# return true if x is prime.  return false otherwise.
let primetest x =
    let rec primetest_driver num max x =
        if (greater num max) true
	    (if (equal (mod x num) 0) 
                false
		(primetest_driver (plus num 1) max x))
    in 
    let max = divide x 2 in  
    primetest_driver 2 max x
in primetest 101