红黑树的实现可以有多精简（各种语言随意）？ 第1页

       module RedBlackSet( empty                   , member                   , insert                   ) where  data Tree a = Empty             | T Color (Tree a) a (Tree a)  data Color  = R             | B  empty :: Ord a => Tree a empty = Empty  member :: Ord a => Tree a -> a -> Bool member (T _ left e right) x | x == e = True                             | x < e  = member left x                             | x > e  = member right x member Empty _                       = False  insert :: Ord a => a -> Tree a -> Tree a insert x s = let T _ a y b = ins s              in  T B a y b         where           ins s'@(T color a' y' b')                     | x < y'    = build color (ins a') y' b'                     | x > y'    = build color a' y' (ins b')                     | otherwise = s'           ins Empty             = T R Empty x Empty  build :: Color -> Tree a -> a -> Tree a -> Tree a build B (T R (T R a x b) y c) z d = T R (T B a x b) y (T B c z d) build B (T R a x (T R b y c)) z d = T R (T B a x b) y (T B c z d) build B a x (T R (T R b y c) z d) = T R (T B a x b) y (T B c z d) build B a x (T R b y (T R c z d)) = T R (T B a x b) y (T B c z d) build color left x right          = T color left x right