2 ||M|| This file is part of HELM, an Hypertextual, Electronic
3 ||A|| Library of Mathematics, developed at the Computer Science
4 ||T|| Department of the University of Bologna, Italy.
7 ||A|| This file is distributed under the terms of the
8 \ / GNU General Public License Version 2
10 V_______________________________________________________________ *)
12 include "basics/types.ma".
13 include "arithmetics/div_and_mod.ma".
15 definition sameF_upto: nat → ∀A.relation(nat→A) ≝
16 λk.λA.λf,g.∀i. i < k → f i = g i.
18 definition sameF_p: nat → (nat → bool) →∀A.relation(nat→A) ≝
19 λk,p,A,f,g.∀i. i < k → p i = true → f i = g i.
21 lemma sameF_upto_le: ∀A,f,g,n,m.
22 n ≤m → sameF_upto m A f g → sameF_upto n A f g.
23 #A #f #g #n #m #lenm #samef #i #ltin @samef /2 by lt_to_le_to_lt/
26 lemma sameF_p_le: ∀A,p,f,g,n,m.
27 n ≤m → sameF_p m p A f g → sameF_p n p A f g.
28 #A #p #f #g #n #m #lenm #samef #i #ltin #pi @samef /2 by lt_to_le_to_lt/
32 definition sumF ≝ λA.λf,g:nat → A.λn,i.
33 if_then_else ? (leb n i) (g (i-n)) (f i).
35 lemma sumF_unfold: ∀A,f,g,n,i.
36 sumF A f g n i = if_then_else ? (leb n i) (g (i-n)) (f i).
40 λA,B.λf:nat→A.λg:nat→B.λm,x.〈 f(div x m), g(mod x m) 〉.
43 let rec bigop (n:nat) (p:nat → bool) (B:Type[0])
44 (nil: B) (op: B → B → B) (f: nat → B) ≝
49 [true ⇒ op (f k) (bigop k p B nil op f)
50 |false ⇒ bigop k p B nil op f]
53 notation "\big [ op , nil ]_{ ident i < n | p } f"
55 for @{'bigop $n $op $nil (λ${ident i}. $p) (λ${ident i}. $f)}.
57 notation "\big [ op , nil ]_{ ident i < n } f"
59 for @{'bigop $n $op $nil (λ${ident i}.true) (λ${ident i}. $f)}.
61 interpretation "bigop" 'bigop n op nil p f = (bigop n p ? nil op f).
63 notation "\big [ op , nil ]_{ ident j ∈ [a,b[ | p } f"
65 for @{'bigop ($b-$a) $op $nil (λ${ident j}.((λ${ident j}.$p) (${ident j}+$a)))
66 (λ${ident j}.((λ${ident j}.$f)(${ident j}+$a)))}.
68 notation "\big [ op , nil ]_{ ident j ∈ [a,b[ } f"
70 for @{'bigop ($b-$a) $op $nil (λ${ident j}.((λ${ident j}.true) (${ident j}+$a)))
71 (λ${ident j}.((λ${ident j}.$f)(${ident j}+$a)))}.
73 (* notation "\big [ op , nil ]_{( term 55) a ≤ ident j < b | p } f"
75 for @{\big[$op,$nil]_{${ident j} < ($b-$a) | ((λ${ident j}.$p) (${ident j}+$a))}((λ${ident j}.$f)(${ident j}+$a))}.
78 interpretation "bigop" 'bigop n op nil p f = (bigop n p ? nil op f).
80 lemma bigop_Strue: ∀k,p,B,nil,op.∀f:nat→B. p k = true →
81 \big[op,nil]_{i < S k | p i}(f i) =
82 op (f k) (\big[op,nil]_{i < k | p i}(f i)).
83 #k #p #B #nil #op #f #H normalize >H // qed.
85 lemma bigop_Sfalse: ∀k,p,B,nil,op.∀f:nat→B. p k = false →
86 \big[op,nil]_{ i < S k | p i}(f i) =
87 \big[op,nil]_{i < k | p i}(f i).
88 #k #p #B #nil #op #f #H normalize >H // qed.
90 lemma same_bigop : ∀k,p1,p2,B,nil,op.∀f,g:nat→B.
91 sameF_upto k bool p1 p2 → sameF_p k p1 B f g →
92 \big[op,nil]_{i < k | p1 i}(f i) =
93 \big[op,nil]_{i < k | p2 i}(g i).
94 #k #p1 #p2 #B #nil #op #f #g (elim k) //
95 #n #Hind #samep #samef normalize >Hind /2/
96 <(samep … (le_n …)) cases(true_or_false (p1 n)) #H1 >H1
97 normalize // <(samef … (le_n …) H1) //
100 theorem pad_bigop: ∀k,n,p,B,nil,op.∀f:nat→B. n ≤ k →
101 \big[op,nil]_{i < n | p i}(f i)
102 = \big[op,nil]_{i < k | if leb n i then false else p i}(f i).
103 #k #n #p #B #nil #op #f #lenk (elim lenk)
104 [@same_bigop #i #lti // >(not_le_to_leb_false …) /2/
105 |#j #leup #Hind >bigop_Sfalse >(le_to_leb_true … leup) //
108 theorem pad_bigop1: ∀k,n,p,B,nil,op.∀f:nat→B. n ≤ k →
109 (∀i. n ≤ i → i < k → p i = false) →
110 \big[op,nil]_{i < n | p i}(f i)
111 = \big[op,nil]_{i < k | p i}(f i).
112 #k #n #p #B #nil #op #f #lenk (elim lenk)
113 [#_ @same_bigop #i #lti //
114 |#j #leup #Hind #Hfalse >bigop_Sfalse
115 [@Hind #i #leni #ltij @Hfalse // @le_S //
121 theorem bigop_false: ∀n,B,nil,op.∀f:nat→B.
122 \big[op,nil]_{i < n | false }(f i) = nil.
123 #n #B #nil #op #f elim n // #n1 #Hind
127 record Aop (A:Type[0]) (nil:A) : Type[0] ≝
129 nill:∀a. op nil a = a;
130 nilr:∀a. op a nil = a;
131 assoc: ∀a,b,c.op a (op b c) = op (op a b) c
134 theorem pad_bigop_nil: ∀k,n,p,B,nil.∀op:Aop B nil.∀f:nat→B. n ≤ k →
135 (∀i. n ≤ i → i < k → p i = false ∨ f i = nil) →
136 \big[op,nil]_{i < n | p i}(f i)
137 = \big[op,nil]_{i < k | p i}(f i).
138 #k #n #p #B #nil #op #f #lenk (elim lenk)
139 [#_ @same_bigop #i #lti //
140 |#j #leup #Hind #Hfalse cases (true_or_false (p j)) #Hpj
143 [cases (Hfalse j leup (le_n … )) // >Hpj #H destruct (H)] #Hfj
144 >Hfj >nill @Hind #i #leni #ltij
145 cases (Hfalse i leni (le_S … ltij)) /2/
146 |>bigop_Sfalse // @Hind #i #leni #ltij
147 cases (Hfalse i leni (le_S … ltij)) /2/
152 theorem bigop_sum: ∀k1,k2,p1,p2,B.∀nil.∀op:Aop B nil.∀f,g:nat→B.
153 op (\big[op,nil]_{i<k1|p1 i}(f i)) \big[op,nil]_{i<k2|p2 i}(g i) =
154 \big[op,nil]_{i<k1+k2|if leb k2 i then p1 (i-k2) else p2 i}
155 (if leb k2 i then f (i-k2) else g i).
156 #k1 #k2 #p1 #p2 #B #nil #op #f #g (elim k1)
157 [normalize >nill @same_bigop #i #lti
158 >(lt_to_leb_false … lti) normalize /2/
159 |#i #Hind normalize <minus_plus_m_m (cases (p1 i))
160 >(le_to_leb_true … (le_plus_n …)) normalize <Hind //
165 lemma plus_minus1: ∀a,b,c. c ≤ b → a + (b -c) = a + b -c.
166 #a #b #c #lecb @sym_eq @plus_to_minus >(commutative_plus c)
167 >associative_plus <plus_minus_m_m //
170 theorem bigop_I: ∀n,p,B.∀nil.∀op:Aop B nil.∀f:nat→B.
171 \big[op,nil]_{i∈[0,n[ |p i}(f i) = \big[op,nil]_{i < n|p i}(f i).
172 #n #p #B #nil #op #f <minus_n_O @same_bigop //
175 theorem bigop_sumI: ∀a,b,c,p,B.∀nil.∀op:Aop B nil.∀f:nat→B.
177 \big[op,nil]_{i∈[a,c[ |p i}(f i) =
178 op (\big[op,nil]_{i ∈ [b,c[ |p i}(f i))
179 \big[op,nil]_{i ∈ [a,b[ |p i}(f i).
180 #a #b # c #p #B #nil #op #f #leab #lebc
181 >(plus_minus_m_m (c-a) (b-a)) in ⊢ (??%?); /2/
182 >minus_plus >(commutative_plus a) <plus_minus_m_m //
183 >bigop_sum (cut (∀i. b -a ≤ i → i+a = i-(b-a)+b))
184 [#i #lei >plus_minus // <plus_minus1
185 [@eq_f @sym_eq @plus_to_minus /2/ | /2/]]
186 #H @same_bigop #i #ltic @leb_elim normalize // #lei <H //
189 theorem bigop_a: ∀a,b,B.∀nil.∀op:Aop B nil.∀f:nat→B. a ≤ b →
190 \big[op,nil]_{i∈[a,S b[ }(f i) =
191 op (\big[op,nil]_{i ∈ [a,b[ }(f (S i))) (f a).
192 #a #b #B #nil #op #f #leab
193 >(bigop_sumI a (S a) (S b)) [|@le_S_S //|//] @eq_f2
194 [@same_bigop // |<minus_Sn_n normalize @nilr]
197 theorem bigop_0: ∀n,B.∀nil.∀op:Aop B nil.∀f:nat→B.
198 \big[op,nil]_{i < S n}(f i) =
199 op (\big[op,nil]_{i < n}(f (S i))) (f 0).
201 <bigop_I >bigop_a [|//] @eq_f2 [|//] <minus_n_O
205 theorem bigop_prod: ∀k1,k2,p1,p2,B.∀nil.∀op:Aop B nil.∀f: nat →nat → B.
206 \big[op,nil]_{x<k1|p1 x}(\big[op,nil]_{i<k2|p2 x i}(f x i)) =
207 \big[op,nil]_{i<k1*k2|andb (p1 (i/k2)) (p2 (i/k2) (i \mod k2))}
208 (f (i/k2) (i \mod k2)).
209 #k1 #k2 #p1 #p2 #B #nil #op #f (elim k1) //
210 #n #Hind cases(true_or_false (p1 n)) #Hp1
211 [>bigop_Strue // >Hind >bigop_sum @same_bigop
212 #i #lti @leb_elim // #lei cut (i = n*k2+(i-n*k2)) /2 by plus_minus/
213 #eqi [|#H] >eqi in ⊢ (???%);
214 >div_plus_times /2 by monotonic_lt_minus_l/
215 >Hp1 >(mod_plus_times …) /2 by refl, monotonic_lt_minus_l, eq_f/
216 |>bigop_Sfalse // >Hind >(pad_bigop (S n*k2)) // @same_bigop
217 #i #lti @leb_elim // #lei cut (i = n*k2+(i-n*k2)) /2/
218 #eqi >eqi in ⊢ (???%); >div_plus_times /2/
222 record ACop (A:Type[0]) (nil:A) : Type[0] ≝
224 comm: ∀a,b.aop a b = aop b a
227 lemma bigop_op: ∀k,p,B.∀nil.∀op:ACop B nil.∀f,g: nat → B.
228 op (\big[op,nil]_{i<k|p i}(f i)) (\big[op,nil]_{i<k|p i}(g i)) =
229 \big[op,nil]_{i<k|p i}(op (f i) (g i)).
230 #k #p #B #nil #op #f #g (elim k) [normalize @nill]
231 -k #k #Hind (cases (true_or_false (p k))) #H
232 [>bigop_Strue // >bigop_Strue // >bigop_Strue //
233 normalize <assoc <assoc in ⊢ (???%); @eq_f >assoc >comm in ⊢ (??(????%?)?);
235 |>bigop_Sfalse // >bigop_Sfalse // >bigop_Sfalse //
239 lemma bigop_diff: ∀p,B.∀nil.∀op:ACop B nil.∀f:nat → B.∀i,n.
241 \big[op,nil]_{x<n|p x}(f x)=
242 op (f i) (\big[op,nil]_{x<n|andb(notb(eqb i x))(p x)}(f x)).
243 #p #B #nil #op #f #i #n (elim n)
245 |#n #Hind #lein #pi cases (le_to_or_lt_eq … (le_S_S_to_le …lein)) #Hi
246 [cut (andb(notb(eqb i n))(p n) = (p n))
247 [>(not_eq_to_eqb_false … (lt_to_not_eq … Hi)) //] #Hcut
248 cases (true_or_false (p n)) #pn
249 [>bigop_Strue // >bigop_Strue //
250 normalize >assoc >(comm ?? op (f i) (f n)) <assoc >Hind //
251 |>bigop_Sfalse // >bigop_Sfalse // >Hind //
253 |<Hi >bigop_Strue // @eq_f >bigop_Sfalse
254 [@same_bigop // #k #ltki >not_eq_to_eqb_false /2/
262 record range (A:Type[0]): Type[0] ≝
263 {enum:nat→A; upto:nat; filter:nat→bool}.
265 definition sub_hk: (nat→nat)→(nat→nat)→∀A:Type[0].relation (range A) ≝
266 λh,k,A,I,J.∀i.i<(upto A I) → (filter A I i)=true →
268 ∧ filter A J (h i) = true
271 definition iso: ∀A:Type[0].relation (range A) ≝
273 (∀i. i < (upto A I) → (filter A I i) = true →
274 enum A I i = enum A J (h i)) ∧
275 sub_hk h k A I J ∧ sub_hk k h A J I.
277 lemma sub_hkO: ∀h,k,A,I,J. upto A I = 0 → sub_hk h k A I J.
278 #h #k #A #I #J #up0 #i #lti >up0 @False_ind /2/
281 lemma sub0_to_false: ∀h,k,A,I,J. upto A I = 0 → sub_hk h k A J I →
282 ∀i. i < upto A J → filter A J i = false.
283 #h #k #A #I #J #up0 #sub #i #lti cases(true_or_false (filter A J i)) //
284 #ptrue (cases (sub i lti ptrue)) * #hi @False_ind /2/
287 lemma sub_lt: ∀A,e,p,n,m. n ≤ m →
288 sub_hk (λx.x) (λx.x) A (mk_range A e n p) (mk_range A e m p).
289 #A #e #f #n #m #lenm #i #lti #fi % // % /2 by lt_to_le_to_lt/
292 theorem transitive_sub: ∀h1,k1,h2,k2,A,I,J,K.
293 sub_hk h1 k1 A I J → sub_hk h2 k2 A J K →
294 sub_hk (λx.h2(h1 x)) (λx.k1(k2 x)) A I K.
295 #h1 #k1 #h2 #k2 #A #I #J #K #sub1 #sub2 #i #lti #fi
296 cases(sub1 i lti fi) * #lth1i #fh1i #ei
297 cases(sub2 (h1 i) lth1i fh1i) * #H1 #H2 #H3 % // % //
300 theorem bigop_iso: ∀n1,n2,p1,p2,B.∀nil.∀op:ACop B nil.∀f1,f2.
301 iso B (mk_range B f1 n1 p1) (mk_range B f2 n2 p2) →
302 \big[op,nil]_{i<n1|p1 i}(f1 i) = \big[op,nil]_{i<n2|p2 i}(f2 i).
303 #n1 #n2 #p1 #p2 #B #nil #op #f1 #f2 * #h * #k * * #same
304 @(le_gen ? n1) #i lapply p2 (elim i)
305 [(elim n2) // #m #Hind #p2 #_ #sub1 #sub2
307 [@(Hind ? (le_O_n ?)) [/2/ | @(transitive_sub … (sub_lt …) sub2) //]
308 |@(sub0_to_false … sub2) //
310 |#n #Hind #p2 #ltn #sub1 #sub2 (cut (n ≤n1)) [/2/] #len
311 cases(true_or_false (p1 n)) #p1n
312 [>bigop_Strue // (cases (sub1 n (le_n …) p1n)) * #hn #p2hn #eqn
313 >(bigop_diff … (h n) n2) // >same //
315 [#i #ltin #p1i (cases (sub1 i (le_S … ltin) p1i)) *
316 #h1i #p2h1i #eqi % // % // >not_eq_to_eqb_false normalize //
317 @(not_to_not ??? (lt_to_not_eq ? ? ltin)) //
318 |#j #ltj #p2j (cases (sub2 j ltj (andb_true_r …p2j))) *
319 #ltkj #p1kj #eqj % // % //
320 (cases (le_to_or_lt_eq …(le_S_S_to_le …ltkj))) //
321 #eqkj @False_ind lapply p2j @eqb_elim
324 |>bigop_Sfalse // @(Hind ? len)
325 [@(transitive_sub … (sub_lt …) sub1) //
326 |#i #lti #p2i cases(sub2 i lti p2i) * #ltki #p1ki #eqi
327 % // % // cases(le_to_or_lt_eq …(le_S_S_to_le …ltki)) //
334 (* lemma div_mod_exchange: ∀i,n,m. i < n*m → i\n = i mod m. *)
337 theorem bigop_commute: ∀n,m,p11,p12,p21,p22,B.∀nil.∀op:ACop B nil.∀f.
339 (∀i,j. i < n → j < m → (p11 i ∧ p12 i j) = (p21 j ∧ p22 i j)) →
340 \big[op,nil]_{i<n|p11 i}(\big[op,nil]_{j<m|p12 i j}(f i j)) =
341 \big[op,nil]_{j<m|p21 j}(\big[op,nil]_{i<n|p22 i j}(f i j)).
342 #n #m #p11 #p12 #p21 #p22 #B #nil #op #f #posn #posm #Heq
343 >bigop_prod >bigop_prod @bigop_iso
344 %{(λi.(i\mod m)*n + i/m)} %{(λi.(i\mod n)*m + i/n)} %
346 [#i #lti #Heq (* whd in ⊢ (???(?(?%?)?)); *) @eq_f2
347 [@sym_eq @mod_plus_times /2 by lt_times_to_lt_div/
348 |@sym_eq @div_plus_times /2 by lt_times_to_lt_div/
351 cut ((i\mod m*n+i/m)\mod n=i/m)
352 [@mod_plus_times @lt_times_to_lt_div //] #H1
353 cut ((i\mod m*n+i/m)/n=i \mod m)
354 [@div_plus_times @lt_times_to_lt_div //] #H2
355 %[%[@(lt_to_le_to_lt ? (i\mod m*n+n))
356 [whd >plus_n_Sm @monotonic_le_plus_r @lt_times_to_lt_div //
357 |>commutative_plus @(le_times (S(i \mod m)) m n n) // @lt_mod_m_m //
359 |lapply (Heq (i/m) (i \mod m) ??)
360 [@lt_mod_m_m // |@lt_times_to_lt_div //|>Hi >H1 >H2 //]
366 cut ((i\mod n*m+i/n)\mod m=i/n)
367 [@mod_plus_times @lt_times_to_lt_div //] #H1
368 cut ((i\mod n*m+i/n)/m=i \mod n)
369 [@div_plus_times @lt_times_to_lt_div //] #H2
370 %[%[@(lt_to_le_to_lt ? (i\mod n*m+m))
371 [whd >plus_n_Sm @monotonic_le_plus_r @lt_times_to_lt_div //
372 |>commutative_plus @(le_times (S(i \mod n)) n m m) // @lt_mod_m_m //
374 |lapply (Heq (i \mod n) (i/n) ??)
375 [@lt_times_to_lt_div // |@lt_mod_m_m // |>Hi >H1 >H2 //]
384 record Dop (A:Type[0]) (nil:A): Type[0] ≝
387 null: \forall a. prod a nil = nil;
388 distr: ∀a,b,c:A. prod a (sum b c) = sum (prod a b) (prod a c)
391 theorem bigop_distr: ∀n,p,B,nil.∀R:Dop B nil.∀f,a.
392 let aop ≝ sum B nil R in
393 let mop ≝ prod B nil R in
394 mop a \big[aop,nil]_{i<n|p i}(f i) =
395 \big[aop,nil]_{i<n|p i}(mop a (f i)).
396 #n #p #B #nil #R #f #a normalize (elim n) [@null]
397 #n #Hind (cases (true_or_false (p n))) #H
398 [>bigop_Strue // >bigop_Strue // >(distr B nil R) >Hind //
399 |>bigop_Sfalse // >bigop_Sfalse //