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Diffstat (limited to 'theories7/ZArith/Zlogarithm.v')
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diff --git a/theories7/ZArith/Zlogarithm.v b/theories7/ZArith/Zlogarithm.v deleted file mode 100644 index dc850738..00000000 --- a/theories7/ZArith/Zlogarithm.v +++ /dev/null @@ -1,272 +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: Zlogarithm.v,v 1.1.2.1 2004/07/16 19:31:43 herbelin Exp $ i*) - -(**********************************************************************) -(** The integer logarithms with base 2. - - There are three logarithms, - depending on the rounding of the real 2-based logarithm: - - [Log_inf]: [y = (Log_inf x) iff 2^y <= x < 2^(y+1)] - i.e. [Log_inf x] is the biggest integer that is smaller than [Log x] - - [Log_sup]: [y = (Log_sup x) iff 2^(y-1) < x <= 2^y] - i.e. [Log_inf x] is the smallest integer that is bigger than [Log x] - - [Log_nearest]: [y= (Log_nearest x) iff 2^(y-1/2) < x <= 2^(y+1/2)] - i.e. [Log_nearest x] is the integer nearest from [Log x] *) - -Require ZArith_base. -Require Omega. -Require Zcomplements. -Require Zpower. -V7only [Import Z_scope.]. -Open Local Scope Z_scope. - -Section Log_pos. (* Log of positive integers *) - -(** First we build [log_inf] and [log_sup] *) - -Fixpoint log_inf [p:positive] : Z := - Cases p of - xH => `0` (* 1 *) - | (xO q) => (Zs (log_inf q)) (* 2n *) - | (xI q) => (Zs (log_inf q)) (* 2n+1 *) - end. -Fixpoint log_sup [p:positive] : Z := - Cases p of - xH => `0` (* 1 *) - | (xO n) => (Zs (log_sup n)) (* 2n *) - | (xI n) => (Zs (Zs (log_inf n))) (* 2n+1 *) - end. - -Hints Unfold log_inf log_sup. - -(** Then we give the specifications of [log_inf] and [log_sup] - and prove their validity *) - -(*i Hints Resolve ZERO_le_S : zarith. i*) -Hints Resolve Zle_trans : zarith. - -Theorem log_inf_correct : (x:positive) ` 0 <= (log_inf x)` /\ - ` (two_p (log_inf x)) <= (POS x) < (two_p (Zs (log_inf x)))`. -Induction x; Intros; Simpl; -[ Elim H; Intros Hp HR; Clear H; Split; - [ Auto with zarith - | Conditional (Apply Zle_le_S; Trivial) Rewrite two_p_S with x:=(Zs (log_inf p)); - Conditional Trivial Rewrite two_p_S; - Conditional Trivial Rewrite two_p_S in HR; - Rewrite (POS_xI p); Omega ] -| Elim H; Intros Hp HR; Clear H; Split; - [ Auto with zarith - | Conditional (Apply Zle_le_S; Trivial) Rewrite two_p_S with x:=(Zs (log_inf p)); - Conditional Trivial Rewrite two_p_S; - Conditional Trivial Rewrite two_p_S in HR; - Rewrite (POS_xO p); Omega ] -| Unfold two_power_pos; Unfold shift_pos; Simpl; Omega -]. -Qed. - -Definition log_inf_correct1 := - [p:positive](proj1 ? ? (log_inf_correct p)). -Definition log_inf_correct2 := - [p:positive](proj2 ? ? (log_inf_correct p)). - -Opaque log_inf_correct1 log_inf_correct2. - -Hints Resolve log_inf_correct1 log_inf_correct2 : zarith. - -Lemma log_sup_correct1 : (p:positive)` 0 <= (log_sup p)`. -Induction p; Intros; Simpl; Auto with zarith. -Qed. - -(** For every [p], either [p] is a power of two and [(log_inf p)=(log_sup p)] - either [(log_sup p)=(log_inf p)+1] *) - -Theorem log_sup_log_inf : (p:positive) - IF (POS p)=(two_p (log_inf p)) - then (POS p)=(two_p (log_sup p)) - else ` (log_sup p)=(Zs (log_inf p))`. - -Induction p; Intros; -[ Elim H; Right; Simpl; - Rewrite (two_p_S (log_inf p0) (log_inf_correct1 p0)); - Rewrite POS_xI; Unfold Zs; Omega -| Elim H; Clear H; Intro Hif; - [ Left; Simpl; - Rewrite (two_p_S (log_inf p0) (log_inf_correct1 p0)); - Rewrite (two_p_S (log_sup p0) (log_sup_correct1 p0)); - Rewrite <- (proj1 ? ? Hif); Rewrite <- (proj2 ? ? Hif); - Auto - | Right; Simpl; - Rewrite (two_p_S (log_inf p0) (log_inf_correct1 p0)); - Rewrite POS_xO; Unfold Zs; Omega ] -| Left; Auto ]. -Qed. - -Theorem log_sup_correct2 : (x:positive) - ` (two_p (Zpred (log_sup x))) < (POS x) <= (two_p (log_sup x))`. - -Intro. -Elim (log_sup_log_inf x). -(* x is a power of two and [log_sup = log_inf] *) -Intros (E1,E2); Rewrite E2. -Split ; [ Apply two_p_pred; Apply log_sup_correct1 | Apply Zle_n ]. -Intros (E1,E2); Rewrite E2. -Rewrite <- (Zpred_Sn (log_inf x)). -Generalize (log_inf_correct2 x); Omega. -Qed. - -Lemma log_inf_le_log_sup : - (p:positive) `(log_inf p) <= (log_sup p)`. -Induction p; Simpl; Intros; Omega. -Qed. - -Lemma log_sup_le_Slog_inf : - (p:positive) `(log_sup p) <= (Zs (log_inf p))`. -Induction p; Simpl; Intros; Omega. -Qed. - -(** Now it's possible to specify and build the [Log] rounded to the nearest *) - -Fixpoint log_near[x:positive] : Z := - Cases x of - xH => `0` - | (xO xH) => `1` - | (xI xH) => `2` - | (xO y) => (Zs (log_near y)) - | (xI y) => (Zs (log_near y)) - end. - -Theorem log_near_correct1 : (p:positive)` 0 <= (log_near p)`. -Induction p; Simpl; Intros; -[Elim p0; Auto with zarith | Elim p0; Auto with zarith | Trivial with zarith ]. -Intros; Apply Zle_le_S. -Generalize H0; Elim p1; Intros; Simpl; - [ Assumption | Assumption | Apply ZERO_le_POS ]. -Intros; Apply Zle_le_S. -Generalize H0; Elim p1; Intros; Simpl; - [ Assumption | Assumption | Apply ZERO_le_POS ]. -Qed. - -Theorem log_near_correct2: (p:positive) - (log_near p)=(log_inf p) -\/(log_near p)=(log_sup p). -Induction p. -Intros p0 [Einf|Esup]. -Simpl. Rewrite Einf. -Case p0; [Left | Left | Right]; Reflexivity. -Simpl; Rewrite Esup. -Elim (log_sup_log_inf p0). -Generalize (log_inf_le_log_sup p0). -Generalize (log_sup_le_Slog_inf p0). -Case p0; Auto with zarith. -Intros; Omega. -Case p0; Intros; Auto with zarith. -Intros p0 [Einf|Esup]. -Simpl. -Repeat Rewrite Einf. -Case p0; Intros; Auto with zarith. -Simpl. -Repeat Rewrite Esup. -Case p0; Intros; Auto with zarith. -Auto. -Qed. - -(*i****************** -Theorem log_near_correct: (p:positive) - `| (two_p (log_near p)) - (POS p) | <= (POS p)-(two_p (log_inf p))` - /\`| (two_p (log_near p)) - (POS p) | <= (two_p (log_sup p))-(POS p)`. -Intro. -Induction p. -Intros p0 [(Einf1,Einf2)|(Esup1,Esup2)]. -Unfold log_near log_inf log_sup. Fold log_near log_inf log_sup. -Rewrite Einf1. -Repeat Rewrite two_p_S. -Case p0; [Left | Left | Right]. - -Split. -Simpl. -Rewrite E1; Case p0; Try Reflexivity. -Compute. -Unfold log_near; Fold log_near. -Unfold log_inf; Fold log_inf. -Repeat Rewrite E1. -Split. -**********************************i*) - -End Log_pos. - -Section divers. - -(** Number of significative digits. *) - -Definition N_digits := - [x:Z]Cases x of - (POS p) => (log_inf p) - | (NEG p) => (log_inf p) - | ZERO => `0` - end. - -Lemma ZERO_le_N_digits : (x:Z) ` 0 <= (N_digits x)`. -Induction x; Simpl; -[ Apply Zle_n -| Exact log_inf_correct1 -| Exact log_inf_correct1]. -Qed. - -Lemma log_inf_shift_nat : - (n:nat)(log_inf (shift_nat n xH))=(inject_nat n). -Induction n; Intros; -[ Try Trivial -| Rewrite -> inj_S; Rewrite <- H; Reflexivity]. -Qed. - -Lemma log_sup_shift_nat : - (n:nat)(log_sup (shift_nat n xH))=(inject_nat n). -Induction n; Intros; -[ Try Trivial -| Rewrite -> inj_S; Rewrite <- H; Reflexivity]. -Qed. - -(** [Is_power p] means that p is a power of two *) -Fixpoint Is_power[p:positive] : Prop := - Cases p of - xH => True - | (xO q) => (Is_power q) - | (xI q) => False - end. - -Lemma Is_power_correct : - (p:positive) (Is_power p) <-> (Ex [y:nat](p=(shift_nat y xH))). - -Split; -[ Elim p; - [ Simpl; Tauto - | Simpl; Intros; Generalize (H H0); Intro H1; Elim H1; Intros y0 Hy0; - Exists (S y0); Rewrite Hy0; Reflexivity - | Intro; Exists O; Reflexivity] -| Intros; Elim H; Intros; Rewrite -> H0; Elim x; Intros; Simpl; Trivial]. -Qed. - -Lemma Is_power_or : (p:positive) (Is_power p)\/~(Is_power p). -Induction p; -[ Intros; Right; Simpl; Tauto -| Intros; Elim H; - [ Intros; Left; Simpl; Exact H0 - | Intros; Right; Simpl; Exact H0] -| Left; Simpl; Trivial]. -Qed. - -End divers. - - - - - - - |