old_contents: #!/usr/bin/env python
  # -*- encoding: utf-8 -*-
  #
  # Copyright (c) 2016 ASMlover. All rights reserved.
  #
  # Redistribution and use in source and binary forms, with or without
  # modification, are permitted provided that the following conditions
  # are met:
  #
  #  * Redistributions of source code must retain the above copyright
  #    notice, this list ofconditions and the following disclaimer.
  #
  #  * Redistributions in binary form must reproduce the above copyright
  #    notice, this list of conditions and the following disclaimer in
  #    the documentation and/or other materialsprovided with the
  #    distribution.
  #
  # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  # FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  # COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  # INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  # BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  # LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  # CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  # LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  # ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  # POSSIBILITY OF SUCH DAMAGE.
  
  from collections import namedtuple
  import tyr_ast as ast
  from tyr_error import TyrSyntaxError
  
  MatchPattern = namedtuple('Match', ['pattern', 'body'])
  ConditionElif = namedtuple('ConditionElif', ['cond', 'body'])
  
  class ParserError(TyrSyntaxError):
      def __init__(self, message, token):
          super(ParserError, self).__init__(token.lineno, token.column, message)
  
  def enter_scope(parser, name):
      class State(object):
          def __enter__(self):
              parser.scope.append(name)
  
          def __exit__(self, exc_type, exc_val, exc_tb):
              parser.scope.pop()
  
      return State()
  
  class Subparser(object):
      PRECEDENCE = {
          'call': 10,
          'subscript': 10,
  
          'unary': 9,
  
          '*': 7,
          '/': 7,
          '%': 7,
  
          '+': 6,
          '-': 6,
  
          '>': 5,
          '>= ': 5,
          '<': 5,
          '<=': 5,
  
          '==': 4,
          '!=': 4,
  
          '&&': 3,
  
          '||': 2,
  
          '..': 1,
          '...': 1,
      }
  
new_contents: #!/usr/bin/env python
  # -*- encoding: utf-8 -*-
  #
  # Copyright (c) 2016 ASMlover. All rights reserved.
  #
  # Redistribution and use in source and binary forms, with or without
  # modification, are permitted provided that the following conditions
  # are met:
  #
  #  * Redistributions of source code must retain the above copyright
  #    notice, this list ofconditions and the following disclaimer.
  #
  #  * Redistributions in binary form must reproduce the above copyright
  #    notice, this list of conditions and the following disclaimer in
  #    the documentation and/or other materialsprovided with the
  #    distribution.
  #
  # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  # FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  # COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  # INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  # BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  # LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  # CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  # LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  # ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  # POSSIBILITY OF SUCH DAMAGE.
  
  from collections import namedtuple
  import tyr_ast as ast
  from tyr_error import TyrSyntaxError
  
  MatchPattern = namedtuple('Match', ['pattern', 'body'])
  ConditionElif = namedtuple('ConditionElif', ['cond', 'body'])
  
  class ParserError(TyrSyntaxError):
      def __init__(self, message, token):
          super(ParserError, self).__init__(token.lineno, token.column, message)
  
  def enter_scope(parser, name):
      class State(object):
          def __enter__(self):
              parser.scope.append(name)
  
          def __exit__(self, exc_type, exc_val, exc_tb):
              parser.scope.pop()
  
      return State()
  
  class Subparser(object):
      PRECEDENCE = {
          'call': 10,
          'subscript': 10,
  
          'unary': 9,
  
          '*': 7,
          '/': 7,
          '%': 7,
  
          '+': 6,
          '-': 6,
  
          '>': 5,
          '>= ': 5,
          '<': 5,
          '<=': 5,
  
          '==': 4,
          '!=': 4,
  
          '&&': 3,
  
          '||': 2,
  
          '..': 1,
          '...': 1,
      }
  
      def get_subparser(self, token, subparsers, default=None):
          cls = subparsers.get(token.name, default)
          if cls:
              return cls()
  
  class PrefixSubparser(Subparser):
      def parse(self, parser, tokens):
          raise NotImplementedError()
  
  class InfixSubparser(Subparser):
      def parse(self, parser, tokens, left):
          raise NotImplementedError()
  
      def get_precedence(self, token):
          raise NotImplementedError()
  
subject: add prefix sub-parser and infix sub-parser