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+(************************************************************************)
+(*  v      *   The Coq Proof Assistant  /  The Coq Development Team     *)
+(* <O___,, * CNRS-Ecole Polytechnique-INRIA Futurs-Universite Paris Sud *)
+(*   \VV/  **************************************************************)
+(*    //   *      This file is distributed under the terms of the       *)
+(*         *       GNU Lesser General Public License Version 2.1        *)
+(************************************************************************)
+Require Compare_dec.
+Require Wf_nat.
+
+Section Iter.
+Variable A : Type.
+
+Fixpoint iter (n : nat) : (A -> A) -> A -> A :=
+  fun (fl : A -> A) (def : A) =>
+  match n with
+  | O => def
+  | S m => fl (iter m fl def)
+  end.
+End Iter.
+
+Theorem SSplus_lt : forall p p' : nat, p < S (S (p + p')).
+  intro p; intro p'; change (S p <= S (S (p + p'))); 
+    apply le_S; apply Gt.gt_le_S; change (p < S (p + p')); 
+    apply Lt.le_lt_n_Sm; apply Plus.le_plus_l.
+Qed.
+ 
+
+Theorem Splus_lt : forall p p' : nat, p' < S (p + p').
+  intro p; intro p'; change (S p' <= S (p + p')); 
+    apply Gt.gt_le_S; change (p' < S (p + p')); apply Lt.le_lt_n_Sm;
+       apply Plus.le_plus_r.
+Qed.
+
+Theorem le_lt_SS : forall x y, x <= y -> x < S (S y).
+intro x; intro y; intro H; change (S x <= S (S y)); 
+    apply le_S; apply Gt.gt_le_S; change (x < S y); 
+    apply Lt.le_lt_n_Sm; exact H.
+Qed.
+
+Inductive max_type (m n:nat) : Set :=
+  cmt : forall v, m <= v -> n <= v -> max_type m n.
+
+Definition max : forall m n:nat, max_type m n.
+intros m n; case (Compare_dec.le_gt_dec m n).
+intros h; exists n; [exact h | apply le_n].
+intros h; exists m; [apply le_n | apply Lt.lt_le_weak; exact h].
+Defined.