FFI Help

[Malcolm Wallace]

> > > foreign import ccall "math.h signgam" signgamC :: IO Int
> 
> signgam is an "int" variable, but this assumes that it is a function
> of type "int signgam(void)".
> 
> Write a C wrapper "int get_signgam(void) { return signgam; }" and
> import that.

Or alternatively, foreign import the address of the int and read it
directly with 'peek'.

    import Foreign
    ...
    foreign import ccall "math.h &signgam" signgamC :: Ptr Int32
    ...
    gammaIO :: Double -> IO Double
    gammaIO x = do lg <- lgammaC x
                   s  <- peek signgamC
                   return $ fromIntegral s * exp lg


Regards,
  Malcolm