Re: Ada.Locales pseudo-string types

[Robert A Duff <bobduff@shell01.TheWorld.com>]

Marius Amado-Alves <amado.alves@gmail.com> writes:

> I took the chance to learn subtype aspect clauses, and changed Ada_Locales thus:

Predicates are my favorite new feature of Ada 2012!

>    subtype Country_Code is String (1 .. 2)
>       with Static_Predicate =>
>          Country_Code (1) in 'A' .. 'Z' and
>          Country_Code (2) in 'A' .. 'Z';

Or "type Country_Code is String (1 .. 2) with ...".

As has been noted, it should be Dynamic_Predicate.  Or in GNAT,
you can use just "with Predicate =>", but that's not standard.

It's a bug that GNAT accepts it as a Static_Predicate.
If you report the bug, AdaCore will fix it.  If you
are a supported customer, we will fix it quickly.

> (1) It seems the compiler accepts the type name, in the aspect clause,
> as a representative of a value of the type. I could not find this
> documented in the RM.

Look up "current instance".  For types, this concept has been around
since Ada 83.  In Ada 2012, it works for subtypes, too.

> (2) The aspect clause does not seem to have effect. The following code
> compiles and runs normally.
>
>    CC : Ada_Locales.Country_Code := "34";

It works for me, using the latest compiler.  Did you remember to turn
on checking of assertions, for example using the -gnata switch?

- Bob