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Newsgroups: comp.lang.ada
From: anon@anon.org (anon)
Subject: Re: Task question
Reply-To: anon@anon.org (anon)
References: <31235206-1025-467c-8444-07a8eacc9b48@e6g2000prf.googlegroups.com>
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Date: Tue, 11 Dec 2007 00:43:41 GMT
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Date: 2007-12-11T00:43:41+00:00
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--
-- f_p.adb
--
with Ada.Text_IO ;

procedure F_P is

  task type Function_Task is
    entry Function_1 ( X : in Boolean ) ;
    entry Result_1 ( X : out Boolean ) ;
  end function_Task ;

  --
  -- This task uses two calls. One activate the function
  -- and the second returns the function value once valid.
  --
  -- Note: Delays are use to simulate the actual algorithm for 
  -- the function. Normally there are not needed.
  --
  task body Function_Task is

      W : Boolean ; -- Hold paramter and result value

    begin -- Function_Task
      -- Initial or setup functions
      loop
        select
          --
          -- Start execution of function
          --
          accept Function_1 ( X : in Boolean ) do
            W := X ;
          end Function_1 ;
          --
          -- Routine for function. It could be a function call
          -- Or code here
          --
          Delay 1.0 ; -- simulate a complex algorithm
          W := not W ;
        or
          --
          -- Retrieve function's result if needed wait until 
          -- result is valid
          --
          accept Result_1 ( X : out Boolean ) do
            X := W ; -- Retrive result.
          end Result_1 ;
        or
          --
          -- Allows the task to end, if the program exist
          --
          terminate ; 
        end select ;
      end loop ;
      -- shutdown function
  end function_Task ;

  procedure put ( V : boolean ) is
    begin
      if V then
        Ada.Text_IO.put ( Item => "True" ) ;
      else
        Ada.Text_IO.put ( Item => "False" ) ;
      end if ;              
    end ;

  Functions : function_Task ;
  Z : Boolean := True ;

begin -- F_P 

  Ada.Text_IO.put_line ( Item => "Excute Function 1" ) ;
  Functions.Function_1 ( Z ) ;  
  Put ( Z ) ;
  Ada.Text_IO.new_line ;

  Ada.Text_IO.put_line ( Item => "Excute Something Else" ) ;

  --
  -- Now we need the result from Function 1. So we may 
  -- need to wait until result of function is valid.
  --
  Ada.Text_IO.put_line ( Item => "Get Result for function 1" ) ;
  Functions.Result_1 ( Z ) ;  
  Put ( Z ) ;
  Ada.Text_IO.new_line ;

  Ada.Text_IO.put_line ( Item => "Exit Program" ) ;
  
end F_P ;

In <31235206-1025-467c-8444-07a8eacc9b48@e6g2000prf.googlegroups.com>, shaunpatterson@gmail.com writes:
>Hey,
>
>   What is the best / proper way to spawn a new task so that a
>function call can
>continue in the background.. like so:
>
>procedure Test is
>  begin
>
>          -- Call a callback function that may take a long time
>          FuncPtr.all
>
>
>          -- Continue other processing here
>
>  end Test;
>
>
>Is there any way to encapsulate the callback function call in another
>task WITHOUT making
>the function -- the function called by funcptr.all -- a new task?
>
>Thanks
>
>--
>Shaun