Interesting loop in Pascal

[User137]

You have several errors in it. I don't know about speed, propably not faster. It can have some modifications which still won't help much. Mod itself on every index makes it heavier than simple for-loop:

  y:=-1; // important to initialize y, and know that y gets +1 on first round
  for i:=0 to Map_width * map_height -1 do // added -1, because it starts from 0
  begin
    x:=i mod Map_width;
    if x=0 then y:=y+1; // mod Width, not height, and then we can re-use x
    
    // do_something_with_xy

    //i:=i+1; // Don't modify for-loop variable
  end;

This version however might be faster than the for-loop, or at least equal:

  x:=0; y:=0;
  for i:=0 to Map_width * map_height -1 do begin
        
    // do_something_with_xy

    x:=x+1;
    if x=Map_width then begin
      x:=0;
      y:=y+1;
    end;
  end;