{-# LANGUAGE EmptyDataDecls, FlexibleInstances,
  MultiParamTypeClasses, TypeFamilies #-}
module STD.Pair.Template where
import Foreign.C.Types
import Foreign.Ptr
import FFICXX.Runtime.Cast

data RawPair tp1 tp2

newtype Pair tp1 tp2 = Pair (Ptr (RawPair tp1 tp2))

class () => IPair tp1 tp2 where
        newPair :: tp1 -> tp2 -> IO (Pair tp1 tp2)
        
        deletePair :: Pair tp1 tp2 -> IO ()
        
        first_get :: Pair tp1 tp2 -> IO tp1
        
        first_set :: Pair tp1 tp2 -> tp1 -> IO ()
        
        second_get :: Pair tp1 tp2 -> IO tp2
        
        second_set :: Pair tp1 tp2 -> tp2 -> IO ()

instance () => FPtr (Pair tp1 tp2) where
        type Raw (Pair tp1 tp2) = RawPair tp1 tp2
        get_fptr (Pair ptr) = ptr
        cast_fptr_to_obj = Pair

instance () => Castable (Pair tp1 tp2) (Ptr (RawPair tp1 tp2))
         where
        cast x f = f (castPtr (get_fptr x))
        uncast x f = f (cast_fptr_to_obj (castPtr x))