proposition: Lemma instab_non_nil t l : instab t l != [::].
proof: Proof. Proof using. by case: t => [// | t0 t] /=; case (bumprow t0 l) => [[ll|]] l0. Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(perm fingroup) tools partition Yamanouchi ordtype subseq tableau std stdtab