--- a/Haskell/baby.hs	Wed Mar 26 18:13:52 2014 +0900
+++ b/Haskell/baby.hs	Sun May 11 03:49:24 2014 +0900
@@ -48,3 +48,60 @@
                   ++ case ls of [] -> "empty."
                                 [x] -> "a singleton list."
                                 xs -> "a longer list."
+
+maximum' :: (Ord a) => [a] -> a
+maximum' [] = error "maximum of empty list!"
+maximum' [x] = x
+maximum' (x:xs) = max x (maximum' xs)
+
+replicate' :: Int -> a -> [a]
+replicate' n x
+    | n <= 0    = []
+    | otherwise = x : replicate' (n-1) x
+
+take' :: Int -> [a] -> [a]
+take' n _
+    | n <= 0    = []
+take' _ []      = []
+take' n (x:xs) = x : take' (n-1) xs
+
+reverse' :: [a] -> [a]
+reverse' [] = []
+reverse' (x:xs) = reverse' xs ++ [x]
+
+repeat' :: a -> [a]
+repeat' x = x : repeat' x
+
+quicksort :: (Ord a) => [a] -> [a]
+quicksort [] = []
+quicksort (x:xs) =
+    let smallerOrEqual = [a| a<-xs, a<= x]
+        larger = [a | a<-xs, a>x]
+    in  quicksort smallerOrEqual ++ [x] ++ quicksort larger
+
+-- Chapter 5
+
+multThree :: Int -> Int -> Int -> Int
+multThree x y z = x * y * z
+
+compareWithHundred :: Int -> Ordering
+compareWithHundred x = compare 100 x
+
+compareWithHundred' :: Int -> Ordering
+compareWithHundred' = compare 100
+
+zipWith' :: (a -> b -> c) -> [a] -> [b] -> [c]
+-- 型推論をさせると zipWith' :: (t -> t1 -> a) -> [t] -> [t1] -> [a] となる
+zipWith' _ [] _ = []
+zipWith' _ _ [] = []
+zipWith' f (x:xs) (y:ys) = f x y : zipWith' f xs ys
+
+flip' :: (a -> b -> c) -> (b -> a -> c)
+flip' f = g
+    where g x y = f y x
+
+chain :: Integer -> [Integer]
+chain 1 = [1]
+chain n
+    | even n = n : chain (n `div` 2)
+    | odd  n = n : chain (n * 3 + 1)