Hi,

> P.S. Just for information, here is the specification of the Bitset
> (BSET) data type I use.  It turned out to be useful, convenient, and
> complete for its purpose (which is of course only one of the
> potential applications of bit-twiddling):

You may be interested in the following portable library which provides
a compact representation of integer sets and an API matching the full
SRFI-14 (one of the primary uses of this was to represent character
sets).

  http://www.call-with-current-continuation.org/eggs/iset.html

Although it's implemented using bit operations, what you describe is a
set of integers, so in the above library they are called isets.

--
Alex