你有两个问题:
>您的递归次数错误(如果n == 1,则应调用该函数一次);和
>您没有在递归调用的返回值上调用f,因此该函数只应用一次.
尝试:
def repeat(f, n, x):
if n == 1: # note 1, not 0
return f(x)
else:
return f(repeat(f, n-1, x)) # call f with returned value
或者,或者:
def repeat(f, n, x):
if n == 0:
return x # note x, not f(x)
else:
return f(repeat(f, n-1, x)) # call f with returned value
(感谢后者的@Kevin,它支持n == 0).
例:
>>> repeat(lambda z: z + 1, 2, 2)
4
>>> assert repeat(lambda z: z * 2, 4, 3) == 3 * 2 * 2 * 2 * 2
>>>