proposition: Lemma lef_trans g f h : f <=1 g -> g <=1 h -> f <=1 h.
proof: Proof. by move=> h1 h2 x; apply/(le_trans (h1 x)). Qed.
imports: mathcomp(all_ssreflect all_algebra) mathcomp.bigenough.bigenough mathcomp.classical(boolp classical_sets functions) mathcomp.classical(mathcomp_extra) xfinmap ereal reals discrete topology