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-rw-r--r--theories/QArith/Qreduction.v166
1 files changed, 67 insertions, 99 deletions
diff --git a/theories/QArith/Qreduction.v b/theories/QArith/Qreduction.v
index e39eca0c..3b3a30eb 100644
--- a/theories/QArith/Qreduction.v
+++ b/theories/QArith/Qreduction.v
@@ -1,6 +1,6 @@
(************************************************************************)
(* v * The Coq Proof Assistant / The Coq Development Team *)
-(* <O___,, * INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2010 *)
+(* <O___,, * INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2012 *)
(* \VV/ **************************************************************)
(* // * This file is distributed under the terms of the *)
(* * GNU Lesser General Public License Version 2.1 *)
@@ -11,46 +11,29 @@
Require Export QArith_base.
Require Import Znumtheory.
-(** First, a function that (tries to) build a positive back from a Z. *)
+Notation Z2P := Z.to_pos (compat "8.3").
+Notation Z2P_correct := Z2Pos.id (compat "8.3").
-Definition Z2P (z : Z) :=
- match z with
- | Z0 => 1%positive
- | Zpos p => p
- | Zneg p => p
- end.
-
-Lemma Z2P_correct : forall z : Z, (0 < z)%Z -> Zpos (Z2P z) = z.
-Proof.
- simple destruct z; simpl in |- *; auto; intros; discriminate.
-Qed.
-
-Lemma Z2P_correct2 : forall z : Z, 0%Z <> z -> Zpos (Z2P z) = Zabs z.
-Proof.
- simple destruct z; simpl in |- *; auto; intros; elim H; auto.
-Qed.
-
-(** Simplification of fractions using [Zgcd].
+(** Simplification of fractions using [Z.gcd].
This version can compute within Coq. *)
Definition Qred (q:Q) :=
let (q1,q2) := q in
- let (r1,r2) := snd (Zggcd q1 ('q2))
- in r1#(Z2P r2).
+ let (r1,r2) := snd (Z.ggcd q1 ('q2))
+ in r1#(Z.to_pos r2).
Lemma Qred_correct : forall q, (Qred q) == q.
Proof.
unfold Qred, Qeq; intros (n,d); simpl.
- generalize (Zggcd_gcd n ('d)) (Zgcd_nonneg n ('d))
- (Zggcd_correct_divisors n ('d)).
- destruct (Zggcd n (Zpos d)) as (g,(nn,dd)); simpl.
+ generalize (Z.ggcd_gcd n ('d)) (Z.gcd_nonneg n ('d))
+ (Z.ggcd_correct_divisors n ('d)).
+ destruct (Z.ggcd n (Zpos d)) as (g,(nn,dd)); simpl.
Open Scope Z_scope.
intros Hg LE (Hn,Hd). rewrite Hd, Hn.
rewrite <- Hg in LE; clear Hg.
assert (0 <> g) by (intro; subst; discriminate).
- rewrite Z2P_correct. ring.
- apply Zmult_gt_0_lt_0_reg_r with g; auto with zarith.
- now rewrite Zmult_comm, <- Hd.
+ rewrite Z2Pos.id. ring.
+ rewrite <- (Z.mul_pos_cancel_l g); [now rewrite <- Hd | omega].
Close Scope Z_scope.
Qed.
@@ -59,68 +42,54 @@ Proof.
intros (a,b) (c,d).
unfold Qred, Qeq in *; simpl in *.
Open Scope Z_scope.
- generalize (Zggcd_gcd a ('b)) (Zgcd_is_gcd a ('b))
- (Zgcd_nonneg a ('b)) (Zggcd_correct_divisors a ('b)).
- destruct (Zggcd a (Zpos b)) as (g,(aa,bb)).
- generalize (Zggcd_gcd c ('d)) (Zgcd_is_gcd c ('d))
- (Zgcd_nonneg c ('d)) (Zggcd_correct_divisors c ('d)).
- destruct (Zggcd c (Zpos d)) as (g',(cc,dd)).
- simpl.
- intro H; rewrite <- H; clear H.
- intros Hg'1 Hg'2 (Hg'3,Hg'4).
- intro H; rewrite <- H; clear H.
- intros Hg1 Hg2 (Hg3,Hg4).
- intros.
- assert (g <> 0) by (intro; subst g; discriminate).
- assert (g' <> 0) by (intro; subst g'; discriminate).
+ intros H.
+ generalize (Z.ggcd_gcd a ('b)) (Zgcd_is_gcd a ('b))
+ (Z.gcd_nonneg a ('b)) (Z.ggcd_correct_divisors a ('b)).
+ destruct (Z.ggcd a (Zpos b)) as (g,(aa,bb)).
+ simpl. intros <- Hg1 Hg2 (Hg3,Hg4).
+ assert (Hg0 : g <> 0) by (intro; now subst g).
+ generalize (Z.ggcd_gcd c ('d)) (Zgcd_is_gcd c ('d))
+ (Z.gcd_nonneg c ('d)) (Z.ggcd_correct_divisors c ('d)).
+ destruct (Z.ggcd c (Zpos d)) as (g',(cc,dd)).
+ simpl. intros <- Hg'1 Hg'2 (Hg'3,Hg'4).
+ assert (Hg'0 : g' <> 0) by (intro; now subst g').
elim (rel_prime_cross_prod aa bb cc dd).
- congruence.
- unfold rel_prime in |- *.
- (*rel_prime*)
- constructor.
- exists aa; auto with zarith.
- exists bb; auto with zarith.
- intros.
- inversion Hg1.
- destruct (H6 (g*x)) as (x',Hx).
- rewrite Hg3.
- destruct H2 as (xa,Hxa); exists xa; rewrite Hxa; ring.
- rewrite Hg4.
- destruct H3 as (xb,Hxb); exists xb; rewrite Hxb; ring.
- exists x'.
- apply Zmult_reg_l with g; auto. rewrite Hx at 1; ring.
- (* /rel_prime *)
- unfold rel_prime in |- *.
- (* rel_prime *)
- constructor.
- exists cc; auto with zarith.
- exists dd; auto with zarith.
- intros.
- inversion Hg'1.
- destruct (H6 (g'*x)) as (x',Hx).
- rewrite Hg'3.
- destruct H2 as (xc,Hxc); exists xc; rewrite Hxc; ring.
- rewrite Hg'4.
- destruct H3 as (xd,Hxd); exists xd; rewrite Hxd; ring.
- exists x'.
- apply Zmult_reg_l with g'; auto. rewrite Hx at 1; ring.
- (* /rel_prime *)
- assert (0<bb); [|auto with zarith].
- apply Zmult_gt_0_lt_0_reg_r with g.
- omega.
- rewrite Zmult_comm.
- rewrite <- Hg4; compute; auto.
- assert (0<dd); [|auto with zarith].
- apply Zmult_gt_0_lt_0_reg_r with g'.
- omega.
- rewrite Zmult_comm.
- rewrite <- Hg'4; compute; auto.
- apply Zmult_reg_l with (g'*g).
- intro H2; elim (Zmult_integral _ _ H2); auto.
- replace (g'*g*(aa*dd)) with ((g*aa)*(g'*dd)); [|ring].
- replace (g'*g*(bb*cc)) with ((g'*cc)*(g*bb)); [|ring].
- rewrite <- Hg3; rewrite <- Hg4; rewrite <- Hg'3; rewrite <- Hg'4; auto.
+ - congruence.
+ - (*rel_prime*)
+ constructor.
+ * exists aa; auto with zarith.
+ * exists bb; auto with zarith.
+ * intros x Ha Hb.
+ destruct Hg1 as (Hg11,Hg12,Hg13).
+ destruct (Hg13 (g*x)) as (x',Hx).
+ { rewrite Hg3.
+ destruct Ha as (xa,Hxa); exists xa; rewrite Hxa; ring. }
+ { rewrite Hg4.
+ destruct Hb as (xb,Hxb); exists xb; rewrite Hxb; ring. }
+ exists x'.
+ apply Z.mul_reg_l with g; auto. rewrite Hx at 1; ring.
+ - (* rel_prime *)
+ constructor.
+ * exists cc; auto with zarith.
+ * exists dd; auto with zarith.
+ * intros x Hc Hd.
+ inversion Hg'1 as (Hg'11,Hg'12,Hg'13).
+ destruct (Hg'13 (g'*x)) as (x',Hx).
+ { rewrite Hg'3.
+ destruct Hc as (xc,Hxc); exists xc; rewrite Hxc; ring. }
+ { rewrite Hg'4.
+ destruct Hd as (xd,Hxd); exists xd; rewrite Hxd; ring. }
+ exists x'.
+ apply Z.mul_reg_l with g'; auto. rewrite Hx at 1; ring.
+ - apply Z.lt_gt.
+ rewrite <- (Z.mul_pos_cancel_l g); [now rewrite <- Hg4 | omega].
+ - apply Z.lt_gt.
+ rewrite <- (Z.mul_pos_cancel_l g'); [now rewrite <- Hg'4 | omega].
+ - apply Z.mul_reg_l with (g*g').
+ * rewrite Z.mul_eq_0. now destruct 1.
+ * rewrite Z.mul_shuffle1, <- Hg3, <- Hg'4.
+ now rewrite Z.mul_shuffle1, <- Hg'3, <- Hg4, H, Z.mul_comm.
Close Scope Z_scope.
Qed.
@@ -137,39 +106,39 @@ Definition Qminus' x y := Qred (Qminus x y).
Lemma Qplus'_correct : forall p q : Q, (Qplus' p q)==(Qplus p q).
Proof.
- intros; unfold Qplus' in |- *; apply Qred_correct; auto.
+ intros; unfold Qplus'; apply Qred_correct; auto.
Qed.
Lemma Qmult'_correct : forall p q : Q, (Qmult' p q)==(Qmult p q).
Proof.
- intros; unfold Qmult' in |- *; apply Qred_correct; auto.
+ intros; unfold Qmult'; apply Qred_correct; auto.
Qed.
Lemma Qminus'_correct : forall p q : Q, (Qminus' p q)==(Qminus p q).
Proof.
- intros; unfold Qminus' in |- *; apply Qred_correct; auto.
+ intros; unfold Qminus'; apply Qred_correct; auto.
Qed.
Add Morphism Qplus' : Qplus'_comp.
Proof.
- intros; unfold Qplus' in |- *.
- rewrite H; rewrite H0; auto with qarith.
+ intros; unfold Qplus'.
+ rewrite H, H0; auto with qarith.
Qed.
Add Morphism Qmult' : Qmult'_comp.
- intros; unfold Qmult' in |- *.
- rewrite H; rewrite H0; auto with qarith.
+ intros; unfold Qmult'.
+ rewrite H, H0; auto with qarith.
Qed.
Add Morphism Qminus' : Qminus'_comp.
- intros; unfold Qminus' in |- *.
- rewrite H; rewrite H0; auto with qarith.
+ intros; unfold Qminus'.
+ rewrite H, H0; auto with qarith.
Qed.
Lemma Qred_opp: forall q, Qred (-q) = - (Qred q).
Proof.
intros (x, y); unfold Qred; simpl.
- rewrite Zggcd_opp; case Zggcd; intros p1 (p2, p3); simpl.
+ rewrite Z.ggcd_opp; case Z.ggcd; intros p1 (p2, p3); simpl.
unfold Qopp; auto.
Qed.
@@ -178,4 +147,3 @@ Theorem Qred_compare: forall x y,
Proof.
intros x y; apply Qcompare_comp; apply Qeq_sym; apply Qred_correct.
Qed.
-
generated by cgit v1.2.3 (git 2.39.1) at 2024-05-20 16:35:49 +0000