[英]What kinds of recursions are used in the definitions of `foldr` and `foldl`?
foldr :: (a -> b -> b) -> b -> [a] -> b
foldr f v [] = v
foldr f v (x:xs) = f x (foldr f v xs)
和
foldl :: (a -> b -> a) -> a -> [b] -> a
foldl f v [] = v
foldl f v (x:xs) = foldl f (f v x) xs
似乎使用不同種類的遞歸。
foldr
和foldl
的定義中使用了哪些遞歸?
謝謝。
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