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=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID
	autolearn=no autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,7f472b5a22d27612,start
X-Google-Attributes: gid103376,public
From: Matthew Heaney <matthew_heaney@acm.org>
Subject: Generic Formal With Discrim Used As Actual - How?
Date: 1998/10/25
Message-ID: <m3af2l77o2.fsf@mheaney.ni.net>#1/1
X-Deja-AN: 404811335
Sender: matt@mheaney.ni.net
NNTP-Posting-Date: Sun, 25 Oct 1998 01:14:01 PDT
Newsgroups: comp.lang.ada
Date: 1998-10-25T00:00:00+00:00
List-Id: <comp.lang.ada>

I'm having trouble passing generic formal types --one of which has an
access discriminant-- as generic actuals to another generic having an
identical profile.  Something like:

generic
   type T1 (<>) is limited private;
   type T2 (O : access T1) is limited private;
procedure GP;

generic
   type T1 (<>) is limited private;
   type T2 (O : access T1) is limited private;
procedure GQ;

with GQ;
procedure GP is
  procedure Q is new GQ (T1, T2);
begin
   null;
end GP;


When I try to compile the body of GP, I get the following message:

(start of compiler message)
gnatf /home/matt/acl/rings/gp.adb
gp.adb:4:30: types of actual discriminants must match formal
gp.adb:4:30: instantiation abandoned

Compilation exited abnormally with code 1 at Sun Oct 25 01:13:09
(end of compiler message)


Can someone explain what's going on here?  Why doesn't this code compile?

Is there any way to pass a formal type with a discriminant as the actual
type of another instantiation?

Thanks,
Matt