diff options
Diffstat (limited to 'theories/ZArith/Zdiv.v')
| -rw-r--r-- | theories/ZArith/Zdiv.v | 24 |
1 files changed, 11 insertions, 13 deletions
diff --git a/theories/ZArith/Zdiv.v b/theories/ZArith/Zdiv.v index 2e3a2280..d0d10891 100644 --- a/theories/ZArith/Zdiv.v +++ b/theories/ZArith/Zdiv.v @@ -1,7 +1,7 @@ (* -*- coding: utf-8 -*- *) (************************************************************************) (* v * The Coq Proof Assistant / The Coq Development Team *) -(* <O___,, * INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2014 *) +(* <O___,, * INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2015 *) (* \VV/ **************************************************************) (* // * This file is distributed under the terms of the *) (* * GNU Lesser General Public License Version 2.1 *) @@ -666,24 +666,22 @@ Theorem Zdiv_eucl_extended : {qr : Z * Z | let (q, r) := qr in a = b * q + r /\ 0 <= r < Z.abs b}. Proof. intros b Hb a. - elim (Z_le_gt_dec 0 b); intro Hb'. - cut (b > 0); [ intro Hb'' | omega ]. - rewrite Z.abs_eq; [ apply Zdiv_eucl_exist; assumption | assumption ]. - cut (- b > 0); [ intro Hb'' | omega ]. - elim (Zdiv_eucl_exist Hb'' a); intros qr. - elim qr; intros q r Hqr. - exists (- q, r). - elim Hqr; intros. - split. - rewrite <- Z.mul_opp_comm; assumption. - rewrite Z.abs_neq; [ assumption | omega ]. + destruct (Z_le_gt_dec 0 b) as [Hb'|Hb']. + - assert (Hb'' : b > 0) by omega. + rewrite Z.abs_eq; [ apply Zdiv_eucl_exist; assumption | assumption ]. + - assert (Hb'' : - b > 0) by omega. + destruct (Zdiv_eucl_exist Hb'' a) as ((q,r),[]). + exists (- q, r). + split. + + rewrite <- Z.mul_opp_comm; assumption. + + rewrite Z.abs_neq; [ assumption | omega ]. Qed. Arguments Zdiv_eucl_extended : default implicits. (** * Division and modulo in Z agree with same in nat: *) -Require Import NPeano. +Require Import PeanoNat. Lemma div_Zdiv (n m: nat): m <> O -> Z.of_nat (n / m) = Z.of_nat n / Z.of_nat m. |