theorem Set.notMem_setOf_iff
theorem Set.notMem_setOf_iff: ∀ {α : Type u} {a : α} {p : α → Prop}, (¬a ∈ setOf fun x => p x) ↔ ¬p a
theorem Set.notMem_setOf_iff
theorem Set.notMem_setOf_iff: ∀ {α : Type u} {a : α} {p : α → Prop}, (¬a ∈ setOf fun x => p x) ↔ ¬p a