Tuned (for the sake of a meaningless log entry).
2 Title: HOL/Algebra/UnivPoly.thy
4 Author: Clemens Ballarin, started 9 December 1996
5 Copyright: Clemens Ballarin
8 theory UnivPoly imports Module begin
11 section {* Univariate Polynomials *}
14 Polynomials are formalised as modules with additional operations for
15 extracting coefficients from polynomials and for obtaining monomials
16 from coefficients and exponents (record @{text "up_ring"}). The
17 carrier set is a set of bounded functions from Nat to the
18 coefficient domain. Bounded means that these functions return zero
19 above a certain bound (the degree). There is a chapter on the
20 formalisation of polynomials in the PhD thesis \cite{Ballarin:1999},
21 which was implemented with axiomatic type classes. This was later
26 subsection {* The Constructor for Univariate Polynomials *}
29 Functions with finite support.
36 assumes bound: "!!m. n < m \<Longrightarrow> f m = z"
38 declare bound.intro [intro!]
39 and bound.bound [dest]
42 assumes bound: "bound z m f" and nonzero: "f n \<noteq> z" shows "n \<le> m"
43 proof (rule classical)
45 then have "m < n" by arith
46 with bound have "f n = z" ..
47 with nonzero show ?thesis by contradiction
50 record ('a, 'p) up_ring = "('a, 'p) module" +
51 monom :: "['a, nat] => 'p"
52 coeff :: "['p, nat] => 'a"
54 constdefs (structure R)
55 up :: "('a, 'm) ring_scheme => (nat => 'a) set"
56 "up R == {f. f \<in> UNIV -> carrier R & (EX n. bound \<zero> n f)}"
57 UP :: "('a, 'm) ring_scheme => ('a, nat => 'a) up_ring"
60 mult = (%p:up R. %q:up R. %n. \<Oplus>i \<in> {..n}. p i \<otimes> q (n-i)),
61 one = (%i. if i=0 then \<one> else \<zero>),
63 add = (%p:up R. %q:up R. %i. p i \<oplus> q i),
64 smult = (%a:carrier R. %p:up R. %i. a \<otimes> p i),
65 monom = (%a:carrier R. %n i. if i=n then a else \<zero>),
66 coeff = (%p:up R. %n. p n) |)"
69 Properties of the set of polynomials @{term up}.
72 lemma mem_upI [intro]:
73 "[| !!n. f n \<in> carrier R; EX n. bound (zero R) n f |] ==> f \<in> up R"
74 by (simp add: up_def Pi_def)
77 "f \<in> up R ==> f n \<in> carrier R"
78 by (simp add: up_def Pi_def)
80 lemma (in cring) bound_upD [dest]:
81 "f \<in> up R ==> EX n. bound \<zero> n f"
84 lemma (in cring) up_one_closed:
85 "(%n. if n = 0 then \<one> else \<zero>) \<in> up R"
88 lemma (in cring) up_smult_closed:
89 "[| a \<in> carrier R; p \<in> up R |] ==> (%i. a \<otimes> p i) \<in> up R"
92 lemma (in cring) up_add_closed:
93 "[| p \<in> up R; q \<in> up R |] ==> (%i. p i \<oplus> q i) \<in> up R"
96 assume "p \<in> up R" and "q \<in> up R"
97 then show "p n \<oplus> q n \<in> carrier R"
100 assume UP: "p \<in> up R" "q \<in> up R"
101 show "EX n. bound \<zero> n (%i. p i \<oplus> q i)"
103 from UP obtain n where boundn: "bound \<zero> n p" by fast
104 from UP obtain m where boundm: "bound \<zero> m q" by fast
105 have "bound \<zero> (max n m) (%i. p i \<oplus> q i)"
109 with boundn and boundm and UP show "p i \<oplus> q i = \<zero>" by fastsimp
115 lemma (in cring) up_a_inv_closed:
116 "p \<in> up R ==> (%i. \<ominus> (p i)) \<in> up R"
118 assume R: "p \<in> up R"
119 then obtain n where "bound \<zero> n p" by auto
120 then have "bound \<zero> n (%i. \<ominus> p i)" by auto
121 then show "EX n. bound \<zero> n (%i. \<ominus> p i)" by auto
124 lemma (in cring) up_mult_closed:
125 "[| p \<in> up R; q \<in> up R |] ==>
126 (%n. \<Oplus>i \<in> {..n}. p i \<otimes> q (n-i)) \<in> up R"
129 assume "p \<in> up R" "q \<in> up R"
130 then show "(\<Oplus>i \<in> {..n}. p i \<otimes> q (n-i)) \<in> carrier R"
131 by (simp add: mem_upD funcsetI)
133 assume UP: "p \<in> up R" "q \<in> up R"
134 show "EX n. bound \<zero> n (%n. \<Oplus>i \<in> {..n}. p i \<otimes> q (n-i))"
136 from UP obtain n where boundn: "bound \<zero> n p" by fast
137 from UP obtain m where boundm: "bound \<zero> m q" by fast
138 have "bound \<zero> (n + m) (%n. \<Oplus>i \<in> {..n}. p i \<otimes> q (n - i))"
140 fix k assume bound: "n + m < k"
143 have "p i \<otimes> q (k-i) = \<zero>"
144 proof (cases "n < i")
146 with boundn have "p i = \<zero>" by auto
147 moreover from UP have "q (k-i) \<in> carrier R" by auto
148 ultimately show ?thesis by simp
151 with bound have "m < k-i" by arith
152 with boundm have "q (k-i) = \<zero>" by auto
153 moreover from UP have "p i \<in> carrier R" by auto
154 ultimately show ?thesis by simp
157 then show "(\<Oplus>i \<in> {..k}. p i \<otimes> q (k-i)) = \<zero>"
158 by (simp add: Pi_def)
160 then show ?thesis by fast
165 subsection {* Effect of Operations on Coefficients *}
168 fixes R (structure) and P (structure)
169 defines P_def: "P == UP R"
171 locale UP_cring = UP + cring R
173 locale UP_domain = UP_cring + "domain" R
176 Temporarily declare @{thm [locale=UP] P_def} as simp rule.
179 declare (in UP) P_def [simp]
181 lemma (in UP_cring) coeff_monom [simp]:
182 "a \<in> carrier R ==>
183 coeff P (monom P a m) n = (if m=n then a else \<zero>)"
185 assume R: "a \<in> carrier R"
186 then have "(%n. if n = m then a else \<zero>) \<in> up R"
187 using up_def by force
188 with R show ?thesis by (simp add: UP_def)
191 lemma (in UP_cring) coeff_zero [simp]:
192 "coeff P \<zero>\<^bsub>P\<^esub> n = \<zero>"
193 by (auto simp add: UP_def)
195 lemma (in UP_cring) coeff_one [simp]:
196 "coeff P \<one>\<^bsub>P\<^esub> n = (if n=0 then \<one> else \<zero>)"
197 using up_one_closed by (simp add: UP_def)
199 lemma (in UP_cring) coeff_smult [simp]:
200 "[| a \<in> carrier R; p \<in> carrier P |] ==>
201 coeff P (a \<odot>\<^bsub>P\<^esub> p) n = a \<otimes> coeff P p n"
202 by (simp add: UP_def up_smult_closed)
204 lemma (in UP_cring) coeff_add [simp]:
205 "[| p \<in> carrier P; q \<in> carrier P |] ==>
206 coeff P (p \<oplus>\<^bsub>P\<^esub> q) n = coeff P p n \<oplus> coeff P q n"
207 by (simp add: UP_def up_add_closed)
209 lemma (in UP_cring) coeff_mult [simp]:
210 "[| p \<in> carrier P; q \<in> carrier P |] ==>
211 coeff P (p \<otimes>\<^bsub>P\<^esub> q) n = (\<Oplus>i \<in> {..n}. coeff P p i \<otimes> coeff P q (n-i))"
212 by (simp add: UP_def up_mult_closed)
214 lemma (in UP) up_eqI:
215 assumes prem: "!!n. coeff P p n = coeff P q n"
216 and R: "p \<in> carrier P" "q \<in> carrier P"
220 from prem and R show "p x = q x" by (simp add: UP_def)
224 subsection {* Polynomials Form a Commutative Ring. *}
226 text {* Operations are closed over @{term P}. *}
228 lemma (in UP_cring) UP_mult_closed [simp]:
229 "[| p \<in> carrier P; q \<in> carrier P |] ==> p \<otimes>\<^bsub>P\<^esub> q \<in> carrier P"
230 by (simp add: UP_def up_mult_closed)
232 lemma (in UP_cring) UP_one_closed [simp]:
233 "\<one>\<^bsub>P\<^esub> \<in> carrier P"
234 by (simp add: UP_def up_one_closed)
236 lemma (in UP_cring) UP_zero_closed [intro, simp]:
237 "\<zero>\<^bsub>P\<^esub> \<in> carrier P"
238 by (auto simp add: UP_def)
240 lemma (in UP_cring) UP_a_closed [intro, simp]:
241 "[| p \<in> carrier P; q \<in> carrier P |] ==> p \<oplus>\<^bsub>P\<^esub> q \<in> carrier P"
242 by (simp add: UP_def up_add_closed)
244 lemma (in UP_cring) monom_closed [simp]:
245 "a \<in> carrier R ==> monom P a n \<in> carrier P"
246 by (auto simp add: UP_def up_def Pi_def)
248 lemma (in UP_cring) UP_smult_closed [simp]:
249 "[| a \<in> carrier R; p \<in> carrier P |] ==> a \<odot>\<^bsub>P\<^esub> p \<in> carrier P"
250 by (simp add: UP_def up_smult_closed)
252 lemma (in UP) coeff_closed [simp]:
253 "p \<in> carrier P ==> coeff P p n \<in> carrier R"
254 by (auto simp add: UP_def)
256 declare (in UP) P_def [simp del]
258 text {* Algebraic ring properties *}
260 lemma (in UP_cring) UP_a_assoc:
261 assumes R: "p \<in> carrier P" "q \<in> carrier P" "r \<in> carrier P"
262 shows "(p \<oplus>\<^bsub>P\<^esub> q) \<oplus>\<^bsub>P\<^esub> r = p \<oplus>\<^bsub>P\<^esub> (q \<oplus>\<^bsub>P\<^esub> r)"
263 by (rule up_eqI, simp add: a_assoc R, simp_all add: R)
265 lemma (in UP_cring) UP_l_zero [simp]:
266 assumes R: "p \<in> carrier P"
267 shows "\<zero>\<^bsub>P\<^esub> \<oplus>\<^bsub>P\<^esub> p = p"
268 by (rule up_eqI, simp_all add: R)
270 lemma (in UP_cring) UP_l_neg_ex:
271 assumes R: "p \<in> carrier P"
272 shows "EX q : carrier P. q \<oplus>\<^bsub>P\<^esub> p = \<zero>\<^bsub>P\<^esub>"
274 let ?q = "%i. \<ominus> (p i)"
275 from R have closed: "?q \<in> carrier P"
276 by (simp add: UP_def P_def up_a_inv_closed)
277 from R have coeff: "!!n. coeff P ?q n = \<ominus> (coeff P p n)"
278 by (simp add: UP_def P_def up_a_inv_closed)
281 show "?q \<oplus>\<^bsub>P\<^esub> p = \<zero>\<^bsub>P\<^esub>"
282 by (auto intro!: up_eqI simp add: R closed coeff R.l_neg)
286 lemma (in UP_cring) UP_a_comm:
287 assumes R: "p \<in> carrier P" "q \<in> carrier P"
288 shows "p \<oplus>\<^bsub>P\<^esub> q = q \<oplus>\<^bsub>P\<^esub> p"
289 by (rule up_eqI, simp add: a_comm R, simp_all add: R)
291 lemma (in UP_cring) UP_m_assoc:
292 assumes R: "p \<in> carrier P" "q \<in> carrier P" "r \<in> carrier P"
293 shows "(p \<otimes>\<^bsub>P\<^esub> q) \<otimes>\<^bsub>P\<^esub> r = p \<otimes>\<^bsub>P\<^esub> (q \<otimes>\<^bsub>P\<^esub> r)"
297 fix k and a b c :: "nat=>'a"
298 assume R: "a \<in> UNIV -> carrier R" "b \<in> UNIV -> carrier R"
299 "c \<in> UNIV -> carrier R"
300 then have "k <= n ==>
301 (\<Oplus>j \<in> {..k}. (\<Oplus>i \<in> {..j}. a i \<otimes> b (j-i)) \<otimes> c (n-j)) =
302 (\<Oplus>j \<in> {..k}. a j \<otimes> (\<Oplus>i \<in> {..k-j}. b i \<otimes> c (n-j-i)))"
303 (is "_ \<Longrightarrow> ?eq k")
305 case 0 then show ?case by (simp add: Pi_def m_assoc)
308 then have "k <= n" by arith
309 from this R have "?eq k" by (rule Suc)
311 by (simp cong: finsum_cong
312 add: Suc_diff_le Pi_def l_distr r_distr m_assoc)
313 (simp cong: finsum_cong add: Pi_def a_ac finsum_ldistr m_assoc)
316 with R show "coeff P ((p \<otimes>\<^bsub>P\<^esub> q) \<otimes>\<^bsub>P\<^esub> r) n = coeff P (p \<otimes>\<^bsub>P\<^esub> (q \<otimes>\<^bsub>P\<^esub> r)) n"
317 by (simp add: Pi_def)
318 qed (simp_all add: R)
320 lemma (in UP_cring) UP_l_one [simp]:
321 assumes R: "p \<in> carrier P"
322 shows "\<one>\<^bsub>P\<^esub> \<otimes>\<^bsub>P\<^esub> p = p"
325 show "coeff P (\<one>\<^bsub>P\<^esub> \<otimes>\<^bsub>P\<^esub> p) n = coeff P p n"
327 case 0 with R show ?thesis by simp
329 case Suc with R show ?thesis
330 by (simp del: finsum_Suc add: finsum_Suc2 Pi_def)
332 qed (simp_all add: R)
334 lemma (in UP_cring) UP_l_distr:
335 assumes R: "p \<in> carrier P" "q \<in> carrier P" "r \<in> carrier P"
336 shows "(p \<oplus>\<^bsub>P\<^esub> q) \<otimes>\<^bsub>P\<^esub> r = (p \<otimes>\<^bsub>P\<^esub> r) \<oplus>\<^bsub>P\<^esub> (q \<otimes>\<^bsub>P\<^esub> r)"
337 by (rule up_eqI) (simp add: l_distr R Pi_def, simp_all add: R)
339 lemma (in UP_cring) UP_m_comm:
340 assumes R: "p \<in> carrier P" "q \<in> carrier P"
341 shows "p \<otimes>\<^bsub>P\<^esub> q = q \<otimes>\<^bsub>P\<^esub> p"
345 fix k and a b :: "nat=>'a"
346 assume R: "a \<in> UNIV -> carrier R" "b \<in> UNIV -> carrier R"
347 then have "k <= n ==>
348 (\<Oplus>i \<in> {..k}. a i \<otimes> b (n-i)) =
349 (\<Oplus>i \<in> {..k}. a (k-i) \<otimes> b (i+n-k))"
350 (is "_ \<Longrightarrow> ?eq k")
352 case 0 then show ?case by (simp add: Pi_def)
354 case (Suc k) then show ?case
355 by (subst (2) finsum_Suc2) (simp add: Pi_def a_comm)+
359 from R show "coeff P (p \<otimes>\<^bsub>P\<^esub> q) n = coeff P (q \<otimes>\<^bsub>P\<^esub> p) n"
360 apply (simp add: Pi_def)
362 apply (auto simp add: Pi_def)
363 apply (simp add: m_comm)
365 qed (simp_all add: R)
367 theorem (in UP_cring) UP_cring:
369 by (auto intro!: cringI abelian_groupI comm_monoidI UP_a_assoc UP_l_zero
370 UP_l_neg_ex UP_a_comm UP_m_assoc UP_l_one UP_m_comm UP_l_distr)
372 lemma (in UP_cring) UP_ring:
374 we want "UP_ring R P ==> ring P", not "UP_cring R P ==> ring P" *)
376 by (auto intro: ring.intro cring.axioms UP_cring)
378 lemma (in UP_cring) UP_a_inv_closed [intro, simp]:
379 "p \<in> carrier P ==> \<ominus>\<^bsub>P\<^esub> p \<in> carrier P"
380 by (rule abelian_group.a_inv_closed
381 [OF ring.is_abelian_group [OF UP_ring]])
383 lemma (in UP_cring) coeff_a_inv [simp]:
384 assumes R: "p \<in> carrier P"
385 shows "coeff P (\<ominus>\<^bsub>P\<^esub> p) n = \<ominus> (coeff P p n)"
387 from R coeff_closed UP_a_inv_closed have
388 "coeff P (\<ominus>\<^bsub>P\<^esub> p) n = \<ominus> coeff P p n \<oplus> (coeff P p n \<oplus> coeff P (\<ominus>\<^bsub>P\<^esub> p) n)"
390 also from R have "... = \<ominus> (coeff P p n)"
391 by (simp del: coeff_add add: coeff_add [THEN sym]
392 abelian_group.r_neg [OF ring.is_abelian_group [OF UP_ring]])
393 finally show ?thesis .
397 Interpretation of lemmas from @{term cring}. Saves lifting 43
401 interpretation UP_cring < cring P
403 (rule cring.axioms ring.axioms abelian_group.axioms comm_monoid.axioms UP_cring)+
406 subsection {* Polynomials Form an Algebra *}
408 lemma (in UP_cring) UP_smult_l_distr:
409 "[| a \<in> carrier R; b \<in> carrier R; p \<in> carrier P |] ==>
410 (a \<oplus> b) \<odot>\<^bsub>P\<^esub> p = a \<odot>\<^bsub>P\<^esub> p \<oplus>\<^bsub>P\<^esub> b \<odot>\<^bsub>P\<^esub> p"
411 by (rule up_eqI) (simp_all add: R.l_distr)
413 lemma (in UP_cring) UP_smult_r_distr:
414 "[| a \<in> carrier R; p \<in> carrier P; q \<in> carrier P |] ==>
415 a \<odot>\<^bsub>P\<^esub> (p \<oplus>\<^bsub>P\<^esub> q) = a \<odot>\<^bsub>P\<^esub> p \<oplus>\<^bsub>P\<^esub> a \<odot>\<^bsub>P\<^esub> q"
416 by (rule up_eqI) (simp_all add: R.r_distr)
418 lemma (in UP_cring) UP_smult_assoc1:
419 "[| a \<in> carrier R; b \<in> carrier R; p \<in> carrier P |] ==>
420 (a \<otimes> b) \<odot>\<^bsub>P\<^esub> p = a \<odot>\<^bsub>P\<^esub> (b \<odot>\<^bsub>P\<^esub> p)"
421 by (rule up_eqI) (simp_all add: R.m_assoc)
423 lemma (in UP_cring) UP_smult_one [simp]:
424 "p \<in> carrier P ==> \<one> \<odot>\<^bsub>P\<^esub> p = p"
425 by (rule up_eqI) simp_all
427 lemma (in UP_cring) UP_smult_assoc2:
428 "[| a \<in> carrier R; p \<in> carrier P; q \<in> carrier P |] ==>
429 (a \<odot>\<^bsub>P\<^esub> p) \<otimes>\<^bsub>P\<^esub> q = a \<odot>\<^bsub>P\<^esub> (p \<otimes>\<^bsub>P\<^esub> q)"
430 by (rule up_eqI) (simp_all add: R.finsum_rdistr R.m_assoc Pi_def)
433 Interpretation of lemmas from @{term algebra}.
436 lemma (in cring) cring:
440 lemma (in UP_cring) UP_algebra:
442 by (auto intro: algebraI R.cring UP_cring UP_smult_l_distr UP_smult_r_distr
443 UP_smult_assoc1 UP_smult_assoc2)
445 interpretation UP_cring < algebra R P
447 (rule module.axioms algebra.axioms UP_algebra)+
450 subsection {* Further Lemmas Involving Monomials *}
452 lemma (in UP_cring) monom_zero [simp]:
453 "monom P \<zero> n = \<zero>\<^bsub>P\<^esub>"
454 by (simp add: UP_def P_def)
456 lemma (in UP_cring) monom_mult_is_smult:
457 assumes R: "a \<in> carrier R" "p \<in> carrier P"
458 shows "monom P a 0 \<otimes>\<^bsub>P\<^esub> p = a \<odot>\<^bsub>P\<^esub> p"
461 have "coeff P (p \<otimes>\<^bsub>P\<^esub> monom P a 0) n = coeff P (a \<odot>\<^bsub>P\<^esub> p) n"
463 case 0 with R show ?thesis by (simp add: R.m_comm)
465 case Suc with R show ?thesis
466 by (simp cong: R.finsum_cong add: R.r_null Pi_def)
469 with R show "coeff P (monom P a 0 \<otimes>\<^bsub>P\<^esub> p) n = coeff P (a \<odot>\<^bsub>P\<^esub> p) n"
470 by (simp add: UP_m_comm)
471 qed (simp_all add: R)
473 lemma (in UP_cring) monom_add [simp]:
474 "[| a \<in> carrier R; b \<in> carrier R |] ==>
475 monom P (a \<oplus> b) n = monom P a n \<oplus>\<^bsub>P\<^esub> monom P b n"
476 by (rule up_eqI) simp_all
478 lemma (in UP_cring) monom_one_Suc:
479 "monom P \<one> (Suc n) = monom P \<one> n \<otimes>\<^bsub>P\<^esub> monom P \<one> 1"
482 show "coeff P (monom P \<one> (Suc n)) k = coeff P (monom P \<one> n \<otimes>\<^bsub>P\<^esub> monom P \<one> 1) k"
483 proof (cases "k = Suc n")
484 case True show ?thesis
487 from True have less_add_diff:
488 "!!i. [| n < i; i <= n + m |] ==> n + m - i < m" by arith
489 from True have "coeff P (monom P \<one> (Suc n)) k = \<one>" by simp
491 have "... = (\<Oplus>i \<in> {..<n} \<union> {n}. coeff P (monom P \<one> n) i \<otimes>
492 coeff P (monom P \<one> 1) (k - i))"
493 by (simp cong: R.finsum_cong add: Pi_def)
494 also have "... = (\<Oplus>i \<in> {..n}. coeff P (monom P \<one> n) i \<otimes>
495 coeff P (monom P \<one> 1) (k - i))"
496 by (simp only: ivl_disj_un_singleton)
498 have "... = (\<Oplus>i \<in> {..n} \<union> {n<..k}. coeff P (monom P \<one> n) i \<otimes>
499 coeff P (monom P \<one> 1) (k - i))"
500 by (simp cong: R.finsum_cong add: R.finsum_Un_disjoint ivl_disj_int_one
501 order_less_imp_not_eq Pi_def)
502 also from True have "... = coeff P (monom P \<one> n \<otimes>\<^bsub>P\<^esub> monom P \<one> 1) k"
503 by (simp add: ivl_disj_un_one)
504 finally show ?thesis .
510 "\<lambda>i. (if n = i then \<one> else \<zero>) \<otimes> (if Suc 0 = k - i then \<one> else \<zero>)"
511 from neq have "coeff P (monom P \<one> (Suc n)) k = \<zero>" by simp
512 also have "... = (\<Oplus>i \<in> {..k}. ?s i)"
514 have f1: "(\<Oplus>i \<in> {..<n}. ?s i) = \<zero>"
515 by (simp cong: R.finsum_cong add: Pi_def)
516 from neq have f2: "(\<Oplus>i \<in> {n}. ?s i) = \<zero>"
517 by (simp cong: R.finsum_cong add: Pi_def) arith
518 have f3: "n < k ==> (\<Oplus>i \<in> {n<..k}. ?s i) = \<zero>"
519 by (simp cong: R.finsum_cong add: order_less_imp_not_eq Pi_def)
521 proof (cases "k < n")
522 case True then show ?thesis by (simp cong: R.finsum_cong add: Pi_def)
524 case False then have n_le_k: "n <= k" by arith
526 proof (cases "n = k")
528 then have "\<zero> = (\<Oplus>i \<in> {..<n} \<union> {n}. ?s i)"
529 by (simp cong: R.finsum_cong add: ivl_disj_int_singleton Pi_def)
530 also from True have "... = (\<Oplus>i \<in> {..k}. ?s i)"
531 by (simp only: ivl_disj_un_singleton)
532 finally show ?thesis .
534 case False with n_le_k have n_less_k: "n < k" by arith
535 with neq have "\<zero> = (\<Oplus>i \<in> {..<n} \<union> {n}. ?s i)"
536 by (simp add: R.finsum_Un_disjoint f1 f2
537 ivl_disj_int_singleton Pi_def del: Un_insert_right)
538 also have "... = (\<Oplus>i \<in> {..n}. ?s i)"
539 by (simp only: ivl_disj_un_singleton)
540 also from n_less_k neq have "... = (\<Oplus>i \<in> {..n} \<union> {n<..k}. ?s i)"
541 by (simp add: R.finsum_Un_disjoint f3 ivl_disj_int_one Pi_def)
542 also from n_less_k have "... = (\<Oplus>i \<in> {..k}. ?s i)"
543 by (simp only: ivl_disj_un_one)
544 finally show ?thesis .
548 also have "... = coeff P (monom P \<one> n \<otimes>\<^bsub>P\<^esub> monom P \<one> 1) k" by simp
549 finally show ?thesis .
553 lemma (in UP_cring) monom_mult_smult:
554 "[| a \<in> carrier R; b \<in> carrier R |] ==> monom P (a \<otimes> b) n = a \<odot>\<^bsub>P\<^esub> monom P b n"
555 by (rule up_eqI) simp_all
557 lemma (in UP_cring) monom_one [simp]:
558 "monom P \<one> 0 = \<one>\<^bsub>P\<^esub>"
559 by (rule up_eqI) simp_all
561 lemma (in UP_cring) monom_one_mult:
562 "monom P \<one> (n + m) = monom P \<one> n \<otimes>\<^bsub>P\<^esub> monom P \<one> m"
564 case 0 show ?case by simp
566 case Suc then show ?case
567 by (simp only: add_Suc monom_one_Suc) (simp add: P.m_ac)
570 lemma (in UP_cring) monom_mult [simp]:
571 assumes R: "a \<in> carrier R" "b \<in> carrier R"
572 shows "monom P (a \<otimes> b) (n + m) = monom P a n \<otimes>\<^bsub>P\<^esub> monom P b m"
574 from R have "monom P (a \<otimes> b) (n + m) = monom P (a \<otimes> b \<otimes> \<one>) (n + m)" by simp
575 also from R have "... = a \<otimes> b \<odot>\<^bsub>P\<^esub> monom P \<one> (n + m)"
576 by (simp add: monom_mult_smult del: R.r_one)
577 also have "... = a \<otimes> b \<odot>\<^bsub>P\<^esub> (monom P \<one> n \<otimes>\<^bsub>P\<^esub> monom P \<one> m)"
578 by (simp only: monom_one_mult)
579 also from R have "... = a \<odot>\<^bsub>P\<^esub> (b \<odot>\<^bsub>P\<^esub> (monom P \<one> n \<otimes>\<^bsub>P\<^esub> monom P \<one> m))"
580 by (simp add: UP_smult_assoc1)
581 also from R have "... = a \<odot>\<^bsub>P\<^esub> (b \<odot>\<^bsub>P\<^esub> (monom P \<one> m \<otimes>\<^bsub>P\<^esub> monom P \<one> n))"
582 by (simp add: P.m_comm)
583 also from R have "... = a \<odot>\<^bsub>P\<^esub> ((b \<odot>\<^bsub>P\<^esub> monom P \<one> m) \<otimes>\<^bsub>P\<^esub> monom P \<one> n)"
584 by (simp add: UP_smult_assoc2)
585 also from R have "... = a \<odot>\<^bsub>P\<^esub> (monom P \<one> n \<otimes>\<^bsub>P\<^esub> (b \<odot>\<^bsub>P\<^esub> monom P \<one> m))"
586 by (simp add: P.m_comm)
587 also from R have "... = (a \<odot>\<^bsub>P\<^esub> monom P \<one> n) \<otimes>\<^bsub>P\<^esub> (b \<odot>\<^bsub>P\<^esub> monom P \<one> m)"
588 by (simp add: UP_smult_assoc2)
589 also from R have "... = monom P (a \<otimes> \<one>) n \<otimes>\<^bsub>P\<^esub> monom P (b \<otimes> \<one>) m"
590 by (simp add: monom_mult_smult del: R.r_one)
591 also from R have "... = monom P a n \<otimes>\<^bsub>P\<^esub> monom P b m" by simp
592 finally show ?thesis .
595 lemma (in UP_cring) monom_a_inv [simp]:
596 "a \<in> carrier R ==> monom P (\<ominus> a) n = \<ominus>\<^bsub>P\<^esub> monom P a n"
597 by (rule up_eqI) simp_all
599 lemma (in UP_cring) monom_inj:
600 "inj_on (%a. monom P a n) (carrier R)"
603 assume R: "x \<in> carrier R" "y \<in> carrier R" and eq: "monom P x n = monom P y n"
604 then have "coeff P (monom P x n) n = coeff P (monom P y n) n" by simp
605 with R show "x = y" by simp
609 subsection {* The Degree Function *}
611 constdefs (structure R)
612 deg :: "[('a, 'm) ring_scheme, nat => 'a] => nat"
613 "deg R p == LEAST n. bound \<zero> n (coeff (UP R) p)"
615 lemma (in UP_cring) deg_aboveI:
616 "[| (!!m. n < m ==> coeff P p m = \<zero>); p \<in> carrier P |] ==> deg R p <= n"
617 by (unfold deg_def P_def) (fast intro: Least_le)
620 lemma coeff_bound_ex: "EX n. bound n (coeff p)"
622 have "(%n. coeff p n) : UP" by (simp add: coeff_def Rep_UP)
623 then obtain n where "bound n (coeff p)" by (unfold UP_def) fast
627 lemma bound_coeff_obtain:
628 assumes prem: "(!!n. bound n (coeff p) ==> P)" shows "P"
630 have "(%n. coeff p n) : UP" by (simp add: coeff_def Rep_UP)
631 then obtain n where "bound n (coeff p)" by (unfold UP_def) fast
636 lemma (in UP_cring) deg_aboveD:
637 assumes "deg R p < m" and "p \<in> carrier P"
638 shows "coeff P p m = \<zero>"
640 from `p \<in> carrier P` obtain n where "bound \<zero> n (coeff P p)"
641 by (auto simp add: UP_def P_def)
642 then have "bound \<zero> (deg R p) (coeff P p)"
643 by (auto simp: deg_def P_def dest: LeastI)
644 from this and `deg R p < m` show ?thesis ..
647 lemma (in UP_cring) deg_belowI:
648 assumes non_zero: "n ~= 0 ==> coeff P p n ~= \<zero>"
649 and R: "p \<in> carrier P"
651 -- {* Logically, this is a slightly stronger version of
652 @{thm [source] deg_aboveD} *}
654 case True then show ?thesis by simp
656 case False then have "coeff P p n ~= \<zero>" by (rule non_zero)
657 then have "~ deg R p < n" by (fast dest: deg_aboveD intro: R)
658 then show ?thesis by arith
661 lemma (in UP_cring) lcoeff_nonzero_deg:
662 assumes deg: "deg R p ~= 0" and R: "p \<in> carrier P"
663 shows "coeff P p (deg R p) ~= \<zero>"
665 from R obtain m where "deg R p <= m" and m_coeff: "coeff P p m ~= \<zero>"
667 have minus: "!!(n::nat) m. n ~= 0 ==> (n - Suc 0 < m) = (n <= m)"
669 (* TODO: why does simplification below not work with "1" *)
670 from deg have "deg R p - 1 < (LEAST n. bound \<zero> n (coeff P p))"
671 by (unfold deg_def P_def) arith
672 then have "~ bound \<zero> (deg R p - 1) (coeff P p)" by (rule not_less_Least)
673 then have "EX m. deg R p - 1 < m & coeff P p m ~= \<zero>"
674 by (unfold bound_def) fast
675 then have "EX m. deg R p <= m & coeff P p m ~= \<zero>" by (simp add: deg minus)
676 then show ?thesis by (auto intro: that)
678 with deg_belowI R have "deg R p = m" by fastsimp
679 with m_coeff show ?thesis by simp
682 lemma (in UP_cring) lcoeff_nonzero_nonzero:
683 assumes deg: "deg R p = 0" and nonzero: "p ~= \<zero>\<^bsub>P\<^esub>" and R: "p \<in> carrier P"
684 shows "coeff P p 0 ~= \<zero>"
686 have "EX m. coeff P p m ~= \<zero>"
687 proof (rule classical)
689 with R have "p = \<zero>\<^bsub>P\<^esub>" by (auto intro: up_eqI)
690 with nonzero show ?thesis by contradiction
692 then obtain m where coeff: "coeff P p m ~= \<zero>" ..
693 from this and R have "m <= deg R p" by (rule deg_belowI)
694 then have "m = 0" by (simp add: deg)
695 with coeff show ?thesis by simp
698 lemma (in UP_cring) lcoeff_nonzero:
699 assumes neq: "p ~= \<zero>\<^bsub>P\<^esub>" and R: "p \<in> carrier P"
700 shows "coeff P p (deg R p) ~= \<zero>"
701 proof (cases "deg R p = 0")
702 case True with neq R show ?thesis by (simp add: lcoeff_nonzero_nonzero)
704 case False with neq R show ?thesis by (simp add: lcoeff_nonzero_deg)
707 lemma (in UP_cring) deg_eqI:
708 "[| !!m. n < m ==> coeff P p m = \<zero>;
709 !!n. n ~= 0 ==> coeff P p n ~= \<zero>; p \<in> carrier P |] ==> deg R p = n"
710 by (fast intro: le_anti_sym deg_aboveI deg_belowI)
712 text {* Degree and polynomial operations *}
714 lemma (in UP_cring) deg_add [simp]:
715 assumes R: "p \<in> carrier P" "q \<in> carrier P"
716 shows "deg R (p \<oplus>\<^bsub>P\<^esub> q) <= max (deg R p) (deg R q)"
717 proof (cases "deg R p <= deg R q")
718 case True show ?thesis
719 by (rule deg_aboveI) (simp_all add: True R deg_aboveD)
721 case False show ?thesis
722 by (rule deg_aboveI) (simp_all add: False R deg_aboveD)
725 lemma (in UP_cring) deg_monom_le:
726 "a \<in> carrier R ==> deg R (monom P a n) <= n"
727 by (intro deg_aboveI) simp_all
729 lemma (in UP_cring) deg_monom [simp]:
730 "[| a ~= \<zero>; a \<in> carrier R |] ==> deg R (monom P a n) = n"
731 by (fastsimp intro: le_anti_sym deg_aboveI deg_belowI)
733 lemma (in UP_cring) deg_const [simp]:
734 assumes R: "a \<in> carrier R" shows "deg R (monom P a 0) = 0"
735 proof (rule le_anti_sym)
736 show "deg R (monom P a 0) <= 0" by (rule deg_aboveI) (simp_all add: R)
738 show "0 <= deg R (monom P a 0)" by (rule deg_belowI) (simp_all add: R)
741 lemma (in UP_cring) deg_zero [simp]:
742 "deg R \<zero>\<^bsub>P\<^esub> = 0"
743 proof (rule le_anti_sym)
744 show "deg R \<zero>\<^bsub>P\<^esub> <= 0" by (rule deg_aboveI) simp_all
746 show "0 <= deg R \<zero>\<^bsub>P\<^esub>" by (rule deg_belowI) simp_all
749 lemma (in UP_cring) deg_one [simp]:
750 "deg R \<one>\<^bsub>P\<^esub> = 0"
751 proof (rule le_anti_sym)
752 show "deg R \<one>\<^bsub>P\<^esub> <= 0" by (rule deg_aboveI) simp_all
754 show "0 <= deg R \<one>\<^bsub>P\<^esub>" by (rule deg_belowI) simp_all
757 lemma (in UP_cring) deg_uminus [simp]:
758 assumes R: "p \<in> carrier P" shows "deg R (\<ominus>\<^bsub>P\<^esub> p) = deg R p"
759 proof (rule le_anti_sym)
760 show "deg R (\<ominus>\<^bsub>P\<^esub> p) <= deg R p" by (simp add: deg_aboveI deg_aboveD R)
762 show "deg R p <= deg R (\<ominus>\<^bsub>P\<^esub> p)"
763 by (simp add: deg_belowI lcoeff_nonzero_deg
764 inj_on_iff [OF R.a_inv_inj, of _ "\<zero>", simplified] R)
767 lemma (in UP_domain) deg_smult_ring:
768 "[| a \<in> carrier R; p \<in> carrier P |] ==>
769 deg R (a \<odot>\<^bsub>P\<^esub> p) <= (if a = \<zero> then 0 else deg R p)"
770 by (cases "a = \<zero>") (simp add: deg_aboveI deg_aboveD)+
772 lemma (in UP_domain) deg_smult [simp]:
773 assumes R: "a \<in> carrier R" "p \<in> carrier P"
774 shows "deg R (a \<odot>\<^bsub>P\<^esub> p) = (if a = \<zero> then 0 else deg R p)"
775 proof (rule le_anti_sym)
776 show "deg R (a \<odot>\<^bsub>P\<^esub> p) <= (if a = \<zero> then 0 else deg R p)"
777 using R by (rule deg_smult_ring)
779 show "(if a = \<zero> then 0 else deg R p) <= deg R (a \<odot>\<^bsub>P\<^esub> p)"
780 proof (cases "a = \<zero>")
781 qed (simp, simp add: deg_belowI lcoeff_nonzero_deg integral_iff R)
784 lemma (in UP_cring) deg_mult_cring:
785 assumes R: "p \<in> carrier P" "q \<in> carrier P"
786 shows "deg R (p \<otimes>\<^bsub>P\<^esub> q) <= deg R p + deg R q"
787 proof (rule deg_aboveI)
789 assume boundm: "deg R p + deg R q < m"
792 assume boundk: "deg R p + deg R q < k"
793 then have "coeff P p i \<otimes> coeff P q (k - i) = \<zero>"
794 proof (cases "deg R p < i")
795 case True then show ?thesis by (simp add: deg_aboveD R)
797 case False with boundk have "deg R q < k - i" by arith
798 then show ?thesis by (simp add: deg_aboveD R)
801 with boundm R show "coeff P (p \<otimes>\<^bsub>P\<^esub> q) m = \<zero>" by simp
804 lemma (in UP_domain) deg_mult [simp]:
805 "[| p ~= \<zero>\<^bsub>P\<^esub>; q ~= \<zero>\<^bsub>P\<^esub>; p \<in> carrier P; q \<in> carrier P |] ==>
806 deg R (p \<otimes>\<^bsub>P\<^esub> q) = deg R p + deg R q"
807 proof (rule le_anti_sym)
808 assume "p \<in> carrier P" " q \<in> carrier P"
809 then show "deg R (p \<otimes>\<^bsub>P\<^esub> q) <= deg R p + deg R q" by (rule deg_mult_cring)
811 let ?s = "(%i. coeff P p i \<otimes> coeff P q (deg R p + deg R q - i))"
812 assume R: "p \<in> carrier P" "q \<in> carrier P" and nz: "p ~= \<zero>\<^bsub>P\<^esub>" "q ~= \<zero>\<^bsub>P\<^esub>"
813 have less_add_diff: "!!(k::nat) n m. k < n ==> m < n + m - k" by arith
814 show "deg R p + deg R q <= deg R (p \<otimes>\<^bsub>P\<^esub> q)"
815 proof (rule deg_belowI, simp add: R)
816 have "(\<Oplus>i \<in> {.. deg R p + deg R q}. ?s i)
817 = (\<Oplus>i \<in> {..< deg R p} \<union> {deg R p .. deg R p + deg R q}. ?s i)"
818 by (simp only: ivl_disj_un_one)
819 also have "... = (\<Oplus>i \<in> {deg R p .. deg R p + deg R q}. ?s i)"
820 by (simp cong: R.finsum_cong add: R.finsum_Un_disjoint ivl_disj_int_one
821 deg_aboveD less_add_diff R Pi_def)
822 also have "...= (\<Oplus>i \<in> {deg R p} \<union> {deg R p <.. deg R p + deg R q}. ?s i)"
823 by (simp only: ivl_disj_un_singleton)
824 also have "... = coeff P p (deg R p) \<otimes> coeff P q (deg R q)"
825 by (simp cong: R.finsum_cong
826 add: ivl_disj_int_singleton deg_aboveD R Pi_def)
827 finally have "(\<Oplus>i \<in> {.. deg R p + deg R q}. ?s i)
828 = coeff P p (deg R p) \<otimes> coeff P q (deg R q)" .
829 with nz show "(\<Oplus>i \<in> {.. deg R p + deg R q}. ?s i) ~= \<zero>"
830 by (simp add: integral_iff lcoeff_nonzero R)
834 lemma (in UP_cring) coeff_finsum:
835 assumes fin: "finite A"
836 shows "p \<in> A -> carrier P ==>
837 coeff P (finsum P p A) k = (\<Oplus>i \<in> A. coeff P (p i) k)"
838 using fin by induct (auto simp: Pi_def)
840 lemma (in UP_cring) up_repr:
841 assumes R: "p \<in> carrier P"
842 shows "(\<Oplus>\<^bsub>P\<^esub> i \<in> {..deg R p}. monom P (coeff P p i) i) = p"
844 let ?s = "(%i. monom P (coeff P p i) i)"
846 from R have RR: "!!i. (if i = k then coeff P p i else \<zero>) \<in> carrier R"
848 show "coeff P (\<Oplus>\<^bsub>P\<^esub> i \<in> {..deg R p}. ?s i) k = coeff P p k"
849 proof (cases "k <= deg R p")
851 hence "coeff P (\<Oplus>\<^bsub>P\<^esub> i \<in> {..deg R p}. ?s i) k =
852 coeff P (\<Oplus>\<^bsub>P\<^esub> i \<in> {..k} \<union> {k<..deg R p}. ?s i) k"
853 by (simp only: ivl_disj_un_one)
855 have "... = coeff P (\<Oplus>\<^bsub>P\<^esub> i \<in> {..k}. ?s i) k"
856 by (simp cong: R.finsum_cong add: R.finsum_Un_disjoint
857 ivl_disj_int_one order_less_imp_not_eq2 coeff_finsum R RR Pi_def)
859 have "... = coeff P (\<Oplus>\<^bsub>P\<^esub> i \<in> {..<k} \<union> {k}. ?s i) k"
860 by (simp only: ivl_disj_un_singleton)
861 also have "... = coeff P p k"
862 by (simp cong: R.finsum_cong
863 add: ivl_disj_int_singleton coeff_finsum deg_aboveD R RR Pi_def)
864 finally show ?thesis .
867 hence "coeff P (\<Oplus>\<^bsub>P\<^esub> i \<in> {..deg R p}. ?s i) k =
868 coeff P (\<Oplus>\<^bsub>P\<^esub> i \<in> {..<deg R p} \<union> {deg R p}. ?s i) k"
869 by (simp only: ivl_disj_un_singleton)
870 also from False have "... = coeff P p k"
871 by (simp cong: R.finsum_cong
872 add: ivl_disj_int_singleton coeff_finsum deg_aboveD R Pi_def)
873 finally show ?thesis .
875 qed (simp_all add: R Pi_def)
877 lemma (in UP_cring) up_repr_le:
878 "[| deg R p <= n; p \<in> carrier P |] ==>
879 (\<Oplus>\<^bsub>P\<^esub> i \<in> {..n}. monom P (coeff P p i) i) = p"
881 let ?s = "(%i. monom P (coeff P p i) i)"
882 assume R: "p \<in> carrier P" and "deg R p <= n"
883 then have "finsum P ?s {..n} = finsum P ?s ({..deg R p} \<union> {deg R p<..n})"
884 by (simp only: ivl_disj_un_one)
885 also have "... = finsum P ?s {..deg R p}"
886 by (simp cong: P.finsum_cong add: P.finsum_Un_disjoint ivl_disj_int_one
888 also have "... = p" using R by (rule up_repr)
889 finally show ?thesis .
893 subsection {* Polynomials over Integral Domains *}
896 assumes cring: "cring R"
897 and one_not_zero: "one R ~= zero R"
898 and integral: "!!a b. [| mult R a b = zero R; a \<in> carrier R;
899 b \<in> carrier R |] ==> a = zero R | b = zero R"
901 by (auto intro!: domain.intro domain_axioms.intro cring.axioms assms
904 lemma (in UP_domain) UP_one_not_zero:
905 "\<one>\<^bsub>P\<^esub> ~= \<zero>\<^bsub>P\<^esub>"
907 assume "\<one>\<^bsub>P\<^esub> = \<zero>\<^bsub>P\<^esub>"
908 hence "coeff P \<one>\<^bsub>P\<^esub> 0 = (coeff P \<zero>\<^bsub>P\<^esub> 0)" by simp
909 hence "\<one> = \<zero>" by simp
910 with one_not_zero show "False" by contradiction
913 lemma (in UP_domain) UP_integral:
914 "[| p \<otimes>\<^bsub>P\<^esub> q = \<zero>\<^bsub>P\<^esub>; p \<in> carrier P; q \<in> carrier P |] ==> p = \<zero>\<^bsub>P\<^esub> | q = \<zero>\<^bsub>P\<^esub>"
917 assume pq: "p \<otimes>\<^bsub>P\<^esub> q = \<zero>\<^bsub>P\<^esub>" and R: "p \<in> carrier P" "q \<in> carrier P"
918 show "p = \<zero>\<^bsub>P\<^esub> | q = \<zero>\<^bsub>P\<^esub>"
919 proof (rule classical)
920 assume c: "~ (p = \<zero>\<^bsub>P\<^esub> | q = \<zero>\<^bsub>P\<^esub>)"
921 with R have "deg R p + deg R q = deg R (p \<otimes>\<^bsub>P\<^esub> q)" by simp
922 also from pq have "... = 0" by simp
923 finally have "deg R p + deg R q = 0" .
924 then have f1: "deg R p = 0 & deg R q = 0" by simp
925 from f1 R have "p = (\<Oplus>\<^bsub>P\<^esub> i \<in> {..0}. monom P (coeff P p i) i)"
926 by (simp only: up_repr_le)
927 also from R have "... = monom P (coeff P p 0) 0" by simp
928 finally have p: "p = monom P (coeff P p 0) 0" .
929 from f1 R have "q = (\<Oplus>\<^bsub>P\<^esub> i \<in> {..0}. monom P (coeff P q i) i)"
930 by (simp only: up_repr_le)
931 also from R have "... = monom P (coeff P q 0) 0" by simp
932 finally have q: "q = monom P (coeff P q 0) 0" .
933 from R have "coeff P p 0 \<otimes> coeff P q 0 = coeff P (p \<otimes>\<^bsub>P\<^esub> q) 0" by simp
934 also from pq have "... = \<zero>" by simp
935 finally have "coeff P p 0 \<otimes> coeff P q 0 = \<zero>" .
936 with R have "coeff P p 0 = \<zero> | coeff P q 0 = \<zero>"
937 by (simp add: R.integral_iff)
938 with p q show "p = \<zero>\<^bsub>P\<^esub> | q = \<zero>\<^bsub>P\<^esub>" by fastsimp
942 theorem (in UP_domain) UP_domain:
944 by (auto intro!: domainI UP_cring UP_one_not_zero UP_integral del: disjCI)
947 Interpretation of theorems from @{term domain}.
950 interpretation UP_domain < "domain" P
951 by intro_locales (rule domain.axioms UP_domain)+
954 subsection {* The Evaluation Homomorphism and Universal Property*}
956 (* alternative congruence rule (possibly more efficient)
957 lemma (in abelian_monoid) finsum_cong2:
958 "[| !!i. i \<in> A ==> f i \<in> carrier G = True; A = B;
959 !!i. i \<in> B ==> f i = g i |] ==> finsum G f A = finsum G g B"
962 theorem (in cring) diagonal_sum:
963 "[| f \<in> {..n + m::nat} -> carrier R; g \<in> {..n + m} -> carrier R |] ==>
964 (\<Oplus>k \<in> {..n + m}. \<Oplus>i \<in> {..k}. f i \<otimes> g (k - i)) =
965 (\<Oplus>k \<in> {..n + m}. \<Oplus>i \<in> {..n + m - k}. f k \<otimes> g i)"
967 assume Rf: "f \<in> {..n + m} -> carrier R" and Rg: "g \<in> {..n + m} -> carrier R"
971 (\<Oplus>k \<in> {..j}. \<Oplus>i \<in> {..k}. f i \<otimes> g (k - i)) =
972 (\<Oplus>k \<in> {..j}. \<Oplus>i \<in> {..j - k}. f k \<otimes> g i)"
974 case 0 from Rf Rg show ?case by (simp add: Pi_def)
977 have R6: "!!i k. [| k <= j; i <= Suc j - k |] ==> g i \<in> carrier R"
978 using Suc by (auto intro!: funcset_mem [OF Rg])
979 have R8: "!!i k. [| k <= Suc j; i <= k |] ==> g (k - i) \<in> carrier R"
980 using Suc by (auto intro!: funcset_mem [OF Rg])
981 have R9: "!!i k. [| k <= Suc j |] ==> f k \<in> carrier R"
982 using Suc by (auto intro!: funcset_mem [OF Rf])
983 have R10: "!!i k. [| k <= Suc j; i <= Suc j - k |] ==> g i \<in> carrier R"
984 using Suc by (auto intro!: funcset_mem [OF Rg])
985 have R11: "g 0 \<in> carrier R"
986 using Suc by (auto intro!: funcset_mem [OF Rg])
988 by (simp cong: finsum_cong add: Suc_diff_le a_ac
989 Pi_def R6 R8 R9 R10 R11)
992 then show ?thesis by fast
995 lemma (in abelian_monoid) boundD_carrier:
996 "[| bound \<zero> n f; n < m |] ==> f m \<in> carrier G"
999 theorem (in cring) cauchy_product:
1000 assumes bf: "bound \<zero> n f" and bg: "bound \<zero> m g"
1001 and Rf: "f \<in> {..n} -> carrier R" and Rg: "g \<in> {..m} -> carrier R"
1002 shows "(\<Oplus>k \<in> {..n + m}. \<Oplus>i \<in> {..k}. f i \<otimes> g (k - i)) =
1003 (\<Oplus>i \<in> {..n}. f i) \<otimes> (\<Oplus>i \<in> {..m}. g i)" (* State reverse direction? *)
1005 have f: "!!x. f x \<in> carrier R"
1008 show "f x \<in> carrier R"
1009 using Rf bf boundD_carrier by (cases "x <= n") (auto simp: Pi_def)
1011 have g: "!!x. g x \<in> carrier R"
1014 show "g x \<in> carrier R"
1015 using Rg bg boundD_carrier by (cases "x <= m") (auto simp: Pi_def)
1017 from f g have "(\<Oplus>k \<in> {..n + m}. \<Oplus>i \<in> {..k}. f i \<otimes> g (k - i)) =
1018 (\<Oplus>k \<in> {..n + m}. \<Oplus>i \<in> {..n + m - k}. f k \<otimes> g i)"
1019 by (simp add: diagonal_sum Pi_def)
1020 also have "... = (\<Oplus>k \<in> {..n} \<union> {n<..n + m}. \<Oplus>i \<in> {..n + m - k}. f k \<otimes> g i)"
1021 by (simp only: ivl_disj_un_one)
1022 also from f g have "... = (\<Oplus>k \<in> {..n}. \<Oplus>i \<in> {..n + m - k}. f k \<otimes> g i)"
1023 by (simp cong: finsum_cong
1024 add: bound.bound [OF bf] finsum_Un_disjoint ivl_disj_int_one Pi_def)
1026 have "... = (\<Oplus>k \<in> {..n}. \<Oplus>i \<in> {..m} \<union> {m<..n + m - k}. f k \<otimes> g i)"
1027 by (simp cong: finsum_cong add: ivl_disj_un_one le_add_diff Pi_def)
1028 also from f g have "... = (\<Oplus>k \<in> {..n}. \<Oplus>i \<in> {..m}. f k \<otimes> g i)"
1029 by (simp cong: finsum_cong
1030 add: bound.bound [OF bg] finsum_Un_disjoint ivl_disj_int_one Pi_def)
1031 also from f g have "... = (\<Oplus>i \<in> {..n}. f i) \<otimes> (\<Oplus>i \<in> {..m}. g i)"
1032 by (simp add: finsum_ldistr diagonal_sum Pi_def,
1033 simp cong: finsum_cong add: finsum_rdistr Pi_def)
1034 finally show ?thesis .
1037 lemma (in UP_cring) const_ring_hom:
1038 "(%a. monom P a 0) \<in> ring_hom R P"
1039 by (auto intro!: ring_hom_memI intro: up_eqI simp: monom_mult_is_smult)
1041 constdefs (structure S)
1042 eval :: "[('a, 'm) ring_scheme, ('b, 'n) ring_scheme,
1043 'a => 'b, 'b, nat => 'a] => 'b"
1044 "eval R S phi s == \<lambda>p \<in> carrier (UP R).
1045 \<Oplus>i \<in> {..deg R p}. phi (coeff (UP R) p i) \<otimes> s (^) i"
1048 lemma (in UP) eval_on_carrier:
1050 shows "p \<in> carrier P ==>
1051 eval R S phi s p = (\<Oplus>\<^bsub>S\<^esub> i \<in> {..deg R p}. phi (coeff P p i) \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> i)"
1052 by (unfold eval_def, fold P_def) simp
1054 lemma (in UP) eval_extensional:
1055 "eval R S phi p \<in> extensional (carrier P)"
1056 by (unfold eval_def, fold P_def) simp
1059 text {* The universal property of the polynomial ring *}
1061 locale UP_pre_univ_prop = ring_hom_cring R S h + UP_cring R P
1063 locale UP_univ_prop = UP_pre_univ_prop +
1065 assumes indet_img_carrier [simp, intro]: "s \<in> carrier S"
1066 defines Eval_def: "Eval == eval R S h s"
1068 theorem (in UP_pre_univ_prop) eval_ring_hom:
1069 assumes S: "s \<in> carrier S"
1070 shows "eval R S h s \<in> ring_hom P S"
1071 proof (rule ring_hom_memI)
1073 assume R: "p \<in> carrier P"
1074 then show "eval R S h s p \<in> carrier S"
1075 by (simp only: eval_on_carrier) (simp add: S Pi_def)
1078 assume R: "p \<in> carrier P" "q \<in> carrier P"
1079 then show "eval R S h s (p \<otimes>\<^bsub>P\<^esub> q) = eval R S h s p \<otimes>\<^bsub>S\<^esub> eval R S h s q"
1080 proof (simp only: eval_on_carrier UP_mult_closed)
1082 "(\<Oplus>\<^bsub>S\<^esub> i \<in> {..deg R (p \<otimes>\<^bsub>P\<^esub> q)}. h (coeff P (p \<otimes>\<^bsub>P\<^esub> q) i) \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> i) =
1083 (\<Oplus>\<^bsub>S\<^esub> i \<in> {..deg R (p \<otimes>\<^bsub>P\<^esub> q)} \<union> {deg R (p \<otimes>\<^bsub>P\<^esub> q)<..deg R p + deg R q}.
1084 h (coeff P (p \<otimes>\<^bsub>P\<^esub> q) i) \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> i)"
1085 by (simp cong: S.finsum_cong
1086 add: deg_aboveD S.finsum_Un_disjoint ivl_disj_int_one Pi_def
1088 also from R have "... =
1089 (\<Oplus>\<^bsub>S\<^esub> i \<in> {..deg R p + deg R q}. h (coeff P (p \<otimes>\<^bsub>P\<^esub> q) i) \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> i)"
1090 by (simp only: ivl_disj_un_one deg_mult_cring)
1091 also from R S have "... =
1092 (\<Oplus>\<^bsub>S\<^esub> i \<in> {..deg R p + deg R q}.
1093 \<Oplus>\<^bsub>S\<^esub> k \<in> {..i}.
1094 h (coeff P p k) \<otimes>\<^bsub>S\<^esub> h (coeff P q (i - k)) \<otimes>\<^bsub>S\<^esub>
1095 (s (^)\<^bsub>S\<^esub> k \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> (i - k)))"
1096 by (simp cong: S.finsum_cong add: S.nat_pow_mult Pi_def
1097 S.m_ac S.finsum_rdistr)
1098 also from R S have "... =
1099 (\<Oplus>\<^bsub>S\<^esub> i\<in>{..deg R p}. h (coeff P p i) \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> i) \<otimes>\<^bsub>S\<^esub>
1100 (\<Oplus>\<^bsub>S\<^esub> i\<in>{..deg R q}. h (coeff P q i) \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> i)"
1101 by (simp add: S.cauchy_product [THEN sym] bound.intro deg_aboveD S.m_ac
1104 "(\<Oplus>\<^bsub>S\<^esub> i \<in> {..deg R (p \<otimes>\<^bsub>P\<^esub> q)}. h (coeff P (p \<otimes>\<^bsub>P\<^esub> q) i) \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> i) =
1105 (\<Oplus>\<^bsub>S\<^esub> i \<in> {..deg R p}. h (coeff P p i) \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> i) \<otimes>\<^bsub>S\<^esub>
1106 (\<Oplus>\<^bsub>S\<^esub> i \<in> {..deg R q}. h (coeff P q i) \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> i)" .
1110 assume R: "p \<in> carrier P" "q \<in> carrier P"
1111 then show "eval R S h s (p \<oplus>\<^bsub>P\<^esub> q) = eval R S h s p \<oplus>\<^bsub>S\<^esub> eval R S h s q"
1112 proof (simp only: eval_on_carrier P.a_closed)
1114 "(\<Oplus>\<^bsub>S \<^esub>i\<in>{..deg R (p \<oplus>\<^bsub>P\<^esub> q)}. h (coeff P (p \<oplus>\<^bsub>P\<^esub> q) i) \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> i) =
1115 (\<Oplus>\<^bsub>S \<^esub>i\<in>{..deg R (p \<oplus>\<^bsub>P\<^esub> q)} \<union> {deg R (p \<oplus>\<^bsub>P\<^esub> q)<..max (deg R p) (deg R q)}.
1116 h (coeff P (p \<oplus>\<^bsub>P\<^esub> q) i) \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> i)"
1117 by (simp cong: S.finsum_cong
1118 add: deg_aboveD S.finsum_Un_disjoint ivl_disj_int_one Pi_def
1120 also from R have "... =
1121 (\<Oplus>\<^bsub>S\<^esub> i \<in> {..max (deg R p) (deg R q)}.
1122 h (coeff P (p \<oplus>\<^bsub>P\<^esub> q) i) \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> i)"
1123 by (simp add: ivl_disj_un_one)
1124 also from R S have "... =
1125 (\<Oplus>\<^bsub>S\<^esub>i\<in>{..max (deg R p) (deg R q)}. h (coeff P p i) \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> i) \<oplus>\<^bsub>S\<^esub>
1126 (\<Oplus>\<^bsub>S\<^esub>i\<in>{..max (deg R p) (deg R q)}. h (coeff P q i) \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> i)"
1127 by (simp cong: S.finsum_cong
1128 add: S.l_distr deg_aboveD ivl_disj_int_one Pi_def)
1130 (\<Oplus>\<^bsub>S\<^esub> i \<in> {..deg R p} \<union> {deg R p<..max (deg R p) (deg R q)}.
1131 h (coeff P p i) \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> i) \<oplus>\<^bsub>S\<^esub>
1132 (\<Oplus>\<^bsub>S\<^esub> i \<in> {..deg R q} \<union> {deg R q<..max (deg R p) (deg R q)}.
1133 h (coeff P q i) \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> i)"
1134 by (simp only: ivl_disj_un_one le_maxI1 le_maxI2)
1135 also from R S have "... =
1136 (\<Oplus>\<^bsub>S\<^esub> i \<in> {..deg R p}. h (coeff P p i) \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> i) \<oplus>\<^bsub>S\<^esub>
1137 (\<Oplus>\<^bsub>S\<^esub> i \<in> {..deg R q}. h (coeff P q i) \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> i)"
1138 by (simp cong: S.finsum_cong
1139 add: deg_aboveD S.finsum_Un_disjoint ivl_disj_int_one Pi_def)
1141 "(\<Oplus>\<^bsub>S\<^esub>i \<in> {..deg R (p \<oplus>\<^bsub>P\<^esub> q)}. h (coeff P (p \<oplus>\<^bsub>P\<^esub> q) i) \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> i) =
1142 (\<Oplus>\<^bsub>S\<^esub>i \<in> {..deg R p}. h (coeff P p i) \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> i) \<oplus>\<^bsub>S\<^esub>
1143 (\<Oplus>\<^bsub>S\<^esub>i \<in> {..deg R q}. h (coeff P q i) \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> i)" .
1146 show "eval R S h s \<one>\<^bsub>P\<^esub> = \<one>\<^bsub>S\<^esub>"
1147 by (simp only: eval_on_carrier UP_one_closed) simp
1150 text {* Interpretation of ring homomorphism lemmas. *}
1152 interpretation UP_univ_prop < ring_hom_cring P S Eval
1153 apply (unfold Eval_def)
1155 apply (rule ring_hom_cring.axioms)
1156 apply (rule ring_hom_cring.intro)
1157 apply unfold_locales
1158 apply (rule eval_ring_hom)
1163 text {* Further properties of the evaluation homomorphism. *}
1166 The following lemma could be proved in @{text UP_cring} with the additional
1167 assumption that @{text h} is closed. *}
1169 lemma (in UP_pre_univ_prop) eval_const:
1170 "[| s \<in> carrier S; r \<in> carrier R |] ==> eval R S h s (monom P r 0) = h r"
1171 by (simp only: eval_on_carrier monom_closed) simp
1173 text {* The following proof is complicated by the fact that in arbitrary
1174 rings one might have @{term "one R = zero R"}. *}
1176 (* TODO: simplify by cases "one R = zero R" *)
1178 lemma (in UP_pre_univ_prop) eval_monom1:
1179 assumes S: "s \<in> carrier S"
1180 shows "eval R S h s (monom P \<one> 1) = s"
1181 proof (simp only: eval_on_carrier monom_closed R.one_closed)
1183 "(\<Oplus>\<^bsub>S\<^esub> i\<in>{..deg R (monom P \<one> 1)}. h (coeff P (monom P \<one> 1) i) \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> i) =
1184 (\<Oplus>\<^bsub>S\<^esub> i\<in>{..deg R (monom P \<one> 1)} \<union> {deg R (monom P \<one> 1)<..1}.
1185 h (coeff P (monom P \<one> 1) i) \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> i)"
1186 by (simp cong: S.finsum_cong del: coeff_monom
1187 add: deg_aboveD S.finsum_Un_disjoint ivl_disj_int_one Pi_def)
1189 (\<Oplus>\<^bsub>S\<^esub> i \<in> {..1}. h (coeff P (monom P \<one> 1) i) \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> i)"
1190 by (simp only: ivl_disj_un_one deg_monom_le R.one_closed)
1192 proof (cases "s = \<zero>\<^bsub>S\<^esub>")
1193 case True then show ?thesis by (simp add: Pi_def)
1195 case False then show ?thesis by (simp add: S Pi_def)
1197 finally show "(\<Oplus>\<^bsub>S\<^esub> i \<in> {..deg R (monom P \<one> 1)}.
1198 h (coeff P (monom P \<one> 1) i) \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> i) = s" .
1201 lemma (in UP_cring) monom_pow:
1202 assumes R: "a \<in> carrier R"
1203 shows "(monom P a n) (^)\<^bsub>P\<^esub> m = monom P (a (^) m) (n * m)"
1205 case 0 from R show ?case by simp
1207 case Suc with R show ?case
1208 by (simp del: monom_mult add: monom_mult [THEN sym] add_commute)
1211 lemma (in ring_hom_cring) hom_pow [simp]:
1212 "x \<in> carrier R ==> h (x (^) n) = h x (^)\<^bsub>S\<^esub> (n::nat)"
1213 by (induct n) simp_all
1215 lemma (in UP_univ_prop) Eval_monom:
1216 "r \<in> carrier R ==> Eval (monom P r n) = h r \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> n"
1218 assume R: "r \<in> carrier R"
1219 from R have "Eval (monom P r n) = Eval (monom P r 0 \<otimes>\<^bsub>P\<^esub> (monom P \<one> 1) (^)\<^bsub>P\<^esub> n)"
1220 by (simp del: monom_mult add: monom_mult [THEN sym] monom_pow)
1222 from R eval_monom1 [where s = s, folded Eval_def]
1223 have "... = h r \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> n"
1224 by (simp add: eval_const [where s = s, folded Eval_def])
1225 finally show ?thesis .
1228 lemma (in UP_pre_univ_prop) eval_monom:
1229 assumes R: "r \<in> carrier R" and S: "s \<in> carrier S"
1230 shows "eval R S h s (monom P r n) = h r \<otimes>\<^bsub>S\<^esub> s (^)\<^bsub>S\<^esub> n"
1232 interpret UP_univ_prop [R S h P s _]
1233 using UP_pre_univ_prop_axioms P_def R S
1234 by (auto intro: UP_univ_prop.intro UP_univ_prop_axioms.intro)
1236 show ?thesis by (rule Eval_monom)
1239 lemma (in UP_univ_prop) Eval_smult:
1240 "[| r \<in> carrier R; p \<in> carrier P |] ==> Eval (r \<odot>\<^bsub>P\<^esub> p) = h r \<otimes>\<^bsub>S\<^esub> Eval p"
1242 assume R: "r \<in> carrier R" and P: "p \<in> carrier P"
1244 by (simp add: monom_mult_is_smult [THEN sym]
1245 eval_const [where s = s, folded Eval_def])
1248 lemma ring_hom_cringI:
1251 and "h \<in> ring_hom R S"
1252 shows "ring_hom_cring R S h"
1253 by (fast intro: ring_hom_cring.intro ring_hom_cring_axioms.intro
1256 lemma (in UP_pre_univ_prop) UP_hom_unique:
1257 assumes "ring_hom_cring P S Phi"
1258 assumes Phi: "Phi (monom P \<one> (Suc 0)) = s"
1259 "!!r. r \<in> carrier R ==> Phi (monom P r 0) = h r"
1260 assumes "ring_hom_cring P S Psi"
1261 assumes Psi: "Psi (monom P \<one> (Suc 0)) = s"
1262 "!!r. r \<in> carrier R ==> Psi (monom P r 0) = h r"
1263 and P: "p \<in> carrier P" and S: "s \<in> carrier S"
1264 shows "Phi p = Psi p"
1266 interpret ring_hom_cring [P S Phi] by fact
1267 interpret ring_hom_cring [P S Psi] by fact
1269 Phi (\<Oplus>\<^bsub>P \<^esub>i \<in> {..deg R p}. monom P (coeff P p i) 0 \<otimes>\<^bsub>P\<^esub> monom P \<one> 1 (^)\<^bsub>P\<^esub> i)"
1270 by (simp add: up_repr P monom_mult [THEN sym] monom_pow del: monom_mult)
1273 Psi (\<Oplus>\<^bsub>P \<^esub>i\<in>{..deg R p}. monom P (coeff P p i) 0 \<otimes>\<^bsub>P\<^esub> monom P \<one> 1 (^)\<^bsub>P\<^esub> i)"
1274 by (simp add: Phi Psi P Pi_def comp_def)
1275 also have "... = Psi p"
1276 by (simp add: up_repr P monom_mult [THEN sym] monom_pow del: monom_mult)
1277 finally show ?thesis .
1280 lemma (in UP_pre_univ_prop) ring_homD:
1281 assumes Phi: "Phi \<in> ring_hom P S"
1282 shows "ring_hom_cring P S Phi"
1283 proof (rule ring_hom_cring.intro)
1284 show "ring_hom_cring_axioms P S Phi"
1285 by (rule ring_hom_cring_axioms.intro) (rule Phi)
1288 theorem (in UP_pre_univ_prop) UP_universal_property:
1289 assumes S: "s \<in> carrier S"
1290 shows "EX! Phi. Phi \<in> ring_hom P S \<inter> extensional (carrier P) &
1291 Phi (monom P \<one> 1) = s &
1292 (ALL r : carrier R. Phi (monom P r 0) = h r)"
1294 apply (auto intro: eval_ring_hom eval_const eval_extensional)
1295 apply (rule extensionalityI)
1296 apply (auto intro: UP_hom_unique ring_homD)
1300 subsection {* Sample Application of Evaluation Homomorphism *}
1302 lemma UP_pre_univ_propI:
1305 and "h \<in> ring_hom R S"
1306 shows "UP_pre_univ_prop R S h"
1308 by (auto intro!: UP_pre_univ_prop.intro ring_hom_cring.intro
1309 ring_hom_cring_axioms.intro UP_cring.intro)
1313 "INTEG == (| carrier = UNIV, mult = op *, one = 1, zero = 0, add = op + |)"
1317 by (unfold INTEG_def) (auto intro!: cringI abelian_groupI comm_monoidI
1318 zadd_zminus_inverse2 zadd_zmult_distrib)
1320 lemma INTEG_id_eval:
1321 "UP_pre_univ_prop INTEG INTEG id"
1322 by (fast intro: UP_pre_univ_propI INTEG_cring id_ring_hom)
1325 Interpretation now enables to import all theorems and lemmas
1326 valid in the context of homomorphisms between @{term INTEG} and @{term
1327 "UP INTEG"} globally.
1330 interpretation INTEG: UP_pre_univ_prop [INTEG INTEG id]
1336 lemma INTEG_closed [intro, simp]:
1337 "z \<in> carrier INTEG"
1338 by (unfold INTEG_def) simp
1340 lemma INTEG_mult [simp]:
1341 "mult INTEG z w = z * w"
1342 by (unfold INTEG_def) simp
1344 lemma INTEG_pow [simp]:
1345 "pow INTEG z n = z ^ n"
1346 by (induct n) (simp_all add: INTEG_def nat_pow_def)
1348 lemma "eval INTEG INTEG id 10 (monom (UP INTEG) 5 2) = 500"
1349 by (simp add: INTEG.eval_monom)