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{-# LANGUAGE ForeignFunctionInterface #-}
import Foreign hiding ( unsafePerformIO )
import Foreign.C
import System.IO.Unsafe
d f x = unsafePerformIO $ do
g <- mkfun f
r <- deriv g x 1
return r
main = do
print $ d (\x -> x * 2) 3
print $ d (\x -> x * d (\y -> x + y) 5) 7
foreign import ccall safe "deriv"
deriv :: FunPtr (CDouble -> CDouble) -> CDouble -> CDouble -> IO CDouble
foreign import ccall safe "wrapper"
mkfun :: (CDouble -> CDouble) -> IO (FunPtr (CDouble -> CDouble))
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