过滤列表中的位置，Haskell [英] Filter positions in a list, Haskell

问题描述

我需要打印奇数索引的元素.当前正在打印索引.

I need to print the elements of odd index. Currently is printing index.

我不明白如何打印此索引的元素?

I don't understand how I can print elements of this index?

f :: [Int] -> [Int]
f lst = filter odd [0..length lst]

-- I can't edit this part
main = do
   inputdata <- getContents
   mapM_ (putStrLn. show). f. map read. lines $ inputdata

推荐答案

如果您想徒步"进行此操作:

If you want to do this "on foot":

odds [] = []
odds [x] = []
odds (e1:e2:xs) = e2 : odds xs

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