proposition: Lemma partdom_union_intpart (s1 s2 t1 t2 : intpart) : partdom s1 s2 -> partdom t1 t2 -> partdom (union_intpart s1 t1) (union_intpart s2 t2).
proof: Proof. move=> /partdom_union_intpartr-/(_ t1)/partdom_trans Hs Ht; apply: Hs. by move: Ht => /partdom_union_intpartl; apply. Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(div ssralg ssrint ssrnum binomial) tools combclass sorted ordtype