Possible to call Haskell function from C and return a struct by value?
scott.frame at gmail.com
Wed Mar 30 06:41:08 CEST 2011
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
data Geocentric = Geocentric
ecefX :: Double,
ecefY :: Double,
ecefZ :: Double
data Geodetic = Geodetic
latitude :: Double,
longitude :: Double,
height :: Double
geocentricToGeodetic :: Geocentric -> Geodetic
geocentricToGeodetic geocentric = Geodetic lat lon height
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)
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:
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
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