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From: Laurent.Guerby@enst-bretagne.fr (Laurent Guerby)
Subject: Re: Question about tagged types and functions
Date: 1996/05/22
Message-ID: <4xpw7xpoc6.fsf@leibniz.enst-bretagne.fr>#1/1
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sender: guerby@leibniz.enst-bretagne.fr
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organization: Telecom Bretagne
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newsgroups: comp.lang.ada
Date: 1996-05-22T00:00:00+00:00
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David> Why does Ada-95 (GNAT 3.01a) tell me that I also *must* have:

David>     function Create return DerivedType;

David> There is something going on with tagged types and functions
David> that I don't understand because if I use

David>     procedure Create(a : out BaseType);

David> it (Ada-95) does not object.

   The status of functions (primitives) that dispatch on result is
special in Ada 95. See RM95-3.9.3(4-6). Or better, read the paper "Ada
9X Tagged Types and their Implementation in GNAT" by Cyrille Comar and
Brett Porter (may be available from http://www.gnat.com, if not in the
TriAda94 Conference proceedings). There's a section devoted to this
error message (4.4) (among other OO error messages ;-).

-- 
--  Laurent Guerby, student at Telecom Bretagne (France), Team Ada.
--  "Use the Source, Luke. The Source will be with you, always (GPL)."
--  http://www-eleves.enst-bretagne.fr/~guerby/ (GATO Project).
--  Try GNAT, the GNU Ada 95 compiler (ftp://cs.nyu.edu/pub/gnat).