From: Andrea Asperti Date: Mon, 3 Oct 2005 08:16:18 +0000 (+0000) Subject: Added congruence.ma. X-Git-Tag: V_0_7_2_3~262 X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=commitdiff_plain;h=b2565147ddbf4f9c3baf37359ad0f6330903b4f8;p=helm.git Added congruence.ma. --- diff --git a/helm/matita/library/nat/congruence.ma b/helm/matita/library/nat/congruence.ma new file mode 100644 index 000000000..20c73b3d1 --- /dev/null +++ b/helm/matita/library/nat/congruence.ma @@ -0,0 +1,153 @@ +(**************************************************************************) +(* ___ *) +(* ||M|| *) +(* ||A|| A project by Andrea Asperti *) +(* ||T|| *) +(* ||I|| Developers: *) +(* ||T|| A.Asperti, C.Sacerdoti Coen, *) +(* ||A|| E.Tassi, S.Zacchiroli *) +(* \ / *) +(* \ / Matita is distributed under the terms of the *) +(* v GNU Lesser General Public License Version 2.1 *) +(* *) +(**************************************************************************) + +set "baseuri" "cic:/matita/nat/congruence". + +include "nat/relevant_equations.ma". +include "nat/primes.ma". + +definition S_mod: nat \to nat \to nat \def +\lambda n,m:nat. (S m) \mod n. + +definition congruent: nat \to nat \to nat \to Prop \def +\lambda n,m,p:nat. mod n p = mod m p. + +theorem congruent_n_n: \forall n,p:nat.congruent n n p. +intros.unfold congruent.reflexivity. +qed. + +theorem transitive_congruent: \forall p:nat. transitive nat +(\lambda n,m. congruent n m p). +intros.unfold transitive.unfold congruent.intros. +whd.apply trans_eq ? ? (y \mod p). +apply H.apply H1. +qed. + +theorem le_to_mod: \forall n,m:nat. n \lt m \to n = n \mod m. +intros. +apply div_mod_spec_to_eq2 n m O n (n/m) (n \mod m). +constructor 1.assumption.simplify.reflexivity. +apply div_mod_spec_div_mod. +apply le_to_lt_to_lt O n m.apply le_O_n.assumption. +qed. + +theorem mod_mod : \forall n,p:nat. O

div_mod (n \mod p) p in \vdash (? ? % ?). +rewrite > eq_div_O ? p.reflexivity. +(* uffa: hint non lo trova lt vs. le*) +apply lt_mod_m_m. +assumption. +assumption. +qed. + +theorem congruent_n_mod_n : +\forall n,p:nat. O < p \to congruent n (n \mod p) p. +intros.unfold congruent. +apply mod_mod.assumption. +qed. + +theorem eq_times_plus_to_congruent: \forall n,m,p,r:nat. O< p \to +n = r*p+m \to congruent n m p. +intros.unfold congruent. +apply div_mod_spec_to_eq2 n p (div n p) (mod n p) (r +(div m p)) (mod m p). +apply div_mod_spec_div_mod.assumption. +constructor 1. +apply lt_mod_m_m.assumption. +rewrite > sym_times. +rewrite > distr_times_plus. +rewrite > sym_times. +rewrite > sym_times p. +rewrite > assoc_plus. +rewrite < div_mod. +assumption.assumption. +qed. + +theorem divides_to_congruent: \forall n,m,p:nat. O < p \to m \le n \to +divides p (n - m) \to congruent n m p. +intros.elim H2. +apply eq_times_plus_to_congruent n m p n2. +assumption. +rewrite < sym_plus. +apply minus_to_plus.assumption. +rewrite > sym_times. assumption. +qed. + +theorem congruent_to_divides: \forall n,m,p:nat. +O < p \to congruent n m p \to divides p (n - m). +intros.unfold congruent in H1. +apply witness ? ? ((n / p)-(m / p)). +rewrite > sym_times. +rewrite > div_mod n p in \vdash (? ? % ?). +rewrite > div_mod m p in \vdash (? ? % ?). +rewrite < sym_plus (m \mod p). +rewrite < H1. +rewrite < eq_minus_minus_minus_plus ? (n \mod p). +rewrite < minus_plus_m_m. +apply sym_eq. +apply times_minus_l. +assumption.assumption. +qed. + +theorem mod_times: \forall n,m,p:nat. +O < p \to mod (n*m) p = mod ((mod n p)*(mod m p)) p. +intros. +change with congruent (n*m) ((mod n p)*(mod m p)) p. +apply eq_times_plus_to_congruent ? ? p +((n / p)*p*(m / p) + (n / p)*(m \mod p) + (n \mod p)*(m / p)). +assumption. +apply trans_eq ? ? (((n/p)*p+(n \mod p))*((m/p)*p+(m \mod p))). +apply eq_f2. +apply div_mod.assumption. +apply div_mod.assumption. +apply trans_eq ? ? (((n/p)*p)*((m/p)*p) + (n/p)*p*(m \mod p) + +(n \mod p)*((m / p)*p) + (n \mod p)*(m \mod p)). +apply times_plus_plus. +apply eq_f2. +rewrite < assoc_times. +rewrite > assoc_times (n/p) p (m \mod p). +rewrite > sym_times p (m \mod p). +rewrite < assoc_times (n/p) (m \mod p) p. +rewrite < times_plus_l. +rewrite < assoc_times (n \mod p). +rewrite < times_plus_l. +apply eq_f2. +apply eq_f2.reflexivity. +reflexivity.reflexivity. +reflexivity. +qed. + +theorem congruent_times: \forall n,m,n1,m1,p. O < p \to congruent n n1 p \to +congruent m m1 p \to congruent (n*m) (n1*m1) p. +unfold congruent. +intros. +rewrite > mod_times n m p H. +rewrite > H1. +rewrite > H2. +apply sym_eq. +apply mod_times.assumption. +qed. + +theorem congruent_pi: \forall f:nat \to nat. \forall n,m,p:nat.O < p \to +congruent (pi n f m) (pi n (\lambda m. mod (f m) p) m) p. +intros. +elim n.change with congruent (f m) (f m \mod p) p. +apply congruent_n_mod_n.assumption. +change with congruent ((f (S n1+m))*(pi n1 f m)) +(((f (S n1+m))\mod p)*(pi n1 (\lambda m.(f m) \mod p) m)) p. +apply congruent_times. +assumption. +apply congruent_n_mod_n.assumption. +assumption. +qed. \ No newline at end of file