proposition: Lemma cast_intpartn_id n eq_n (s : 'P_n) : cast_intpartn eq_n s = s.
proof: Proof. Proof using. by apply val_inj => /=; rewrite cast_intpartnE. Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(div ssralg ssrint ssrnum binomial) tools combclass sorted ordtype