(* *)
(**************************************************************************)
-include "ground_2/arith.ma".
+include "ground_2/lib/arith.ma".
(* SORT HIERARCHY ***********************************************************)
}.
definition sh_N: sh ≝ mk_sh S ….
-// qed.
+// defined.
(* Basic properties *********************************************************)
lemma nexts_le: ∀h,k,l. k ≤ (next h)^l k.
#h #k #l elim l -l // normalize #l #IHl
lapply (next_lt h ((next h)^l k)) #H
-lapply (le_to_lt_to_lt … IHl H) -IHl -H /2 width=2/
+lapply (le_to_lt_to_lt … IHl H) -IHl -H /2 width=2 by lt_to_le/
+qed.
+
+lemma nexts_lt: ∀h,k,l. k < (next h)^(l+1) k.
+#h #k #l >iter_SO
+lapply (nexts_le h k l) #H
+@(le_to_lt_to_lt … H) //
qed.
axiom nexts_dec: ∀h,k1,k2. Decidable (∃l. (next h)^l k1 = k2).
axiom nexts_inj: ∀h,k,l1,l2. (next h)^l1 k = (next h)^l2 k → l1 = l2.
-