code: func (s Int64Slice) Exists(x int64) bool {
  	i := s.Search(x)
  	if i == len(s) {
  		return false
  	}
  
  	return s[i] == x
  }
docs: // Exists returns a bool indicating if the provided value exists
  // in this list.  This has undefined behavior if the list is not
  // sorted.