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 ntheorem foo: ∀A:Type.∀a,b:A.∀f:A→A.∀g:A→A→A.
21 (∀x,y.f (g x y) = x) → ∀x. g (f a) x = b → f a = f b.
24 ninductive nat : Type[0] ≝
28 interpretation "Natural numbers" 'N = nat.
30 alias num (instance 0) = "nnatural number".
34 {n:>nat; is_pos: n ≠ 0}.
36 ncoercion nat_to_pos: ∀n:nat. n ≠0 →pos ≝ mk_pos on
39 (* default "natural numbers" cic:/matita/ng/arithmetics/nat/nat.ind.
43 λn. match n with [ O ⇒ O | (S p) ⇒ p].
45 ntheorem pred_Sn : ∀n. n = pred (S n).
48 ntheorem injective_S : injective nat nat S.
52 ntheorem inj_S : \forall n,m:nat.(S n)=(S m) \to n=m.
55 ntheorem not_eq_S: ∀n,m:nat. n ≠ m → S n ≠ S m.
58 ndefinition not_zero: nat → Prop ≝
60 [ O ⇒ False | (S p) ⇒ True ].
62 ntheorem not_eq_O_S : ∀n:nat. O ≠ S n.
63 #n; napply nmk; #eqOS; nchange with (not_zero O); nrewrite > eqOS; //.
66 ntheorem not_eq_n_Sn: ∀n:nat. n ≠ S n.
67 #n; nelim n;/2/; nqed.
71 (n=O → P O) → (∀m:nat. (n=(S m) → P (S m))) → P n.
72 #n; #P; nelim n; /2/; nqed.
78 → (∀n,m:nat. R n m → R (S n) (S m))
80 #R; #ROn; #RSO; #RSS; #n; nelim n;//;
81 #n0; #Rn0m; #m; ncases m;/2/; nqed.
83 ntheorem decidable_eq_nat : ∀n,m:nat.decidable (n=m).
87 ##| #m; #Hind; ncases Hind; /3/;
91 (*************************** plus ******************************)
96 | S p ⇒ S (plus p m) ].
98 interpretation "natural plus" 'plus x y = (plus x y).
100 ntheorem plus_O_n: ∀n:nat. n = 0+n.
104 ntheorem plus_Sn_m: ∀n,m:nat. S (n + m) = S n + m.
108 ntheorem plus_n_O: ∀n:nat. n = n+0.
109 #n; nelim n; nnormalize; //; nqed.
111 ntheorem plus_n_Sm : ∀n,m:nat. S (n+m) = n + S m.
112 #n; nelim n; nnormalize; //; nqed.
115 ntheorem plus_Sn_m1: ∀n,m:nat. S m + n = n + S m.
116 #n; nelim n; nnormalize; //; nqed.
120 ntheorem plus_n_1 : ∀n:nat. S n = n+1.
124 ntheorem symmetric_plus: symmetric ? plus.
125 #n; nelim n; nnormalize; //; nqed.
127 ntheorem associative_plus : associative nat plus.
128 #n; nelim n; nnormalize; //; nqed.
130 ntheorem assoc_plus1: ∀a,b,c. c + (b + a) = b + c + a.
133 ntheorem injective_plus_r: ∀n:nat.injective nat nat (λm.n+m).
134 #n; nelim n; nnormalize; /3/; nqed.
136 (* ntheorem inj_plus_r: \forall p,n,m:nat. p+n = p+m \to n=m
137 \def injective_plus_r.
139 ntheorem injective_plus_l: ∀m:nat.injective nat nat (λn.n+m).
142 (* ntheorem inj_plus_l: \forall p,n,m:nat. n+p = m+p \to n=m
143 \def injective_plus_l. *)
145 (*************************** times *****************************)
150 | S p ⇒ m+(times p m) ].
152 interpretation "natural times" 'times x y = (times x y).
154 ntheorem times_Sn_m: ∀n,m:nat. m+n*m = S n*m.
157 ntheorem times_O_n: ∀n:nat. O = O*n.
160 ntheorem times_n_O: ∀n:nat. O = n*O.
161 #n; nelim n; //; nqed.
163 ntheorem times_n_Sm : ∀n,m:nat. n+(n*m) = n*(S m).
164 #n; nelim n; nnormalize; //; nqed.
166 ntheorem symmetric_times : symmetric nat times.
167 #n; nelim n; nnormalize; //; nqed.
169 (* variant sym_times : \forall n,m:nat. n*m = m*n \def
172 ntheorem distributive_times_plus : distributive nat times plus.
173 #n; nelim n; nnormalize; //; nqed.
175 ntheorem distributive_times_plus_r :
176 ∀a,b,c:nat. (b+c)*a = b*a + c*a.
179 ntheorem associative_times: associative nat times.
180 #n; nelim n; nnormalize; //; nqed.
182 nlemma times_times: ∀x,y,z. x*(y*z) = y*(x*z).
185 (* ci servono questi risultati?
186 ntheorem times_O_to_O: ∀n,m:nat.n*m=O → n=O ∨ m=O.
187 napply nat_elim2; /2/;
188 #n; #m; #H; nnormalize; #H1; napply False_ind;napply not_eq_O_S;
191 ntheorem times_n_SO : ∀n:nat. n = n * S O.
194 ntheorem times_SSO_n : ∀n:nat. n + n = (S(S O)) * n.
195 nnormalize; //; nqed.
197 nlemma times_SSO: \forall n.(S(S O))*(S n) = S(S((S(S O))*n)).
200 ntheorem or_eq_eq_S: \forall n.\exists m.
201 n = (S(S O))*m \lor n = S ((S(S O))*m).
204 ##|#a; #H; nelim H; #b;#or;nelim or;#aeq;
206 ##|@ (S b); @ 1; /2/;
211 (******************** ordering relations ************************)
213 ninductive le (n:nat) : nat → Prop ≝
215 | le_S : ∀ m:nat. le n m → le n (S m).
217 interpretation "natural 'less or equal to'" 'leq x y = (le x y).
219 interpretation "natural 'neither less nor equal to'" 'nleq x y = (Not (le x y)).
221 ndefinition lt: nat → nat → Prop ≝
224 interpretation "natural 'less than'" 'lt x y = (lt x y).
226 interpretation "natural 'not less than'" 'nless x y = (Not (lt x y)).
228 (* nlemma eq_lt: ∀n,m. (n < m) = (S n ≤ m).
231 ndefinition ge: nat → nat → Prop ≝
234 interpretation "natural 'greater or equal to'" 'geq x y = (ge x y).
236 ndefinition gt: nat → nat → Prop ≝
239 interpretation "natural 'greater than'" 'gt x y = (gt x y).
241 interpretation "natural 'not greater than'" 'ngtr x y = (Not (gt x y)).
243 ntheorem transitive_le : transitive nat le.
244 #a; #b; #c; #leab; #lebc;nelim lebc;/2/;
248 ntheorem trans_le: \forall n,m,p:nat. n \leq m \to m \leq p \to n \leq p
249 \def transitive_le. *)
252 ntheorem transitive_lt: transitive nat lt.
253 #a; #b; #c; #ltab; #ltbc;nelim ltbc;/2/;nqed.
256 theorem trans_lt: \forall n,m,p:nat. lt n m \to lt m p \to lt n p
257 \def transitive_lt. *)
259 ntheorem le_S_S: ∀n,m:nat. n ≤ m → S n ≤ S m.
260 #n; #m; #lenm; nelim lenm; /2/; nqed.
262 ntheorem le_O_n : ∀n:nat. O ≤ n.
263 #n; nelim n; /2/; nqed.
265 ntheorem le_n_Sn : ∀n:nat. n ≤ S n.
268 ntheorem le_pred_n : ∀n:nat. pred n ≤ n.
269 #n; nelim n; //; nqed.
271 (* XXX global problem
272 nlemma my_trans_le : ∀x,y,z:nat.x ≤ y → y ≤ z → x ≤ z.
273 napply transitive_le.
276 ntheorem monotonic_pred: monotonic ? le pred.
277 #n; #m; #lenm; nelim lenm; /2/;nqed.
279 ntheorem le_S_S_to_le: ∀n,m:nat. S n ≤ S m → n ≤ m.
280 (* XXX *) nletin hint ≝ monotonic.
283 (* this are instances of the le versions
284 ntheorem lt_S_S_to_lt: ∀n,m. S n < S m → n < m.
287 ntheorem lt_to_lt_S_S: ∀n,m. n < m → S n < S m.
290 ntheorem lt_to_not_zero : ∀n,m:nat. n < m → not_zero m.
291 #n; #m; #Hlt; nelim Hlt;//; nqed.
294 ntheorem not_le_Sn_O: ∀ n:nat. S n ≰ O.
295 #n; napply nmk; #Hlen0; napply (lt_to_not_zero ?? Hlen0); nqed.
297 ntheorem not_le_to_not_le_S_S: ∀ n,m:nat. n ≰ m → S n ≰ S m.
300 ntheorem not_le_S_S_to_not_le: ∀ n,m:nat. S n ≰ S m → n ≰ m.
303 ntheorem decidable_le: ∀n,m. decidable (n≤m).
304 napply nat_elim2; #n; /2/;
307 ntheorem decidable_lt: ∀n,m. decidable (n < m).
308 #n; #m; napply decidable_le ; nqed.
310 ntheorem not_le_Sn_n: ∀n:nat. S n ≰ n.
311 #n; nelim n; /2/; nqed.
313 (* this is le_S_S_to_le
314 ntheorem lt_S_to_le: ∀n,m:nat. n < S m → n ≤ m.
318 ntheorem not_le_to_lt: ∀n,m. n ≰ m → m < n.
319 napply nat_elim2; #n;
320 ##[#abs; napply False_ind;/2/;
322 ##|#m;#Hind;#HnotleSS; napply le_S_S;/3/;
326 ntheorem lt_to_not_le: ∀n,m. n < m → m ≰ n.
327 #n; #m; #Hltnm; nelim Hltnm;/3/; nqed.
329 ntheorem not_lt_to_le: ∀n,m:nat. n ≮ m → m ≤ n.
333 #n; #m; #Hnlt; napply le_S_S_to_le;/2/;
334 (* something strange here: /2/ fails *)
335 napply not_le_to_lt; napply Hnlt; nqed. *)
337 ntheorem le_to_not_lt: ∀n,m:nat. n ≤ m → m ≮ n.
338 #n; #m; #H;napply lt_to_not_le; /2/; (* /3/ *) nqed.
340 (* lt and le trans *)
342 ntheorem lt_to_le_to_lt: ∀n,m,p:nat. n < m → m ≤ p → n < p.
343 #n; #m; #p; #H; #H1; nelim H1; /2/; nqed.
345 ntheorem le_to_lt_to_lt: ∀n,m,p:nat. n ≤ m → m < p → n < p.
346 #n; #m; #p; #H; nelim H; /3/; nqed.
348 ntheorem lt_S_to_lt: ∀n,m. S n < m → n < m.
351 ntheorem ltn_to_ltO: ∀n,m:nat. n < m → O < m.
355 theorem lt_SO_n_to_lt_O_pred_n: \forall n:nat.
356 (S O) \lt n \to O \lt (pred n).
358 apply (ltn_to_ltO (pred (S O)) (pred n) ?).
359 apply (lt_pred (S O) n);
365 ntheorem lt_O_n_elim: ∀n:nat. O < n →
366 ∀P:nat → Prop.(∀m:nat.P (S m)) → P n.
367 #n; nelim n; //; #abs; napply False_ind;/2/;
371 theorem lt_pred: \forall n,m.
372 O < n \to n < m \to pred n < pred m.
374 [intros.apply False_ind.apply (not_le_Sn_O ? H)
375 |intros.apply False_ind.apply (not_le_Sn_O ? H1)
376 |intros.simplify.unfold.apply le_S_S_to_le.assumption
380 theorem S_pred: \forall n:nat.lt O n \to eq nat n (S (pred n)).
381 intro.elim n.apply False_ind.exact (not_le_Sn_O O H).
382 apply eq_f.apply pred_Sn.
385 theorem le_pred_to_le:
386 ∀n,m. O < m → pred n ≤ pred m → n ≤ m.
391 rewrite > (S_pred m);
402 ntheorem le_to_or_lt_eq: ∀n,m:nat. n ≤ m → n < m ∨ n = m.
403 #n; #m; #lenm; nelim lenm; /3/; nqed.
406 ntheorem lt_to_not_eq : ∀n,m:nat. n < m → n ≠ m.
407 #n; #m; #H; napply not_to_not;/2/; nqed.
410 ntheorem eq_to_not_lt: ∀a,b:nat. a = b → a ≮ b.
415 apply (lt_to_not_eq b b)
421 theorem lt_n_m_to_not_lt_m_Sn: ∀n,m. n < m → m ≮ S n.
427 generalize in match (le_S_S ? ? H);
429 generalize in match (transitive_le ? ? ? H2 H1);
431 apply (not_le_Sn_n ? H3).
434 ntheorem not_eq_to_le_to_lt: ∀n,m. n≠m → n≤m → n<m.
435 #n; #m; #Hneq; #Hle; ncases (le_to_or_lt_eq ?? Hle); //;
438 nelim (Hneq Heq); nqed. *)
441 ntheorem le_n_O_to_eq : ∀n:nat. n ≤ O → O=n.
442 #n; ncases n; //; #a ; #abs;
443 napply False_ind; /2/;nqed.
445 ntheorem le_n_O_elim: ∀n:nat. n ≤ O → ∀P: nat →Prop. P O → P n.
446 #n; ncases n; //; #a; #abs;
447 napply False_ind; /2/; nqed.
449 ntheorem le_n_Sm_elim : ∀n,m:nat.n ≤ S m →
450 ∀P:Prop. (S n ≤ S m → P) → (n=S m → P) → P.
451 #n; #m; #Hle; #P; nelim Hle; /3/; nqed.
455 ntheorem le_to_le_to_eq: ∀n,m. n ≤ m → m ≤ n → n = m.
456 napply nat_elim2; /4/; nqed.
458 ntheorem lt_O_S : ∀n:nat. O < S n.
462 (* other abstract properties *)
463 theorem antisymmetric_le : antisymmetric nat le.
464 unfold antisymmetric.intros 2.
465 apply (nat_elim2 (\lambda n,m.(n \leq m \to m \leq n \to n=m))).
466 intros.apply le_n_O_to_eq.assumption.
467 intros.apply False_ind.apply (not_le_Sn_O ? H).
468 intros.apply eq_f.apply H.
469 apply le_S_S_to_le.assumption.
470 apply le_S_S_to_le.assumption.
473 theorem antisym_le: \forall n,m:nat. n \leq m \to m \leq n \to n=m
474 \def antisymmetric_le.
476 theorem le_n_m_to_lt_m_Sn_to_eq_n_m: ∀n,m. n ≤ m → m < S n → n=m.
479 generalize in match (le_S_S_to_le ? ? H1);
486 (* well founded induction principles *)
488 ntheorem nat_elim1 : ∀n:nat.∀P:nat → Prop.
489 (∀m.(∀p. p < m → P p) → P m) → P n.
491 ncut (∀q:nat. q ≤ n → P q);/2/;
493 ##[#q; #HleO; (* applica male *)
494 napply (le_n_O_elim ? HleO);
496 napply False_ind; /2/; (* 3 *)
497 ##|#p; #Hind; #q; #HleS;
498 napply H; #a; #lta; napply Hind;
499 napply le_S_S_to_le;/2/;
503 (* some properties of functions *)
505 definition increasing \def \lambda f:nat \to nat.
506 \forall n:nat. f n < f (S n).
508 theorem increasing_to_monotonic: \forall f:nat \to nat.
509 increasing f \to monotonic nat lt f.
510 unfold monotonic.unfold lt.unfold increasing.unfold lt.intros.elim H1.apply H.
511 apply (trans_le ? (f n1)).
512 assumption.apply (trans_le ? (S (f n1))).
517 theorem le_n_fn: \forall f:nat \to nat. (increasing f)
518 \to \forall n:nat. n \le (f n).
521 apply (trans_le ? (S (f n1))).
522 apply le_S_S.apply H1.
523 simplify in H. unfold increasing in H.unfold lt in H.apply H.
526 theorem increasing_to_le: \forall f:nat \to nat. (increasing f)
527 \to \forall m:nat. \exists i. m \le (f i).
529 apply (ex_intro ? ? O).apply le_O_n.
531 apply (ex_intro ? ? (S a)).
532 apply (trans_le ? (S (f a))).
533 apply le_S_S.assumption.
534 simplify in H.unfold increasing in H.unfold lt in H.
538 theorem increasing_to_le2: \forall f:nat \to nat. (increasing f)
539 \to \forall m:nat. (f O) \le m \to
540 \exists i. (f i) \le m \land m <(f (S i)).
542 apply (ex_intro ? ? O).
543 split.apply le_n.apply H.
545 cut ((S n1) < (f (S a)) \lor (S n1) = (f (S a))).
547 apply (ex_intro ? ? a).
548 split.apply le_S. assumption.assumption.
549 apply (ex_intro ? ? (S a)).
550 split.rewrite < H7.apply le_n.
553 apply le_to_or_lt_eq.apply H6.
557 (*********************** monotonicity ***************************)
558 ntheorem monotonic_le_plus_r:
559 ∀n:nat.monotonic nat le (λm.n + m).
560 #n; #a; #b; nelim n; nnormalize; //;
561 #m; #H; #leab;napply le_S_S; /2/; nqed.
564 ntheorem le_plus_r: ∀p,n,m:nat. n ≤ m → p + n ≤ p + m
565 ≝ monotonic_le_plus_r. *)
567 ntheorem monotonic_le_plus_l:
568 ∀m:nat.monotonic nat le (λn.n + m).
569 #m; #x; #y; #H; napplyS monotonic_le_plus_r;
573 ntheorem le_plus_l: \forall p,n,m:nat. n \le m \to n + p \le m + p
574 \def monotonic_le_plus_l. *)
576 ntheorem le_plus: ∀n1,n2,m1,m2:nat. n1 ≤ n2 → m1 ≤ m2
578 #n1; #n2; #m1; #m2; #len; #lem; napply (transitive_le ? (n1+m2));
581 ntheorem le_plus_n :∀n,m:nat. m ≤ n + m.
584 nlemma le_plus_a: ∀a,n,m. n ≤ m → n ≤ a + m.
587 nlemma le_plus_b: ∀b,n,m. n + b ≤ m → n ≤ m.
590 ntheorem le_plus_n_r :∀n,m:nat. m ≤ m + n.
593 ntheorem eq_plus_to_le: ∀n,m,p:nat.n=m+p → m ≤ n.
596 ntheorem le_plus_to_le: ∀a,n,m. a + n ≤ a + m → n ≤ m.
597 #a; nelim a; nnormalize; /3/; nqed.
599 ntheorem le_plus_to_le_r: ∀a,n,m. n + a ≤ m +a → n ≤ m.
604 ntheorem monotonic_lt_plus_r:
605 ∀n:nat.monotonic nat lt (λm.n+m).
609 variant lt_plus_r: \forall n,p,q:nat. p < q \to n + p < n + q \def
610 monotonic_lt_plus_r. *)
612 ntheorem monotonic_lt_plus_l:
613 ∀n:nat.monotonic nat lt (λm.m+n).
617 variant lt_plus_l: \forall n,p,q:nat. p < q \to p + n < q + n \def
618 monotonic_lt_plus_l. *)
620 ntheorem lt_plus: ∀n,m,p,q:nat. n < m → p < q → n + p < m + q.
621 #n; #m; #p; #q; #ltnm; #ltpq;
622 napply (transitive_lt ? (n+q));/2/; nqed.
624 ntheorem lt_plus_to_lt_l :∀n,p,q:nat. p+n < q+n → p<q.
627 ntheorem lt_plus_to_lt_r :∀n,p,q:nat. n+p < n+q → p<q.
631 ntheorem le_to_lt_to_lt_plus: ∀a,b,c,d:nat.
632 a ≤ c → b < d → a + b < c+d.
633 (* bello /2/ un po' lento *)
634 #a; #b; #c; #d; #leac; #lebd;
635 nnormalize; napplyS le_plus; //; nqed.
639 ntheorem monotonic_le_times_r:
640 ∀n:nat.monotonic nat le (λm. n * m).
641 #n; #x; #y; #lexy; nelim n; nnormalize;//;(* lento /2/;*)
642 #a; #lea; napply le_plus; //;
646 ntheorem le_times_r: \forall p,n,m:nat. n \le m \to p*n \le p*m
647 \def monotonic_le_times_r. *)
650 ntheorem monotonic_le_times_l:
651 ∀m:nat.monotonic nat le (λn.n*m).
656 theorem le_times_l: \forall p,n,m:nat. n \le m \to n*p \le m*p
657 \def monotonic_le_times_l. *)
659 ntheorem le_times: ∀n1,n2,m1,m2:nat.
660 n1 ≤ n2 → m1 ≤ m2 → n1*m1 ≤ n2*m2.
661 #n1; #n2; #m1; #m2; #len; #lem;
662 napply (transitive_le ? (n1*m2)); (* /2/ slow *)
663 ##[ napply monotonic_le_times_r;//;
664 ##| napplyS monotonic_le_times_r;//;
669 ntheorem lt_times_n: ∀n,m:nat. O < n → m ≤ n*m.
670 #n; #m; #H; /2/; nqed.
672 ntheorem le_times_to_le:
673 ∀a,n,m. O < a → a * n ≤ a * m → n ≤ m.
674 #a; napply nat_elim2; nnormalize;
677 napply (transitive_le ? (a*S n));/2/;
678 ##|#n; #m; #H; #lta; #le;
679 napply le_S_S; napply H; /2/;
683 ntheorem le_S_times_2: ∀n,m.O < m → n ≤ m → S n ≤ 2*m.
684 #n; #m; #posm; #lenm; (* interessante *)
685 napplyS (le_plus n m); //; nqed.
689 ntheorem lt_O_times_S_S: ∀n,m:nat.O < (S n)*(S m).
690 intros.simplify.unfold lt.apply le_S_S.apply le_O_n.
694 ntheorem lt_times_eq_O: \forall a,b:nat.
695 O < a → a * b = O → b = O.
702 rewrite > (S_pred a) in H1
704 apply (eq_to_not_lt O ((S (pred a))*(S m)))
707 | apply lt_O_times_S_S
714 theorem O_lt_times_to_O_lt: \forall a,c:nat.
715 O \lt (a * c) \to O \lt a.
727 lemma lt_times_to_lt_O: \forall i,n,m:nat. i < n*m \to O < m.
729 elim (le_to_or_lt_eq O ? (le_O_n m))
733 rewrite < times_n_O in H.
734 apply (not_le_Sn_O ? H)
739 ntheorem monotonic_lt_times_r:
740 ∀n:nat.monotonic nat lt (λm.(S n)*m).
744 simplify.rewrite < plus_n_O.rewrite < plus_n_O.assumption.
745 apply lt_plus.assumption.assumption.
748 ntheorem monotonic_lt_times_l:
749 ∀c:nat. O < c → monotonic nat lt (λt.(t*c)).
750 #c; #posc; #n; #m; #ltnm;
751 nelim ltnm; nnormalize;
753 ##|#a; #_; #lt1; napply (transitive_le ??? lt1);//;
757 ntheorem monotonic_lt_times_r:
758 ∀c:nat. O < c → monotonic nat lt (λt.(c*t)).
761 ntheorem lt_to_le_to_lt_times:
762 ∀n,m,p,q:nat. n < m → p ≤ q → O < q → n*p < m*q.
763 #n; #m; #p; #q; #ltnm; #lepq; #posq;
764 napply (le_to_lt_to_lt ? (n*q));
765 ##[napply monotonic_le_times_r;//;
766 ##|napply monotonic_lt_times_l;//;
770 ntheorem lt_times:∀n,m,p,q:nat. n<m → p<q → n*p < m*q.
771 #n; #m; #p; #q; #ltnm; #ltpq;
772 napply lt_to_le_to_lt_times;/2/;
775 ntheorem lt_times_n_to_lt_l:
776 ∀n,p,q:nat. p*n < q*n → p < q.
778 nelim (decidable_lt p q);//;
779 #nltpq; napply False_ind;
780 napply (absurd ? ? (lt_to_not_le ? ? Hlt));
781 napplyS monotonic_le_times_r;/2/;
784 ntheorem lt_times_n_to_lt_r:
785 ∀n,p,q:nat. n*p < n*q → p < q.
789 theorem nat_compare_times_l : \forall n,p,q:nat.
790 nat_compare p q = nat_compare ((S n) * p) ((S n) * q).
791 intros.apply nat_compare_elim.intro.
792 apply nat_compare_elim.
795 apply (inj_times_r n).assumption.
796 apply lt_to_not_eq. assumption.
798 apply (lt_times_to_lt_r n).assumption.
799 apply le_to_not_lt.apply lt_to_le.assumption.
800 intro.rewrite < H.rewrite > nat_compare_n_n.reflexivity.
801 intro.apply nat_compare_elim.intro.
803 apply (lt_times_to_lt_r n).assumption.
804 apply le_to_not_lt.apply lt_to_le.assumption.
807 apply (inj_times_r n).assumption.
808 apply lt_to_not_eq.assumption.
813 theorem lt_times_plus_times: \forall a,b,n,m:nat.
814 a < n \to b < m \to a*m + b < n*m.
817 [intros.apply False_ind.apply (not_le_Sn_O ? H)
821 change with (S b+a*m1 \leq m1+m*m1).
825 [apply le_S_S_to_le.assumption
832 (************************** minus ******************************)
840 | S q ⇒ minus p q ]].
842 interpretation "natural minus" 'minus x y = (minus x y).
844 ntheorem minus_S_S: ∀n,m:nat.S n - S m = n -m.
847 ntheorem minus_O_n: ∀n:nat.O=O-n.
848 #n; ncases n; //; nqed.
850 ntheorem minus_n_O: ∀n:nat.n=n-O.
851 #n; ncases n; //; nqed.
853 ntheorem minus_n_n: ∀n:nat.O=n-n.
854 #n; nelim n; //; nqed.
856 ntheorem minus_Sn_n: ∀n:nat. S O = (S n)-n.
857 #n; nelim n; nnormalize; //; nqed.
859 ntheorem minus_Sn_m: ∀m,n:nat. m ≤ n → S n -m = S (n-m).
860 (* qualcosa da capire qui
861 #n; #m; #lenm; nelim lenm; napplyS refl_eq. *)
864 ##|#n; #abs; napply False_ind; /2/
865 ##|#n; #m; #Hind; #c; napplyS Hind; /2/;
869 ntheorem not_eq_to_le_to_le_minus:
870 ∀n,m.n ≠ m → n ≤ m → n ≤ m - 1.
871 #n; #m; ncases m;//; #m; nnormalize;
872 #H; #H1; napply le_S_S_to_le;
873 napplyS (not_eq_to_le_to_lt n (S m) H H1);
876 ntheorem eq_minus_S_pred: ∀n,m. n - (S m) = pred(n -m).
877 napply nat_elim2; nnormalize; //; nqed.
880 ∀m,n,p:nat. m ≤ n → (n-m)+p = (n+p)-m.
883 ##|#n; #p; #abs; napply False_ind; /2/;
888 ntheorem minus_plus_m_m: ∀n,m:nat.n = (n+m)-m.
889 #n; #m; napplyS (plus_minus m m n); //; nqed.
891 ntheorem plus_minus_m_m: ∀n,m:nat.
893 #n; #m; #lemn; napplyS symmetric_eq;
894 napplyS (plus_minus m n m); //; nqed.
896 ntheorem le_plus_minus_m_m: ∀n,m:nat. n ≤ (n-m)+m.
899 ##|#a; #Hind; #m; ncases m;//;
904 ntheorem minus_to_plus :∀n,m,p:nat.
905 m ≤ n → n-m = p → n = m+p.
906 #n; #m; #p; #lemn; #eqp; napplyS plus_minus_m_m; //;
909 ntheorem plus_to_minus :∀n,m,p:nat.n = m+p → n-m = p.
910 (* /4/ done in 43.5 *)
913 napplyS (minus_plus_m_m p m);
916 ntheorem minus_pred_pred : ∀n,m:nat. O < n → O < m →
917 pred n - pred m = n - m.
918 #n; #m; #posn; #posm;
919 napply (lt_O_n_elim n posn);
920 napply (lt_O_n_elim m posm);//.
924 theorem eq_minus_n_m_O: \forall n,m:nat.
925 n \leq m \to n-m = O.
927 apply (nat_elim2 (\lambda n,m.n \leq m \to n-m = O)).
928 intros.simplify.reflexivity.
929 intros.apply False_ind.
933 simplify.apply H.apply le_S_S_to_le. apply H1.
936 theorem le_SO_minus: \forall n,m:nat.S n \leq m \to S O \leq m-n.
937 intros.elim H.elim (minus_Sn_n n).apply le_n.
938 rewrite > minus_Sn_m.
939 apply le_S.assumption.
940 apply lt_to_le.assumption.
943 theorem minus_le_S_minus_S: \forall n,m:nat. m-n \leq S (m-(S n)).
945 apply (nat_elim2 (\lambda n,m.m-n \leq S (m-(S n)))).
946 intro.elim n1.simplify.apply le_n_Sn.
947 simplify.rewrite < minus_n_O.apply le_n.
948 intros.simplify.apply le_n_Sn.
949 intros.simplify.apply H.
952 theorem lt_minus_S_n_to_le_minus_n : \forall n,m,p:nat. m-(S n) < p \to m-n \leq p.
955 (* end auto($Revision: 9739 $) proof: TIME=1.33 SIZE=100 DEPTH=100 *)
956 apply (trans_le (m-n) (S (m-(S n))) p).
957 apply minus_le_S_minus_S.
961 theorem le_minus_m: \forall n,m:nat. n-m \leq n.
962 intros.apply (nat_elim2 (\lambda m,n. n-m \leq n)).
963 intros.rewrite < minus_n_O.apply le_n.
964 intros.simplify.apply le_n.
965 intros.simplify.apply le_S.assumption.
968 theorem lt_minus_m: \forall n,m:nat. O < n \to O < m \to n-m \lt n.
969 intros.apply (lt_O_n_elim n H).intro.
970 apply (lt_O_n_elim m H1).intro.
971 simplify.unfold lt.apply le_S_S.apply le_minus_m.
974 theorem minus_le_O_to_le: \forall n,m:nat. n-m \leq O \to n \leq m.
976 apply (nat_elim2 (\lambda n,m:nat.n-m \leq O \to n \leq m)).
978 simplify.intros. assumption.
979 simplify.intros.apply le_S_S.apply H.assumption.
983 (* monotonicity and galois *)
985 ntheorem monotonic_le_minus_l:
986 ∀p,q,n:nat. q ≤ p → q-n ≤ p-n.
987 napply nat_elim2; #p; #q;
988 ##[#lePO; napply (le_n_O_elim ? lePO);//;
990 ##|#Hind; #n; ncases n;
992 ##|#a; #leSS; napply Hind; /2/;
997 ntheorem le_minus_to_plus: ∀n,m,p. n-m ≤ p → n≤ p+m.
999 napply transitive_le;
1000 ##[##|napply le_plus_minus_m_m
1001 ##|napply monotonic_le_plus_l;//;
1005 ntheorem le_plus_to_minus: ∀n,m,p. n ≤ p+m → n-m ≤ p.
1008 napplyS monotonic_le_minus_l;//;
1012 ntheorem monotonic_le_minus_r:
1013 ∀p,q,n:nat. q ≤ p → n-p ≤ n-q.
1015 napply le_plus_to_minus;
1016 napply (transitive_le ??? (le_plus_minus_m_m ? q));/2/;
1019 (*********************** boolean arithmetics ********************)
1020 include "basics/bool.ma".
1024 [ O ⇒ match m with [ O ⇒ true | S q ⇒ false]
1025 | S p ⇒ match m with [ O ⇒ false | S q ⇒ eqb p q]
1029 ntheorem eqb_to_Prop: ∀n,m:nat.
1030 match (eqb n m) with
1031 [ true \Rightarrow n = m
1032 | false \Rightarrow n \neq m].
1035 (\lambda n,m:nat.match (eqb n m) with
1036 [ true \Rightarrow n = m
1037 | false \Rightarrow n \neq m])).
1039 simplify.reflexivity.
1040 simplify.apply not_eq_O_S.
1042 simplify.unfold Not.
1043 intro. apply (not_eq_O_S n1).apply sym_eq.assumption.
1045 generalize in match H.
1047 simplify.apply eq_f.apply H1.
1048 simplify.unfold Not.intro.apply H1.apply inj_S.assumption.
1052 naxiom eqb_elim : ∀ n,m:nat.∀ P:bool → Prop.
1053 (n=m → (P true)) → (n ≠ m → (P false)) → (P (eqb n m)).
1056 ##[#n; ncases n; nnormalize; /3/;
1062 ntheorem eqb_n_n: ∀n. eqb n n = true.
1063 #n; nelim n; nnormalize; //.
1066 ntheorem eqb_true_to_eq: ∀n,m:nat. eqb n m = true → n = m.
1067 #n; #m; napply (eqb_elim n m);//;
1068 #_; #abs; napply False_ind; /2/;
1071 ntheorem eqb_false_to_not_eq: ∀n,m:nat. eqb n m = false → n ≠ m.
1072 #n; #m; napply (eqb_elim n m);/2/;
1075 ntheorem eq_to_eqb_true: ∀n,m:nat.
1076 n = m → eqb n m = true.
1079 ntheorem not_eq_to_eqb_false: ∀n,m:nat.
1080 n ≠ m → eqb n m = false.
1083 #Heq; napply False_ind; /2/;
1092 | (S q) ⇒ leb p q]].
1094 ntheorem leb_elim: ∀n,m:nat. ∀P:bool → Prop.
1095 (n ≤ m → P true) → (n ≰ m → P false) → P (leb n m).
1096 napply nat_elim2; nnormalize;
1099 ##|#n; #m; #Hind; #P; #Pt; #Pf; napply Hind;
1100 ##[#lenm; napply Pt; napply le_S_S;//;
1101 ##|#nlenm; napply Pf; /2/;
1106 ntheorem leb_true_to_le:∀n,m.leb n m = true → n ≤ m.
1107 #n; #m; napply leb_elim;
1109 ##|#_; #abs; napply False_ind; /2/;
1113 ntheorem leb_false_to_not_le:∀n,m.
1114 leb n m = false → n ≰ m.
1115 #n; #m; napply leb_elim;
1116 ##[#_; #abs; napply False_ind; /2/;
1121 ntheorem le_to_leb_true: ∀n,m. n ≤ m → leb n m = true.
1122 #n; #m; napply leb_elim; //;
1123 #H; #H1; napply False_ind; /2/;
1126 ntheorem not_le_to_leb_false: ∀n,m. n ≰ m → leb n m = false.
1127 #n; #m; napply leb_elim; //;
1128 #H; #H1; napply False_ind; /2/;
1131 ntheorem lt_to_leb_false: ∀n,m. m < n → leb n m = false.
1135 ndefinition ltb ≝λn,m. leb (S n) m.
1137 ntheorem ltb_elim: ∀n,m:nat. ∀P:bool → Prop.
1138 (n < m → P true) → (n ≮ m → P false) → P (ltb n m).
1139 #n; #m; #P; #Hlt; #Hnlt;
1140 napply leb_elim; /3/; nqed.
1142 ntheorem ltb_true_to_lt:∀n,m.ltb n m = true → n < m.
1143 #n; #m; #Hltb; napply leb_true_to_le; nassumption;
1146 ntheorem ltb_false_to_not_lt:∀n,m.
1147 ltb n m = false → n ≮ m.
1148 #n; #m; #Hltb; napply leb_false_to_not_le; nassumption;
1151 ntheorem lt_to_ltb_true: ∀n,m. n < m → ltb n m = true.
1152 #n; #m; #Hltb; napply le_to_leb_true; nassumption;
1155 ntheorem le_to_ltb_false: ∀n,m. m \le n → ltb n m = false.
1156 #n; #m; #Hltb; napply lt_to_leb_false; /2/;
1159 ninductive compare : Type[0] ≝
1164 ndefinition compare_invert: compare → compare ≝
1170 nlet rec nat_compare n m: compare ≝
1175 | S p ⇒ match m with
1177 | S q ⇒ nat_compare p q]].
1179 ntheorem nat_compare_n_n: ∀n. nat_compare n n = EQ.
1182 ##|#m;#IH;nnormalize;//]
1185 ntheorem nat_compare_S_S: ∀n,m:nat.nat_compare n m = nat_compare (S n) (S m).
1189 ntheorem nat_compare_pred_pred:
1190 ∀n,m.O < n → O < m → nat_compare n m = nat_compare (pred n) (pred m).
1192 napply (lt_O_n_elim n Hn);
1193 napply (lt_O_n_elim m Hm);
1197 ntheorem nat_compare_to_Prop:
1198 ∀n,m.match (nat_compare n m) with
1203 napply (nat_elim2 (λn,m.match (nat_compare n m) with
1206 | GT ⇒ m < n ]) ?????) (* FIXME: don't want to put all these ?, especially when … does not work! *)
1207 ##[##1,2:#n1;ncases n1;//;
1208 ##|#n1;#m1;nnormalize;ncases (nat_compare n1 m1);
1209 ##[##1,3:nnormalize;#IH;napply le_S_S;//;
1210 ##|nnormalize;#IH;nrewrite > IH;//]
1213 ntheorem nat_compare_n_m_m_n:
1214 ∀n,m:nat.nat_compare n m = compare_invert (nat_compare m n).
1216 napply (nat_elim2 (λn,m. nat_compare n m = compare_invert (nat_compare m n)))
1217 ##[##1,2:#n1;ncases n1;//;
1218 ##|#n1;#m1;#IH;nnormalize;napply IH]
1221 ntheorem nat_compare_elim :
1222 ∀n,m. ∀P:compare → Prop.
1223 (n < m → P LT) → (n=m → P EQ) → (m < n → P GT) → P (nat_compare n m).
1224 #n;#m;#P;#Hlt;#Heq;#Hgt;
1225 ncut (match (nat_compare n m) with
1229 P (nat_compare n m))
1230 ##[ncases (nat_compare n m);
1234 ##|#Hcut;napply Hcut;//;
1237 ninductive cmp_cases (n,m:nat) : CProp[0] ≝
1238 | cmp_le : n ≤ m → cmp_cases n m
1239 | cmp_gt : m < n → cmp_cases n m.
1241 ntheorem lt_to_le : ∀n,m:nat. n < m → n ≤ m.
1247 nlemma cmp_nat: ∀n,m.cmp_cases n m.
1248 #n;#m; nlapply (nat_compare_to_Prop n m);
1249 ncases (nat_compare n m);#H
1250 ##[@;napply lt_to_le;//