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[Merged by Bors] - chore(topology/order): relate Sup and Inf of topologies to generate_from #9045

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Since there is a Galois insertion between generate_from : set (set α) → topological_space α and the "forgetful functor" topological_space α → set (set α), all kinds of lemmas about the interaction of generate_from and the ordering on topologies automatically follow. But it is hard to use the Galois insertion lemmas directly, because the Galois insertion is actually provided for the dual order on topologies, which confuses Lean. Here we re-state most of the Galois insertion API in this special case.


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@hrmacbeth hrmacbeth added the awaiting-review The author would like community review of the PR label Sep 7, 2021
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Comment on lines 213 to 219
@galois_insertion.u_le_u_iff _ _ _ _ _
(@partial_order.to_preorder _
(@semilattice_sup.to_partial_order _
(@lattice.to_semilattice_sup _
(@bounded_lattice.to_lattice _
(@complete_lattice.to_bounded_lattice _ tmp_complete_lattice)))))
(gi_generate_from α) a b
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Suggested change
@galois_insertion.u_le_u_iff _ _ _ _ _
(@partial_order.to_preorder _
(@semilattice_sup.to_partial_order _
(@lattice.to_semilattice_sup _
(@bounded_lattice.to_lattice _
(@complete_lattice.to_bounded_lattice _ tmp_complete_lattice)))))
(gi_generate_from α) a b
@galois_insertion.u_le_u_iff _ (order_dual (topological_space α)) _ _ _ _ (gi_generate_from α) a b

Hopefully the same works below?

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Thanks, yes! I've changed throughout. I'm suprised because order_dual (topological_space α) actually carries the dual of the dual of tmp_order, whereas the Galois insertion is stated for tmp_order. I had assumed that an order was not defeq to its double dual.

@semorrison semorrison added awaiting-author A reviewer has asked the author a question or requested changes and removed awaiting-review The author would like community review of the PR labels Sep 7, 2021
@hrmacbeth hrmacbeth added awaiting-review The author would like community review of the PR and removed awaiting-author A reviewer has asked the author a question or requested changes labels Sep 7, 2021
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LGTM!

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Thanks 🎉

bors merge

@github-actions github-actions bot added ready-to-merge All that is left is for bors to build and merge this PR. (Remember you need to say `bors r+`.) and removed awaiting-review The author would like community review of the PR labels Sep 8, 2021
bors bot pushed a commit that referenced this pull request Sep 8, 2021
…from` (#9045)

Since there is a Galois insertion between `generate_from : set (set α) → topological_space α` and the "forgetful functor" `topological_space α → set (set α)`, all kinds of lemmas about the interaction of `generate_from` and the ordering on topologies automatically follow.  But it is hard to use the Galois insertion lemmas directly, because the Galois insertion is actually provided for the dual order on topologies, which confuses Lean.  Here we re-state most of the Galois insertion API in this special case.



Co-authored-by: Johan Commelin <johan@commelin.net>
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bors bot commented Sep 8, 2021

Pull request successfully merged into master.

Build succeeded:

@bors bors bot changed the title chore(topology/order): relate Sup and Inf of topologies to generate_from [Merged by Bors] - chore(topology/order): relate Sup and Inf of topologies to generate_from Sep 8, 2021
@bors bors bot closed this Sep 8, 2021
@bors bors bot deleted the topology-Inf-Sup branch September 8, 2021 14:00
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3 participants