From 871f1a383f3434ee8f01d77712730c661596bf7d Mon Sep 17 00:00:00 2001
From: Sasha <sasha+frama@marvid.fr>
Date: Fri, 2 Feb 2018 17:25:10 +0100
Subject: [PATCH] Shuffle is more a CCard thing than something specific to
 KoiKoi or other Games

---
 CCard.hs | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/CCard.hs b/CCard.hs
index 7b8e2be..c56ffc7 100644
--- a/CCard.hs
+++ b/CCard.hs
@@ -2,6 +2,7 @@ module CCard where
 
 import Data.Word (Word64)
 import Data.Bits (setBit, (.|.), (.&.), shift, xor, testBit)
+import System.Random (randomRIO)
 
 data Flower =
     Pine
@@ -72,3 +73,14 @@ pair card1 card2 = flower card1 == flower card2
 
 cards :: [Card]
 cards = [Pine0 .. Phoenix]
+
+shuffle :: [a] -> IO [a]
+shuffle l =
+  aux (length l) l
+  where
+    aux n [] = return []
+    aux n (h:t) = do
+      cut <- randomRIO (0, n-1)
+      shuffled <- shuffle t
+      let (top, bottom) = splitAt cut shuffled
+      return $ top ++ h : bottom