Task

Write a boolean function that tells whether a given integer is prime.



Remember that   1   and all non-positive numbers are not prime.

Use trial division.

Even numbers greater than   2   may be eliminated right away.

A loop from   3   to   √ n    will suffice,   but other loops are allowed.



Related tasks

   count in factors
   prime decomposition
   AKS test for primes
   factors of an integer
   Sieve of Eratosthenes
   factors of a Mersenne number
   trial factoring of a Mersenne number
   partition an integer X into N primes
   sequence of primes by Trial Division


fn is_prime(n: u64) -> bool {
    match n {
        0 | 1 => false,
        2 => true,
        _even if n % 2 == 0 => false,
        _ => {
            let sqrt_limit = (n as f64).sqrt() as u64;
            (3..=sqrt_limit).step_by(2).find(|i| n % i == 0).is_none()
        }
    }
}
 
fn main() {
    for i in (1..30).filter(|i| is_prime(*i)) {
        println!("{} ", i);
    }
}