(************************************************************************)
(*  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        *)
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(*i 	$Id$	 i*)
Section MapCard.
Variables A B : Type.

Lemma length_as_fold :
forall (C:Type) (l:list C),
length l = fold_right (fun (_:C) (n:nat) => S n) 0 l.