On 11/7/23 18:26, Julieta Shem via Python-list wrote: > For the first time I'm trying to write a tail-recursive > square-and-multiply and, even though it /seems/ to work, I'm not happy > with what I wrote and I don't seem to understand it so well. > > --8<---------------cut here---------------start------------->8--- > def sam(b, e, m, acc = 1): > if e == 0: > return acc > if is_even(e): > return sam(remainder(b * b, m), e//2, m, acc) > else: > return sam(b, e - 1, m, remainder(b * acc, m)) > --8<---------------cut here---------------end--------------->8---
I don't see any definition of "remainder()" When you post to the list, please provide short but complete code, including a demonstration of using the code provided. That will help others understand what you are trying to do, and perhaps comment on your concerns. > You see, I tried to use an accumulator, but I'm only accumulating when > the exponent is odd. When it's even, I feel I'm forced to change the > base into b * b mod m and leave the accumulator alone. This feels so > unnatural to me. I feel I broke some symmetry there. I'm having to > think of two cases --- when I change the accumulator and when I change > the base. That seems too much for my small head. Can you help? I don't really understand the code either, so I cannot help much. -- https://mail.python.org/mailman/listinfo/python-list
