class JunkComparisonException (BaseException):

	pass

class Junk:

	def __init__ (self, represents = None):
		assert(represents == None or isinstance(represents, basestring))
		self.repr = represents

	def __str__ (self):
		if self.repr:
			return '['+self.repr+']'
		return "[junk]"

	def __repr__ (self):
		return self.__str__()

	def __add__ (self, other):
		return self

	def __radd__ (self, other):
		return self

	def __sub__ (self, other):
		return self

	def __rsub__ (self, other):
		return self