proposition: Lemma pleq_validL (x x1 x2 : U) : [pcm x1 <= x2] -> valid (x \+ x2) -> valid (x \+ x1).
proof: Proof. by case=>a -> V; rewrite (validRE3 V). Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq bigop fintype finset) pcm(options axioms prelude seqperm pred seqext)