delimited-text-0.3.0: examples/test.hs

import qualified Data.ByteString            as BS
import qualified Data.ByteString.Lazy       as B
import qualified Data.ByteString.Lex.Double as L
import System.Environment                   (getArgs)
import Text.Delimited                       as DT

mainInteract :: [Char] -> IO ()
mainInteract ds = do
    s <- DT.interact id ds `fmap` B.getContents
    case s of
        Right bs -> B.putStr bs
        Left e   -> putStrLn ("Parse failed: " ++ e)

mainPrint :: [Char] -> IO ()
mainPrint ds = do
    s <- DT.decode ds `fmap` B.getContents
    case s of
        Right c -> mapM_ print c
        Left e  -> putStrLn ("Parse failed: " ++ e)

readDouble :: Double -> BS.ByteString -> Double
readDouble d s = case L.readDouble s of
                    Nothing     -> d
                    Just (a, _) -> a

mainPrintNumbers :: [Char] -> IO ()
mainPrintNumbers ds = do
    s <- DT.decode ds `fmap` B.getContents
    case s of
        Right c -> mapM_ (print . map (readDouble 0)) c
        Left e  -> putStrLn ("Parse failed: " ++ e)

main :: IO ()
main = do
    [cmd, ds] <- getArgs
    case cmd of
        "interact" -> mainInteract ds
        "print"    -> mainPrint ds
        "printnum" -> mainPrintNumbers ds
        otherwise  -> putStrLn "Usage: runhaskell test.hs [interact|print|printnum] DELIMITERS < FILE"