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[Merged by Bors] - feat(order/filter): change definition of inf #8657
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LGTM. I'll leave some time for others to have a look if they want, but still I think we should merge this pretty quickly to avoid conflicts. |
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I golfed a few proofs. LGTM. Thanks! |
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also renames lots of lemmas to remove the word "sets" that was a remnant of the very early days.
Co-authored-by: sgouezel <sebastien.gouezel@univ-rennes1.fr>
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The current definition of `filter.inf` came directly from the Galois insertion: `u ∈ f ⊓ g` if it contains `s ∩ t` for some `s ∈ f` and `t ∈ g`, but the new one is tidier: `u ∈ f ⊓ g` if `u = s ∩ t` for some `s ∈ f` and `t ∈ g`. This gives a stronger assertion to work with when assuming a set belongs to a filter inf. On the other hand it makes it harder to prove such a statement so we keep the old version as a lemma `filter.mem_inf_of_inter : ∀ {f g : filter α} {s t u : set α}, s ∈ f → t ∈ g → s ∩ t ⊆ u → u ∈ f ⊓ g`. Also renames lots of lemmas to remove the word "sets" that was a remnant of the very early days. In passing I also changed the simp lemma `filter.mem_map` from `t ∈ map m f ↔ {x | m x ∈ t} ∈ f` to `t ∈ map m f ↔ m ⁻¹' t ∈ f` which seemed more normal form to me. But this led to a lot of breakage, so I also kept the old version as `mem_map'`. Co-authored-by: Yury G. Kudryashov <urkud@urkud.name>
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Also finishes the filter inf work from #8657 proving stronger lemmas for filter.infi
Also finishes the filter inf work from #8657 proving stronger lemmas for filter.infi Co-authored-by: Johan Commelin <johan@commelin.net>
The current definition of
filter.inf
came directly from the Galois insertion:u ∈ f ⊓ g
if it containss ∩ t
for somes ∈ f
andt ∈ g
, but the new one is tidier:u ∈ f ⊓ g
ifu = s ∩ t
for somes ∈ f
andt ∈ g
. This gives a stronger assertion to work with when assuming a set belongs to a filter inf. On the other hand it makes it harder to prove such a statement so we keep the old version as a lemmafilter.mem_inf_of_inter : ∀ {f g : filter α} {s t u : set α}, s ∈ f → t ∈ g → s ∩ t ⊆ u → u ∈ f ⊓ g
.Also renames lots of lemmas to remove the word "sets" that was a remnant of the very early days.
In passing I also changed the simp lemma
filter.mem_map
fromt ∈ map m f ↔ {x | m x ∈ t} ∈ f
tot ∈ map m f ↔ m ⁻¹' t ∈ f
which seemed more normal form to me. But this led to a lot of breakage, so I also kept the old version asmem_map'
.