Haskell -Main.HS：18：5：输入上的解析错误＆＃x2018; putstrln＆＃x2019;

发布于 2025-01-25 06:53:31 字数 890 浏览 1 评论 0原文

module Main where

reportResults :: [String] -> [Int] -> IO ()
reportResults fileNames exitCodes = do
    putStrLn "All Files"
    putStrLn "---------"
    putStr.unlines $ map ("    " ++) fileNames
    putStrLn ""

    let problems = filter (\p -> fst p /= 0) $ zip exitCodes fileNames

    putStrLn "Problematic Files"
    putStrLn "-----------------"
    mapM_ (putStrLn . showProblem) problems
                where showProblem :: (Int, String) -> String
                      showProblem (c, f) = "    " ++ show c ++ " - " ++ f

    putStrLn "Done!"  -- "Parse error on input...". OK if this line is removed.

main :: IO ()
main = do
    let fileNames = ["A", "B", "C", "D"]
    let exitCodes = [0,   1,   2,   3]
    reportResults fileNames exitCodes

如果我发表评论或删除有问题的行（第18行），则该代码可以正常工作，但是我真的很想保留它，也可以理解我在做错了什么。尝试了许多排列并搜索堆后，我仍然无法破解它。任何帮助将不胜感激。

原文

module Main where

reportResults :: [String] -> [Int] -> IO ()
reportResults fileNames exitCodes = do
    putStrLn "All Files"
    putStrLn "---------"
    putStr.unlines $ map ("    " ++) fileNames
    putStrLn ""

    let problems = filter (\p -> fst p /= 0) $ zip exitCodes fileNames

    putStrLn "Problematic Files"
    putStrLn "-----------------"
    mapM_ (putStrLn . showProblem) problems
                where showProblem :: (Int, String) -> String
                      showProblem (c, f) = "    " ++ show c ++ " - " ++ f

    putStrLn "Done!"  -- "Parse error on input...". OK if this line is removed.

main :: IO ()
main = do
    let fileNames = ["A", "B", "C", "D"]
    let exitCodes = [0,   1,   2,   3]
    reportResults fileNames exitCodes

The code works fine if I comment out, or remove, the offending line (line 18), but I would really like to retain it and also understand what I'm doing wrong. After trying many permutations and searching heaps, I still can't crack it. Any help would be greatly appreciated.

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梦里°也失望 2025-02-01 06:53:31

您可以在中定义showproblem 子句，因此：

reportResults :: [String] -> [Int] -> IO ()
reportResults fileNames exitCodes = do
    putStrLn "All Files"
    putStrLn "---------"
    putStr.unlines $ map ("    " ++) fileNames
    putStrLn ""

    let problems = filter (\p -> fst p /= 0) $ zip exitCodes fileNames

    putStrLn "Problematic Files"
    putStrLn "-----------------"
    let showProblem (c, f) = "    " ++ show c ++ " - " ++ f
    mapM_ (putStrLn . showProblem) problems
    putStrLn "Done!"  -- "Parse error on input...". OK if this line is removed.

You can define the showProblem function in a let clause, so:

reportResults :: [String] -> [Int] -> IO ()
reportResults fileNames exitCodes = do
    putStrLn "All Files"
    putStrLn "---------"
    putStr.unlines $ map ("    " ++) fileNames
    putStrLn ""

    let problems = filter (\p -> fst p /= 0) $ zip exitCodes fileNames

    putStrLn "Problematic Files"
    putStrLn "-----------------"
    let showProblem (c, f) = "    " ++ show c ++ " - " ++ f
    mapM_ (putStrLn . showProblem) problems
    putStrLn "Done!"  -- "Parse error on input...". OK if this line is removed.

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