import functools
 
 def bounce(func):
   @functools.wraps(func)
   def _inner(arg):
     result = func(arg)
     return result(fact)
   return _inner
 
 class return_if(object):
   def __init__(self, map):
     self._map = dict(
       (tuple(k) if hasattr(k, '__iter__') else (k,), v) for k,v in map.iteritems()
     )
     self._func = lambda x:x
   def _inner(self, *args):
     if args in self._map: return self._map[args]
     else: return self._func(*args)
   def __call__(self, func):
     self._func = func
     return self._inner
 
 @bounce
 @return_if({1: lambda _:1})
 def fact(n):
   return lambda x: n*x(n-1)
 
 
 def fact(m):
   @return_if({1: lambda :1})
   def fact_inner(n):
     return lambda f: n*f(n-1)
   return fact_inner(m)(lambda n: fact_inner(n))
 
 assert fact(5) == 120
 print 'yes!'