proposition: Lemma pfUn e (x y : U) : valid (x \+ y) -> S x y -> e \In f (x \+ y) -> e \In f x \/ e \In f y.
proof: Proof. by move=>W H1; rewrite pfjoin //; case/InUn; eauto. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path interval) pcm(options prelude pred finmap rtc seqext useqord uslice uconsec)