proposition: Lemma ltrD2l x : {mono +%R x : y z / y < z}.
proof: Proof. by move=> y z; rewrite (leW_mono (lerD2l _)). Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)