def read_json_numeric_chars
      str = ""
      while (true)
        ch = @reader.peek
        if (!is_json_numeric(ch))
          break;
        end
        ch = @reader.read
        str += ch
      end
      return str
    end
def read_json_numeric_chars
      str = ""
      while (true)
        ch = @reader.peek
        if (!is_json_numeric(ch))
          break;
        end
        ch = @reader.read
        str += ch
      end
      return str
    end
Reads a sequence of characters, stopping at the first one that is not
 a valid JSON numeric character.