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chore: fix statement of List.filter_congr #4524

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Jun 21, 2024
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chore: fix statement of List.filter_congr #4524

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4d923f6
chore: fix statement of List.filter_congr
kim-em Jun 21, 2024
3733a90
fix proof
kim-em Jun 21, 2024
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6 changes: 3 additions & 3 deletions src/Init/Data/List/Lemmas.lean
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Original file line number Diff line number Diff line change
Expand Up @@ -923,12 +923,12 @@ theorem map_filter_eq_foldr (f : α → β) (p : α → Bool) (as : List α) :
| a :: l₁, l₂ => by simp [filter]; split <;> simp [filter_append l₁]

theorem filter_congr {p q : α → Bool} :
∀ {l : List α}, (∀ x ∈ l, p x ↔ q x) → filter p l = filter q l
∀ {l : List α}, (∀ x ∈ l, p x = q x) → filter p l = filter q l
| [], _ => rfl
| a :: l, h => by
rw [forall_mem_cons] at h; by_cases pa : p a
· simp [pa, h.1.1 pa, filter_congr h.2]
· simp [pa, mt h.1.2 pa, filter_congr h.2]
· simp [pa, h.1 ▸ pa, filter_congr h.2]
· simp [pa, h.1 ▸ pa, filter_congr h.2]

@[deprecated filter_congr (since := "2024-06-20")] abbrev filter_congr' := @filter_congr

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