proposition: Lemma cast_intpartnK m n eq_m_n : cancel (@cast_intpartn m n eq_m_n) (cast_intpartn (esym eq_m_n)).
proof: Proof. Proof using. by subst m. Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(div ssralg ssrint ssrnum binomial) tools combclass sorted ordtype