From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,FREEMAIL_FROM
	autolearn=ham autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,87077e61d6b3095b
X-Google-Attributes: gid103376,public
X-Google-ArrivalTime: 2003-12-22 15:23:21 PST
Path: 
 archiver1.google.com!news1.google.com!sn-xit-02!sn-xit-01!sn-post-01!supernews.com!corp.supernews.com!not-for-mail
From: cl1motorsports <cwlambert76@yahoo.com>
Newsgroups: comp.lang.ada
Subject: Re: how do i implement double-dispatching?
Date: Mon, 22 Dec 2003 18:04:52 -0500
Organization: Posted via Supernews, http://www.supernews.com
Message-Id: <pan.2003.12.22.23.04.46.656829@yahoo.com>
User-Agent: Pan/0.14.2 (This is not a psychotic episode. It's a cleansing
 moment of clarity. (Debian GNU/Linux))
References: <pan.2003.12.17.18.08.34.122050@yahoo.com>
 <pan.2003.12.20.06.27.10.68359@yahoo.com>
 <pan.2003.12.22.21.41.43.388128@yahoo.com>
 <mailman.160.1072133388.31149.comp.lang.ada@ada-france.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 8bit
X-Complaints-To: abuse@supernews.com
Xref: archiver1.google.com comp.lang.ada:3725
Date: 2003-12-22T18:04:52-05:00
List-Id: <comp.lang.ada>

On Mon, 22 Dec 2003 17:49:41 -0500, Stephen Leake wrote:

> cl1motorsports <cwlambert76@yahoo.com> writes:
> 
>> Okay. now it works when the Visitor type, Visit() procedures and the
>> Accept_Visitor() procedure is in a separate package from the parse tree.
>> but when i try to combine the 2 into one package i get
>> an error about multiple dispatching on all of the Visit() procedures.
>> what is my scope issue with being in the same package that doesn't apply
>> to them being in 2 packages?
> 
> In general, you will find that the Ada rules encourage putting things
> in different packages. This is a Good Thing :).
But in this case there is no point of having a visitor with out a tree to
visit or a parse tree with no visitor to run operations on it. Currently
to use this in a program i have to do this:

with Parse_Tree_Pkg; use Parse_Tree_Pkg;
with Abstract_Visitor_Pkg; use Abstract_Visitor_Pkg;
with Interpret_Tree; use Interpret_Tree;

a person using the interpret_Tree package having to know that it's
created from an abstract visitor package exposes implementation and that's
what I am trying to avoid. The user should only have to do:

with parse_tree_pkg; use parse_tree_pkg;
with Interpret_Tree; use interpret_Tree;

am i correct on this or am i missing something?


> 
> Sometimes child packages work better.