Re: how to import a package

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

On 11 Dec 2006 06:19:37 -0800, markww wrote:

> I'm sorry, I still don't understand how to just pass a generic through
> as a parameter!

No way. It is incorrect in either C++ or Ada. A generic is never a [normal]
parameter. It can only be a *generic* parameter of another generic thing.

Answering less formally, what you want to achieve is probably this:

generic
   type T is private;
package Generic_List is
   type Node;
   type Node_Ptr is access Node;
   type Node is limited record -- We don't copy nodes
      Data : T;                -- The data in the node
      Prev : Node_Ptr;         -- Previous node, else null
      Next : Node_Ptr;         -- Next node, else null
   end record;
   -- Operations defined on the nodes follow:
   --
   -- Add a new node to the list after the node indicated by
   -- the parameter After.
   --
   procedure Add (After : Node_Ptr; Data : T);
end Generic_List;
----------------------------------------------
package body Generic_List is
   procedure Add (After : Node_Ptr; Data : T) is
      New_Node : Node_Ptr := new Node;
   begin
      New_Node.Data := Data;
      New_Node.Prev := After;
      New_Node.Next := After.Next;
      if After.Next /= null then
         After.Next.Prev := New_Node;
      end if;
      After.Next := New_Node;
   end Add;
end Generic_List;
-------------------------------------------

1. T is a generic formal parameter of the package Generic_List.

2. Data is normal parameter of a procedure Add.

3. The procedure Add is not generic

4. When Generic_List is instantiated this instance will be a normal package
with a normal procedure Add in it.

5. This Add will be defined on the actual type specified for T during the
instantiation.

For example:

   package List_Of_Integers is new Generic_List (T=>Integer);
   
-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de