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chore(Order/Filter/CardinalInter): fix typos and polish docs (#31624)
Issues found and fixed with help from Codex.
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Mathlib/Order/Filter/CardinalInter.lean

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@@ -25,7 +25,7 @@ their intersection belongs to `l` as well.
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`c > ℵ₀` is a `CountableInterFilter`.
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* `CountableInterFilter.toCardinalInterFilter` establishes that every `CountableInterFilter l` is a
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`CardinalInterFilter l ℵ₁`.
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* `CardinalInterFilter.of_CardinalInterFilter_of_lt` establishes that we have
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* `CardinalInterFilter.of_cardinalInterFilter_of_lt` establishes that we have
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`CardinalInterFilter l c` → `CardinalInterFilter l a` for all `a < c`.
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## Tags
@@ -77,7 +77,7 @@ theorem cardinalInterFilter_aleph_one_iff :
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CardinalInterFilter.cardinal_sInter_mem S ((countable_iff_lt_aleph_one S).1 h) a⟩,
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fun _ ↦ CountableInterFilter.toCardinalInterFilter l⟩
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/-- Every CardinalInterFilter for some c also is a CardinalInterFilter for some a ≤ c -/
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/-- Every `CardinalInterFilter` for some `c` also is a `CardinalInterFilter` for any `a ≤ c`. -/
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theorem CardinalInterFilter.of_cardinalInterFilter_of_le (l : Filter α) [CardinalInterFilter l c]
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{a : Cardinal.{u}} (hac : a ≤ c) :
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CardinalInterFilter l a where
@@ -287,7 +287,8 @@ inductive CardinalGenerateSets : Set α → Prop
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| sInter {S : Set (Set α)} :
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(#S < c) → (∀ s ∈ S, CardinalGenerateSets s) → CardinalGenerateSets (⋂₀ S)
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/-- `Filter.cardinalGenerate c g` is the greatest `cardinalInterFilter c` containing `g`. -/
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/-- Assuming `2 < c`, `Filter.cardinalGenerate c g` is the greatest `CardinalInterFilter c`
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containing `g`. -/
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def cardinalGenerate (hc : 2 < c) : Filter α :=
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ofCardinalInter (CardinalGenerateSets g) hc (fun _ => CardinalGenerateSets.sInter) fun _ _ =>
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CardinalGenerateSets.superset
@@ -301,7 +302,7 @@ variable {g}
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/-- A set is in the `cardinalInterFilter` generated by `g` if and only if
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it contains an intersection of `c` elements of `g`. -/
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theorem mem_cardinaleGenerate_iff {s : Set α} {hreg : c.IsRegular} :
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theorem mem_cardinalGenerate_iff {s : Set α} {hreg : c.IsRegular} :
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s ∈ cardinalGenerate g (IsRegular.nat_lt hreg 2) ↔
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∃ S : Set (Set α), S ⊆ g ∧ (#S < c) ∧ ⋂₀ S ⊆ s := by
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constructor <;> intro h
@@ -324,6 +325,8 @@ theorem mem_cardinaleGenerate_iff {s : Set α} {hreg : c.IsRegular} :
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exact mem_of_superset ((cardinal_sInter_mem Sct).mpr
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(fun s H => CardinalGenerateSets.basic (Sg H))) hS
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@[deprecated (since := "2025-11-14")] alias mem_cardinaleGenerate_iff := mem_cardinalGenerate_iff
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theorem le_cardinalGenerate_iff_of_cardinalInterFilter {f : Filter α} [CardinalInterFilter f c]
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(hc : 2 < c) : f ≤ cardinalGenerate g hc ↔ g ⊆ f.sets := by
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constructor <;> intro h
@@ -335,7 +338,7 @@ theorem le_cardinalGenerate_iff_of_cardinalInterFilter {f : Filter α} [Cardinal
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| superset _ st ih => exact mem_of_superset ih st
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| sInter Sct _ ih => exact (cardinal_sInter_mem Sct).mpr ih
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/-- `cardinalGenerate g hc` is the greatest `cardinalInterFilter c` containing `g`. -/
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/-- `cardinalGenerate g hc` is the greatest `CardinalInterFilter c` containing `g`. -/
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theorem cardinalGenerate_isGreatest (hc : 2 < c) :
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IsGreatest { f : Filter α | CardinalInterFilter f c ∧ g ⊆ f.sets } (cardinalGenerate g hc) := by
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refine ⟨⟨cardinalInter_ofCardinalGenerate _ _, fun s => CardinalGenerateSets.basic⟩, ?_⟩

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