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问题描述
示例：
是否有内置函数来替换haskell中给定索引处的元素？replaceAtIndex（2，foo，[bar，bar，bar]）
应该给：
[bar，bar，foo]我知道我可以创建自己的函数，但它似乎应该是内置的。
解决方案如果您需要更新特定索引处的元素，则列表不是最好的数据结构。您可能要考虑使用 Seq 。 htmlrel =noreferrer> Data.Sequence ，在这种情况下，您要查找的函数是 update :: Int - > a - > Seq a - > Seq a 。
> import Data.Sequence >更新2foo$ fromList [bar，bar，bar] fromList [bar，bar，foo]
Is there any built-in function to replace an element at a given index in haskell?
Example:
replaceAtIndex(2,"foo",["bar","bar","bar"])
Should give:
["bar", "bar", "foo"]I know i could make my own function, but it just seems it should be built-in.
解决方案If you need to update elements at a specific index, lists aren't the best data structure for that. You might want to consider using Seq from Data.Sequence instead, in which case the function you're looking for is update :: Int -> a -> Seq a -> Seq a.
> import Data.Sequence > update 2 "foo" $ fromList ["bar", "bar", "bar"] fromList ["bar","bar","foo"]
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