From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=0.2 required=5.0 tests=BAYES_00,INVALID_MSGID,
	REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,2045dce6c7815bab,start
X-Google-Attributes: gid103376,public
From: kbrun@ibm.net
Subject: access types and dispatching subprograms
Date: 1996/06/23
Message-ID: <4qjqre$44lo@news-s01.ny.us.ibm.net>#1/1
X-Deja-AN: 161703108
reply-to: kbrun@ibm.net
newsgroups: comp.lang.ada
Date: 1996-06-23T00:00:00+00:00
List-Id: <comp.lang.ada>


I have some trouble with Ada95 dispatching subprograms and access types.
AFAIK, a proc. call should dispatch if all corresponding actual parameters
are of (*or pointing to*) type T'Class and if the formal parameters are
of (*or pointing to*) type T. Still, the following code sample doesn't
work.

--

package T is

   type T is tagged null record;
   type T_p is access all T;
   type TC_p is access all T'class;

   type T1 is new T with null record;
   type T1_p is access all T1;

   procedure disp(p: T_p);
   procedure disp(p: T1_p);

   procedure do_dispatch;
end T;

package body T is

   procedure disp(p: T_p) is
   begin
     Put("T_p");
   end disp;

   procedure disp(p: T1_p) is
   begin
     Put("T1_p");
   end disp;

   procedure do_dispatch is
      classp: TC_p := new T1;
   begin
      disp(classp);	-- this call won't dispatch, instead it causes
                        -- a compiler error. what's wrong?
   end do_dispatch;
end x;

--

Could someone please enlighten me on this subject?

-- Klaus A. Brunner   Austria, Europe
-- mailto:kbrun@ibm.net