cogset
Add a type cogset A
of finite/cofinite sets of elements of countable type A
. When A
is also infinite, all the usual operations are decidable. The implementation uses a pair of constructors (finite or infinite) each carrying a finite set.
The file includes efficient conversions to and from gset A
(for finite cogsets) and to coPset
(for arbitrary cogsets), as well as less efficient conversions to and from other finite sets and other sets with a top element.
Two things are marked TODO in the source, which really means "to discuss".
Edited by David Swasey