nth-prime.rs

pub fn nth(n: usize) -> Result<u64, &'static str> {
  if n <= 0 { Err("No primes below 1") }
  else {
    match (2..).filter(|&x| is_prime(x)).nth(n - 1) {
      Some(n) => Ok(n),
      None => Err("Iteration error")
    }
  }
}

fn is_prime(n: u64) -> bool {
  let mut lhs = n / 2;
  let mut rhs = 1;
  let mut factors = 0;

  while lhs > 0 {
    let result = lhs * rhs;

    if result == n { 
      factors += 1;
      lhs -= 1; 
      rhs = 1;
    } else if result > n { 
      lhs -= 1; 
      rhs = 1; 
    } else if result < n { 
      rhs += 1; 
    }
  }

  factors == 1
}