Re: Access type to member procedure of instance (Object Oriented programming in Ada)

[Brian Drummond <brian@shapes.demon.co.uk>]

On Mon, 19 Nov 2012 11:39:03 +0000, Brian Drummond wrote:

> On Mon, 19 Nov 2012 01:59:42 -0800, ake.ragnar.dahlgren wrote:
> 
>> Not sure if this has already been discussed but: Is it possible to
>> define a pointer to a member procedure of an instance?
> 
> Yes.

>> Is it possible to create a parameterless access type to the
>> Message.Print procedure? The following application refuses to compile:
> 
> Message.Print is not parameterless, it is identical to Print(Message)
> so ... no.

Okay. I am astonished!
But I am more than happy to withdraw the above "no".

- Brian

--------------------------------------------------------
with Some_Package;

procedure Main is
   Message : Some_Package.Message_Type;

   procedure P renames Message.Print;

   Method_Ref : access procedure := P'access;

begin
   Message.Print;
   P;
   Method_Ref.all;
end Main;
--------------------------------------------------------

./main
Hello
Hello
Hello

And just for completeness...
--------------------------------------------------------
package Some_Package is

   type Message_Type is tagged null record;
   
   procedure Print(Message : Message_Type);

end Some_Package;
--------------------------------------------------------
with Ada.Text_IO;

package body Some_Package is

   procedure Print (Message : Message_Type) is begin
      Ada.Text_IO.Put_Line("Hello");
   end Print;

end Some_Package;
--------------------------------------------------------