atropinetears / num-primes Goto Github PK

When I wrote a little program to check out how this crate works and I found something strange. Now I am not an expert in prime numbers so I might have done something wrong.

use num_primes::*;

fn main() {
    let numbers = [
        Generator::new_prime(512),
        Generator::new_prime(32),
        Generator::new_prime(16),
        17957u32.into(),
        5u32.into(),
    ];

    for number in numbers {
        if Verification::is_prime(&number) {
            println!("{} is a prime number", number);
        } else {
            println!("{} is not a prime number", number);
        }
    }
}

And the result I got was:

7143985141390067685062171960235716944255257884955901307961617824283167357210788588888340513160296160835326595412561271828611378926148900988701377840767267 is a prime number
2161366811 is a prime number
49331 is a prime number
17957 is not a prime number
5 is not a prime number

I expected both 17957 and 5 to be prime numbers. So I tried to generate a 8 bit prime number but then the program hang. I then tried to find the limit of the minimum number of bits for which a prime number could be generated and found that Generator::new_prime(15) worked fine but Generator::new_prime(14) made the program hang (probably stuck in an infinite loop some where).

Hey!
so the prime generator returns BigUint from a private module.
This breaks incompatibility with existing code that uses BigUint.

example of an error:
for
let d = e.invmod(&et);
we get:
expected struct num_bigint::BigUint, found struct num_bigint::biguint::BigUint

Why not return !is_prime here, when would third branch happens?