Re: Task discriminants

["Nick Roberts" <nick.roberts@acm.org>]

"Dave Levy" <dlevy@mail.usyd.edu.au> wrote in message
news:40ACC50E.9040406@mail.usyd.edu.au...

> Suppose one has a task type with a discriminant:
>
>     task type A_Task( Id : integer);
>
> and one wishes to declare a set of tasks with initialised discriminants:
>     t1 : A_Task(1);
>     t2 : A_Task(2);
>     t3 : A_Task(3);
>
> How could one declare them as an array of tasks with each one getting an
> initialised discriminant? Perhaps something like:
>
>     The_Tasks: array (1..3) of A_Task( Id => 1,2,3 );
>
> Except I tried this with Gnat and it won't compile.

It is a basic precept of Ada arrays that its components are all of the same
subtype. This means that they cannot have different discriminants. So this
approach, as such, is doomed.

You could use the 'old' technique:

   type A_Task_Number is range 1..3;

   task type A_Task is
      entry Init (Num: in A_Task_Number);
      ...
   end;

   The_Tasks: array (A_Task_Number) of A_Task;

   ...
      for i in A_Task_Number loop
         The_Tasks(i).Init(i);
      end loop;
   ...

   task body A_Task is
      My_Num: A_Task_Number;
      ...
   begin
      accept Init (Num: in A_Task_Number) do
         My_Num := Num;
      end;
      ...
   end A_Task;

It's always worked for me!

-- 
Nick Roberts