Dear Daniel, > I was glad that you and Nicolas wrote the combinatorial classes notes > last April. However, there wasn't any followup, so I wanted to check > if the situation has changed at all since then. I recently got an > email asking about my covering designs code, in which I had promised a > faster Cython version. I put that on hold until it was clear how a > fast iterator should be added to a class, and I'd like to get back to > it.
Sorry for answering so late... Actually, there wasn't *apparently* any followup concerning CombinatorialClass because it was decided to rename them enumerated set and to make them parents as any sage sets. As any sage parent they must belongs to a category. Therefore things had to wait until categories stuff enters sage, which eventually happen three weeks ago in Sage 4-3. As usual work is never progressing as fast as we hope. Sorry I didn't think about updating the Wiki page. So here is the current status: any set of combinatorial objects should be a parent in either category FiniteEnumeratedSets() or InfiniteEnumeratedSets() or even EnumeratedSet() if the cardinality is unknown. The code for these categories seems to be stable and moreover, there are examples showing how to write such a parent (please see FiniteEnumeratedSets().example() and InfiniteEnumeratedSets().example() from sage) or the respective files sage/categories/examples. You also may want to have a look at the category Sets() associated to the files sets_cat.py for the problem of constructing elements in a parent. On the other hand, concerning the infrastructure a final step is currently being made by allowing categories to work with Cython/extension types (see trac #7921 currently in review). So once it is integrated, there shouldn't be any infrastructure problem. I'm currently working on adapting the combinatorial code to this design. But this is still in progress. The plan is to have trees and binary trees in sage as soon as possible and then to rework permutations, partitions ... Since you didn't ask any precise question, I'm not sure this is what you needed, but I hope this helps. Anyway, please feel free to ask more questions, I'll try to be more reactive. Cheers, Florent PS: I've put Nicolas Thiéry in CC since he is the categories architect.
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