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Diffstat (limited to 'theories/Numbers/Cyclic/DoubleCyclic/DoubleDiv.v')
| -rw-r--r-- | theories/Numbers/Cyclic/DoubleCyclic/DoubleDiv.v | 1494 |
1 files changed, 0 insertions, 1494 deletions
diff --git a/theories/Numbers/Cyclic/DoubleCyclic/DoubleDiv.v b/theories/Numbers/Cyclic/DoubleCyclic/DoubleDiv.v deleted file mode 100644 index 09d7329b..00000000 --- a/theories/Numbers/Cyclic/DoubleCyclic/DoubleDiv.v +++ /dev/null @@ -1,1494 +0,0 @@ -(************************************************************************) -(* v * The Coq Proof Assistant / The Coq Development Team *) -(* <O___,, * INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2016 *) -(* \VV/ **************************************************************) -(* // * This file is distributed under the terms of the *) -(* * GNU Lesser General Public License Version 2.1 *) -(************************************************************************) -(* Benjamin Gregoire, Laurent Thery, INRIA, 2007 *) -(************************************************************************) - -Set Implicit Arguments. - -Require Import ZArith. -Require Import BigNumPrelude. -Require Import DoubleType. -Require Import DoubleBase. -Require Import DoubleDivn1. -Require Import DoubleAdd. -Require Import DoubleSub. - -Local Open Scope Z_scope. - -Ltac zarith := auto with zarith. - - -Section POS_MOD. - - Variable w:Type. - Variable w_0 : w. - Variable w_digits : positive. - Variable w_zdigits : w. - Variable w_WW : w -> w -> zn2z w. - Variable w_pos_mod : w -> w -> w. - Variable w_compare : w -> w -> comparison. - Variable ww_compare : zn2z w -> zn2z w -> comparison. - Variable w_0W : w -> zn2z w. - Variable low: zn2z w -> w. - Variable ww_sub: zn2z w -> zn2z w -> zn2z w. - Variable ww_zdigits : zn2z w. - - - Definition ww_pos_mod p x := - let zdigits := w_0W w_zdigits in - match x with - | W0 => W0 - | WW xh xl => - match ww_compare p zdigits with - | Eq => w_WW w_0 xl - | Lt => w_WW w_0 (w_pos_mod (low p) xl) - | Gt => - match ww_compare p ww_zdigits with - | Lt => - let n := low (ww_sub p zdigits) in - w_WW (w_pos_mod n xh) xl - | _ => x - end - end - end. - - - Variable w_to_Z : w -> Z. - - Notation wB := (base w_digits). - Notation wwB := (base (ww_digits w_digits)). - Notation "[| x |]" := (w_to_Z x) (at level 0, x at level 99). - - Notation "[[ x ]]" := (ww_to_Z w_digits w_to_Z x)(at level 0, x at level 99). - - - Variable spec_w_0 : [|w_0|] = 0. - - Variable spec_to_Z : forall x, 0 <= [|x|] < wB. - - Variable spec_to_w_Z : forall x, 0 <= [[x]] < wwB. - - Variable spec_w_WW : forall h l, [[w_WW h l]] = [|h|] * wB + [|l|]. - - Variable spec_pos_mod : forall w p, - [|w_pos_mod p w|] = [|w|] mod (2 ^ [|p|]). - - Variable spec_w_0W : forall l, [[w_0W l]] = [|l|]. - Variable spec_ww_compare : forall x y, - ww_compare x y = Z.compare [[x]] [[y]]. - Variable spec_ww_sub: forall x y, - [[ww_sub x y]] = ([[x]] - [[y]]) mod wwB. - - Variable spec_zdigits : [| w_zdigits |] = Zpos w_digits. - Variable spec_low: forall x, [| low x|] = [[x]] mod wB. - Variable spec_ww_zdigits : [[ww_zdigits]] = 2 * [|w_zdigits|]. - Variable spec_ww_digits : ww_digits w_digits = xO w_digits. - - - Hint Rewrite spec_w_0 spec_w_WW : w_rewrite. - - Lemma spec_ww_pos_mod : forall w p, - [[ww_pos_mod p w]] = [[w]] mod (2 ^ [[p]]). - assert (HHHHH:= lt_0_wB w_digits). - assert (F0: forall x y, x - y + y = x); auto with zarith. - intros w1 p; case (spec_to_w_Z p); intros HH1 HH2. - unfold ww_pos_mod; case w1. reflexivity. - intros xh xl; rewrite spec_ww_compare. - case Z.compare_spec; - rewrite spec_w_0W; rewrite spec_zdigits; fold wB; - intros H1. - rewrite H1; simpl ww_to_Z. - autorewrite with w_rewrite rm10. - rewrite Zplus_mod; auto with zarith. - rewrite Z_mod_mult; auto with zarith. - autorewrite with rm10. - rewrite Zmod_mod; auto with zarith. - rewrite Zmod_small; auto with zarith. - autorewrite with w_rewrite rm10. - simpl ww_to_Z. - rewrite spec_pos_mod. - assert (HH0: [|low p|] = [[p]]). - rewrite spec_low. - apply Zmod_small; auto with zarith. - case (spec_to_w_Z p); intros HHH1 HHH2; split; auto with zarith. - apply Z.lt_le_trans with (1 := H1). - unfold base; apply Zpower2_le_lin; auto with zarith. - rewrite HH0. - rewrite Zplus_mod; auto with zarith. - unfold base. - rewrite <- (F0 (Zpos w_digits) [[p]]). - rewrite Zpower_exp; auto with zarith. - rewrite Z.mul_assoc. - rewrite Z_mod_mult; auto with zarith. - autorewrite with w_rewrite rm10. - rewrite Zmod_mod; auto with zarith. - rewrite spec_ww_compare. - case Z.compare_spec; rewrite spec_ww_zdigits; - rewrite spec_zdigits; intros H2. - replace (2^[[p]]) with wwB. - rewrite Zmod_small; auto with zarith. - unfold base; rewrite H2. - rewrite spec_ww_digits; auto. - assert (HH0: [|low (ww_sub p (w_0W w_zdigits))|] = - [[p]] - Zpos w_digits). - rewrite spec_low. - rewrite spec_ww_sub. - rewrite spec_w_0W; rewrite spec_zdigits. - rewrite <- Zmod_div_mod; auto with zarith. - rewrite Zmod_small; auto with zarith. - split; auto with zarith. - apply Z.lt_le_trans with (Zpos w_digits); auto with zarith. - unfold base; apply Zpower2_le_lin; auto with zarith. - exists wB; unfold base; rewrite <- Zpower_exp; auto with zarith. - rewrite spec_ww_digits; - apply f_equal with (f := Z.pow 2); rewrite Pos2Z.inj_xO; auto with zarith. - simpl ww_to_Z; autorewrite with w_rewrite. - rewrite spec_pos_mod; rewrite HH0. - pattern [|xh|] at 2; - rewrite Z_div_mod_eq with (b := 2 ^ ([[p]] - Zpos w_digits)); - auto with zarith. - rewrite (fun x => (Z.mul_comm (2 ^ x))); rewrite Z.mul_add_distr_r. - unfold base; rewrite <- Z.mul_assoc; rewrite <- Zpower_exp; - auto with zarith. - rewrite F0; auto with zarith. - rewrite <- Z.add_assoc; rewrite Zplus_mod; auto with zarith. - rewrite Z_mod_mult; auto with zarith. - autorewrite with rm10. - rewrite Zmod_mod; auto with zarith. - symmetry; apply Zmod_small; auto with zarith. - case (spec_to_Z xh); intros U1 U2. - case (spec_to_Z xl); intros U3 U4. - split; auto with zarith. - apply Z.add_nonneg_nonneg; auto with zarith. - apply Z.mul_nonneg_nonneg; auto with zarith. - match goal with |- 0 <= ?X mod ?Y => - case (Z_mod_lt X Y); auto with zarith - end. - match goal with |- ?X mod ?Y * ?U + ?Z < ?T => - apply Z.le_lt_trans with ((Y - 1) * U + Z ); - [case (Z_mod_lt X Y); auto with zarith | idtac] - end. - match goal with |- ?X * ?U + ?Y < ?Z => - apply Z.le_lt_trans with (X * U + (U - 1)) - end. - apply Z.add_le_mono_l; auto with zarith. - case (spec_to_Z xl); unfold base; auto with zarith. - rewrite Z.mul_sub_distr_r; rewrite <- Zpower_exp; auto with zarith. - rewrite F0; auto with zarith. - rewrite Zmod_small; auto with zarith. - case (spec_to_w_Z (WW xh xl)); intros U1 U2. - split; auto with zarith. - apply Z.lt_le_trans with (1:= U2). - unfold base; rewrite spec_ww_digits. - apply Zpower_le_monotone; auto with zarith. - split; auto with zarith. - rewrite Pos2Z.inj_xO; auto with zarith. - Qed. - -End POS_MOD. - -Section DoubleDiv32. - - Variable w : Type. - Variable w_0 : w. - Variable w_Bm1 : w. - Variable w_Bm2 : w. - Variable w_WW : w -> w -> zn2z w. - Variable w_compare : w -> w -> comparison. - Variable w_add_c : w -> w -> carry w. - Variable w_add_carry_c : w -> w -> carry w. - Variable w_add : w -> w -> w. - Variable w_add_carry : w -> w -> w. - Variable w_pred : w -> w. - Variable w_sub : w -> w -> w. - Variable w_mul_c : w -> w -> zn2z w. - Variable w_div21 : w -> w -> w -> w*w. - Variable ww_sub_c : zn2z w -> zn2z w -> carry (zn2z w). - - Definition w_div32_body a1 a2 a3 b1 b2 := - match w_compare a1 b1 with - | Lt => - let (q,r) := w_div21 a1 a2 b1 in - match ww_sub_c (w_WW r a3) (w_mul_c q b2) with - | C0 r1 => (q,r1) - | C1 r1 => - let q := w_pred q in - ww_add_c_cont w_WW w_add_c w_add_carry_c - (fun r2=>(w_pred q, ww_add w_add_c w_add w_add_carry r2 (WW b1 b2))) - (fun r2 => (q,r2)) - r1 (WW b1 b2) - end - | Eq => - ww_add_c_cont w_WW w_add_c w_add_carry_c - (fun r => (w_Bm2, ww_add w_add_c w_add w_add_carry r (WW b1 b2))) - (fun r => (w_Bm1,r)) - (WW (w_sub a2 b2) a3) (WW b1 b2) - | Gt => (w_0, W0) (* cas absurde *) - end. - - Definition w_div32 a1 a2 a3 b1 b2 := - Eval lazy beta iota delta [ww_add_c_cont ww_add w_div32_body] in - w_div32_body a1 a2 a3 b1 b2. - - (* Proof *) - - Variable w_digits : positive. - Variable w_to_Z : w -> Z. - - Notation wB := (base w_digits). - Notation wwB := (base (ww_digits w_digits)). - Notation "[| x |]" := (w_to_Z x) (at level 0, x at level 99). - Notation "[+| c |]" := - (interp_carry 1 wB w_to_Z c) (at level 0, c at level 99). - Notation "[-| c |]" := - (interp_carry (-1) wB w_to_Z c) (at level 0, c at level 99). - - Notation "[[ x ]]" := (ww_to_Z w_digits w_to_Z x)(at level 0, x at level 99). - Notation "[-[ c ]]" := - (interp_carry (-1) wwB (ww_to_Z w_digits w_to_Z) c) - (at level 0, c at level 99). - - - Variable spec_w_0 : [|w_0|] = 0. - Variable spec_w_Bm1 : [|w_Bm1|] = wB - 1. - Variable spec_w_Bm2 : [|w_Bm2|] = wB - 2. - - Variable spec_to_Z : forall x, 0 <= [|x|] < wB. - - Variable spec_w_WW : forall h l, [[w_WW h l]] = [|h|] * wB + [|l|]. - Variable spec_compare : - forall x y, w_compare x y = Z.compare [|x|] [|y|]. - Variable spec_w_add_c : forall x y, [+|w_add_c x y|] = [|x|] + [|y|]. - Variable spec_w_add_carry_c : - forall x y, [+|w_add_carry_c x y|] = [|x|] + [|y|] + 1. - - Variable spec_w_add : forall x y, [|w_add x y|] = ([|x|] + [|y|]) mod wB. - Variable spec_w_add_carry : - forall x y, [|w_add_carry x y|] = ([|x|] + [|y|] + 1) mod wB. - - Variable spec_pred : forall x, [|w_pred x|] = ([|x|] - 1) mod wB. - Variable spec_sub : forall x y, [|w_sub x y|] = ([|x|] - [|y|]) mod wB. - - Variable spec_mul_c : forall x y, [[ w_mul_c x y ]] = [|x|] * [|y|]. - Variable spec_div21 : forall a1 a2 b, - wB/2 <= [|b|] -> - [|a1|] < [|b|] -> - let (q,r) := w_div21 a1 a2 b in - [|a1|] *wB+ [|a2|] = [|q|] * [|b|] + [|r|] /\ - 0 <= [|r|] < [|b|]. - - Variable spec_ww_sub_c : forall x y, [-[ww_sub_c x y]] = [[x]] - [[y]]. - - Ltac Spec_w_to_Z x := - let H:= fresh "HH" in - assert (H:= spec_to_Z x). - Ltac Spec_ww_to_Z x := - let H:= fresh "HH" in - assert (H:= spec_ww_to_Z w_digits w_to_Z spec_to_Z x). - - Theorem wB_div2: forall x, wB/2 <= x -> wB <= 2 * x. - intros x H; rewrite <- wB_div_2; apply Z.mul_le_mono_nonneg_l; auto with zarith. - Qed. - - Lemma Zmult_lt_0_reg_r_2 : forall n m : Z, 0 <= n -> 0 < m * n -> 0 < m. - Proof. - intros n m H1 H2;apply Z.mul_pos_cancel_r with n;trivial. - Z.le_elim H1; trivial. - subst;rewrite Z.mul_0_r in H2;discriminate H2. - Qed. - - Theorem spec_w_div32 : forall a1 a2 a3 b1 b2, - wB/2 <= [|b1|] -> - [[WW a1 a2]] < [[WW b1 b2]] -> - let (q,r) := w_div32 a1 a2 a3 b1 b2 in - [|a1|] * wwB + [|a2|] * wB + [|a3|] = - [|q|] * ([|b1|] * wB + [|b2|]) + [[r]] /\ - 0 <= [[r]] < [|b1|] * wB + [|b2|]. - Proof. - intros a1 a2 a3 b1 b2 Hle Hlt. - assert (U:= lt_0_wB w_digits); assert (U1:= lt_0_wwB w_digits). - Spec_w_to_Z a1;Spec_w_to_Z a2;Spec_w_to_Z a3;Spec_w_to_Z b1;Spec_w_to_Z b2. - rewrite wwB_wBwB; rewrite Z.pow_2_r; rewrite Z.mul_assoc;rewrite <- Z.mul_add_distr_r. - change (w_div32 a1 a2 a3 b1 b2) with (w_div32_body a1 a2 a3 b1 b2). - unfold w_div32_body. - rewrite spec_compare. case Z.compare_spec; intro Hcmp. - simpl in Hlt. - rewrite Hcmp in Hlt;assert ([|a2|] < [|b2|]). omega. - assert ([[WW (w_sub a2 b2) a3]] = ([|a2|]-[|b2|])*wB + [|a3|] + wwB). - simpl;rewrite spec_sub. - assert ([|a2|] - [|b2|] = wB*(-1) + ([|a2|] - [|b2|] + wB)). ring. - assert (0 <= [|a2|] - [|b2|] + wB < wB). omega. - rewrite <-(Zmod_unique ([|a2|]-[|b2|]) wB (-1) ([|a2|]-[|b2|]+wB) H1 H0). - rewrite wwB_wBwB;ring. - assert (U2 := wB_pos w_digits). - eapply spec_ww_add_c_cont with (P := - fun (x y:zn2z w) (res:w*zn2z w) => - let (q, r) := res in - ([|a1|] * wB + [|a2|]) * wB + [|a3|] = - [|q|] * ([|b1|] * wB + [|b2|]) + [[r]] /\ - 0 <= [[r]] < [|b1|] * wB + [|b2|]);eauto. - rewrite H0;intros r. - repeat - (rewrite spec_ww_add;eauto || rewrite spec_w_Bm1 || rewrite spec_w_Bm2); - simpl ww_to_Z;try rewrite Z.mul_1_l;intros H1. - assert (0<= ([[r]] + ([|b1|] * wB + [|b2|])) - wwB < [|b1|] * wB + [|b2|]). - Spec_ww_to_Z r;split;zarith. - rewrite H1. - assert (H12:= wB_div2 Hle). assert (wwB <= 2 * [|b1|] * wB). - rewrite wwB_wBwB; rewrite Z.pow_2_r; zarith. - assert (-wwB < ([|a2|] - [|b2|]) * wB + [|a3|] < 0). - split. apply Z.lt_le_trans with (([|a2|] - [|b2|]) * wB);zarith. - rewrite wwB_wBwB;replace (-(wB^2)) with (-wB*wB);[zarith | ring]. - apply Z.mul_lt_mono_pos_r;zarith. - apply Z.le_lt_trans with (([|a2|] - [|b2|]) * wB + (wB -1));zarith. - replace ( ([|a2|] - [|b2|]) * wB + (wB - 1)) with - (([|a2|] - [|b2|] + 1) * wB + - 1);[zarith | ring]. - assert (([|a2|] - [|b2|] + 1) * wB <= 0);zarith. - replace 0 with (0*wB);zarith. - replace (([|a2|] - [|b2|]) * wB + [|a3|] + wwB + ([|b1|] * wB + [|b2|]) + - ([|b1|] * wB + [|b2|]) - wwB) with - (([|a2|] - [|b2|]) * wB + [|a3|] + 2*[|b1|] * wB + 2*[|b2|]); - [zarith | ring]. - rewrite <- (Zmod_unique ([[r]] + ([|b1|] * wB + [|b2|])) wwB - 1 ([[r]] + ([|b1|] * wB + [|b2|]) - wwB));zarith;try (ring;fail). - split. rewrite H1;rewrite Hcmp;ring. trivial. - Spec_ww_to_Z (WW b1 b2). simpl in HH4;zarith. - rewrite H0;intros r;repeat - (rewrite spec_w_Bm1 || rewrite spec_w_Bm2); - simpl ww_to_Z;try rewrite Z.mul_1_l;intros H1. - assert ([[r]]=([|a2|]-[|b2|])*wB+[|a3|]+([|b1|]*wB+[|b2|])). zarith. - split. rewrite H2;rewrite Hcmp;ring. - split. Spec_ww_to_Z r;zarith. - rewrite H2. - assert (([|a2|] - [|b2|]) * wB + [|a3|] < 0);zarith. - apply Z.le_lt_trans with (([|a2|] - [|b2|]) * wB + (wB -1));zarith. - replace ( ([|a2|] - [|b2|]) * wB + (wB - 1)) with - (([|a2|] - [|b2|] + 1) * wB + - 1);[zarith|ring]. - assert (([|a2|] - [|b2|] + 1) * wB <= 0);zarith. - replace 0 with (0*wB);zarith. - (* Cas Lt *) - assert (Hdiv21 := spec_div21 a2 Hle Hcmp); - destruct (w_div21 a1 a2 b1) as (q, r);destruct Hdiv21. - rewrite H. - assert (Hq := spec_to_Z q). - generalize - (spec_ww_sub_c (w_WW r a3) (w_mul_c q b2)); - destruct (ww_sub_c (w_WW r a3) (w_mul_c q b2)) - as [r1|r1];repeat (rewrite spec_w_WW || rewrite spec_mul_c); - unfold interp_carry;intros H1. - rewrite H1. - split. ring. split. - rewrite <- H1;destruct (spec_ww_to_Z w_digits w_to_Z spec_to_Z r1);trivial. - apply Z.le_lt_trans with ([|r|] * wB + [|a3|]). - assert ( 0 <= [|q|] * [|b2|]);zarith. - apply beta_lex_inv;zarith. - assert ([[r1]] = [|r|] * wB + [|a3|] - [|q|] * [|b2|] + wwB). - rewrite <- H1;ring. - Spec_ww_to_Z r1; assert (0 <= [|r|]*wB). zarith. - assert (0 < [|q|] * [|b2|]). zarith. - assert (0 < [|q|]). - apply Zmult_lt_0_reg_r_2 with [|b2|];zarith. - eapply spec_ww_add_c_cont with (P := - fun (x y:zn2z w) (res:w*zn2z w) => - let (q0, r0) := res in - ([|q|] * [|b1|] + [|r|]) * wB + [|a3|] = - [|q0|] * ([|b1|] * wB + [|b2|]) + [[r0]] /\ - 0 <= [[r0]] < [|b1|] * wB + [|b2|]);eauto. - intros r2;repeat (rewrite spec_pred || rewrite spec_ww_add;eauto); - simpl ww_to_Z;intros H7. - assert (0 < [|q|] - 1). - assert (H6 : 1 <= [|q|]) by zarith. - Z.le_elim H6;zarith. - rewrite <- H6 in H2;rewrite H2 in H7. - assert (0 < [|b1|]*wB). apply Z.mul_pos_pos;zarith. - Spec_ww_to_Z r2. zarith. - rewrite (Zmod_small ([|q|] -1));zarith. - rewrite (Zmod_small ([|q|] -1 -1));zarith. - assert ([[r2]] + ([|b1|] * wB + [|b2|]) = - wwB * 1 + - ([|r|] * wB + [|a3|] - [|q|] * [|b2|] + 2 * ([|b1|] * wB + [|b2|]))). - rewrite H7;rewrite H2;ring. - assert - ([|r|]*wB + [|a3|] - [|q|]*[|b2|] + 2 * ([|b1|]*wB + [|b2|]) - < [|b1|]*wB + [|b2|]). - Spec_ww_to_Z r2;omega. - Spec_ww_to_Z (WW b1 b2). simpl in HH5. - assert - (0 <= [|r|]*wB + [|a3|] - [|q|]*[|b2|] + 2 * ([|b1|]*wB + [|b2|]) - < wwB). split;try omega. - replace (2*([|b1|]*wB+[|b2|])) with ((2*[|b1|])*wB+2*[|b2|]). 2:ring. - assert (H12:= wB_div2 Hle). assert (wwB <= 2 * [|b1|] * wB). - rewrite wwB_wBwB; rewrite Z.pow_2_r; zarith. omega. - rewrite <- (Zmod_unique - ([[r2]] + ([|b1|] * wB + [|b2|])) - wwB - 1 - ([|r|] * wB + [|a3|] - [|q|] * [|b2|] + 2*([|b1|] * wB + [|b2|])) - H10 H8). - split. ring. zarith. - intros r2;repeat (rewrite spec_pred);simpl ww_to_Z;intros H7. - rewrite (Zmod_small ([|q|] -1));zarith. - split. - replace [[r2]] with ([[r1]] + ([|b1|] * wB + [|b2|]) -wwB). - rewrite H2; ring. rewrite <- H7; ring. - Spec_ww_to_Z r2;Spec_ww_to_Z r1. omega. - simpl in Hlt. - assert ([|a1|] * wB + [|a2|] <= [|b1|] * wB + [|b2|]). zarith. - assert (H1 := beta_lex _ _ _ _ _ H HH0 HH3). rewrite spec_w_0;simpl;zarith. - Qed. - - -End DoubleDiv32. - -Section DoubleDiv21. - Variable w : Type. - Variable w_0 : w. - - Variable w_0W : w -> zn2z w. - Variable w_div32 : w -> w -> w -> w -> w -> w * zn2z w. - - Variable ww_1 : zn2z w. - Variable ww_compare : zn2z w -> zn2z w -> comparison. - Variable ww_sub : zn2z w -> zn2z w -> zn2z w. - - - Definition ww_div21 a1 a2 b := - match a1 with - | W0 => - match ww_compare a2 b with - | Gt => (ww_1, ww_sub a2 b) - | Eq => (ww_1, W0) - | Lt => (W0, a2) - end - | WW a1h a1l => - match a2 with - | W0 => - match b with - | W0 => (W0,W0) (* cas absurde *) - | WW b1 b2 => - let (q1, r) := w_div32 a1h a1l w_0 b1 b2 in - match r with - | W0 => (WW q1 w_0, W0) - | WW r1 r2 => - let (q2, s) := w_div32 r1 r2 w_0 b1 b2 in - (WW q1 q2, s) - end - end - | WW a2h a2l => - match b with - | W0 => (W0,W0) (* cas absurde *) - | WW b1 b2 => - let (q1, r) := w_div32 a1h a1l a2h b1 b2 in - match r with - | W0 => (WW q1 w_0, w_0W a2l) - | WW r1 r2 => - let (q2, s) := w_div32 r1 r2 a2l b1 b2 in - (WW q1 q2, s) - end - end - end - end. - - (* Proof *) - - Variable w_digits : positive. - Variable w_to_Z : w -> Z. - Notation wB := (base w_digits). - Notation wwB := (base (ww_digits w_digits)). - Notation "[| x |]" := (w_to_Z x) (at level 0, x at level 99). - Notation "[[ x ]]" := (ww_to_Z w_digits w_to_Z x)(at level 0, x at level 99). - Notation "[-[ c ]]" := - (interp_carry (-1) wwB (ww_to_Z w_digits w_to_Z) c) - (at level 0, c at level 99). - - Variable spec_w_0 : [|w_0|] = 0. - Variable spec_to_Z : forall x, 0 <= [|x|] < wB. - Variable spec_w_0W : forall l, [[w_0W l]] = [|l|]. - Variable spec_w_div32 : forall a1 a2 a3 b1 b2, - wB/2 <= [|b1|] -> - [[WW a1 a2]] < [[WW b1 b2]] -> - let (q,r) := w_div32 a1 a2 a3 b1 b2 in - [|a1|] * wwB + [|a2|] * wB + [|a3|] = - [|q|] * ([|b1|] * wB + [|b2|]) + [[r]] /\ - 0 <= [[r]] < [|b1|] * wB + [|b2|]. - Variable spec_ww_1 : [[ww_1]] = 1. - Variable spec_ww_compare : forall x y, - ww_compare x y = Z.compare [[x]] [[y]]. - Variable spec_ww_sub : forall x y, [[ww_sub x y]] = ([[x]] - [[y]]) mod wwB. - - Theorem wwB_div: wwB = 2 * (wwB / 2). - Proof. - rewrite wwB_div_2; rewrite Z.mul_assoc; rewrite wB_div_2; auto. - rewrite <- Z.pow_2_r; apply wwB_wBwB. - Qed. - - Ltac Spec_w_to_Z x := - let H:= fresh "HH" in - assert (H:= spec_to_Z x). - Ltac Spec_ww_to_Z x := - let H:= fresh "HH" in - assert (H:= spec_ww_to_Z w_digits w_to_Z spec_to_Z x). - - Theorem spec_ww_div21 : forall a1 a2 b, - wwB/2 <= [[b]] -> - [[a1]] < [[b]] -> - let (q,r) := ww_div21 a1 a2 b in - [[a1]] *wwB+[[a2]] = [[q]] * [[b]] + [[r]] /\ 0 <= [[r]] < [[b]]. - Proof. - assert (U:= lt_0_wB w_digits). - assert (U1:= lt_0_wwB w_digits). - intros a1 a2 b H Hlt; unfold ww_div21. - Spec_ww_to_Z b; assert (Eq: 0 < [[b]]). Spec_ww_to_Z a1;omega. - generalize Hlt H ;clear Hlt H;case a1. - intros H1 H2;simpl in H1;Spec_ww_to_Z a2. - rewrite spec_ww_compare. case Z.compare_spec; - simpl;try rewrite spec_ww_1;autorewrite with rm10; intros;zarith. - rewrite spec_ww_sub;simpl. rewrite Zmod_small;zarith. - split. ring. - assert (wwB <= 2*[[b]]);zarith. - rewrite wwB_div;zarith. - intros a1h a1l. Spec_w_to_Z a1h;Spec_w_to_Z a1l. Spec_ww_to_Z a2. - destruct a2 as [ |a3 a4]; - (destruct b as [ |b1 b2];[unfold Z.le in Eq;discriminate Eq|idtac]); - try (Spec_w_to_Z a3; Spec_w_to_Z a4); Spec_w_to_Z b1; Spec_w_to_Z b2; - intros Hlt H; match goal with |-context [w_div32 ?X ?Y ?Z ?T ?U] => - generalize (@spec_w_div32 X Y Z T U); case (w_div32 X Y Z T U); - intros q1 r H0 - end; (assert (Eq1: wB / 2 <= [|b1|]);[ - apply (@beta_lex (wB / 2) 0 [|b1|] [|b2|] wB); auto with zarith; - autorewrite with rm10;repeat rewrite (Z.mul_comm wB); - rewrite <- wwB_div_2; trivial - | generalize (H0 Eq1 Hlt);clear H0;destruct r as [ |r1 r2];simpl; - try rewrite spec_w_0; try rewrite spec_w_0W;repeat rewrite Z.add_0_r; - intros (H1,H2) ]). - split;[rewrite wwB_wBwB; rewrite Z.pow_2_r | trivial]. - rewrite Z.mul_assoc;rewrite Z.mul_add_distr_r;rewrite <- Z.mul_assoc; - rewrite <- Z.pow_2_r; rewrite <- wwB_wBwB;rewrite H1;ring. - destruct H2 as (H2,H3);match goal with |-context [w_div32 ?X ?Y ?Z ?T ?U] => - generalize (@spec_w_div32 X Y Z T U); case (w_div32 X Y Z T U); - intros q r H0;generalize (H0 Eq1 H3);clear H0;intros (H4,H5) end. - split;[rewrite wwB_wBwB | trivial]. - rewrite Z.pow_2_r. - rewrite Z.mul_assoc;rewrite Z.mul_add_distr_r;rewrite <- Z.mul_assoc; - rewrite <- Z.pow_2_r. - rewrite <- wwB_wBwB;rewrite H1. - rewrite spec_w_0 in H4;rewrite Z.add_0_r in H4. - repeat rewrite Z.mul_add_distr_r. rewrite <- (Z.mul_assoc [|r1|]). - rewrite <- Z.pow_2_r; rewrite <- wwB_wBwB;rewrite H4;simpl;ring. - split;[rewrite wwB_wBwB | split;zarith]. - replace (([|a1h|] * wB + [|a1l|]) * wB^2 + ([|a3|] * wB + [|a4|])) - with (([|a1h|] * wwB + [|a1l|] * wB + [|a3|])*wB+ [|a4|]). - rewrite H1;ring. rewrite wwB_wBwB;ring. - change [|a4|] with (0*wB+[|a4|]);apply beta_lex_inv;zarith. - assert (1 <= wB/2);zarith. - assert (H_:= wB_pos w_digits);apply Zdiv_le_lower_bound;zarith. - destruct H2 as (H2,H3);match goal with |-context [w_div32 ?X ?Y ?Z ?T ?U] => - generalize (@spec_w_div32 X Y Z T U); case (w_div32 X Y Z T U); - intros q r H0;generalize (H0 Eq1 H3);clear H0;intros (H4,H5) end. - split;trivial. - replace (([|a1h|] * wB + [|a1l|]) * wwB + ([|a3|] * wB + [|a4|])) with - (([|a1h|] * wwB + [|a1l|] * wB + [|a3|])*wB + [|a4|]); - [rewrite H1 | rewrite wwB_wBwB;ring]. - replace (([|q1|]*([|b1|]*wB+[|b2|])+([|r1|]*wB+[|r2|]))*wB+[|a4|]) with - (([|q1|]*([|b1|]*wB+[|b2|]))*wB+([|r1|]*wwB+[|r2|]*wB+[|a4|])); - [rewrite H4;simpl|rewrite wwB_wBwB];ring. - Qed. - -End DoubleDiv21. - -Section DoubleDivGt. - Variable w : Type. - Variable w_digits : positive. - Variable w_0 : w. - - Variable w_WW : w -> w -> zn2z w. - Variable w_0W : w -> zn2z w. - Variable w_compare : w -> w -> comparison. - Variable w_eq0 : w -> bool. - Variable w_opp_c : w -> carry w. - Variable w_opp w_opp_carry : w -> w. - Variable w_sub_c : w -> w -> carry w. - Variable w_sub w_sub_carry : w -> w -> w. - - Variable w_div_gt : w -> w -> w*w. - Variable w_mod_gt : w -> w -> w. - Variable w_gcd_gt : w -> w -> w. - Variable w_add_mul_div : w -> w -> w -> w. - Variable w_head0 : w -> w. - Variable w_div21 : w -> w -> w -> w * w. - Variable w_div32 : w -> w -> w -> w -> w -> w * zn2z w. - - - Variable _ww_zdigits : zn2z w. - Variable ww_1 : zn2z w. - Variable ww_add_mul_div : zn2z w -> zn2z w -> zn2z w -> zn2z w. - - Variable w_zdigits : w. - - Definition ww_div_gt_aux ah al bh bl := - Eval lazy beta iota delta [ww_sub ww_opp] in - let p := w_head0 bh in - match w_compare p w_0 with - | Gt => - let b1 := w_add_mul_div p bh bl in - let b2 := w_add_mul_div p bl w_0 in - let a1 := w_add_mul_div p w_0 ah in - let a2 := w_add_mul_div p ah al in - let a3 := w_add_mul_div p al w_0 in - let (q,r) := w_div32 a1 a2 a3 b1 b2 in - (WW w_0 q, ww_add_mul_div - (ww_sub w_0 w_WW w_opp_c w_opp_carry w_sub_c - w_opp w_sub w_sub_carry _ww_zdigits (w_0W p)) W0 r) - | _ => (ww_1, ww_sub w_0 w_WW w_opp_c w_opp_carry w_sub_c - w_opp w_sub w_sub_carry (WW ah al) (WW bh bl)) - end. - - Definition ww_div_gt a b := - Eval lazy beta iota delta [ww_div_gt_aux double_divn1 - double_divn1_p double_divn1_p_aux double_divn1_0 double_divn1_0_aux - double_split double_0 double_WW] in - match a, b with - | W0, _ => (W0,W0) - | _, W0 => (W0,W0) - | WW ah al, WW bh bl => - if w_eq0 ah then - let (q,r) := w_div_gt al bl in - (WW w_0 q, w_0W r) - else - match w_compare w_0 bh with - | Eq => - let(q,r):= - double_divn1 w_zdigits w_0 w_WW w_head0 w_add_mul_div w_div21 - w_compare w_sub 1 a bl in - (q, w_0W r) - | Lt => ww_div_gt_aux ah al bh bl - | Gt => (W0,W0) (* cas absurde *) - end - end. - - Definition ww_mod_gt_aux ah al bh bl := - Eval lazy beta iota delta [ww_sub ww_opp] in - let p := w_head0 bh in - match w_compare p w_0 with - | Gt => - let b1 := w_add_mul_div p bh bl in - let b2 := w_add_mul_div p bl w_0 in - let a1 := w_add_mul_div p w_0 ah in - let a2 := w_add_mul_div p ah al in - let a3 := w_add_mul_div p al w_0 in - let (q,r) := w_div32 a1 a2 a3 b1 b2 in - ww_add_mul_div (ww_sub w_0 w_WW w_opp_c w_opp_carry w_sub_c - w_opp w_sub w_sub_carry _ww_zdigits (w_0W p)) W0 r - | _ => - ww_sub w_0 w_WW w_opp_c w_opp_carry w_sub_c - w_opp w_sub w_sub_carry (WW ah al) (WW bh bl) - end. - - Definition ww_mod_gt a b := - Eval lazy beta iota delta [ww_mod_gt_aux double_modn1 - double_modn1_p double_modn1_p_aux double_modn1_0 double_modn1_0_aux - double_split double_0 double_WW snd] in - match a, b with - | W0, _ => W0 - | _, W0 => W0 - | WW ah al, WW bh bl => - if w_eq0 ah then w_0W (w_mod_gt al bl) - else - match w_compare w_0 bh with - | Eq => - w_0W (double_modn1 w_zdigits w_0 w_head0 w_add_mul_div w_div21 - w_compare w_sub 1 a bl) - | Lt => ww_mod_gt_aux ah al bh bl - | Gt => W0 (* cas absurde *) - end - end. - - Definition ww_gcd_gt_body (cont: w->w->w->w->zn2z w) (ah al bh bl: w) := - Eval lazy beta iota delta [ww_mod_gt_aux double_modn1 - double_modn1_p double_modn1_p_aux double_modn1_0 double_modn1_0_aux - double_split double_0 double_WW snd] in - match w_compare w_0 bh with - | Eq => - match w_compare w_0 bl with - | Eq => WW ah al (* normalement n'arrive pas si forme normale *) - | Lt => - let m := double_modn1 w_zdigits w_0 w_head0 w_add_mul_div w_div21 - w_compare w_sub 1 (WW ah al) bl in - WW w_0 (w_gcd_gt bl m) - | Gt => W0 (* absurde *) - end - | Lt => - let m := ww_mod_gt_aux ah al bh bl in - match m with - | W0 => WW bh bl - | WW mh ml => - match w_compare w_0 mh with - | Eq => - match w_compare w_0 ml with - | Eq => WW bh bl - | _ => - let r := double_modn1 w_zdigits w_0 w_head0 w_add_mul_div w_div21 - w_compare w_sub 1 (WW bh bl) ml in - WW w_0 (w_gcd_gt ml r) - end - | Lt => - let r := ww_mod_gt_aux bh bl mh ml in - match r with - | W0 => m - | WW rh rl => cont mh ml rh rl - end - | Gt => W0 (* absurde *) - end - end - | Gt => W0 (* absurde *) - end. - - Fixpoint ww_gcd_gt_aux - (p:positive) (cont: w -> w -> w -> w -> zn2z w) (ah al bh bl : w) - {struct p} : zn2z w := - ww_gcd_gt_body - (fun mh ml rh rl => match p with - | xH => cont mh ml rh rl - | xO p => ww_gcd_gt_aux p (ww_gcd_gt_aux p cont) mh ml rh rl - | xI p => ww_gcd_gt_aux p (ww_gcd_gt_aux p cont) mh ml rh rl - end) ah al bh bl. - - - (* Proof *) - - Variable w_to_Z : w -> Z. - Notation wB := (base w_digits). - Notation wwB := (base (ww_digits w_digits)). - Notation "[| x |]" := (w_to_Z x) (at level 0, x at level 99). - Notation "[-| c |]" := - (interp_carry (-1) wB w_to_Z c) (at level 0, c at level 99). - - Notation "[[ x ]]" := (ww_to_Z w_digits w_to_Z x)(at level 0, x at level 99). - - Variable spec_w_0 : [|w_0|] = 0. - Variable spec_to_Z : forall x, 0 <= [|x|] < wB. - Variable spec_to_w_Z : forall x, 0 <= [[x]] < wwB. - - Variable spec_w_WW : forall h l, [[w_WW h l]] = [|h|] * wB + [|l|]. - Variable spec_w_0W : forall l, [[w_0W l]] = [|l|]. - Variable spec_compare : - forall x y, w_compare x y = Z.compare [|x|] [|y|]. - Variable spec_eq0 : forall x, w_eq0 x = true -> [|x|] = 0. - - Variable spec_opp_c : forall x, [-|w_opp_c x|] = -[|x|]. - Variable spec_opp : forall x, [|w_opp x|] = (-[|x|]) mod wB. - Variable spec_opp_carry : forall x, [|w_opp_carry x|] = wB - [|x|] - 1. - - Variable spec_sub_c : forall x y, [-|w_sub_c x y|] = [|x|] - [|y|]. - Variable spec_sub : forall x y, [|w_sub x y|] = ([|x|] - [|y|]) mod wB. - Variable spec_sub_carry : - forall x y, [|w_sub_carry x y|] = ([|x|] - [|y|] - 1) mod wB. - - Variable spec_div_gt : forall a b, [|a|] > [|b|] -> 0 < [|b|] -> - let (q,r) := w_div_gt a b in - [|a|] = [|q|] * [|b|] + [|r|] /\ - 0 <= [|r|] < [|b|]. - Variable spec_mod_gt : forall a b, [|a|] > [|b|] -> 0 < [|b|] -> - [|w_mod_gt a b|] = [|a|] mod [|b|]. - Variable spec_gcd_gt : forall a b, [|a|] > [|b|] -> - Zis_gcd [|a|] [|b|] [|w_gcd_gt a b|]. - - Variable spec_add_mul_div : forall x y p, - [|p|] <= Zpos w_digits -> - [| w_add_mul_div p x y |] = - ([|x|] * (2 ^ ([|p|])) + - [|y|] / (2 ^ ((Zpos w_digits) - [|p|]))) mod wB. - Variable spec_head0 : forall x, 0 < [|x|] -> - wB/ 2 <= 2 ^ [|w_head0 x|] * [|x|] < wB. - - Variable spec_div21 : forall a1 a2 b, - wB/2 <= [|b|] -> - [|a1|] < [|b|] -> - let (q,r) := w_div21 a1 a2 b in - [|a1|] *wB+ [|a2|] = [|q|] * [|b|] + [|r|] /\ - 0 <= [|r|] < [|b|]. - - Variable spec_w_div32 : forall a1 a2 a3 b1 b2, - wB/2 <= [|b1|] -> - [[WW a1 a2]] < [[WW b1 b2]] -> - let (q,r) := w_div32 a1 a2 a3 b1 b2 in - [|a1|] * wwB + [|a2|] * wB + [|a3|] = - [|q|] * ([|b1|] * wB + [|b2|]) + [[r]] /\ - 0 <= [[r]] < [|b1|] * wB + [|b2|]. - - Variable spec_w_zdigits: [|w_zdigits|] = Zpos w_digits. - - Variable spec_ww_digits_ : [[_ww_zdigits]] = Zpos (xO w_digits). - Variable spec_ww_1 : [[ww_1]] = 1. - Variable spec_ww_add_mul_div : forall x y p, - [[p]] <= Zpos (xO w_digits) -> - [[ ww_add_mul_div p x y ]] = - ([[x]] * (2^[[p]]) + - [[y]] / (2^(Zpos (xO w_digits) - [[p]]))) mod wwB. - - Ltac Spec_w_to_Z x := - let H:= fresh "HH" in - assert (H:= spec_to_Z x). - - Ltac Spec_ww_to_Z x := - let H:= fresh "HH" in - assert (H:= spec_ww_to_Z w_digits w_to_Z spec_to_Z x). - - Lemma to_Z_div_minus_p : forall x p, - 0 < [|p|] < Zpos w_digits -> - 0 <= [|x|] / 2 ^ (Zpos w_digits - [|p|]) < 2 ^ [|p|]. - Proof. - intros x p H;Spec_w_to_Z x. - split. apply Zdiv_le_lower_bound;zarith. - apply Zdiv_lt_upper_bound;zarith. - rewrite <- Zpower_exp;zarith. - ring_simplify ([|p|] + (Zpos w_digits - [|p|])); unfold base in HH;zarith. - Qed. - Hint Resolve to_Z_div_minus_p : zarith. - - Lemma spec_ww_div_gt_aux : forall ah al bh bl, - [[WW ah al]] > [[WW bh bl]] -> - 0 < [|bh|] -> - let (q,r) := ww_div_gt_aux ah al bh bl in - [[WW ah al]] = [[q]] * [[WW bh bl]] + [[r]] /\ - 0 <= [[r]] < [[WW bh bl]]. - Proof. - intros ah al bh bl Hgt Hpos;unfold ww_div_gt_aux. - change - (let (q, r) := let p := w_head0 bh in - match w_compare p w_0 with - | Gt => - let b1 := w_add_mul_div p bh bl in - let b2 := w_add_mul_div p bl w_0 in - let a1 := w_add_mul_div p w_0 ah in - let a2 := w_add_mul_div p ah al in - let a3 := w_add_mul_div p al w_0 in - let (q,r) := w_div32 a1 a2 a3 b1 b2 in - (WW w_0 q, ww_add_mul_div - (ww_sub w_0 w_WW w_opp_c w_opp_carry w_sub_c - w_opp w_sub w_sub_carry _ww_zdigits (w_0W p)) W0 r) - | _ => (ww_1, ww_sub w_0 w_WW w_opp_c w_opp_carry w_sub_c - w_opp w_sub w_sub_carry (WW ah al) (WW bh bl)) - end in [[WW ah al]]=[[q]]*[[WW bh bl]]+[[r]] /\ 0 <=[[r]]< [[WW bh bl]]). - assert (Hh := spec_head0 Hpos). - lazy zeta. - rewrite spec_compare; case Z.compare_spec; - rewrite spec_w_0; intros HH. - generalize Hh; rewrite HH; simpl Z.pow; - rewrite Z.mul_1_l; intros (HH1, HH2); clear HH. - assert (wwB <= 2*[[WW bh bl]]). - apply Z.le_trans with (2*[|bh|]*wB). - rewrite wwB_wBwB; rewrite Z.pow_2_r; apply Z.mul_le_mono_nonneg_r; zarith. - rewrite <- wB_div_2; apply Z.mul_le_mono_nonneg_l; zarith. - simpl ww_to_Z;rewrite Z.mul_add_distr_l;rewrite Z.mul_assoc. - Spec_w_to_Z bl;zarith. - Spec_ww_to_Z (WW ah al). - rewrite spec_ww_sub;eauto. - simpl;rewrite spec_ww_1;rewrite Z.mul_1_l;simpl. - simpl ww_to_Z in Hgt, H, HH;rewrite Zmod_small;split;zarith. - case (spec_to_Z (w_head0 bh)); auto with zarith. - assert ([|w_head0 bh|] < Zpos w_digits). - destruct (Z_lt_ge_dec [|w_head0 bh|] (Zpos w_digits));trivial. - exfalso. - assert (2 ^ [|w_head0 bh|] * [|bh|] >= wB);auto with zarith. - apply Z.le_ge; replace wB with (wB * 1);try ring. - Spec_w_to_Z bh;apply Z.mul_le_mono_nonneg;zarith. - unfold base;apply Zpower_le_monotone;zarith. - assert (HHHH : 0 < [|w_head0 bh|] < Zpos w_digits); auto with zarith. - assert (Hb:= Z.lt_le_incl _ _ H). - generalize (spec_add_mul_div w_0 ah Hb) - (spec_add_mul_div ah al Hb) - (spec_add_mul_div al w_0 Hb) - (spec_add_mul_div bh bl Hb) - (spec_add_mul_div bl w_0 Hb); - rewrite spec_w_0; repeat rewrite Z.mul_0_l;repeat rewrite Z.add_0_l; - rewrite Zdiv_0_l;repeat rewrite Z.add_0_r. - Spec_w_to_Z ah;Spec_w_to_Z bh. - unfold base;repeat rewrite Zmod_shift_r;zarith. - assert (H3:=to_Z_div_minus_p ah HHHH);assert(H4:=to_Z_div_minus_p al HHHH); - assert (H5:=to_Z_div_minus_p bl HHHH). - rewrite Z.mul_comm in Hh. - assert (2^[|w_head0 bh|] < wB). unfold base;apply Zpower_lt_monotone;zarith. - unfold base in H0;rewrite Zmod_small;zarith. - fold wB; rewrite (Zmod_small ([|bh|] * 2 ^ [|w_head0 bh|]));zarith. - intros U1 U2 U3 V1 V2. - generalize (@spec_w_div32 (w_add_mul_div (w_head0 bh) w_0 ah) - (w_add_mul_div (w_head0 bh) ah al) - (w_add_mul_div (w_head0 bh) al w_0) - (w_add_mul_div (w_head0 bh) bh bl) - (w_add_mul_div (w_head0 bh) bl w_0)). - destruct (w_div32 (w_add_mul_div (w_head0 bh) w_0 ah) - (w_add_mul_div (w_head0 bh) ah al) - (w_add_mul_div (w_head0 bh) al w_0) - (w_add_mul_div (w_head0 bh) bh bl) - (w_add_mul_div (w_head0 bh) bl w_0)) as (q,r). - rewrite V1;rewrite V2. rewrite Z.mul_add_distr_r. - rewrite <- (Z.add_assoc ([|bh|] * 2 ^ [|w_head0 bh|] * wB)). - unfold base;rewrite <- shift_unshift_mod;zarith. fold wB. - replace ([|bh|] * 2 ^ [|w_head0 bh|] * wB + [|bl|] * 2 ^ [|w_head0 bh|]) with - ([[WW bh bl]] * 2^[|w_head0 bh|]). 2:simpl;ring. - fold wwB. rewrite wwB_wBwB. rewrite Z.pow_2_r. rewrite U1;rewrite U2;rewrite U3. - rewrite Z.mul_assoc. rewrite Z.mul_add_distr_r. - rewrite (Z.add_assoc ([|ah|] / 2^(Zpos(w_digits) - [|w_head0 bh|])*wB * wB)). - rewrite <- Z.mul_add_distr_r. rewrite <- Z.add_assoc. - unfold base;repeat rewrite <- shift_unshift_mod;zarith. fold wB. - replace ([|ah|] * 2 ^ [|w_head0 bh|] * wB + [|al|] * 2 ^ [|w_head0 bh|]) with - ([[WW ah al]] * 2^[|w_head0 bh|]). 2:simpl;ring. - intros Hd;destruct Hd;zarith. - simpl. apply beta_lex_inv;zarith. rewrite U1;rewrite V1. - assert ([|ah|] / 2 ^ (Zpos (w_digits) - [|w_head0 bh|]) < wB/2);zarith. - apply Zdiv_lt_upper_bound;zarith. - unfold base. - replace (2^Zpos (w_digits)) with (2^(Zpos (w_digits) - 1)*2). - rewrite Z_div_mult;zarith. rewrite <- Zpower_exp;zarith. - apply Z.lt_le_trans with wB;zarith. - unfold base;apply Zpower_le_monotone;zarith. - pattern 2 at 2;replace 2 with (2^1);trivial. - rewrite <- Zpower_exp;zarith. ring_simplify (Zpos (w_digits) - 1 + 1);trivial. - change [[WW w_0 q]] with ([|w_0|]*wB+[|q|]);rewrite spec_w_0;rewrite - Z.mul_0_l;rewrite Z.add_0_l. - replace [[ww_add_mul_div (ww_sub w_0 w_WW w_opp_c w_opp_carry w_sub_c w_opp w_sub w_sub_carry - _ww_zdigits (w_0W (w_head0 bh))) W0 r]] with ([[r]]/2^[|w_head0 bh|]). - assert (0 < 2^[|w_head0 bh|]). apply Z.pow_pos_nonneg;zarith. - split. - rewrite <- (Z_div_mult [[WW ah al]] (2^[|w_head0 bh|]));zarith. - rewrite H1;rewrite Z.mul_assoc;apply Z_div_plus_l;trivial. - split;[apply Zdiv_le_lower_bound| apply Zdiv_lt_upper_bound];zarith. - rewrite spec_ww_add_mul_div. - rewrite spec_ww_sub; auto with zarith. - rewrite spec_ww_digits_. - change (Zpos (xO (w_digits))) with (2*Zpos (w_digits));zarith. - simpl ww_to_Z;rewrite Z.mul_0_l;rewrite Z.add_0_l. - rewrite spec_w_0W. - rewrite (fun x y => Zmod_small (x-y)); auto with zarith. - ring_simplify (2 * Zpos w_digits - (2 * Zpos w_digits - [|w_head0 bh|])). - rewrite Zmod_small;zarith. - split;[apply Zdiv_le_lower_bound| apply Zdiv_lt_upper_bound];zarith. - Spec_ww_to_Z r. - apply Z.lt_le_trans with wwB;zarith. - rewrite <- (Z.mul_1_r wwB);apply Z.mul_le_mono_nonneg;zarith. - split; auto with zarith. - apply Z.le_lt_trans with (2 * Zpos w_digits); auto with zarith. - unfold base, ww_digits; rewrite (Pos2Z.inj_xO w_digits). - apply Zpower2_lt_lin; auto with zarith. - rewrite spec_ww_sub; auto with zarith. - rewrite spec_ww_digits_; rewrite spec_w_0W. - rewrite Zmod_small;zarith. - rewrite Pos2Z.inj_xO; split; auto with zarith. - apply Z.le_lt_trans with (2 * Zpos w_digits); auto with zarith. - unfold base, ww_digits; rewrite (Pos2Z.inj_xO w_digits). - apply Zpower2_lt_lin; auto with zarith. - Qed. - - Lemma spec_ww_div_gt : forall a b, [[a]] > [[b]] -> 0 < [[b]] -> - let (q,r) := ww_div_gt a b in - [[a]] = [[q]] * [[b]] + [[r]] /\ - 0 <= [[r]] < [[b]]. - Proof. - intros a b Hgt Hpos;unfold ww_div_gt. - change (let (q,r) := match a, b with - | W0, _ => (W0,W0) - | _, W0 => (W0,W0) - | WW ah al, WW bh bl => - if w_eq0 ah then - let (q,r) := w_div_gt al bl in - (WW w_0 q, w_0W r) - else - match w_compare w_0 bh with - | Eq => - let(q,r):= - double_divn1 w_zdigits w_0 w_WW w_head0 w_add_mul_div w_div21 - w_compare w_sub 1 a bl in - (q, w_0W r) - | Lt => ww_div_gt_aux ah al bh bl - | Gt => (W0,W0) (* cas absurde *) - end - end in [[a]] = [[q]] * [[b]] + [[r]] /\ 0 <= [[r]] < [[b]]). - destruct a as [ |ah al]. simpl in Hgt;omega. - destruct b as [ |bh bl]. simpl in Hpos;omega. - Spec_w_to_Z ah; Spec_w_to_Z al; Spec_w_to_Z bh; Spec_w_to_Z bl. - assert (H:=@spec_eq0 ah);destruct (w_eq0 ah). - simpl ww_to_Z;rewrite H;trivial. simpl in Hgt;rewrite H in Hgt;trivial. - assert ([|bh|] <= 0). - apply beta_lex with (d:=[|al|])(b:=[|bl|]) (beta := wB);zarith. - assert ([|bh|] = 0);zarith. rewrite H1 in Hgt;rewrite H1;simpl in Hgt. - simpl. simpl in Hpos;rewrite H1 in Hpos;simpl in Hpos. - assert (H2:=spec_div_gt Hgt Hpos);destruct (w_div_gt al bl). - repeat rewrite spec_w_0W;simpl;rewrite spec_w_0;simpl;trivial. - clear H. - rewrite spec_compare; case Z.compare_spec; intros Hcmp. - rewrite spec_w_0 in Hcmp. change [[WW bh bl]] with ([|bh|]*wB+[|bl|]). - rewrite <- Hcmp;rewrite Z.mul_0_l;rewrite Z.add_0_l. - simpl in Hpos;rewrite <- Hcmp in Hpos;simpl in Hpos. - assert (H2:= @spec_double_divn1 w w_digits w_zdigits w_0 w_WW w_head0 w_add_mul_div - w_div21 w_compare w_sub w_to_Z spec_to_Z spec_w_zdigits spec_w_0 spec_w_WW spec_head0 - spec_add_mul_div spec_div21 spec_compare spec_sub 1 (WW ah al) bl Hpos). - destruct (double_divn1 w_zdigits w_0 w_WW w_head0 w_add_mul_div w_div21 - w_compare w_sub 1 - (WW ah al) bl). - rewrite spec_w_0W;unfold ww_to_Z;trivial. - apply spec_ww_div_gt_aux;trivial. rewrite spec_w_0 in Hcmp;trivial. - rewrite spec_w_0 in Hcmp;exfalso;omega. - Qed. - - Lemma spec_ww_mod_gt_aux_eq : forall ah al bh bl, - ww_mod_gt_aux ah al bh bl = snd (ww_div_gt_aux ah al bh bl). - Proof. - intros ah al bh bl. unfold ww_mod_gt_aux, ww_div_gt_aux. - case w_compare; auto. - case w_div32; auto. - Qed. - - Lemma spec_ww_mod_gt_aux : forall ah al bh bl, - [[WW ah al]] > [[WW bh bl]] -> - 0 < [|bh|] -> - [[ww_mod_gt_aux ah al bh bl]] = [[WW ah al]] mod [[WW bh bl]]. - Proof. - intros. rewrite spec_ww_mod_gt_aux_eq;trivial. - assert (H3 := spec_ww_div_gt_aux ah al bl H H0). - destruct (ww_div_gt_aux ah al bh bl) as (q,r);simpl. simpl in H,H3. - destruct H3;apply Zmod_unique with [[q]];zarith. - rewrite H1;ring. - Qed. - - Lemma spec_w_mod_gt_eq : forall a b, [|a|] > [|b|] -> 0 <[|b|] -> - [|w_mod_gt a b|] = [|snd (w_div_gt a b)|]. - Proof. - intros a b Hgt Hpos. - rewrite spec_mod_gt;trivial. - assert (H:=spec_div_gt Hgt Hpos). - destruct (w_div_gt a b) as (q,r);simpl. - rewrite Z.mul_comm in H;destruct H. - symmetry;apply Zmod_unique with [|q|];trivial. - Qed. - - Lemma spec_ww_mod_gt_eq : forall a b, [[a]] > [[b]] -> 0 < [[b]] -> - [[ww_mod_gt a b]] = [[snd (ww_div_gt a b)]]. - Proof. - intros a b Hgt Hpos. - change (ww_mod_gt a b) with - (match a, b with - | W0, _ => W0 - | _, W0 => W0 - | WW ah al, WW bh bl => - if w_eq0 ah then w_0W (w_mod_gt al bl) - else - match w_compare w_0 bh with - | Eq => - w_0W (double_modn1 w_zdigits w_0 w_head0 w_add_mul_div w_div21 - w_compare w_sub 1 a bl) - | Lt => ww_mod_gt_aux ah al bh bl - | Gt => W0 (* cas absurde *) - end end). - change (ww_div_gt a b) with - (match a, b with - | W0, _ => (W0,W0) - | _, W0 => (W0,W0) - | WW ah al, WW bh bl => - if w_eq0 ah then - let (q,r) := w_div_gt al bl in - (WW w_0 q, w_0W r) - else - match w_compare w_0 bh with - | Eq => - let(q,r):= - double_divn1 w_zdigits w_0 w_WW w_head0 w_add_mul_div w_div21 - w_compare w_sub 1 a bl in - (q, w_0W r) - | Lt => ww_div_gt_aux ah al bh bl - | Gt => (W0,W0) (* cas absurde *) - end - end). - destruct a as [ |ah al];trivial. - destruct b as [ |bh bl];trivial. - Spec_w_to_Z ah; Spec_w_to_Z al; Spec_w_to_Z bh; Spec_w_to_Z bl. - assert (H:=@spec_eq0 ah);destruct (w_eq0 ah). - simpl in Hgt;rewrite H in Hgt;trivial. - assert ([|bh|] <= 0). - apply beta_lex with (d:=[|al|])(b:=[|bl|]) (beta := wB);zarith. - assert ([|bh|] = 0);zarith. rewrite H1 in Hgt;simpl in Hgt. - simpl in Hpos;rewrite H1 in Hpos;simpl in Hpos. - rewrite spec_w_0W;rewrite spec_w_mod_gt_eq;trivial. - destruct (w_div_gt al bl);simpl;rewrite spec_w_0W;trivial. - clear H. - rewrite spec_compare; case Z.compare_spec; intros H2. - rewrite (@spec_double_modn1_aux w w_zdigits w_0 w_WW w_head0 w_add_mul_div - w_div21 w_compare w_sub w_to_Z spec_w_0 spec_compare 1 (WW ah al) bl). - destruct (double_divn1 w_zdigits w_0 w_WW w_head0 w_add_mul_div w_div21 w_compare w_sub 1 - (WW ah al) bl);simpl;trivial. - rewrite spec_ww_mod_gt_aux_eq;trivial;symmetry;trivial. - trivial. - Qed. - - Lemma spec_ww_mod_gt : forall a b, [[a]] > [[b]] -> 0 < [[b]] -> - [[ww_mod_gt a b]] = [[a]] mod [[b]]. - Proof. - intros a b Hgt Hpos. - assert (H:= spec_ww_div_gt a b Hgt Hpos). - rewrite (spec_ww_mod_gt_eq a b Hgt Hpos). - destruct (ww_div_gt a b)as(q,r);destruct H. - apply Zmod_unique with[[q]];simpl;trivial. - rewrite Z.mul_comm;trivial. - Qed. - - Lemma Zis_gcd_mod : forall a b d, - 0 < b -> Zis_gcd b (a mod b) d -> Zis_gcd a b d. - Proof. - intros a b d H H1; apply Zis_gcd_for_euclid with (a/b). - pattern a at 1;rewrite (Z_div_mod_eq a b). - ring_simplify (b * (a / b) + a mod b - a / b * b);trivial. zarith. - Qed. - - Lemma spec_ww_gcd_gt_aux_body : - forall ah al bh bl n cont, - [[WW bh bl]] <= 2^n -> - [[WW ah al]] > [[WW bh bl]] -> - (forall xh xl yh yl, - [[WW xh xl]] > [[WW yh yl]] -> [[WW yh yl]] <= 2^(n-1) -> - Zis_gcd [[WW xh xl]] [[WW yh yl]] [[cont xh xl yh yl]]) -> - Zis_gcd [[WW ah al]] [[WW bh bl]] [[ww_gcd_gt_body cont ah al bh bl]]. - Proof. - intros ah al bh bl n cont Hlog Hgt Hcont. - change (ww_gcd_gt_body cont ah al bh bl) with (match w_compare w_0 bh with - | Eq => - match w_compare w_0 bl with - | Eq => WW ah al (* normalement n'arrive pas si forme normale *) - | Lt => - let m := double_modn1 w_zdigits w_0 w_head0 w_add_mul_div w_div21 - w_compare w_sub 1 (WW ah al) bl in - WW w_0 (w_gcd_gt bl m) - | Gt => W0 (* absurde *) - end - | Lt => - let m := ww_mod_gt_aux ah al bh bl in - match m with - | W0 => WW bh bl - | WW mh ml => - match w_compare w_0 mh with - | Eq => - match w_compare w_0 ml with - | Eq => WW bh bl - | _ => - let r := double_modn1 w_zdigits w_0 w_head0 w_add_mul_div w_div21 - w_compare w_sub 1 (WW bh bl) ml in - WW w_0 (w_gcd_gt ml r) - end - | Lt => - let r := ww_mod_gt_aux bh bl mh ml in - match r with - | W0 => m - | WW rh rl => cont mh ml rh rl - end - | Gt => W0 (* absurde *) - end - end - | Gt => W0 (* absurde *) - end). - rewrite spec_compare, spec_w_0. - case Z.compare_spec; intros Hbh. - simpl ww_to_Z in *. rewrite <- Hbh. - rewrite Z.mul_0_l;rewrite Z.add_0_l. - rewrite spec_compare, spec_w_0. - case Z.compare_spec; intros Hbl. - rewrite <- Hbl;apply Zis_gcd_0. - simpl;rewrite spec_w_0;rewrite Z.mul_0_l;rewrite Z.add_0_l. - apply Zis_gcd_mod;zarith. - change ([|ah|] * wB + [|al|]) with (double_to_Z w_digits w_to_Z 1 (WW ah al)). - rewrite <- (@spec_double_modn1 w w_digits w_zdigits w_0 w_WW w_head0 w_add_mul_div - w_div21 w_compare w_sub w_to_Z spec_to_Z spec_w_zdigits spec_w_0 spec_w_WW spec_head0 spec_add_mul_div - spec_div21 spec_compare spec_sub 1 (WW ah al) bl Hbl). - apply spec_gcd_gt. - rewrite (@spec_double_modn1 w w_digits w_zdigits w_0 w_WW); trivial. - apply Z.lt_gt;match goal with | |- ?x mod ?y < ?y => - destruct (Z_mod_lt x y);zarith end. - Spec_w_to_Z bl;exfalso;omega. - assert (H:= spec_ww_mod_gt_aux _ _ _ Hgt Hbh). - assert (H2 : 0 < [[WW bh bl]]). - simpl;Spec_w_to_Z bl. apply Z.lt_le_trans with ([|bh|]*wB);zarith. - apply Z.mul_pos_pos;zarith. - apply Zis_gcd_mod;trivial. rewrite <- H. - simpl in *;destruct (ww_mod_gt_aux ah al bh bl) as [ |mh ml]. - simpl;apply Zis_gcd_0;zarith. - rewrite spec_compare, spec_w_0; case Z.compare_spec; intros Hmh. - simpl;rewrite <- Hmh;simpl. - rewrite spec_compare, spec_w_0; case Z.compare_spec; intros Hml. - rewrite <- Hml;simpl;apply Zis_gcd_0. - simpl; rewrite spec_w_0; simpl. - apply Zis_gcd_mod;zarith. - change ([|bh|] * wB + [|bl|]) with (double_to_Z w_digits w_to_Z 1 (WW bh bl)). - rewrite <- (@spec_double_modn1 w w_digits w_zdigits w_0 w_WW w_head0 w_add_mul_div - w_div21 w_compare w_sub w_to_Z spec_to_Z spec_w_zdigits spec_w_0 spec_w_WW spec_head0 spec_add_mul_div - spec_div21 spec_compare spec_sub 1 (WW bh bl) ml Hml). - apply spec_gcd_gt. - rewrite (@spec_double_modn1 w w_digits w_zdigits w_0 w_WW); trivial. - apply Z.lt_gt;match goal with | |- ?x mod ?y < ?y => - destruct (Z_mod_lt x y);zarith end. - Spec_w_to_Z ml;exfalso;omega. - assert ([[WW bh bl]] > [[WW mh ml]]). - rewrite H;simpl; apply Z.lt_gt;match goal with | |- ?x mod ?y < ?y => - destruct (Z_mod_lt x y);zarith end. - assert (H1:= spec_ww_mod_gt_aux _ _ _ H0 Hmh). - assert (H3 : 0 < [[WW mh ml]]). - simpl;Spec_w_to_Z ml. apply Z.lt_le_trans with ([|mh|]*wB);zarith. - apply Z.mul_pos_pos;zarith. - apply Zis_gcd_mod;zarith. simpl in *;rewrite <- H1. - destruct (ww_mod_gt_aux bh bl mh ml) as [ |rh rl]. simpl; apply Zis_gcd_0. - simpl;apply Hcont. simpl in H1;rewrite H1. - apply Z.lt_gt;match goal with | |- ?x mod ?y < ?y => - destruct (Z_mod_lt x y);zarith end. - apply Z.le_trans with (2^n/2). - apply Zdiv_le_lower_bound;zarith. - apply Z.le_trans with ([|bh|] * wB + [|bl|]);zarith. - assert (H3' := Z_div_mod_eq [[WW bh bl]] [[WW mh ml]] (Z.lt_gt _ _ H3)). - assert (H4 : 0 <= [[WW bh bl]]/[[WW mh ml]]). - apply Z.ge_le;apply Z_div_ge0;zarith. simpl in *;rewrite H1. - pattern ([|bh|] * wB + [|bl|]) at 2;rewrite H3'. - Z.le_elim H4. - assert (H6' : [[WW bh bl]] mod [[WW mh ml]] = - [[WW bh bl]] - [[WW mh ml]] * ([[WW bh bl]]/[[WW mh ml]])). - simpl;pattern ([|bh|] * wB + [|bl|]) at 2;rewrite H3';ring. simpl in H6'. - assert ([[WW mh ml]] <= [[WW mh ml]] * ([[WW bh bl]]/[[WW mh ml]])). - simpl;pattern ([|mh|]*wB+[|ml|]) at 1;rewrite <- Z.mul_1_r;zarith. - simpl in *;assert (H8 := Z_mod_lt [[WW bh bl]] [[WW mh ml]]);simpl in H8; - zarith. - assert (H8 := Z_mod_lt [[WW bh bl]] [[WW mh ml]]);simpl in *;zarith. - rewrite <- H4 in H3';rewrite Z.mul_0_r in H3';simpl in H3';zarith. - pattern n at 1;replace n with (n-1+1);try ring. - rewrite Zpower_exp;zarith. change (2^1) with 2. - rewrite Z_div_mult;zarith. - assert (2^1 <= 2^n). change (2^1) with 2;zarith. - assert (H7 := @Zpower_le_monotone_inv 2 1 n);zarith. - Spec_w_to_Z mh;exfalso;zarith. - Spec_w_to_Z bh;exfalso;zarith. - Qed. - - Lemma spec_ww_gcd_gt_aux : - forall p cont n, - (forall xh xl yh yl, - [[WW xh xl]] > [[WW yh yl]] -> - [[WW yh yl]] <= 2^n -> - Zis_gcd [[WW xh xl]] [[WW yh yl]] [[cont xh xl yh yl]]) -> - forall ah al bh bl , [[WW ah al]] > [[WW bh bl]] -> - [[WW bh bl]] <= 2^(Zpos p + n) -> - Zis_gcd [[WW ah al]] [[WW bh bl]] - [[ww_gcd_gt_aux p cont ah al bh bl]]. - Proof. - induction p;intros cont n Hcont ah al bh bl Hgt Hs;simpl ww_gcd_gt_aux. - assert (0 < Zpos p). unfold Z.lt;reflexivity. - apply spec_ww_gcd_gt_aux_body with (n := Zpos (xI p) + n); - trivial;rewrite Pos2Z.inj_xI. - intros. apply IHp with (n := Zpos p + n);zarith. - intros. apply IHp with (n := n );zarith. - apply Z.le_trans with (2 ^ (2* Zpos p + 1+ n -1));zarith. - apply Z.pow_le_mono_r;zarith. - assert (0 < Zpos p). unfold Z.lt;reflexivity. - apply spec_ww_gcd_gt_aux_body with (n := Zpos (xO p) + n );trivial. - rewrite (Pos2Z.inj_xO p). - intros. apply IHp with (n := Zpos p + n - 1);zarith. - intros. apply IHp with (n := n -1 );zarith. - intros;apply Hcont;zarith. - apply Z.le_trans with (2^(n-1));zarith. - apply Z.pow_le_mono_r;zarith. - apply Z.le_trans with (2 ^ (Zpos p + n -1));zarith. - apply Z.pow_le_mono_r;zarith. - apply Z.le_trans with (2 ^ (2*Zpos p + n -1));zarith. - apply Z.pow_le_mono_r;zarith. - apply spec_ww_gcd_gt_aux_body with (n := n+1);trivial. - rewrite Z.add_comm;trivial. - ring_simplify (n + 1 - 1);trivial. - Qed. - -End DoubleDivGt. - -Section DoubleDiv. - - Variable w : Type. - Variable w_digits : positive. - Variable ww_1 : zn2z w. - Variable ww_compare : zn2z w -> zn2z w -> comparison. - - Variable ww_div_gt : zn2z w -> zn2z w -> zn2z w * zn2z w. - Variable ww_mod_gt : zn2z w -> zn2z w -> zn2z w. - - Definition ww_div a b := - match ww_compare a b with - | Gt => ww_div_gt a b - | Eq => (ww_1, W0) - | Lt => (W0, a) - end. - - Definition ww_mod a b := - match ww_compare a b with - | Gt => ww_mod_gt a b - | Eq => W0 - | Lt => a - end. - - Variable w_to_Z : w -> Z. - Notation wB := (base w_digits). - Notation wwB := (base (ww_digits w_digits)). - Notation "[| x |]" := (w_to_Z x) (at level 0, x at level 99). - Notation "[[ x ]]" := (ww_to_Z w_digits w_to_Z x)(at level 0, x at level 99). - Variable spec_to_Z : forall x, 0 <= [|x|] < wB. - Variable spec_ww_1 : [[ww_1]] = 1. - Variable spec_ww_compare : forall x y, - ww_compare x y = Z.compare [[x]] [[y]]. - Variable spec_ww_div_gt : forall a b, [[a]] > [[b]] -> 0 < [[b]] -> - let (q,r) := ww_div_gt a b in - [[a]] = [[q]] * [[b]] + [[r]] /\ - 0 <= [[r]] < [[b]]. - Variable spec_ww_mod_gt : forall a b, [[a]] > [[b]] -> 0 < [[b]] -> - [[ww_mod_gt a b]] = [[a]] mod [[b]]. - - Ltac Spec_w_to_Z x := - let H:= fresh "HH" in - assert (H:= spec_to_Z x). - - Ltac Spec_ww_to_Z x := - let H:= fresh "HH" in - assert (H:= spec_ww_to_Z w_digits w_to_Z spec_to_Z x). - - Lemma spec_ww_div : forall a b, 0 < [[b]] -> - let (q,r) := ww_div a b in - [[a]] = [[q]] * [[b]] + [[r]] /\ - 0 <= [[r]] < [[b]]. - Proof. - intros a b Hpos;unfold ww_div. - rewrite spec_ww_compare; case Z.compare_spec; intros. - simpl;rewrite spec_ww_1;split;zarith. - simpl;split;[ring|Spec_ww_to_Z a;zarith]. - apply spec_ww_div_gt;auto with zarith. - Qed. - - Lemma spec_ww_mod : forall a b, 0 < [[b]] -> - [[ww_mod a b]] = [[a]] mod [[b]]. - Proof. - intros a b Hpos;unfold ww_mod. - rewrite spec_ww_compare; case Z.compare_spec; intros. - simpl;apply Zmod_unique with 1;try rewrite H;zarith. - Spec_ww_to_Z a;symmetry;apply Zmod_small;zarith. - apply spec_ww_mod_gt;auto with zarith. - Qed. - - - Variable w_0 : w. - Variable w_1 : w. - Variable w_compare : w -> w -> comparison. - Variable w_eq0 : w -> bool. - Variable w_gcd_gt : w -> w -> w. - Variable _ww_digits : positive. - Variable spec_ww_digits_ : _ww_digits = xO w_digits. - Variable ww_gcd_gt_fix : - positive -> (w -> w -> w -> w -> zn2z w) -> - w -> w -> w -> w -> zn2z w. - - Variable spec_w_0 : [|w_0|] = 0. - Variable spec_w_1 : [|w_1|] = 1. - Variable spec_compare : - forall x y, w_compare x y = Z.compare [|x|] [|y|]. - Variable spec_eq0 : forall x, w_eq0 x = true -> [|x|] = 0. - Variable spec_gcd_gt : forall a b, [|a|] > [|b|] -> - Zis_gcd [|a|] [|b|] [|w_gcd_gt a b|]. - Variable spec_gcd_gt_fix : - forall p cont n, - (forall xh xl yh yl, - [[WW xh xl]] > [[WW yh yl]] -> - [[WW yh yl]] <= 2^n -> - Zis_gcd [[WW xh xl]] [[WW yh yl]] [[cont xh xl yh yl]]) -> - forall ah al bh bl , [[WW ah al]] > [[WW bh bl]] -> - [[WW bh bl]] <= 2^(Zpos p + n) -> - Zis_gcd [[WW ah al]] [[WW bh bl]] - [[ww_gcd_gt_fix p cont ah al bh bl]]. - - Definition gcd_cont (xh xl yh yl:w) := - match w_compare w_1 yl with - | Eq => ww_1 - | _ => WW xh xl - end. - - Lemma spec_gcd_cont : forall xh xl yh yl, - [[WW xh xl]] > [[WW yh yl]] -> - [[WW yh yl]] <= 1 -> - Zis_gcd [[WW xh xl]] [[WW yh yl]] [[gcd_cont xh xl yh yl]]. - Proof. - intros xh xl yh yl Hgt' Hle. simpl in Hle. - assert ([|yh|] = 0). - change 1 with (0*wB+1) in Hle. - assert (0 <= 1 < wB). split;zarith. apply wB_pos. - assert (H1:= beta_lex _ _ _ _ _ Hle (spec_to_Z yl) H). - Spec_w_to_Z yh;zarith. - unfold gcd_cont; rewrite spec_compare, spec_w_1. - case Z.compare_spec; intros Hcmpy. - simpl;rewrite H;simpl; - rewrite spec_ww_1;rewrite <- Hcmpy;apply Zis_gcd_mod;zarith. - rewrite <- (Zmod_unique ([|xh|]*wB+[|xl|]) 1 ([|xh|]*wB+[|xl|]) 0);zarith. - rewrite H in Hle; exfalso;zarith. - assert (H0 : [|yl|] = 0) by (Spec_w_to_Z yl;zarith). - simpl. rewrite H0, H;simpl;apply Zis_gcd_0;trivial. - Qed. - - - Variable cont : w -> w -> w -> w -> zn2z w. - Variable spec_cont : forall xh xl yh yl, - [[WW xh xl]] > [[WW yh yl]] -> - [[WW yh yl]] <= 1 -> - Zis_gcd [[WW xh xl]] [[WW yh yl]] [[cont xh xl yh yl]]. - - Definition ww_gcd_gt a b := - match a, b with - | W0, _ => b - | _, W0 => a - | WW ah al, WW bh bl => - if w_eq0 ah then (WW w_0 (w_gcd_gt al bl)) - else ww_gcd_gt_fix _ww_digits cont ah al bh bl - end. - - Definition ww_gcd a b := - Eval lazy beta delta [ww_gcd_gt] in - match ww_compare a b with - | Gt => ww_gcd_gt a b - | Eq => a - | Lt => ww_gcd_gt b a - end. - - Lemma spec_ww_gcd_gt : forall a b, [[a]] > [[b]] -> - Zis_gcd [[a]] [[b]] [[ww_gcd_gt a b]]. - Proof. - intros a b Hgt;unfold ww_gcd_gt. - destruct a as [ |ah al]. simpl;apply Zis_gcd_sym;apply Zis_gcd_0. - destruct b as [ |bh bl]. simpl;apply Zis_gcd_0. - simpl in Hgt. generalize (@spec_eq0 ah);destruct (w_eq0 ah);intros. - simpl;rewrite H in Hgt;trivial;rewrite H;trivial;rewrite spec_w_0;simpl. - assert ([|bh|] <= 0). - apply beta_lex with (d:=[|al|])(b:=[|bl|]) (beta := wB);zarith. - Spec_w_to_Z bh;assert ([|bh|] = 0);zarith. rewrite H1 in Hgt;simpl in Hgt. - rewrite H1;simpl;auto. clear H. - apply spec_gcd_gt_fix with (n:= 0);trivial. - rewrite Z.add_0_r;rewrite spec_ww_digits_. - change (2 ^ Zpos (xO w_digits)) with wwB. Spec_ww_to_Z (WW bh bl);zarith. - Qed. - - Lemma spec_ww_gcd : forall a b, Zis_gcd [[a]] [[b]] [[ww_gcd a b]]. - Proof. - intros a b. - change (ww_gcd a b) with - (match ww_compare a b with - | Gt => ww_gcd_gt a b - | Eq => a - | Lt => ww_gcd_gt b a - end). - rewrite spec_ww_compare; case Z.compare_spec; intros Hcmp. - Spec_ww_to_Z b;rewrite Hcmp. - apply Zis_gcd_for_euclid with 1;zarith. - ring_simplify ([[b]] - 1 * [[b]]). apply Zis_gcd_0;zarith. - apply Zis_gcd_sym;apply spec_ww_gcd_gt;zarith. - apply spec_ww_gcd_gt;zarith. - Qed. - -End DoubleDiv. - |