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!'