int LuaThing::addAlias(lua_State *L) { int n = lua_gettop(L); if (2 != n) { return luaL_error(L, "takes one string argument"); } Thing *t = checkThing(L, -2); if (0 == t) { return luaL_error(L, "not a Thing!"); } string alias = luaL_checkstring(L, -1); t->addAlias(alias); return 1; }