Question

我是Haskell的新手。在下面的示例中，该函数从列表中删除所有特定元素，并返回一个新列表。另外，我正在尝试使用辅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。

我很感激找到错误原因的任何帮助。

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

where子句中的所有绑定必须从同一列开始，

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。

辅助函数，给出解析错误

1 个答案: