Read.hs

module Read where

-- import Text.Read

readsData :: (String -> ReadS a) -> Int -> ReadS a
readsData reader d =
    readParen (d > 10) $ \ r -> [res | (kw,s) <- lex r, res <- reader kw s]

readsUnaryWith :: (Int -> ReadS a) -> String -> (a -> t) -> String -> ReadS t
readsUnaryWith rp name cons kw s =
    [(cons x,t) | kw == name, (x,t) <- rp 11 s]

readUnaryWith :: ReadPrec a -> String -> (a -> t) -> String -> ReadPrec t
readUnaryWith = undefined

readsBinaryWith :: (Int -> ReadS a) -> (Int -> ReadS b) ->
    String -> (a -> b -> t) -> String -> ReadS t
readsBinaryWith rp1 rp2 name cons kw s =
    [(cons x y,u) | kw == name, (x,t) <- rp1 11 s, (y,u) <- rp2 11 t]

readBinaryWith :: ReadPrec a -> ReadPrec b ->
    String -> (a -> b -> t) -> String -> ReadPrec t
readBinaryWith = undefined

liftReadsPrec2Either :: (Int -> ReadS a) -> ReadS [a]
                     -> (Int -> ReadS b) -> ReadS [b]
                     -> Int -> ReadS (Either a b)
liftReadsPrec2Either rp1 _ rp2 _ = readsData $
    readsUnaryWith rp1 "Left" Left `mappend`
    readsUnaryWith rp2 "Right" Right