diff --git a/src/data/finset.lean b/src/data/finset.lean index 4bc87379e757d..f3eac9a819285 100644 --- a/src/data/finset.lean +++ b/src/data/finset.lean @@ -2562,6 +2562,10 @@ lemma disjoint_filter {s : finset α} {p q : α → Prop} [decidable_pred p] [de disjoint (s.filter p) (s.filter q) ↔ (∀ x ∈ s, p x → ¬ q x) := by split; simp [disjoint_left] {contextual := tt} +lemma disjoint_filter_filter {s t : finset α} {p q : α → Prop} [decidable_pred p] [decidable_pred q] : + (disjoint s t) → disjoint (s.filter p) (t.filter q) := +disjoint.mono (filter_subset _) (filter_subset _) + lemma pi_disjoint_of_disjoint {δ : α → Type*} [∀a, decidable_eq (δ a)] {s : finset α} [decidable_eq (Πa∈s, δ a)] (t₁ t₂ : Πa, finset (δ a)) {a : α} (ha : a ∈ s) (h : disjoint (t₁ a) (t₂ a)) :