func (s *VecStack) PopLast() (value *Vec) {
	if lastElem := s.popLast(s.top); s.size >= 2 && lastElem != nil {
		return lastElem.value
	}
	return nil
}
func (s *VecStack) PopLast() (value *Vec) {
	if lastElem := s.popLast(s.top); s.size >= 2 && lastElem != nil {
		return lastElem.value
	}
	return nil
}
func ( s * VecStack ) PopLast ( ) ( value * Vec ) { if lastElem := s . popLast ( s . top ) ; s . size >= 2 && lastElem != nil { return lastElem . value } return nil }
// PopLast removes the bottommost item.
//
// PopLast does nothing if the stack does not contain at least 2 items.
PopLast removes the bottommost item . PopLast does nothing if the stack does not contain at least 2 items .