
Message-ID: <E7G9In.FEr@world.std.com>#1/1
X-Deja-AN: 227573890
References: <5gkv23INN3rn@thalamus.cis.ohio-state.edu>
 <5gtvbv$1nj@pandora.cs.utwente.nl> <JSA.97Mar21135016@alexandria>
 <5guuehINN6iq@thalamus.cis.ohio-state.edu>
Organization: The World Public Access UNIX, Brookline, MA
Newsgroups: comp.lang.ada
Date: 1997-03-22T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <5guuehINN6iq@thalamus.cis.ohio-state.edu>,
david scott gibson <dgibson@thalamus.cis.ohio-state.edu> wrote:
>So in this case it's clear to us and the compiler what specific type
>derived from Base Get_Object returns.  It may or may not be an access
>type.  If an access type, Op1 could have an access parameter formal
>and still dispatch.  However, Get_Object must return a tagged type and
>thus the value returned must be returned by reference in either case,
>right?

No, tagged types are returned by copy, unless the type is limited.

>...  So whether explicit or not X, the value of X must be a pointer
>to some object.  Is that right?  If Get_Object doesn't return an acces
>type and we don't use Unchecked_Access or aliased variables anywhere
>in the program, does Ada guarantee that the object to which X points
>cannot be aliased?

Not sure exactly what you're getting at, but Ada allows and/or requires
pass-by-reference in some cases, and those constitute aliases in the
normal sense of the word.

- Bob