properset

Allows to handles sets, including complex ones, -- properly.

`properset` allows to properly handle sets that contain objects, tables, or other sets and can handle cyclic sets, that is, sets that reference themselves or that contain sets that reference themselves. Moreover, it provides functions for basic set arithmetics, sports a sane interface, and is well-documented.

However, `properset` is *not* quite production-ready. The interface may still change and the test suite isn't complete yet.

See <https://github.com/odkr/properset.lua> for details.