proposition: Lemma pcmFJ (x y : U * V) : (x \+ y).1 = x.1 \+ y.1.
proof: Proof. by rewrite pcmE. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq bigop fintype finset) pcm(options axioms prelude seqperm pred seqext)