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


import "/fmt" for Fmt
 
var isPrime = Fn.new { |n|
    if (n < 2) return false
    if (n%2 == 0) return n == 2
    var p = 3
    while (p * p <= n) {
        if (n%p == 0) return false
        p = p + 2
    }
    return true
}
 
var tests = [2, 5, 12, 19, 57, 61, 97]
System.print("Are the following prime?")
for (test in tests) {
    System.print("%(Fmt.d(2, test)) -> %(isPrime.call(test) ? "yes" : "no")")
}