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(************************************************************************)
(* * The Coq Proof Assistant / The Coq Development Team *)
(* v * INRIA, CNRS and contributors - Copyright 1999-2018 *)
(* <O___,, * (see CREDITS file for the list of authors) *)
(* \VV/ **************************************************************)
(* // * This file is distributed under the terms of the *)
(* * GNU Lesser General Public License Version 2.1 *)
(* * (see LICENSE file for the text of the license) *)
(************************************************************************)
Require Import ZArith_base.
Require Import Zpow_def.
Require Import BinInt.
Require Import BinNat.
Require Import Setoid.
Require Import BinList.
Require Import BinPos.
Require Import BinNat.
Require Import BinInt.
Require Import Setoid.
Require Export Ncring.
Require Export Ncring_polynom.
Set Implicit Arguments.
(* An object to return when an expression is not recognized as a constant *)
Definition NotConstant := false.
(** Z is a ring and a setoid*)
Lemma Zsth : Equivalence (@eq Z).
Proof. exact Z.eq_equiv. Qed.
Instance Zops:@Ring_ops Z 0%Z 1%Z Z.add Z.mul Z.sub Z.opp (@eq Z).
Instance Zr: (@Ring _ _ _ _ _ _ _ _ Zops).
Proof.
constructor; try apply Zsth; try solve_proper.
exact Z.add_comm. exact Z.add_assoc.
exact Z.mul_1_l. exact Z.mul_1_r. exact Z.mul_assoc.
exact Z.mul_add_distr_r. intros; apply Z.mul_add_distr_l. exact Z.sub_diag.
Defined.
(*Instance ZEquality: @Equality Z:= (@eq Z).*)
(** Two generic morphisms from Z to (arbitrary) rings, *)
(**second one is more convenient for proofs but they are ext. equal*)
Section ZMORPHISM.
Context {R:Type}`{Ring R}.
Ltac rrefl := reflexivity.
Fixpoint gen_phiPOS1 (p:positive) : R :=
match p with
| xH => 1
| xO p => (1 + 1) * (gen_phiPOS1 p)
| xI p => 1 + ((1 + 1) * (gen_phiPOS1 p))
end.
Fixpoint gen_phiPOS (p:positive) : R :=
match p with
| xH => 1
| xO xH => (1 + 1)
| xO p => (1 + 1) * (gen_phiPOS p)
| xI xH => 1 + (1 +1)
| xI p => 1 + ((1 + 1) * (gen_phiPOS p))
end.
Definition gen_phiZ1 z :=
match z with
| Zpos p => gen_phiPOS1 p
| Z0 => 0
| Zneg p => -(gen_phiPOS1 p)
end.
Definition gen_phiZ z :=
match z with
| Zpos p => gen_phiPOS p
| Z0 => 0
| Zneg p => -(gen_phiPOS p)
end.
Local Notation "[ x ]" := (gen_phiZ x) : ZMORPHISM.
Local Open Scope ZMORPHISM.
Definition get_signZ z :=
match z with
| Zneg p => Some (Zpos p)
| _ => None
end.
Ltac norm := gen_rewrite.
Ltac add_push := Ncring.gen_add_push.
Ltac rsimpl := simpl.
Lemma same_gen : forall x, gen_phiPOS1 x == gen_phiPOS x.
Proof.
induction x;rsimpl.
rewrite IHx. destruct x;simpl;norm.
rewrite IHx;destruct x;simpl;norm.
reflexivity.
Qed.
Lemma ARgen_phiPOS_Psucc : forall x,
gen_phiPOS1 (Pos.succ x) == 1 + (gen_phiPOS1 x).
Proof.
induction x;rsimpl;norm.
rewrite IHx. gen_rewrite. add_push 1. reflexivity.
Qed.
Lemma ARgen_phiPOS_add : forall x y,
gen_phiPOS1 (x + y) == (gen_phiPOS1 x) + (gen_phiPOS1 y).
Proof.
induction x;destruct y;simpl;norm.
rewrite Pos.add_carry_spec.
rewrite ARgen_phiPOS_Psucc.
rewrite IHx;norm.
add_push (gen_phiPOS1 y);add_push 1;reflexivity.
rewrite IHx;norm;add_push (gen_phiPOS1 y);reflexivity.
rewrite ARgen_phiPOS_Psucc;norm;add_push 1;reflexivity.
rewrite IHx;norm;add_push(gen_phiPOS1 y); add_push 1;reflexivity.
rewrite IHx;norm;add_push(gen_phiPOS1 y);reflexivity.
add_push 1;reflexivity.
rewrite ARgen_phiPOS_Psucc;norm;add_push 1;reflexivity.
Qed.
Lemma ARgen_phiPOS_mult :
forall x y, gen_phiPOS1 (x * y) == gen_phiPOS1 x * gen_phiPOS1 y.
Proof.
induction x;intros;simpl;norm.
rewrite ARgen_phiPOS_add;simpl;rewrite IHx;norm.
rewrite IHx;reflexivity.
Qed.
(*morphisms are extensionally equal*)
Lemma same_genZ : forall x, [x] == gen_phiZ1 x.
Proof.
destruct x;rsimpl; try rewrite same_gen; reflexivity.
Qed.
Lemma gen_Zeqb_ok : forall x y,
Zeq_bool x y = true -> [x] == [y].
Proof.
intros x y H7.
assert (H10 := Zeq_bool_eq x y H7);unfold IDphi in H10.
rewrite H10;reflexivity.
Qed.
Lemma gen_phiZ1_add_pos_neg : forall x y,
gen_phiZ1 (Z.pos_sub x y)
== gen_phiPOS1 x + -gen_phiPOS1 y.
Proof.
intros x y.
generalize (Z.pos_sub_discr x y).
destruct (Z.pos_sub x y) as [|p|p]; intros; subst.
- now rewrite ring_opp_def.
- rewrite ARgen_phiPOS_add;simpl;norm.
add_push (gen_phiPOS1 p). rewrite ring_opp_def;norm.
- rewrite ARgen_phiPOS_add;simpl;norm.
rewrite ring_opp_def;norm.
Qed.
Lemma match_compOpp : forall x (B:Type) (be bl bg:B),
match CompOpp x with Eq => be | Lt => bl | Gt => bg end
= match x with Eq => be | Lt => bg | Gt => bl end.
Proof. destruct x;simpl;intros;trivial. Qed.
Lemma gen_phiZ_add : forall x y, [x + y] == [x] + [y].
Proof.
intros x y; repeat rewrite same_genZ; generalize x y;clear x y.
induction x;destruct y;simpl;norm.
apply ARgen_phiPOS_add.
apply gen_phiZ1_add_pos_neg.
rewrite gen_phiZ1_add_pos_neg. rewrite ring_add_comm.
reflexivity.
rewrite ARgen_phiPOS_add. rewrite ring_opp_add. reflexivity.
Qed.
Lemma gen_phiZ_opp : forall x, [- x] == - [x].
Proof.
intros x. repeat rewrite same_genZ. generalize x ;clear x.
induction x;simpl;norm.
rewrite ring_opp_opp. reflexivity.
Qed.
Lemma gen_phiZ_mul : forall x y, [x * y] == [x] * [y].
Proof.
intros x y;repeat rewrite same_genZ.
destruct x;destruct y;simpl;norm;
rewrite ARgen_phiPOS_mult;try (norm;fail).
rewrite ring_opp_opp ;reflexivity.
Qed.
Lemma gen_phiZ_ext : forall x y : Z, x = y -> [x] == [y].
Proof. intros;subst;reflexivity. Qed.
Declare Equivalent Keys bracket gen_phiZ.
(*proof that [.] satisfies morphism specifications*)
Global Instance gen_phiZ_morph :
(@Ring_morphism (Z:Type) R _ _ _ _ _ _ _ Zops Zr _ _ _ _ _ _ _ _ _ gen_phiZ) . (* beurk!*)
apply Build_Ring_morphism; simpl;try reflexivity.
apply gen_phiZ_add. intros. rewrite ring_sub_def.
replace (x-y)%Z with (x + (-y))%Z.
now rewrite gen_phiZ_add, gen_phiZ_opp, ring_sub_def.
reflexivity.
apply gen_phiZ_mul. apply gen_phiZ_opp. apply gen_phiZ_ext.
Defined.
End ZMORPHISM.
Instance multiplication_phi_ring{R:Type}`{Ring R} : Multiplication :=
{multiplication x y := (gen_phiZ x) * y}.
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