帮助函数，给出解析错误

Question

我是Haskell的新手。在下面的例子中，该函数从列表中删除所有出现的特定元素并返回一个新列表。另外，我正在尝试使用帮助函数来获取返回的列表并输出它的长度。

我遇到的问题是编译期间的解析错误，指向包含delete _ [] = []的行。

我很感激任何帮助找出错误的原因。

countDelete y (x:xs) = length outputList 
    where outputList = delete y (x:xs) 

    delete _ [] = [] 
    delete y (x:xs) | x==y = delete y xs 
        | otherwise = x:delete y xs 

Answer 1

所有where子句中的绑定必须在同一列开始，

countDelete y (x:xs) = length outputList 
    where 
    outputList = delete y (x:xs) 

    delete _ [] = [] 
    delete y (x:xs) 
     | x==y  = delete y xs 
     | otherwise = x:delete y xs 

作品。