RE: C++ integration / DSEL alternative questions

[Moose <moose@...>]

Hello Thijs,

thanks for your response. Let me add some thoughts...

Am 01.04.2014 12:23 schrieb Thijs Schreijer:
> > 4) In a real world use case my users have many scripts in my DSEL 
> > that
> > get executed at a frequency of about 30 Hz or more. Would I create a 
> > Lua
> > state and execute the chunk every time or can I re-use the state 
> > after
> > instantiating it once and excecute many times?
>
> You might have to cleanup some stuff left behind in between calls,
> probably using some sandboxing that can be discarded.
>
> Generally two approaches;
> 1) use a single state. In this case you can use coroutines to create
> different environments (cooperative multithreading)
> 2) use multiple states. Using OS threads (preemptive multithreading)

I think I can rule out 2). The user scripts have to be executed 
sequentially in one thread. Unfortunately, the underlying functions, 
that they all end up calling at some point, are single threaded. As in 
"They all have to be executed from within one specific thread". I cannot 
influence them and have to live with that.

> 1: might require protection from a script locking/hanging the
> environment too long to keep it fluent. Will only utilize a single CPU
> core. Easier to share global state between the different scripts. In a
> multithreaded application synchronization happens before entering the
> Lua state.

So, to me (as a complete Lua newbie) that would mean...

I now do this, straight forward:

	lua_State *L = luaL_newstate();
	luaL_openlibs(L);
	luaopen_MyCppWrapper(L);

	if (luaL_dofile(L, "lunawrapper.lua")) {
		std::cerr << "Lua program returned an error: \n";
		std::cerr << lua_tostring(L, -1);
		std::cerr << std::endl;
		lua_close(L);
              // fail
	}

	lua_gc(L, LUA_GCCOLLECT, 0);  // collected garbage
	lua_close(L);

could you post some hints on how this would be modified to reflect your 
comment? When I would like to execute the file (or memory chunk, as it 
would be in real world) again and again, ideally keeping local 
variables?

Thanks,
Moose