class  Read a  where
    readsPrec        :: Int -> ReadS a
    readList         :: ReadS [a]

-- Minimal complete definition:
-- readsPrec
    readList         = readParen False (\r -> [pr | ("[",s)  <- lex r,
                                                    pr       <- readl s])
                       where readl  s = [([],t)   | ("]",t)  <- lex s] ++
                                        [(x:xs,u) | (x,t)    <- reads s,
                                                    (xs,u)   <- readl' t]
                             readl' s = [([],t)   | ("]",t)  <- lex s] ++
                                        [(x:xs,v) | (",",t)  <- lex s,
                                                    (x,u)    <- reads t,
                                                    (xs,v)   <- readl' u]

instance Read Int where

    readsPrec p         = readSigned readDec

instance Read Integer where

    readsPrec p         = readSigned readDec

instance Read Float where

    readsPrec p         = readFloat

instance Read Double where

    readsPrec p         = readFloat

instance Read () where

   readsPrec p    = readParen False
                            (\r -> [((),t) | ("(",s) <- lex r,
                                             (")",t) <- lex s ] )

instance Read Char where

    readsPrec p      = readParen False
                            (\r -> [(c,t) | ('\'':s,t)<- lex r,
                                            (c,"\'")  <- readLitChar s])

    readList = readParen False (\r -> [(l,t) | ('"':s, t) <- lex r,
                                               (l,_)      <- readl s ])
        where readl ('"':s)      = [("",s)]
              readl ('\\':'&':s) = readl s
              readl s            = [(c:cs,u) | (c ,t) <- readLitChar s,
                                               (cs,u) <- readl t       ]

instance (Read a) => Read [a] where

    readsPrec p      = readList