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=-1.9 required=5.0 tests=BAYES_00
	autolearn=unavailable autolearn_force=no version=3.4.4
X-Received: by 10.70.102.205 with SMTP id fq13mr1934204pdb.6.1407243994059;
 Tue, 05 Aug 2014 06:06:34 -0700 (PDT)
X-Received: by 10.140.107.137 with SMTP id h9mr22016qgf.16.1407243994007; Tue,
 05 Aug 2014 06:06:34 -0700 (PDT)
Path: 
 border2.nntp.dca1.giganews.com!border1.nntp.dca1.giganews.com!nntp.giganews.com!h18no14392482igc.0!news-out.google.com!b3ni5434qac.1!nntp.google.com!v10no4523168qac.1!postnews.google.com!glegroupsg2000goo.googlegroups.com!not-for-mail
Newsgroups: comp.lang.ada
Date: Tue, 5 Aug 2014 06:06:33 -0700 (PDT)
Complaints-To: groups-abuse@google.com
Injection-Info: glegroupsg2000goo.googlegroups.com;
 posting-host=85.242.67.121;
 posting-account=nd46uAkAAAB2IU3eJoKQE6q_ACEyvPP_
NNTP-Posting-Host: 85.242.67.121
User-Agent: G2/1.0
MIME-Version: 1.0
Message-ID: <986b5653-f446-4833-9a83-426f45b7c03f@googlegroups.com>
Subject: Problem with indefinite discriminant records in container
From: john@peppermind.com
Injection-Date: Tue, 05 Aug 2014 13:06:34 +0000
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
Xref: number.nntp.dca.giganews.com comp.lang.ada:188156
Date: 2014-08-05T06:06:33-07:00
List-Id: <comp.lang.ada>

I want to store records of different size in Ada.Containers.Indefinite_Vect=
ors:

 type Rt_Class (Method_Table_Size : MethodId;
                  Superclass_Count  : ClassId) is record
      Id              : ClassId;
      Is_Interface    : Boolean;
      Methods         : Rt_Methods (1 .. Method_Table_Size);
      Superclasses    : Rt_Class_Ids (1 .. Superclass_Count);
      Inst_Prop_Count : Natural;
      Method_Count    : Natural;
   end record;

   package Class_Vectors is new Ada.Containers.Indefinite_Vectors
     (Index_Type =3D> ClassId,
      Element_Type =3D> Rt_Class);
   use Class_Vectors;
   type Rt_Classes is new Class_Vectors.Vector with null record;

it compiles but I get a *runtime* error "instantiation error" with explanat=
ion=20
"invalid constraint: type has no discriminant" when the above package is in=
stantiated.

Rt_Methods and Rt_Class_Ids are array types and all of this occurs in the p=
rivate part of a package.=20

How can I store different versions of an indefinite record with discriminan=
ts such as Rt_Class in some array or vector? Using access types would be ve=
ry hard if not impossible in this case because of the associated scope rest=
rictions. Somewhat annoying in this case is also that this table/array only=
 needs to be created *once* in the beginning of program execution and other=
wise is completely static and read-only ... and access should be as fast as=
 possible.

Any ideas or suggestions?