rotateStackDown method Null safety

void rotateStackDown()

the R key

Implementation

void rotateStackDown() {
  Value t = _stack[0];
  _stack[0] = _stack[1];
  _stack[1] = _stack[2];
  _stack[2] = _stack[3];
  _stack[3] = t;
  display.window = 0;
  _needsSave = true;
}