Consider the following code which registers a free function (plus()) as a member function of class A:

	#include <string>
	#include <iostream>
	#include <luabind/luabind.hpp>
	struct A
	{
	A(int val): a(val) {}
	int a;
	};
	int plus(A* o, int v)
	{
	return o->a + v;
	}
	extern "C" int init(lua_State* L)
	{
	using namespace luabind;
	open(L);
	module(L)
	[
	class_<A>("A")
	.def(constructor<int>())
	.def("plus", &plus)
	];
	return 0;
	}

view raw register_free.cpp hosted with ❤ by GitHub

When run:

kuyu@ub16:~/dkuyu/Dropbox/practice/lua/luabind/register_free$ cat test.lua
package.loadlib('./register_free.so', 'init')()
x = A(3)
print(x:plus(5))
kuyu@ub16:~/dkuyu/Dropbox/practice/lua/luabind/register_free$ cat commands.bash
#!/bin/bash
g++ register_free.cpp -I/usr/include/lua5.2/ -c -fPIC
g++ -shared -Wl,--whole-archive -o register_free.so register_free.o -lluabind -Wl,--no-whole-archive
lua test.lua
kuyu@ub16:~/dkuyu/Dropbox/practice/lua/luabind/register_free$ ./commands.bash
8
kuyu@ub16:~/dkuyu/Dropbox/practice/lua/luabind/register_free$