From 9db0008777cc4cd9f07e14a3458e3d903e3cc4f6 Mon Sep 17 00:00:00 2001
From: Determinant <ted.sybil@gmail.com>
Date: Mon, 29 May 2017 13:29:11 -0400
Subject: finish vol 4

---
 31-41/40.hs | 10 ++++++++++
 1 file changed, 10 insertions(+)
 create mode 100644 31-41/40.hs

(limited to '31-41/40.hs')

diff --git a/31-41/40.hs b/31-41/40.hs
new file mode 100644
index 0000000..9d9b2f7
--- /dev/null
+++ b/31-41/40.hs
@@ -0,0 +1,10 @@
+isPrime :: Int -> Bool
+
+isPrime 1 = False
+isPrime x = and $ map (\y -> x `mod` y /= 0) $ fst $ span (\y -> y * y <= x) [2..]
+
+goldbach :: Int -> (Int, Int)
+
+goldbach x = head [(a, b) | a <- primes, let b = x - a, isPrime b]
+    where primes = filterPrime[3..]
+          filterPrime (p:xs) = p:filterPrime [x | x <- xs, x `mod` p /= 0]
-- 
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