LineEditor.hs

import Control.Monad
import Control.Applicative
import Control.Exception
import System.IO
import Data.IORef

main = do
  -- args <- getArgs
  -- if length args < 1 then
  --   putStrLn
  lineEdit "read.txt"

prompt :: String -> IO String
prompt msg = do
  putStr msg
  hFlush stdout
  getLine

type FileName = String
type Line  = String
type Text = [Line]
top   = fst
under = snd
type Posit = IORef Int
type EditState = (Posit, Text)


lineEdit fileName = do
  text  <- lines <$> readFile fileName
  state <- newIORef 0
  let edit = (state, text)
  forM_ [0,0..] $ \i -> do
    op <- prompt ":"
    command edit op


command :: EditState -> String -> IO ()
command edit op = --{{{
  case op of
    "p" -> do
      posit <- readIORef (fst edit)
      putStr " "
      putStr $ show (posit + 1)
      putStr "|"
      putStrLn $ (snd edit) !! posit

    "j" -> do
      posit <- readIORef (fst edit)
      if posit < (length $ snd edit) - 1 then
            modifyIORef (fst edit) ((+) 1)
      else  return ()

    "k" -> do
      posit <- readIORef (fst edit)
      if posit > 0 then
            modifyIORef (fst edit) ((-) 1)
      else  return ()

    "q" -> error "強制終了の合図です"

    _   -> putStrLn "コマンドないよ"

--}}}