Re: [Q] Task Types

[Matthew Heaney <matthew_heaney@acm.org>]

John McCabe <jgm@hayling.cwmbran.gecm.com> writes:

> Is there a means of providing an incomplete declaration of a Task type?

The following code compiles cleanly using gnat v3.09.


procedure Test_Task is

   type T;
   type TA is access T;

   task type T is
      entry E (O : TA);
   end T;

   task body T is
   begin
      accept E (O : TA);
   end T;

begin

   null;

end Test_Task;


You'd often use access discriminants for this sort of thing:

type RT;

task type TT (RO : access RT) is
   entry E;
end TT;

type RT is
   limited record
      TO : TT (RT'Access);
      I  : Integer;
   end record;

task body TT is
begin
   accept E do <whatever> end E;

   ... RO.I ...

end TT;

Access discriminants give task type TT access to all the components in
the record.