当Haskell中的功能不正确时，我只能切片列表？
当功能不正确时，我想切片列表，但是我不知道在其他情况下我必须回馈什么。你有什么想法吗？
Example :
sliceBy odd [1..5] == [[1],[2],[3],[4],[5]]
sliceBy odd [1,3,2,4,5,7,4,6] == [[1,3],[2,4],[5,7],[4,6]]
sliceBy even [1,3,2,4,5,7,4,6] == [[],[1,3],[2,4],[5,7],[4,6]]
sliceBy :: (a -> Bool) -> [a] -> [[a]]
sliceBy _ [] = []
sliceBy _ [x] = [[x]]
sliceBy f (x:xs)
| f x = [x] : sliceBy f xs
| otherwise = ??
I would like to slice my list when the function is not true, but I do not have an idea what I have to give back in the otherwise case. Do you have any idea ?
Example :
sliceBy odd [1..5] == [[1],[2],[3],[4],[5]]
sliceBy odd [1,3,2,4,5,7,4,6] == [[1,3],[2,4],[5,7],[4,6]]
sliceBy even [1,3,2,4,5,7,4,6] == [[],[1,3],[2,4],[5,7],[4,6]]
sliceBy :: (a -> Bool) -> [a] -> [[a]]
sliceBy _ [] = []
sliceBy _ [x] = [[x]]
sliceBy f (x:xs)
| f x = [x] : sliceBy f xs
| otherwise = ??
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您可以使用
past （a - ＆gt; bool） - ＆gt; [a] - ＆gt; （[a]，[a]）和break ::（a - ＆gt; bool） - ＆gt; [a] - ＆gt; （[a]，[a]）获得列表所能/不满足给定谓词的最长前缀。因此，您可以使用它来制作两个函数sliceby和slicebynot相互调用：您需要填写
…parts。因此，这两个功能应该互相呼叫。You can make use of
span :: (a -> Bool) -> [a] -> ([a], [a])andbreak :: (a -> Bool) -> [a] -> ([a], [a])to get the longest prefixes where the list does/does not satisfy a given predicate. You thus can use this to make two functionssliceByandsliceByNotthat call each other:Where you need to fill in the
…parts. The two functions thus should call each other.