proposition: Lemma ceil_ge0 x : 0 <= x -> 0 <= ceil x.
proof: Proof. by move/(ge_trans (ceil_ge x)); rewrite -(ler_int R). Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra) mathcomp(mathcomp_extra boolp classical_sets set_interval) Setoid