Python Trampolining

trampoline.py

def trampoline(f):
    def _wrapped(*args, **kwargs):
        x = f(*args, **kwargs)
        while callable(x):
            x = x()
        return x
    return _wrapped


def factorial(n, total=1):
    return total if n == 0 else factorial(n - 1, total * n)


def thunk_factorial(n, total=1):
    def ret_func(*args, **kwargs):
        return total if n == 0 else thunk_factorial(n - 1, total * n)
    return ret_func


print "trampolined 1000!: {}".format(trampoline(thunk_factorial)(1000))
try:
    print "regular 1000!: {}".format(factorial(1000))
except RuntimeError, e:
    print "regular 1000! ran into exception: {}".format(e)