proposition: Lemma lteD2lE x a b : x \is a fin_num -> (x + a < x + b) = (a < b).
proof: Proof. move: a b x => [a| |] [b| |] [x| |] _ //; rewrite ?(ltry, ltNyr)//. by rewrite !lte_fin ltrD2l. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap) mathcomp(mathcomp_extra) signed