fact: Definition option_relation {A B} (R: A → B → Prop) (P: A → Prop) (Q: B → Prop) (mx : option A) (my : option B) : Prop := match mx, my with | Some x, Some y => R x y | Some x, None => P x | None, Some y => Q y | None, None => True end.
imports: stdpp(options)