小编use*_*228的帖子

我被要求实现一个使用以下配置文件的函数:

maybe_divide :: Maybe Integer -> Maybe Integer -> Maybe Integer

并以下列方式回应:

> maybe_divide (Just 5) (Just 2) 
Just 2
> maybe_divide (Just (-5)) (Just 2) 
Just (-3)
> maybe_divide (Just (-5)) (Just 0) 
Nothing
> maybe_divide Nothing (Just 1) 
Nothing
> maybe_divide (Just 1) Nothing
Nothing

我写了以下但它不会编译.你们有什么建议吗？

maybe_divide :: Maybe Integer -> Maybe Integer -> Maybe Integer
maybe_divide x y = case x of
    Just x' -> case y of 
        Just y'
            | y' == 0 -> Nothing  
            | …