http://en.wikibooks.org/wiki/Write_Yourself_a_Scheme_in_48_Hours/Parsing attempt

Error

GHCi, version 6.8.2: http://www.haskell.org/ghc/  :? for help

shell returned 1

:!ghc -o hello --make main.hs
[1 of 1] Compiling Main             ( main.hs, main.o )

main.hs:31:4: parse error on input `x'

shell returned 1

gistfile1.hs

module Main where
import System.Environment
import Text.ParserCombinators.Parsec hiding (spaces)


main :: IO()
main = do 
    args <- getArgs
    putStrLn (readExpr (args !! 0))

symbol :: Parser Char
symbol = oneOf "!#$%&|*+-/:<=>?@^_~" 

data LispVal = Atom String 
    | List [LispVal] 
    | DottedList [LispVal] LispVal 
    | Number Integer 
    | String String 
    | Bool Bool 

readExpr :: String -> String
readExpr input = case parse (space >> symbol) "lisp" input of
    Left err -> "no match: " ++ show err
    Right val -> "Found Val"

spaces :: Parser ()
spaces = skipMany1 space

parseString :: Parser LispVal 
parseString = do char '"' 
    x <- many (noneOf "\"") 
    char '"' 
    return x