(** This file is part of the Coquelicot formalization of real analysis in Coq: http://coquelicot.saclay.inria.fr/  Copyright (C) 2011-2015 Sylvie Boldo #<br /># Copyright (C) 2011-2015 Catherine Lelay #<br /># Copyright (C) 2011-2015 Guillaume Melquiond  This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.  This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the COPYING file for more details. *)
(** * This file describes basic missing facts about the standard library of reals and a few concerning ssreflect.seq. It also contains a definition of the [sign] function. *)
(** Tactic for changing the last argument of a property to an evar, in order to apply theorems modulo equality. *)
Ltac evar_last :=
match goal with
| |- ?f ?x =>
let tx := type of x in
let tx := eval simpl in tx in
let tmp := fresh "tmp" in
evar (tmp : tx) ;
refine (@eq_ind tx tmp f _ x _) ;
unfold tmp ; clear tmp
end.
Module MyNat.

Lemma sub_succ_r (n m : nat) : n - S m = pred (n - m).