Re: What would you like in Ada202X?

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Wed, 25 Apr 2012 10:59:02 +0200, Yannick Duch�ne (Hibou57) wrote:

> Le Wed, 25 Apr 2012 10:36:41 +0200, Dmitry A. Kazakov  
> <mailbox@dmitry-kazakov.de> a �crit:
>> 11) Package interfaces, transitive "use." I.e. an ability to make things
>> visible in some package visible in another without repeating all its with
>> and use clauses. And, of course, "use" should imply "with" where
>> applicable.
> Why this one? (I agree with all, but this single one)

Because Ada is a language for software engineering.

It was no problem back in 80s when a project had 10 or so units. It became
a huge problem now with thousands of units especially when generics are
used with instances of packages scattered all over the project. Typically
instances are bound by common parameters, e.g. the actual types used for
formal types. There is no way to put these related instances together in a
third package, make visible what you all need to, and then reuse the
result.

The most simple example is:

   package P is
      package Q is new Foo;
   end P;

There is no means to flatten P making declarations of Q be directly visible
for clients of P. E.g. something like

   package P is
      package Q is new Foo (...);
      use all Q; -- Make things from Q declared directly in P
   end P;

Note that this is a next level of software developing. Instantiations of
some generics is just an implementation detail. The goal is to obtain a new
package of desired properties unconstrained by arbitrary details like
incidental names of instances They should not contaminate the result, e.g.

   package P is
      use all new Foo (...); -- I don't need the instance name
   end P;

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de