'function i register
Public Function Print(ByVal lua_state As IntPtr) As Integer
    Console.WriteLine(clua.GetString(-1))
End Function

'how i register a function
Friend Sub register(ByVal lua_state As IntPtr, ByVal name As String, ByVal func As LuaCFunction)
    Dim top As Integer = lua_gettop(lua_state) 'upvalues
    lua_pushcclosure(lua_state, func, top)
    lua_setfield(lua_state, LUA_GLOBALSINDEX, name)
End Sub