+++ /dev/null
-(**************************************************************************)
-(* ___ *)
-(* ||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/log".
-
-include "datatypes/constructors.ma".
-include "nat/exp.ma".
-include "nat/lt_arith.ma".
-include "nat/primes.ma".
-
-(* this definition of log is based on pairs, with a remainder *)
-
-let rec plog_aux p n m \def
- match (mod n m) with
- [ O \Rightarrow
- match p with
- [ O \Rightarrow pair nat nat O n
- | (S p) \Rightarrow
- match (plog_aux p (div n m) m) with
- [ (pair q r) \Rightarrow pair nat nat (S q) r]]
- | (S a) \Rightarrow pair nat nat O n].
-
-(* plog n m = <q,r> if m divides n q times, with remainder r *)
-definition plog \def \lambda n,m:nat.plog_aux n n m.
-
-theorem plog_aux_to_Prop: \forall p,n,m. O < m \to
- match plog_aux p n m with
- [ (pair q r) \Rightarrow n = m \sup q *r ].
-intro.
-elim p.
-change with
-match (
-match (mod n m) with
- [ O \Rightarrow pair nat nat O n
- | (S a) \Rightarrow pair nat nat O n] )
-with
- [ (pair q r) \Rightarrow n = m \sup q * r ].
-apply nat_case (mod n m).
-simplify.apply plus_n_O.
-intros.
-simplify.apply plus_n_O.
-change with
-match (
-match (mod n1 m) with
- [ O \Rightarrow
- match (plog_aux n (div n1 m) m) with
- [ (pair q r) \Rightarrow pair nat nat (S q) r]
- | (S a) \Rightarrow pair nat nat O n1] )
-with
- [ (pair q r) \Rightarrow n1 = m \sup q * r].
-apply nat_case1 (mod n1 m).intro.
-change with
-match (
- match (plog_aux n (div n1 m) m) with
- [ (pair q r) \Rightarrow pair nat nat (S q) r])
-with
- [ (pair q r) \Rightarrow n1 = m \sup q * r].
-generalize in match (H (div n1 m) m).
-elim plog_aux n (div n1 m) m.
-simplify.
-rewrite > assoc_times.
-rewrite < H3.rewrite > plus_n_O (m*(div n1 m)).
-rewrite < H2.
-rewrite > sym_times.
-rewrite < div_mod.reflexivity.
-assumption.assumption.
-intros.simplify.apply plus_n_O.
-qed.
-
-theorem plog_aux_to_exp: \forall p,n,m,q,r. O < m \to
- (pair nat nat q r) = plog_aux p n m \to n = m \sup q * r.
-intros.
-change with
-match (pair nat nat q r) with
- [ (pair q r) \Rightarrow n = m \sup q * r ].
-rewrite > H1.
-apply plog_aux_to_Prop.
-assumption.
-qed.
-(* questo va spostato in primes1.ma *)
-theorem plog_exp: \forall n,m,i. O < m \to mod n m \neq O \to
-\forall p. i \le p \to plog_aux p (m \sup i * n) m = pair nat nat i n.
-intros 5.
-elim i.
-simplify.
-rewrite < plus_n_O.
-apply nat_case p.
-change with
- match (mod n m) with
- [ O \Rightarrow pair nat nat O n
- | (S a) \Rightarrow pair nat nat O n]
- = pair nat nat O n.
-elim (mod n m).simplify.reflexivity.simplify.reflexivity.
-intro.
-change with
- match (mod n m) with
- [ O \Rightarrow
- match (plog_aux m1 (div n m) m) with
- [ (pair q r) \Rightarrow pair nat nat (S q) r]
- | (S a) \Rightarrow pair nat nat O n]
- = pair nat nat O n.
-cut O < mod n m \lor O = mod n m.
-elim Hcut.apply lt_O_n_elim (mod n m) H3.
-intros. simplify.reflexivity.
-apply False_ind.
-apply H1.apply sym_eq.assumption.
-apply le_to_or_lt_eq.apply le_O_n.
-generalize in match H3.
-apply nat_case p.intro.apply False_ind.apply not_le_Sn_O n1 H4.
-intros.
-change with
- match (mod (m \sup (S n1) *n) m) with
- [ O \Rightarrow
- match (plog_aux m1 (div (m \sup (S n1) *n) m) m) with
- [ (pair q r) \Rightarrow pair nat nat (S q) r]
- | (S a) \Rightarrow pair nat nat O (m \sup (S n1) *n)]
- = pair nat nat (S n1) n.
-cut (mod (m \sup (S n1)*n) m) = O.
-rewrite > Hcut.
-change with
-match (plog_aux m1 (div (m \sup (S n1)*n) m) m) with
- [ (pair q r) \Rightarrow pair nat nat (S q) r]
- = pair nat nat (S n1) n.
-cut div (m \sup (S n1) *n) m = m \sup n1 *n.
-rewrite > Hcut1.
-rewrite > H2 m1. simplify.reflexivity.
-apply le_S_S_to_le.assumption.
-(* div_exp *)
-change with div (m* m \sup n1 *n) m = m \sup n1 * n.
-rewrite > assoc_times.
-apply lt_O_n_elim m H.
-intro.apply div_times.
-(* mod_exp = O *)
-apply divides_to_mod_O.
-assumption.
-simplify.rewrite > assoc_times.
-apply witness ? ? (m \sup n1 *n).reflexivity.
-qed.
-
-theorem plog_aux_to_Prop1: \forall p,n,m. (S O) < m \to O < n \to n \le p \to
- match plog_aux p n m with
- [ (pair q r) \Rightarrow mod r m \neq O].
-intro.elim p.absurd O < n.assumption.
-apply le_to_not_lt.assumption.
-change with
-match
- (match (mod n1 m) with
- [ O \Rightarrow
- match (plog_aux n(div n1 m) m) with
- [ (pair q r) \Rightarrow pair nat nat (S q) r]
- | (S a) \Rightarrow pair nat nat O n1])
-with
- [ (pair q r) \Rightarrow mod r m \neq O].
-apply nat_case1 (mod n1 m).intro.
-generalize in match (H (div n1 m) m).
-elim (plog_aux n (div n1 m) m).
-apply H5.assumption.
-apply eq_mod_O_to_lt_O_div.
-apply trans_lt ? (S O).simplify.apply le_n.
-assumption.assumption.assumption.
-apply le_S_S_to_le.
-apply trans_le ? n1.change with div n1 m < n1.
-apply lt_div_n_m_n.assumption.assumption.assumption.
-intros.
-change with mod n1 m \neq O.
-rewrite > H4.
-(* Andrea: META NOT FOUND !!!
-rewrite > sym_eq. *)
-simplify.intro.
-apply not_eq_O_S m1.
-rewrite > H5.reflexivity.
-qed.
-
-theorem plog_aux_to_not_mod_O: \forall p,n,m,q,r. (S O) < m \to O < n \to n \le p \to
- pair nat nat q r = plog_aux p n m \to mod r m \neq O.
-intros.
-change with
- match (pair nat nat q r) with
- [ (pair q r) \Rightarrow mod r m \neq O].
-rewrite > H3.
-apply plog_aux_to_Prop1.
-assumption.assumption.assumption.
-qed.
-
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