haskell从列表列表中删除所有出现的给定值 [英] haskell removes all occurrences of a given value from within a list of lists

问题描述

我想从列表清单中删除所有出现的给定值。例如，
输入：

I would like to remove all occurrences of a given value from within a list of lists. For example, input:

'a' ["abc", "bc", "aa"] 

输出：

output:

 ["bc", "bc", ""]

到目前为止：

remove :: Eq a => a -> [[a ]] -> [[a ]]
remove y xs = filter(\x -> x/= y) xs

我收到一个错误，提前谢谢。

I'm getting an error, thank you in advance.

推荐答案

您需要映射到外部列表。

You need to map over the outer lists.

remove y xs = map (filter(\x -> x/= y)) xs

您实际上并不需要lambda表达式，更好：

You don't actually need a lambda here, nicer:

remove y xs = map (filter(/=y)) xs

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