Steven D'Aprano <steve+pyt...@pearwood.info> added the comment:
Hi, The behaviour you are calling "gibbrish" is correct, as the expression `(p-1)/2` calculates a 64-bit floating point number, which may lose precision even for small values of p, but will definitely lose precision for large p. Calling `int()` on that float will not recover the lost precision. So there is no bug here, this is expected behaviour with floats. Please remember that floats are not mathematically exact Real numbers like we learn about in school, they have limited precision. To avoid the float conversion, use the floor-division operator `(p-1)//2` as you mention. If `p` is an int, the result will be exact. ---------- nosy: +steven.daprano title: pow(a,b,p) where b=int((p-1)/2) spits out gibbrish for big p -> pow(a, b, p) where b=int((p-1)/2) spits out gibbrish for big p _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue40446> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
