func (s *VecStack) Pop() (value *Vec) {
	if s.size > 0 {
		value, s.top = s.top.value, s.top.next
		s.size--
		return
	}
	return nil
}
func (s *VecStack) Pop() (value *Vec) {
	if s.size > 0 {
		value, s.top = s.top.value, s.top.next
		s.size--
		return
	}
	return nil
}
func ( s * VecStack ) Pop ( ) ( value * Vec ) { if s . size > 0 { value , s . top = s . top . value , s . top . next s . size -- return } return nil }
// Pop removes the topmost item from the stack and return its value.
//
// If the stack is empty, Pop returns nil.
Pop removes the topmost item from the stack and return its value . If the stack is empty Pop returns nil .