Zulip Chat Archive
Stream: mathlib4
Topic: Inductive sets (finiteInterClosure)
Yury G. Kudryashov (Feb 26 2026 at 05:27):
Another offender is docs#FiniteInter.finiteInterClosure. It's an inductive predicate of type Set _. @Adam Topaz what do you prefer
- add an auxiliary inductive predicate, then use
setOf - redefine it as a set of intersections of finite subfamilies
- redefine it as the intersection of all sets that contain our set and satisfy the
univandinterproperties?
Adam Topaz (Feb 26 2026 at 13:06):
Yury G. Kudryashov said:
Another offender is docs#FiniteInter.finiteInterClosure. It's an
inductivepredicate of typeSet _. Adam Topaz what do you prefer
- add an auxiliary inductive predicate, then use
setOf- redefine it as a set of intersections of finite subfamilies
- redefine it as the intersection of all sets that contain our set and satisfy the
univandinterproperties?
@Yury G. Kudryashov I would prefer making an auxiliary inductive predicate in this case. Do I understand correctly that we are effectively banning the (direct) creation of inductive sets in the sense of inductive foo : Set X where ...?
Last updated: Feb 28 2026 at 14:05 UTC