Re: Renaming of procedures in a generic instantiation

[Gene <gene.ressler@gmail.com>]

On Sep 26, 4:45 am, Stephen Leake <stephen_le...@stephe-leake.org>
wrote:
> Gene <gene.ress...@gmail.com> writes:
> > I'm confused about an aspect of renaming. It boils out to this little
> > example:
>
> > with Ada.Containers.Ordered_Sets;
>
> > package Foo is
>
> >   type Queue is private;
>
> >   procedure Add(Q : in out Queue; Item : in Integer);
>
> >   function Is_Empty(Q : Queue) return Boolean;
>
> > private
>
> >   package Queues is
> >     new Ada.Containers.Ordered_Sets(Integer, "<", "=");
> >   type Queue is new Queues.Set with null record;
>
> All primitive operations of Queues.Set are implicitly declared here,
> with Queue replacing Queues.Set; that includes Set and Is_Empty. That's
> what derived types are for.
>
> > end Foo;
>
> > package body Foo is
>
> >    procedure Add(Q : in out Queue; Item : in Integer)
> >       renames Insert;
>
> This 'Insert' resolves to Foo.Insert (Container : in out Foo.Queue; ...);
>
> >    function Is_Empty(Q : Queue) return Boolean
> >       renames Queues.Is_Empty;
>
> Queues.Is_Empty expects a Constainer of type Foo.Queues.Set, not Foo.Queue.
>
> If you replace
>
>    type Queue is new Queues.Set with null record;
>
> with
>
>    subtype Queue is Queues.Set;
>
> Then the Add renames will fail (because the primitive operations are not
> derived), and the Is_Empty will succeed.
>
> --
> -- Stephe- Hide quoted text -
>
> - Show quoted text -

Thanks.  This is one variation I tried.  There is first a compiler
complaint that this private subtype declaration doesn't match the
earlier public "type Queue is private".  I take it there is no way at
all to declare a type private and then specify it in the private
section as a subtype?