imports Rat_Pair Polynomial_List

(* Title: HOL/Decision_Procs/Reflected_Multivariate_Polynomial.thy Author: Amine Chaieb *) section ‹Implementation and verification of multivariate polynomials› theory Reflected_Multivariate_Polynomial imports Complex_Main Rat_Pair Polynomial_List begin subsection ‹Datatype of polynomial expressions› datatype poly = C Num | Bound nat | Add poly poly | Sub poly poly | Mul poly poly| Neg poly| Pw poly nat| CN poly nat poly abbreviation poly_0 :: "poly" ("0⇩_{p}") where "0⇩_{p}≡ C (0⇩_{N})" abbreviation poly_p :: "int ⇒ poly" ("'((_)')⇩_{p}") where "(i)⇩_{p}≡ C (i)⇩_{N}" subsection‹Boundedness, substitution and all that› primrec polysize:: "poly ⇒ nat" where "polysize (C c) = 1" | "polysize (Bound n) = 1" | "polysize (Neg p) = 1 + polysize p" | "polysize (Add p q) = 1 + polysize p + polysize q" | "polysize (Sub p q) = 1 + polysize p + polysize q" | "polysize (Mul p q) = 1 + polysize p + polysize q" | "polysize (Pw p n) = 1 + polysize p" | "polysize (CN c n p) = 4 + polysize c + polysize p" primrec polybound0:: "poly ⇒ bool" ― ‹a poly is INDEPENDENT of Bound 0› where "polybound0 (C c) ⟷ True" | "polybound0 (Bound n) ⟷ n > 0" | "polybound0 (Neg a) ⟷ polybound0 a" | "polybound0 (Add a b) ⟷ polybound0 a ∧ polybound0 b" | "polybound0 (Sub a b) ⟷ polybound0 a ∧ polybound0 b" | "polybound0 (Mul a b) ⟷ polybound0 a ∧ polybound0 b" | "polybound0 (Pw p n) ⟷ polybound0 p" | "polybound0 (CN c n p) ⟷ n ≠ 0 ∧ polybound0 c ∧ polybound0 p" primrec polysubst0:: "poly ⇒ poly ⇒ poly" ― ‹substitute a poly into a poly for Bound 0› where "polysubst0 t (C c) = C c" | "polysubst0 t (Bound n) = (if n = 0 then t else Bound n)" | "polysubst0 t (Neg a) = Neg (polysubst0 t a)" | "polysubst0 t (Add a b) = Add (polysubst0 t a) (polysubst0 t b)" | "polysubst0 t (Sub a b) = Sub (polysubst0 t a) (polysubst0 t b)" | "polysubst0 t (Mul a b) = Mul (polysubst0 t a) (polysubst0 t b)" | "polysubst0 t (Pw p n) = Pw (polysubst0 t p) n" | "polysubst0 t (CN c n p) = (if n = 0 then Add (polysubst0 t c) (Mul t (polysubst0 t p)) else CN (polysubst0 t c) n (polysubst0 t p))" fun decrpoly:: "poly ⇒ poly" where "decrpoly (Bound n) = Bound (n - 1)" | "decrpoly (Neg a) = Neg (decrpoly a)" | "decrpoly (Add a b) = Add (decrpoly a) (decrpoly b)" | "decrpoly (Sub a b) = Sub (decrpoly a) (decrpoly b)" | "decrpoly (Mul a b) = Mul (decrpoly a) (decrpoly b)" | "decrpoly (Pw p n) = Pw (decrpoly p) n" | "decrpoly (CN c n p) = CN (decrpoly c) (n - 1) (decrpoly p)" | "decrpoly a = a" subsection ‹Degrees and heads and coefficients› fun degree :: "poly ⇒ nat" where "degree (CN c 0 p) = 1 + degree p" | "degree p = 0" fun head :: "poly ⇒ poly" where "head (CN c 0 p) = head p" | "head p = p" text ‹More general notions of degree and head.› fun degreen :: "poly ⇒ nat ⇒ nat" where "degreen (CN c n p) = (λm. if n = m then 1 + degreen p n else 0)" | "degreen p = (λm. 0)" fun headn :: "poly ⇒ nat ⇒ poly" where "headn (CN c n p) = (λm. if n ≤ m then headn p m else CN c n p)" | "headn p = (λm. p)" fun coefficients :: "poly ⇒ poly list" where "coefficients (CN c 0 p) = c # coefficients p" | "coefficients p = [p]" fun isconstant :: "poly ⇒ bool" where "isconstant (CN c 0 p) = False" | "isconstant p = True" fun behead :: "poly ⇒ poly" where "behead (CN c 0 p) = (let p' = behead p in if p' = 0⇩_{p}then c else CN c 0 p')" | "behead p = 0⇩_{p}" fun headconst :: "poly ⇒ Num" where "headconst (CN c n p) = headconst p" | "headconst (C n) = n" subsection ‹Operations for normalization› declare if_cong[fundef_cong del] declare let_cong[fundef_cong del] fun polyadd :: "poly ⇒ poly ⇒ poly" (infixl "+⇩_{p}" 60) where "polyadd (C c) (C c') = C (c +⇩_{N}c')" | "polyadd (C c) (CN c' n' p') = CN (polyadd (C c) c') n' p'" | "polyadd (CN c n p) (C c') = CN (polyadd c (C c')) n p" | "polyadd (CN c n p) (CN c' n' p') = (if n < n' then CN (polyadd c (CN c' n' p')) n p else if n' < n then CN (polyadd (CN c n p) c') n' p' else let cc' = polyadd c c'; pp' = polyadd p p' in if pp' = 0⇩_{p}then cc' else CN cc' n pp')" | "polyadd a b = Add a b" fun polyneg :: "poly ⇒ poly" ("~⇩_{p}") where "polyneg (C c) = C (~⇩_{N}c)" | "polyneg (CN c n p) = CN (polyneg c) n (polyneg p)" | "polyneg a = Neg a" definition polysub :: "poly ⇒ poly ⇒ poly" (infixl "-⇩_{p}" 60) where "p -⇩_{p}q = polyadd p (polyneg q)" fun polymul :: "poly ⇒ poly ⇒ poly" (infixl "*⇩_{p}" 60) where "polymul (C c) (C c') = C (c *⇩_{N}c')" | "polymul (C c) (CN c' n' p') = (if c = 0⇩_{N}then 0⇩_{p}else CN (polymul (C c) c') n' (polymul (C c) p'))" | "polymul (CN c n p) (C c') = (if c' = 0⇩_{N}then 0⇩_{p}else CN (polymul c (C c')) n (polymul p (C c')))" | "polymul (CN c n p) (CN c' n' p') = (if n < n' then CN (polymul c (CN c' n' p')) n (polymul p (CN c' n' p')) else if n' < n then CN (polymul (CN c n p) c') n' (polymul (CN c n p) p') else polyadd (polymul (CN c n p) c') (CN 0⇩_{p}n' (polymul (CN c n p) p')))" | "polymul a b = Mul a b" declare if_cong[fundef_cong] declare let_cong[fundef_cong] fun polypow :: "nat ⇒ poly ⇒ poly" where "polypow 0 = (λp. (1)⇩_{p})" | "polypow n = (λp. let q = polypow (n div 2) p; d = polymul q q in if even n then d else polymul p d)" abbreviation poly_pow :: "poly ⇒ nat ⇒ poly" (infixl "^⇩_{p}" 60) where "a ^⇩_{p}k ≡ polypow k a" function polynate :: "poly ⇒ poly" where "polynate (Bound n) = CN 0⇩_{p}n (1)⇩_{p}" | "polynate (Add p q) = polynate p +⇩_{p}polynate q" | "polynate (Sub p q) = polynate p -⇩_{p}polynate q" | "polynate (Mul p q) = polynate p *⇩_{p}polynate q" | "polynate (Neg p) = ~⇩_{p}(polynate p)" | "polynate (Pw p n) = polynate p ^⇩_{p}n" | "polynate (CN c n p) = polynate (Add c (Mul (Bound n) p))" | "polynate (C c) = C (normNum c)" by pat_completeness auto termination by (relation "measure polysize") auto fun poly_cmul :: "Num ⇒ poly ⇒ poly" where "poly_cmul y (C x) = C (y *⇩_{N}x)" | "poly_cmul y (CN c n p) = CN (poly_cmul y c) n (poly_cmul y p)" | "poly_cmul y p = C y *⇩_{p}p" definition monic :: "poly ⇒ poly × bool" where "monic p = (let h = headconst p in if h = 0⇩_{N}then (p, False) else (C (Ninv h) *⇩_{p}p, 0>⇩_{N}h))" subsection ‹Pseudo-division› definition shift1 :: "poly ⇒ poly" where "shift1 p = CN 0⇩_{p}0 p" abbreviation funpow :: "nat ⇒ ('a ⇒ 'a) ⇒ 'a ⇒ 'a" where "funpow ≡ compow" partial_function (tailrec) polydivide_aux :: "poly ⇒ nat ⇒ poly ⇒ nat ⇒ poly ⇒ nat × poly" where "polydivide_aux a n p k s = (if s = 0⇩_{p}then (k, s) else let b = head s; m = degree s in if m < n then (k,s) else let p' = funpow (m - n) shift1 p in if a = b then polydivide_aux a n p k (s -⇩_{p}p') else polydivide_aux a n p (Suc k) ((a *⇩_{p}s) -⇩_{p}(b *⇩_{p}p')))" definition polydivide :: "poly ⇒ poly ⇒ nat × poly" where "polydivide s p = polydivide_aux (head p) (degree p) p 0 s" fun poly_deriv_aux :: "nat ⇒ poly ⇒ poly" where "poly_deriv_aux n (CN c 0 p) = CN (poly_cmul ((int n)⇩_{N}) c) 0 (poly_deriv_aux (n + 1) p)" | "poly_deriv_aux n p = poly_cmul ((int n)⇩_{N}) p" fun poly_deriv :: "poly ⇒ poly" where "poly_deriv (CN c 0 p) = poly_deriv_aux 1 p" | "poly_deriv p = 0⇩_{p}" subsection ‹Semantics of the polynomial representation› primrec Ipoly :: "'a list ⇒ poly ⇒ 'a::{field_char_0,field,power}" where "Ipoly bs (C c) = INum c" | "Ipoly bs (Bound n) = bs!n" | "Ipoly bs (Neg a) = - Ipoly bs a" | "Ipoly bs (Add a b) = Ipoly bs a + Ipoly bs b" | "Ipoly bs (Sub a b) = Ipoly bs a - Ipoly bs b" | "Ipoly bs (Mul a b) = Ipoly bs a * Ipoly bs b" | "Ipoly bs (Pw t n) = Ipoly bs t ^ n" | "Ipoly bs (CN c n p) = Ipoly bs c + (bs!n) * Ipoly bs p" abbreviation Ipoly_syntax :: "poly ⇒ 'a list ⇒'a::{field_char_0,field,power}" ("⦇_⦈⇩_{p}⇗^{_⇖}") where "⦇p⦈⇩_{p}⇗^{bs⇖}≡ Ipoly bs p" lemma Ipoly_CInt: "Ipoly bs (C (i, 1)) = of_int i" by (simp add: INum_def) lemma Ipoly_CRat: "Ipoly bs (C (i, j)) = of_int i / of_int j" by (simp add: INum_def) lemmas RIpoly_eqs = Ipoly.simps(2-7) Ipoly_CInt Ipoly_CRat subsection ‹Normal form and normalization› fun isnpolyh:: "poly ⇒ nat ⇒ bool" where "isnpolyh (C c) = (λk. isnormNum c)" | "isnpolyh (CN c n p) = (λk. n ≥ k ∧ isnpolyh c (Suc n) ∧ isnpolyh p n ∧ p ≠ 0⇩_{p})" | "isnpolyh p = (λk. False)" lemma isnpolyh_mono: "n' ≤ n ⟹ isnpolyh p n ⟹ isnpolyh p n'" by (induct p rule: isnpolyh.induct) auto definition isnpoly :: "poly ⇒ bool" where "isnpoly p = isnpolyh p 0" text ‹polyadd preserves normal forms› lemma polyadd_normh: "isnpolyh p n0 ⟹ isnpolyh q n1 ⟹ isnpolyh (polyadd p q) (min n0 n1)" proof (induct p q arbitrary: n0 n1 rule: polyadd.induct) case (2 ab c' n' p' n0 n1) from 2 have th1: "isnpolyh (C ab) (Suc n')" by simp from 2(3) have th2: "isnpolyh c' (Suc n')" and nplen1: "n' ≥ n1" by simp_all with isnpolyh_mono have cp: "isnpolyh c' (Suc n')" by simp with 2(1)[OF th1 th2] have th3:"isnpolyh (C ab +⇩_{p}c') (Suc n')" by simp from nplen1 have n01len1: "min n0 n1 ≤ n'" by simp then show ?case using 2 th3 by simp next case (3 c' n' p' ab n1 n0) from 3 have th1: "isnpolyh (C ab) (Suc n')" by simp from 3(2) have th2: "isnpolyh c' (Suc n')" and nplen1: "n' ≥ n1" by simp_all with isnpolyh_mono have cp: "isnpolyh c' (Suc n')" by simp with 3(1)[OF th2 th1] have th3:"isnpolyh (c' +⇩_{p}C ab) (Suc n')" by simp from nplen1 have n01len1: "min n0 n1 ≤ n'" by simp then show ?case using 3 th3 by simp next case (4 c n p c' n' p' n0 n1) then have nc: "isnpolyh c (Suc n)" and np: "isnpolyh p n" by simp_all from 4 have nc': "isnpolyh c' (Suc n')" and np': "isnpolyh p' n'" by simp_all from 4 have ngen0: "n ≥ n0" by simp from 4 have n'gen1: "n' ≥ n1" by simp consider (eq) "n = n'" | (lt) "n < n'" | (gt) "n > n'" by arith then show ?case proof cases case eq with "4.hyps"(3)[OF nc nc'] have ncc':"isnpolyh (c +⇩_{p}c') (Suc n)" by auto then have ncc'n01: "isnpolyh (c +⇩_{p}c') (min n0 n1)" using isnpolyh_mono[where n'="min n0 n1" and n="Suc n"] ngen0 n'gen1 by auto from eq "4.hyps"(4)[OF np np'] have npp': "isnpolyh (p +⇩_{p}p') n" by simp have minle: "min n0 n1 ≤ n'" using ngen0 n'gen1 eq by simp from minle npp' ncc'n01 4 eq ngen0 n'gen1 ncc' show ?thesis by (simp add: Let_def) next case lt have "min n0 n1 ≤ n0" by simp with 4 lt have th1:"min n0 n1 ≤ n" by auto from 4 have th21: "isnpolyh c (Suc n)" by simp from 4 have th22: "isnpolyh (CN c' n' p') n'" by simp from lt have th23: "min (Suc n) n' = Suc n" by arith from "4.hyps"(1)[OF th21 th22] have "isnpolyh (polyadd c (CN c' n' p')) (Suc n)" using th23 by simp with 4 lt th1 show ?thesis by simp next case gt then have gt': "n' < n ∧ ¬ n < n'" by simp have "min n0 n1 ≤ n1" by simp with 4 gt have th1: "min n0 n1 ≤ n'" by auto from 4 have th21: "isnpolyh c' (Suc n')" by simp_all from 4 have th22: "isnpolyh (CN c n p) n" by simp from gt have th23: "min n (Suc n') = Suc n'" by arith from "4.hyps"(2)[OF th22 th21] have "isnpolyh (polyadd (CN c n p) c') (Suc n')" using th23 by simp with 4 gt th1 show ?thesis by simp qed qed auto lemma polyadd[simp]: "Ipoly bs (polyadd p q) = Ipoly bs p + Ipoly bs q" by (induct p q rule: polyadd.induct) (auto simp add: Let_def field_simps distrib_left[symmetric] simp del: distrib_left_NO_MATCH) lemma polyadd_norm: "isnpoly p ⟹ isnpoly q ⟹ isnpoly (polyadd p q)" using polyadd_normh[of p 0 q 0] isnpoly_def by simp text ‹The degree of addition and other general lemmas needed for the normal form of polymul.› lemma polyadd_different_degreen: assumes "isnpolyh p n0" and "isnpolyh q n1" and "degreen p m ≠ degreen q m" and "m ≤ min n0 n1" shows "degreen (polyadd p q) m = max (degreen p m) (degreen q m)" using assms proof (induct p q arbitrary: m n0 n1 rule: polyadd.induct) case (4 c n p c' n' p' m n0 n1) show ?case proof (cases "n = n'") case True with 4(4)[of n n m] 4(3)[of "Suc n" "Suc n" m] 4(5-7) show ?thesis by (auto simp: Let_def) next case False with 4 show ?thesis by auto qed qed auto lemma headnz[simp]: "isnpolyh p n ⟹ p ≠ 0⇩_{p}⟹ headn p m ≠ 0⇩_{p}" by (induct p arbitrary: n rule: headn.induct) auto lemma degree_isnpolyh_Suc[simp]: "isnpolyh p (Suc n) ⟹ degree p = 0" by (induct p arbitrary: n rule: degree.induct) auto lemma degreen_0[simp]: "isnpolyh p n ⟹ m < n ⟹ degreen p m = 0" by (induct p arbitrary: n rule: degreen.induct) auto lemma degree_isnpolyh_Suc': "n > 0 ⟹ isnpolyh p n ⟹ degree p = 0" by (induct p arbitrary: n rule: degree.induct) auto lemma degree_npolyhCN[simp]: "isnpolyh (CN c n p) n0 ⟹ degree c = 0" using degree_isnpolyh_Suc by auto lemma degreen_npolyhCN[simp]: "isnpolyh (CN c n p) n0 ⟹ degreen c n = 0" using degreen_0 by auto lemma degreen_polyadd: assumes np: "isnpolyh p n0" and nq: "isnpolyh q n1" and m: "m ≤ max n0 n1" shows "degreen (p +⇩_{p}q) m ≤ max (degreen p m) (degreen q m)" using np nq m proof (induct p q arbitrary: n0 n1 m rule: polyadd.induct) case (2 c c' n' p' n0 n1) then show ?case by (cases n') simp_all next case (3 c n p c' n0 n1) then show ?case by (cases n) auto next case (4 c n p c' n' p' n0 n1 m) show ?case proof (cases "n = n'") case True with 4(4)[of n n m] 4(3)[of "Suc n" "Suc n" m] 4(5-7) show ?thesis by (auto simp: Let_def) next case False then show ?thesis by simp qed qed auto lemma polyadd_eq_const_degreen: assumes "isnpolyh p n0" and "isnpolyh q n1" and "polyadd p q = C c" shows "degreen p m = degreen q m" using assms proof (induct p q arbitrary: m n0 n1 c rule: polyadd.induct) case (4 c n p c' n' p' m n0 n1 x) consider "n = n'" | "n > n' ∨ n < n'" by arith then show ?case proof cases case 1 with 4 show ?thesis by (cases "p +⇩_{p}p' = 0⇩_{p}") (auto simp add: Let_def) next case 2 with 4 show ?thesis by auto qed qed simp_all lemma polymul_properties: assumes "SORT_CONSTRAINT('a::{field_char_0,field})" and np: "isnpolyh p n0" and nq: "isnpolyh q n1" and m: "m ≤ min n0 n1" shows "isnpolyh (p *⇩_{p}q) (min n0 n1)" and "p *⇩_{p}q = 0⇩_{p}⟷ p = 0⇩_{p}∨ q = 0⇩_{p}" and "degreen (p *⇩_{p}q) m = (if p = 0⇩_{p}∨ q = 0⇩_{p}then 0 else degreen p m + degreen q m)" using np nq m proof (induct p q arbitrary: n0 n1 m rule: polymul.induct) case (2 c c' n' p') { case (1 n0 n1) with "2.hyps"(4-6)[of n' n' n'] and "2.hyps"(1-3)[of "Suc n'" "Suc n'" n'] show ?case by (auto simp add: min_def) next case (2 n0 n1) then show ?case by auto next case (3 n0 n1) then show ?case using "2.hyps" by auto } next case (3 c n p c') { case (1 n0 n1) with "3.hyps"(4-6)[of n n n] and "3.hyps"(1-3)[of "Suc n" "Suc n" n] show ?case by (auto simp add: min_def) next case (2 n0 n1) then show ?case by auto next case (3 n0 n1) then show ?case using "3.hyps" by auto } next case (4 c n p c' n' p') let ?cnp = "CN c n p" let ?cnp' = "CN c' n' p'" { case (1 n0 n1) then have cnp: "isnpolyh ?cnp n" and cnp': "isnpolyh ?cnp' n'" and np: "isnpolyh p n" and nc: "isnpolyh c (Suc n)" and np': "isnpolyh p' n'" and nc': "isnpolyh c' (Suc n')" and nn0: "n ≥ n0" and nn1: "n' ≥ n1" by simp_all { assume "n < n'" with "4.hyps"(4-5)[OF np cnp', of n] and "4.hyps"(1)[OF nc cnp', of n] nn0 cnp have ?case by (simp add: min_def) } moreover { assume "n' < n" with "4.hyps"(16-17)[OF cnp np', of "n'"] and "4.hyps"(13)[OF cnp nc', of "Suc n'"] nn1 cnp' have ?case by (cases "Suc n' = n") (simp_all add: min_def) } moreover { assume "n' = n" with "4.hyps"(16-17)[OF cnp np', of n] and "4.hyps"(13)[OF cnp nc', of n] cnp cnp' nn1 nn0 have ?case apply (auto intro!: polyadd_normh) apply (simp_all add: min_def isnpolyh_mono[OF nn0]) done } ultimately show ?case by arith next fix n0 n1 m assume np: "isnpolyh ?cnp n0" assume np':"isnpolyh ?cnp' n1" assume m: "m ≤ min n0 n1" let ?d = "degreen (?cnp *⇩_{p}?cnp') m" let ?d1 = "degreen ?cnp m" let ?d2 = "degreen ?cnp' m" let ?eq = "?d = (if ?cnp = 0⇩_{p}∨ ?cnp' = 0⇩_{p}then 0 else ?d1 + ?d2)" have "n' < n ∨ n < n' ∨ n' = n" by auto moreover { assume "n' < n ∨ n < n'" with "4.hyps"(3,6,18) np np' m have ?eq by auto } moreover { assume nn': "n' = n" then have nn: "¬ n' < n ∧ ¬ n < n'" by arith from "4.hyps"(16,18)[of n n' n] "4.hyps"(13,14)[of n "Suc n'" n] np np' nn' have norm: "isnpolyh ?cnp n" "isnpolyh c' (Suc n)" "isnpolyh (?cnp *⇩_{p}c') n" "isnpolyh p' n" "isnpolyh (?cnp *⇩_{p}p') n" "isnpolyh (CN 0⇩_{p}n (CN c n p *⇩_{p}p')) n" "?cnp *⇩_{p}c' = 0⇩_{p}⟷ c' = 0⇩_{p}" "?cnp *⇩_{p}p' ≠ 0⇩_{p}" by (auto simp add: min_def) { assume mn: "m = n" from "4.hyps"(17,18)[OF norm(1,4), of n] "4.hyps"(13,15)[OF norm(1,2), of n] norm nn' mn have degs: "degreen (?cnp *⇩_{p}c') n = (if c' = 0⇩_{p}then 0 else ?d1 + degreen c' n)" "degreen (?cnp *⇩_{p}p') n = ?d1 + degreen p' n" by (simp_all add: min_def) from degs norm have th1: "degreen (?cnp *⇩_{p}c') n < degreen (CN 0⇩_{p}n (?cnp *⇩_{p}p')) n" by simp then have neq: "degreen (?cnp *⇩_{p}c') n ≠ degreen (CN 0⇩_{p}n (?cnp *⇩_{p}p')) n" by simp have nmin: "n ≤ min n n" by (simp add: min_def) from polyadd_different_degreen[OF norm(3,6) neq nmin] th1 have deg: "degreen (CN c n p *⇩_{p}c' +⇩_{p}CN 0⇩_{p}n (CN c n p *⇩_{p}p')) n = degreen (CN 0⇩_{p}n (CN c n p *⇩_{p}p')) n" by simp from "4.hyps"(16-18)[OF norm(1,4), of n] "4.hyps"(13-15)[OF norm(1,2), of n] mn norm m nn' deg have ?eq by simp } moreover { assume mn: "m ≠ n" then have mn': "m < n" using m np by auto from nn' m np have max1: "m ≤ max n n" by simp then have min1: "m ≤ min n n" by simp then have min2: "m ≤ min n (Suc n)" by simp from "4.hyps"(16-18)[OF norm(1,4) min1] "4.hyps"(13-15)[OF norm(1,2) min2] degreen_polyadd[OF norm(3,6) max1] have "degreen (?cnp *⇩_{p}c' +⇩_{p}CN 0⇩_{p}n (?cnp *⇩_{p}p')) m ≤ max (degreen (?cnp *⇩_{p}c') m) (degreen (CN 0⇩_{p}n (?cnp *⇩_{p}p')) m)" using mn nn' np np' by simp with "4.hyps"(16-18)[OF norm(1,4) min1] "4.hyps"(13-15)[OF norm(1,2) min2] degreen_0[OF norm(3) mn'] have ?eq using nn' mn np np' by clarsimp } ultimately have ?eq by blast } ultimately show ?eq by blast } { case (2 n0 n1) then have np: "isnpolyh ?cnp n0" and np': "isnpolyh ?cnp' n1" and m: "m ≤ min n0 n1" by simp_all then have mn: "m ≤ n" by simp let ?c0p = "CN 0⇩_{p}n (?cnp *⇩_{p}p')" { assume C: "?cnp *⇩_{p}c' +⇩_{p}?c0p = 0⇩_{p}" "n' = n" then have nn: "¬ n' < n ∧ ¬ n < n'" by simp from "4.hyps"(16-18) [of n n n] "4.hyps"(13-15)[of n "Suc n" n] np np' C(2) mn have norm: "isnpolyh ?cnp n" "isnpolyh c' (Suc n)" "isnpolyh (?cnp *⇩_{p}c') n" "isnpolyh p' n" "isnpolyh (?cnp *⇩_{p}p') n" "isnpolyh (CN 0⇩_{p}n (CN c n p *⇩_{p}p')) n" "?cnp *⇩_{p}c' = 0⇩_{p}⟷ c' = 0⇩_{p}" "?cnp *⇩_{p}p' ≠ 0⇩_{p}" "degreen (?cnp *⇩_{p}c') n = (if c' = 0⇩_{p}then 0 else degreen ?cnp n + degreen c' n)" "degreen (?cnp *⇩_{p}p') n = degreen ?cnp n + degreen p' n" by (simp_all add: min_def) from norm have cn: "isnpolyh (CN 0⇩_{p}n (CN c n p *⇩_{p}p')) n" by simp have degneq: "degreen (?cnp *⇩_{p}c') n < degreen (CN 0⇩_{p}n (?cnp *⇩_{p}p')) n" using norm by simp from polyadd_eq_const_degreen[OF norm(3) cn C(1), where m="n"] degneq have False by simp } then show ?case using "4.hyps" by clarsimp } qed auto lemma polymul[simp]: "Ipoly bs (p *⇩_{p}q) = Ipoly bs p * Ipoly bs q" by (induct p q rule: polymul.induct) (auto simp add: field_simps) lemma polymul_normh: assumes "SORT_CONSTRAINT('a::{field_char_0,field})" shows "isnpolyh p n0 ⟹ isnpolyh q n1 ⟹ isnpolyh (p *⇩_{p}q) (min n0 n1)" using polymul_properties(1) by blast lemma polymul_eq0_iff: assumes "SORT_CONSTRAINT('a::{field_char_0,field})" shows "isnpolyh p n0 ⟹ isnpolyh q n1 ⟹ p *⇩_{p}q = 0⇩_{p}⟷ p = 0⇩_{p}∨ q = 0⇩_{p}" using polymul_properties(2) by blast lemma polymul_degreen: assumes "SORT_CONSTRAINT('a::{field_char_0,field})" shows "isnpolyh p n0 ⟹ isnpolyh q n1 ⟹ m ≤ min n0 n1 ⟹ degreen (p *⇩_{p}q) m = (if p = 0⇩_{p}∨ q = 0⇩_{p}then 0 else degreen p m + degreen q m)" by (fact polymul_properties(3)) lemma polymul_norm: assumes "SORT_CONSTRAINT('a::{field_char_0,field})" shows "isnpoly p ⟹ isnpoly q ⟹ isnpoly (polymul p q)" using polymul_normh[of "p" "0" "q" "0"] isnpoly_def by simp lemma headconst_zero: "isnpolyh p n0 ⟹ headconst p = 0⇩_{N}⟷ p = 0⇩_{p}" by (induct p arbitrary: n0 rule: headconst.induct) auto lemma headconst_isnormNum: "isnpolyh p n0 ⟹ isnormNum (headconst p)" by (induct p arbitrary: n0) auto lemma monic_eqI: assumes np: "isnpolyh p n0" shows "INum (headconst p) * Ipoly bs (fst (monic p)) = (Ipoly bs p ::'a::{field_char_0,field, power})" unfolding monic_def Let_def proof (cases "headconst p = 0⇩_{N}", simp_all add: headconst_zero[OF np]) let ?h = "headconst p" assume pz: "p ≠ 0⇩_{p}" { assume hz: "INum ?h = (0::'a)" from headconst_isnormNum[OF np] have norm: "isnormNum ?h" "isnormNum 0⇩_{N}" by simp_all from isnormNum_unique[where ?'a = 'a, OF norm] hz have "?h = 0⇩_{N}" by simp with headconst_zero[OF np] have "p = 0⇩_{p}" by blast with pz have False by blast } then show "INum (headconst p) = (0::'a) ⟶ ⦇p⦈⇩_{p}⇗^{bs⇖}= 0" by blast qed text ‹polyneg is a negation and preserves normal forms› lemma polyneg[simp]: "Ipoly bs (polyneg p) = - Ipoly bs p" by (induct p rule: polyneg.induct) auto lemma polyneg0: "isnpolyh p n ⟹ (~⇩_{p}p) = 0⇩_{p}⟷ p = 0⇩_{p}" by (induct p arbitrary: n rule: polyneg.induct) (auto simp add: Nneg_def) lemma polyneg_polyneg: "isnpolyh p n0 ⟹ ~⇩_{p}(~⇩_{p}p) = p" by (induct p arbitrary: n0 rule: polyneg.induct) auto lemma polyneg_normh: "isnpolyh p n ⟹ isnpolyh (polyneg p) n" by (induct p arbitrary: n rule: polyneg.induct) (auto simp add: polyneg0) lemma polyneg_norm: "isnpoly p ⟹ isnpoly (polyneg p)" using isnpoly_def polyneg_normh by simp text ‹polysub is a substraction and preserves normal forms› lemma polysub[simp]: "Ipoly bs (polysub p q) = Ipoly bs p - Ipoly bs q" by (simp add: polysub_def) lemma polysub_normh: "isnpolyh p n0 ⟹ isnpolyh q n1 ⟹ isnpolyh (polysub p q) (min n0 n1)" by (simp add: polysub_def polyneg_normh polyadd_normh) lemma polysub_norm: "isnpoly p ⟹ isnpoly q ⟹ isnpoly (polysub p q)" using polyadd_norm polyneg_norm by (simp add: polysub_def) lemma polysub_same_0[simp]: assumes "SORT_CONSTRAINT('a::{field_char_0,field})" shows "isnpolyh p n0 ⟹ polysub p p = 0⇩_{p}" unfolding polysub_def split_def fst_conv snd_conv by (induct p arbitrary: n0) (auto simp add: Let_def Nsub0[simplified Nsub_def]) lemma polysub_0: assumes "SORT_CONSTRAINT('a::{field_char_0,field})" shows "isnpolyh p n0 ⟹ isnpolyh q n1 ⟹ p -⇩_{p}q = 0⇩_{p}⟷ p = q" unfolding polysub_def split_def fst_conv snd_conv by (induct p q arbitrary: n0 n1 rule:polyadd.induct) (auto simp: Nsub0[simplified Nsub_def] Let_def) text ‹polypow is a power function and preserves normal forms› lemma polypow[simp]: "Ipoly bs (polypow n p) = (Ipoly bs p :: 'a::{field_char_0,field}) ^ n" proof (induct n rule: polypow.induct) case 1 then show ?case by simp next case (2 n) let ?q = "polypow ((Suc n) div 2) p" let ?d = "polymul ?q ?q" have "odd (Suc n) ∨ even (Suc n)" by simp moreover { assume odd: "odd (Suc n)" have th: "(Suc (Suc (Suc 0) * (Suc n div Suc (Suc 0)))) = Suc n div 2 + Suc n div 2 + 1" by arith from odd have "Ipoly bs (p ^⇩_{p}Suc n) = Ipoly bs (polymul p ?d)" by (simp add: Let_def) also have "… = (Ipoly bs p) * (Ipoly bs p)^(Suc n div 2) * (Ipoly bs p)^(Suc n div 2)" using "2.hyps" by simp also have "… = (Ipoly bs p) ^ (Suc n div 2 + Suc n div 2 + 1)" by (simp only: power_add power_one_right) simp also have "… = (Ipoly bs p) ^ (Suc (Suc (Suc 0) * (Suc n div Suc (Suc 0))))" by (simp only: th) finally have ?case unfolding numeral_2_eq_2 [symmetric] using odd_two_times_div_two_nat [OF odd] by simp } moreover { assume even: "even (Suc n)" from even have "Ipoly bs (p ^⇩_{p}Suc n) = Ipoly bs ?d" by (simp add: Let_def) also have "… = (Ipoly bs p) ^ (2 * (Suc n div 2))" using "2.hyps" by (simp only: mult_2 power_add) simp finally have ?case using even_two_times_div_two [OF even] by simp } ultimately show ?case by blast qed lemma polypow_normh: assumes "SORT_CONSTRAINT('a::{field_char_0,field})" shows "isnpolyh p n ⟹ isnpolyh (polypow k p) n" proof (induct k arbitrary: n rule: polypow.induct) case 1 then show ?case by auto next case (2 k n) let ?q = "polypow (Suc k div 2) p" let ?d = "polymul ?q ?q" from 2 have th1: "isnpolyh ?q n" and th2: "isnpolyh p n" by blast+ from polymul_normh[OF th1 th1] have dn: "isnpolyh ?d n" by simp from polymul_normh[OF th2 dn] have on: "isnpolyh (polymul p ?d) n" by simp from dn on show ?case by (simp, unfold Let_def) auto qed lemma polypow_norm: assumes "SORT_CONSTRAINT('a::{field_char_0,field})" shows "isnpoly p ⟹ isnpoly (polypow k p)" by (simp add: polypow_normh isnpoly_def) text ‹Finally the whole normalization› lemma polynate [simp]: "Ipoly bs (polynate p) = (Ipoly bs p :: 'a ::{field_char_0,field})" by (induct p rule:polynate.induct) auto lemma polynate_norm[simp]: assumes "SORT_CONSTRAINT('a::{field_char_0,field})" shows "isnpoly (polynate p)" by (induct p rule: polynate.induct) (simp_all add: polyadd_norm polymul_norm polysub_norm polyneg_norm polypow_norm, simp_all add: isnpoly_def) text ‹shift1› lemma shift1: "Ipoly bs (shift1 p) = Ipoly bs (Mul (Bound 0) p)" by (simp add: shift1_def) lemma shift1_isnpoly: assumes "isnpoly p" and "p ≠ 0⇩_{p}" shows "isnpoly (shift1 p) " using assms by (simp add: shift1_def isnpoly_def) lemma shift1_nz[simp]:"shift1 p ≠ 0⇩_{p}" by (simp add: shift1_def) lemma funpow_shift1_isnpoly: "isnpoly p ⟹ p ≠ 0⇩_{p}⟹ isnpoly (funpow n shift1 p)" by (induct n arbitrary: p) (auto simp add: shift1_isnpoly funpow_swap1) lemma funpow_isnpolyh: assumes "⋀p. isnpolyh p n ⟹ isnpolyh (f p) n" and "isnpolyh p n" shows "isnpolyh (funpow k f p) n" using assms by (induct k arbitrary: p) auto lemma funpow_shift1: "(Ipoly bs (funpow n shift1 p) :: 'a :: {field_char_0,field}) = Ipoly bs (Mul (Pw (Bound 0) n) p)" by (induct n arbitrary: p) (simp_all add: shift1_isnpoly shift1) lemma shift1_isnpolyh: "isnpolyh p n0 ⟹ p ≠ 0⇩_{p}⟹ isnpolyh (shift1 p) 0" using isnpolyh_mono[where n="n0" and n'="0" and p="p"] by (simp add: shift1_def) lemma funpow_shift1_1: "(Ipoly bs (funpow n shift1 p) :: 'a :: {field_char_0,field}) = Ipoly bs (funpow n shift1 (1)⇩_{p}*⇩_{p}p)" by (simp add: funpow_shift1) lemma poly_cmul[simp]: "Ipoly bs (poly_cmul c p) = Ipoly bs (Mul (C c) p)" by (induct p rule: poly_cmul.induct) (auto simp add: field_simps) lemma behead: assumes "isnpolyh p n" shows "Ipoly bs (Add (Mul (head p) (Pw (Bound 0) (degree p))) (behead p)) = (Ipoly bs p :: 'a :: {field_char_0,field})" using assms proof (induct p arbitrary: n rule: behead.induct) case (1 c p n) then have pn: "isnpolyh p n" by simp from 1(1)[OF pn] have th:"Ipoly bs (Add (Mul (head p) (Pw (Bound 0) (degree p))) (behead p)) = Ipoly bs p" . then show ?case using "1.hyps" apply (simp add: Let_def,cases "behead p = 0⇩_{p}") apply (simp_all add: th[symmetric] field_simps) done qed (auto simp add: Let_def) lemma behead_isnpolyh: assumes "isnpolyh p n" shows "isnpolyh (behead p) n" using assms by (induct p rule: behead.induct) (auto simp add: Let_def isnpolyh_mono) subsection ‹Miscellaneous lemmas about indexes, decrementation, substitution etc ...› lemma isnpolyh_polybound0: "isnpolyh p (Suc n) ⟹ polybound0 p" proof (induct p arbitrary: n rule: poly.induct, auto, goal_cases) case prems: (1 c n p n') then have "n = Suc (n - 1)" by simp then have "isnpolyh p (Suc (n - 1))" using ‹isnpolyh p n› by simp with prems(2) show ?case by simp qed lemma isconstant_polybound0: "isnpolyh p n0 ⟹ isconstant p ⟷ polybound0 p" by (induct p arbitrary: n0 rule: isconstant.induct) (auto simp add: isnpolyh_polybound0) lemma decrpoly_zero[simp]: "decrpoly p = 0⇩_{p}⟷ p = 0⇩_{p}" by (induct p) auto lemma decrpoly_normh: "isnpolyh p n0 ⟹ polybound0 p ⟹ isnpolyh (decrpoly p) (n0 - 1)" apply (induct p arbitrary: n0) apply auto apply atomize apply (rename_tac nat a b, erule_tac x = "Suc nat" in allE) apply auto done lemma head_polybound0: "isnpolyh p n0 ⟹ polybound0 (head p)" by (induct p arbitrary: n0 rule: head.induct) (auto intro: isnpolyh_polybound0) lemma polybound0_I: assumes "polybound0 a" shows "Ipoly (b # bs) a = Ipoly (b' # bs) a" using assms by (induct a rule: poly.induct) auto lemma polysubst0_I: "Ipoly (b # bs) (polysubst0 a t) = Ipoly ((Ipoly (b # bs) a) # bs) t" by (induct t) simp_all lemma polysubst0_I': assumes "polybound0 a" shows "Ipoly (b # bs) (polysubst0 a t) = Ipoly ((Ipoly (b' # bs) a) # bs) t" by (induct t) (simp_all add: polybound0_I[OF assms, where b="b" and b'="b'"]) lemma decrpoly: assumes "polybound0 t" shows "Ipoly (x # bs) t = Ipoly bs (decrpoly t)" using assms by (induct t rule: decrpoly.induct) simp_all lemma polysubst0_polybound0: assumes "polybound0 t" shows "polybound0 (polysubst0 t a)" using assms by (induct a rule: poly.induct) auto lemma degree0_polybound0: "isnpolyh p n ⟹ degree p = 0 ⟹ polybound0 p" by (induct p arbitrary: n rule: degree.induct) (auto simp add: isnpolyh_polybound0) primrec maxindex :: "poly ⇒ nat" where "maxindex (Bound n) = n + 1" | "maxindex (CN c n p) = max (n + 1) (max (maxindex c) (maxindex p))" | "maxindex (Add p q) = max (maxindex p) (maxindex q)" | "maxindex (Sub p q) = max (maxindex p) (maxindex q)" | "maxindex (Mul p q) = max (maxindex p) (maxindex q)" | "maxindex (Neg p) = maxindex p" | "maxindex (Pw p n) = maxindex p" | "maxindex (C x) = 0" definition wf_bs :: "'a list ⇒ poly ⇒ bool" where "wf_bs bs p ⟷ length bs ≥ maxindex p" lemma wf_bs_coefficients: "wf_bs bs p ⟹ ∀c ∈ set (coefficients p). wf_bs bs c" proof (induct p rule: coefficients.induct) case (1 c p) show ?case proof fix x assume xc: "x ∈ set (coefficients (CN c 0 p))" then have "x = c ∨ x ∈ set (coefficients p)" by simp moreover { assume "x = c" then have "wf_bs bs x" using "1.prems" unfolding wf_bs_def by simp } moreover { assume H: "x ∈ set (coefficients p)" from "1.prems" have "wf_bs bs p" unfolding wf_bs_def by simp with "1.hyps" H have "wf_bs bs x" by blast } ultimately show "wf_bs bs x" by blast qed qed simp_all lemma maxindex_coefficients: "∀c ∈ set (coefficients p). maxindex c ≤ maxindex p" by (induct p rule: coefficients.induct) auto lemma wf_bs_I: "wf_bs bs p ⟹ Ipoly (bs @ bs') p = Ipoly bs p" unfolding wf_bs_def by (induct p) (auto simp add: nth_append) lemma take_maxindex_wf: assumes wf: "wf_bs bs p" shows "Ipoly (take (maxindex p) bs) p = Ipoly bs p" proof - let ?ip = "maxindex p" let ?tbs = "take ?ip bs" from wf have "length ?tbs = ?ip" unfolding wf_bs_def by simp then have wf': "wf_bs ?tbs p" unfolding wf_bs_def by simp have eq: "bs = ?tbs @ drop ?ip bs" by simp from wf_bs_I[OF wf', of "drop ?ip bs"] show ?thesis using eq by simp qed lemma decr_maxindex: "polybound0 p ⟹ maxindex (decrpoly p) = maxindex p - 1" by (induct p) auto lemma wf_bs_insensitive: "length bs = length bs' ⟹ wf_bs bs p = wf_bs bs' p" unfolding wf_bs_def by simp lemma wf_bs_insensitive': "wf_bs (x # bs) p = wf_bs (y # bs) p" unfolding wf_bs_def by simp lemma wf_bs_coefficients': "∀c ∈ set (coefficients p). wf_bs bs c ⟹ wf_bs (x # bs) p" by (induct p rule: coefficients.induct) (auto simp add: wf_bs_def) lemma coefficients_Nil[simp]: "coefficients p ≠ []" by (induct p rule: coefficients.induct) simp_all lemma coefficients_head: "last (coefficients p) = head p" by (induct p rule: coefficients.induct) auto lemma wf_bs_decrpoly: "wf_bs bs (decrpoly p) ⟹ wf_bs (x # bs) p" unfolding wf_bs_def by (induct p rule: decrpoly.induct) auto lemma length_le_list_ex: "length xs ≤ n ⟹ ∃ys. length (xs @ ys) = n" apply (rule exI[where x="replicate (n - length xs) z" for z]) apply simp done lemma isnpolyh_Suc_const: "isnpolyh p (Suc n) ⟹ isconstant p" apply (cases p) apply auto apply (rename_tac nat a, case_tac "nat") apply simp_all done lemma wf_bs_polyadd: "wf_bs bs p ∧ wf_bs bs q ⟶ wf_bs bs (p +⇩_{p}q)" unfolding wf_bs_def by (induct p q rule: polyadd.induct) (auto simp add: Let_def) lemma wf_bs_polyul: "wf_bs bs p ⟹ wf_bs bs q ⟹ wf_bs bs (p *⇩_{p}q)" unfolding wf_bs_def apply (induct p q arbitrary: bs rule: polymul.induct) apply (simp_all add: wf_bs_polyadd) apply clarsimp apply (rule wf_bs_polyadd[unfolded wf_bs_def, rule_format]) apply auto done lemma wf_bs_polyneg: "wf_bs bs p ⟹ wf_bs bs (~⇩_{p}p)" unfolding wf_bs_def by (induct p rule: polyneg.induct) auto lemma wf_bs_polysub: "wf_bs bs p ⟹ wf_bs bs q ⟹ wf_bs bs (p -⇩_{p}q)" unfolding polysub_def split_def fst_conv snd_conv using wf_bs_polyadd wf_bs_polyneg by blast subsection ‹Canonicity of polynomial representation, see lemma isnpolyh_unique› definition "polypoly bs p = map (Ipoly bs) (coefficients p)" definition "polypoly' bs p = map (Ipoly bs ∘ decrpoly) (coefficients p)" definition "poly_nate bs p = map (Ipoly bs ∘ decrpoly) (coefficients (polynate p))" lemma coefficients_normh: "isnpolyh p n0 ⟹ ∀q ∈ set (coefficients p). isnpolyh q n0" proof (induct p arbitrary: n0 rule: coefficients.induct) case (1 c p n0) have cp: "isnpolyh (CN c 0 p) n0" by fact then have norm: "isnpolyh c 0" "isnpolyh p 0" "p ≠ 0⇩_{p}" "n0 = 0" by (auto simp add: isnpolyh_mono[where n'=0]) from "1.hyps"[OF norm(2)] norm(1) norm(4) show ?case by simp qed auto lemma coefficients_isconst: "isnpolyh p n ⟹ ∀q ∈ set (coefficients p). isconstant q" by (induct p arbitrary: n rule: coefficients.induct) (auto simp add: isnpolyh_Suc_const) lemma polypoly_polypoly': assumes np: "isnpolyh p n0" shows "polypoly (x # bs) p = polypoly' bs p" proof - let ?cf = "set (coefficients p)" from coefficients_normh[OF np] have cn_norm: "∀ q∈ ?cf. isnpolyh q n0" . { fix q assume q: "q ∈ ?cf" from q cn_norm have th: "isnpolyh q n0" by blast from coefficients_isconst[OF np] q have "isconstant q" by blast with isconstant_polybound0[OF th] have "polybound0 q" by blast } then have "∀q ∈ ?cf. polybound0 q" .. then have "∀q ∈ ?cf. Ipoly (x # bs) q = Ipoly bs (decrpoly q)" using polybound0_I[where b=x and bs=bs and b'=y] decrpoly[where x=x and bs=bs] by auto then show ?thesis unfolding polypoly_def polypoly'_def by simp qed lemma polypoly_poly: assumes "isnpolyh p n0" shows "Ipoly (x # bs) p = poly (polypoly (x # bs) p) x" using assms by (induct p arbitrary: n0 bs rule: coefficients.induct) (auto simp add: polypoly_def) lemma polypoly'_poly: assumes "isnpolyh p n0" shows "⦇p⦈⇩_{p}⇗^{x # bs⇖}= poly (polypoly' bs p) x" using polypoly_poly[OF assms, simplified polypoly_polypoly'[OF assms]] . lemma polypoly_poly_polybound0: assumes "isnpolyh p n0" and "polybound0 p" shows "polypoly bs p = [Ipoly bs p]" using assms unfolding polypoly_def apply (cases p) apply auto apply (rename_tac nat a, case_tac nat) apply auto done lemma head_isnpolyh: "isnpolyh p n0 ⟹ isnpolyh (head p) n0" by (induct p rule: head.induct) auto lemma headn_nz[simp]: "isnpolyh p n0 ⟹ headn p m = 0⇩_{p}⟷ p = 0⇩_{p}" by (cases p) auto lemma head_eq_headn0: "head p = headn p 0" by (induct p rule: head.induct) simp_all lemma head_nz[simp]: "isnpolyh p n0 ⟹ head p = 0⇩_{p}⟷ p = 0⇩_{p}" by (simp add: head_eq_headn0) lemma isnpolyh_zero_iff: assumes nq: "isnpolyh p n0" and eq :"∀bs. wf_bs bs p ⟶ ⦇p⦈⇩_{p}⇗^{bs⇖}= (0::'a::{field_char_0,field, power})" shows "p = 0⇩_{p}" using nq eq proof (induct "maxindex p" arbitrary: p n0 rule: less_induct) case less note np = ‹isnpolyh p n0› and zp = ‹∀bs. wf_bs bs p ⟶ ⦇p⦈⇩_{p}⇗^{bs⇖}= (0::'a)› { assume nz: "maxindex p = 0" then obtain c where "p = C c" using np by (cases p) auto with zp np have "p = 0⇩_{p}" unfolding wf_bs_def by simp } moreover { assume nz: "maxindex p ≠ 0" let ?h = "head p" let ?hd = "decrpoly ?h" let ?ihd = "maxindex ?hd" from head_isnpolyh[OF np] head_polybound0[OF np] have h: "isnpolyh ?h n0" "polybound0 ?h" by simp_all then have nhd: "isnpolyh ?hd (n0 - 1)" using decrpoly_normh by blast from maxindex_coefficients[of p] coefficients_head[of p, symmetric] have mihn: "maxindex ?h ≤ maxindex p" by auto with decr_maxindex[OF h(2)] nz have ihd_lt_n: "?ihd < maxindex p" by auto { fix bs :: "'a list" assume bs: "wf_bs bs ?hd" let ?ts = "take ?ihd bs" let ?rs = "drop ?ihd bs" have ts: "wf_bs ?ts ?hd" using bs unfolding wf_bs_def by simp have bs_ts_eq: "?ts @ ?rs = bs" by simp from wf_bs_decrpoly[OF ts] have tsh: " ∀x. wf_bs (x # ?ts) ?h" by simp from ihd_lt_n have "∀x. length (x # ?ts) ≤ maxindex p" by simp with length_le_list_ex obtain xs where xs: "length ((x # ?ts) @ xs) = maxindex p" by blast then have "∀x. wf_bs ((x # ?ts) @ xs) p" unfolding wf_bs_def by simp with zp have "∀x. Ipoly ((x # ?ts) @ xs) p = 0" by blast then have "∀x. Ipoly (x # (?ts @ xs)) p = 0" by simp with polypoly_poly[OF np, where ?'a = 'a] polypoly_polypoly'[OF np, where ?'a = 'a] have "∀x. poly (polypoly' (?ts @ xs) p) x = poly [] x" by simp then have "poly (polypoly' (?ts @ xs) p) = poly []" by auto then have "∀c ∈ set (coefficients p). Ipoly (?ts @ xs) (decrpoly c) = 0" using poly_zero[where ?'a='a] by (simp add: polypoly'_def) with coefficients_head[of p, symmetric] have th0: "Ipoly (?ts @ xs) ?hd = 0" by simp from bs have wf'': "wf_bs ?ts ?hd" unfolding wf_bs_def by simp with th0 wf_bs_I[of ?ts ?hd xs] have "Ipoly ?ts ?hd = 0" by simp with wf'' wf_bs_I[of ?ts ?hd ?rs] bs_ts_eq have "⦇?hd⦈⇩_{p}⇗^{bs⇖}= 0" by simp } then have hdz: "∀bs. wf_bs bs ?hd ⟶ ⦇?hd⦈⇩_{p}⇗^{bs⇖}= (0::'a)" by blast from less(1)[OF ihd_lt_n nhd] hdz have "?hd = 0⇩_{p}" by blast then have "?h = 0⇩_{p}" by simp with head_nz[OF np] have "p = 0⇩_{p}" by simp } ultimately show "p = 0⇩_{p}" by blast qed lemma isnpolyh_unique: assumes np: "isnpolyh p n0" and nq: "isnpolyh q n1" shows "(∀bs. ⦇p⦈⇩_{p}⇗^{bs⇖}= (⦇q⦈⇩_{p}⇗^{bs⇖}:: 'a::{field_char_0,field,power})) ⟷ p = q" proof auto assume H: "∀bs. (⦇p⦈⇩_{p}⇗^{bs⇖}::'a) = ⦇q⦈⇩_{p}⇗^{bs⇖}" then have "∀bs.⦇p -⇩_{p}q⦈⇩_{p}⇗^{bs⇖}= (0::'a)" by simp then have "∀bs. wf_bs bs (p -⇩_{p}q) ⟶ ⦇p -⇩_{p}q⦈⇩_{p}⇗^{bs⇖}= (0::'a)" using wf_bs_polysub[where p=p and q=q] by auto with isnpolyh_zero_iff[OF polysub_normh[OF np nq]] polysub_0[OF np nq] show "p = q" by blast qed text ‹consequences of unicity on the algorithms for polynomial normalization› lemma polyadd_commute: assumes "SORT_CONSTRAINT('a::{field_char_0,field})" and np: "isnpolyh p n0" and nq: "isnpolyh q n1" shows "p +⇩_{p}q = q +⇩_{p}p" using isnpolyh_unique[OF polyadd_normh[OF np nq] polyadd_normh[OF nq np]] by simp lemma zero_normh: "isnpolyh 0⇩_{p}n" by simp lemma one_normh: "isnpolyh (1)⇩_{p}n" by simp lemma polyadd_0[simp]: assumes "SORT_CONSTRAINT('a::{field_char_0,field})" and np: "isnpolyh p n0" shows "p +⇩_{p}0⇩_{p}= p" and "0⇩_{p}+⇩_{p}p = p" using isnpolyh_unique[OF polyadd_normh[OF np zero_normh] np] isnpolyh_unique[OF polyadd_normh[OF zero_normh np] np] by simp_all lemma polymul_1[simp]: assumes "SORT_CONSTRAINT('a::{field_char_0,field})" and np: "isnpolyh p n0" shows "p *⇩_{p}(1)⇩_{p}= p" and "(1)⇩_{p}*⇩_{p}p = p" using isnpolyh_unique[OF polymul_normh[OF np one_normh] np] isnpolyh_unique[OF polymul_normh[OF one_normh np] np] by simp_all lemma polymul_0[simp]: assumes "SORT_CONSTRAINT('a::{field_char_0,field})" and np: "isnpolyh p n0" shows "p *⇩_{p}0⇩_{p}= 0⇩_{p}" and "0⇩_{p}*⇩_{p}p = 0⇩_{p}" using isnpolyh_unique[OF polymul_normh[OF np zero_normh] zero_normh] isnpolyh_unique[OF polymul_normh[OF zero_normh np] zero_normh] by simp_all lemma polymul_commute: assumes "SORT_CONSTRAINT('a::{field_char_0,field})" and np: "isnpolyh p n0" and nq: "isnpolyh q n1" shows "p *⇩_{p}q = q *⇩_{p}p" using isnpolyh_unique[OF polymul_normh[OF np nq] polymul_normh[OF nq np], where ?'a = "'a::{field_char_0,field, power}"] by simp declare polyneg_polyneg [simp] lemma isnpolyh_polynate_id [simp]: assumes "SORT_CONSTRAINT('a::{field_char_0,field})" and np: "isnpolyh p n0" shows "polynate p = p" using isnpolyh_unique[where ?'a= "'a::{field_char_0,field}", OF polynate_norm[of p, unfolded isnpoly_def] np] polynate[where ?'a = "'a::{field_char_0,field}"] by simp lemma polynate_idempotent[simp]: assumes "SORT_CONSTRAINT('a::{field_char_0,field})" shows "polynate (polynate p) = polynate p" using isnpolyh_polynate_id[OF polynate_norm[of p, unfolded isnpoly_def]] . lemma poly_nate_polypoly': "poly_nate bs p = polypoly' bs (polynate p)" unfolding poly_nate_def polypoly'_def .. lemma poly_nate_poly: "poly (poly_nate bs p) = (λx:: 'a ::{field_char_0,field}. ⦇p⦈⇩_{p}⇗^{x # bs⇖})" using polypoly'_poly[OF polynate_norm[unfolded isnpoly_def], symmetric, of bs p] unfolding poly_nate_polypoly' by auto subsection ‹heads, degrees and all that› lemma degree_eq_degreen0: "degree p = degreen p 0" by (induct p rule: degree.induct) simp_all lemma degree_polyneg: assumes "isnpolyh p n" shows "degree (polyneg p) = degree p" apply (induct p rule: polyneg.induct) using assms apply simp_all apply (case_tac na) apply auto done lemma degree_polyadd: assumes np: "isnpolyh p n0" and nq: "isnpolyh q n1" shows "degree (p +⇩_{p}q) ≤ max (degree p) (degree q)" using degreen_polyadd[OF np nq, where m= "0"] degree_eq_degreen0 by simp lemma degree_polysub: assumes np: "isnpolyh p n0" and nq: "isnpolyh q n1" shows "degree (p -⇩_{p}q) ≤ max (degree p) (degree q)" proof- from nq have nq': "isnpolyh (~⇩_{p}q) n1" using polyneg_normh by simp from degree_polyadd[OF np nq'] show ?thesis by (simp add: polysub_def degree_polyneg[OF nq]) qed lemma degree_polysub_samehead: assumes "SORT_CONSTRAINT('a::{field_char_0,field})" and np: "isnpolyh p n0" and nq: "isnpolyh q n1" and h: "head p = head q" and d: "degree p = degree q" shows "degree (p -⇩_{p}q) < degree p ∨ (p -⇩_{p}q = 0⇩_{p})" unfolding polysub_def split_def fst_conv snd_conv using np nq h d proof (induct p q rule: polyadd.induct) case (1 c c') then show ?case by (simp add: Nsub_def Nsub0[simplified Nsub_def]) next case (2 c c' n' p') from 2 have "degree (C c) = degree (CN c' n' p')" by simp then have nz: "n' > 0" by (cases n') auto then have "head (CN c' n' p') = CN c' n' p'" by (cases n') auto with 2 show ?case by simp next case (3 c n p c') then have "degree (C c') = degree (CN c n p)" by simp then have nz: "n > 0" by (cases n) auto then have "head (CN c n p) = CN c n p" by (cases n) auto with 3 show ?case by simp next case (4 c n p c' n' p') then have H: "isnpolyh (CN c n p) n0" "isnpolyh (CN c' n' p') n1" "head (CN c n p) = head (CN c' n' p')" "degree (CN c n p) = degree (CN c' n' p')" by simp_all then have degc: "degree c = 0" and degc': "degree c' = 0" by simp_all then have degnc: "degree (~⇩_{p}c) = 0" and degnc': "degree (~⇩_{p}c') = 0" using H(1-2) degree_polyneg by auto from H have cnh: "isnpolyh c (Suc n)" and c'nh: "isnpolyh c' (Suc n')" by simp_all from degree_polysub[OF cnh c'nh, simplified polysub_def] degc degc' have degcmc': "degree (c +⇩_{p}~⇩_{p}c') = 0" by simp from H have pnh: "isnpolyh p n" and p'nh: "isnpolyh p' n'" by auto have "n = n' ∨ n < n' ∨ n > n'" by arith moreover { assume nn': "n = n'" have "n = 0 ∨ n > 0" by arith moreover { assume nz: "n = 0" then have ?case using 4 nn' by (auto simp add: Let_def degcmc') } moreover { assume nz: "n > 0" with nn' H(3) have cc': "c = c'" and pp': "p = p'" by (cases n, auto)+ then have ?case using polysub_same_0[OF p'nh, simplified polysub_def split_def fst_conv snd_conv] using polysub_same_0[OF c'nh, simplified polysub_def] using nn' 4 by (simp add: Let_def) } ultimately have ?case by blast } moreover { assume nn': "n < n'" then have n'p: "n' > 0" by simp then have headcnp':"head (CN c' n' p') = CN c' n' p'" by (cases n') simp_all have degcnp': "degree (CN c' n' p') = 0" and degcnpeq: "degree (CN c n p) = degree (CN c' n' p')" using 4 nn' by (cases n', simp_all) then have "n > 0" by (cases n) simp_all then have headcnp: "head (CN c n p) = CN c n p" by (cases n) auto from H(3) headcnp headcnp' nn' have ?case by auto } moreover { assume nn': "n > n'" then have np: "n > 0" by simp then have headcnp:"head (CN c n p) = CN c n p" by (cases n) simp_all from 4 have degcnpeq: "degree (CN c' n' p') = degree (CN c n p)" by simp from np have degcnp: "degree (CN c n p) = 0" by (cases n) simp_all with degcnpeq have "n' > 0" by (cases n') simp_all then have headcnp': "head (CN c' n' p') = CN c' n' p'" by (cases n') auto from H(3) headcnp headcnp' nn' have ?case by auto } ultimately show ?case by blast qed auto lemma shift1_head : "isnpolyh p n0 ⟹ head (shift1 p) = head p" by (induct p arbitrary: n0 rule: head.induct) (simp_all add: shift1_def) lemma funpow_shift1_head: "isnpolyh p n0 ⟹ p≠ 0⇩_{p}⟹ head (funpow k shift1 p) = head p" proof (induct k arbitrary: n0 p) case 0 then show ?case by auto next case (Suc k n0 p) then have "isnpolyh (shift1 p) 0" by (simp add: shift1_isnpolyh) with Suc have "head (funpow k shift1 (shift1 p)) = head (shift1 p)" and "head (shift1 p) = head p" by (simp_all add: shift1_head) then show ?case by (simp add: funpow_swap1) qed lemma shift1_degree: "degree (shift1 p) = 1 + degree p" by (simp add: shift1_def) lemma funpow_shift1_degree: "degree (funpow k shift1 p) = k + degree p " by (induct k arbitrary: p) (auto simp add: shift1_degree) lemma funpow_shift1_nz: "p ≠ 0⇩_{p}⟹ funpow n shift1 p ≠ 0⇩_{p}" by (induct n arbitrary: p) simp_all lemma head_isnpolyh_Suc[simp]: "isnpolyh p (Suc n) ⟹ head p = p" by (induct p arbitrary: n rule: degree.induct) auto lemma headn_0[simp]: "isnpolyh p n ⟹ m < n ⟹ headn p m = p" by (induct p arbitrary: n rule: degreen.induct) auto lemma head_isnpolyh_Suc': "n > 0 ⟹ isnpolyh p n ⟹ head p = p" by (induct p arbitrary: n rule: degree.induct) auto lemma head_head[simp]: "isnpolyh p n0 ⟹ head (head p) = head p" by (induct p rule: head.induct) auto lemma polyadd_eq_const_degree: "isnpolyh p n0 ⟹ isnpolyh q n1 ⟹ polyadd p q = C c ⟹ degree p = degree q" using polyadd_eq_const_degreen degree_eq_degreen0 by simp lemma polyadd_head: assumes np: "isnpolyh p n0" and nq: "isnpolyh q n1" and deg: "degree p ≠ degree q" shows "head (p +⇩_{p}q) = (if degree p < degree q then head q else head p)" using np nq deg apply (induct p q arbitrary: n0 n1 rule: polyadd.induct) apply simp_all apply (case_tac n', simp, simp) apply (case_tac n, simp, simp) apply (case_tac n, case_tac n', simp add: Let_def) apply (auto simp add: polyadd_eq_const_degree)[2] apply (metis head_nz) apply (metis head_nz) apply (metis degree.simps(9) gr0_conv_Suc head.simps(1) less_Suc0 not_less_eq) done lemma polymul_head_polyeq: assumes "SORT_CONSTRAINT('a::{field_char_0,field})" shows "isnpolyh p n0 ⟹ isnpolyh q n1 ⟹ p ≠ 0⇩_{p}⟹ q ≠ 0⇩_{p}⟹ head (p *⇩_{p}q) = head p *⇩_{p}head q" proof (induct p q arbitrary: n0 n1 rule: polymul.induct) case (2 c c' n' p' n0 n1) then have "isnpolyh (head (CN c' n' p')) n1" "isnormNum c" by (simp_all add: head_isnpolyh) then show ?case using 2 by (cases n') auto next case (3 c n p c' n0 n1) then have "isnpolyh (head (CN c n p)) n0" "isnormNum c'" by (simp_all add: head_isnpolyh) then show ?case using 3 by (cases n) auto next case (4 c n p c' n' p' n0 n1) then have norm: "isnpolyh p n" "isnpolyh c (Suc n)" "isnpolyh p' n'" "isnpolyh c' (Suc n')" "isnpolyh (CN c n p) n" "isnpolyh (CN c' n' p') n'" by simp_all have "n < n' ∨ n' < n ∨ n = n'" by arith moreover { assume nn': "n < n'" then have ?case using norm "4.hyps"(2)[OF norm(1,6)] "4.hyps"(1)[OF norm(2,6)] apply simp apply (cases n) apply simp apply (cases n') apply simp_all done } moreover { assume nn': "n'< n" then have ?case using norm "4.hyps"(6) [OF norm(5,3)] "4.hyps"(5)[OF norm(5,4)] apply simp apply (cases n') apply simp apply (cases n) apply auto done } moreover { assume nn': "n' = n" from nn' polymul_normh[OF norm(5,4)] have ncnpc':"isnpolyh (CN c n p *⇩_{p}c') n" by (simp add: min_def) from nn' polymul_normh[OF norm(5,3)] norm have ncnpp':"isnpolyh (CN c n p *⇩_{p}p') n" by simp from nn' ncnpp' polymul_eq0_iff[OF norm(5,3)] norm(6) have ncnpp0':"isnpolyh (CN 0⇩_{p}n (CN c n p *⇩_{p}p')) n" by simp from polyadd_normh[OF ncnpc' ncnpp0'] have nth: "isnpolyh ((CN c n p *⇩_{p}c') +⇩_{p}(CN 0⇩_{p}n (CN c n p *⇩_{p}p'))) n" by (simp add: min_def) { assume np: "n > 0" with nn' head_isnpolyh_Suc'[OF np nth] head_isnpolyh_Suc'[OF np norm(5)] head_isnpolyh_Suc'[OF np norm(6)[simplified nn']] have ?case by simp } moreover { assume nz: "n = 0" from polymul_degreen[OF norm(5,4), where m="0"] polymul_degreen[OF norm(5,3), where m="0"] nn' nz degree_eq_degreen0 norm(5,6) degree_npolyhCN[OF norm(6)] have dth: "degree (CN c 0 p *⇩_{p}c') < degree (CN 0⇩_{p}0 (CN c 0 p *⇩_{p}p'))" by simp then have dth': "degree (CN c 0 p *⇩_{p}c') ≠ degree (CN 0⇩_{p}0 (CN c 0 p *⇩_{p}p'))" by simp from polyadd_head[OF ncnpc'[simplified nz] ncnpp0'[simplified nz] dth'] dth have ?case using norm "4.hyps"(6)[OF norm(5,3)] "4.hyps"(5)[OF norm(5,4)] nn' nz by simp } ultimately have ?case by (cases n) auto } ultimately show ?case by blast qed simp_all lemma degree_coefficients: "degree p = length (coefficients p) - 1" by (induct p rule: degree.induct) auto lemma degree_head[simp]: "degree (head p) = 0" by (induct p rule: head.induct) auto lemma degree_CN: "isnpolyh p n ⟹ degree (CN c n p) ≤ 1 + degree p" by (cases n) simp_all lemma degree_CN': "isnpolyh p n ⟹ degree (CN c n p) ≥ degree p" by (cases n) simp_all lemma polyadd_different_degree: "isnpolyh p n0 ⟹ isnpolyh q n1 ⟹ degree p ≠ degree q ⟹ degree (polyadd p q) = max (degree p) (degree q)" using polyadd_different_degreen degree_eq_degreen0 by simp lemma degreen_polyneg: "isnpolyh p n0 ⟹ degreen (~⇩_{p}p) m = degreen p m" by (induct p arbitrary: n0 rule: polyneg.induct) auto lemma degree_polymul: assumes "SORT_CONSTRAINT('a::{field_char_0,field})" and np: "isnpolyh p n0" and nq: "isnpolyh q n1" shows "degree (p *⇩_{p}q) ≤ degree p + degree q" using polymul_degreen[OF np nq, where m="0"] degree_eq_degreen0 by simp lemma polyneg_degree: "isnpolyh p n ⟹ degree (polyneg p) = degree p" by (induct p arbitrary: n rule: degree.induct) auto lemma polyneg_head: "isnpolyh p n ⟹ head (polyneg p) = polyneg (head p)" by (induct p arbitrary: n rule: degree.induct) auto subsection ‹Correctness of polynomial pseudo division› lemma polydivide_aux_properties: assumes "SORT_CONSTRAINT('a::{field_char_0,field})" and np: "isnpolyh p n0" and ns: "isnpolyh s n1" and ap: "head p = a" and ndp: "degree p = n" and pnz: "p ≠ 0⇩_{p}" shows "polydivide_aux a n p k s = (k', r) ⟶ k' ≥ k ∧ (degree r = 0 ∨ degree r < degree p) ∧ (∃nr. isnpolyh r nr) ∧ (∃q n1. isnpolyh q n1 ∧ (polypow (k' - k) a) *⇩_{p}s = p *⇩_{p}q +⇩_{p}r)" using ns proof (induct "degree s" arbitrary: s k k' r n1 rule: less_induct) case less let ?qths = "∃q n1. isnpolyh q n1 ∧ (a ^⇩_{p}(k' - k) *⇩_{p}s = p *⇩_{p}q +⇩_{p}r)" let ?ths = "polydivide_aux a n p k s = (k', r) ⟶ k ≤ k' ∧ (degree r = 0 ∨ degree r < degree p) ∧ (∃nr. isnpolyh r nr) ∧ ?qths" let ?b = "head s" let ?p' = "funpow (degree s - n) shift1 p" let ?xdn = "funpow (degree s - n) shift1 (1)⇩_{p}" let ?akk' = "a ^⇩_{p}(k' - k)" note ns = ‹isnpolyh s n1› from np have np0: "isnpolyh p 0" using isnpolyh_mono[where n="n0" and n'="0" and p="p"] by simp have np': "isnpolyh ?p' 0" using funpow_shift1_isnpoly[OF np0[simplified isnpoly_def[symmetric]] pnz, where n="degree s - n"] isnpoly_def by simp have headp': "head ?p' = head p" using funpow_shift1_head[OF np pnz] by simp from funpow_shift1_isnpoly[where p="(1)⇩_{p}"] have nxdn: "isnpolyh ?xdn 0" by (simp add: isnpoly_def) from polypow_normh [OF head_isnpolyh[OF np0], where k="k' - k"] ap have nakk':"isnpolyh ?akk' 0" by blast { assume sz: "s = 0⇩_{p}" then have ?ths using np polydivide_aux.simps apply clarsimp apply (rule exI[where x="0⇩_{p}"]) apply simp done } moreover { assume sz: "s ≠ 0⇩_{p}" { assume dn: "degree s < n" then have "?ths" using ns ndp np polydivide_aux.simps apply auto apply (rule exI[where x="0⇩_{p}"]) apply simp done } moreover { assume dn': "¬ degree s < n" then have dn: "degree s ≥ n" by arith have degsp': "degree s = degree ?p'" using dn ndp funpow_shift1_degree[where k = "degree s - n" and p="p"] by simp { assume ba: "?b = a" then have headsp': "head s = head ?p'" using ap headp' by simp have nr: "isnpolyh (s -⇩_{p}?p') 0" using polysub_normh[OF ns np'] by simp from degree_polysub_samehead[OF ns np' headsp' degsp'] have "degree (s -⇩_{p}?p') < degree s ∨ s -⇩_{p}?p' = 0⇩_{p}" by simp moreover { assume deglt:"degree (s -⇩_{p}?p') < degree s" from polydivide_aux.simps sz dn' ba have eq: "polydivide_aux a n p k s = polydivide_aux a n p k (s -⇩_{p}?p')" by (simp add: Let_def) { assume h1: "polydivide_aux a n p k s = (k', r)" from less(1)[OF deglt nr, of k k' r] trans[OF eq[symmetric] h1] have kk': "k ≤ k'" and nr: "∃nr. isnpolyh r nr" and dr: "degree r = 0 ∨ degree r < degree p" and q1: "∃q nq. isnpolyh q nq ∧ a ^⇩_{p}k' - k *⇩_{p}(s -⇩_{p}?p') = p *⇩_{p}q +⇩_{p}r" by auto from q1 obtain q n1 where nq: "isnpolyh q n1" and asp: "a^⇩_{p}(k' - k) *⇩_{p}(s -⇩_{p}?p') = p *⇩_{p}q +⇩_{p}r" by blast from nr obtain nr where nr': "isnpolyh r nr" by blast from polymul_normh[OF nakk' ns] have nakks': "isnpolyh (a ^⇩_{p}(k' - k) *⇩_{p}s) 0" by simp from polyadd_normh[OF polymul_normh[OF nakk' nxdn] nq] have nq': "isnpolyh (?akk' *⇩_{p}?xdn +⇩_{p}q) 0" by simp from polyadd_normh[OF polymul_normh[OF np polyadd_normh[OF polymul_normh[OF nakk' nxdn] nq]] nr'] have nqr': "isnpolyh (p *⇩_{p}(?akk' *⇩_{p}?xdn +⇩_{p}q) +⇩_{p}r) 0" by simp from asp have "∀bs :: 'a::{field_char_0,field} list. Ipoly bs (a^⇩_{p}(k' - k) *⇩_{p}(s -⇩_{p}?p')) = Ipoly bs (p *⇩_{p}q +⇩_{p}r)" by simp then have "∀bs :: 'a::{field_char_0,field} list. Ipoly bs (a^⇩_{p}(k' - k)*⇩_{p}s) = Ipoly bs (a^⇩_{p}(k' - k)) * Ipoly bs ?p' + Ipoly bs p * Ipoly bs q + Ipoly bs r" by (simp add: field_simps) then have "∀bs :: 'a::{field_char_0,field} list. Ipoly bs (a ^⇩_{p}(k' - k) *⇩_{p}s) = Ipoly bs (a^⇩_{p}(k' - k)) * Ipoly bs (funpow (degree s - n) shift1 (1)⇩_{p}*⇩_{p}p) + Ipoly bs p * Ipoly bs q + Ipoly bs r" by (auto simp only: funpow_shift1_1) then have "∀bs:: 'a::{field_char_0,field} list. Ipoly bs (a ^⇩_{p}(k' - k) *⇩_{p}s) = Ipoly bs p * (Ipoly bs (a^⇩_{p}(k' - k)) * Ipoly bs (funpow (degree s - n) shift1 (1)⇩_{p}) + Ipoly bs q) + Ipoly bs r" by (simp add: field_simps) then have "∀bs:: 'a::{field_char_0,field} list. Ipoly bs (a ^⇩_{p}(k' - k) *⇩_{p}s) = Ipoly bs (p *⇩_{p}((a^⇩_{p}(k' - k)) *⇩_{p}(funpow (degree s - n) shift1 (1)⇩_{p}) +⇩_{p}q) +⇩_{p}r)" by simp with isnpolyh_unique[OF nakks' nqr'] have "a ^⇩_{p}(k' - k) *⇩_{p}s = p *⇩_{p}((a^⇩_{p}(k' - k)) *⇩_{p}(funpow (degree s - n) shift1 (1)⇩_{p}) +⇩_{p}q) +⇩_{p}r" by blast then have ?qths using nq' apply (rule_tac x="(a^⇩_{p}(k' - k)) *⇩_{p}(funpow (degree s - n) shift1 (1)⇩_{p}) +⇩_{p}q" in exI) apply (rule_tac x="0" in exI) apply simp done with kk' nr dr have "k ≤ k' ∧ (degree r = 0 ∨ degree r < degree p) ∧ (∃nr. isnpolyh r nr) ∧ ?qths" by blast } then have ?ths by blast } moreover { assume spz:"s -⇩_{p}?p' = 0⇩_{p}" from spz isnpolyh_unique[OF polysub_normh[OF ns np'], where q="0⇩_{p}", symmetric, where ?'a = "'a::{field_char_0,field}"] have "∀bs:: 'a::{field_char_0,field} list. Ipoly bs s = Ipoly bs ?p'" by simp then have "∀bs:: 'a::{field_char_0,field} list. Ipoly bs s = Ipoly bs (?xdn *⇩_{p}p)" using np nxdn apply simp apply (simp only: funpow_shift1_1) apply simp done then have sp': "s = ?xdn *⇩_{p}p" using isnpolyh_unique[OF ns polymul_normh[OF nxdn np]] by blast { assume h1: "polydivide_aux a n p k s = (k', r)" from polydivide_aux.simps sz dn' ba have eq: "polydivide_aux a n p k s = polydivide_aux a n p k (s -⇩_{p}?p')" by (simp add: Let_def) also have "… = (k,0⇩_{p})" using polydivide_aux.simps spz by simp finally have "(k', r) = (k, 0⇩_{p})" using h1 by simp with sp'[symmetric] ns np nxdn polyadd_0(1)[OF polymul_normh[OF np nxdn]] polyadd_0(2)[OF polymul_normh[OF np nxdn]] have ?ths apply auto apply (rule exI[where x="?xdn"]) apply (auto simp add: polymul_commute[of p]) done } } ultimately have ?ths by blast } moreover { assume ba: "?b ≠ a" from polysub_normh[OF polymul_normh[OF head_isnpolyh[OF np0, simplified ap] ns] polymul_normh[OF head_isnpolyh[OF ns] np']] have nth: "isnpolyh ((a *⇩_{p}s) -⇩_{p}(?b *⇩_{p}?p')) 0" by (simp add: min_def) have nzths: "a *⇩_{p}s ≠ 0⇩_{p}" "?b *⇩_{p}?p' ≠ 0⇩_{p}" using polymul_eq0_iff[OF head_isnpolyh[OF np0, simplified ap] ns] polymul_eq0_iff[OF head_isnpolyh[OF ns] np']head_nz[OF np0] ap pnz sz head_nz[OF ns] funpow_shift1_nz[OF pnz] by simp_all from polymul_head_polyeq[OF head_isnpolyh[OF np] ns] head_nz[OF np] sz ap head_head[OF np] pnz polymul_head_polyeq[OF head_isnpolyh[OF ns] np'] head_nz [OF ns] sz funpow_shift1_nz[OF pnz, where n="degree s - n"] have hdth: "head (a *⇩_{p}s) = head (?b *⇩_{p}?p')" using head_head[OF ns] funpow_shift1_head[OF np pnz] polymul_commute[OF head_isnpolyh[OF np] head_isnpolyh[OF ns]] by (simp add: ap) from polymul_degreen[OF head_isnpolyh[OF np] ns, where m="0"] head_nz[OF np] pnz sz ap[symmetric] funpow_shift1_nz[OF pnz, where n="degree s - n"] polymul_degreen[OF head_isnpolyh[OF ns] np', where m="0"] head_nz[OF ns] ndp dn have degth: "degree (a *⇩_{p}s) = degree (?b *⇩_{p}?p')" by (simp add: degree_eq_degreen0[symmetric] funpow_shift1_degree) { assume dth: "degree ((a *⇩_{p}s) -⇩_{p}(?b *⇩_{p}?p')) < degree s" from polysub_normh[OF polymul_normh[OF head_isnpolyh[OF np] ns] polymul_normh[OF head_isnpolyh[OF ns]np']] ap have nasbp': "isnpolyh ((a *⇩_{p}s) -⇩_{p}(?b *⇩_{p}?p')) 0" by simp { assume h1:"polydivide_aux a n p k s = (k', r)" from h1 polydivide_aux.simps sz dn' ba have eq:"polydivide_aux a n p (Suc k) ((a *⇩_{p}s) -⇩_{p}(?b *⇩_{p}?p')) = (k',r)" by (simp add: Let_def) with less(1)[OF dth nasbp', of "Suc k" k' r] obtain q nq nr where kk': "Suc k ≤ k'" and nr: "isnpolyh r nr" and nq: "isnpolyh q nq" and dr: "degree r = 0 ∨ degree r < degree p" and qr: "a ^⇩_{p}(k' - Suc k) *⇩_{p}((a *⇩_{p}s) -⇩_{p}(?b *⇩_{p}?p')) = p *⇩_{p}q +⇩_{p}r" by auto from kk' have kk'': "Suc (k' - Suc k) = k' - k" by arith { fix bs :: "'a::{field_char_0,field} list" from qr isnpolyh_unique[OF polypow_normh[OF head_isnpolyh[OF np], where k="k' - Suc k", simplified ap] nasbp', symmetric] have "Ipoly bs (a ^⇩_{p}(k' - Suc k) *⇩_{p}((a *⇩_{p}s) -⇩_{p}(?b *⇩_{p}?p'))) = Ipoly bs (p *⇩_{p}q +⇩_{p}r)" by simp then have "Ipoly bs a ^ (Suc (k' - Suc k)) * Ipoly bs s = Ipoly bs p * Ipoly bs q + Ipoly bs a ^ (k' - Suc k) * Ipoly bs ?b * Ipoly bs ?p' + Ipoly bs r" by (simp add: field_simps) then have "Ipoly bs a ^ (k' - k) * Ipoly bs s = Ipoly bs p * Ipoly bs q + Ipoly bs a ^ (k' - Suc k) * Ipoly bs ?b * Ipoly bs ?xdn * Ipoly bs p + Ipoly bs r" by (simp add: kk'' funpow_shift1_1[where n="degree s - n" and p="p"]) then have "Ipoly bs (a ^⇩_{p}(k' - k) *⇩_{p}s) = Ipoly bs p * (Ipoly bs q + Ipoly bs a ^ (k' - Suc k) * Ipoly bs ?b * Ipoly bs ?xdn) + Ipoly bs r" by (simp add: field_simps) } then have ieq:"∀bs :: 'a::{field_char_0,field} list. Ipoly bs (a ^⇩_{p}(k' - k) *⇩_{p}s) = Ipoly bs (p *⇩_{p}(q +⇩_{p}(a ^⇩_{p}(k' - Suc k) *⇩_{p}?b *⇩_{p}?xdn)) +⇩_{p}r)" by auto let ?q = "q +⇩_{p}(a ^⇩_{p}(k' - Suc k) *⇩_{p}?b *⇩_{p}?xdn)" from polyadd_normh[OF nq polymul_normh[OF polymul_normh[OF polypow_normh[OF head_isnpolyh[OF np], where k="k' - Suc k"] head_isnpolyh[OF ns], simplified ap] nxdn]] have nqw: "isnpolyh ?q 0" by simp from ieq isnpolyh_unique[OF polymul_normh[OF polypow_normh[OF head_isnpolyh[OF np], where k="k' - k"] ns, simplified ap] polyadd_normh[OF polymul_normh[OF np nqw] nr]] have asth: "(a ^⇩_{p}(k' - k) *⇩_{p}s) = p *⇩_{p}(q +⇩_{p}(a ^⇩_{p}(k' - Suc k) *⇩_{p}?b *⇩_{p}?xdn)) +⇩_{p}r" by blast from dr kk' nr h1 asth nqw have ?ths apply simp apply (rule conjI) apply (rule exI[where x="nr"], simp) apply (rule exI[where x="(q +⇩_{p}(a ^⇩_{p}(k' - Suc k) *⇩_{p}?b *⇩_{p}?xdn))"], simp) apply (rule exI[where x="0"], simp) done } then have ?ths by blast } moreover { assume spz: "a *⇩_{p}s -⇩_{p}(?b *⇩_{p}?p') = 0⇩_{p}" { fix bs :: "'a::{field_char_0,field} list" from isnpolyh_unique[OF nth, where ?'a="'a" and q="0⇩_{p}",simplified,symmetric] spz have "Ipoly bs (a*⇩_{p}s) = Ipoly bs ?b * Ipoly bs ?p'" by simp then have "Ipoly bs (a*⇩_{p}s) = Ipoly bs (?b *⇩_{p}?xdn) * Ipoly bs p" by (simp add: funpow_shift1_1[where n="degree s - n" and p="p"]) then have "Ipoly bs (a*⇩_{p}s) = Ipoly bs (p *⇩_{p}(?b *⇩_{p}?xdn))" by simp } then have hth: "∀bs :: 'a::{field_char_0,field} list. Ipoly bs (a *⇩_{p}s) = Ipoly bs (p *⇩_{p}(?b *⇩_{p}?xdn))" .. from hth have asq: "a *⇩_{p}s = p *⇩_{p}(?b *⇩_{p}?xdn)" using isnpolyh_unique[where ?'a = "'a::{field_char_0,field}", OF polymul_normh[OF head_isnpolyh[OF np] ns] polymul_normh[OF np polymul_normh[OF head_isnpolyh[OF ns] nxdn]], simplified ap] by simp { assume h1: "polydivide_aux a n p k s = (k', r)" from h1 sz ba dn' spz polydivide_aux.simps polydivide_aux.simps have "(k', r) = (Suc k, 0⇩_{p})" by (simp add: Let_def) with h1 np head_isnpolyh[OF np, simplified ap] ns polymul_normh[OF head_isnpolyh[OF ns] nxdn] polymul_normh[OF np polymul_normh[OF head_isnpolyh[OF ns] nxdn]] asq have ?ths apply (clarsimp simp add: Let_def) apply (rule exI[where x="?b *⇩_{p}?xdn"]) apply simp apply (rule exI[where x="0"], simp) done } then have ?ths by blast } ultimately have ?ths using degree_polysub_samehead[OF polymul_normh[OF head_isnpolyh[OF np0, simplified ap] ns] polymul_normh[OF head_isnpolyh[OF ns] np'] hdth degth] polymul_degreen[OF head_isnpolyh[OF np] ns, where m="0"] head_nz[OF np] pnz sz ap[symmetric] by (auto simp add: degree_eq_degreen0[symmetric]) } ultimately have ?ths by blast } ultimately have ?ths by blast } ultimately show ?ths by blast qed lemma polydivide_properties: assumes "SORT_CONSTRAINT('a::{field_char_0,field})" and np: "isnpolyh p n0" and ns: "isnpolyh s n1" and pnz: "p ≠ 0⇩_{p}" shows "∃k r. polydivide s p = (k, r) ∧ (∃nr. isnpolyh r nr) ∧ (degree r = 0 ∨ degree r < degree p) ∧ (∃q n1. isnpolyh q n1 ∧ polypow k (head p) *⇩_{p}s = p *⇩_{p}q +⇩_{p}r)" proof - have trv: "head p = head p" "degree p = degree p" by simp_all from polydivide_def[where s="s" and p="p"] have ex: "∃ k r. polydivide s p = (k,r)" by auto then obtain k r where kr: "polydivide s p = (k,r)" by blast from trans[OF polydivide_def[where s="s"and p="p", symmetric] kr] polydivide_aux_properties[OF np ns trv pnz, where k="0" and k'="k" and r="r"] have "(degree r = 0 ∨ degree r < degree p) ∧ (∃nr. isnpolyh r nr) ∧ (∃q n1. isnpolyh q n1 ∧ head p ^⇩_{p}k - 0 *⇩_{p}s = p *⇩_{p}q +⇩_{p}r)" by blast with kr show ?thesis apply - apply (rule exI[where x="k"]) apply (rule exI[where x="r"]) apply simp done qed subsection ‹More about polypoly and pnormal etc› definition "isnonconstant p ⟷ ¬ isconstant p" lemma isnonconstant_pnormal_iff: assumes "isnonconstant p" shows "pnormal (polypoly bs p) ⟷ Ipoly bs (head p) ≠ 0" proof let ?p = "polypoly bs p" assume H: "pnormal ?p" have csz: "coefficients p ≠ []" using assms by (cases p) auto from coefficients_head[of p] last_map[OF csz, of "Ipoly bs"] pnormal_last_nonzero[OF H] show "Ipoly bs (head p) ≠ 0" by (simp add: polypoly_def) next assume h: "⦇head p⦈⇩_{p}⇗^{bs⇖}≠ 0" let ?p = "polypoly bs p" have csz: "coefficients p ≠ []" using assms by (cases p) auto then have pz: "?p ≠ []" by (simp add: polypoly_def) then have lg: "length ?p > 0" by simp from h coefficients_head[of p] last_map[OF csz, of "Ipoly bs"] have lz: "last ?p ≠ 0" by (simp add: polypoly_def) from pnormal_last_length[OF lg lz] show "pnormal ?p" . qed lemma isnonconstant_coefficients_length: "isnonconstant p ⟹ length (coefficients p) > 1" unfolding isnonconstant_def apply (cases p) apply simp_all apply (rename_tac nat a, case_tac nat) apply auto done lemma isnonconstant_nonconstant: assumes "isnonconstant p" shows "nonconstant (polypoly bs p) ⟷ Ipoly bs (head p) ≠ 0" proof let ?p = "polypoly bs p" assume nc: "nonconstant ?p" from isnonconstant_pnormal_iff[OF assms, of bs] nc show "⦇head p⦈⇩_{p}⇗^{bs⇖}≠ 0" unfolding nonconstant_def by blast next let ?p = "polypoly bs p" assume h: "⦇head p⦈⇩_{p}⇗^{bs⇖}≠ 0" from isnonconstant_pnormal_iff[OF assms, of bs] h have pn: "pnormal ?p" by blast { fix x assume H: "?p = [x]" from H have "length (coefficients p) = 1" unfolding polypoly_def by auto with isnonconstant_coefficients_length[OF assms] have False by arith } then show "nonconstant ?p" using pn unfolding nonconstant_def by blast qed lemma pnormal_length: "p ≠ [] ⟹ pnormal p ⟷ length (pnormalize p) = length p" apply (induct p) apply (simp_all add: pnormal_def) apply (case_tac "p = []") apply simp_all done lemma degree_degree: assumes "isnonconstant p" shows "degree p = Polynomial_List.degree (polypoly bs p) ⟷ ⦇head p⦈⇩_{p}⇗^{bs⇖}≠ 0" proof let ?p = "polypoly bs p" assume H: "degree p = Polynomial_List.degree ?p" from isnonconstant_coefficients_length[OF assms] have pz: "?p ≠ []" unfolding polypoly_def by auto from H degree_coefficients[of p] isnonconstant_coefficients_length[OF assms] have lg: "length (pnormalize ?p) = length ?p" unfolding Polynomial_List.degree_def polypoly_def by simp then have "pnormal ?p" using pnormal_length[OF pz] by blast with isnonconstant_pnormal_iff[OF assms] show "⦇head p⦈⇩_{p}⇗^{bs⇖}≠ 0" by blast next let ?p = "polypoly bs p" assume H: "⦇head p⦈⇩_{p}⇗^{bs⇖}≠ 0" with isnonconstant_pnormal_iff[OF assms] have "pnormal ?p" by blast with degree_coefficients[of p] isnonconstant_coefficients_length[OF assms] show "degree p = Polynomial_List.degree ?p" unfolding polypoly_def pnormal_def Polynomial_List.degree_def by auto qed section ‹Swaps ; Division by a certain variable› primrec swap :: "nat ⇒ nat ⇒ poly ⇒ poly" where "swap n m (C x) = C x" | "swap n m (Bound k) = Bound (if k = n then m else if k = m then n else k)" | "swap n m (Neg t) = Neg (swap n m t)" | "swap n m (Add s t) = Add (swap n m s) (swap n m t)" | "swap n m (Sub s t) = Sub (swap n m s) (swap n m t)" | "swap n m (Mul s t) = Mul (swap n m s) (swap n m t)" | "swap n m (Pw t k) = Pw (swap n m t) k" | "swap n m (CN c k p) = CN (swap n m c) (if k = n then m else if k=m then n else k) (swap n m p)" lemma swap: assumes "n < length bs" and "m < length bs" shows "Ipoly bs (swap n m t) = Ipoly ((bs[n:= bs!m])[m:= bs!n]) t" proof (induct t) case (Bound k) then show ?case using assms by simp next case (CN c k p) then show ?case using assms by simp qed simp_all lemma swap_swap_id [simp]: "swap n m (swap m n t) = t" by (induct t) simp_all lemma swap_commute: "swap n m p = swap m n p" by (induct p) simp_all lemma swap_same_id[simp]: "swap n n t = t" by (induct t) simp_all definition "swapnorm n m t = polynate (swap n m t)" lemma swapnorm: assumes nbs: "n < length bs" and mbs: "m < length bs" shows "((Ipoly bs (swapnorm n m t) :: 'a::{field_char_0,field})) = Ipoly ((bs[n:= bs!m])[m:= bs!n]) t" using swap[OF assms] swapnorm_def by simp lemma swapnorm_isnpoly [simp]: assumes "SORT_CONSTRAINT('a::{field_char_0,field})" shows "isnpoly (swapnorm n m p)" unfolding swapnorm_def by simp definition "polydivideby n s p = (let ss = swapnorm 0 n s; sp = swapnorm 0 n p; h = head sp; (k, r) = polydivide ss sp in (k, swapnorm 0 n h, swapnorm 0 n r))" lemma swap_nz [simp]: "swap n m p = 0⇩_{p}⟷ p = 0⇩_{p}" by (induct p) simp_all fun isweaknpoly :: "poly ⇒ bool" where "isweaknpoly (C c) = True" | "isweaknpoly (CN c n p) ⟷ isweaknpoly c ∧ isweaknpoly p" | "isweaknpoly p = False" lemma isnpolyh_isweaknpoly: "isnpolyh p n0 ⟹ isweaknpoly p" by (induct p arbitrary: n0) auto lemma swap_isweanpoly: "isweaknpoly p ⟹ isweaknpoly (swap n m p)" by (induct p) auto end