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=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID
	autolearn=no autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,56dbd715fa74735a
X-Google-Attributes: gid103376,public
From: Geoff Bull <gbull@acenet.com.au>
Subject: Re: Mutually dependent private types
Date: 1998/05/30
Message-ID: <356F8561.A863216A@acenet.com.au>#1/1
X-Deja-AN: 357851241
Content-Transfer-Encoding: 7bit
References: <6k25ra$6j7$1@nnrp1.dejanews.com>
 <matthew_heaney-ya023680002105982333070001@news.ni.net>
 <3565B105.9BFB4788@ac3i.dseg.ti.com>
 <matthew_heaney-ya023680002205981805440001@news.ni.net>
 <356B226F.EF05E927@ac3i.dseg.ti.com> <m3d8d08yk6.fsf@mheaney.ni.net>
 <356C8A02.44354B09@ac3i.dseg.ti.com> <m3g1hvs1u3.fsf@mheaney.ni.net>
 <356E09A1.B493FE89@ac3i.dseg.ti.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Organization: Telstra Internet Browse Server
Newsgroups: comp.lang.ada
Date: 1998-05-30T00:00:00+00:00
List-Id: <comp.lang.ada>


John Volan wrote:
>>Matthew Heaney wrote:

[snip]

> > So now when he sees this
> >
> > with type P.T;
> >

[snip]

> > I don't know what to do really.  Maybe a pragma be better:
> >
> > with P;
> > pragma Mutual (P);
> > package Q is

> It seems to me that if there's a mutual spec dependency going on between
> P and Q, then the "with" clause here is already illegal according to
> Ada95's language rules.  So what exactly would this "Mutual" pragma
> mean?  "I know the with clause is illegal, but ignore that and pretend
> to be a different language"? :-)  What about Ada95's run-time
> elaboration mechanism?  When would the elaboration code for the specs of
> packages P and Q get executed? In what order?


Isn't this whole thread about changing the language?
Otherwise, put up with the language and use Cohen or similar method,
end of thread.

I agree that providing the occasional extra package to resolve circular
dependencies is a pain. However this is probably less painful than working
on poorly designed code that has used "pragma Mutual" or "with type"
all through it.

How does a compiler that uses a non source based compilation library
"with" a package that hasn't been compiled yet?
(i.e. would allowing circular dependencies introduce a big headache
for just about every Ada compiler, except for Gnat?)

==========================================
Geoff Bull
Murray Bull Information Technology Pty Ltd  ACN 056 703 274