From: comar@cs.nyu.edu (Cyrille Comar)
Subject: Re: Mut. Recurs. in Ada9X w/o Breaking Encaps.? (LONG)
Date: 2 Oct 1994 20:33:59 -0400
Date: 1994-10-02T20:33:59-04:00 [thread overview]
Message-ID: <36njhn$o7e@lang8.cs.nyu.edu> (raw)
In-Reply-To: 1994Sep29.014611.20263@swlvx2.msd.ray.com
jgv@swl.msd.ray.com (John Volan) writes:
: can the client do with that pointer? As far as it can see, the Office object
: being pointed to is totally featureless. Oh, sure, it's possible that this
:Office object is really some subclass of Abstract_Office that does have useful
: features, but this information isn't available to the client.The only way the
: client could get to that information would be to use an unchecked conversion
: to change this "opaque" pointer into a pointer to the "non-opaque" Office
: subclass below. (I think folks in the other languages would call this
: "downcasting".) But this practice breaks type-safety!
As far as I know, downcasting is allowed in Ada9x and is type-safe (a check is
performed at run-time) by using a regular conversion not an
unchecked-conversion, so Mark's solution seems very close to what you need.
--
------------------------------------------------------------------------
Cyrille Comar, E-mail: comar@cs.nyu.edu
Gnat Project US phone: (212) 998-3489
next prev parent reply other threads:[~1994-10-03 0:33 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
1994-09-27 16:52 Mut. Recurs. in Ada9X w/o Breaking Encaps.? (LONG) John Volan
1994-09-27 18:48 ` Mark A Biggar
1994-09-29 1:46 ` John Volan
1994-09-29 13:57 ` Tucker Taft
1994-09-29 17:20 ` Bjarne Stroustrup <9758-26353> 0112760
1994-09-30 1:38 ` Tucker Taft
1994-09-30 12:33 ` Bjarne Stroustrup <9758-26353> 0112760
1994-09-29 18:37 ` John Volan
1994-09-29 19:34 ` David Weller
1994-09-30 22:13 ` John Volan
1994-10-02 3:31 ` Andrew Lees
1994-09-30 1:47 ` Tucker Taft
1994-09-30 13:30 ` John Volan
1994-09-29 18:10 ` R. William Beckwith
1994-10-03 0:33 ` Cyrille Comar [this message]
1994-09-28 14:01 ` Norman H. Cohen
1994-09-29 2:12 ` John Volan
1994-09-29 14:01 ` Tucker Taft
1994-09-29 18:37 ` Norman H. Cohen
1994-09-29 9:48 ` Magnus Kempe
1994-09-29 13:10 ` Magnus Kempe
1994-09-29 18:05 ` Tucker Taft
1994-09-30 10:20 ` Mut. Recurs. in Ada9X w/o Breaking Encaps.? Magnus Kempe
1994-09-30 13:22 ` Tucker Taft
1994-10-01 1:24 ` Mut. Recurs. in Ada9X w/o Breaking Encaps.? (LONG) Adam Beneschan
1994-10-01 12:01 ` Magnus Kempe
1994-10-01 18:43 ` Mark A Biggar
1994-10-02 16:41 ` John Volan
1994-10-02 23:33 ` Matt Kennel
1994-10-03 8:07 ` Mut. Recurs. in Ada9X w/o Breaking Encaps.? Magnus Kempe
1994-10-03 12:14 ` Mut. Recurs. in Ada9X w/o Breaking Encaps.? (LONG) Robert I. Eachus
1994-10-04 2:12 ` R. William Beckwith
1994-10-04 16:00 ` John Volan
1994-10-05 11:42 ` Robert I. Eachus
1994-10-05 21:09 ` Matt Kennel
1994-10-03 20:29 ` Harry Koehnemann
1994-09-29 13:35 ` John Volan
1994-09-30 20:27 ` Norman H. Cohen
1994-10-01 1:47 ` John Volan
1994-10-01 20:44 ` Tucker Taft
1994-10-03 11:29 ` Robert I. Eachus
1994-09-30 22:46 ` Matt Kennel
1994-10-01 2:11 ` John Volan
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