Re: Mutually dependent private types

[Geoff Bull <gbull@acenet.com.au>]

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