summaryrefslogtreecommitdiff
path: root/theories/ZArith/Zbinary.v
diff options
context:
space:
mode:
authorGravatar Stephane Glondu <steph@glondu.net>2010-07-21 09:46:51 +0200
committerGravatar Stephane Glondu <steph@glondu.net>2010-07-21 09:46:51 +0200
commit5b7eafd0f00a16d78f99a27f5c7d5a0de77dc7e6 (patch)
tree631ad791a7685edafeb1fb2e8faeedc8379318ae /theories/ZArith/Zbinary.v
parentda178a880e3ace820b41d38b191d3785b82991f5 (diff)
Imported Upstream snapshot 8.3~beta0+13298
Diffstat (limited to 'theories/ZArith/Zbinary.v')
-rw-r--r--theories/ZArith/Zbinary.v352
1 files changed, 0 insertions, 352 deletions
diff --git a/theories/ZArith/Zbinary.v b/theories/ZArith/Zbinary.v
deleted file mode 100644
index 08f08e12..00000000
--- a/theories/ZArith/Zbinary.v
+++ /dev/null
@@ -1,352 +0,0 @@
-(************************************************************************)
-(* v * The Coq Proof Assistant / The Coq Development Team *)
-(* <O___,, * CNRS-Ecole Polytechnique-INRIA Futurs-Universite Paris Sud *)
-(* \VV/ **************************************************************)
-(* // * This file is distributed under the terms of the *)
-(* * GNU Lesser General Public License Version 2.1 *)
-(************************************************************************)
-
-(*i $Id: Zbinary.v 9245 2006-10-17 12:53:34Z notin $ i*)
-
-(** Bit vectors interpreted as integers.
- Contribution by Jean Duprat (ENS Lyon). *)
-
-Require Import Bvector.
-Require Import ZArith.
-Require Export Zpower.
-Require Import Omega.
-
-(** L'évaluation des vecteurs de booléens se font à la fois en binaire et
- en complément à  deux. Le nombre appartient à  Z.
- On utilise donc Omega pour faire les calculs dans Z.
- De plus, on utilise les fonctions 2^n où n est un naturel, ici la longueur.
- two_power_nat = [n:nat](POS (shift_nat n xH))
- : nat->Z
- two_power_nat_S
- : (n:nat)`(two_power_nat (S n)) = 2*(two_power_nat n)`
- Z_lt_ge_dec
- : (x,y:Z){`x < y`}+{`x >= y`}
-*)
-
-
-Section VALUE_OF_BOOLEAN_VECTORS.
-
-(** Les calculs sont effectués dans la convention positive usuelle.
- Les valeurs correspondent soit à  l'écriture binaire (nat),
- soit au complément à  deux (int).
- On effectue le calcul suivant le schéma de Horner.
- Le complément à  deux n'a de sens que sur les vecteurs de taille
- supérieure ou égale à  un, le bit de signe étant évalué négativement.
-*)
-
- Definition bit_value (b:bool) : Z :=
- match b with
- | true => 1%Z
- | false => 0%Z
- end.
-
- Lemma binary_value : forall n:nat, Bvector n -> Z.
- Proof.
- simple induction n; intros.
- exact 0%Z.
-
- inversion H0.
- exact (bit_value a + 2 * H H2)%Z.
- Defined.
-
- Lemma two_compl_value : forall n:nat, Bvector (S n) -> Z.
- Proof.
- simple induction n; intros.
- inversion H.
- exact (- bit_value a)%Z.
-
- inversion H0.
- exact (bit_value a + 2 * H H2)%Z.
- Defined.
-
-End VALUE_OF_BOOLEAN_VECTORS.
-
-Section ENCODING_VALUE.
-
-(** On calcule la valeur binaire selon un schema de Horner.
- Le calcul s'arrete à  la longueur du vecteur sans vérification.
- On definit une fonction Zmod2 calquee sur Zdiv2 mais donnant le quotient
- de la division z=2q+r avec 0<=r<=1.
- La valeur en complément à  deux est calculée selon un schema de Horner
- avec Zmod2, le paramètre est la taille moins un.
-*)
-
- Definition Zmod2 (z:Z) :=
- match z with
- | Z0 => 0%Z
- | Zpos p => match p with
- | xI q => Zpos q
- | xO q => Zpos q
- | xH => 0%Z
- end
- | Zneg p =>
- match p with
- | xI q => (Zneg q - 1)%Z
- | xO q => Zneg q
- | xH => (-1)%Z
- end
- end.
-
-
- Lemma Zmod2_twice :
- forall z:Z, z = (2 * Zmod2 z + bit_value (Zeven.Zodd_bool z))%Z.
- Proof.
- destruct z; simpl in |- *.
- trivial.
-
- destruct p; simpl in |- *; trivial.
-
- destruct p; simpl in |- *.
- destruct p as [p| p| ]; simpl in |- *.
- rewrite <- (Pdouble_minus_one_o_succ_eq_xI p); trivial.
-
- trivial.
-
- trivial.
-
- trivial.
-
- trivial.
- Qed.
-
- Lemma Z_to_binary : forall n:nat, Z -> Bvector n.
- Proof.
- simple induction n; intros.
- exact Bnil.
-
- exact (Bcons (Zeven.Zodd_bool H0) n0 (H (Zeven.Zdiv2 H0))).
- Defined.
-
- Lemma Z_to_two_compl : forall n:nat, Z -> Bvector (S n).
- Proof.
- simple induction n; intros.
- exact (Bcons (Zeven.Zodd_bool H) 0 Bnil).
-
- exact (Bcons (Zeven.Zodd_bool H0) (S n0) (H (Zmod2 H0))).
- Defined.
-
-End ENCODING_VALUE.
-
-Section Z_BRIC_A_BRAC.
-
- (** Bibliotheque de lemmes utiles dans la section suivante.
- Utilise largement ZArith.
- Mériterait d'être récrite.
- *)
-
- Lemma binary_value_Sn :
- forall (n:nat) (b:bool) (bv:Bvector n),
- binary_value (S n) (Vcons bool b n bv) =
- (bit_value b + 2 * binary_value n bv)%Z.
- Proof.
- intros; auto.
- Qed.
-
- Lemma Z_to_binary_Sn :
- forall (n:nat) (b:bool) (z:Z),
- (z >= 0)%Z ->
- Z_to_binary (S n) (bit_value b + 2 * z) = Bcons b n (Z_to_binary n z).
- Proof.
- destruct b; destruct z; simpl in |- *; auto.
- intro H; elim H; trivial.
- Qed.
-
- Lemma binary_value_pos :
- forall (n:nat) (bv:Bvector n), (binary_value n bv >= 0)%Z.
- Proof.
- induction bv as [| a n v IHbv]; simpl in |- *.
- omega.
-
- destruct a; destruct (binary_value n v); simpl in |- *; auto.
- auto with zarith.
- Qed.
-
- Lemma two_compl_value_Sn :
- forall (n:nat) (bv:Bvector (S n)) (b:bool),
- two_compl_value (S n) (Bcons b (S n) bv) =
- (bit_value b + 2 * two_compl_value n bv)%Z.
- Proof.
- intros; auto.
- Qed.
-
- Lemma Z_to_two_compl_Sn :
- forall (n:nat) (b:bool) (z:Z),
- Z_to_two_compl (S n) (bit_value b + 2 * z) =
- Bcons b (S n) (Z_to_two_compl n z).
- Proof.
- destruct b; destruct z as [| p| p]; auto.
- destruct p as [p| p| ]; auto.
- destruct p as [p| p| ]; simpl in |- *; auto.
- intros; rewrite (Psucc_o_double_minus_one_eq_xO p); trivial.
- Qed.
-
- Lemma Z_to_binary_Sn_z :
- forall (n:nat) (z:Z),
- Z_to_binary (S n) z =
- Bcons (Zeven.Zodd_bool z) n (Z_to_binary n (Zeven.Zdiv2 z)).
- Proof.
- intros; auto.
- Qed.
-
- Lemma Z_div2_value :
- forall z:Z,
- (z >= 0)%Z -> (bit_value (Zeven.Zodd_bool z) + 2 * Zeven.Zdiv2 z)%Z = z.
- Proof.
- destruct z as [| p| p]; auto.
- destruct p; auto.
- intro H; elim H; trivial.
- Qed.
-
- Lemma Pdiv2 : forall z:Z, (z >= 0)%Z -> (Zeven.Zdiv2 z >= 0)%Z.
- Proof.
- destruct z as [| p| p].
- auto.
-
- destruct p; auto.
- simpl in |- *; intros; omega.
-
- intro H; elim H; trivial.
- Qed.
-
- Lemma Zdiv2_two_power_nat :
- forall (z:Z) (n:nat),
- (z >= 0)%Z ->
- (z < two_power_nat (S n))%Z -> (Zeven.Zdiv2 z < two_power_nat n)%Z.
- Proof.
- intros.
- cut (2 * Zeven.Zdiv2 z < 2 * two_power_nat n)%Z; intros.
- omega.
-
- rewrite <- two_power_nat_S.
- destruct (Zeven.Zeven_odd_dec z); intros.
- rewrite <- Zeven.Zeven_div2; auto.
-
- generalize (Zeven.Zodd_div2 z H z0); omega.
- Qed.
-
- Lemma Z_to_two_compl_Sn_z :
- forall (n:nat) (z:Z),
- Z_to_two_compl (S n) z =
- Bcons (Zeven.Zodd_bool z) (S n) (Z_to_two_compl n (Zmod2 z)).
- Proof.
- intros; auto.
- Qed.
-
- Lemma Zeven_bit_value :
- forall z:Z, Zeven.Zeven z -> bit_value (Zeven.Zodd_bool z) = 0%Z.
- Proof.
- destruct z; unfold bit_value in |- *; auto.
- destruct p; tauto || (intro H; elim H).
- destruct p; tauto || (intro H; elim H).
- Qed.
-
- Lemma Zodd_bit_value :
- forall z:Z, Zeven.Zodd z -> bit_value (Zeven.Zodd_bool z) = 1%Z.
- Proof.
- destruct z; unfold bit_value in |- *; auto.
- intros; elim H.
- destruct p; tauto || (intros; elim H).
- destruct p; tauto || (intros; elim H).
- Qed.
-
- Lemma Zge_minus_two_power_nat_S :
- forall (n:nat) (z:Z),
- (z >= - two_power_nat (S n))%Z -> (Zmod2 z >= - two_power_nat n)%Z.
- Proof.
- intros n z; rewrite (two_power_nat_S n).
- generalize (Zmod2_twice z).
- destruct (Zeven.Zeven_odd_dec z) as [H| H].
- rewrite (Zeven_bit_value z H); intros; omega.
-
- rewrite (Zodd_bit_value z H); intros; omega.
- Qed.
-
- Lemma Zlt_two_power_nat_S :
- forall (n:nat) (z:Z),
- (z < two_power_nat (S n))%Z -> (Zmod2 z < two_power_nat n)%Z.
- Proof.
- intros n z; rewrite (two_power_nat_S n).
- generalize (Zmod2_twice z).
- destruct (Zeven.Zeven_odd_dec z) as [H| H].
- rewrite (Zeven_bit_value z H); intros; omega.
-
- rewrite (Zodd_bit_value z H); intros; omega.
- Qed.
-
-End Z_BRIC_A_BRAC.
-
-Section COHERENT_VALUE.
-
-(** On vérifie que dans l'intervalle de définition les fonctions sont
- réciproques l'une de l'autre. Elles utilisent les lemmes du bric-a-brac.
-*)
-
- Lemma binary_to_Z_to_binary :
- forall (n:nat) (bv:Bvector n), Z_to_binary n (binary_value n bv) = bv.
- Proof.
- induction bv as [| a n bv IHbv].
- auto.
-
- rewrite binary_value_Sn.
- rewrite Z_to_binary_Sn.
- rewrite IHbv; trivial.
-
- apply binary_value_pos.
- Qed.
-
- Lemma two_compl_to_Z_to_two_compl :
- forall (n:nat) (bv:Bvector n) (b:bool),
- Z_to_two_compl n (two_compl_value n (Bcons b n bv)) = Bcons b n bv.
- Proof.
- induction bv as [| a n bv IHbv]; intro b.
- destruct b; auto.
-
- rewrite two_compl_value_Sn.
- rewrite Z_to_two_compl_Sn.
- rewrite IHbv; trivial.
- Qed.
-
- Lemma Z_to_binary_to_Z :
- forall (n:nat) (z:Z),
- (z >= 0)%Z ->
- (z < two_power_nat n)%Z -> binary_value n (Z_to_binary n z) = z.
- Proof.
- induction n as [| n IHn].
- unfold two_power_nat, shift_nat in |- *; simpl in |- *; intros; omega.
-
- intros; rewrite Z_to_binary_Sn_z.
- rewrite binary_value_Sn.
- rewrite IHn.
- apply Z_div2_value; auto.
-
- apply Pdiv2; trivial.
-
- apply Zdiv2_two_power_nat; trivial.
- Qed.
-
- Lemma Z_to_two_compl_to_Z :
- forall (n:nat) (z:Z),
- (z >= - two_power_nat n)%Z ->
- (z < two_power_nat n)%Z -> two_compl_value n (Z_to_two_compl n z) = z.
- Proof.
- induction n as [| n IHn].
- unfold two_power_nat, shift_nat in |- *; simpl in |- *; intros.
- assert (z = (-1)%Z \/ z = 0%Z). omega.
- intuition; subst z; trivial.
-
- intros; rewrite Z_to_two_compl_Sn_z.
- rewrite two_compl_value_Sn.
- rewrite IHn.
- generalize (Zmod2_twice z); omega.
-
- apply Zge_minus_two_power_nat_S; auto.
-
- apply Zlt_two_power_nat_S; auto.
- Qed.
-
-End COHERENT_VALUE.