diff --git a/csrc/MacroPatternMatch.h b/csrc/MacroPatternMatch.h
--- a/csrc/MacroPatternMatch.h
+++ b/csrc/MacroPatternMatch.h
@@ -16,5 +16,28 @@
 #define IS_PAREN(x) CHECK(IS_PAREN_PROBE x)
 #define IS_PAREN_PROBE(...) PROBE(~)
 
+
+
+template<class ToType, class FromType>
+const ToType* to_const(const FromType* x) {
+  return reinterpret_cast<const ToType*>(x);
+}
+
+template<class ToType, class FromType>
+ToType* to_nonconst(FromType* x) {
+  return reinterpret_cast<ToType*>(x);
+}
+
+template<class ToType, class FromType>
+const ToType& to_constref(const FromType& x) {
+  return reinterpret_cast<const ToType&>(x);
+}
+
+template<class ToType, class FromType>
+ToType& to_nonconstref(FromType& x) {
+  return reinterpret_cast<ToType&>(x);
+}
+
+
 #endif // __MACROPATTERNMATCH__ 
 
diff --git a/fficxx-runtime.cabal b/fficxx-runtime.cabal
--- a/fficxx-runtime.cabal
+++ b/fficxx-runtime.cabal
@@ -1,5 +1,5 @@
 Name:		fficxx-runtime
-Version:	0.2.1
+Version:	0.3
 Synopsis:	Runtime for fficxx-generated library
 Description: 	Runtime for fficxx-generated library
 License:        BSD3
@@ -20,10 +20,14 @@
   ghc-options: 	-Wall -funbox-strict-fields -fno-warn-unused-do-bind
   ghc-prof-options: -caf-all -auto-all
   Build-Depends: 
-                   base == 4.*
+                 base == 4.*,
+                 bytestring,
+                 template-haskell
 
   Exposed-Modules: 
                    FFICXX.Runtime.Cast
+                   FFICXX.Runtime.TH
 
+                   
   Include-dirs:    csrc
   Install-includes: MacroPatternMatch.h
diff --git a/lib/FFICXX/Runtime/Cast.hs b/lib/FFICXX/Runtime/Cast.hs
--- a/lib/FFICXX/Runtime/Cast.hs
+++ b/lib/FFICXX/Runtime/Cast.hs
@@ -12,7 +12,7 @@
 -----------------------------------------------------------------------------
 -- |
 -- Module      : FFICXX.Runtime.Cast
--- Copyright   : (c) 2011-2014 Ian-Woo Kim
+-- Copyright   : (c) 2011-2017 Ian-Woo Kim
 --
 -- License     : BSD3
 -- Maintainer  : Ian-Woo Kim <ianwookim@gmail.com>
@@ -23,26 +23,29 @@
 
 module FFICXX.Runtime.Cast where
 
+import Control.Monad         ((>=>))
+import Data.ByteString.Char8 (ByteString,packCString, useAsCString)
 import Data.String
 import Data.Word
 import Foreign.C
 import Foreign.C.String
-import Foreign.Ptr
 import Foreign.ForeignPtr
 import Foreign.Marshal.Array
+import Foreign.Ptr
+import Foreign.Storable
+-- import System.IO.Unsafe
 
-import System.IO.Unsafe
 
 class IsRawType a 
 
 class Castable a b where
-  cast :: a -> b 
-  uncast :: b -> a 
+  cast   :: a -> (b -> IO r) -> IO r 
+  uncast :: b -> (a -> IO r) -> IO r 
 
 class FPtr a where
   type Raw a :: *
-  get_fptr :: a -> ForeignPtr (Raw a) 
-  cast_fptr_to_obj :: ForeignPtr (Raw a) -> a
+  get_fptr :: a -> Ptr (Raw a) 
+  cast_fptr_to_obj :: Ptr (Raw a) -> a
 
 
 class FunPtrWrappable a where
@@ -52,18 +55,9 @@
   fptrWrap :: FunPtrWrapped a -> IO (FunPtr (FunPtrType a)) 
   wrap :: FunPtrHsType a -> FunPtrWrapped a 
 
-class Existable a where
-  data Exist a :: *  
 
-data BottomType
-
-class GADTTypeable a where
-  data GADTType a :: * -> *
-  data EGADTType a :: *
-
 class IsCType a where 
 
-
 instance IsCType CChar
 instance IsCType CInt
 instance IsCType CUInt 
@@ -71,166 +65,205 @@
 instance IsCType CULong 
 instance IsCType CLong
 
-instance IsString CString where
-  fromString str = unsafePerformIO (newCString str)
-
--- cause incoherent instances but cannot avoid it now
-{-
-instance Castable a a where
-  cast = id
-  uncast = id
--}
-
 instance Castable () () where
-  cast = id 
-  uncast = id 
-
+  cast x f = f x
+  uncast x f = f x
 
 instance Castable CDouble CDouble where
-  cast = id
-  uncast = id
-
-
+  cast x f = f x
+  uncast x f = f x
 
 instance Castable CUInt CUInt where
-  cast = id 
-  uncast = id 
+  cast x f = f x 
+  uncast x f = f x  
 
 instance Castable CInt CInt where 
-  cast = id 
-  uncast = id 
+  cast x f = f x 
+  uncast x f = f x 
 
 instance Castable CLong CLong where
-  cast = id
-  uncast = id
+  cast x f = f x 
+  uncast x f = f x
 
 instance Castable CULong CULong where 
-  cast = id 
-  uncast = id 
+  cast x f = f x 
+  uncast x f = f x 
 
  
 instance Castable (Ptr CInt) (Ptr CInt) where 
-  cast = id 
-  uncast = id 
+  cast x f = f x
+  uncast x f = f x 
 
 instance Castable (Ptr CChar) (Ptr CChar) where 
-  cast = id 
-  uncast = id 
+  cast x f = f x 
+  uncast x f = f x 
 
 instance Castable (Ptr CUInt) (Ptr CUInt) where 
-  cast = id 
-  uncast = id 
+  cast x f = f x 
+  uncast x f = f x 
 
 instance Castable (Ptr CULong) (Ptr CULong) where 
-  cast = id 
-  uncast = id 
+  cast x f = f x 
+  uncast x f = f x 
 
 instance Castable (Ptr CLong) (Ptr CLong) where 
-  cast = id 
-  uncast = id 
+  cast x f = f x 
+  uncast x f = f x 
 
 instance Castable (Ptr CDouble) (Ptr CDouble) where 
-  cast = id 
-  uncast = id 
+  cast x f = f x 
+  uncast x f = f x 
 
 instance Castable (Ptr CString) (Ptr CString) where 
-  cast = id 
-  uncast = id 
+  cast x f = f x 
+  uncast x f = f x 
 
 instance Castable (Ptr ()) (Ptr ()) where
-  cast = id
-  uncast = id
+  cast x f = f x
+  uncast x f = f x
 
 
 instance Castable Int CInt where
-  cast = fromIntegral 
-  uncast = fromIntegral
+  cast x f = f (fromIntegral x)
+  uncast x f = f (fromIntegral x)
 
 instance Castable Word CUInt where
-  cast = fromIntegral
-  uncast = fromIntegral
+  cast x f = f (fromIntegral x)
+  uncast x f = f (fromIntegral x)
 
 instance Castable Word8 CChar where
-  cast = fromIntegral 
-  uncast = fromIntegral
+  cast x f = f (fromIntegral x)
+  uncast x f = f (fromIntegral x)
   
 instance Castable Double CDouble where
-  cast = realToFrac
-  uncast = realToFrac 
+  cast x f = f (realToFrac x)
+  uncast x f = f (realToFrac x)
 
 instance Castable [Double] (Ptr CDouble) where
-  cast xs = unsafePerformIO (newArray (map realToFrac xs))
-  uncast _c_xs = undefined 
+  cast xs f = newArray (map realToFrac xs) >>= f 
+  uncast xs f = undefined 
 
 instance Castable [Int] (Ptr CInt) where
-  cast xs = unsafePerformIO (newArray (map fromIntegral xs))
-  uncast _c_xs = undefined 
+  cast xs f = newArray (map fromIntegral xs) >>= f
+  uncast xs f = undefined 
 
+instance Castable ByteString CString where
+  cast x f = useAsCString x f
+  uncast x f = packCString x >>= f 
+
+
+instance Castable [ByteString] (Ptr CString) where
+  cast xs f = do ys <- mapM (\x -> useAsCString x return) xs
+                 withArray ys $ \cptr -> f cptr
+  uncast xs f = undefined 
+
+{- 
 instance Castable String CString where
   cast x = unsafePerformIO (newCString x)
   uncast x = unsafePerformIO (peekCString x) 
 
-instance Castable [String] (Ptr CString) where
-  cast xs = unsafePerformIO (mapM  newCString xs >>= newArray)
-  uncast _c_xs = undefined
 
-
 instance (Castable a a', Castable b b') => Castable (a->b) (a'->b') where
   cast f = cast . f . uncast
   uncast f = uncast . f . cast 
-
+-}
 
 xformnull :: (Castable a ca) => (IO ca) -> IO a
-xformnull f = f >>= return . uncast
+xformnull f = f >>= \ca -> uncast ca return
 
 xform0 :: (Castable a ca, Castable y cy) 
        => (ca -> IO cy) -> a -> IO y
-xform0 f a = f (cast a) >>= return . uncast 
+xform0 f a = cast a $ \ca -> f ca >>= \cy -> uncast cy return
 
 xform1 :: (Castable a ca, Castable x1 cx1, Castable y cy) 
        => (ca -> cx1 -> IO cy) -> a -> x1 -> IO y
-xform1 f a x1 = f (cast a) (cast x1) >>= return . uncast 
+xform1 f a x1 = cast a $ \ca ->
+                  cast x1 $ \cx1 ->
+                    f ca cx1 >>= \cy -> uncast cy return 
 
 xform2 :: (Castable a ca, Castable x1 cx1, Castable x2 cx2, Castable y cy) 
        => (ca -> cx1 -> cx2 -> IO cy) -> a -> x1 -> x2-> IO y
-xform2 f a x1 x2 = f (cast a) (cast x1) (cast x2) >>= return . uncast 
+xform2 f a x1 x2 = cast a $ \ca ->
+                     cast x1 $ \cx1 ->
+                       cast x2 $ \cx2 ->
+                         f ca cx1 cx2 >>= \cy -> uncast cy return
 
 xform3 :: (Castable a ca, Castable x1 cx1, Castable x2 cx2, Castable x3 cx3, Castable y cy) 
        => (ca -> cx1 -> cx2 -> cx3 -> IO cy) -> a -> x1 -> x2 -> x3 -> IO y
-xform3 f a x1 x2 x3 = f (cast a) (cast x1) (cast x2) (cast x3) >>= return . uncast 
+xform3 f a x1 x2 x3 = cast a $ \ca ->
+                        cast x1 $ \cx1 ->
+                          cast x2 $ \cx2 ->
+                            cast x3 $ \cx3 ->
+                              f ca cx1 cx2 cx3 >>= \cy -> uncast cy return 
 
 xform4 :: (Castable a ca, Castable x1 cx1, Castable x2 cx2, Castable x3 cx3, Castable x4 cx4, Castable y cy) 
        => (ca -> cx1 -> cx2 -> cx3 -> cx4 -> IO cy) -> a -> x1 -> x2 -> x3 -> x4 -> IO y
-xform4 f a x1 x2 x3 x4 = f (cast a) (cast x1) (cast x2) (cast x3) (cast x4) >>= return . uncast 
+xform4 f a x1 x2 x3 x4 =
+  cast a $ \ca ->
+    cast x1 $ \cx1 ->
+      cast x2 $ \cx2 ->
+        cast x3 $ \cx3 ->
+          cast x4 $ \cx4 -> 
+            f ca cx1 cx2 cx3 cx4 >>= \cy -> uncast cy return 
 
+
 xform5 :: (Castable a ca, Castable x1 cx1, Castable x2 cx2, Castable x3 cx3, Castable x4 cx4,
            Castable x5 cx5, Castable y cy) 
        => (ca -> cx1 -> cx2 -> cx3 -> cx4 -> cx5 -> IO cy) -> a -> x1 -> x2 -> x3 -> x4 -> x5 -> IO y
-xform5 f a x1 x2 x3 x4 x5 = f (cast a) (cast x1) (cast x2) (cast x3) (cast x4) (cast x5) >>= return . uncast 
+xform5 f a x1 x2 x3 x4 x5 =
+  cast a $ \ca ->
+    cast x1 $ \cx1 ->
+      cast x2 $ \cx2 ->
+        cast x3 $ \cx3 ->
+          cast x4 $ \cx4 ->
+            cast x5 $ \cx5 -> 
+              f ca cx1 cx2 cx3 cx4 cx5 >>= \cy -> uncast cy return 
 
 xform6 :: (Castable a ca, Castable x1 cx1, Castable x2 cx2, Castable x3 cx3, Castable x4 cx4,
            Castable x5 cx5, Castable x6 cx6, Castable y cy) 
        => (ca -> cx1 -> cx2 -> cx3 -> cx4 -> cx5 -> cx6 -> IO cy) 
           -> a -> x1 -> x2 -> x3 -> x4 -> x5 -> x6 -> IO y
 xform6 f a x1 x2 x3 x4 x5 x6 = 
-  f (cast a) (cast x1) (cast x2) (cast x3) (cast x4) (cast x5) (cast x6) 
-  >>= return . uncast 
-
+  cast a $ \ca ->
+    cast x1 $ \cx1 ->
+      cast x2 $ \cx2 ->
+        cast x3 $ \cx3 ->
+          cast x4 $ \cx4 ->
+            cast x5 $ \cx5 ->
+              cast x6 $ \cx6 -> 
+                f ca cx1 cx2 cx3 cx4 cx5 cx6 >>= \cy -> uncast cy return 
+  
 xform7 :: (Castable a ca, Castable x1 cx1, Castable x2 cx2, Castable x3 cx3, Castable x4 cx4,
            Castable x5 cx5, Castable x6 cx6, Castable x7 cx7, Castable y cy) 
        => (ca -> cx1 -> cx2 -> cx3 -> cx4 -> cx5 -> cx6 -> cx7 -> IO cy) 
           -> a -> x1 -> x2 -> x3 -> x4 -> x5 -> x6 -> x7 -> IO y
 xform7 f a x1 x2 x3 x4 x5 x6 x7 = 
-  f (cast a) (cast x1) (cast x2) (cast x3) (cast x4) (cast x5) (cast x6) (cast x7)
-  >>= return . uncast 
+  cast a $ \ca ->
+    cast x1 $ \cx1 ->
+      cast x2 $ \cx2 ->
+        cast x3 $ \cx3 ->
+          cast x4 $ \cx4 ->
+            cast x5 $ \cx5 ->
+              cast x6 $ \cx6 ->
+                cast x7 $ \cx7 ->  
+                  f ca cx1 cx2 cx3 cx4 cx5 cx6 cx7 >>= \cy -> uncast cy return 
 
+
 xform8 :: (Castable a ca, Castable x1 cx1, Castable x2 cx2, Castable x3 cx3, Castable x4 cx4,
            Castable x5 cx5, Castable x6 cx6, Castable x7 cx7, Castable x8 cx8, Castable y cy) 
        => (ca -> cx1 -> cx2 -> cx3 -> cx4 -> cx5 -> cx6 -> cx7 -> cx8 -> IO cy) 
           -> a -> x1 -> x2 -> x3 -> x4 -> x5 -> x6 -> x7 -> x8 -> IO y
-xform8 f a x1 x2 x3 x4 x5 x6 x7 x8 = 
-  f (cast a) (cast x1) (cast x2) (cast x3) (cast x4) (cast x5) (cast x6) (cast x7) (cast x8)
-  >>= return . uncast 
+xform8 f a x1 x2 x3 x4 x5 x6 x7 x8 =
+  cast a $ \ca ->
+    cast x1 $ \cx1 ->
+      cast x2 $ \cx2 ->
+        cast x3 $ \cx3 ->
+          cast x4 $ \cx4 ->
+            cast x5 $ \cx5 ->
+              cast x6 $ \cx6 ->
+                cast x7 $ \cx7 ->
+                  cast x8 $ \cx8 ->  
+                    f ca cx1 cx2 cx3 cx4 cx5 cx6 cx7 cx8 >>= \cy -> uncast cy return 
 
 xform9 :: (Castable a ca, Castable x1 cx1, Castable x2 cx2, Castable x3 cx3, Castable x4 cx4,
            Castable x5 cx5, Castable x6 cx6, Castable x7 cx7, Castable x8 cx8, Castable x9 cx9, 
@@ -238,8 +271,17 @@
        => (ca -> cx1 -> cx2 -> cx3 -> cx4 -> cx5 -> cx6 -> cx7 -> cx8 -> cx9 -> IO cy) 
           -> a -> x1 -> x2 -> x3 -> x4 -> x5 -> x6 -> x7 -> x8 -> x9 -> IO y
 xform9 f a x1 x2 x3 x4 x5 x6 x7 x8 x9 = 
-  f (cast a) (cast x1) (cast x2) (cast x3) (cast x4) (cast x5) (cast x6) (cast x7) (cast x8) (cast x9)
-  >>= return . uncast 
+  cast a $ \ca ->
+    cast x1 $ \cx1 ->
+      cast x2 $ \cx2 ->
+        cast x3 $ \cx3 ->
+          cast x4 $ \cx4 ->
+            cast x5 $ \cx5 ->
+              cast x6 $ \cx6 ->
+                cast x7 $ \cx7 ->
+                  cast x8 $ \cx8 ->
+                    cast x9 $ \cx9 ->  
+                      f ca cx1 cx2 cx3 cx4 cx5 cx6 cx7 cx8 cx9 >>= \cy -> uncast cy return 
 
 xform10 :: (Castable a ca, Castable x1 cx1, Castable x2 cx2, Castable x3 cx3, Castable x4 cx4,
             Castable x5 cx5, Castable x6 cx6, Castable x7 cx7, Castable x8 cx8, Castable x9 cx9,  
@@ -247,13 +289,36 @@
        => (ca -> cx1 -> cx2 -> cx3 -> cx4 -> cx5 -> cx6 -> cx7 -> cx8 -> cx9 -> cx10 -> IO cy) 
           -> a -> x1 -> x2 -> x3 -> x4 -> x5 -> x6 -> x7 -> x8 -> x9 -> x10 -> IO y
 xform10 f a x1 x2 x3 x4 x5 x6 x7 x8 x9 x10 = 
-  f (cast a) (cast x1) (cast x2) (cast x3) (cast x4) (cast x5) (cast x6) (cast x7) (cast x8) (cast x9) (cast x10) >>= return . uncast 
+  cast a $ \ca ->
+    cast x1 $ \cx1 ->
+      cast x2 $ \cx2 ->
+        cast x3 $ \cx3 ->
+          cast x4 $ \cx4 ->
+            cast x5 $ \cx5 ->
+              cast x6 $ \cx6 ->
+                cast x7 $ \cx7 ->
+                  cast x8 $ \cx8 ->
+                    cast x9 $ \cx9 ->
+                      cast x10 $ \cx10 ->  
+                        f ca cx1 cx2 cx3 cx4 cx5 cx6 cx7 cx8 cx9 cx10 >>= \cy -> uncast cy return 
 
 xform11 :: (Castable a ca, Castable x1 cx1, Castable x2 cx2, Castable x3 cx3, Castable x4 cx4,
             Castable x5 cx5, Castable x6 cx6, Castable x7 cx7, Castable x8 cx8, Castable x9 cx9,  
             Castable x10 cx10, Castable x11 cx11, Castable y cy) 
        => (ca -> cx1 -> cx2 -> cx3 -> cx4 -> cx5 -> cx6 -> cx7 -> cx8 -> cx9 -> cx10 -> cx11 -> IO cy) 
           -> a -> x1 -> x2 -> x3 -> x4 -> x5 -> x6 -> x7 -> x8 -> x9 -> x10 -> x11 -> IO y
-xform11 f a x1 x2 x3 x4 x5 x6 x7 x8 x9 x10 x11 = 
-  f (cast a) (cast x1) (cast x2) (cast x3) (cast x4) (cast x5) (cast x6) (cast x7) (cast x8) (cast x9) (cast x10) (cast x11)  >>= return . uncast 
+xform11 f a x1 x2 x3 x4 x5 x6 x7 x8 x9 x10 x11 =
+  cast a $ \ca ->
+    cast x1 $ \cx1 ->
+      cast x2 $ \cx2 ->
+        cast x3 $ \cx3 ->
+          cast x4 $ \cx4 ->
+            cast x5 $ \cx5 ->
+              cast x6 $ \cx6 ->
+                cast x7 $ \cx7 ->
+                  cast x8 $ \cx8 ->
+                    cast x9 $ \cx9 ->
+                      cast x10 $ \cx10 ->
+                        cast x11 $ \cx11 ->  
+                         f ca cx1 cx2 cx3 cx4 cx5 cx6 cx7 cx8 cx9 cx10 cx11 >>= \cy -> uncast cy return 
 
diff --git a/lib/FFICXX/Runtime/TH.hs b/lib/FFICXX/Runtime/TH.hs
new file mode 100644
--- /dev/null
+++ b/lib/FFICXX/Runtime/TH.hs
@@ -0,0 +1,55 @@
+{-# LANGUAGE TemplateHaskell #-}
+
+-----------------------------------------------------------------------------
+-- |
+-- Module      : FFICXX.Runtime.TH
+-- Copyright   : (c) 2011-2016 Ian-Woo Kim
+--
+-- License     : BSD3
+-- Maintainer  : Ian-Woo Kim <ianwookim@gmail.com>
+-- Stability   : experimental
+-- Portability : GHC
+--
+-----------------------------------------------------------------------------
+
+module FFICXX.Runtime.TH where
+
+import Data.Monoid                ( (<>) )
+import Language.Haskell.TH
+import Language.Haskell.TH.Syntax
+
+-------
+
+con :: String -> Type
+con = ConT . mkNameS
+
+mkInstance :: Cxt -> Type -> [Dec] -> Dec
+mkInstance = InstanceD Nothing
+
+mkTFunc :: (Name, String, String -> String, Name -> Q Type) -> ExpQ
+mkTFunc (nty, ncty, nf, tyf)
+  = do let fn = nf ncty
+       let fn' = "c_" <> fn
+       n <- newName fn'
+       d <- forImpD CCall unsafe fn n (tyf nty)
+       addTopDecls [d]
+       [| $( varE n ) |]
+
+
+
+mkMember :: String -> (Name -> String -> Q Exp) -> Name -> String -> Q Dec
+mkMember fname f n ctyp = do
+  let x = mkNameS "x"
+  e <- f n ctyp
+  return $
+    FunD (mkNameS fname) [ Clause [VarP x] (NormalB (AppE e (VarE x))) [] ]
+
+mkNew :: String -> (Name -> String -> Q Exp) -> Name -> String -> Q Dec
+mkNew fname f n ctyp = do
+  e <- f n ctyp
+  return $
+    FunD (mkNameS fname)
+      [ Clause [] (NormalB e) [] ]
+
+mkDelete :: String -> (Name -> String -> Q Exp) -> Name -> String -> Q Dec
+mkDelete = mkMember