From: jsa@alexandria (Jon S Anthony)
Subject: Re: Syntax for tagged record types (was Re: Not intended for use in medical,)
Date: 1997/05/25
Date: 1997-05-25T00:00:00+00:00 [thread overview]
Message-ID: <JSA.97May24213835@alexandria> (raw)
In-Reply-To: 33867D87.21BA@sprintmail.com
In article <33867D87.21BA@sprintmail.com> "John G. Volan" <johnvolan@sprintmail.com> writes:
> Just so folks won't be confused, what Jon's referring to here are
> ordinary Ada functions that happen to return a value of a given type,
Right.
> > For limited types, the only way around this is to hide them behind
> > access types for them.
>
> Right, when you deal with true object-oriented abstractions (as opposed
> to value-oriented abstract data types), you inevitably have to invoke
> reference semantics and the identity-vs-state issue.
>
> Here's a pattern I like to use for object-oriented types:
>
> type Some_Object_Type (<>) is tagged limited private;
> type Some_Object_Access_Type is access all Some_Object_Type'Class;
>
> function Make_Some_Object (... from one set of parameters ...)
> return Some_Object_Access_Type;
<...>
Exactly! Right on the mark.
> (1) Some_Object_Type is limited, so assignment can't be used to casually
Absolutely.
> (3) Some_Object_Type has an unknown discriminant part, so a direct
> declaration for an object of this type is illegal:
>
> Some_Object : Some_Object_Type; -- compiler error! indefinite type!
Absolutely!
> And the users can't get around this by trying to initialize the object
> to something -- because it's a limited type, so assignment is illegal.
Exactly!
> > Then things again work just fine - except for
> > storage management issues. Hence, the need for GC. Limited types are
> > really extremely useful. Unfortunately, much of this is lost without
> > GC support.
>
> Agreed.
Well, with some luck this will not be so much an issue by some time
this summer! :-) If I could only get out from under this proposal
writing rubbish...
/Jon
--
Jon Anthony
Organon Motives, Inc.
Belmont, MA 02178
617.484.3383
jsa@organon.com
next prev parent reply other threads:[~1997-05-25 0:00 UTC|newest]
Thread overview: 120+ messages / expand[flat|nested] mbox.gz Atom feed top
1997-04-23 0:00 Not intended for use in medical, Robert C. Leif, Ph.D.
1997-04-24 0:00 ` J. Florio
1997-04-25 0:00 ` Kevin Cline
1997-04-25 0:00 ` Robert Dewar
1997-04-25 0:00 ` Ken Garlington
1997-04-28 0:00 ` John Apa
1997-04-28 0:00 ` John M. Mills
1997-04-30 0:00 ` Larry Kilgallen
1997-05-02 0:00 ` Nick Roberts
1997-04-28 0:00 ` Robert Dewar
1997-04-29 0:00 ` Kaz Kylheku
1997-04-30 0:00 ` John Apa
[not found] ` <3367CE1E.5ED1@die_spammer.dasd.honeywell.com>
1997-05-01 0:00 ` Kaz Kylheku
1997-05-03 0:00 ` Simon Wright
1997-05-04 0:00 ` Kaz Kylheku
1997-05-04 0:00 ` Robert Dewar
1997-05-04 0:00 ` Richard Kenner
1997-05-05 0:00 ` Kaz Kylheku
1997-05-06 0:00 ` Kaz Kylheku
1997-05-06 0:00 ` Robert A Duff
1997-05-07 0:00 ` Robert Dewar
1997-05-08 0:00 ` Robert A Duff
1997-05-09 0:00 ` Robert I. Eachus
1997-05-11 0:00 ` Robert Dewar
1997-05-11 0:00 ` Matthew Heaney
1997-05-12 0:00 ` Robert Dewar
1997-05-12 0:00 ` Matthew Heaney
1997-05-13 0:00 ` Jon S Anthony
1997-05-13 0:00 ` Matthew Heaney
1997-05-14 0:00 ` Robert Dewar
1997-05-14 0:00 ` Robert Dewar
1997-05-14 0:00 ` Robert Dewar
1997-05-14 0:00 ` Nick Roberts
1997-05-14 0:00 ` Robert Dewar
1997-05-15 0:00 ` W. Wesley Groleau (Wes)
1997-05-12 0:00 ` Robert I. Eachus
1997-05-13 0:00 ` Robert Dewar
1997-05-14 0:00 ` Nick Roberts
1997-05-14 0:00 ` Robert Dewar
[not found] ` <01bc6182$30e3a7c0$LocalHost@xhv46.dial.pipex.com>
1997-05-16 0:00 ` Robert A Duff
1997-05-16 0:00 ` Robert I. Eachus
1997-05-18 0:00 ` Nick Roberts
1997-05-18 0:00 ` Matthew Heaney
1997-05-19 0:00 ` Robert A Duff
1997-05-19 0:00 ` Robert I. Eachus
1997-05-19 0:00 ` Matthew Heaney
1997-05-20 0:00 ` Nick Roberts
1997-05-20 0:00 ` Matthew Heaney
1997-05-21 0:00 ` Dale Stanbrough
1997-05-16 0:00 ` Robert Dewar
1997-05-08 0:00 ` Kaz Kylheku
1997-05-08 0:00 ` Robert Dewar
1997-05-09 0:00 ` Kaz Kylheku
1997-05-12 0:00 ` W. Wesley Groleau (Wes)
1997-05-12 0:00 ` John G. Volan
1997-05-14 0:00 ` Nick Roberts
1997-05-14 0:00 ` Robert Dewar
1997-05-14 0:00 ` Jeff Carter
[not found] ` <dewar.863632434@merv>
1997-05-15 0:00 ` Kaz Kylheku
1997-05-18 0:00 ` Robert Dewar
1997-05-15 0:00 ` Kaz Kylheku
1997-05-08 0:00 ` John G. Volan
1997-05-10 0:00 ` Robert Dewar
1997-05-10 0:00 ` John G. Volan
1997-05-11 0:00 ` Robert Dewar
1997-05-11 0:00 ` John G. Volan
1997-05-11 0:00 ` Robert Dewar
1997-05-11 0:00 ` John G. Volan
1997-05-11 0:00 ` Robert A Duff
1997-05-12 0:00 ` Robert Dewar
1997-05-12 0:00 ` John G. Volan
1997-05-12 0:00 ` John G. Volan
1997-05-12 0:00 ` Robert Dewar
1997-05-17 0:00 ` Robert I. Eachus
[not found] ` <dewar.863877808@merv>
1997-05-17 0:00 ` Robert Dewar
1997-05-17 0:00 ` Jon S Anthony
1997-05-21 0:00 ` Syntax for tagged record types (was Re: Not intended for use in medical,) Ben Brosgol
1997-05-20 0:00 ` Matthew Heaney
1997-05-21 0:00 ` Syntax for tagged record types and class types Mats Weber
1997-05-21 0:00 ` Matthew Heaney
1997-05-22 0:00 ` Mats Weber
1997-05-27 0:00 ` Tucker Taft
1997-05-30 0:00 ` Mats.Weber
1997-05-22 0:00 ` Samuel A. Mize
1997-05-22 0:00 ` Samuel A. Mize
1997-05-23 0:00 ` Mats Weber
1997-05-21 0:00 ` Syntax for tagged record types (was Re: Not intended for use in medical,) Jon S Anthony
1997-05-21 0:00 ` Matthew Heaney
1997-05-22 0:00 ` Robert I. Eachus
1997-05-25 0:00 ` Matthew Heaney
1997-05-28 0:00 ` Robert I. Eachus
1997-05-23 0:00 ` Jon S Anthony
1997-05-23 0:00 ` Matthew Heaney
1997-05-25 0:00 ` Jon S Anthony
1997-05-28 0:00 ` Syntax for tagged record types (was Re David Kristola
1997-05-23 0:00 ` Syntax for tagged record types (was Re: Not intended for use in medical,) Simon Wright
[not found] ` <mheaney-ya023680002005972314260001@news.ni.net <mheaney-ya023680002105972302430001@news.ni.net>
1997-05-22 0:00 ` Robert A Duff
1997-05-22 0:00 ` John G. Volan
1997-05-23 0:00 ` Matthew Heaney
1997-05-23 0:00 ` Jon S Anthony
1997-05-23 0:00 ` Matthew Heaney
1997-05-25 0:00 ` Robert Dewar
1997-05-25 0:00 ` Jon S Anthony
1997-05-27 0:00 ` Ray Blaak
1997-05-23 0:00 ` John G. Volan
1997-05-24 0:00 ` Robert A Duff
1997-05-24 0:00 ` Matthew Heaney
1997-05-28 0:00 ` Robert I. Eachus
1997-05-25 0:00 ` Jon S Anthony [this message]
1997-05-23 0:00 ` Jon S Anthony
1997-05-12 0:00 ` Not intended for use in medical, John G. Volan
1997-05-12 0:00 ` Language Design Mistakes (was "not intended...") W. Wesley Groleau (Wes)
1997-05-13 0:00 ` Robert Dewar
1997-05-13 0:00 ` Robert A Duff
1997-05-14 0:00 ` Robert Dewar
1997-05-13 0:00 ` W. Wesley Groleau (Wes)
1997-05-07 0:00 ` Not intended for use in medical, Kaz Kylheku
1997-05-08 0:00 ` Robert A Duff
1997-05-04 0:00 ` Robert Dewar
1997-05-04 0:00 ` Richard Kenner
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