Ada Example : parsing of html

Ada Example : multi tasking

This example shows how Ada language fully integrates multitask programming. Most of the complexity in multitasking systems is the way of sharing ressource.

Here, Ada is inventive and defers slightly : The returned value of a Task is truly safe.

Computes zetha(2) S = Sum 1/k^2 with k in [1 .. n] = 1.6449 = pi^2 /6

Main program : main.adb

with Ada.Text_IO; use Ada.Text_IO;
with Ada.Task_Identification;
 
procedure Main is
 
   Ct_Nb_TOp  : constant := 100000000;
   Ct_Nb_Tack : constant := 10;
   Ct_Nb_Op   : constant := Ct_Nb_TOp/Ct_Nb_Tack;
   pragma PRIORITY (1);
 
   task type Task_A is
      entry Init_A( Val : in      integer );
      entry End_A ( S   : in out  Long_Float );
   end Task_A;
 
 
 
   task body Task_A is
      VA : integer := 0;
      Sum : Long_Float  := 0.0 ;	
   begin
 
      accept Init_A( Val : in integer ) do
         VA:=Val;
         Put_line("Init_A " & VA'Img);
      end Init_A;
 
         Put_line("Do_A" & VA'Img);
         for I in VA .. VA+ (Ct_Nb_Op-1) loop
            Sum := Sum + 1.0/(Long_Float(I)*Long_Float(I));
         end loop;
 
      accept End_A (S : in out  Long_Float ) do
         S:=Sum+S;
         Put_line("End_A" & VA'Img);
      end End_A;
 
   end Task_A;
 
 
   A_Array : array (0.. Ct_Nb_Tack) of Task_A;
   Global_Sum : Long_Float := 0.0 ;
 
   begin
   Put_line("Main");
   for I in 0 .. Ct_Nb_Tack loop
       Put_line("  " & Ada.Task_Identification.Image(A_Array(I)'Identity));
      A_Array(I).Init_A(I*Ct_Nb_Op+1);
   end loop;
 
   for I in reverse  0 .. Ct_Nb_Tack loop
      A_Array(I).End_A(Global_Sum);
      Put_line("End_A from main" & Global_Sum'Img);
   end loop;
 
end Main;