如何改进此Haskell源的结构？

必须说，我发现Haskell中的编程比我尝试过的任何其他语言都需要更多的认知强度。我不确定我是否非常关心延迟计算或monad，但我确实很欣赏某些功能方面，静态类型检查，并且不需要一个巨大的VM来运行

我一直在写一个基于EXIF的重命名图像的短程序，现在有了一些有用的东西。我希望有人能就源代码的总体结构发表专家意见，包括我做对了什么/错了什么，以及如何改进和使代码更加简洁。我不会费心发布整个程序，但下面是很多总体结构。谢谢

import Control.Applicative
import Control.Monad.Error
import Data.Char
import Data.Either
import Data.List
import Data.Maybe
import Data.Time.Format
import Data.Time.LocalTime
import System.Console.GetOpt
import System.Directory
import System.Environment
import System.FilePath
import System.Locale
import System.IO.Error
import Text.Printf

import Album.Utils
import Album.Exif
import Album.Error

-- -----------------------------------------------------------------------
-- Main

main = do
  r <- try main0
  case r of
    Left err -> do
      printf "Error type:     %s\n" $ (show $ ioeGetErrorType err)
      printf "Error string:   %s\n" $ (ioeGetErrorString err)
      printf "Error filename: %s\n" $ (maybe "None" id $ ioeGetFileName err)
      printf "Error handle:   %s\n" $ (maybe "None" show $ ioeGetHandle err)
    Right _  -> return ()

-- Process arguments
main0 = do
  args <- getArgs
  case processArgs args desc of
    (True, _, usage) -> showUsage usage
    (False, (flags, fns, []), usage) -> do
      rv <- runErrorT $ main1 flags fns
      either (\e -> showErrs [show e] usage) (const $ return ()) rv
    (False, (_, _, errs), usage) -> showErrs errs usage
  where
    desc = "Rename and catalog media.\n" ++
           "Usage: album -n <albumname> <options> <media files>\n"

-- Sanity check
main1 flags fns = do

    -- Check name
    albName <- maybe (throwError AlbumNameError) return $ albumName flags

    -- Check for duplicate media
    let dups = nub $ fns \\ nub fns
    unless (null dups) $ throwError $ MediaDuplicateError dups

    -- Check for valid filenames
    (haves, havenots) <- liftIO $ filesExist fns
    unless (null havenots) $ throwError $ MediaNotFoundError havenots
    when (null haves)      $ throwError MediaNotSpecifiedError

    -- Check exiftool existence
    tool0 <- liftIO $ findExecutable "exiftool"
    tool  <- maybe (throwError ExifToolNotFoundError) return tool0

    -- Get EXIF attributes
    exifs0 <- liftIO $ getExifs tool fns
    exifs  <- either (throwError . ExifParseError) return exifs0

    -- Check for exiftool errors
    let bads = findExifs "ExifTool:Error" exifs
    unless (null bads) $ throwError $ MediaBadError $ map fst bads

    -- Check for timestamps
    let infos0 = map (\(n,e) -> (n, exifToDateTime e)) exifs
    let nodates = filter (isNothing . snd) infos0
    unless (null nodates) $ throwError $ MediaDateTimeTagError $ map fst nodates

    let infos = map (\(n,Just dt) -> (n,dt)) infos0
    main2 albName infos

-- Do renames
main2 albName infos = do

    -- Album folder name
    let mints     = minimum $ map snd infos
    let mintsiso  = formatTime defaultTimeLocale "%Y%m%d" mints
    let albFolder = printf "%s - %s" mintsiso albName

    -- Get list of existing media
    albExist <- liftIO $ doesDirectoryExist albFolder
    (albCreate, existing) <- case albExist of
        False -> return (True, [])
        True -> do
            e <- liftIO $ filter ((/= ".") . nub) <$> getDirectoryContents albFolder
            return (False, e)

    -- Rename list
    let rens0 = mediaNames albName infos existing
    let rens1 = map (\(a,b) -> (a, combine albFolder b)) rens0
    let len = maximum $ map (length . fst) rens1

    if albCreate
      then do
        liftIO $ printf "Creating folder: %s\n" albFolder
        liftIO $ createDirectory albFolder
      else 
        return ()

    forM_ rens1 $ \(oldf, newf) -> do
        liftIO $ printf "%*s >>> %s\n" len oldf newf
        liftIO $ renameFile oldf newf

    return ()

showErrs errs usage = do
    putStrLn $ concatMap ("Error: " ++ ) errs
    return ()

showUsage usage = do
    putStrLn usage
    return ()

-- -----------------------------------------------------------------------
-- Rename

mediaNames albName infos existing = go existing (map cands infos)
    where
    go es [] = []
    go es ((fn,cs):css) = let p = unused cs es in (fn,p):go (p:es) css
    unused cs es = fromJust $ find (`notElem` es) cs
    cands (fn,dt) = (fn, map (++ ext) (pref:alts))
        where
        pref  = printf "%s - %s" (ft dt) albName
        ft dt = formatTime defaultTimeLocale "%Y%m%dT%H%M%S" dt
        alts  = map (printf "%s (%02d)" pref) ([1..] :: [Int])
        ext   = map toLower (takeExtension fn)

-- -----------------------------------------------------------------------
-- Arguments

data Option = OptionAlbumName String
            | OptionHelp
            deriving (Eq, Show)

processArgs args desc = (elem OptionHelp flags, opts, usage)
  where
    opts@(flags, fns, errs)  = getOpt RequireOrder conf args
    usage = usageInfo desc conf
    conf  = [
      Option "n" ["name"] (ReqArg OptionAlbumName "NAME") "Album name",
      Option "h" ["help"] (NoArg OptionHelp) "Help"]

albumName (OptionAlbumName n:xs) = Just n
albumName (x:xs)                 = albumName xs
albumName []                     = Nothing

导入控件。应用程序
导入控制.Monad.Error
导入数据.Char
导入数据。或者
导入数据。列表
导入数据，也许吧
导入Data.Time.Format
导入Data.Time.LocalTime
导入System.Console.GetOpt
导入系统目录
导入系统。环境
导入System.FilePath
导入系统语言环境
导入系统IO错误
导入文本.Printf
导入相册.Utils
导入相册.Exif
导入相册。错误
-- -----------------------------------------------------------------------
--主要
main=do
r do
printf“错误类型：%s\n”$（显示$ioeGetErrorType err）
printf“错误字符串：%s\n”$（ioeGetErrorString错误）
printf“错误文件名：%s\n”$（可能是“无”id$ioeGetFileName err）
printf“错误句柄：%s\n”$（可能“无”显示$ioeGetHandle err）
右键->返回（）
--过程参数
main0=do
args显示使用情况
（错误，（标志，FN，[]），用法）->do
房车淋浴器[显示e]使用情况）（const$return（））房车
（错误，错误，用法）->淋浴器错误用法
哪里
desc=“重命名并编录媒体。\n”++
“用法：相册-n\n”
--健康检查
main1标志fns=do
--核对姓名
albName不是一个糟糕的问题，但投票以“离题”结束，因为你的问题可能更适合于不糟糕的问题，但投票以“离题”结束，因为你的问题可能更适合于