/*
                            Converted by Karl-Heinz Mauerlich from SLANT6.PR

Selected from a zip archive containing the P-ROBOTS simulator (Crobots clone in Pascal)

*/


/* plot course function, return degree heading to */
/* reach destination x, y; uses atan() trig function */
int plot_course(xx,yy)
int xx, yy;
{
  int d;
  int x,y;
  int scale;
  int curx, cury;

  scale = 100000;  /* scale for trig functions */
  curx = loc_x();  /* get current location */
  cury = loc_y();
  x = curx - xx;
  y = cury - yy;

  /* atan only returns -90 to +90, so figure out how to use */
  /* the atan() value */

  if (x == 0) {      /* x is zero, we either move due north or south */
    if (yy > cury)
      d = 90;        /* north */
    else
      d = 270;       /* south */
  } else {
    if (yy < cury) {
      if (xx > curx)
        d = 360 + atan((scale * y) / x);  /* south-east, quadrant 4 */
      else
        d = 180 + atan((scale * y) / x);  /* south-west, quadrant 3 */ 
    } else {
      if (xx > curx)
        d = atan((scale * y) / x);        /* north-east, quadrant 1 */
      else
        d = 180 + atan((scale * y) / x);  /* north-west, quadrant 2 */
    }
  }
  return (d);
}

/* classical pythagorean distance formula */
int distance(x1,y1,x2,y2)
int x1;
int y1;
int x2;
int y2;
{
  int x, y;
  int d;

  x = x1 - x2;
  y = y1 - y2;
  d = sqrt((x*x) + (y*y));
  return(d);
}

GOTO(dest_x, dest_y) {
  while (distance(loc_x(), loc_y(), dest_x, dest_y) > 100) {
    if (speed() == 0) drive(plot_course(dest_x, dest_y), 100);
  }

  drive(0, 0); /*i.e., stop*/
  while (speed() > 0) ; /*nothing-- i.e., slow down*/
}

main() { /* Main routine */

  GOTO(5, 995); /* Go to upper left corner */

  while(1) { /* Main loop */

    while (loc_y() > 150) { /* Check for bottom */
      drive(315, 100); /* Go diagonally down and right */
      if (scan(0, 10) > 0) { /* Look right */
        cannon(0, scan(0, 10)); /* Shoot if you see anything */
      }
      if (scan(90, 10) > 0) { /* Look up */
        cannon(90, scan(90, 10)); /* Shoot if you see anything */
      }
      if (scan(270, 10) > 0) { /* Look down */
        cannon(270, scan(270, 10)); /* Shoot if you see anything */
      }
      if (scan(180, 10) > 0) { /* Look left */
        cannon(180, scan(180, 10)); /* Shoot if you see anything */
      }
    }

    drive(315, 0); /* Near bottom, slow down */
    while (speed() > 50) ; /* Wait for slow to 50 */

    while (loc_y() < 850) { /* Check for top */
      drive(135, 100); /* Go diagonally up and left */
      if (scan(0, 10) > 0) { /* Look right */
        cannon(0, scan(0, 10)); /* Shoot, as before */
      }
      if (scan(270, 10) > 0) { /* Look down */
        cannon(270, scan(270, 10)); /* Shoot, as before */
      }
      if (scan(90, 10) > 0) { /* Look up */
        cannon(90, scan(90, 10)); /* Shoot if you see anything */
      }
      if (scan(180, 10) > 0) { /* Look left */
        cannon(180, scan(180, 10)); /* Shoot if you see anything */
      }
    }

    drive(135, 0); /* Slow down */
    while (speed() > 50) ; /* Wait for 50 */

  }
}