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My use of Haskell Text.JSON is considered ugly?

What I'm trying to do is really simple .

I would like to convert the following JSON that I get from an external source:

[{"symbol": "sym1", "description": "desc1"}
 {"symbol": "sym1", "description": "desc1"}]

in the following types:

data Symbols = Symbols [Symbol]
type Symbol  = (String, String)

I ended up writing the following code using Text.JSON:

instance JSON Symbols where
  readJSON (JSArray arr) = either Error (Ok . Symbols) $ resultToEither (f arr [])
    where
      f ((JSObject obj):vs) acc = either Error (\x -> f vs (x:acc)) $ resultToEither (g (fromJSObject obj) [])
      f [] acc                  = Ok $ reverse acc
      f _ acc                   = Error "Invalid symbol/description list"

      g ((name, JSString val):vs) acc = g vs ((name, fromJSString val):acc)
      g [] acc                        = valg acc
      g _ acc                         = Error "Invalid symbol/description record"

      valg xs = case (sym, desc) of
        (Nothing, _)            -> Error "Record is missing symbol"
        (_, Nothing)            -> Error "Record is missing description"
        (Just sym', Just desc') -> Ok (sym', desc')
        where
          sym = lookup "symbol" xs
          desc = lookup "description" xs

  showJSON (Symbols syms) = JSArray $ map f syms
    where
      f (sym, desc) = JSObject $ toJSObject [("symbol", JSString $ toJSString sym),
                                             ("description", JSString $ toJSString desc)]

It reached the most inelegant Haskell I have ever written. readJSONjust doesn't look right. Sure, showJSONmuch shorter, but what about this tag JSString $ toJSStringand JSObject $ toJSObjectwhich I have to bring here? And resultToEither?

Am I using Text.JSON incorrectly? Is there a better way?

, . readJSON . JSON , .

instance JSON Symbols where
  readJSON o = fmap Symbols (readJSON o >>= mapM f)
    where
      f (JSObject o) = (,) <$> valFromObj "symbol" o <*> valFromObj "description" o
      f _            = Error "Unable to read object"
+5
2

- ? "Haskell Text.JSON ..." - " Text.JSON ..."

- ? - mapM.

:

instance JSON Symbols where
  readJSON (JSArray arr) = fmap Symbols (f arr)
  f = mapM (\(JSObject obj) -> g . fromJSObject $ obj)
  g = valg . map (\(name, JSString val) -> (name, fromJSString val))

  valg xs = case (sym, desc) of
    (Nothing, _)            -> Error "Record is missing symbol"
    (_, Nothing)            -> Error "Record is missing description"
    (Just sym', Just desc') -> Ok (sym', desc')
    where 
      sym = lookup "symbol" xs
      desc = lookup "description" xs
+6

. , .

instance JSON Symbols where
  readJSON o = fmap Symbols (readJSON o >>= mapM f)
    where
      f (JSObject o) = let l = fromJSObject o
                       in do s <- jslookup "symbol" l
                             d <- jslookup "description" l
                             return (s,d)
      f _ = Error "Expected an Object"
      jslookup k l = maybe (Error $ "missing key : "++k) readJSON (lookup k l)
+2

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