module ProjectEuler ( isPrime ) where isPrime :: (Integral n) => n -> Bool isPrime 1 = False isPrime 2 = True isPrime 3 = True isPrime n = n `mod` 2 /= 0 && n `mod` 3 /= 0 && null [ x | x <- candidates, n `mod` x == 0 || n `mod` (x+2) == 0 ] where candidates = [5,11..limit] limit = floor(sqrt(fromIntegral n)) + 1