def match_str(str)
      ret = nil
      if @input[@current_pos, str.size] == str
        ret = str
        @current_pos += str.size
      else
        ret = :failed
        fail(type: "literal", value: str, description: "\"#{str}\"") if @slient_fails == 0
      end
      ret
    end
def match_str(str)
      ret = nil
      if @input[@current_pos, str.size] == str
        ret = str
        @current_pos += str.size
      else
        ret = :failed
        fail(type: "literal", value: str, description: "\"#{str}\"") if @slient_fails == 0
      end
      ret
    end
match string