proposition: Lemma le_YoungP sh1 sh2 : reflect (forall i, nth 0 sh1 i <= nth 0 sh2 i) (sh1 <= sh2)%O.
proof: Proof. exact: (iffP (part_includedP _ (intpartP sh1))). Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(div ssralg ssrint ssrnum binomial) tools combclass sorted ordtype