This is the design I like: a u32 vector such that each even element is the starting code point of an interval and each odd element is the ending code point + 1 of an interval, where the intervals are in order. A binary search determines whether an element is in or out of the set. Intersection is merge, and complement is "prepend #x00000 to the set and remove the last element, unless the set already begins with #x00000, in which case remove it and append #x200000".

See https://github.com/scheme-requests-for-implementation/srfi-14/blob/master/contrib/unicode-2019/CharsetDefs.html for how to make standard character set definitions that conform to Unicode rather than Java 1.0.

On Wed, May 17, 2023 at 1:34 PM Bradley Lucier <lucier@math.purdue.edu> wrote:

Marc:

I'd like to have an implementation of SRFI 14 (character sets) that
works with the entire unicode character set rather than just the
256-character Latin1 subset

I think one needs a data structure that allows compact encoding of
relatively large (about $2^{21}$ elements) sets of positive integers
that have lots of contiguous subsets.

At any rate, I thought you may have solved this problem in
gambit/lib/gambit/char/char#.scm, but for the life of me I can't figure
out what you're doing there.

Can your data sets for encoding Unicode properties be used for an
efficient SRFI 14 implementation?

Brad

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