Re: Generic package parameters not externally visible : what's the rational ?

["Jeffrey R. Carter" <spam.jrcarter.not@spam.acm.org>]

Hibou57 (Yannick Duch�ne) wrote:
> 
> One good reason to miss it, is when a package A has another package B
> in its formal parameters and this formal package parameter (B) is it
> self generic, and A needs to use some type which were given to
> instantiate the package B. This is an example case where the parameter
> which were used to instantiate a package, are not accessible from a
> point they are needed (if P instantiated B, of course P has access to
> parameters used to instantiate B, but this does not help A, it if ever
> itself also need these).

But Ada allows a generic to reference the unknown generic parameters of its 
formal package parameters. See ARM 12.7.

> To come back to the first point : one other good reason apart of a
> generic package having another generic in its parameters, is when a
> generic package B may also be instantiated in a package A, which will
> then be use in another package C, which does not have direct access to
> the parameters used to instantiate the package (let say it was in a
> third package which A deeply rely on one, but not C). Then, one of the
> more natural way to access these, if ever needed for other stuff in C,
> is the generic package instance B itself.

Then C clearly has a dependency on this 4th pkg (shall we call it D?), and that 
dependency should be made explicit, by including "with D;" on C.

-- 
Jeff Carter
"We'll make Rock Ridge think it's a chicken
that got caught in a tractor's nuts!"
Blazing Saddles
87