Hi all, I am experimenting with hdirect for the first time, and I can't figure out how to call an haskell function of type String -> IO Int from C. I already can compile and use a function of type Char -> IO Int, so I assume to be using the right command line arguments. I have, in Math.idl ---- module Math { int munlink([in,string]char *s); }; ---- in Math.hs ---- module Math where munlink :: String -> IO Int munlink s = putStr ("Hey!" ++ s ++ "\n") >> return (-1) ---- This is the generated .hs file: module MathProxy where import Prelude (fromEnum, toEnum) import qualified Prelude import qualified Foreign.Ptr (Ptr) import qualified HDirect (unmarshallString) import qualified Math (munlink) munlink_proxy :: Prelude.String -> Prelude.IO Prelude.Int munlink_proxy = wrap_munlink Math.munlink foreign export ccall "munlink" munlink_proxy :: Foreign.Ptr.Ptr Prelude.String -> Prelude.IO Prelude.Int wrap_munlink :: (Prelude.String -> Prelude.IO Prelude.Int) -> Foreign.Ptr.Ptr Prelude.String -> Prelude.IO Prelude.Int wrap_munlink munlink_meth s = do s <- HDirect.unmarshallString s munlink_meth s I get a type error when compiling MathProxy.hs, and the strange thing is that commenting out the type declaration for "munlink_proxy" makes my program work like a charm. Errors from the compiler follow, any help will be highly appreciated. Vincenzo Ciancia ghc -O2 -fglasgow-exts Math.hs -c ihc -fshow-idl-in-comments -s -fhs-to-c --gen-headers -fuse-ints-everywhere -c Math.idl ghc -O2 -c main.c -o main.o ghc -O2 -fglasgow-exts -package hdirect MathProxy.hs -c MathProxy.hs:15: Couldn't match `GHC.Ptr.Ptr GHC.Base.String' against `GHC.Base.String' Expected type: GHC.Base.String -> GHC.IOBase.IO GHC.Base.Int Inferred type: GHC.Ptr.Ptr GHC.Base.String -> GHC.IOBase.IO GHC.Base.Int In the application `wrap_munlink Math.munlink' In the definition of `munlink_proxy': munlink_proxy = wrap_munlink Math.munlink MathProxy.hs:17: Couldn't match `GHC.Base.String' against `GHC.Ptr.Ptr GHC.Base.String' Expected type: GHC.Ptr.Ptr GHC.Base.String -> GHC.IOBase.IO GHC.Base.Int Inferred type: GHC.Base.String -> GHC.IOBase.IO GHC.Base.Int When checking declaration: foreign export ccall "munlink" munlink_proxy :: GHC.Ptr.Ptr GHC.Base.String -> GHC.IOBase.IO GHC.Base.Int