old_contents: from .lexerconstants import *
  from .ws_token import Tokeniser
  
  
  class Lexer(object):
      def __init__(self, line):
          self.line = line
          self.pos = 0
          self.tokens = []
  
      def _get_int(self):
          token = Tokeniser()
          if self.line[-1] == '\n':
              const = 'INT'
              token.scan(self.line, self.pos, const)
          else:
              # TODO: Add error handling for invalid integer
              pass
          return token
  
      def _get_token(self, const):
          token = Tokeniser()
          token.scan(self.line, self.pos, const)
          return token
  
      def get_all_tokens(self):
          while self.pos < len(self.line):
              const = IMP_CONST if self.pos is 0 else eval(
                  "{}_CONST".format(self.tokens[0].type))
              token = self._get_token(const)
              self.tokens.append(token)
              self.pos = self.pos + len(token.value)
              if token.type == 'PUSH':
                  self.tokens.append(self._get_int())
                  self.pos = len(self.line)
  
  
new_contents: from .lexerconstants import *
  from .ws_token import Tokeniser
  
  
  class IntError(ValueError):
      '''Exception when invalid integer is found'''
  
  
  class Lexer(object):
      def __init__(self, line):
          self.line = line
          self.pos = 0
          self.tokens = []
  
      def _get_int(self):
          token = Tokeniser()
          if self.line[-1] == '\n':
              const = 'INT'
              token.scan(self.line, self.pos, const)
          else:
              raise IntError
          return token
  
      def _get_token(self, const):
          token = Tokeniser()
          token.scan(self.line, self.pos, const)
          return token
  
      def get_all_tokens(self):
          while self.pos < len(self.line):
              const = IMP_CONST if self.pos is 0 else eval(
                  "{}_CONST".format(self.tokens[0].type))
              token = self._get_token(const)
              self.tokens.append(token)
              self.pos = self.pos + len(token.value)
              if token.type == 'PUSH':
                  self.tokens.append(self._get_int())
                  self.pos = len(self.line)
  
  
subject: Add Execption for invalid Integer