code: func (s Int64Slice) Insert(x int64) Int64Slice {
  	i := s.Search(x)
  	if i == len(s) {
  		return append(s, x)
  	}
  
  	if s[i] == x {
  		return s
  	}
  
  	s = append(s, 0)
  	copy(s[i+1:], s[i:])
  	s[i] = x
  	return s
  }
docs: // Insert will insert x into the sorted position in this list
  // and return a list with the value added.  If this slice has not
  // been sorted Insert's behavior is undefined.