Problem Statement

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.

Let's start with the solution:

ISPRIME(N)
 QUIT:(N=2) 1
 NEW I,R
 SET R=N#2
 IF R FOR I=3:2:(N**.5) SET R=N#I Q:'R
 KILL I
 QUIT R