proposition: Lemma cast_intpartn_bij m n eq_m_n : bijective (@cast_intpartn m n eq_m_n).
proof: Proof. Proof using. exact: Bijective (cast_intpartnK eq_m_n) (cast_intpartnKV _). Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(div ssralg ssrint ssrnum binomial) tools combclass sorted ordtype