Add Haskell FFI example

experiments/ffi/Makefile

@@ -0,0 +1,12 @@
+.PHONY: all
+all: c_functions.o
+
+CC=clang
+
+c_functions.o:
+	$(CC) -c c-functions.c
+
+
+.PHONY: clean
+clean:
+	rm -f c-functions.o

experiments/ffi/c-functions.c

@@ -0,0 +1,7 @@
+#include "c-functions.h"
+
+
+int c_add(int i, int j)
+{
+  return i + j;
+}

experiments/ffi/c-functions.h

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+#ifndef C_FUNCTIONS_H
+#define C_FUNCTIONS_H
+
+int c_add(int i, int j);
+
+#endif

experiments/ffi/hs-functions.hs

@@ -0,0 +1,11 @@
+{-# LANGUAGE ForeignFunctionInterface #-}
+
+module FfiExperiment where
+
+import Foreign.C
+
+
+foreign import ccall "c-functions.h c_add" c_add :: CInt -> CInt -> CInt
+
+add :: Int -> Int -> Int
+add x y = fromIntegral $ c_add (fromIntegral x) (fromIntegral y)