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Diffstat (limited to 'coqprime-8.4/Coqprime/Iterator.v')
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diff --git a/coqprime-8.4/Coqprime/Iterator.v b/coqprime-8.4/Coqprime/Iterator.v new file mode 100644 index 000000000..e84687cd4 --- /dev/null +++ b/coqprime-8.4/Coqprime/Iterator.v @@ -0,0 +1,180 @@ + +(*************************************************************) +(* This file is distributed under the terms of the *) +(* GNU Lesser General Public License Version 2.1 *) +(*************************************************************) +(* Benjamin.Gregoire@inria.fr Laurent.Thery@inria.fr *) +(*************************************************************) + +Require Export Coq.Lists.List. +Require Export Coqprime.Permutation. +Require Import Coq.Arith.Arith. + +Section Iterator. +Variables A B : Set. +Variable zero : B. +Variable f : A -> B. +Variable g : B -> B -> B. +Hypothesis g_zero : forall a, g a zero = a. +Hypothesis g_trans : forall a b c, g a (g b c) = g (g a b) c. +Hypothesis g_sym : forall a b, g a b = g b a. + +Definition iter := fold_right (fun a r => g (f a) r) zero. +Hint Unfold iter . + +Theorem iter_app: forall l1 l2, iter (app l1 l2) = g (iter l1) (iter l2). +intros l1; elim l1; simpl; auto. +intros l2; rewrite g_sym; auto. +intros a l H l2; rewrite H. +rewrite g_trans; auto. +Qed. + +Theorem iter_permutation: forall l1 l2, permutation l1 l2 -> iter l1 = iter l2. +intros l1 l2 H; elim H; simpl; auto; clear H l1 l2. +intros a l1 l2 H1 H2; apply f_equal2 with ( f := g ); auto. +intros a b l; (repeat rewrite g_trans). +apply f_equal2 with ( f := g ); auto. +intros l1 l2 l3 H H0 H1 H2; apply trans_equal with ( 1 := H0 ); auto. +Qed. + +Lemma iter_inv: + forall P l, + P zero -> + (forall a b, P a -> P b -> P (g a b)) -> + (forall x, In x l -> P (f x)) -> P (iter l). +intros P l H H0; (elim l; simpl; auto). +Qed. +Variable next : A -> A. + +Fixpoint progression (m : A) (n : nat) {struct n} : list A := + match n with 0 => nil + | S n1 => cons m (progression (next m) n1) end. + +Fixpoint next_n (c : A) (n : nat) {struct n} : A := + match n with 0 => c | S n1 => next_n (next c) n1 end. + +Theorem progression_app: + forall a b n m, + le m n -> + b = next_n a m -> + progression a n = app (progression a m) (progression b (n - m)). +intros a b n m; generalize a b n; clear a b n; elim m; clear m; simpl. +intros a b n H H0; apply f_equal2 with ( f := progression ); auto with arith. +intros m H a b n; case n; simpl; clear n. +intros H1; absurd (0 < 1 + m); auto with arith. +intros n H0 H1; apply f_equal2 with ( f := @cons A ); auto with arith. +Qed. + +Let iter_progression := fun m n => iter (progression m n). + +Theorem iter_progression_app: + forall a b n m, + le m n -> + b = next_n a m -> + iter (progression a n) = + g (iter (progression a m)) (iter (progression b (n - m))). +intros a b n m H H0; unfold iter_progression; rewrite (progression_app a b n m); + (try apply iter_app); auto. +Qed. + +Theorem length_progression: forall z n, length (progression z n) = n. +intros z n; generalize z; elim n; simpl; auto. +Qed. + +End Iterator. +Implicit Arguments iter [A B]. +Implicit Arguments progression [A]. +Implicit Arguments next_n [A]. +Hint Unfold iter . +Hint Unfold progression . +Hint Unfold next_n . + +Theorem iter_ext: + forall (A B : Set) zero (f1 : A -> B) f2 g l, + (forall a, In a l -> f1 a = f2 a) -> iter zero f1 g l = iter zero f2 g l. +intros A B zero f1 f2 g l; elim l; simpl; auto. +intros a l0 H H0; apply f_equal2 with ( f := g ); auto. +Qed. + +Theorem iter_map: + forall (A B C : Set) zero (f : B -> C) g (k : A -> B) l, + iter zero f g (map k l) = iter zero (fun x => f (k x)) g l. +intros A B C zero f g k l; elim l; simpl; auto. +intros; apply f_equal2 with ( f := g ); auto with arith. +Qed. + +Theorem iter_comp: + forall (A B : Set) zero (f1 f2 : A -> B) g l, + (forall a, g a zero = a) -> + (forall a b c, g a (g b c) = g (g a b) c) -> + (forall a b, g a b = g b a) -> + g (iter zero f1 g l) (iter zero f2 g l) = + iter zero (fun x => g (f1 x) (f2 x)) g l. +intros A B zero f1 f2 g l g_zero g_trans g_sym; elim l; simpl; auto. +intros a l0 H; rewrite <- H; (repeat rewrite <- g_trans). +apply f_equal2 with ( f := g ); auto. +(repeat rewrite g_trans); apply f_equal2 with ( f := g ); auto. +Qed. + +Theorem iter_com: + forall (A B : Set) zero (f : A -> A -> B) g l1 l2, + (forall a, g a zero = a) -> + (forall a b c, g a (g b c) = g (g a b) c) -> + (forall a b, g a b = g b a) -> + iter zero (fun x => iter zero (fun y => f x y) g l1) g l2 = + iter zero (fun y => iter zero (fun x => f x y) g l2) g l1. +intros A B zero f g l1 l2 H H0 H1; generalize l2; elim l1; simpl; auto; + clear l1 l2. +intros l2; elim l2; simpl; auto with arith. +intros; rewrite H1; rewrite H; auto with arith. +intros a l1 H2 l2; case l2; clear l2; simpl; auto. +elim l1; simpl; auto with arith. +intros; rewrite H1; rewrite H; auto with arith. +intros b l2. +rewrite <- (iter_comp + _ _ zero (fun x => f x a) + (fun x => iter zero (fun (y : A) => f x y) g l1)); auto with arith. +rewrite <- (iter_comp + _ _ zero (fun y => f b y) + (fun y => iter zero (fun (x : A) => f x y) g l2)); auto with arith. +(repeat rewrite H0); auto. +apply f_equal2 with ( f := g ); auto. +(repeat rewrite <- H0); auto. +apply f_equal2 with ( f := g ); auto. +Qed. + +Theorem iter_comp_const: + forall (A B : Set) zero (f : A -> B) g k l, + k zero = zero -> + (forall a b, k (g a b) = g (k a) (k b)) -> + k (iter zero f g l) = iter zero (fun x => k (f x)) g l. +intros A B zero f g k l H H0; elim l; simpl; auto. +intros a l0 H1; rewrite H0; apply f_equal2 with ( f := g ); auto. +Qed. + +Lemma next_n_S: forall n m, next_n S n m = plus n m. +intros n m; generalize n; elim m; clear n m; simpl; auto with arith. +intros m H n; case n; simpl; auto with arith. +rewrite H; auto with arith. +intros n1; rewrite H; simpl; auto with arith. +Qed. + +Theorem progression_S_le_init: + forall n m p, In p (progression S n m) -> le n p. +intros n m; generalize n; elim m; clear n m; simpl; auto. +intros; contradiction. +intros m H n p [H1|H1]; auto with arith. +subst n; auto. +apply le_S_n; auto with arith. +Qed. + +Theorem progression_S_le_end: + forall n m p, In p (progression S n m) -> lt p (n + m). +intros n m; generalize n; elim m; clear n m; simpl; auto. +intros; contradiction. +intros m H n p [H1|H1]; auto with arith. +subst n; auto with arith. +rewrite <- plus_n_Sm; auto with arith. +rewrite <- plus_n_Sm; auto with arith. +generalize (H (S n) p); auto with arith. +Qed. |