Re: ANN: Ada 2005 Math Extensions, 20100810 release

[Simon Wright <simon@pushface.org>]

"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:

> Yes, especially because of two "Extensions". I had immense problems with
> names. Look at this:
>
>    http://www.dmitry-kazakov.de/ada/fuzzy_packages.gif

Gosh!

From a UML background (OK, OK, ...) I'd have the arrows pointing the
other way ('depends on' rather than 'is used in' or 'supports').

> Somewhere down deep the hierarchy the user starts to become
> incomprehensive error messages upon instantiation within the
> generic(!) bodies. It is practically impossible to understand what is
> wrong, is it a compiler bug (in GNAT case) or something else. For the
> user it would be a nightmare to fight this.

I think I've come across a GNAT bug here .. I dont think it's allowed
for a generic to compile but the instantiation not!

> Another rule of thumb (I don't know if this is going to be fixed in
> Ada 2012), is that a child should always rename formal generic
> arguments in its specifications. Under certain circumstances, usually
> in children, they might become unavailable. I mean this:
>
> generic
>    with package P is new Generic_P (<>);
> package Generic_S is
>    package P_Of renames P; -- You will need this!
>
> Sometimes you need to "rename" formal types as well:
>
> generic
>    type Foo is ...
> package Generic_S is
>    subtype Foo_Of is Foo; -- What a mess!

I've more often come across the latter.

Could consider

generic
   type Formal_Foo is ...
package Generic_S is
   subtype Foo is Formal_Foo;