1 (**************************************************************************)
4 (* ||A|| A project by Andrea Asperti *)
6 (* ||I|| Developers: *)
7 (* ||T|| A.Asperti, C.Sacerdoti Coen, *)
8 (* ||A|| E.Tassi, S.Zacchiroli *)
10 (* \ / This file is distributed under the terms of the *)
11 (* v GNU Lesser General Public License Version 2.1 *)
13 (**************************************************************************)
15 (* include "higher_order_defs/functions.ma". *)
16 include "hints_declaration.ma".
17 include "basics/functions.ma".
18 include "basics/eq.ma".
20 ninductive nat : Type[0] ≝
24 interpretation "Natural numbers" 'N = nat.
26 alias num (instance 0) = "nnatural number".
30 {n:>nat; is_pos: n ≠ 0}.
32 ncoercion nat_to_pos: ∀n:nat. n ≠0 →pos ≝ mk_pos on
35 (* default "natural numbers" cic:/matita/ng/arithmetics/nat/nat.ind.
39 λn. match n with [ O ⇒ O | (S p) ⇒ p].
41 ntheorem pred_Sn : ∀n. n = pred (S n).
44 ntheorem injective_S : injective nat nat S.
48 ntheorem inj_S : \forall n,m:nat.(S n)=(S m) \to n=m.
51 ntheorem not_eq_S: ∀n,m:nat. n ≠ m → S n ≠ S m.
54 ndefinition not_zero: nat → Prop ≝
56 [ O ⇒ False | (S p) ⇒ True ].
58 ntheorem not_eq_O_S : ∀n:nat. O ≠ S n.
59 #n; #eqOS; nchange with (not_zero O); nrewrite > eqOS; //.
62 ntheorem not_eq_n_Sn : ∀n:nat. n ≠ S n.
63 #n; nelim n; /2/; nqed.
67 (n=O → P O) → (∀m:nat. (n=(S m) → P (S m))) → P n.
68 #n; #P; nelim n; /2/; nqed.
74 → (∀n,m:nat. R n m → R (S n) (S m))
76 #R; #ROn; #RSO; #RSS; #n; nelim n;//;
77 #n0; #Rn0m; #m; ncases m;/2/; nqed.
79 ntheorem decidable_eq_nat : ∀n,m:nat.decidable (n=m).
83 ##| #m; #Hind; ncases Hind; /3/;
87 (*************************** plus ******************************)
92 | S p ⇒ S (plus p m) ].
94 interpretation "natural plus" 'plus x y = (plus x y).
96 ntheorem plus_O_n: ∀n:nat. n = 0+n.
100 ntheorem plus_Sn_m: ∀n,m:nat. S (n + m) = S n + m.
104 ntheorem plus_n_O: ∀n:nat. n = n+0.
105 #n; nelim n; nnormalize; //; nqed.
107 ntheorem plus_n_Sm : ∀n,m:nat. S (n+m) = n + S m.
108 #n; nelim n; nnormalize; //; nqed.
111 ntheorem plus_Sn_m1: ∀n,m:nat. S m + n = n + S m.
112 #n; nelim n; nnormalize; //; nqed.
116 ntheorem plus_n_SO : ∀n:nat. S n = n+S O.
119 ntheorem symmetric_plus: symmetric ? plus.
120 #n; nelim n; nnormalize; //; nqed.
122 ntheorem associative_plus : associative nat plus.
123 #n; nelim n; nnormalize; //; nqed.
125 ntheorem assoc_plus1: ∀a,b,c. c + (b + a) = b + c + a.
128 ntheorem injective_plus_r: ∀n:nat.injective nat nat (λm.n+m).
129 #n; nelim n; nnormalize; /3/; nqed.
131 (* ntheorem inj_plus_r: \forall p,n,m:nat. p+n = p+m \to n=m
132 \def injective_plus_r.
134 ntheorem injective_plus_l: ∀m:nat.injective nat nat (λn.n+m).
137 (* ntheorem inj_plus_l: \forall p,n,m:nat. n+p = m+p \to n=m
138 \def injective_plus_l. *)
140 (*************************** times *****************************)
145 | S p ⇒ m+(times p m) ].
147 interpretation "natural times" 'times x y = (times x y).
149 ntheorem times_Sn_m: ∀n,m:nat. m+n*m = S n*m.
152 ntheorem times_O_n: ∀n:nat. O = O*n.
155 ntheorem times_n_O: ∀n:nat. O = n*O.
156 #n; nelim n; //; nqed.
158 ntheorem times_n_Sm : ∀n,m:nat. n+(n*m) = n*(S m).
159 #n; nelim n; nnormalize; //; nqed.
161 ntheorem symmetric_times : symmetric nat times.
162 #n; nelim n; nnormalize; //; nqed.
164 (* variant sym_times : \forall n,m:nat. n*m = m*n \def
167 ntheorem distributive_times_plus : distributive nat times plus.
168 #n; nelim n; nnormalize; //; nqed.
170 ntheorem distributive_times_plus_r:
171 \forall a,b,c:nat. (b+c)*a = b*a + c*a.
174 ntheorem associative_times: associative nat times.
175 #n; nelim n; nnormalize; //; nqed.
177 nlemma times_times: ∀x,y,z. x*(y*z) = y*(x*z).
180 (* ci servono questi risultati?
181 ntheorem times_O_to_O: ∀n,m:nat.n*m=O → n=O ∨ m=O.
182 napply nat_elim2; /2/;
183 #n; #m; #H; nnormalize; #H1; napply False_ind;napply not_eq_O_S;
186 ntheorem times_n_SO : ∀n:nat. n = n * S O.
189 ntheorem times_SSO_n : ∀n:nat. n + n = (S(S O)) * n.
190 nnormalize; //; nqed.
192 nlemma times_SSO: \forall n.(S(S O))*(S n) = S(S((S(S O))*n)).
195 ntheorem or_eq_eq_S: \forall n.\exists m.
196 n = (S(S O))*m \lor n = S ((S(S O))*m).
199 ##|#a; #H; nelim H; #b;#or;nelim or;#aeq;
201 ##|@ (S b); @ 1; /2/;
206 (******************** ordering relations ************************)
208 ninductive le (n:nat) : nat → Prop ≝
210 | le_S : ∀ m:nat. le n m → le n (S m).
212 interpretation "natural 'less or equal to'" 'leq x y = (le x y).
214 interpretation "natural 'neither less nor equal to'" 'nleq x y = (Not (le x y)).
216 ndefinition lt: nat → nat → Prop ≝
219 interpretation "natural 'less than'" 'lt x y = (lt x y).
221 interpretation "natural 'not less than'" 'nless x y = (Not (lt x y)).
223 (* nlemma eq_lt: ∀n,m. (n < m) = (S n ≤ m).
226 ndefinition ge: nat \to nat \to Prop \def
227 \lambda n,m:nat.m \leq n.
229 interpretation "natural 'greater or equal to'" 'geq x y = (ge x y).
231 ndefinition gt: nat \to nat \to Prop \def
234 interpretation "natural 'greater than'" 'gt x y = (gt x y).
236 interpretation "natural 'not greater than'" 'ngtr x y = (Not (gt x y)).
238 ntheorem transitive_le : transitive nat le.
239 #a; #b; #c; #leab; #lebc;nelim lebc;/2/;
243 ntheorem trans_le: \forall n,m,p:nat. n \leq m \to m \leq p \to n \leq p
244 \def transitive_le. *)
247 naxiom transitive_lt: transitive nat lt.
248 (* #a; #b; #c; #ltab; #ltbc;nelim ltbc;/2/;nqed.*)
251 theorem trans_lt: \forall n,m,p:nat. lt n m \to lt m p \to lt n p
252 \def transitive_lt. *)
254 ntheorem le_S_S: ∀n,m:nat. n ≤ m → S n ≤ S m.
255 #n; #m; #lenm; nelim lenm; /2/; nqed.
257 ntheorem le_O_n : ∀n:nat. O ≤ n.
258 #n; nelim n; /2/; nqed.
260 ntheorem le_n_Sn : ∀n:nat. n ≤ S n.
263 ntheorem le_pred_n : ∀n:nat. pred n ≤ n.
264 #n; nelim n; //; nqed.
266 (* XXX global problem *)
267 nlemma my_trans_le : ∀x,y,z:nat.x ≤ y → y ≤ z → x ≤ z.
268 napply transitive_le.
271 ntheorem monotonic_pred: monotonic ? le pred.
272 #n; #m; #lenm; nelim lenm; /2/; nqed.
274 ntheorem le_S_S_to_le: ∀n,m:nat. S n ≤ S m → n ≤ m.
275 (* XXX *) nletin hint ≝ monotonic. /2/; nqed.
277 ntheorem lt_S_S_to_lt: ∀n,m. S n < S m → n < m.
280 ntheorem lt_to_lt_S_S: ∀n,m. n < m → S n < S m.
283 ntheorem lt_to_not_zero : ∀n,m:nat. n < m → not_zero m.
284 #n; #m; #Hlt; nelim Hlt;//; nqed.
287 ntheorem not_le_Sn_O: ∀ n:nat. S n ≰ O.
288 #n; #Hlen0; napply (lt_to_not_zero ?? Hlen0); nqed.
290 ntheorem not_le_to_not_le_S_S: ∀ n,m:nat. n ≰ m → S n ≰ S m.
293 ntheorem not_le_S_S_to_not_le: ∀ n,m:nat. S n ≰ S m → n ≰ m.
296 ntheorem decidable_le: ∀n,m. decidable (n≤m).
297 napply nat_elim2; #n; /3/;
298 #m; #dec; ncases dec;/4/; nqed.
300 ntheorem decidable_lt: ∀n,m. decidable (n < m).
301 #n; #m; napply decidable_le ; nqed.
303 ntheorem not_le_Sn_n: ∀n:nat. S n ≰ n.
304 #n; nelim n; /3/; nqed.
306 ntheorem lt_S_to_le: ∀n,m:nat. n < S m → n ≤ m.
309 ntheorem not_le_to_lt: ∀n,m. n ≰ m → m < n.
310 napply nat_elim2; #n;
311 ##[#abs; napply False_ind;/2/;
313 ##|#m;#Hind;#HnotleSS; napply lt_to_lt_S_S;/4/;
317 ntheorem lt_to_not_le: ∀n,m. n < m → m ≰ n.
318 #n; #m; #Hltnm; nelim Hltnm;/3/; nqed.
320 ntheorem not_lt_to_le: ∀n,m:nat. n ≮ m → m ≤ n.
321 #n; #m; #Hnlt; napply lt_S_to_le;
322 (* something strange here: /2/ fails:
323 we need an extra depths for unfolding not *)
324 napply not_le_to_lt; napply Hnlt; nqed.
326 ntheorem le_to_not_lt: ∀n,m:nat. n ≤ m → m ≮ n.
329 (* lt and le trans *)
331 ntheorem lt_to_le_to_lt: ∀n,m,p:nat. n < m → m ≤ p → n < p.
332 #n; #m; #p; #H; #H1; nelim H1; /2/; nqed.
334 ntheorem le_to_lt_to_lt: ∀n,m,p:nat. n ≤ m → m < p → n < p.
335 #n; #m; #p; #H; nelim H; /3/; nqed.
337 ntheorem lt_S_to_lt: ∀n,m. S n < m → n < m.
340 ntheorem ltn_to_ltO: ∀n,m:nat. n < m → O < m.
344 theorem lt_SO_n_to_lt_O_pred_n: \forall n:nat.
345 (S O) \lt n \to O \lt (pred n).
347 apply (ltn_to_ltO (pred (S O)) (pred n) ?).
348 apply (lt_pred (S O) n);
354 ntheorem lt_O_n_elim: ∀n:nat. O < n →
355 ∀P:nat → Prop.(∀m:nat.P (S m)) → P n.
356 #n; nelim n; //; #abs; napply False_ind; /2/; nqed.
359 theorem lt_pred: \forall n,m.
360 O < n \to n < m \to pred n < pred m.
362 [intros.apply False_ind.apply (not_le_Sn_O ? H)
363 |intros.apply False_ind.apply (not_le_Sn_O ? H1)
364 |intros.simplify.unfold.apply le_S_S_to_le.assumption
368 theorem S_pred: \forall n:nat.lt O n \to eq nat n (S (pred n)).
369 intro.elim n.apply False_ind.exact (not_le_Sn_O O H).
370 apply eq_f.apply pred_Sn.
373 theorem le_pred_to_le:
374 ∀n,m. O < m → pred n ≤ pred m → n ≤ m.
379 rewrite > (S_pred m);
390 ntheorem le_to_or_lt_eq: ∀n,m:nat. n ≤ m → n < m ∨ n = m.
391 #n; #m; #lenm; nelim lenm; /3/; nqed.
394 ntheorem lt_to_not_eq : ∀n,m:nat. n < m → n ≠ m.
398 ntheorem eq_to_not_lt: ∀a,b:nat. a = b → a ≮ b.
403 apply (lt_to_not_eq b b)
409 theorem lt_n_m_to_not_lt_m_Sn: ∀n,m. n < m → m ≮ S n.
415 generalize in match (le_S_S ? ? H);
417 generalize in match (transitive_le ? ? ? H2 H1);
419 apply (not_le_Sn_n ? H3).
422 ntheorem not_eq_to_le_to_lt: ∀n,m. n≠m → n≤m → n<m.
423 #n; #m; #Hneq; #Hle; ncases (le_to_or_lt_eq ?? Hle); //;
424 #Heq; nelim (Hneq Heq); nqed.
427 ntheorem le_n_O_to_eq : ∀n:nat. n ≤ O → O=n.
428 #n; ncases n; //; #a ; #abs; nelim (not_le_Sn_O ? abs); nqed.
430 ntheorem le_n_O_elim: ∀n:nat. n ≤ O → ∀P: nat →Prop. P O → P n.
431 #n; ncases n; //; #a; #abs; nelim (not_le_Sn_O ? abs); nqed.
433 ntheorem le_n_Sm_elim : ∀n,m:nat.n ≤ S m →
434 ∀P:Prop. (S n ≤ S m → P) → (n=S m → P) → P.
435 #n; #m; #Hle; #P; nelim Hle; /3/; nqed.
439 ntheorem le_to_le_to_eq: ∀n,m. n ≤ m → m ≤ n → n = m.
440 napply nat_elim2; /4/; nqed.
442 ntheorem lt_O_S : ∀n:nat. O < S n.
446 (* other abstract properties *)
447 theorem antisymmetric_le : antisymmetric nat le.
448 unfold antisymmetric.intros 2.
449 apply (nat_elim2 (\lambda n,m.(n \leq m \to m \leq n \to n=m))).
450 intros.apply le_n_O_to_eq.assumption.
451 intros.apply False_ind.apply (not_le_Sn_O ? H).
452 intros.apply eq_f.apply H.
453 apply le_S_S_to_le.assumption.
454 apply le_S_S_to_le.assumption.
457 theorem antisym_le: \forall n,m:nat. n \leq m \to m \leq n \to n=m
458 \def antisymmetric_le.
460 theorem le_n_m_to_lt_m_Sn_to_eq_n_m: ∀n,m. n ≤ m → m < S n → n=m.
463 generalize in match (le_S_S_to_le ? ? H1);
470 (* well founded induction principles *)
472 ntheorem nat_elim1 : ∀n:nat.∀P:nat → Prop.
473 (∀m.(∀p. p < m → P p) → P m) → P n.
475 ncut (∀q:nat. q ≤ n → P q);/2/;
477 ##[#q; #HleO; (* applica male *)
478 napply (le_n_O_elim ? HleO);
480 napply False_ind; /2/;
481 ##|#p; #Hind; #q; #HleS;
482 napply H; #a; #lta; napply Hind;
483 napply le_S_S_to_le;/2/;
487 (* some properties of functions *)
489 definition increasing \def \lambda f:nat \to nat.
490 \forall n:nat. f n < f (S n).
492 theorem increasing_to_monotonic: \forall f:nat \to nat.
493 increasing f \to monotonic nat lt f.
494 unfold monotonic.unfold lt.unfold increasing.unfold lt.intros.elim H1.apply H.
495 apply (trans_le ? (f n1)).
496 assumption.apply (trans_le ? (S (f n1))).
501 theorem le_n_fn: \forall f:nat \to nat. (increasing f)
502 \to \forall n:nat. n \le (f n).
505 apply (trans_le ? (S (f n1))).
506 apply le_S_S.apply H1.
507 simplify in H. unfold increasing in H.unfold lt in H.apply H.
510 theorem increasing_to_le: \forall f:nat \to nat. (increasing f)
511 \to \forall m:nat. \exists i. m \le (f i).
513 apply (ex_intro ? ? O).apply le_O_n.
515 apply (ex_intro ? ? (S a)).
516 apply (trans_le ? (S (f a))).
517 apply le_S_S.assumption.
518 simplify in H.unfold increasing in H.unfold lt in H.
522 theorem increasing_to_le2: \forall f:nat \to nat. (increasing f)
523 \to \forall m:nat. (f O) \le m \to
524 \exists i. (f i) \le m \land m <(f (S i)).
526 apply (ex_intro ? ? O).
527 split.apply le_n.apply H.
529 cut ((S n1) < (f (S a)) \lor (S n1) = (f (S a))).
531 apply (ex_intro ? ? a).
532 split.apply le_S. assumption.assumption.
533 apply (ex_intro ? ? (S a)).
534 split.rewrite < H7.apply le_n.
537 apply le_to_or_lt_eq.apply H6.
541 (*********************** monotonicity ***************************)
542 ntheorem monotonic_le_plus_r:
543 ∀n:nat.monotonic nat le (λm.n + m).
544 #n; #a; #b; nelim n; nnormalize; //;
545 #m; #H; #leab;napply le_S_S; /2/; nqed.
548 ntheorem le_plus_r: ∀p,n,m:nat. n ≤ m → p + n ≤ p + m
549 ≝ monotonic_le_plus_r. *)
551 ntheorem monotonic_le_plus_l:
552 ∀m:nat.monotonic nat le (λn.n + m).
556 ntheorem le_plus_l: \forall p,n,m:nat. n \le m \to n + p \le m + p
557 \def monotonic_le_plus_l. *)
559 ntheorem le_plus: ∀n1,n2,m1,m2:nat. n1 ≤ n2 \to m1 ≤ m2
561 #n1; #n2; #m1; #m2; #len; #lem; napply transitive_le;
564 ntheorem le_plus_n :∀n,m:nat. m ≤ n + m.
567 ntheorem le_plus_n_r :∀n,m:nat. m ≤ m + n.
570 ntheorem eq_plus_to_le: ∀n,m,p:nat.n=m+p → m ≤ n.
573 ntheorem le_plus_to_le: ∀a,n,m. a + n ≤ a + m → n ≤ m.
574 #a; nelim a; nnormalize; /3/; nqed.
576 ntheorem le_plus_to_le_r: ∀a,n,m. n + a ≤ m +a → n ≤ m.
581 ntheorem monotonic_lt_plus_r:
582 ∀n:nat.monotonic nat lt (λm.n+m).
586 variant lt_plus_r: \forall n,p,q:nat. p < q \to n + p < n + q \def
587 monotonic_lt_plus_r. *)
589 ntheorem monotonic_lt_plus_l:
590 ∀n:nat.monotonic nat lt (λm.m+n).
594 variant lt_plus_l: \forall n,p,q:nat. p < q \to p + n < q + n \def
595 monotonic_lt_plus_l. *)
597 ntheorem lt_plus: ∀n,m,p,q:nat. n < m → p < q → n + p < m + q.
598 #n; #m; #p; #q; #ltnm; #ltpq;
599 napply (transitive_lt ? (n+q));/2/; nqed.
601 ntheorem lt_plus_to_lt_l :∀n,p,q:nat. p+n < q+n → p<q.
604 ntheorem lt_plus_to_lt_r :∀n,p,q:nat. n+p < n+q → p<q.
607 ntheorem le_to_lt_to_plus_lt: ∀a,b,c,d:nat.
608 a ≤ c → b < d → a + b < c+d.
609 (* bello /2/ un po' lento *)
610 #a; #b; #c; #d; #leac; #lebd;
611 nnormalize; napplyS le_plus; //; nqed.
614 ntheorem monotonic_le_times_r:
615 ∀n:nat.monotonic nat le (λm. n * m).
616 #n; #x; #y; #lexy; nelim n; nnormalize;//;(* lento /2/;*)
617 #a; #lea; napply le_plus; //;
621 ntheorem le_times_r: \forall p,n,m:nat. n \le m \to p*n \le p*m
622 \def monotonic_le_times_r. *)
624 ntheorem monotonic_le_times_l:
625 ∀m:nat.monotonic nat le (λn.n*m).
629 theorem le_times_l: \forall p,n,m:nat. n \le m \to n*p \le m*p
630 \def monotonic_le_times_l. *)
632 ntheorem le_times: ∀n1,n2,m1,m2:nat.
633 n1 ≤ n2 → m1 ≤ m2 → n1*m1 ≤ n2*m2.
634 #n1; #n2; #m1; #m2; #len; #lem;
635 napply transitive_le; (* /2/ slow *)
636 ##[ ##| napply monotonic_le_times_l;//;
637 ##| napply monotonic_le_times_r;//;
641 ntheorem lt_times_n: ∀n,m:nat. O < n → m ≤ n*m.
645 ntheorem le_times_to_le:
646 ∀a,n,m. O < a → a * n ≤ a * m → n ≤ m.
647 #a; napply nat_elim2; nnormalize;
649 ##|#n; #H1; #H2; napply False_ind;
650 ngeneralize in match H2;
652 napply (transitive_le ? (S n));/2/;
653 ##|#n; #m; #H; #lta; #le;
654 napply le_S_S; napply H; /2/;
658 ntheorem le_S_times_2: ∀n,m.O < m → n ≤ m → n < 2*m.
659 #n; #m; #posm; #lenm; (* interessante *)
660 nnormalize; napplyS (le_plus n); //; nqed.
664 ntheorem lt_O_times_S_S: ∀n,m:nat.O < (S n)*(S m).
665 intros.simplify.unfold lt.apply le_S_S.apply le_O_n.
669 ntheorem lt_times_eq_O: \forall a,b:nat.
670 O < a → a * b = O → b = O.
677 rewrite > (S_pred a) in H1
679 apply (eq_to_not_lt O ((S (pred a))*(S m)))
682 | apply lt_O_times_S_S
689 theorem O_lt_times_to_O_lt: \forall a,c:nat.
690 O \lt (a * c) \to O \lt a.
702 lemma lt_times_to_lt_O: \forall i,n,m:nat. i < n*m \to O < m.
704 elim (le_to_or_lt_eq O ? (le_O_n m))
708 rewrite < times_n_O in H.
709 apply (not_le_Sn_O ? H)
714 ntheorem monotonic_lt_times_r:
715 ∀n:nat.monotonic nat lt (λm.(S n)*m).
719 simplify.rewrite < plus_n_O.rewrite < plus_n_O.assumption.
720 apply lt_plus.assumption.assumption.
723 ntheorem monotonic_lt_times_l:
724 ∀c:nat. O < c → monotonic nat lt (λt.(t*c)).
725 #c; #posc; #n; #m; #ltnm;
726 nelim ltnm; nnormalize;
727 ##[napplyS monotonic_lt_plus_l;//;
728 ##|#a; #_; #lt1; napply (transitive_le ??? lt1);//;
732 ntheorem monotonic_lt_times_r:
733 ∀c:nat. O < c → monotonic nat lt (λt.(c*t)).
735 #c; #posc; #n; #m; #ltnm;
736 (* why?? napplyS (monotonic_lt_times_l c posc n m ltnm); *)
737 nrewrite > (symmetric_times c n);
738 nrewrite > (symmetric_times c m);
739 napply monotonic_lt_times_l;//;
742 ntheorem lt_to_le_to_lt_times:
743 ∀n,m,p,q:nat. n < m → p ≤ q → O < q → n*p < m*q.
744 #n; #m; #p; #q; #ltnm; #lepq; #posq;
745 napply (le_to_lt_to_lt ? (n*q));
746 ##[napply monotonic_le_times_r;//;
747 ##|napply monotonic_lt_times_l;//;
751 ntheorem lt_times:∀n,m,p,q:nat. n<m → p<q → n*p < m*q.
752 #n; #m; #p; #q; #ltnm; #ltpq;
753 napply lt_to_le_to_lt_times;/2/;
756 ntheorem lt_times_n_to_lt_l:
757 ∀n,p,q:nat. O < n → p*n < q*n → p < q.
758 #n; #p; #q; #posn; #Hlt;
759 nelim (decidable_lt p q);//;
760 #nltpq;napply False_ind;
761 napply (lt_to_not_le ? ? Hlt);
762 napply monotonic_le_times_l;/3/;
765 ntheorem lt_times_n_to_lt_r:
766 ∀n,p,q:nat. O < n → n*p < n*q → p < q.
767 #n; #p; #q; #posn; #Hlt;
768 napply (lt_times_n_to_lt_l ??? posn);//;
772 theorem nat_compare_times_l : \forall n,p,q:nat.
773 nat_compare p q = nat_compare ((S n) * p) ((S n) * q).
774 intros.apply nat_compare_elim.intro.
775 apply nat_compare_elim.
778 apply (inj_times_r n).assumption.
779 apply lt_to_not_eq. assumption.
781 apply (lt_times_to_lt_r n).assumption.
782 apply le_to_not_lt.apply lt_to_le.assumption.
783 intro.rewrite < H.rewrite > nat_compare_n_n.reflexivity.
784 intro.apply nat_compare_elim.intro.
786 apply (lt_times_to_lt_r n).assumption.
787 apply le_to_not_lt.apply lt_to_le.assumption.
790 apply (inj_times_r n).assumption.
791 apply lt_to_not_eq.assumption.
796 theorem lt_times_plus_times: \forall a,b,n,m:nat.
797 a < n \to b < m \to a*m + b < n*m.
800 [intros.apply False_ind.apply (not_le_Sn_O ? H)
804 change with (S b+a*m1 \leq m1+m*m1).
808 [apply le_S_S_to_le.assumption
815 (************************** minus ******************************)
823 | S q ⇒ minus p q ]].
825 interpretation "natural minus" 'minus x y = (minus x y).
827 ntheorem minus_S_S: ∀n,m:nat.S n - S m = n -m.
830 ntheorem minus_O_n: ∀n:nat.O=O-n.
831 #n; ncases n; //; nqed.
833 ntheorem minus_n_O: ∀n:nat.n=n-O.
834 #n; ncases n; //; nqed.
836 ntheorem minus_n_n: ∀n:nat.O=n-n.
837 #n; nelim n; //; nqed.
839 ntheorem minus_Sn_n: ∀n:nat. S O = (S n)-n.
840 #n; nelim n; //; nqed.
842 ntheorem minus_Sn_m: ∀m,n:nat. m ≤ n → S n -m = S (n-m).
843 (* qualcosa da capire qui
844 #n; #m; #lenm; nelim lenm; napplyS refl_eq. *)
847 ##|#n; #abs; napply False_ind; /2/.
848 ##|#n; #m; #Hind; #c; napplyS Hind; /2/;
852 ntheorem not_eq_to_le_to_le_minus:
853 ∀n,m.n ≠ m → n ≤ m → n ≤ m - 1.
854 #n; #m; ncases m;//; #m; nnormalize;
855 #H; #H1; napply le_S_S_to_le;
856 napplyS (not_eq_to_le_to_lt n (S m) H H1);
859 ntheorem eq_minus_S_pred: ∀n,m. n - (S m) = pred(n -m).
860 napply nat_elim2; //; nqed.
863 ∀m,n,p:nat. m ≤ n → (n-m)+p = (n+p)-m.
866 ##|#n; #p; #abs; napply False_ind; /2/;
871 ntheorem minus_plus_m_m: ∀n,m:nat.n = (n+m)-m.
872 #n; #m; napplyS (plus_minus m m n); //; nqed.
874 ntheorem plus_minus_m_m: ∀n,m:nat.
875 m \leq n \to n = (n-m)+m.
876 #n; #m; #lemn; napplyS symmetric_eq;
877 napplyS (plus_minus m n m); //; nqed.
879 ntheorem le_plus_minus_m_m: ∀n,m:nat. n ≤ (n-m)+m.
882 ##|#a; #Hind; #m; ncases m;//;
883 nnormalize; #n;napplyS le_S_S;//
887 ntheorem minus_to_plus :∀n,m,p:nat.
888 m ≤ n → n-m = p → n = m+p.
889 #n; #m; #p; #lemn; #eqp; napplyS plus_minus_m_m; //;
892 ntheorem plus_to_minus :∀n,m,p:nat.n = m+p → n-m = p.
893 (* /4/ done in 43.5 *)
896 napplyS (minus_plus_m_m p m);
899 ntheorem minus_pred_pred : ∀n,m:nat. O < n → O < m →
900 pred n - pred m = n - m.
901 #n; #m; #posn; #posm;
902 napply (lt_O_n_elim n posn);
903 napply (lt_O_n_elim m posm);//.
907 theorem eq_minus_n_m_O: \forall n,m:nat.
908 n \leq m \to n-m = O.
910 apply (nat_elim2 (\lambda n,m.n \leq m \to n-m = O)).
911 intros.simplify.reflexivity.
912 intros.apply False_ind.
916 simplify.apply H.apply le_S_S_to_le. apply H1.
919 theorem le_SO_minus: \forall n,m:nat.S n \leq m \to S O \leq m-n.
920 intros.elim H.elim (minus_Sn_n n).apply le_n.
921 rewrite > minus_Sn_m.
922 apply le_S.assumption.
923 apply lt_to_le.assumption.
926 theorem minus_le_S_minus_S: \forall n,m:nat. m-n \leq S (m-(S n)).
928 apply (nat_elim2 (\lambda n,m.m-n \leq S (m-(S n)))).
929 intro.elim n1.simplify.apply le_n_Sn.
930 simplify.rewrite < minus_n_O.apply le_n.
931 intros.simplify.apply le_n_Sn.
932 intros.simplify.apply H.
935 theorem lt_minus_S_n_to_le_minus_n : \forall n,m,p:nat. m-(S n) < p \to m-n \leq p.
938 (* end auto($Revision: 9739 $) proof: TIME=1.33 SIZE=100 DEPTH=100 *)
939 apply (trans_le (m-n) (S (m-(S n))) p).
940 apply minus_le_S_minus_S.
944 theorem le_minus_m: \forall n,m:nat. n-m \leq n.
945 intros.apply (nat_elim2 (\lambda m,n. n-m \leq n)).
946 intros.rewrite < minus_n_O.apply le_n.
947 intros.simplify.apply le_n.
948 intros.simplify.apply le_S.assumption.
951 theorem lt_minus_m: \forall n,m:nat. O < n \to O < m \to n-m \lt n.
952 intros.apply (lt_O_n_elim n H).intro.
953 apply (lt_O_n_elim m H1).intro.
954 simplify.unfold lt.apply le_S_S.apply le_minus_m.
957 theorem minus_le_O_to_le: \forall n,m:nat. n-m \leq O \to n \leq m.
959 apply (nat_elim2 (\lambda n,m:nat.n-m \leq O \to n \leq m)).
961 simplify.intros. assumption.
962 simplify.intros.apply le_S_S.apply H.assumption.
966 (* monotonicity and galois *)
968 ntheorem monotonic_le_minus_l:
969 ∀p,q,n:nat. q ≤ p → q-n ≤ p-n.
970 napply nat_elim2; #p; #q;
971 ##[#lePO; napply (le_n_O_elim ? lePO);//;
973 ##|#Hind; #n; ncases n;
975 ##|#a; #leSS; napply Hind; /2/;
980 ntheorem le_minus_to_plus: ∀n,m,p. n-m ≤ p → n≤ p+m.
982 napply transitive_le;
983 ##[##|napply le_plus_minus_m_m
984 ##|napply monotonic_le_plus_l;//;
988 ntheorem le_plus_to_minus: ∀n,m,p. n ≤ p+m → n-m ≤ p.
991 napplyS monotonic_le_minus_l;//;
994 ntheorem monotonic_le_minus_r:
995 ∀p,q,n:nat. q ≤ p → n-p ≤ n-q.
997 napply le_plus_to_minus;
998 napply (transitive_le ??? (le_plus_minus_m_m ? q));/2/;
1001 (*********************** boolean arithmetics ********************)
1002 include "basics/bool.ma".
1006 [ O ⇒ match m with [ O ⇒ true | S q ⇒ false]
1007 | S p ⇒ match m with [ O ⇒ false | S q ⇒ eqb p q]
1011 ntheorem eqb_to_Prop: ∀n,m:nat.
1012 match (eqb n m) with
1013 [ true \Rightarrow n = m
1014 | false \Rightarrow n \neq m].
1017 (\lambda n,m:nat.match (eqb n m) with
1018 [ true \Rightarrow n = m
1019 | false \Rightarrow n \neq m])).
1021 simplify.reflexivity.
1022 simplify.apply not_eq_O_S.
1024 simplify.unfold Not.
1025 intro. apply (not_eq_O_S n1).apply sym_eq.assumption.
1027 generalize in match H.
1029 simplify.apply eq_f.apply H1.
1030 simplify.unfold Not.intro.apply H1.apply inj_S.assumption.
1034 ntheorem eqb_elim : ∀ n,m:nat.∀ P:bool → Prop.
1035 (n=m → (P true)) → (n ≠ m → (P false)) → (P (eqb n m)).
1037 ##[#n; ncases n; nnormalize; /3/;
1043 ntheorem eqb_n_n: ∀n. eqb n n = true.
1044 #n; nelim n; nnormalize; //.
1047 ntheorem eqb_true_to_eq: ∀n,m:nat. eqb n m = true → n = m.
1048 #n; #m; napply (eqb_elim n m);//;
1049 #_; #abs; napply False_ind; /2/;
1052 ntheorem eqb_false_to_not_eq: ∀n,m:nat. eqb n m = false → n ≠ m.
1053 #n; #m; napply (eqb_elim n m);/2/;
1056 ntheorem eq_to_eqb_true: ∀n,m:nat.
1057 n = m → eqb n m = true.
1060 ntheorem not_eq_to_eqb_false: ∀n,m:nat.
1061 n ≠ m → eqb n m = false.
1063 nelim (true_or_false (eqb n m)); //;
1064 #Heq; napply False_ind; napply noteq;/2/;
1073 | (S q) ⇒ leb p q]].
1075 ntheorem leb_elim: ∀n,m:nat. ∀P:bool → Prop.
1076 (n ≤ m → P true) → (n ≰ m → P false) → P (leb n m).
1077 napply nat_elim2; nnormalize;
1080 ##|#n; #m; #Hind; #P; #Pt; #Pf; napply Hind;
1081 ##[#lenm; napply Pt; napply le_S_S;//;
1082 ##|#nlenm; napply Pf; #leSS; /3/;
1087 ntheorem leb_true_to_le:∀n,m.leb n m = true → n ≤ m.
1088 #n; #m; napply leb_elim;
1090 ##|#_; #abs; napply False_ind; /2/;
1094 ntheorem leb_false_to_not_le:∀n,m.
1095 leb n m = false → n ≰ m.
1096 #n; #m; napply leb_elim;
1097 ##[#_; #abs; napply False_ind; /2/;
1102 ntheorem le_to_leb_true: ∀n,m. n ≤ m → leb n m = true.
1103 #n; #m; napply leb_elim; //;
1104 #H; #H1; napply False_ind; /2/;
1107 ntheorem lt_to_leb_false: ∀n,m. m < n → leb n m = false.
1108 #n; #m; napply leb_elim; //;
1109 #H; #H1; napply False_ind; /2/;
1113 ndefinition ltb ≝λn,m. leb (S n) m.
1115 ntheorem ltb_elim: ∀n,m:nat. ∀P:bool → Prop.
1116 (n < m → P true) → (n ≮ m → P false) → P (ltb n m).
1117 #n; #m; #P; #Hlt; #Hnlt;
1118 napply leb_elim; /3/; nqed.
1120 ntheorem ltb_true_to_lt:∀n,m.ltb n m = true → n < m.
1121 #n; #m; #Hltb; napply leb_true_to_le; nassumption;
1124 ntheorem ltb_false_to_not_lt:∀n,m.
1125 ltb n m = false → n ≮ m.
1126 #n; #m; #Hltb; napply leb_false_to_not_le; nassumption;
1129 ntheorem lt_to_ltb_true: ∀n,m. n < m → ltb n m = true.
1130 #n; #m; #Hltb; napply le_to_leb_true; nassumption;
1133 ntheorem le_to_ltb_false: ∀n,m. m \le n → ltb n m = false.
1134 #n; #m; #Hltb; napply lt_to_leb_false; /2/;