proposition: Lemma umall2KR f1 f2 g1 g2 : Equivalence_rel P -> valid (f1 \+ g1) -> valid (f2 \+ g2) -> um_all2 (f1 \+ g1) (f2 \+ g2) -> um_all2 g1 g2 -> um_all2 f1 f2.
proof: Proof. by rewrite (joinC f1) (joinC f2); apply: umall2KL. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)