func (s *VecStack) Peek() (value *Vec, exists bool) {
	exists = false
	if s.size > 0 {
		value = s.top.value
		exists = true
	}
	return
}
func (s *VecStack) Peek() (value *Vec, exists bool) {
	exists = false
	if s.size > 0 {
		value = s.top.value
		exists = true
	}
	return
}
func ( s * VecStack ) Peek ( ) ( value * Vec , exists bool ) { exists = false if s . size > 0 { value = s . top . value exists = true } return }
// Peek returns the topmost item without removing it from the stack.
Peek returns the topmost item without removing it from the stack .