幫助函數，給出解析錯誤

Question

我是Haskell的新手。在下面的例子中，該函數從列表中刪除所有出現的特定元素並返回一個新列表。另外，我正在嘗試使用幫助函數來獲取返回的列表並輸出它的長度。

我遇到的問題是編譯期間的解析錯誤，指向包含delete _ [] = []的行。

我很感激任何幫助找出錯誤的原因。

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子句中的綁定必須在同一列開始，

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。