From 6996016ccc33e1ffe7f8c289b4d869d412003075 Mon Sep 17 00:00:00 2001
From: Jesse McDonald <nybble41@gmail.com>
Date: Wed, 2 Sep 2015 20:06:18 -0500
Subject: [PATCH] Add solution for problem 60.

---
 Problem060.hs | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)
 create mode 100644 Problem060.hs

diff --git a/Problem060.hs b/Problem060.hs
new file mode 100644
index 0000000..2c0b48b
--- /dev/null
+++ b/Problem060.hs
@@ -0,0 +1,24 @@
+-- Find the lowest sum for a set of five primes for which any two primes
+-- concatenate to produce another prime.
+
+import Euler
+import Debug.Trace
+import Data.Array.Unboxed ((!))
+
+nDigits n = ceiling $ logBase 10 $ max 1 $ fromIntegral n
+a ## b = (a * (10 ^ nDigits b)) + b
+
+main = print $ head $ do
+   a <- drop 4 primes
+   b <- takeWhile (< a) primes
+   guard $ all isPrime $ [(## b), (b ##)] <*> [a]
+   --traceM $ show (a,b)
+   c <- takeWhile (< b) primes
+   guard $ all isPrime $ [(## c), (c ##)] <*> [a,b]
+   --traceM $ show (a,b,c)
+   d <- takeWhile (< c) primes
+   guard $ all isPrime $ [(## d), (d ##)] <*> [a,b,c]
+   e <- takeWhile (< d) primes
+   guard $ all isPrime $ [(## e), (e ##)] <*> [a,b,c,d]
+   let xs = [a,b,c,d,e]
+   return (sum xs, xs)