I've just pushed another SRFI version and implementation
to <http://www.ccil.org/~cowan/srfi-113.html> and
<http://www.ccil.org/~cowan/sets.tar.gz>.  I assume they'll be up on
the SRFI site soon.

Here are the changes:

1) Flushed alist->bag! because of complications with handling conflicts
between the bag and multiple occurrences in the alist.

2) Added bag-sum and bag-product and corresponding ! versions.

3) Renamed set/bag-comparator to set/bag-element-comparator.

4) Added comparator objects set/bag-comparator for comparing sets/bags.
Having them allows sets of sets, bags of bags, etc.

I decided to save cartesian products and power sets for a possible
future combinatorics SRFI, as Alex Shinn suggested.  The only Scheme I
could find that has them is Gauche, which puts them with combinations
and permutations.

I really hope not to have any more substantive changes now, so that we
can finalize the SRFI in a week or so.  Of course, editorial changes or
epic fails should be reported.

--
John Cowan          http://www.ccil.org/~cowan        xxxxxx@ccil.org
De plichten van een docent zijn divers, die van het gehoor ook.
      --Edsger Dijkstra