Question

This is an school assignment. To create a snake game.
So I have created two packages one for graphics and one for the snake.
The snake moves smoothly and everything works. But I need to control the snake with the keyboard.This is the main procedure:

with Graphics; use Graphics;
with Graphics.Snake; use Graphics.Snake;

procedure Run_Snake is
   B : Buffer (1 .. 24, 1 .. 80);
   S : Snake_Type (1 .. 5) := ((10, 10),
                               (10, 11),
                               (10, 12),
                               (11, 12),
                               (12, 12));
   D : Duration := 0.07;
begin

  loop
      Empty (B);
      Draw_Rect (B, (1, 1), Width  => 80,
                 Height            => 24);
      Draw (B, S);
      Update (B);



      Move (S, 0, -1);
      delay D;

   end loop;

end Run_Snake;

in this line of code I controll the snakes head rotation:

Move (S, x, y);  

where x is the x value it can be -1 for left, 1 for right.
where y is the y value it can be -1 for down, 1 for up;

Anyways, how can I read the input without pausing the snake from moving?
Thanks

Answer 1

You might want to use a multitasking system to overcome your problem.

procedure Snake_Game is

   task Run_Snake is
      entry Input_Received (S : Snake_Type; x : Integer; y : Integer);
   end Run_Snake;

   task body Run_Snake is
      D : constant Duration := 0.07;
      B : Buffer (1 .. 24, 1 .. 80);
   begin
      loop
         select
            accept Input_Received (S : Snake_Type; x : Integer; y : Integer) do
               Move (S, x, y);
            end;
         or
            delay D;
            Empty (B);
            Draw_Rect (B, (1, 1), Width => 80, Height => 24);
            Draw (B, S);
            Update (B);
         end select;
      end loop;
   end Run_Snake;

   S : Snake_Type (1 .. 5) := ((10, 10),
                              (10, 11),
                              (10, 12),
                              (11, 12),
                              (12, 12));

begin
   loop
      Do_Whatever_You_Want_To_Get (x, y)
      Run_Snake.Input_Received(S, x, y);
   end loop;
end Snake_Game;

In such a system, you have your drawing process in a separate task. At the “select” line, the task waits for a call to Input_Received(). If this entry is not called after a duration D, then the task executes all the drawing functions, and the loop begins anew.

Hope it can help.
Cheers.