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


func IsPrime(n int) bool {
	if n < 0 { n = -n }
	switch {
        case n == 2:
		return true
	case n < 2 || n % 2 == 0:
		return false
 
	default:
		for i = 3; i*i <= n; i += 2 {
			if n % i == 0 { return false }
		}
	}
	return true
}