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From: Martin <martin.dowie@btopenworld.com>
Newsgroups: comp.lang.ada
Subject: Re: Ada2012 Invariants and obaque types
Date: Wed, 22 Jun 2011 06:57:19 -0700 (PDT)
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Date: 2011-06-22T06:57:19-07:00
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On Jun 22, 11:39=A0am, Egil H=F8vik <egilho...@hotmail.com> wrote:
> > Example:
> > package P1 is
> > =A0 =A0type T1 is tagged private
> > =A0 =A0 =A0 with Invariant =3D> Is_Valid (T1);
>
> I believe it's called Type_Invariant, not just Invariant.
>
> =A0http://www.ada-auth.org/standards/12rm/html/RM-7-3-2.html#I3544

Sadly, that still didn't help:

package P1 is
   type T1 is tagged private
     with Type_Invariant =3D> True;
private
   type Imp;
   type Imp_Ref is not null access Imp;
   type T1 is tagged
      record
         I : Imp_Ref;
      end record;
end P1;

Results in:
gnatmake -d -PH:\Ada\test_invarients\test_invarients.gpr p1.ads
gcc -c -g -g -gnatE -fstack-check -gnato -gnatf -fcallgraph-info=3Dsu,da
-gnat12 -I- -gnatA H:\Ada\test_invarients\src\p1.ads
p1.ads:5:04: type "Imp" is frozen at line 2 before its full
declaration
gnatmake: "H:\Ada\test_invarients\src\p1.ads" compilation error

[2011-06-22 14:53:53] process exited with status 4 (elapsed time:
16.29s)

Thanks anyway.

-- Martin
p.s. I got 'Invariant' from the AI...must now remember that AI's are
not always the 'latest-and-greatest'!