haskell 求助
我是刚接触haskell，现在有个题目，有点不懂。要求如下：
1：
-- In this module you will implement the match queue data structure.
-- A match queue is essentially a First-In-First-Match-Out, linear data set.
-- It is like a FIFO queue, a new element will be always added to the end of the queue.
-- But retrieving as well as deleting is not always the head.
-- Retrieving and deleting operations are accompanied with a predicate,
-- and the result will be the first element, starting from the front of the queue,
-- that satisfies the predicate.
-- For instace, given a match queue [1, 2, 3, 4, 1, 2, 5]
-- and a predicate (written as a Haskell function): \x -> x > 3
-- A retrieving will get the element 4, and a deleting will make a new queue [1, 2, 3, 1, 2, 5].
-- If we do delete again, we will get [1, 2, 3, 1, 2, 5].
-- Below is the module structure. You need to implement the data type and all the operation functions
-- whose type are already specified. You can make the implementation based on the queue that we have
-- defined in the class (in the queue.hs file of samplecode package), or you can do from scratch.
-- Notice that you are not allowed to change the types!
-- Finish the code.
-- You'd better make a brief descrption of your implementation and a rough analysis of complexity.
module MatchQueue
( MatchQueue -- data types for match queue
, mqAdd
, mqMatchHead
, mqMatchDelete
, emptyQueue
, isEmpty
) where
emptyQueue :: MatchQueue
isEmpty :: MatchQueue a -> Bool
mqAdd :: MatchQueue a -> a -> MatchQueue a
mqMatchHead :: (a -> bool) -> MatchQueue a -> Maybe a --就是这里不会，怎么实现（）-> ->，我只懂 -> -> 实现该问题
mqMatchDelete :: (a -> bool) -> MatchQueue a -> MatchQueue a --就是这里不会，怎么实现（）-> ->，我只懂 -> -> 实现该问题
2，还有一题，要求如下：
--就是最好能满足序列为无穷的，紧急。（从右边删除满足条件，留下左边）
Implement dropWhile with foldr.
The normal definition of dropWhile is
dropWhile :: (a -> bool) -> [a] -> [a]
dropWhile p [] = []
dropWhile p (x:xs) = if p x then dropWhile p xs else (x:xs)
[解决办法]
这个不是张龙吗？你真舍得，50分啊
