From: Tucker Taft <stt@averstar.com>
Subject: Re: Elimination of "use" clauses
Date: 1999/07/23
Date: 1999-07-23T00:00:00+00:00 [thread overview]
Message-ID: <3798E50D.100976B@averstar.com> (raw)
In-Reply-To: 7n0icj$1je@dfw-ixnews21.ix.netcom.com
Richard D Riehle wrote:
>
> In article <dale-1807991510420001@192.168.0.2>,
> dale@cs.rmit.edu.au (Dale Stanbrough) wrote:
>
> >Export directives -could- do it (and it is not a bad idea at all),
> >but we shouldn't forget that Ada already has the ability to export
> >-just- the operators we want, and it's called using a private type
> >and only advertising the appropriate operations.
>
> I fully agree that the private type is underused for this purpose.
> However, you will need to declare the arithmetic and logical
> operators for a private type. This is the ideal place for using
> a nested Ops package to restrict the set of operators to exactly
> those you want available in your design.
>
> package P is
> type T is private;
> -- operations on T
> package Ops is
> function ">" (L, R : T) return Boolean;
> function "+" (L, R : T) return T;
> end Ops;
> end P;
>
> Now, use P.Ops makes sense and exports only the operators the
> designer feels are appropriate but still restricts them to an
> Ops package. Of course, if they were not in the nested Ops package,
> one could still invoke the "use type" clause. In the end, I think it
> it will be a matter of preference rather than a matter of which is
> better.
The major difference is that the operators are no longer inherited
as part of a derived type definition.
In general, the "ops" package idiom was an Ada 83 work-around.
Now that we have use-type, I recommend against proliferating it further.
There are ways to work with a language, and ways to fight against it.
In Ada 95, the "use type" is definitely the language-defined way to
deal with operator visibility. In Ada 83, there really wasn't
any particularly good language support for operator visibility,
so various approaches were adopted.
> ...
> Richard Riehle
> richard@adaworks.com
> http://www.adaworks.com
>
--
-Tucker Taft stt@averstar.com http://www.averstar.com/~stt/
Technical Director, Distributed IT Solutions (www.averstar.com/tools)
AverStar (formerly Intermetrics, Inc.) Burlington, MA USA
next prev parent reply other threads:[~1999-07-23 0:00 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-07-01 0:00 Elimination of "use" clauses Dr. Neil C. Audsley
1999-07-01 0:00 ` Joe Wisniewski
1999-07-01 0:00 ` Samuel T. Harris
1999-07-01 0:00 ` czgrr
1999-07-01 0:00 ` Ted Dennison
1999-07-02 0:00 ` czgrr
1999-07-02 0:00 ` Ted Dennison
1999-07-02 0:00 ` Robert Dewar
1999-07-02 0:00 ` Samuel T. Harris
1999-07-02 0:00 ` Robert Dewar
1999-07-08 0:00 ` R. Tim Coslet
1999-07-09 0:00 ` Robert Dewar
1999-07-09 0:00 ` tmoran
[not found] ` <7ltl2q$mog$1@nnrp1.deja.com>
1999-07-08 0:00 ` Michael F. Yoder
1999-07-09 0:00 ` Richard D Riehle
1999-07-09 0:00 ` Marin David Condic
1999-07-09 0:00 ` Michael F. Yoder
1999-07-09 0:00 ` Robert Dewar
1999-07-09 0:00 ` Michael F. Yoder
1999-07-14 0:00 ` Tucker Taft
1999-07-09 0:00 ` Dale Stanbrough
1999-07-12 0:00 ` Robert Dewar
1999-07-12 0:00 ` Ted Dennison
1999-07-10 0:00 ` Simon Wright
1999-07-12 0:00 ` Robert Dewar
1999-07-02 0:00 ` Ed Falis
1999-07-03 0:00 ` Joe Wisniewski
1999-07-03 0:00 ` Ed Falis
1999-07-03 0:00 ` Keith Thompson
1999-07-13 0:00 ` Peter Amey
1999-07-02 0:00 ` Ted Dennison
1999-07-02 0:00 ` Ed Falis
1999-07-02 0:00 ` Robert Dewar
[not found] ` <7ltus1$ah1@dfw-ixnews19.ix.netcom.com>
1999-07-13 0:00 ` Robert A Duff
1999-07-18 0:00 ` Richard D Riehle
1999-07-18 0:00 ` jerry
1999-07-19 0:00 ` Vladimir Olensky
1999-07-20 0:00 ` Richard D Riehle
1999-07-20 0:00 ` jerry
1999-07-20 0:00 ` Opaque Types (was Elimination of "use" clauses) David C. Hoos, Sr.
1999-07-18 0:00 ` Elimination of "use" clauses Dale Stanbrough
1999-07-20 0:00 ` Richard D Riehle
1999-07-19 0:00 ` Brian Rogoff
1999-07-20 0:00 ` Robert Dewar
1999-07-20 0:00 ` Brian Rogoff
1999-07-21 0:00 ` Robert Dewar
1999-07-21 0:00 ` Brian Rogoff
1999-07-22 0:00 ` Robert Dewar
1999-07-22 0:00 ` Brian Rogoff
1999-07-22 0:00 ` Robert Dewar
1999-07-22 0:00 ` Brian Rogoff
1999-07-21 0:00 ` Ted Dennison
1999-07-21 0:00 ` Robert A Duff
1999-07-21 0:00 ` Robert Dewar
1999-07-21 0:00 ` Robert A Duff
1999-07-21 0:00 ` Michael F. Yoder
1999-07-21 0:00 ` Robert A Duff
1999-07-23 0:00 ` Tucker Taft [this message]
1999-08-03 0:00 ` Richard D Riehle
1999-07-20 0:00 ` David Kristola
1999-07-19 0:00 ` Ted Dennison
1999-07-19 0:00 ` Tucker Taft
1999-07-19 0:00 ` Ted Dennison
1999-07-02 0:00 ` Stephen Leake
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