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4 (* ||A|| A project by Andrea Asperti *)
6 (* ||I|| Developers: *)
7 (* ||T|| The HELM team. *)
8 (* ||A|| http://helm.cs.unibo.it *)
10 (* \ / This file is distributed under the terms of the *)
11 (* v GNU General Public License Version 2 *)
13 (**************************************************************************)
15 include "logic/pts.ma".
16 include "logic/equality.ma".
17 include "arithmetics/nat.ma".
19 ninductive list (A:Type[0]) : Type[0] ≝
21 | cons: A -> list A -> list A.
23 notation "hvbox(hd break :: tl)"
24 right associative with precedence 47
27 notation "[ list0 x sep ; ]"
28 non associative with precedence 90
29 for ${fold right @'nil rec acc @{'cons $x $acc}}.
31 notation "hvbox(l1 break @ l2)"
32 right associative with precedence 47
33 for @{'append $l1 $l2 }.
35 interpretation "nil" 'nil = (nil ?).
36 interpretation "cons" 'cons hd tl = (cons ? hd tl).
38 nlet rec append A (l1: list A) l2 on l1 ≝
41 | cons hd tl ⇒ hd :: append A tl l2 ].
43 interpretation "append" 'append l1 l2 = (append ? l1 l2).
45 nlet rec id_list A (l: list A) on l ≝
48 | cons hd tl ⇒ hd :: id_list A tl ].
51 ndefinition tail ≝ λA:Type[0].λl:list A.
56 nlet rec flatten S (l : list (list S)) on l : list S ≝
57 match l with [ nil ⇒ [ ] | cons w tl ⇒ w @ flatten ? tl ].
59 ntheorem append_nil: ∀A:Type.∀l:list A.l @ [] = l.
61 #a;#l1;#IH;nnormalize;
65 ntheorem associative_append: ∀A:Type[0].associative (list A) (append A).
68 ##|#a;#x1;#H;nnormalize;//]
71 ntheorem cons_append_commute:
72 ∀A:Type[0].∀l1,l2:list A.∀a:A.
73 a :: (l1 @ l2) = (a :: l1) @ l2.
77 nlemma append_cons: ∀A.∀a:A.∀l,l1. l@(a::l1)=(l@[a])@l1.
78 #A;#a;#l;#l1;nrewrite > (associative_append ????);//;
81 (*ninductive permutation (A:Type) : list A -> list A -> Prop \def
82 | refl : \forall l:list A. permutation ? l l
83 | swap : \forall l:list A. \forall x,y:A.
84 permutation ? (x :: y :: l) (y :: x :: l)
85 | trans : \forall l1,l2,l3:list A.
86 permutation ? l1 l2 -> permut1 ? l2 l3 -> permutation ? l1 l3
87 with permut1 : list A -> list A -> Prop \def
88 | step : \forall l1,l2:list A. \forall x,y:A.
89 permut1 ? (l1 @ (x :: y :: l2)) (l1 @ (y :: x :: l2)).*)
93 definition x1 \def S O.
94 definition x2 \def S x1.
95 definition x3 \def S x2.
97 theorem tmp : permutation nat (x1 :: x2 :: x3 :: []) (x1 :: x3 :: x2 :: []).
98 apply (trans ? (x1 :: x2 :: x3 :: []) (x1 :: x2 :: x3 :: []) ?).
100 apply (step ? (x1::[]) [] x2 x3).
103 theorem nil_append_nil_both:
104 \forall A:Type.\forall l1,l2:list A.
105 l1 @ l2 = [] \to l1 = [] \land l2 = [].
107 theorem test_notation: [O; S O; S (S O)] = O :: S O :: S (S O) :: [].
111 theorem test_append: [O;O;O;O;O;O] = [O;O;O] @ [O;O] @ [O].
118 nlet rec nth A l d n on l ≝
121 | cons (x:A) tl ⇒ match n with
123 | S n' ⇒ nth A tl d n' ] ].
125 nlet rec map A B f l on l ≝
126 match l with [ nil ⇒ nil B | cons (x:A) tl ⇒ f x :: map A B f tl ].
128 nlet rec foldr (A,B:Type[0]) (f : A → B → B) (b:B) l on l ≝
129 match l with [ nil ⇒ b | cons (a:A) tl ⇒ f a (foldr A B f b tl) ].
131 ndefinition length ≝ λT:Type[0].λl:list T.foldr T nat (λx,c.S c) O l.
134 λT:Type[0].λl:list T.λp:T → bool.
136 (λx,l0.match (p x) with [ true => x::l0 | false => l0]) [] l.
138 ndefinition iota : nat → nat → list nat ≝
139 λn,m. nat_rect_Type0 (λ_.list ?) (nil ?) (λx,acc.cons ? (n+x) acc) m.
141 (* ### induction principle for functions visiting 2 lists in parallel *)
143 ∀T1,T2:Type[0].∀l1:list T1.∀l2:list T2.∀P:list T1 → list T2 → Prop.
144 length ? l1 = length ? l2 →
145 (P (nil ?) (nil ?)) →
146 (∀tl1,tl2,hd1,hd2. P tl1 tl2 → P (hd1::tl1) (hd2::tl2)) →
148 #T1;#T2;#l1;#l2;#P;#Hl;#Pnil;#Pcons;
149 ngeneralize in match Hl; ngeneralize in match l2;
152 nnormalize;#t2;#tl2;#H;ndestruct;
153 ##|#t1;#tl1;#IH;#l2;ncases l2
154 ##[nnormalize;#H;ndestruct
155 ##|#t2;#tl2;#H;napply Pcons;napply IH;nnormalize in H;ndestruct;//]
159 nlemma eq_map : ∀A,B,f,g,l. (∀x.f x = g x) → map A B f l = map A B g l.
161 nelim l; nnormalize;//;
164 nlemma le_length_filter : ∀A,l,p.length A (filter A l p) ≤ length A l.
165 #A;#l;#p;nelim l;nnormalize
167 ##|#a;#tl;#IH;ncases (p a);nnormalize;
173 nlemma length_append : ∀A,l,m.length A (l@m) = length A l + length A m.
176 ##|#H;#tl;#IH;nnormalize;nrewrite < IH;//]
179 ninductive in_list (A:Type): A → (list A) → Prop ≝
180 | in_list_head : ∀ x,l.(in_list A x (x::l))
181 | in_list_cons : ∀ x,y,l.(in_list A x l) → (in_list A x (y::l)).
183 ndefinition incl : \forall A.(list A) \to (list A) \to Prop \def
184 \lambda A,l,m.\forall x.in_list A x l \to in_list A x m.
186 notation "hvbox(a break ∉ b)" non associative with precedence 45
187 for @{ 'notmem $a $b }.
189 interpretation "list member" 'mem x l = (in_list ? x l).
190 interpretation "list not member" 'notmem x l = (Not (in_list ? x l)).
191 interpretation "list inclusion" 'subseteq l1 l2 = (incl ? l1 l2).
193 nlemma not_in_list_nil : \forall A,x.\lnot in_list A x [].
194 #A x;@;#H1;ninversion H1;
195 ##[#a0 al0 H2 H3;ndestruct (H3);
196 ##|#a0 a1 al0 H2 H3 H4 H5;ndestruct (H5)
200 nlemma in_list_cons_case : \forall A,x,a,l.in_list A x (a::l) \to
201 x = a \lor in_list A x l.
202 #A a0 a1 al0 H1;ninversion H1
203 ##[#a2 al1 H2 H3;ndestruct (H3);@;@
204 ##|#a2 a3 al1 H2 H3 H4 H5;ndestruct (H5);@2;//
208 nlemma in_list_tail : \forall A,l,x,y.
209 in_list A x (y::l) \to x \neq y \to in_list A x l.
210 #A;#l;#x;#y;#H;#Hneq;
212 ##[#x1;#l1;#Hx;#Hl;ndestruct;nelim Hneq;#Hfalse;
214 ##|#x1;#y1;#l1;#H1;#_;#Hx;#Heq;ndestruct;//;
218 nlemma in_list_singleton_to_eq : \forall A,x,y.in_list A x [y] \to x = y.
219 #A a0 a1 H1;ncases (in_list_cons_case ???? H1)
221 ##|#H2;napply False_ind;ncases (not_in_list_nil ? a0);#H3;/2/
225 nlemma in_list_to_in_list_append_l: \forall A.\forall x:A.
226 \forall l1,l2.in_list ? x l1 \to in_list ? x (l1@l2).
227 #A a0 al0 al1 H1;nelim H1
229 ##|#a1 a2 al2 H2 H3;@2;//
233 nlemma in_list_to_in_list_append_r: \forall A.\forall x:A.
234 \forall l1,l2. in_list ? x l2 \to in_list ? x (l1@l2).
235 #A a0 al0 al1 H1;nelim al0
237 ##|#a1 al2 IH;@2;napply IH
241 nlemma in_list_append_to_or_in_list: \forall A:Type.\forall x:A.
242 \forall l,l1. in_list ? x (l@l1) \to in_list ? x l \lor in_list ? x l1.
244 ##[#al1 H1;@2;napply H1
245 ##|#a1 al1 IH al2 H1;nnormalize in H1;
246 ncases (in_list_cons_case ???? H1);#H2
248 ##|ncases (IH … H2);#H3
256 nlet rec mem (A:Type) (eq: A → A → bool) x (l: list A) on l ≝
262 | false ⇒ mem A eq x l'
266 nlemma mem_true_to_in_list :
268 (\forall x,y.equ x y = true \to x = y) \to
269 \forall x,l.mem A equ x l = true \to in_list A x l.
270 #A equ H1 a0 al0;nelim al0
271 ##[nnormalize;#H2;ndestruct (H2)
272 ##|#a1 al1 IH H2;nwhd in H2:(??%?);
273 nlapply (refl ? (equ a0 a1));ncases (equ a0 a1) in ⊢ (???% → %);#H3
274 ##[nrewrite > (H1 … H3);@
275 ##|@2;napply IH;nrewrite > H3 in H2;nnormalize;//;
280 nlemma in_list_to_mem_true :
282 (\forall x.equ x x = true) \to
283 \forall x,l.in_list A x l \to mem A equ x l = true.
284 #A equ H1 a0 al0;nelim al0
285 ##[#H2;napply False_ind;ncases (not_in_list_nil ? a0);/2/
286 ##|#a1 al1 IH H2;nelim H2
287 ##[nnormalize;#a2 al2;nrewrite > (H1 …);@
288 ##|#a2 a3 al2 H3 H4;nnormalize;ncases (equ a2 a3);nnormalize;//;
293 nlemma in_list_filter_to_p_true : \forall A,l,x,p.
294 in_list A x (filter A l p) \to p x = true.
295 #A al0 a0 p;nelim al0
296 ##[nnormalize;#H1;napply False_ind;ncases (not_in_list_nil ? a0);/2/
297 ##|#a1 al1 IH H1;nnormalize in H1;nlapply (refl ? (p a1));
298 ngeneralize in match H1;ncases (p a1) in ⊢ (???% -> ???% → %);
299 ##[#H2 H3;ncases (in_list_cons_case ???? H2);#H4
303 ##|#H2 H3;napply (IH H2);
308 nlemma in_list_filter : \forall A,l,p,x.in_list A x (filter A l p) \to in_list A x l.
309 #A al0 p a0;nelim al0
311 ##|#a1 al1 IH H1;nnormalize in H1;
312 nlapply (refl ? (p a1));ncases (p a1) in ⊢ (???% → %);#H2
313 ##[nrewrite > H2 in H1;#H1;ncases (in_list_cons_case ???? H1);#H3
315 ##|@2;napply IH;napply H3
317 ##|@2;napply IH;nrewrite > H2 in H1;#H1;napply H1;
322 nlemma in_list_filter_r : \forall A,l,p,x.
323 in_list A x l \to p x = true \to in_list A x (filter A l p).
324 #A al0 p a0;nelim al0
325 ##[#H1;napply False_ind;ncases (not_in_list_nil ? a0);/2/
326 ##|#a1 al1 IH H1 H2;ncases (in_list_cons_case ???? H1);#H3
327 ##[nnormalize;nrewrite < H3;nrewrite > H2;@
328 ##|nnormalize;ncases (p a1);nnormalize;
336 nlemma incl_A_A: ∀T,A.incl T A A.
340 nlemma incl_append_l : ∀T,A,B.incl T A (A @ B).
341 #A al0 al1 a0 H1;/2/;
344 nlemma incl_append_r : ∀T,A,B.incl T B (A @ B).
345 #A al0 al1 a0 H1;/2/;
348 nlemma incl_cons : ∀T,A,B,x.incl T A B → incl T (x::A) (x::B).
349 #A al0 al1 a0 H1 a1 H2;ncases (in_list_cons_case ???? H2);/2/;
353 nlet rec foldl (A,B:Type[0]) (f:A → B → A) (a:A) (l:list B) on l ≝
356 | cons b bl ⇒ foldl A B f (f a b) bl ].
358 nlet rec foldl2 (A,B,C:Type[0]) (f:A → B → C → A) (a:A) (bl:list B) (cl:list C) on bl ≝
361 | cons b0 bl0 ⇒ match cl with
363 | cons c0 cl0 ⇒ foldl2 A B C f (f a b0 c0) bl0 cl0 ] ].
365 nlet rec foldr2 (A,B : Type[0]) (X : Type[0]) (f: A → B → X → X) (x:X)
366 (al : list A) (bl : list B) on al : X ≝
369 | cons a al1 ⇒ match bl with
371 | cons b bl1 ⇒ f a b (foldr2 ??? f x al1 bl1) ] ].
373 nlet rec rev (A:Type[0]) (l:list A) on l ≝
376 | cons hd tl ⇒ (rev A tl)@[hd] ].
378 notation > "hvbox(a break \liff b)"
379 left associative with precedence 25
382 notation "hvbox(a break \leftrightarrow b)"
383 left associative with precedence 25
386 interpretation "logical iff" 'iff x y = (iff x y).
388 ndefinition coincl : ∀A.list A → list A → Prop ≝ λA,l1,l2.∀x.x ∈ l1 ↔ x ∈ l2.
390 notation > "hvbox(a break ≡ b)"
391 non associative with precedence 45
394 notation < "hvbox(term 46 a break ≡ term 46 b)"
395 non associative with precedence 45
398 interpretation "list coinclusion" 'equiv x y = (coincl ? x y).
400 nlemma refl_coincl : ∀A.∀l:list A.l ≡ l.
404 nlemma coincl_rev : ∀A.∀l:list A.l ≡ rev ? l.
406 ##[##1,3:#H;napply False_ind;ncases (not_in_list_nil ? x);
408 ##|#a l0 IH H;ncases (in_list_cons_case ???? H);#H1
409 ##[napply in_list_to_in_list_append_r;nrewrite > H1;@
410 ##|napply in_list_to_in_list_append_l;/2/
412 ##|#a l0 IH H;ncases (in_list_append_to_or_in_list ???? H);#H1
414 ##|nrewrite > (in_list_singleton_to_eq ??? H1);@
419 nlemma not_in_list_nil_r : ∀A.∀l:list A.l = [] → ∀x.x ∉ l.
421 ##[#;napply not_in_list_nil
422 ##|#a l0 IH Hfalse;ndestruct (Hfalse)
426 nlemma eq_filter_append :
427 ∀A,p,l1,l2.filter A (l1@l2) p = filter A l1 p@filter A l2 p.
430 ##|#a0 l0 IH;nwhd in ⊢ (??%(??%?));ncases (p a0)
431 ##[nwhd in ⊢ (??%%);nrewrite < IH;@
432 ##|nwhd in ⊢ (??%(??%?));nrewrite < IH;@
438 ∀A,B:Type[0].∀f:A→B.∀P:B → Prop.
439 ∀al.(∀a.a ∈ al → P (f a)) →
440 ∀b. b ∈ map ?? f al → P b.
442 ##[#H1 b Hfalse;napply False_ind;
443 ncases (not_in_list_nil ? b);#H2;napply H2;napply Hfalse;
444 ##|#a1 al1 IH H1 b Hin;nwhd in Hin:(???%);ncases (in_list_cons_case ???? Hin);
445 ##[#e;nrewrite > e;napply H1;@
447 ##[#a2 Hin2;napply H1;@2;//;
455 ∀A,B,C,f,g,l.map B C f (map A B g l) = map A C (λx.f (g x)) l.
458 ##|#a0 al0 IH;nchange in ⊢ (??%%) with (cons ???);
463 nlemma incl_incl_to_incl_append :
464 ∀A.∀l1,l2,l1',l2':list A.l1 ⊆ l1' → l2 ⊆ l2' → l1@l2 ⊆ l1'@l2'.
465 #A al0 al1 al2 al3 H1 H2 a0 H3;
466 ncases (in_list_append_to_or_in_list ???? H3);#H4;
467 ##[napply in_list_to_in_list_append_l;napply H1;//
468 ##|napply in_list_to_in_list_append_r;napply H2;//
472 nlemma eq_map_append :
473 ∀A,B,f,l1,l2.map A B f (l1@l2) = map A B f l1@map A B f l2.
474 #A B f al1 al2;nelim al1
476 ##|#a0 al3 IH;nnormalize;nrewrite > IH;@;
480 nlemma not_in_list_to_mem_false :
482 (∀x,y.equ x y = true → x = y) →
483 ∀x:A.∀l. x ∉ l → mem A equ x l = false.
484 #A equ H1 a0 al0;nelim al0
486 ##|#a1 al1 IH H2;nwhd in ⊢ (??%?);
487 nlapply (refl ? (equ a0 a1));ncases (equ a0 a1) in ⊢ (???% → %);#H3;
488 ##[napply False_ind;ncases H2;#H4;napply H4;
489 nrewrite > (H1 … H3);@
490 ##|napply IH;@;#H4;ncases H2;#H5;napply H5;@2;//
495 nlet rec list_forall (A:Type[0]) (l:list A) (p:A → bool) on l : bool ≝
498 | cons a al ⇒ p a ∧ list_forall A al p ].
501 ∀A,B,f,g,xl.(∀x.x ∈ xl → f x = g x) → map A B f xl = map A B g xl.
504 ##|#a al IH H1;nwhd in ⊢ (??%%);napply eq_f2
506 ##|napply IH;#x Hx;napply H1;@2;//
511 nlemma x_in_map_to_eq :
512 ∀A,B,f,x,l.x ∈ map A B f l → ∃x'.x = f x' ∧ x' ∈ l.
514 ##[#H;ncases (not_in_list_nil ? x);#H1;napply False_ind;napply (H1 H)
515 ##|#a l0 IH H;ncases (in_list_cons_case ???? H);#H1
516 ##[nrewrite > H1;@ a;@;@
517 ##|ncases (IH H1);#a0;*;#H2 H3;@a0;@
523 nlemma list_forall_false :
524 ∀A:Type[0].∀x,xl,p. p x = false → x ∈ xl → list_forall A xl p = false.
525 #A x xl p H1;nelim xl
526 ##[#Hfalse;napply False_ind;ncases (not_in_list_nil ? x);#H2;napply (H2 Hfalse)
527 ##|#x0 xl0 IH H2;ncases (in_list_cons_case ???? H2);#H3
528 ##[nwhd in ⊢ (??%?);nrewrite < H3;nrewrite > H1;@
529 ##|nwhd in ⊢ (??%?);ncases (p x0)
530 ##[nrewrite > (IH H3);@
537 nlemma list_forall_true :
538 ∀A:Type[0].∀xl,p. (∀x.x ∈ xl → p x = true) → list_forall A xl p = true.
541 ##|#x0 xl0 IH H1;nwhd in ⊢ (??%?);nrewrite > (H1 …)
542 ##[napply IH;#x Hx;napply H1;@2;//