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From: stt@dsd.camb.inmet.com (Tucker Taft)
Subject: Re: Mut. Recurs. in Ada9X w/o Breaking Encaps.? (LONG)
Message-ID: <Cwx6At.47C@inmet.camb.inmet.com>
Keywords: Ada 9X, C++, object-oriented, Law of Demeter
Sender: news@inmet.camb.inmet.com
Organization: Intermetrics, Inc.
References: <1994Sep27.165203.9192@swlvx2.msd.ray.com>
 <1994Sep29.014611.20263@swlvx2.msd.ray.com> <Cww9GL.EI@inmet.camb.inmet.com>
 <1994Sep29.183749.7489@swlvx2.msd.ray.com>
Date: Fri, 30 Sep 1994 01:47:16 GMT
Xref: bga.com comp.lang.ada:6336 comp.object:6923 comp.lang.c++:31101
Date: 1994-09-30T01:47:16+00:00
List-Id: <comp.lang.ada>

In article <1994Sep29.183749.7489@swlvx2.msd.ray.com>,
John Volan <jgv@swl.msd.ray.com> wrote:

>STT>    if Y = null or else Y.all in T1'Class then ...
>STT>           -- Checks that PT1(Y) will succeed, before
>STT>	   -- attempting it.
>STT>
>
>Er, I think you meant:
>
>        if Y /= null and then Y.all in T1'Class then ...
>
>Or maybe, if you wanted to cover the contrary case first:
>
>        if Y = null or else Y.all not in T1'Class then ...

No, actally I meant what I wrote ;-).  If Y = null, then the conversion
always succeeds, since all (named) access (sub)types include null
as a legal value of the (sub)type.

>I am an unabashed fanatic of the 1 Package = 1 Type = 1 Class approach, and
>making that approach workable was the whole point of this thread.  

I'm not.  In my view packaging is an additional dimension
of flexibility that should be used (but not abused ;-).
Packages are for grouping logically related entities,
and it is fine if a single package includes two closely linked types.

But I understand some of the advantages of the other approach as well...
Vive la difference (but not on *my* project ;-).

>-- John Volan
>--                  Company             => "Raytheon Missile Systems Division",
>--                  E_Mail_Address      => "jgv@swl.msd.ray.com",

-Tucker Taft   stt@inmet.com
Intermetrics, Inc.