Problem 60 (alternative attempt with prime pairs)

60_alt.hs

@@ -0,0 +1,20 @@
+import Data.List
+
+upper = 10000
+
+isPrime :: Int -> Bool
+isPrime x = null [k | k <- [2..x-1], k * k <= x, x `mod` k == 0]
+
+primes = [x | x <- [2..upper], isPrime x]
+    
+isPrimeNew :: Int -> Bool
+isPrimeNew x
+    | x <= upper = elem x primes
+    | otherwise = isPrime x
+
+isPrimePair :: Int -> Int -> Bool
+isPrimePair a b = isPrime(read(show a ++ show b)) && isPrime(read(show b ++ show a))
+
+primePairs = [(a, b) | a <- primes, b <- primes, a < b, isPrimePair a b]
+
+main = print primePairs