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


define is_prime(n)
{
   if (n == 2) return(1);
   if (n <= 1) return(0);
   if ((n & 1) == 0) return(0);
 
   variable mx = int(sqrt(n)), i;
 
   _for i (3, mx, 1) {
     if ((n mod i) == 0)
       return(0);
   }
   return(1);
}
 
define ptest() 
{
   variable lst = {};
 
   _for $1 (1, 64, 1)
     if (is_prime($1))
       list_append(lst, string($1));
   print(strjoin(list_to_array(lst), ", "));
}
ptest();