programing_in_Haskell_4_1.hs

halve :: [a] -> ([a], [a])
halve xs = splitAt n xs
            where n = length xs `div` 2
-- 実行例
--halve [1, 2, 3, 4, 5, 6]
--([1, 2, 3], [4, 5, 6])

-- drop n xs ... リストからn個の要素を取り除く
-- splitAt n xs = (take n xs, drop n xs) ... リストをn番目の要素のところで分割する