为什么我从 stdin 读取字符串时得到 "Prelude.read : no parse"

Question

我运行遇到 forM_ 循环打印结果的问题。我期待最后一个 putStrLn 函数输出结果。对于那些想要 link 问题的人 - https://www.hackerrank.com/challenges/sherlock-and-anagrams

--Returns a sublist of xs from 'from' to 'to'
slice from to xs = take (to - from + 1) (drop from xs)

--Checks if all elements in list are identical
allTheSame xs = and $ zipWith (==) xs (tail xs)

--Handles validating an anagram
checkForTwoOccurences :: [Char] -> [[Char]] -> Bool
checkForTwoOccurences occ arr
    | allTheSame occ == True = False 
    | reverse occ == occ = False
    | (occ `elemIndex` arr /= Nothing) = True
    | otherwise = False

--Returns the count of anagrams that are substrings of s - n is length of s
findAnagrams s n = 
    let res = concat $ [ tail $ inits $ slice x (n-1) s | x <- [0..n-1] ]
    in foldl (\acc x -> if (checkForTwoOccurences (reverse x) res) then (succ acc) else acc) 0 res


main :: IO ()
main = do 

    t_temp <- getLine
    let t = read t_temp :: Int

    forM_ [1..t] $ \a0  -> do
        s_temp <- getLine
        let s = read s_temp :: String
        putStrLn $ show $ findAnagrams s $ length s

Answer 1

如评论所述，您不需要 "read" 您的字符串 -- 它已经是一个字符串！

所以改变

    s_temp <- getLine
    let s = read s_temp :: String
    putStrLn $ show $ findAnagrams s $ length s

至

    s <- getLine
    putStrLn $ show $ findAnagrams s $ length s

应该解决该错误。

为什么我从 stdin 读取字符串时得到 "Prelude.read : no parse"

Why am I getting "Prelude.read : no parse" on reading a string from stdin

monads

haskell