逆順ナンバリング ref: http://qiita.com/items/e57d03a92ad6d0ffe0ac

file0.txt

テキストファイルを指定するとそのファイル名と，行番号をふった内容を印字するプログラムを作成せよ．
ただし，ファイルは複数指定できるものとし，行番号は（そのファイルでの）残りの行数を表す数である．
（対象ファイルがn行からなる場合，n-1から0までの番号が降順にふられる．）

file1.txt

module Main where

import System.Environment (getArgs)

main :: IO ()
main = mapM_ revNumFileProc =<< getArgs

revNumFileProc :: FilePath -> IO ()
revNumFileProc = undefined

file10.txt

numberings = map (uncurry (printf "%06d: %s")) . zip [0..]

file11.txt

map (uncurry f) . zip xs = zipWith f xs

file12.txt

numberings = zipWith (printf "%06d: %s") [0..]

file13.txt

module Main where

import System.Environment (getArgs)

main :: IO ()
main = mapM_ revNumFileProc =<< getArgs

revNumFileProc :: FilePath -> IO ()
revNumFileProc = uncurry (>>) . pair (putFileName, revNumFile)

putFileName :: FilePath -> IO ()
putFileName = putStrLn

revNumFile    :: FilePath -> IO ()
revNumFile fn =  putStr . unlines . revnumberings . lines =<< readFile fn

revnumberings :: [String] -> [String]
revnumberings = reverse . numberings . reverse

numberings :: [String] -> [String]
numberings = zipWith numbering [0..]

numbering :: Int -> String -> String
numbering = printf "%06d: %s"

-- Utility

pair :: (a -> b, a -> c) -> a -> (b, c)
pair (f,g) x = (f x, g x)

file14.txt

numbering :: Int -> String -> (Int,String)
numbering i s = (i+1,printf "%06d: %s" i s)

file15.txt

numberings = snd . mapAccumL numbering 0 

file16.txt

revnumberings = reverse . numberings . reverse

file17.txt

        行       :      行     ...    :      行       :     []
        ↓             ↓                    ↓             ↓
 n ← number ← n-1 ← number ←...← 1 ← number ← 0 ← number ← 0
        ↓             ↓                    ↓             ↓  
     番号++行    :   番号++行         :   番号++行   :      []

file18.txt

revnumberings = snd . mapAccumR numbering 0

file2.txt

pair :: (a -> b, a -> c) -> a -> (b,c)
pair (f,g) x = (f x, g x)

file3.txt

revNumFileProc :: FilePath -> IO ()
revNumFileProc = uncurry (>>) . pair (putFileName, revNumFile)

file4.txt

module Main where

import System.Environment (getArgs)

main :: IO ()
main = mapM_ revNumFileProc =<< getArgs

revNumFileProc :: FilePath -> IO ()
revNumFileProc = uncurry (>>) . pair (putFileName, revNumFile)

putFileName :: FilePath -> IO ()
putFileName = undefined

revNumFile :: FilePath -> IO ()
revNumFile = undefined

-- Utility

pair :: (a -> b, a -> c) -> a -> (b, c)
pair (f,g) x = (f x, g x)

file5.txt

revNumFile :: FilePath -> IO ()
revNumFile fn =  putStr . unlines . revnumbering . lines =<< readFile fn

file6.txt

module Main where

import System.Environment (getArgs)

main :: IO ()
main = mapM_ revNumFileProc =<< getArgs

revNumFileProc :: FilePath -> IO ()
revNumFileProc = uncurry (>>) . pair (putFileName, revNumFile)

putFileName :: FilePath -> IO ()
putFileName = putStrLn

revNumFile    ::  FilePath -> IO ()
revNumFile fn =   putStr . unlines . revnumberings . lines =<< readFile fn

revnumberings :: [String] -> [String]
revnumberings = undefined

-- Utility

pair :: (a -> b, a -> c) -> a -> (b, c)
pair (f,g) x = (f x, g x)

file7.txt

revnumberings :: [String] -> [String]
revnumberings = reverse . numberings . reverse

file8.txt

numberings :: [String] -> [String]
numberings = map numbering . zip [0..]

numbering :: (Int,String) -> String
numbering (i,s) = printf "%06d: %s" i s

file9.txt

numbering = uncurry (printf "%06d: %s")

revnumbering.hs

module Main where

import Data.List (mapAccumR)
import System.Environment (getArgs)
import Text.Printf (printf)

main :: IO ()
main = mapM_ revNumFileProc =<< getArgs

revNumFileProc :: FilePath -> IO ()
revNumFileProc = uncurry (>>) . pair (putFileName, revNumFile)

putFileName :: FilePath -> IO ()
putFileName = putStrLn

revNumFile    :: FilePath -> IO ()
revNumFile fn =  putStr . unlines . revnumberings . lines =<< readFile fn

revnumberings :: [String] -> [String]
revnumberings = snd . mapAccumR numbering 0

numbering :: Int -> String -> (Int,String)
numbering i s = (i+1, printf "%06d: %s" i s)

-- Utility

pair :: (a -> b, a -> c) -> a -> (b, c)
pair (f,g) x = (f x, g x)