Priority Queues?

[Geoff Leyland <geoff_leyland@...>]

Hi,

I'm new here.  I've been using Lua for a while in a discrete-event  
transport simulation, and it's been fantastic.  I was originally  
thinking of using python, and I'm very pleased I looked a little  
further!

The simulation is mostly written in C++, and I started using Lua for  
its configuration files which turned out to be very effective and  
easy, so the next step has been to make the simulation a Lua module,  
which has made the whole thing far more useful and easy to test.

What I'm thinking of next is writing some of the simulation logic in  
Lua.  This seems to mean storing "pointers to Lua objects" (functions  
or callable tables) on the C++ side which should be ok. I think where  
I'd like to get to, or at least try as an exercise, is having  
something like a std::priority_queue containing "pointers to Lua  
functions".

I'm not quite sure how to go about this.  The queue might get longish  
- 100,000's of elements, and I'd like the solution to be moderately  
efficient.

One way I can imagine doing this at the moment is to create a table  
in the registry and store the lua functions at indexes in that table,  
and then store those indexes in the priority_queue.  That way, Lua is  
aware that I'm interested in those objects, and I have a way of  
keeping hold of them.  Popping to top off the priority queue will  
also mean removing an element from the table, which I imagine will be  
a little inefficient.  Possibly more than I'd like, but I'll have to  
see.

The other approach I can think of (which I don't really like) is to  
look at the Lua internals to see if I can hold on to a "lua object"  
other than in a stack or the registry, and if I can make sure the GC  
knows what I'm up to.  Like I said, probably not a good idea.

Does anyone have any advice on how to approach this?  Have any  
experience with storing a largish number of lua variables in a C data  
structure?  Am I missing anything obvious?  Is there anywhere this  
kind of question has already been covered?

Thanks for your time,
Geoff