(****************************************************************************  IEEE754  :  NDiv  Laurent Thery  ***************************************************************************** Definition of the quotient and divisibility for natural and relative numbers*)
Require Export Omega.
Require Export Paux.
Definition oZ1 (x : Option positive) :=
match x with
| None => 0%Z
| Some z => Zpos z
end.
(* We use the  function Pdiv function to build our Zquotient*)
Definition Zquotient (n m : Z) :=
match n, m with
| Z0, _ => 0%Z
| _, Z0 => 0%Z
| Zpos x, Zpos y => match Pdiv x y with
| (x, _) => oZ1 x
end
| Zneg x, Zneg y => match Pdiv x y with
| (x, _) => oZ1 x
end
| Zpos x, Zneg y => match Pdiv x y with
| (x, _) => (- oZ1 x)%Z
end
| Zneg x, Zpos y => match Pdiv x y with
| (x, _) => (- oZ1 x)%Z
end
end.
intros z; case z; simpl in |- *;
try (intros; apply sym_equal; apply inject_nat_convert; auto);
auto.
Qed.
intros z; case z; simpl in |- *; auto with arith.
Qed.
Hint Resolve Zero_le_oZ: arith.
(* It has the required property *)
intros m n; unfold Zquotient in |- *; case n; simpl in |- *.
intros H; case H; auto.
intros n' Hn'; case m; simpl in |- *; auto.
exists 0%Z; repeat split; simpl in |- *; auto with zarith.
intros m'; generalize (Pdiv_correct m' n'); case (Pdiv m' n'); simpl in |- *;
auto.
intros q r (H1, H2); exists (oZ1 r); repeat (split; auto with zarith).
rewrite <- (inject_nat_convert (Zpos m') m'); auto.
rewrite H1.
rewrite inj_plus; rewrite inj_mult.
rewrite <- (inject_nat_convert (Zpos n') n'); auto.
repeat rewrite inj_oZ1; auto.
rewrite inj_oZ1; rewrite Z.abs_eq; auto with zarith.
rewrite <- (inject_nat_convert (Zpos m') m'); auto with zarith.
rewrite <- (inject_nat_convert (Zpos n') n'); auto with zarith.
rewrite inj_oZ1; rewrite Z.abs_eq; auto with zarith.
rewrite <- (inject_nat_convert (Zpos n') n'); auto with zarith.
intros m'; generalize (Pdiv_correct m' n'); case (Pdiv m' n'); simpl in |- *;
auto.
intros q r (H1, H2); exists (- oZ1 r)%Z; repeat (split; auto with zarith).
replace (Zneg m') with (- Zpos m')%Z; [ idtac | simpl in |- *; auto ].
rewrite <- (inject_nat_convert (Zpos m') m'); auto.
rewrite H1.
rewrite inj_plus; rewrite inj_mult.
rewrite <- (inject_nat_convert (Zpos n') n'); auto.
repeat rewrite inj_oZ1; auto with zarith.
ring.
rewrite <- Zopp_mult_distr_l; rewrite Zabs_Zopp.
rewrite inj_oZ1; rewrite Z.abs_eq; auto with zarith.
rewrite <- (inject_nat_convert (Zpos m') m'); auto with zarith.
rewrite <- (inject_nat_convert (Zpos n') n'); auto with zarith.
rewrite Zabs_Zopp.
rewrite inj_oZ1; rewrite Z.abs_eq; auto with zarith.
rewrite <- (inject_nat_convert (Zpos n') n'); auto with zarith.
intros n' Hn'; case m; simpl in |- *; auto.
exists 0%Z; repeat split; simpl in |- *; auto with zarith.
intros m'; generalize (Pdiv_correct m' n'); case (Pdiv m' n'); simpl in |- *;
auto.
intros q r (H1, H2); exists (oZ1 r); repeat (split; auto with zarith).
replace (Zneg n') with (- Zpos n')%Z; [ idtac | simpl in |- *; auto ].
rewrite <- (inject_nat_convert (Zpos m') m'); auto.
rewrite H1.
rewrite inj_plus; rewrite inj_mult.
rewrite <- (inject_nat_convert (Zpos n') n'); auto.
repeat rewrite inj_oZ1; auto with zarith.
ring.
replace (Zneg n') with (- Zpos n')%Z; [ idtac | simpl in |- *; auto ].
rewrite Zmult_opp_opp.
rewrite inj_oZ1; rewrite Z.abs_eq; auto with zarith.
rewrite <- (inject_nat_convert (Zpos n') n'); auto with zarith.
rewrite <- (inject_nat_convert (Zpos m') m'); auto with zarith.
rewrite inj_oZ1; rewrite Z.abs_eq; auto with zarith.
rewrite <- (inject_nat_convert (Zpos n') n'); auto with zarith.
intros m'; generalize (Pdiv_correct m' n'); case (Pdiv m' n'); simpl in |- *;
auto.
intros q r (H1, H2); exists (- oZ1 r)%Z; repeat (split; auto with zarith).
replace (Zneg m') with (- Zpos m')%Z; [ idtac | simpl in |- *; auto ].
rewrite <- (inject_nat_convert (Zpos m') m'); auto.
replace (Zneg n') with (- Zpos n')%Z; [ idtac | simpl in |- *; auto ].
rewrite H1.
rewrite inj_plus; rewrite inj_mult.
rewrite <- (inject_nat_convert (Zpos n') n'); auto.
repeat rewrite inj_oZ1; auto with zarith.
ring.
replace (Zneg n') with (- Zpos n')%Z; [ idtac | simpl in |- *; auto ].
rewrite <- Zopp_mult_distr_r; rewrite Zabs_Zopp.
rewrite inj_oZ1; rewrite Z.abs_eq; auto with zarith.
rewrite <- (inject_nat_convert (Zpos m') m'); auto with zarith.
rewrite <- (inject_nat_convert (Zpos n') n'); auto with zarith.
rewrite Zabs_Zopp.
rewrite inj_oZ1; rewrite Z.abs_eq; auto with zarith.
rewrite <- (inject_nat_convert (Zpos n') n'); auto with zarith.
Qed.
intros z1 z2 H H0; case (Z.eq_dec z2 0); intros Z1.
rewrite Z1; red in |- *; case z1; simpl in |- *; auto; intros; red in |- *;
intros; discriminate.
case (ZquotientProp z1 z2); auto; intros r (H1, (H2, H3)).
case (Zle_or_lt 0 (Zquotient z1 z2)); auto; intros Z2.
Contradict H3; apply Zle_not_lt.
replace r with (z1 - Zquotient z1 z2 * z2)%Z;
[ idtac | pattern z1 at 1 in |- *; rewrite H1; ring ].
repeat rewrite Z.abs_eq; auto.
pattern z2 at 1 in |- *; replace z2 with (0 + 1 * z2)%Z; [ idtac | ring ].
unfold Zminus in |- *; apply Z.le_trans with (z1 + 1 * z2)%Z; auto with zarith.
apply Zplus_le_compat_l.
rewrite Zopp_mult_distr_l.
apply Zle_Zmult_comp_r; auto with zarith.
unfold Zminus in |- *; rewrite Zopp_mult_distr_l; auto with zarith.
Qed.
(* The property of a  number to divide another one (Ndivides n m) shoud be read as m divides n *)
Definition Zdivides (n m : Z) := exists q : Z, n = (m * q)%Z.
intros n m H' H'0.
case H'0; intros z1 Hz1.
case (ZquotientProp n m); auto; intros z2 (Hz2, (Hz3, Hz4)).
cut (z2 = 0%Z);
[ intros H1; pattern n at 1 in |- *; rewrite Hz2; rewrite H1; ring | idtac ].
cut (z2 = ((z1 - Zquotient n m) * m)%Z); [ intros H2 | idtac ].
case (Z.eq_dec (z1 - Zquotient n m) 0); intros H3.
rewrite H2; rewrite H3; ring.
Contradict Hz4.
replace (Z.abs m) with (1 * Z.abs m)%Z; [ idtac | ring ].
apply Zle_not_lt; rewrite H2.
rewrite Zabs_Zmult; apply Zle_Zmult_comp_r; auto with zarith.
generalize H3; case (z1 - Zquotient n m)%Z;
try (intros H1; case H1; auto; fail); simpl in |- *;
intros p; case p; simpl in |- *; auto; intros; red in |- *;
simpl in |- *; auto; red in |- *; intros; discriminate.
rewrite Zmult_minus_distr_r; rewrite (Zmult_comm z1); rewrite <- Hz1;
(pattern n at 1 in |- *; rewrite Hz2); ring.
Qed.
intros n m H'; red in |- *.
exists (Zquotient n m); auto.
pattern n at 1 in |- *; rewrite H'; auto with zarith.
Qed.
intros n m p H'; red in H'.
elim H'; intros q E.
red in |- *.
exists q.
rewrite E.
auto with zarith.
Qed.
intros a b c H H0.
case (Zle_or_lt c 0); intros Zl1.
apply Zle_antisym; apply Zmult_le_reg_r with (p := (- c)%Z); try apply Z.lt_gt;
auto with zarith; repeat rewrite <- Zopp_mult_distr_r;
rewrite H0; auto with zarith.
apply Zle_antisym; apply Zmult_le_reg_r with (p := c); try apply Z.lt_gt;
auto with zarith; rewrite H0; auto with zarith.
Qed.
intros n m p H' H'0.
case H'0; intros q E.
exists q.
apply Zeq_mult_simpl with (c := p); auto.
rewrite (Zmult_comm n); rewrite E; ring.
Qed.
Definition ZdividesP : forall n m : Z, {Zdivides n m} + {~ Zdivides n m}.
intros n m; case m.
case n.
left; red in |- *; exists 0%Z; auto with zarith.
intros p; right; red in |- *; intros H; case H; simpl in |- *; intros f H1;
discriminate.
intros p; right; red in |- *; intros H; case H; simpl in |- *; intros f H1;
discriminate.
intros p; generalize (Z_eq_bool_correct (Zquotient n (Zpos p) * Zpos p) n);
case (Z_eq_bool (Zquotient n (Zpos p) * Zpos p) n);
intros H1.
left; apply ZdividesZquotientInv; auto.
right; Contradict H1; apply sym_equal; apply ZdividesZquotient; auto.
red in |- *; intros; discriminate.
intros p; generalize (Z_eq_bool_correct (Zquotient n (Zneg p) * Zneg p) n);
case (Z_eq_bool (Zquotient n (Zneg p) * Zneg p) n);
intros H1.
left; apply ZdividesZquotientInv; auto.
right; Contradict H1; apply sym_equal; apply ZdividesZquotient; auto.
red in |- *; intros; discriminate.
Defined.
(* Eval Compute in (ZdividesP (POS (xO (xO xH))) (POS (xO xH))). *)
intros m.
case (ZquotientProp m 1); auto.
red in |- *; intros; discriminate.
intros z (H1, (H2, H3)).
pattern m at 2 in |- *; rewrite H1; replace z with 0%Z; try ring.
generalize H3; case z; simpl in |- *; auto; intros p; case p;
unfold Z.lt in |- *; simpl in |- *; intros; discriminate.
Qed.
intros m; exists m; auto with zarith.
Qed.

Theorem Zabs_eq_case :
forall z1 z2 : Z, Z.abs z1 = Z.abs z2 -> z1 = z2 \/ z1 = (- z2)%Z.