proposition: Lemma dom2E (f1 : U1) (f2 : U2) : dom f1 =i dom f2 <-> dom f1 = dom f2.
proof: Proof. split=>[|->] //; apply/ord_sorted_eq/sorted_dom/sorted_dom. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)