From b499ed76f85c0384ecae9922128188717f0d3631 Mon Sep 17 00:00:00 2001
From: Joe Zhao <ztuowen@gmail.com>
Date: Sun, 22 Feb 2015 21:29:20 +0800
Subject: +p9

---
 p9.hs | 13 +++++++++++++
 1 file changed, 13 insertions(+)
 create mode 100644 p9.hs

diff --git a/p9.hs b/p9.hs
new file mode 100644
index 0000000..b190491
--- /dev/null
+++ b/p9.hs
@@ -0,0 +1,13 @@
+pack :: (Eq a) => [a] -> [[a]]
+pack = foldr elim []
+  where elim e [] = [[e]]
+        elim e p@(n:ns)
+          | e == head n = (e:n):ns 
+          | otherwise = [e]:p
+
+pack' (x:xs) = let (first,rest) = span (==x) xs
+               in (x:first) : pack' rest
+pack' [] = []
+
+pack'' (x:xs) = (x:takeWhile (==x) xs):(pack'' $ dropWhile (==x) xs)
+pack'' [] = []
-- 
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