code: func is_alpha(b []byte, i int) bool {
  	return b[i] >= '0' && b[i] <= '9' || b[i] >= 'A' && b[i] <= 'Z' || b[i] >= 'a' && b[i] <= 'z' || b[i] == '_' || b[i] == '-'
  }
docs: // Check if the character at the specified position is an alphabetical
  // character, a digit, '_', or '-'.