Re: OO Style with Ada Containers

[Matthew Heaney <mheaney@on2.com>]

On Nov 27, 2:31 pm, Georg Bauhaus <rm.tsoh+bauh...@maps.futureapps.de>
wrote:
> On Mon, 2007-11-26 at 12:29 -0800, Matthew Heaney wrote:
> > generic
> >   with procedure Process (Word : String);
> > procedure Generic_Scan (File : File_Type);
>
> Hm. Isn't a local variable together with a local function
> modifying the local variable a viable option?

Yes, that local function would be the generic actual in my example.


> There is no
> 'Access then, but only "access" in a logical sense. The
> variable/constant is not passed to the function but still
> visible and accessible to the function.

Yes, of course.


> One could even wrap
> them both in the same local package. The package might not
> establish coupling in a type, but nevertheless it establishes
> coupling of things that belong together.

I'm not sure I was clear here.  I meant:

package Scanner is
  generic
     with procedure Process (Word : String);
  procedure Generic_Scan (File : File_Type);
end Scanner;

Actually, in Ada05 you don't need the generic at all:

package Scanner is
  procedure Scan
    (File : File_Type,
     Process : not null access Process (Word : String));
end Scanner;

Then you could say:

declare
   M : Map;

   procedure Insert_Word (Word : String) is
      procedure Inc (Count : in out Natural) is
      begin
         Count := Count + 1;
      end;

      C : Cursor;
      B : Boolean;
   begin
      M.Insert (Word, 0, C, B);
      M.Update_Element (C, Inc'Access);
   end;

   F : File_Type;
begin
   Open (F, ...);
   Scanner.Scan (F, Insert_Word'Access);
   ... -- do something with map
end;