Re: generics in Ada 83

["REH" <spamjunk@stny.rr.com>]

Martin Dowie wrote:
> REH wrote:
> > Martin Dowie wrote:
> >
> >>REH wrote:
> >>
> >>>Is there a way to define a default for the with'd procedure in the
> >>>following example in Ada 83:
> >>>
> >>>generic
> >>>    type X is private;
> >>>    with procedure Y(Z : in X);
> >>>package Foo;
> >>>
> >>>I want to define a default for Y, but how can I without knowing X?
> >>>
> >>>I have a generic package that has several with'd procedures, but
> >>>depending on what services the package provides are use, only a few of
> >>>the procedures may need to be defined.  I'd like to just default the
> >>>unused ones to stubs.
> >>
> >>Same as Ada95:
> >>
> >>generic
> >>   type X is private;
> >>   with procedure Y (Z : X) is <>;
> >>package Foo is
> >>end Foo;
> >>
> >>Or do you mean you want the compiler to magically insert a 'null' procedure
> >>if there isn't a matching procedure Y for whatever type X happens to be? If
> >>that's the case you can't do that. There has to be some procedure (even one
> >>that's only 'begin null end;') for each type.
> >>
> >>Cheers
> >>
> >>-- Martin
> >
> >
> > defining it with a box won't work.  There would have to a procedure
> > already defined.  What I want is something like:
> >
> > generic
> >     type X is private;
> >     with procedure Y(Z : in X) is P;
> > package Foo
> >
> >
> > but of course P must already take into account X.  With '95 I think I
> > could just with a generic package containing the stubs, but I can
> > figure out a way in '83.
>
> Yes, how can you have 'P' know which X?
>
> The best I can see is:
>
> package A is
>     type A_T is private;
>     procedure Y (Z : A_T);
> private
>     type A_T is new Integer;
> end A;
>
> generic
>     type X is private;
>     with procedure Y (Z : X) is <>;
> package B is
> end B;
>
> with A; use A;
> with B;
>
> package C is
>     new B (A_T);  -- Picks up 'Y' by default
>
> Cheers
>
> -- Martin

That seems reasonable.  Two questions:
1) If I have Y1 through Yn, Do I define the ones I care about when I
instantiate B or do I define then in C, before B?
2) is there a way to avoid having to include A?