proposition: Lemma corner_arm_length0 sh rc : is_part sh -> corner_box sh rc -> arm_length sh rc = 0.
proof: Proof. move: rc => [r c]. rewrite /corner_box /is_rem_corner /arm_length => Hpart /=/andP[_ /eqP ->]. by case: (nth 0 sh r) => // n; rewrite subSn //= subnn. Qed.
imports: Misc Ccpo mathcomp(all_ssreflect) mathcomp(ssrint div rat ssralg ssrnum) tools subseq partition Yamanouchi stdtab Qmeasure