proposition: Lemma intpartn3 (sh : 'P_3) : [\/ sh = rowpartn 3, sh = hookpartn 3 1 | sh = colpartn 3].
proof: Proof. by case: (val_intpartn3 sh) => sheq; [apply Or31 | apply Or32 | apply Or33]; apply val_inj; rewrite /= {}sheq ?rowpartnE ?hookpartnE ?colpartnE. Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(div ssralg ssrint ssrnum binomial) tools combclass sorted ordtype