[PPL-devel] Re: A question on powerset operations

[Roberto Bagnara]

Hosung Song wrote:
> Thank you very much. Encouraged by your prompt feedback, I decided to 
> try to implement my own C interface for those polyhedra powerset 
> operations. All I need is just three operations: creation of an empty 
> powerset, add a disjunct, and finally check if a polyhedron is contained 
> (geometrically covered) by a powerset. (Maybe I would need more later.) 
> Since my C++ knowledge is very shallow, it took quite a long time to 
> figure out how (after all, most answers I found from the ppl_c.cc), 
> especially how to deal with the compile errors due to differences in 
> Polyhedron and NNC_Polyhedron. Polyhedra_PowerSet is defined as a 
> template class, and I just don't know much how to deal with one 
> effectively. I tried various different ad hoc trials, and it turns out 
> that there's a simple casting operation, which I found in another 
> portion of ppl_c.cc. Anyway, I know my implementation may be too 
> specific for my purpose, but I'd like you to look over it and give me 
> some confirmation.

Dear Hosung,

first of all, please accept my apologies for the delay with which I am
answering.  The last couple of weeks have been tough ones, and things
do not seem to get any better.

I have looked at your code and it seems correct.

> It seems that the integration works well for my 
> project right now, but who knows if my implementation is just completely 
> bogus. I'm attaching the diffs for interfaces/C/ppl_c.cc and 
> interfaces/C/ppl_c.h.in. All diffs are just additions to the original 
> ppl_c.cc and ppl_c.h.in. I know they are really tiny, but it took me a 
> novice C++ user quite a few hours. Any of your comments would be greatly 
> appreciated.

Your code looks OK.  If it runs (I assume you have tested it) and it does
what you want it to do, then you are all set.

> I'd be happy if you somehow incorporate this kind of C 
> interface in the new release. In fact, I thought of coding this as a 
> separate source file, maybe under my project directory, because I didn't 
> want to modify the PPL distribution. However, my lack of knowledge on 
> how to compile it and manage as a library prohibited that approach. If 
> you could give me a pointer on general methods of making C interface for 
> library written in C++, I would certainly try that.

This is an issue we are thinking about.  I will try to summarize
where we are in the next messages.
All the best, and sorry again for the delay,

     Roberto

-- 
Prof. Roberto Bagnara
Computer Science Group
Department of Mathematics, University of Parma, Italy
http://www.cs.unipr.it/~bagnara/
mailto:bagnara at cs.unipr.it