From: "Grein, Christoph" <christoph.grein@eurocopter.com>
Subject: Re: Dispatching and generics - language lawyer question
Date: Wed, 24 Jul 2002 07:33:46 +0200 (MET DST)
Date: 2002-07-24T07:33:46+02:00 [thread overview]
Message-ID: <mailman.1027489082.2047.comp.lang.ada@ada.eu.org> (raw)
> There is a problem with "reemergence" of predefined operators ...
For untagged types, _redefined_ equality does not correctly compose and
_predefined_ equality reemerges in generics if not properly transferred by a
formal parameter:
type X is something;
function "=" (L, R: X) return Boolean; -- redefine
type Y is record
C: X;
end record;
A, B: Y;
L: Boolean := A = B; -- here predefined "=" on component C is used, not the
-- equality redefined above
generic
type T is private;
--with function "=" (L, R: T) return Boolean is <>;
package P is ...
package P_on_X is new P (X); -- here also predefined "=" on X is used,
-- not the equality redefined above
You have to uncomment the generic parameter function to prevent reemergence.
This whole astonishing rule has been introduced because of compatibility with
Ada 83 (note there were no tagged types in Ada 83 so there reemergence could
safely be avoided).
In Ada 83, it was not possible to redefine "=" without using a trick (I do not
remember the exact way to do it, I never did this; you have to use generics with
the a limited private formal type). When you used this trick to redefine
equality, also the predefined equality reemerged as in the cases above. Thus for
compatibility, we have this rule in Ada 95.
next reply other threads:[~2002-07-24 5:33 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-07-24 5:33 Grein, Christoph [this message]
2002-07-24 22:55 ` Dispatching and generics - language lawyer question Robert A Duff
2002-07-25 15:46 ` Ben Brosgol
2002-07-29 20:38 ` Robert A Duff
2002-07-31 22:52 ` Dmitry A.Kazakov
2002-07-31 20:18 ` Robert A Duff
2002-08-02 1:15 ` Dmitry A.Kazakov
2002-08-01 16:30 ` Hyman Rosen
2002-08-02 23:42 ` Dmitry A.Kazakov
2002-08-02 15:49 ` Hyman Rosen
2002-08-02 17:48 ` Stephen Leake
2002-08-10 3:03 ` Warren W. Gay VE3WWG
2002-08-05 11:15 ` Dmitry A. Kazakov
2002-08-12 12:44 ` Robert Dewar
2002-08-13 2:00 ` Information Systems Annex was " Robert C. Leif
2002-08-13 8:17 ` Robert Dewar
2002-08-13 23:53 ` Information Systems Annex Robert C. Leif
2002-08-13 17:37 ` Information Systems Annex was RE: Dispatching and generics - language lawyer question Keith Thompson
2002-08-13 23:53 ` Robert C. Leif
2002-08-14 8:52 ` Keith Thompson
2002-08-14 21:53 ` Robert C. Leif
2002-08-15 9:31 ` Robert Dewar
2002-08-15 21:54 ` Decimal Floating point was " Robert C. Leif
2002-08-16 6:26 ` Keith Thompson
2002-08-16 16:26 ` Robert C. Leif
2002-08-16 18:17 ` Keith Thompson
2002-08-16 15:26 ` Robert Dewar
2002-08-16 15:29 ` Robert Dewar
2002-08-15 9:26 ` Robert Dewar
2002-08-15 16:17 ` Darren New
2002-08-15 17:25 ` David C. Hoos
2002-08-15 17:31 ` Darren New
2002-08-15 19:59 ` Frank J. Lhota
2002-08-15 17:39 ` tmoran
2002-08-15 19:18 ` Information Systems Annex was RE: Dispatching and generics - Larry Kilgallen
2002-08-15 18:41 ` Hyman Rosen
2002-08-16 15:49 ` Robert Dewar
2002-08-17 6:31 ` Simon Wright
2002-08-17 14:17 ` Robert Dewar
2002-08-15 21:54 ` Decimal Floating types was RE: Information Systems Annex was RE: Dispatching and generics - language lawyer question Robert C. Leif
2002-08-16 15:21 ` Robert Dewar
2002-08-16 16:15 ` Decimal Floating types Warren W. Gay VE3WWG
2002-08-17 10:52 ` Robert Dewar
2002-08-17 14:30 ` Warren W. Gay VE3WWG
2002-08-20 0:26 ` Robert Dewar
2002-08-20 2:35 ` SteveD
2002-08-22 18:15 ` Richard Riehle
2002-08-23 3:23 ` Robert Dewar
2002-08-16 15:47 ` Information Systems Annex (usefulness of Decimal Floats) Warren W. Gay VE3WWG
2002-08-17 10:54 ` Robert Dewar
2002-08-17 14:06 ` Warren W. Gay VE3WWG
2002-08-17 10:56 ` Robert Dewar
2002-08-17 14:12 ` Warren W. Gay VE3WWG
2002-08-17 19:04 ` Robert C. Leif
2002-08-20 0:25 ` Robert Dewar
2002-08-16 15:38 ` Information Systems Annex was RE: Dispatching and generics - language lawyer question Robert Dewar
2002-08-13 22:50 ` Randy Brukardt
2002-08-14 0:02 ` Robert A Duff
2002-07-25 0:40 ` Robert Dewar
-- strict thread matches above, loose matches on Subject: below --
2002-07-22 23:13 Adam Beneschan
2002-07-23 15:42 ` Stephen Leake
2002-07-24 15:37 ` Stephen Leake
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