fact: Definition stal (m : nat) (Ar : rArray vM) (a b : rZ) : mbDT := match addEqMem Ar a b with | triple Ar1 true L1 => quatuor _ _ _ _ Ar true nil emptyTrace | triple Ar1 false L1 => match stalN L1 0 m Ar1 with | quatuor Ar2 b2 L2 T2 => quatuor _ _ _ _ Ar2 b2 (appendRz L1 L2) T2 end end.