Greetings, I am a Haskell novice, but I have written some Haskell functions and would like to call them from C++. The functions perform world coordinate system conversions like the following: data Geocentric = Geocentric { ecefX :: Double, ecefY :: Double, ecefZ :: Double } deriving (Show) data Geodetic = Geodetic { latitude :: Double, longitude :: Double, height :: Double } deriving (Show) geocentricToGeodetic :: Geocentric -> Geodetic geocentricToGeodetic geocentric = Geodetic lat lon height where ... ... lat = ... lon = ... height = ... I would like to call these functions from C++ using FFI, and have figured out how to wrap using FFI to accept and return primitive types: xGeocentricFromGeodetic :: CDouble -> CDouble -> CDouble -> CDouble xGeocentricFromGeodetic lat lon height = realToFrac (ecefX (geodeticToGeocentric (Geodetic (realToFrac lat) (realToFrac lon) (realToFrac height)))) foreign export ccall xGeocentricFromGeodetic :: CDouble -> CDouble -> CDouble -> CDouble Would there be a way to accept a C struct and return a C struct by value, something like this: struct Geocentric { double ecefX; double ecefY; double ecefZ; }; struct Geodetic { double lat; double lon; double height; }; With a method like the following: Geocentric geocentricToGeodetic (const Geodetic & geod); I have investigated the Storable class, but it seems as though this is intended to be used with pointers. In addition, it seems that most of the examples I have found deal with calling C code from Haskell and not vice-versa. Does anyone know if this can be achieved, and if so how? Any help is much appreciated. -- View this message in context: http://haskell.1045720.n5.nabble.com/Possible-to-call-Haskell-function-from-... Sent from the Haskell - FFI mailing list archive at Nabble.com.