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


/* Return 1 if n is prime, 0 otherwise */
define p(n) {
    auto i
 
    if (n < 2) return(0)
    if (n == 2) return(1)
    if (n % 2 == 0) return(0)
    for (i = 3; i * i <= n; i += 2) {
        if (n % i == 0) return(0)
    }
    return(1)
}