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 univ and inter properties?

Adam Topaz (Feb 26 2026 at 13:06):

Yury G. Kudryashov said:

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 univ and inter properties?

@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