sapply
不是连续传递风格,所以你必须替换它。
这是 Python 中延续传递风格的翻译(另一种语言)not有适当的尾部调用):
def sum_ways_cps(n_times, k_sum, s_side, ctn):
"""Compute the number of ways to get the sum k by rolling an s-sided die
n times. Then pass the answer to ctn."""
if k_sum < n_times or k_sum > n_times * s_side:
return ctn(0)
elif n_times == 1:
return ctn(1)
else:
f = lambda j, ctn: sum_ways_cps(n_times - 1, k_sum - j, s_side, ctn)
return sum_cps(1, s_side + 1, 0, f, ctn)
def sum_cps(j, j_max, total_so_far, f, ctn):
"""Compute the sum of f(x) for x=j to j_max.
Then pass the answer to ctn."""
if j > j_max:
return ctn(total_so_far)
else:
return f(j, lambda result: sum_cps(j + 1, j_max, total_so_far + result, f, ctn))
sum_ways_cps(2, 7, 6, print) # 6