Drawing Hilbert Curve

enum {
  UP,
  LEFT,
  DOWN,
  RIGHT,
};

void hilbert(int level,int direction=UP)
{
  if (level==1) {
    switch (direction) {
    case LEFT:
      move(RIGHT);      /* move() could draw a line in... */
      move(DOWN);       /* ...the indicated direction */
      move(LEFT);
      break;
    case RIGHT:
      move(LEFT);
      move(UP);
      move(RIGHT);
      break;
    case UP:
      move(DOWN);
      move(RIGHT);
      move(UP);
      break;
    case DOWN:
      move(UP);
      move(LEFT);
      move(DOWN);
      break;
    } /* switch */
  } else {
    switch (direction) {
    case LEFT:
      hilbert_level(level-1,UP);
      move(RIGHT);
      hilbert_level(level-1,LEFT);
      move(DOWN);
      hilbert_level(level-1,LEFT);
      move(LEFT);
      hilbert_level(level-1,DOWN);
      break;
    case RIGHT:
      hilbert_level(level-1,DOWN);
      move(LEFT);
      hilbert_level(level-1,RIGHT);
      move(UP);
      hilbert_level(level-1,RIGHT);
      move(RIGHT);
      hilbert_level(level-1,UP);
      break;
    case UP:
      hilbert_level(level-1,LEFT);
      move(DOWN);
      hilbert_level(level-1,UP);
      move(RIGHT);
      hilbert_level(level-1,UP);
      move(UP);
      hilbert_level(level-1,RIGHT);
      break;
    case DOWN:
      hilbert_level(level-1,RIGHT);
      move(UP);
      hilbert_level(level-1,DOWN);
      move(LEFT);
      hilbert_level(level-1,DOWN);
      move(DOWN);
      hilbert_level(level-1,LEFT);
      break;
    } /* switch */
  } /* if */
}