proposition: Lemma uniq_rangeR f1 f2 : valid (f1 \+ f2) -> uniq (range (f1 \+ f2)) -> uniq (range f2).
proof: Proof. by move=>W; rewrite uniq_rangeUn // cat_uniq; case/and3P. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)