Re: Tasking issues

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Sun, 12 Aug 2007 21:39:58 GMT, anon wrote:

> First the 'ABORT' statement is a legal statement. Yes, there are better 
> ways to terminate the task, but that would mean a complete overhaul of 
> shaunpatterson's program, which could confuse shaunpatterson.

No, it is using abort, which is confusing in a small illustrative program.
There is no need to abort tasks in almost any Ada program.

> Also any statement that is valid in the language is valid in the code. And 
> the people who say 'ABORT' statement is bad are just like the guys who 
> said that "GOTO" in other languages

Ada has goto, see ARM 5.8.

> or Ada's 'LOOP' statement is bad. 
> Since "GOTO' or 'LOOP' statements are a high-level language version of 
> the 'JMP' assembly instruction.

Yes, yes. NASA is training astronauts climbing trees, that makes them
closer to the moon. Everything is Turing Complete. Equivalence of programs
proves nothing.

> As for "Get_Line immediately", thats an error, The Ada code can not 
> force the operating system or keyboard routine to abort.

Of course it can, on most operating systems you can wait for a
or-combination of events, you can also close the file handle from outside
and that will abort pending I/O etc. It is technically possible, though,
AFAIK, RM does not require Get_Line being abortable. Yet it is to expect in
a decent implementation.

[...]
> Also where is your example of how the code should be written without a 
> complete overhaul of shaunpatterson's program. Only simple additions or ]
> changes with some comment for him.

You mean your code or one of the OP? Your code can be rewritten without
aborts and global variables:

with Ada.Characters.Latin_1;  use Ada.Characters.Latin_1;
with Ada.Text_IO;             use Ada.Text_IO;

procedure Main is

   task Get_Name is
      entry Shut_Down;
   end Get_Name;

   task Print_Something is
      entry Shut_Down;
   end Print_Something;

   task body Get_Name is
      Name   : String (1..25);
      Index  : Positive;
      Got_It : Boolean;
   begin
      Get_Line : loop
         Index := Name'First;
         loop
            select
               accept Shut_Down;
               exit Get_Line;
            else
               Get_Immediate (Name (Index), Got_It);         
            end select;
            if Got_It then
               exit when Name (Index) = CR;
               if Index < Name'Last then
                  Index := Index + 1;
               end if;
            end if;
         end loop;
         if Index = Name'Last then
            Put_Line ("Input (truncated):" & Name (1..Index - 1));
         else
            Put_Line ("Input:" & Name (1..Index - 1));
         end if;
      end loop Get_Line;
   end Get_Name;

   task body Print_Something is
   begin
      loop
         select
            accept Shut_Down;
            exit;
         else
            Put_Line ("blah...");
         end select;
      end loop ;
   end Print_Something;

begin
   delay 1.0;
   Get_Name.Shut_Down;
   Print_Something.Shut_Down;
end Main;

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de