Re: Subprogram Renaming

[Jonas Nygren <ehsjony@ehs.ericsson.se>]

Norman H. Cohen wrote:
> 
> In article <4kgde6$q8t@watnews1.watson.ibm.com>, I wrote:
> 
> |>                                             This capability is especially
> |> useful when a subprogram is implemented using generic instantiation.
> 
> Renaming-as-body is also useful in conjunction with derived subprograms.
> Here's a variation on my previous example:

I have been experimenting with such a construct for some months but always
encountered some new problem. My example code is similar to Normans but
instead of Integer_Dequeues I have Generic_Dequeues and Generic_Stacks.

My problem is how to handle a subprogram with the same name for Dequeue_Type 
and Stack_Type, e.g. Remove_All. I never managed to figure out how to handle
the renaming. Perhaps somebody here can help me.

I intersperse the added code in Normans example below.

Of course I could introduce a dummy type with the common names marked
to distinguish them from the intended name. Deque_Type and Stack_Type
then derives from this 'dummy type'.

Another note: As mentioned above my code uses generics while Norman's does
not. Is there a catch? I encountered a problem with Gnat where it worked
without generics but not with. I have reported it but have not heard anything
from ACT (I am not on support contract :-). Is there Ada legal problems
with adding generics to these example packages?

/jonas

> 
>    package Integer_Dequeues is
>       type Dequeue_Type is private;
>       procedure Add_To_Front (Dequeue: in out Dequeue_Type; Item: in Integer);
>       procedure Add_To_Back (Dequeue: in out Dequeue_Type; Item: in Integer);
>       procedure Remove_From_Front
>          (Dequeue: in out Dequeue_Type; Item: out Integer);
>       procedure Remove_From_Back
>          (Dequeue: in out Dequeue_Type; Item: out Integer);

       procedure Remove_All (Dequeue: in out Dequeue_Type);

>    private
>       type Dequeue_Type is ...;
>    end Integer_Dequeues;
> 
>    with Integer_Dequeues;
>    package Integer_Stacks is
>       type Stack_Type is private;
>       procedure Push (Stack: in out Stack_Type; Item: in Integer);
>       procedure Pop (Stack: in out Stack_Type; Item: out Integer);

       procedure Remove_All (Stack: in out Stack_Type);

>    private
>       use Integer_Dequeues;
>       type Stack_Type is new Dequeue_Type;
>       procedure Push (Stack: in out Stack_Type; Item: in Integer)
>          renames Add_To_Front;
>       procedure Pop (Stack: in out Stack_Type; Item: out Integer)
>          renames Remove_From_Front;

       procedure Remove_All (Stack: in out Stack_Type)
          renames Remove_All; -- Does not work, 
                              -- Gnat e.g. creates a recursive call (reported)

>    end Integer_Stacks;
> 
> The subprograms being renamed are the inherited subprograms
> 
>    procedure Remove_From_Front
>       (Dequeue: in out Stack_Type; Item: out Integer);
> 
>    procedure Remove_From_Back
>       (Dequeue: in out Stack_Type; Item: out Integer);
> 
> implicitly declared after the derived-type declaration in the private
> part.
> 
> Because a renaming declaration acting as a subprogram declaration is
> allowed in the package declaration, Integer_Stacks does not even need a
> package body!
> 
> --
> Norman H. Cohen    ncohen@watson.ibm.com

-- 

-------------------------------------------------------
--    Jonas Nygren
--    ehsjony@ehs.ericsson.se
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