Ciao, Il Gio, 22 Agosto 2019 10:32 am, Niels Möller ha scritto: > "Marco Bodrato" <bodr...@mail.dm.unipi.it> writes: >> I'd suggest to extend the range for mpz_nextprime. >> Can we consider both positive and negative primes?
> I think that's a bit unusual. We can compare with the corresponding > functions in pari/gp. These differ from gmp by nextprime(p) == p > if p is prime. And they don't consider negative numbers to be primes. You are right, and the last one is a relevant difference. Within pari/gp we have: ? isprime(17) %1 = 1 ? isprime(-17) %2 = 0 For our library, if we have mpz_neg (x, y); then the following condition is always true (for any y and n): mpz_probab_prime_p (x, n) == mpz_probab_prime_p (y, n) If p is a positive prime, -p is a prime element in the ring of integers. Right? So, if we consider -7 as a prime number, then why should we say that 2 is the correct answer to _nextprime if e.g. -10 is given as a starting point? Ĝis, m _______________________________________________ gmp-devel mailing list gmp-devel@gmplib.org https://gmplib.org/mailman/listinfo/gmp-devel