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我正在尝试接收一个 CSV 文件，对其进行错误检查，然后打印错误消息。

mapM_ (appendFile filePath) (errorCheck 函数返回一个 [string])

这可行，但是当我运行它但在很长的 CSV 上它会耗尽内存。我认为问题在于它太懒了，并且在执行任何操作之前将整个 CSV 加载到内存中。我尝试使用 BangPatterns 强制执行严格性，但我不确定我是否正确使用它，因为它没有帮助

我可以提供更多信息或代码，但我不确定与我的问题相关的内容

代码：

main = do
    safeRead s = catch (readFile s) $ \_ -> return ""

    filePath <- safeRead "in.txt"
    file <- safeRead filePath

    --save the errors
    writeFile (createErrorFilePath filePath) (getFileName $ filePath ++ "\n")
    let !addToErr = do appendFile (createErrorFilePath filePath) 

    mapM_ addToErr (map ('\n':) (errorCheckFile (( \(Right x) -> x )  (parseCSV file)) (errorCheckCols (checkCols . head $ (( \(Right x) -> x )  (parseCSV file))) errorMsgs)))
    --exit with correct number
    exitWith . ExitFailure . exitCtrl $ (errorCheckFile (( \(Right x) -> x )  (parseCSV file)) (errorCheckCols (checkCols $ head $ (( \(Right x) -> x )  (parseCSV file))) errorMsgs)) 

--decides what value to exit with, depends on if errors, warnings or nothing
exitCtrl :: [String] -> Int
exitCtrl [] = 1
exitCtrl (line:rest) 
    | ("ERROR:") == take 6 line = 3
--    | elem ("WARNING:") line = 1
    | otherwise = exitCtrl rest

--gets a files name given a filepath                
getFileName :: String -> String
getFileName filePath =  reverse $ takeWhile (/= '\\') (reverse filePath)

--changes the input filepath to create a new error file at the same location
createErrorFilePath :: String -> String
createErrorFilePath pathIn = (reverse $ drop 4 (reverse pathIn)) ++ "_error_log.txt"

--check if any of the columns errored
errorCheckCols :: [Int] -> [String] -> String
errorCheckCols cols errors 
    | errorPos == Nothing = "All headings are accounted for :)"
    | otherwise = errors !! (fromJust errorPos)
        where errorPos = findIndex (== 1-2) cols

--This takes the file and if any of the columns don't exists, tells you, otherwise it error checks the database    
errorCheckFile :: [[String]] -> String -> [String]
errorCheckFile [] _ = ["ERROR: No Data"]
errorCheckFile (headings:[]) colErrorMsg = ["ERROR: No Data"]
errorCheckFile (headings:info) colErrorMsg
    | length headings > 25 = ["ERROR: Too many Columns of data"]
    | colErrorMsg == "All headings are accounted for :)" = 
            checkDB 
                info 
                (findCol "example name 1" headings 3) 
                (findCol "example name 2" headings 5) 
                (findCol "example name 3" headings 5) 
                (findCol "example name 4" headings 3) 
                (findCol "example name 5" headings 3) 
                (findCol "example name 6" headings 3) 
                (findCol "example name 7" headings 8) 
                (findCol "example name 8" headings 3) 
                (findCol "example name 9" headings 15) 
                (findCol "example name 10" headings 15) 
                (findCol "example name 11" headings 3) 
                (findCol "example name 12" headings 3) 
                (findCol "example name 13" headings 9) 
                (findCol "example name 14" headings 16) 
                (findCol "example name 15" headings 9) 
                (findCol "example name 16" headings 16) 
                (findCol "example name 17" headings 3) 
                (findCol "example name 18" headings 3) 
                (findCol "example name 19" headings 8) 
                (findCol "example name 20" headings 3) 
                ((findCol "example name 21" headings 20) + (findCol "example name 21 alt" headings 20) + 1) 
                (findCol "example name 22" headings 22) 
                (findCol "example name 23" headings 3) 
                (findCol "example name 24" headings 3) 
                (findCol "example name 25" headings 9) 
                1
    | otherwise = [colErrorMsg]



--given the inputs headings, finds the positions if each row by name 
checkCols :: [String] -> [Int]
checkCols headings = [(findCol "example name 1" headings 3),
                (findCol "example name 2" headings 5), 
                (findCol "example name 3" headings 5), 
                (findCol "example name 4" headings 3), 
                (findCol "example name 5" headings 3), 
                (findCol "example name 6" headings 3), 
                (findCol "example name 7" headings 8), 
                (findCol "example name 8" headings 3),
                (findCol "example name 9" headings 15), 
                (findCol "example name 10" headings 15), 
                (findCol "example name 11" headings 3), 
                (findCol "example name 12" headings 3), 
                (findCol "example name 13" headings 9), 
                (findCol "example name 14" headings 16), 
                (findCol "example name 15" headings 9), 
                (findCol "example name 16" headings 16), 
                (findCol "example name 17" headings 3), 
                (findCol "example name 18" headings 3), 
                (findCol "example name 19" headings 8), 
                (findCol "example name 20" headings 3), 
                ((findCol "example name 21" headings 20) + (findCol "example name 21 alt" headings 20) + 1), 
                (findCol "example name 22" headings 22), 
                (findCol "example name 23" headings 3), 
                (findCol "example name 24" headings 3), 
                (findCol "example name 25" headings 9)]


-- [[String]] Intx25 Int(count) returns a [String]
checkDB :: [[String]] -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> [String]
checkDB [] _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ = ["ERROR: Filename given does not exist"]
checkDB (lastRow:[]) pos1 pos2 pos3 pos4 pos5 pos6 pos7 pos8 pos9 pos10 pos11 pos12 pos13 pos14 pos15 pos16 pos17 pos18 pos19 pos20 pos21 pos22 pos23 pos24 pos25 count
    | map (toUpper) (lastRow !! pos4) == "ASD" = checkASD lastRow pos1 pos2 pos3 pos5 pos6 pos7 pos8 pos9 pos10 pos11 pos12 pos13 pos14 pos15 pos16 pos17 pos18 pos19 pos20 pos21 pos22 pos23 count
    | map (toUpper) (lastRow !! pos4) == "QWE" || map (toUpper) (lastRow !! pos4) == "DPS" = checkQWE lastRow pos1 pos2 pos3  pos5 pos6 pos7 pos8 pos9 pos10 pos11 pos12 pos13 pos14 pos15 pos16 pos18 pos19 pos24 pos25 pos17 count 
    | otherwise = ["ERROR: identifier not valid on line " ++ (show count)]
checkDB (firstRow:otherRows) pos1 pos2 pos3 pos4 pos5 pos6 pos7 pos8 pos9 pos10 pos11 pos12 pos13 pos14 pos15 pos16 pos17 pos18 pos19 pos20 pos21 pos22 pos23 pos24 pos25 count
--    | count `mod` 50 == 0 = []
    | map (toUpper) (firstRow !! pos4) == "ASD" = checkASD firstRow pos1 pos2 pos3 pos5 pos6 pos7 pos8 pos9 pos10 pos11 pos12 pos13 pos14 pos15 pos16 pos17 pos18 pos19 pos20 pos21 pos22 pos23 count ++ checkDB otherRows pos1 pos2 pos3 pos4 pos5 pos6 pos7 pos8 pos9 pos10 pos11 pos12 pos13 pos14 pos15 pos16 pos17 pos18 pos19 pos20 pos21 pos22 pos23 pos24 pos25 (count+1)
    | map (toUpper) (firstRow !! pos4) == "QWE" || map (toUpper) (firstRow !! pos4) == "DPS" = checkQWE firstRow pos1 pos2 pos3  pos5 pos6 pos7 pos8 pos9 pos10 pos11 pos12 pos13 pos14 pos15 pos16 pos18 pos19 pos24 pos25 pos17 count ++ checkDB otherRows pos1 pos2 pos3 pos4 pos5 pos6 pos7 pos8 pos9 pos10 pos11 pos12 pos13 pos14 pos15 pos16 pos17 pos18 pos19 pos20 pos21 pos22 pos23 pos24 pos25 (count+1)
    | otherwise = ["ERROR: identifier not valid on line " ++ (show count)] ++ checkDB otherRows pos1 pos2 pos3 pos4 pos5 pos6 pos7 pos8 pos9 pos10 pos11 pos12 pos13 pos14 pos15 pos16 pos17 pos18 pos19 pos20 pos21 pos22 pos23 pos24 pos25 (count+1) 

--collection of error checking methods for ASD rows
checkASD :: [String] -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> [String]
checkASD row pos1 pos2 pos3 pos5 pos6 pos7 pos8 pos9 pos10 pos11 pos12 pos13 pos14 pos15 pos16 pos17 pos18 pos19 pos20 pos21 pos22 pos23 count
    | sum ans == 0 = []
    | (findIndex (>=20) ans /= Nothing && findIndex (>0) ans /= Nothing) = ["WARNING: At line " ++ (show count) ++ " at column(s) " ++ (show (cols!!(fromJust(findIndex (>=20) ans)) + 1))]
    | findIndex (>=20) ans /= Nothing = ["WARNING: At line " ++ (show count) ++ " at column(s) " ++ (show (cols!!(fromJust(findIndex (>=20) ans)) + 1)) ++ "\nERROR: At line " ++ (show count) ++ " at column(s) " ++ unwords( map show( map (+1) (map (cols!!) (findIndices (>0) (init ans)))))]
    | otherwise = ["ERROR: At line " ++ (show count) ++ " at column(s) " ++ unwords( map show( map (cols!!) (findIndices (>0) ans))) ]
    where 
         ans = [errorCheck (row!!pos1) ["01","02","03","04","05"],
                errorCheck (row!!pos2) ["3","4"],
                errorCheck (row!!pos3) ["1","2","3","4","5","6","7","8","9","10","11","12","13","14","15","16","17","18","19","20"],
                checkTypeLength (row!!pos5) isDigit 5,
                sum [ checkLength (row!!pos6) 12, errorCheckNL (row!!pos6) ],
                checkDate (row!!pos7),
                checkTypeLength (row!!pos8) checkSex 1,
                checkDate (row!!pos9),
                checkDate (row!!pos10),
                checkLength (row!!pos11) 5,
                checkTypeLength (row!!pos12) isDigit 5,
                checkMoney (row!!pos13),
                checkMoney (row!!pos14),
                checkMoney (row!!pos15),
                checkMoney (row!!pos16), 
                checkLength (row!!pos17) 10,
                checkLength (row!!pos18) 2,
                checkDate (row!!pos19), 
                checkTypeLength (row!!pos20) isDigit 5,
                checkTypeLength (row!!pos21) isDigit 5,
                checkLength (row!!pos22) 1,
                checkLength (row!!pos23) 1]
         cols = [pos1, pos2, pos3, pos5, pos6, pos7, pos8, pos9, pos10, pos11, pos12, pos13, pos14, pos15, pos16, pos17, pos18, pos19, pos20, pos21, pos22, pos23]
         --cols is a quick fix for finding where errors have occured

--collection of error checking methods for QWE/DPS rows
checkQWE :: [String] -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> [String]    
checkQWE row pos1 pos2 pos3 pos5 pos6 pos7 pos8 pos9 pos10 pos11 pos12 pos13 pos14 pos15 pos16 pos18 pos19 pos24 pos25 pos17 count
    | sum ans == 0 = []
    | (findIndex (>=20) ans /= Nothing && findIndex (>0) ans /= Nothing) = ["WARNING: At line " ++ (show count) ++ " at column(s) " ++ (show (cols!!(fromJust(findIndex (>=20) ans)) + 1))]
    | findIndex (>=20) ans /= Nothing = ["WARNING: At line " ++ (show count) ++ " at column(s) " ++ (show (cols!!(fromJust(findIndex (>=20) ans)) + 1)) ++ "\nERROR: At line " ++ (show count) ++ " at column(s) " ++ unwords( map show( map (+1) (map (cols!!) (findIndices (>0) (init ans)))))]
    | otherwise = ["ERROR: At line " ++ (show count) ++ " at column(s) " ++ unwords( map show (map (cols!!) (findIndices (>0) ans))) ]
    where
         ans = [errorCheck (row!!pos1) ["01","02","03","04","05","06","07","08","1","2","3","4","5","6","7","8"],
                errorCheck (row!!pos2) ["1","2","3","4"],
                errorCheck (row!!pos3) ["1","2","3","4","5","6","7","8","9","10","11","12","13","14","15","16","17","18","19","20","21","22","23","24","25","26","27","28","29","30","31","32"],
                checkTypeLength (row!!pos5) isDigit 5,
                sum [ checkLength (row!!pos6) 12, errorCheckNL (row!!pos6) ],
                checkDate (row!!pos7),
                checkTypeLength (row!!pos8) checkSex 1,
                checkDate (row!!pos9),
                checkDate (row!!pos10),
                checkLength (row!!pos11) 5,
                checkTypeLength (row!!pos12) isDigit 5,
                checkMoney (row!!pos13),
                checkMoney (row!!pos14),
                checkMoney (row!!pos15),
                checkMoney (row!!pos16),
                checkLength (row!!pos18) 2,
                checkDate (row!!pos19),
                checkDate (row!!pos24), 
                checkMoney (row!!pos25),
                checkQWEpos17 (row!!pos17)]
         cols = [pos1, pos2, pos3, pos5, pos6, pos7, pos8, pos9, pos10, pos11, pos12, pos13, pos14, pos15, pos16, pos18, pos19, pos24, pos25, pos17]
         --cols is a quick fix for finding where errors have occured


--checks that a string is 'm' or 'f'
checkSex :: Char -> Bool
checkSex input 
    | toLower input == 'm' || toLower input == 'f' = True
    | otherwise = False

--finds if a row has something other than 1 type and are of a certain length
checkTypeLength :: String -> (Char -> Bool) -> Int -> Int
checkTypeLength [] _ _ = 1
checkTypeLength el isType maxSize
    | length el > 0 && length el <= maxSize && (and $ map isType el) = 0
    | otherwise = 1

--finds elements that exceed a certain length
checkLength :: String -> Int -> Int
checkLength [] _ = 1
checkLength el maxSize
    | length el <= maxSize && length el > 0 = 0
    | otherwise = 1

--finds a columns position given its name and the list of column names, else returns -1
findCol :: String -> [String] -> Int -> Int
findCol colName header unique   --unique is the number of letters of each word that need to be compared
    | findMatch /= Nothing = fromJust findMatch
    | otherwise = -1
    where findMatch = findIndex (==(map (toLower) (take unique colName))) (map (map toLower) (map (take unique) header))

--finds if a line where the element is not a letter and number ONLY, returns col num or 0
errorCheckNL :: String -> Int
errorCheckNL [] = 1
errorCheckNL (el1:el2:el3:rest)
    | isDigit el1 && isDigit el2 && isDigit el3 && and(map isLetter rest) = 0 --return Nothing?
    | otherwise = 2
errorCheckNL others = 3

-- given a row, the column num to check, options of what the column and a counter==0, returns row num or 0
errorCheck :: String -> [String] -> Int
errorCheck [] _ = 1
errorCheck el options 
    | map toLower el `elem` options = 0
    | otherwise = 1

--finds if a date is valid given a row, the column num to check and a counter=0, returns row num or 0
checkDate :: String -> Int
checkDate [] = 1
checkDate el 
    | sepPos1 == Nothing = 1 --error: this is not formated as a date, there's no separator
    | sepPos2 == Nothing = 2 --error: this is not formated as a date, there's no separator
    | day `notElem` ["1","2","3","4","5","6","7","8","9","10","11","12","13","14","15","16","17","18","19","20","21","22","23","24","25","26","27","28","29","30","31"] = 3
    | (map toLower month) `notElem` ["jan","feb","mar","apr","may","jun","jul","aug","sep","oct","nov","dec"] = 4   --error: month is not valid
    | length (tail year) == 4 && and (map isDigit (tail year)) = 22
    | length (tail year) == 2 && and (map isDigit (tail year)) = 0
    | otherwise = 5
    where 
        sepPos1 = findIndex (== '-') el            --maybe
        (day, rest) = splitAt (fromJust sepPos1) el
        sepPos2 = findIndex (== '-') (tail rest)   --maybe
        (month, year) = splitAt (fromJust sepPos2) (tail rest)

--checks that quantities of money are presented correctly
checkMoney :: String -> Int
checkMoney [] = 4
checkMoney cash 
    | decimalPoint == Nothing && checkTypeLength cash isDigit 9 /= 0 = 1  --error: not numbers
    | decimalPoint /= Nothing && checkTypeLength (tail cents) isDigit 2 /= 0 = 2 --error: not numbers after the decimal point
    | decimalPoint /= Nothing && checkTypeLength euros isDigit 9 /= 0 = 3 --error: not numbers after the decimal point
    | otherwise = 0
    where
        decimalPoint = findIndex (== '.') cash     --maybe
        (euros, cents) = splitAt (fromJust decimalPoint) cash
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1 回答 1

5

这段代码

(( \(Right x) -> x )  (parseCSV file))

表示几乎不可能parseCSV在不消耗整个文件的情况下逐步解析文件并开始返回部分结果。这是不可能的，如果

  • parseCSV的结果应Left something在输入格式错误的情况下，在格式正确Right result的输入和
  • 如果格式正确，则应消耗整个输入

在完整的输入被消费之前，无法知道解析是否成功，因此无法确定结果是Left errorMessage还是Right result。

此外，您会使用两次解析结果，一次用于将消息附加到日志文件，一次用于确定退出代码。第二个用途持有对它的引用，因此它（或者，在多次评估的情况下，文件内容）不能被​​垃圾收集。

另一方面，您在四个地方使用了那段代码。根据编译器执行公共子表达式消除的方式，该文件最多被解析四次。将解析结果绑定到名称以避免多次评估更安全。

如果您知道您的文件格式正确，则可以通过分块解析文件来减少空间使用，例如逐行解析并只执行一次遍历（记录和确定退出代码相结合）。Control.Monad.foldM该遍历的合适模式是

logAndUpdate file exitCode record = do
    appendFile file (message record)
    return $! update exitCode (exitInfo record)

主要：

exitCode <- foldM (logAndUpdate filename) 0 (parsedRecords)
exitWith $ ExitCode exitCode

如果行是独立的，则类似的策略是可能的，因此畸形行的存在不会影响之前和之后格式良好行的处理，然后每行将被解析为Either ParseError Record. 如果格式错误的行仅影响后面的行，而不影响前面的行，则仍然可以通过在遇到格式错误的行时停止解析或切换解析器来实现。

但是，如果格式错误的行使整个文件无效，则可能无法在或多或少的恒定空间中执行此操作。如果预期的结构允许，它可以分两遍完成，一遍用于检查格式正确性，另一遍用于解析。

于 2012-04-01T22:29:07.727 回答