stack.go
func (s *SegmentStack) Peek() int64 {
	if s.Len() == 0 {
		return rootSegment
	}
	return s.s[s.Len()-1]
}
func (s *SegmentStack) Peek() int64 {
	if s.Len() == 0 {
		return rootSegment
	}
	return s.s[s.Len()-1]
}
func ( s * SegmentStack ) Peek ( ) int64 { if s . Len ( ) == 0 { return rootSegment } return s . s [ s . Len ( ) - 1 ] }
// Peek returns id from the top of the stack. It returns rootSegment if the stack is empty.
Peek returns id from the top of the stack . It returns rootSegment if the stack is empty .