Oh cool empty set symbol

Changes

1 changed files (+1/-1)

• Set.lean
  • @@ -10,7 +10,7 @@ lemma add_def {a b : Set α} : a + b = a ∆ b := rfl
    instance : Zero (Set α) := ⟨{}⟩ @[simp] - lemma zero_def : (0 : Set α) = {} := rfl + lemma zero_def : (0 : Set α) = ∅ := rfl instance : Neg (Set α) := ⟨id⟩