push a working LibArith example to the repo

examples/lualib_in_haskell/LibArith.hs

@@ -0,0 +1,19 @@
+{-# LANGUAGE ScopedTypeVariables #-}
+
+module LibArith where
+
+import Data.Maybe
+import Foreign.C.Types
+
+import Scripting.Lua
+import Scripting.Lua.Raw
+
+foreign export ccall
+  add :: LuaState -> IO CInt
+
+add :: LuaState -> IO CInt
+add l = do
+  i1 :: LuaNumber <- fromJust `fmap` peek l 1
+  i2 :: LuaNumber <- fromJust `fmap` peek l 2
+  push l (i1 + i2 :: LuaNumber)
+  return 1

examples/lualib_in_haskell/Makefile

@@ -0,0 +1,13 @@
+ALL: libarith.so lualibhelper.so
+
+libarith.so: LibArith.hs
+	ghc $^ -o $@ -shared -fPIC -dynamic -lHSrts-ghc7.10.1
+
+lualibhelper.so: libarith.so libarithhelper.c
+	ghc libarithhelper.c -no-hs-main -o $@ -shared -fPIC -dynamic -lHSrts-ghc7.10.1 -L. -larith -I../../lua-5.1.5
+
+clean:
+	rm -f *.hi
+	rm -f *.o
+	rm -f *.so
+	rm -f *_stub.h

examples/lualib_in_haskell/libarithhelper.c

@@ -0,0 +1,25 @@
+#include "LibArith_stub.h"
+#include "lua.h"
+
+int hs_init_lua(lua_State *L)
+{
+  hs_init(NULL, NULL);
+  return 0;
+}
+
+int hs_exit_lua(lua_State *L)
+{
+  hs_exit();
+  return 0;
+}
+
+int luaopen_lualibhelper(lua_State *L)
+{
+  lua_pushcfunction(L, add);
+  lua_setglobal(L, "add_in_haskell");
+  lua_pushcfunction(L, hs_init_lua);
+  lua_setglobal(L, "hs_init");
+  lua_pushcfunction(L, hs_exit_lua);
+  lua_setglobal(L, "hs_exit");
+  return 0;
+}

examples/lualib_in_haskell/main.lua

@@ -0,0 +1,6 @@
+require "lualibhelper"
+
+hs_init()
+print(add_in_haskell(1, 2))
+print(add_in_haskell(-10, 20))
+hs_exit()