Parsing 防护上的分析错误

我正在实现merge sort的merge子例程。我在编译时收到以下错误消息：输入解析错误|

merge :: [Int] -> [Int] -> [Int]
merge xs ys = go xs ys []
    where go xs ys zs =
            |null ys              = zs ++ xs                     
            |null xs              = zs ++ ys                        
            |(head xs) <= head ys = go (tail xs) ys (head xs : zs)  
            |otherwise            = go xs (tail ys) (head ys : zs)

merge:：[Int]->[Int]->[Int]
合并xs ys=go xs ys[]
xs ys zs去哪里=
|空ys=zs++xs
|空xs=zs++ys
|（head xs）您可以通过删除
go xs ys zs
之后的
=
来修复语法错误-当定义带有保护的内容时，
=
只出现在每个保护之后，就像您已经有的那样

除此之外，如果您更多地使用模式匹配，您的代码将更干净。您可以使用模式
[]
来识别空列表和
（x:xs）
来识别非空列表，并将头和尾绑定到名称
x
和
xs
，等等，而不是先检查列表是否为
null
，然后再检查
头和
尾

merge :: [Int] -> [Int] -> [Int]
merge xs ys = go xs ys []
    where go xs [] zs          = zs ++ xs
          go [] ys zs          = zs ++ ys
          go (x:xs) (y:ys) zs
              | x <= y         = go xs (y:ys) (x:zs)
              | otherwise      = go (x:xs) ys (y:zs)

merge:：[Int]->[Int]->[Int]
合并xs ys=go xs ys[]
其中go xs[]zs=zs++xs
go[]ys zs=zs++ys
go（x:xs）（y:ys）zs
|x您在
go xs ys zs
之后有一个额外的
=
——当定义带有防护装置的内容时，
=
只在每个防护装置之后出现，就像您已经有的那样。