author | paulson <lp15@cam.ac.uk> |
Thu, 29 Sep 2016 11:24:36 +0100 | |
changeset 63954 | fb03766658f4 |
parent 63950 | cdc1e59aa513 |
child 64164 | 38c407446400 |
permissions | -rw-r--r-- |
63764 | 1 |
(* Title: HOL/Library/Polynomial_Factorial.thy |
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Author: Brian Huffman |
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Author: Clemens Ballarin |
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Author: Amine Chaieb |
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Author: Florian Haftmann |
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Author: Manuel Eberl |
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*) |
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theory Polynomial_Factorial |
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imports |
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Complex_Main |
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Polynomial algebra cleanup (tuned)
eberlm <eberlm@in.tum.de>
parents:
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diff
changeset
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"~~/src/HOL/Number_Theory/Euclidean_Algorithm" |
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"~~/src/HOL/Library/Polynomial" |
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"~~/src/HOL/Library/Normalized_Fraction" |
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begin |
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subsection \<open>Prelude\<close> |
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lemma prod_mset_mult: |
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"prod_mset (image_mset (\<lambda>x. f x * g x) A) = prod_mset (image_mset f A) * prod_mset (image_mset g A)" |
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by (induction A) (simp_all add: mult_ac) |
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lemma prod_mset_const: "prod_mset (image_mset (\<lambda>_. c) A) = c ^ size A" |
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by (induction A) (simp_all add: mult_ac) |
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lemma dvd_field_iff: "x dvd y \<longleftrightarrow> (x = 0 \<longrightarrow> y = (0::'a::field))" |
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proof safe |
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assume "x \<noteq> 0" |
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hence "y = x * (y / x)" by (simp add: field_simps) |
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thus "x dvd y" by (rule dvdI) |
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qed auto |
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lemma nat_descend_induct [case_names base descend]: |
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assumes "\<And>k::nat. k > n \<Longrightarrow> P k" |
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assumes "\<And>k::nat. k \<le> n \<Longrightarrow> (\<And>i. i > k \<Longrightarrow> P i) \<Longrightarrow> P k" |
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shows "P m" |
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using assms by induction_schema (force intro!: wf_measure[of "\<lambda>k. Suc n - k"])+ |
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lemma GreatestI_ex: "\<exists>k::nat. P k \<Longrightarrow> \<forall>y. P y \<longrightarrow> y < b \<Longrightarrow> P (GREATEST x. P x)" |
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by (metis GreatestI) |
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context field |
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begin |
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subclass idom_divide .. |
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end |
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context field |
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begin |
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definition normalize_field :: "'a \<Rightarrow> 'a" |
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where [simp]: "normalize_field x = (if x = 0 then 0 else 1)" |
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definition unit_factor_field :: "'a \<Rightarrow> 'a" |
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where [simp]: "unit_factor_field x = x" |
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definition euclidean_size_field :: "'a \<Rightarrow> nat" |
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where [simp]: "euclidean_size_field x = (if x = 0 then 0 else 1)" |
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definition mod_field :: "'a \<Rightarrow> 'a \<Rightarrow> 'a" |
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where [simp]: "mod_field x y = (if y = 0 then x else 0)" |
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end |
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instantiation real :: euclidean_ring |
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begin |
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definition [simp]: "normalize_real = (normalize_field :: real \<Rightarrow> _)" |
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definition [simp]: "unit_factor_real = (unit_factor_field :: real \<Rightarrow> _)" |
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definition [simp]: "euclidean_size_real = (euclidean_size_field :: real \<Rightarrow> _)" |
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definition [simp]: "modulo_real = (mod_field :: real \<Rightarrow> _)" |
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instance by standard (simp_all add: dvd_field_iff divide_simps) |
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end |
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instantiation real :: euclidean_ring_gcd |
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begin |
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definition gcd_real :: "real \<Rightarrow> real \<Rightarrow> real" where |
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"gcd_real = gcd_eucl" |
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definition lcm_real :: "real \<Rightarrow> real \<Rightarrow> real" where |
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"lcm_real = lcm_eucl" |
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definition Gcd_real :: "real set \<Rightarrow> real" where |
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"Gcd_real = Gcd_eucl" |
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definition Lcm_real :: "real set \<Rightarrow> real" where |
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"Lcm_real = Lcm_eucl" |
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instance by standard (simp_all add: gcd_real_def lcm_real_def Gcd_real_def Lcm_real_def) |
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end |
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instantiation rat :: euclidean_ring |
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begin |
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definition [simp]: "normalize_rat = (normalize_field :: rat \<Rightarrow> _)" |
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definition [simp]: "unit_factor_rat = (unit_factor_field :: rat \<Rightarrow> _)" |
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definition [simp]: "euclidean_size_rat = (euclidean_size_field :: rat \<Rightarrow> _)" |
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definition [simp]: "modulo_rat = (mod_field :: rat \<Rightarrow> _)" |
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instance by standard (simp_all add: dvd_field_iff divide_simps) |
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end |
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instantiation rat :: euclidean_ring_gcd |
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begin |
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definition gcd_rat :: "rat \<Rightarrow> rat \<Rightarrow> rat" where |
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"gcd_rat = gcd_eucl" |
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definition lcm_rat :: "rat \<Rightarrow> rat \<Rightarrow> rat" where |
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"lcm_rat = lcm_eucl" |
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definition Gcd_rat :: "rat set \<Rightarrow> rat" where |
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"Gcd_rat = Gcd_eucl" |
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definition Lcm_rat :: "rat set \<Rightarrow> rat" where |
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"Lcm_rat = Lcm_eucl" |
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instance by standard (simp_all add: gcd_rat_def lcm_rat_def Gcd_rat_def Lcm_rat_def) |
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end |
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instantiation complex :: euclidean_ring |
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begin |
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definition [simp]: "normalize_complex = (normalize_field :: complex \<Rightarrow> _)" |
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definition [simp]: "unit_factor_complex = (unit_factor_field :: complex \<Rightarrow> _)" |
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definition [simp]: "euclidean_size_complex = (euclidean_size_field :: complex \<Rightarrow> _)" |
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parents:
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definition [simp]: "modulo_complex = (mod_field :: complex \<Rightarrow> _)" |
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instance by standard (simp_all add: dvd_field_iff divide_simps) |
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end |
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instantiation complex :: euclidean_ring_gcd |
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begin |
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definition gcd_complex :: "complex \<Rightarrow> complex \<Rightarrow> complex" where |
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"gcd_complex = gcd_eucl" |
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definition lcm_complex :: "complex \<Rightarrow> complex \<Rightarrow> complex" where |
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"lcm_complex = lcm_eucl" |
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definition Gcd_complex :: "complex set \<Rightarrow> complex" where |
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"Gcd_complex = Gcd_eucl" |
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definition Lcm_complex :: "complex set \<Rightarrow> complex" where |
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"Lcm_complex = Lcm_eucl" |
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instance by standard (simp_all add: gcd_complex_def lcm_complex_def Gcd_complex_def Lcm_complex_def) |
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end |
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subsection \<open>Lifting elements into the field of fractions\<close> |
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definition to_fract :: "'a :: idom \<Rightarrow> 'a fract" where "to_fract x = Fract x 1" |
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lemma to_fract_0 [simp]: "to_fract 0 = 0" |
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by (simp add: to_fract_def eq_fract Zero_fract_def) |
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lemma to_fract_1 [simp]: "to_fract 1 = 1" |
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by (simp add: to_fract_def eq_fract One_fract_def) |
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lemma to_fract_add [simp]: "to_fract (x + y) = to_fract x + to_fract y" |
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by (simp add: to_fract_def) |
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lemma to_fract_diff [simp]: "to_fract (x - y) = to_fract x - to_fract y" |
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by (simp add: to_fract_def) |
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lemma to_fract_uminus [simp]: "to_fract (-x) = -to_fract x" |
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by (simp add: to_fract_def) |
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lemma to_fract_mult [simp]: "to_fract (x * y) = to_fract x * to_fract y" |
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by (simp add: to_fract_def) |
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lemma to_fract_eq_iff [simp]: "to_fract x = to_fract y \<longleftrightarrow> x = y" |
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by (simp add: to_fract_def eq_fract) |
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lemma to_fract_eq_0_iff [simp]: "to_fract x = 0 \<longleftrightarrow> x = 0" |
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by (simp add: to_fract_def Zero_fract_def eq_fract) |
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lemma snd_quot_of_fract_nonzero [simp]: "snd (quot_of_fract x) \<noteq> 0" |
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by transfer simp |
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lemma Fract_quot_of_fract [simp]: "Fract (fst (quot_of_fract x)) (snd (quot_of_fract x)) = x" |
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by transfer (simp del: fractrel_iff, subst fractrel_normalize_quot_left, simp) |
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lemma to_fract_quot_of_fract: |
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assumes "snd (quot_of_fract x) = 1" |
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shows "to_fract (fst (quot_of_fract x)) = x" |
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proof - |
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have "x = Fract (fst (quot_of_fract x)) (snd (quot_of_fract x))" by simp |
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also note assms |
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finally show ?thesis by (simp add: to_fract_def) |
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qed |
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lemma snd_quot_of_fract_Fract_whole: |
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assumes "y dvd x" |
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shows "snd (quot_of_fract (Fract x y)) = 1" |
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using assms by transfer (auto simp: normalize_quot_def Let_def gcd_proj2_if_dvd) |
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lemma Fract_conv_to_fract: "Fract a b = to_fract a / to_fract b" |
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by (simp add: to_fract_def) |
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lemma quot_of_fract_to_fract [simp]: "quot_of_fract (to_fract x) = (x, 1)" |
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unfolding to_fract_def by transfer (simp add: normalize_quot_def) |
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lemma fst_quot_of_fract_eq_0_iff [simp]: "fst (quot_of_fract x) = 0 \<longleftrightarrow> x = 0" |
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by transfer simp |
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lemma snd_quot_of_fract_to_fract [simp]: "snd (quot_of_fract (to_fract x)) = 1" |
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unfolding to_fract_def by (rule snd_quot_of_fract_Fract_whole) simp_all |
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lemma coprime_quot_of_fract: |
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"coprime (fst (quot_of_fract x)) (snd (quot_of_fract x))" |
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by transfer (simp add: coprime_normalize_quot) |
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lemma unit_factor_snd_quot_of_fract: "unit_factor (snd (quot_of_fract x)) = 1" |
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using quot_of_fract_in_normalized_fracts[of x] |
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by (simp add: normalized_fracts_def case_prod_unfold) |
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lemma unit_factor_1_imp_normalized: "unit_factor x = 1 \<Longrightarrow> normalize x = x" |
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by (subst (2) normalize_mult_unit_factor [symmetric, of x]) |
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(simp del: normalize_mult_unit_factor) |
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lemma normalize_snd_quot_of_fract: "normalize (snd (quot_of_fract x)) = snd (quot_of_fract x)" |
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by (intro unit_factor_1_imp_normalized unit_factor_snd_quot_of_fract) |
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subsection \<open>Mapping polynomials\<close> |
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definition map_poly |
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paulson <lp15@cam.ac.uk>
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:: "('a :: zero \<Rightarrow> 'b :: zero) \<Rightarrow> 'a poly \<Rightarrow> 'b poly" where |
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"map_poly f p = Poly (map f (coeffs p))" |
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lemma map_poly_0 [simp]: "map_poly f 0 = 0" |
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by (simp add: map_poly_def) |
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lemma map_poly_1: "map_poly f 1 = [:f 1:]" |
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by (simp add: map_poly_def) |
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lemma map_poly_1' [simp]: "f 1 = 1 \<Longrightarrow> map_poly f 1 = 1" |
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by (simp add: map_poly_def one_poly_def) |
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lemma coeff_map_poly: |
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assumes "f 0 = 0" |
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shows "coeff (map_poly f p) n = f (coeff p n)" |
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by (auto simp: map_poly_def nth_default_def coeffs_def assms |
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not_less Suc_le_eq coeff_eq_0 simp del: upt_Suc) |
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lemma coeffs_map_poly [code abstract]: |
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"coeffs (map_poly f p) = strip_while (op = 0) (map f (coeffs p))" |
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by (simp add: map_poly_def) |
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lemma set_coeffs_map_poly: |
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"(\<And>x. f x = 0 \<longleftrightarrow> x = 0) \<Longrightarrow> set (coeffs (map_poly f p)) = f ` set (coeffs p)" |
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by (cases "p = 0") (auto simp: coeffs_map_poly last_map last_coeffs_not_0) |
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lemma coeffs_map_poly': |
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assumes "(\<And>x. x \<noteq> 0 \<Longrightarrow> f x \<noteq> 0)" |
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shows "coeffs (map_poly f p) = map f (coeffs p)" |
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by (cases "p = 0") (auto simp: coeffs_map_poly last_map last_coeffs_not_0 assms |
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intro!: strip_while_not_last split: if_splits) |
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lemma degree_map_poly: |
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assumes "\<And>x. x \<noteq> 0 \<Longrightarrow> f x \<noteq> 0" |
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shows "degree (map_poly f p) = degree p" |
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by (simp add: degree_eq_length_coeffs coeffs_map_poly' assms) |
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lemma map_poly_eq_0_iff: |
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assumes "f 0 = 0" "\<And>x. x \<in> set (coeffs p) \<Longrightarrow> x \<noteq> 0 \<Longrightarrow> f x \<noteq> 0" |
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shows "map_poly f p = 0 \<longleftrightarrow> p = 0" |
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proof - |
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{ |
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fix n :: nat |
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have "coeff (map_poly f p) n = f (coeff p n)" by (simp add: coeff_map_poly assms) |
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also have "\<dots> = 0 \<longleftrightarrow> coeff p n = 0" |
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proof (cases "n < length (coeffs p)") |
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case True |
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hence "coeff p n \<in> set (coeffs p)" by (auto simp: coeffs_def simp del: upt_Suc) |
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with assms show "f (coeff p n) = 0 \<longleftrightarrow> coeff p n = 0" by auto |
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qed (auto simp: assms length_coeffs nth_default_coeffs_eq [symmetric] nth_default_def) |
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finally have "(coeff (map_poly f p) n = 0) = (coeff p n = 0)" . |
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} |
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thus ?thesis by (auto simp: poly_eq_iff) |
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qed |
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lemma map_poly_smult: |
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assumes "f 0 = 0""\<And>c x. f (c * x) = f c * f x" |
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shows "map_poly f (smult c p) = smult (f c) (map_poly f p)" |
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by (intro poly_eqI) (simp_all add: assms coeff_map_poly) |
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lemma map_poly_pCons: |
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assumes "f 0 = 0" |
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shows "map_poly f (pCons c p) = pCons (f c) (map_poly f p)" |
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by (intro poly_eqI) (simp_all add: assms coeff_map_poly coeff_pCons split: nat.splits) |
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lemma map_poly_map_poly: |
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assumes "f 0 = 0" "g 0 = 0" |
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shows "map_poly f (map_poly g p) = map_poly (f \<circ> g) p" |
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by (intro poly_eqI) (simp add: coeff_map_poly assms) |
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lemma map_poly_id [simp]: "map_poly id p = p" |
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by (simp add: map_poly_def) |
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lemma map_poly_id' [simp]: "map_poly (\<lambda>x. x) p = p" |
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by (simp add: map_poly_def) |
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lemma map_poly_cong: |
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assumes "(\<And>x. x \<in> set (coeffs p) \<Longrightarrow> f x = g x)" |
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shows "map_poly f p = map_poly g p" |
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proof - |
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from assms have "map f (coeffs p) = map g (coeffs p)" by (intro map_cong) simp_all |
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thus ?thesis by (simp only: coeffs_eq_iff coeffs_map_poly) |
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qed |
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lemma map_poly_monom: "f 0 = 0 \<Longrightarrow> map_poly f (monom c n) = monom (f c) n" |
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by (intro poly_eqI) (simp_all add: coeff_map_poly) |
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lemma map_poly_idI: |
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assumes "\<And>x. x \<in> set (coeffs p) \<Longrightarrow> f x = x" |
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shows "map_poly f p = p" |
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316 |
using map_poly_cong[OF assms, of _ id] by simp |
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lemma map_poly_idI': |
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assumes "\<And>x. x \<in> set (coeffs p) \<Longrightarrow> f x = x" |
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shows "p = map_poly f p" |
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321 |
using map_poly_cong[OF assms, of _ id] by simp |
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lemma smult_conv_map_poly: "smult c p = map_poly (\<lambda>x. c * x) p" |
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by (intro poly_eqI) (simp_all add: coeff_map_poly) |
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lemma div_const_poly_conv_map_poly: |
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327 |
assumes "[:c:] dvd p" |
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shows "p div [:c:] = map_poly (\<lambda>x. x div c) p" |
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proof (cases "c = 0") |
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case False |
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from assms obtain q where p: "p = [:c:] * q" by (erule dvdE) |
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moreover { |
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have "smult c q = [:c:] * q" by simp |
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also have "\<dots> div [:c:] = q" by (rule nonzero_mult_divide_cancel_left) (insert False, auto) |
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finally have "smult c q div [:c:] = q" . |
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} |
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ultimately show ?thesis by (intro poly_eqI) (auto simp: coeff_map_poly False) |
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qed (auto intro!: poly_eqI simp: coeff_map_poly) |
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340 |
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341 |
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subsection \<open>Various facts about polynomials\<close> |
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||
63830 | 344 |
lemma prod_mset_const_poly: "prod_mset (image_mset (\<lambda>x. [:f x:]) A) = [:prod_mset (image_mset f A):]" |
63498 | 345 |
by (induction A) (simp_all add: one_poly_def mult_ac) |
346 |
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347 |
lemma degree_mod_less': "b \<noteq> 0 \<Longrightarrow> a mod b \<noteq> 0 \<Longrightarrow> degree (a mod b) < degree b" |
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348 |
using degree_mod_less[of b a] by auto |
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350 |
lemma is_unit_const_poly_iff: |
|
351 |
"[:c :: 'a :: {comm_semiring_1,semiring_no_zero_divisors}:] dvd 1 \<longleftrightarrow> c dvd 1" |
|
352 |
by (auto simp: one_poly_def) |
|
353 |
||
354 |
lemma is_unit_poly_iff: |
|
355 |
fixes p :: "'a :: {comm_semiring_1,semiring_no_zero_divisors} poly" |
|
356 |
shows "p dvd 1 \<longleftrightarrow> (\<exists>c. p = [:c:] \<and> c dvd 1)" |
|
357 |
proof safe |
|
358 |
assume "p dvd 1" |
|
359 |
then obtain q where pq: "1 = p * q" by (erule dvdE) |
|
360 |
hence "degree 1 = degree (p * q)" by simp |
|
361 |
also from pq have "\<dots> = degree p + degree q" by (intro degree_mult_eq) auto |
|
362 |
finally have "degree p = 0" by simp |
|
363 |
from degree_eq_zeroE[OF this] obtain c where c: "p = [:c:]" . |
|
364 |
with \<open>p dvd 1\<close> show "\<exists>c. p = [:c:] \<and> c dvd 1" |
|
365 |
by (auto simp: is_unit_const_poly_iff) |
|
366 |
qed (auto simp: is_unit_const_poly_iff) |
|
367 |
||
368 |
lemma is_unit_polyE: |
|
369 |
fixes p :: "'a :: {comm_semiring_1,semiring_no_zero_divisors} poly" |
|
370 |
assumes "p dvd 1" obtains c where "p = [:c:]" "c dvd 1" |
|
371 |
using assms by (subst (asm) is_unit_poly_iff) blast |
|
372 |
||
373 |
lemma smult_eq_iff: |
|
374 |
assumes "(b :: 'a :: field) \<noteq> 0" |
|
375 |
shows "smult a p = smult b q \<longleftrightarrow> smult (a / b) p = q" |
|
376 |
proof |
|
377 |
assume "smult a p = smult b q" |
|
378 |
also from assms have "smult (inverse b) \<dots> = q" by simp |
|
379 |
finally show "smult (a / b) p = q" by (simp add: field_simps) |
|
380 |
qed (insert assms, auto) |
|
381 |
||
382 |
lemma irreducible_const_poly_iff: |
|
383 |
fixes c :: "'a :: {comm_semiring_1,semiring_no_zero_divisors}" |
|
384 |
shows "irreducible [:c:] \<longleftrightarrow> irreducible c" |
|
385 |
proof |
|
386 |
assume A: "irreducible c" |
|
387 |
show "irreducible [:c:]" |
|
388 |
proof (rule irreducibleI) |
|
389 |
fix a b assume ab: "[:c:] = a * b" |
|
390 |
hence "degree [:c:] = degree (a * b)" by (simp only: ) |
|
391 |
also from A ab have "a \<noteq> 0" "b \<noteq> 0" by auto |
|
392 |
hence "degree (a * b) = degree a + degree b" by (simp add: degree_mult_eq) |
|
393 |
finally have "degree a = 0" "degree b = 0" by auto |
|
394 |
then obtain a' b' where ab': "a = [:a':]" "b = [:b':]" by (auto elim!: degree_eq_zeroE) |
|
395 |
from ab have "coeff [:c:] 0 = coeff (a * b) 0" by (simp only: ) |
|
396 |
hence "c = a' * b'" by (simp add: ab' mult_ac) |
|
397 |
from A and this have "a' dvd 1 \<or> b' dvd 1" by (rule irreducibleD) |
|
398 |
with ab' show "a dvd 1 \<or> b dvd 1" by (auto simp: one_poly_def) |
|
399 |
qed (insert A, auto simp: irreducible_def is_unit_poly_iff) |
|
400 |
next |
|
401 |
assume A: "irreducible [:c:]" |
|
402 |
show "irreducible c" |
|
403 |
proof (rule irreducibleI) |
|
404 |
fix a b assume ab: "c = a * b" |
|
405 |
hence "[:c:] = [:a:] * [:b:]" by (simp add: mult_ac) |
|
406 |
from A and this have "[:a:] dvd 1 \<or> [:b:] dvd 1" by (rule irreducibleD) |
|
407 |
thus "a dvd 1 \<or> b dvd 1" by (simp add: one_poly_def) |
|
408 |
qed (insert A, auto simp: irreducible_def one_poly_def) |
|
409 |
qed |
|
410 |
||
411 |
lemma lead_coeff_monom [simp]: "lead_coeff (monom c n) = c" |
|
412 |
by (cases "c = 0") (simp_all add: lead_coeff_def degree_monom_eq) |
|
413 |
||
414 |
||
415 |
subsection \<open>Normalisation of polynomials\<close> |
|
416 |
||
417 |
instantiation poly :: ("{normalization_semidom,idom_divide}") normalization_semidom |
|
418 |
begin |
|
419 |
||
420 |
definition unit_factor_poly :: "'a poly \<Rightarrow> 'a poly" |
|
421 |
where "unit_factor_poly p = monom (unit_factor (lead_coeff p)) 0" |
|
422 |
||
423 |
definition normalize_poly :: "'a poly \<Rightarrow> 'a poly" |
|
424 |
where "normalize_poly p = map_poly (\<lambda>x. x div unit_factor (lead_coeff p)) p" |
|
425 |
||
426 |
lemma normalize_poly_altdef: |
|
427 |
"normalize p = p div [:unit_factor (lead_coeff p):]" |
|
428 |
proof (cases "p = 0") |
|
429 |
case False |
|
430 |
thus ?thesis |
|
431 |
by (subst div_const_poly_conv_map_poly) |
|
432 |
(auto simp: normalize_poly_def const_poly_dvd_iff lead_coeff_def ) |
|
433 |
qed (auto simp: normalize_poly_def) |
|
434 |
||
435 |
instance |
|
436 |
proof |
|
437 |
fix p :: "'a poly" |
|
438 |
show "unit_factor p * normalize p = p" |
|
439 |
by (cases "p = 0") |
|
440 |
(simp_all add: unit_factor_poly_def normalize_poly_def monom_0 |
|
441 |
smult_conv_map_poly map_poly_map_poly o_def) |
|
442 |
next |
|
443 |
fix p :: "'a poly" |
|
444 |
assume "is_unit p" |
|
445 |
then obtain c where p: "p = [:c:]" "is_unit c" by (auto simp: is_unit_poly_iff) |
|
446 |
thus "normalize p = 1" |
|
447 |
by (simp add: normalize_poly_def map_poly_pCons is_unit_normalize one_poly_def) |
|
448 |
next |
|
449 |
fix p :: "'a poly" assume "p \<noteq> 0" |
|
450 |
thus "is_unit (unit_factor p)" |
|
451 |
by (simp add: unit_factor_poly_def monom_0 is_unit_poly_iff) |
|
452 |
qed (simp_all add: normalize_poly_def unit_factor_poly_def monom_0 lead_coeff_mult unit_factor_mult) |
|
453 |
||
454 |
end |
|
455 |
||
456 |
lemma unit_factor_pCons: |
|
457 |
"unit_factor (pCons a p) = (if p = 0 then monom (unit_factor a) 0 else unit_factor p)" |
|
458 |
by (simp add: unit_factor_poly_def) |
|
459 |
||
460 |
lemma normalize_monom [simp]: |
|
461 |
"normalize (monom a n) = monom (normalize a) n" |
|
462 |
by (simp add: map_poly_monom normalize_poly_def) |
|
463 |
||
464 |
lemma unit_factor_monom [simp]: |
|
465 |
"unit_factor (monom a n) = monom (unit_factor a) 0" |
|
466 |
by (simp add: unit_factor_poly_def ) |
|
467 |
||
468 |
lemma normalize_const_poly: "normalize [:c:] = [:normalize c:]" |
|
469 |
by (simp add: normalize_poly_def map_poly_pCons) |
|
470 |
||
471 |
lemma normalize_smult: "normalize (smult c p) = smult (normalize c) (normalize p)" |
|
472 |
proof - |
|
473 |
have "smult c p = [:c:] * p" by simp |
|
474 |
also have "normalize \<dots> = smult (normalize c) (normalize p)" |
|
475 |
by (subst normalize_mult) (simp add: normalize_const_poly) |
|
476 |
finally show ?thesis . |
|
477 |
qed |
|
478 |
||
479 |
lemma is_unit_smult_iff: "smult c p dvd 1 \<longleftrightarrow> c dvd 1 \<and> p dvd 1" |
|
480 |
proof - |
|
481 |
have "smult c p = [:c:] * p" by simp |
|
482 |
also have "\<dots> dvd 1 \<longleftrightarrow> c dvd 1 \<and> p dvd 1" |
|
483 |
proof safe |
|
484 |
assume A: "[:c:] * p dvd 1" |
|
485 |
thus "p dvd 1" by (rule dvd_mult_right) |
|
486 |
from A obtain q where B: "1 = [:c:] * p * q" by (erule dvdE) |
|
487 |
have "c dvd c * (coeff p 0 * coeff q 0)" by simp |
|
488 |
also have "\<dots> = coeff ([:c:] * p * q) 0" by (simp add: mult.assoc coeff_mult) |
|
489 |
also note B [symmetric] |
|
490 |
finally show "c dvd 1" by simp |
|
491 |
next |
|
492 |
assume "c dvd 1" "p dvd 1" |
|
493 |
from \<open>c dvd 1\<close> obtain d where "1 = c * d" by (erule dvdE) |
|
494 |
hence "1 = [:c:] * [:d:]" by (simp add: one_poly_def mult_ac) |
|
495 |
hence "[:c:] dvd 1" by (rule dvdI) |
|
496 |
from mult_dvd_mono[OF this \<open>p dvd 1\<close>] show "[:c:] * p dvd 1" by simp |
|
497 |
qed |
|
498 |
finally show ?thesis . |
|
499 |
qed |
|
500 |
||
501 |
||
502 |
subsection \<open>Content and primitive part of a polynomial\<close> |
|
503 |
||
504 |
definition content :: "('a :: semiring_Gcd poly) \<Rightarrow> 'a" where |
|
505 |
"content p = Gcd (set (coeffs p))" |
|
506 |
||
507 |
lemma content_0 [simp]: "content 0 = 0" |
|
508 |
by (simp add: content_def) |
|
509 |
||
510 |
lemma content_1 [simp]: "content 1 = 1" |
|
511 |
by (simp add: content_def) |
|
512 |
||
513 |
lemma content_const [simp]: "content [:c:] = normalize c" |
|
514 |
by (simp add: content_def cCons_def) |
|
515 |
||
516 |
lemma const_poly_dvd_iff_dvd_content: |
|
517 |
fixes c :: "'a :: semiring_Gcd" |
|
518 |
shows "[:c:] dvd p \<longleftrightarrow> c dvd content p" |
|
519 |
proof (cases "p = 0") |
|
520 |
case [simp]: False |
|
521 |
have "[:c:] dvd p \<longleftrightarrow> (\<forall>n. c dvd coeff p n)" by (rule const_poly_dvd_iff) |
|
522 |
also have "\<dots> \<longleftrightarrow> (\<forall>a\<in>set (coeffs p). c dvd a)" |
|
523 |
proof safe |
|
524 |
fix n :: nat assume "\<forall>a\<in>set (coeffs p). c dvd a" |
|
525 |
thus "c dvd coeff p n" |
|
526 |
by (cases "n \<le> degree p") (auto simp: coeff_eq_0 coeffs_def split: if_splits) |
|
527 |
qed (auto simp: coeffs_def simp del: upt_Suc split: if_splits) |
|
528 |
also have "\<dots> \<longleftrightarrow> c dvd content p" |
|
529 |
by (simp add: content_def dvd_Gcd_iff mult.commute [of "unit_factor x" for x] |
|
530 |
dvd_mult_unit_iff lead_coeff_nonzero) |
|
531 |
finally show ?thesis . |
|
532 |
qed simp_all |
|
533 |
||
534 |
lemma content_dvd [simp]: "[:content p:] dvd p" |
|
535 |
by (subst const_poly_dvd_iff_dvd_content) simp_all |
|
536 |
||
537 |
lemma content_dvd_coeff [simp]: "content p dvd coeff p n" |
|
538 |
by (cases "n \<le> degree p") |
|
539 |
(auto simp: content_def coeffs_def not_le coeff_eq_0 simp del: upt_Suc intro: Gcd_dvd) |
|
540 |
||
541 |
lemma content_dvd_coeffs: "c \<in> set (coeffs p) \<Longrightarrow> content p dvd c" |
|
542 |
by (simp add: content_def Gcd_dvd) |
|
543 |
||
544 |
lemma normalize_content [simp]: "normalize (content p) = content p" |
|
545 |
by (simp add: content_def) |
|
546 |
||
547 |
lemma is_unit_content_iff [simp]: "is_unit (content p) \<longleftrightarrow> content p = 1" |
|
548 |
proof |
|
549 |
assume "is_unit (content p)" |
|
550 |
hence "normalize (content p) = 1" by (simp add: is_unit_normalize del: normalize_content) |
|
551 |
thus "content p = 1" by simp |
|
552 |
qed auto |
|
553 |
||
554 |
lemma content_smult [simp]: "content (smult c p) = normalize c * content p" |
|
555 |
by (simp add: content_def coeffs_smult Gcd_mult) |
|
556 |
||
557 |
lemma content_eq_zero_iff [simp]: "content p = 0 \<longleftrightarrow> p = 0" |
|
558 |
by (auto simp: content_def simp: poly_eq_iff coeffs_def) |
|
559 |
||
560 |
definition primitive_part :: "'a :: {semiring_Gcd,idom_divide} poly \<Rightarrow> 'a poly" where |
|
561 |
"primitive_part p = (if p = 0 then 0 else map_poly (\<lambda>x. x div content p) p)" |
|
562 |
||
563 |
lemma primitive_part_0 [simp]: "primitive_part 0 = 0" |
|
564 |
by (simp add: primitive_part_def) |
|
565 |
||
566 |
lemma content_times_primitive_part [simp]: |
|
567 |
fixes p :: "'a :: {idom_divide, semiring_Gcd} poly" |
|
568 |
shows "smult (content p) (primitive_part p) = p" |
|
569 |
proof (cases "p = 0") |
|
570 |
case False |
|
571 |
thus ?thesis |
|
572 |
unfolding primitive_part_def |
|
573 |
by (auto simp: smult_conv_map_poly map_poly_map_poly o_def content_dvd_coeffs |
|
574 |
intro: map_poly_idI) |
|
575 |
qed simp_all |
|
576 |
||
577 |
lemma primitive_part_eq_0_iff [simp]: "primitive_part p = 0 \<longleftrightarrow> p = 0" |
|
578 |
proof (cases "p = 0") |
|
579 |
case False |
|
580 |
hence "primitive_part p = map_poly (\<lambda>x. x div content p) p" |
|
581 |
by (simp add: primitive_part_def) |
|
582 |
also from False have "\<dots> = 0 \<longleftrightarrow> p = 0" |
|
583 |
by (intro map_poly_eq_0_iff) (auto simp: dvd_div_eq_0_iff content_dvd_coeffs) |
|
584 |
finally show ?thesis using False by simp |
|
585 |
qed simp |
|
586 |
||
587 |
lemma content_primitive_part [simp]: |
|
588 |
assumes "p \<noteq> 0" |
|
589 |
shows "content (primitive_part p) = 1" |
|
590 |
proof - |
|
591 |
have "p = smult (content p) (primitive_part p)" by simp |
|
592 |
also have "content \<dots> = content p * content (primitive_part p)" |
|
593 |
by (simp del: content_times_primitive_part) |
|
594 |
finally show ?thesis using assms by simp |
|
595 |
qed |
|
596 |
||
597 |
lemma content_decompose: |
|
598 |
fixes p :: "'a :: semiring_Gcd poly" |
|
599 |
obtains p' where "p = smult (content p) p'" "content p' = 1" |
|
600 |
proof (cases "p = 0") |
|
601 |
case True |
|
602 |
thus ?thesis by (intro that[of 1]) simp_all |
|
603 |
next |
|
604 |
case False |
|
605 |
from content_dvd[of p] obtain r where r: "p = [:content p:] * r" by (erule dvdE) |
|
606 |
have "content p * 1 = content p * content r" by (subst r) simp |
|
607 |
with False have "content r = 1" by (subst (asm) mult_left_cancel) simp_all |
|
608 |
with r show ?thesis by (intro that[of r]) simp_all |
|
609 |
qed |
|
610 |
||
611 |
lemma smult_content_normalize_primitive_part [simp]: |
|
612 |
"smult (content p) (normalize (primitive_part p)) = normalize p" |
|
613 |
proof - |
|
614 |
have "smult (content p) (normalize (primitive_part p)) = |
|
615 |
normalize ([:content p:] * primitive_part p)" |
|
616 |
by (subst normalize_mult) (simp_all add: normalize_const_poly) |
|
617 |
also have "[:content p:] * primitive_part p = p" by simp |
|
618 |
finally show ?thesis . |
|
619 |
qed |
|
620 |
||
621 |
lemma content_dvd_contentI [intro]: |
|
622 |
"p dvd q \<Longrightarrow> content p dvd content q" |
|
623 |
using const_poly_dvd_iff_dvd_content content_dvd dvd_trans by blast |
|
624 |
||
625 |
lemma primitive_part_const_poly [simp]: "primitive_part [:x:] = [:unit_factor x:]" |
|
626 |
by (simp add: primitive_part_def map_poly_pCons) |
|
627 |
||
628 |
lemma primitive_part_prim: "content p = 1 \<Longrightarrow> primitive_part p = p" |
|
629 |
by (auto simp: primitive_part_def) |
|
630 |
||
631 |
lemma degree_primitive_part [simp]: "degree (primitive_part p) = degree p" |
|
632 |
proof (cases "p = 0") |
|
633 |
case False |
|
634 |
have "p = smult (content p) (primitive_part p)" by simp |
|
635 |
also from False have "degree \<dots> = degree (primitive_part p)" |
|
636 |
by (subst degree_smult_eq) simp_all |
|
637 |
finally show ?thesis .. |
|
638 |
qed simp_all |
|
639 |
||
640 |
||
641 |
subsection \<open>Lifting polynomial coefficients to the field of fractions\<close> |
|
642 |
||
643 |
abbreviation (input) fract_poly |
|
644 |
where "fract_poly \<equiv> map_poly to_fract" |
|
645 |
||
646 |
abbreviation (input) unfract_poly |
|
647 |
where "unfract_poly \<equiv> map_poly (fst \<circ> quot_of_fract)" |
|
648 |
||
649 |
lemma fract_poly_smult [simp]: "fract_poly (smult c p) = smult (to_fract c) (fract_poly p)" |
|
650 |
by (simp add: smult_conv_map_poly map_poly_map_poly o_def) |
|
651 |
||
652 |
lemma fract_poly_0 [simp]: "fract_poly 0 = 0" |
|
653 |
by (simp add: poly_eqI coeff_map_poly) |
|
654 |
||
655 |
lemma fract_poly_1 [simp]: "fract_poly 1 = 1" |
|
656 |
by (simp add: one_poly_def map_poly_pCons) |
|
657 |
||
658 |
lemma fract_poly_add [simp]: |
|
659 |
"fract_poly (p + q) = fract_poly p + fract_poly q" |
|
660 |
by (intro poly_eqI) (simp_all add: coeff_map_poly) |
|
661 |
||
662 |
lemma fract_poly_diff [simp]: |
|
663 |
"fract_poly (p - q) = fract_poly p - fract_poly q" |
|
664 |
by (intro poly_eqI) (simp_all add: coeff_map_poly) |
|
665 |
||
666 |
lemma to_fract_setsum [simp]: "to_fract (setsum f A) = setsum (\<lambda>x. to_fract (f x)) A" |
|
667 |
by (cases "finite A", induction A rule: finite_induct) simp_all |
|
668 |
||
669 |
lemma fract_poly_mult [simp]: |
|
670 |
"fract_poly (p * q) = fract_poly p * fract_poly q" |
|
671 |
by (intro poly_eqI) (simp_all add: coeff_map_poly coeff_mult) |
|
672 |
||
673 |
lemma fract_poly_eq_iff [simp]: "fract_poly p = fract_poly q \<longleftrightarrow> p = q" |
|
674 |
by (auto simp: poly_eq_iff coeff_map_poly) |
|
675 |
||
676 |
lemma fract_poly_eq_0_iff [simp]: "fract_poly p = 0 \<longleftrightarrow> p = 0" |
|
677 |
using fract_poly_eq_iff[of p 0] by (simp del: fract_poly_eq_iff) |
|
678 |
||
679 |
lemma fract_poly_dvd: "p dvd q \<Longrightarrow> fract_poly p dvd fract_poly q" |
|
680 |
by (auto elim!: dvdE) |
|
681 |
||
63830 | 682 |
lemma prod_mset_fract_poly: |
683 |
"prod_mset (image_mset (\<lambda>x. fract_poly (f x)) A) = fract_poly (prod_mset (image_mset f A))" |
|
63498 | 684 |
by (induction A) (simp_all add: mult_ac) |
685 |
||
686 |
lemma is_unit_fract_poly_iff: |
|
687 |
"p dvd 1 \<longleftrightarrow> fract_poly p dvd 1 \<and> content p = 1" |
|
688 |
proof safe |
|
689 |
assume A: "p dvd 1" |
|
690 |
with fract_poly_dvd[of p 1] show "is_unit (fract_poly p)" by simp |
|
691 |
from A show "content p = 1" |
|
692 |
by (auto simp: is_unit_poly_iff normalize_1_iff) |
|
693 |
next |
|
694 |
assume A: "fract_poly p dvd 1" and B: "content p = 1" |
|
695 |
from A obtain c where c: "fract_poly p = [:c:]" by (auto simp: is_unit_poly_iff) |
|
696 |
{ |
|
697 |
fix n :: nat assume "n > 0" |
|
698 |
have "to_fract (coeff p n) = coeff (fract_poly p) n" by (simp add: coeff_map_poly) |
|
699 |
also note c |
|
700 |
also from \<open>n > 0\<close> have "coeff [:c:] n = 0" by (simp add: coeff_pCons split: nat.splits) |
|
701 |
finally have "coeff p n = 0" by simp |
|
702 |
} |
|
703 |
hence "degree p \<le> 0" by (intro degree_le) simp_all |
|
704 |
with B show "p dvd 1" by (auto simp: is_unit_poly_iff normalize_1_iff elim!: degree_eq_zeroE) |
|
705 |
qed |
|
706 |
||
707 |
lemma fract_poly_is_unit: "p dvd 1 \<Longrightarrow> fract_poly p dvd 1" |
|
708 |
using fract_poly_dvd[of p 1] by simp |
|
709 |
||
710 |
lemma fract_poly_smult_eqE: |
|
711 |
fixes c :: "'a :: {idom_divide,ring_gcd} fract" |
|
712 |
assumes "fract_poly p = smult c (fract_poly q)" |
|
713 |
obtains a b |
|
714 |
where "c = to_fract b / to_fract a" "smult a p = smult b q" "coprime a b" "normalize a = a" |
|
715 |
proof - |
|
716 |
define a b where "a = fst (quot_of_fract c)" and "b = snd (quot_of_fract c)" |
|
717 |
have "smult (to_fract a) (fract_poly q) = smult (to_fract b) (fract_poly p)" |
|
718 |
by (subst smult_eq_iff) (simp_all add: a_def b_def Fract_conv_to_fract [symmetric] assms) |
|
719 |
hence "fract_poly (smult a q) = fract_poly (smult b p)" by (simp del: fract_poly_eq_iff) |
|
720 |
hence "smult b p = smult a q" by (simp only: fract_poly_eq_iff) |
|
721 |
moreover have "c = to_fract a / to_fract b" "coprime b a" "normalize b = b" |
|
722 |
by (simp_all add: a_def b_def coprime_quot_of_fract gcd.commute |
|
723 |
normalize_snd_quot_of_fract Fract_conv_to_fract [symmetric]) |
|
724 |
ultimately show ?thesis by (intro that[of a b]) |
|
725 |
qed |
|
726 |
||
727 |
||
728 |
subsection \<open>Fractional content\<close> |
|
729 |
||
730 |
abbreviation (input) Lcm_coeff_denoms |
|
731 |
:: "'a :: {semiring_Gcd,idom_divide,ring_gcd} fract poly \<Rightarrow> 'a" |
|
732 |
where "Lcm_coeff_denoms p \<equiv> Lcm (snd ` quot_of_fract ` set (coeffs p))" |
|
733 |
||
734 |
definition fract_content :: |
|
735 |
"'a :: {factorial_semiring,semiring_Gcd,ring_gcd,idom_divide} fract poly \<Rightarrow> 'a fract" where |
|
736 |
"fract_content p = |
|
737 |
(let d = Lcm_coeff_denoms p in Fract (content (unfract_poly (smult (to_fract d) p))) d)" |
|
738 |
||
739 |
definition primitive_part_fract :: |
|
740 |
"'a :: {factorial_semiring,semiring_Gcd,ring_gcd,idom_divide} fract poly \<Rightarrow> 'a poly" where |
|
741 |
"primitive_part_fract p = |
|
742 |
primitive_part (unfract_poly (smult (to_fract (Lcm_coeff_denoms p)) p))" |
|
743 |
||
744 |
lemma primitive_part_fract_0 [simp]: "primitive_part_fract 0 = 0" |
|
745 |
by (simp add: primitive_part_fract_def) |
|
746 |
||
747 |
lemma fract_content_eq_0_iff [simp]: |
|
748 |
"fract_content p = 0 \<longleftrightarrow> p = 0" |
|
749 |
unfolding fract_content_def Let_def Zero_fract_def |
|
750 |
by (subst eq_fract) (auto simp: Lcm_0_iff map_poly_eq_0_iff) |
|
751 |
||
752 |
lemma content_primitive_part_fract [simp]: "p \<noteq> 0 \<Longrightarrow> content (primitive_part_fract p) = 1" |
|
753 |
unfolding primitive_part_fract_def |
|
754 |
by (rule content_primitive_part) |
|
755 |
(auto simp: primitive_part_fract_def map_poly_eq_0_iff Lcm_0_iff) |
|
756 |
||
757 |
lemma content_times_primitive_part_fract: |
|
758 |
"smult (fract_content p) (fract_poly (primitive_part_fract p)) = p" |
|
759 |
proof - |
|
760 |
define p' where "p' = unfract_poly (smult (to_fract (Lcm_coeff_denoms p)) p)" |
|
761 |
have "fract_poly p' = |
|
762 |
map_poly (to_fract \<circ> fst \<circ> quot_of_fract) (smult (to_fract (Lcm_coeff_denoms p)) p)" |
|
763 |
unfolding primitive_part_fract_def p'_def |
|
764 |
by (subst map_poly_map_poly) (simp_all add: o_assoc) |
|
765 |
also have "\<dots> = smult (to_fract (Lcm_coeff_denoms p)) p" |
|
766 |
proof (intro map_poly_idI, unfold o_apply) |
|
767 |
fix c assume "c \<in> set (coeffs (smult (to_fract (Lcm_coeff_denoms p)) p))" |
|
768 |
then obtain c' where c: "c' \<in> set (coeffs p)" "c = to_fract (Lcm_coeff_denoms p) * c'" |
|
769 |
by (auto simp add: Lcm_0_iff coeffs_smult split: if_splits) |
|
770 |
note c(2) |
|
771 |
also have "c' = Fract (fst (quot_of_fract c')) (snd (quot_of_fract c'))" |
|
772 |
by simp |
|
773 |
also have "to_fract (Lcm_coeff_denoms p) * \<dots> = |
|
774 |
Fract (Lcm_coeff_denoms p * fst (quot_of_fract c')) (snd (quot_of_fract c'))" |
|
775 |
unfolding to_fract_def by (subst mult_fract) simp_all |
|
776 |
also have "snd (quot_of_fract \<dots>) = 1" |
|
777 |
by (intro snd_quot_of_fract_Fract_whole dvd_mult2 dvd_Lcm) (insert c(1), auto) |
|
778 |
finally show "to_fract (fst (quot_of_fract c)) = c" |
|
779 |
by (rule to_fract_quot_of_fract) |
|
780 |
qed |
|
781 |
also have "p' = smult (content p') (primitive_part p')" |
|
782 |
by (rule content_times_primitive_part [symmetric]) |
|
783 |
also have "primitive_part p' = primitive_part_fract p" |
|
784 |
by (simp add: primitive_part_fract_def p'_def) |
|
785 |
also have "fract_poly (smult (content p') (primitive_part_fract p)) = |
|
786 |
smult (to_fract (content p')) (fract_poly (primitive_part_fract p))" by simp |
|
787 |
finally have "smult (to_fract (content p')) (fract_poly (primitive_part_fract p)) = |
|
788 |
smult (to_fract (Lcm_coeff_denoms p)) p" . |
|
789 |
thus ?thesis |
|
790 |
by (subst (asm) smult_eq_iff) |
|
791 |
(auto simp add: Let_def p'_def Fract_conv_to_fract field_simps Lcm_0_iff fract_content_def) |
|
792 |
qed |
|
793 |
||
794 |
lemma fract_content_fract_poly [simp]: "fract_content (fract_poly p) = to_fract (content p)" |
|
795 |
proof - |
|
796 |
have "Lcm_coeff_denoms (fract_poly p) = 1" |
|
63905 | 797 |
by (auto simp: set_coeffs_map_poly) |
63498 | 798 |
hence "fract_content (fract_poly p) = |
799 |
to_fract (content (map_poly (fst \<circ> quot_of_fract \<circ> to_fract) p))" |
|
800 |
by (simp add: fract_content_def to_fract_def fract_collapse map_poly_map_poly del: Lcm_1_iff) |
|
801 |
also have "map_poly (fst \<circ> quot_of_fract \<circ> to_fract) p = p" |
|
802 |
by (intro map_poly_idI) simp_all |
|
803 |
finally show ?thesis . |
|
804 |
qed |
|
805 |
||
806 |
lemma content_decompose_fract: |
|
807 |
fixes p :: "'a :: {factorial_semiring,semiring_Gcd,ring_gcd,idom_divide} fract poly" |
|
808 |
obtains c p' where "p = smult c (map_poly to_fract p')" "content p' = 1" |
|
809 |
proof (cases "p = 0") |
|
810 |
case True |
|
811 |
hence "p = smult 0 (map_poly to_fract 1)" "content 1 = 1" by simp_all |
|
812 |
thus ?thesis .. |
|
813 |
next |
|
814 |
case False |
|
815 |
thus ?thesis |
|
816 |
by (rule that[OF content_times_primitive_part_fract [symmetric] content_primitive_part_fract]) |
|
817 |
qed |
|
818 |
||
819 |
||
820 |
subsection \<open>More properties of content and primitive part\<close> |
|
821 |
||
822 |
lemma lift_prime_elem_poly: |
|
63633 | 823 |
assumes "prime_elem (c :: 'a :: semidom)" |
824 |
shows "prime_elem [:c:]" |
|
825 |
proof (rule prime_elemI) |
|
63498 | 826 |
fix a b assume *: "[:c:] dvd a * b" |
827 |
from * have dvd: "c dvd coeff (a * b) n" for n |
|
828 |
by (subst (asm) const_poly_dvd_iff) blast |
|
829 |
{ |
|
830 |
define m where "m = (GREATEST m. \<not>c dvd coeff b m)" |
|
831 |
assume "\<not>[:c:] dvd b" |
|
832 |
hence A: "\<exists>i. \<not>c dvd coeff b i" by (subst (asm) const_poly_dvd_iff) blast |
|
833 |
have B: "\<forall>i. \<not>c dvd coeff b i \<longrightarrow> i < Suc (degree b)" |
|
834 |
by (auto intro: le_degree simp: less_Suc_eq_le) |
|
835 |
have coeff_m: "\<not>c dvd coeff b m" unfolding m_def by (rule GreatestI_ex[OF A B]) |
|
836 |
have "i \<le> m" if "\<not>c dvd coeff b i" for i |
|
837 |
unfolding m_def by (rule Greatest_le[OF that B]) |
|
838 |
hence dvd_b: "c dvd coeff b i" if "i > m" for i using that by force |
|
839 |
||
840 |
have "c dvd coeff a i" for i |
|
841 |
proof (induction i rule: nat_descend_induct[of "degree a"]) |
|
842 |
case (base i) |
|
843 |
thus ?case by (simp add: coeff_eq_0) |
|
844 |
next |
|
845 |
case (descend i) |
|
846 |
let ?A = "{..i+m} - {i}" |
|
847 |
have "c dvd coeff (a * b) (i + m)" by (rule dvd) |
|
848 |
also have "coeff (a * b) (i + m) = (\<Sum>k\<le>i + m. coeff a k * coeff b (i + m - k))" |
|
849 |
by (simp add: coeff_mult) |
|
850 |
also have "{..i+m} = insert i ?A" by auto |
|
851 |
also have "(\<Sum>k\<in>\<dots>. coeff a k * coeff b (i + m - k)) = |
|
852 |
coeff a i * coeff b m + (\<Sum>k\<in>?A. coeff a k * coeff b (i + m - k))" |
|
853 |
(is "_ = _ + ?S") |
|
854 |
by (subst setsum.insert) simp_all |
|
855 |
finally have eq: "c dvd coeff a i * coeff b m + ?S" . |
|
856 |
moreover have "c dvd ?S" |
|
857 |
proof (rule dvd_setsum) |
|
858 |
fix k assume k: "k \<in> {..i+m} - {i}" |
|
859 |
show "c dvd coeff a k * coeff b (i + m - k)" |
|
860 |
proof (cases "k < i") |
|
861 |
case False |
|
862 |
with k have "c dvd coeff a k" by (intro descend.IH) simp |
|
863 |
thus ?thesis by simp |
|
864 |
next |
|
865 |
case True |
|
866 |
hence "c dvd coeff b (i + m - k)" by (intro dvd_b) simp |
|
867 |
thus ?thesis by simp |
|
868 |
qed |
|
869 |
qed |
|
870 |
ultimately have "c dvd coeff a i * coeff b m" |
|
871 |
by (simp add: dvd_add_left_iff) |
|
872 |
with assms coeff_m show "c dvd coeff a i" |
|
63633 | 873 |
by (simp add: prime_elem_dvd_mult_iff) |
63498 | 874 |
qed |
875 |
hence "[:c:] dvd a" by (subst const_poly_dvd_iff) blast |
|
876 |
} |
|
877 |
thus "[:c:] dvd a \<or> [:c:] dvd b" by blast |
|
63633 | 878 |
qed (insert assms, simp_all add: prime_elem_def one_poly_def) |
63498 | 879 |
|
880 |
lemma prime_elem_const_poly_iff: |
|
881 |
fixes c :: "'a :: semidom" |
|
63633 | 882 |
shows "prime_elem [:c:] \<longleftrightarrow> prime_elem c" |
63498 | 883 |
proof |
63633 | 884 |
assume A: "prime_elem [:c:]" |
885 |
show "prime_elem c" |
|
886 |
proof (rule prime_elemI) |
|
63498 | 887 |
fix a b assume "c dvd a * b" |
888 |
hence "[:c:] dvd [:a:] * [:b:]" by (simp add: mult_ac) |
|
63633 | 889 |
from A and this have "[:c:] dvd [:a:] \<or> [:c:] dvd [:b:]" by (rule prime_elem_dvd_multD) |
63498 | 890 |
thus "c dvd a \<or> c dvd b" by simp |
63633 | 891 |
qed (insert A, auto simp: prime_elem_def is_unit_poly_iff) |
63498 | 892 |
qed (auto intro: lift_prime_elem_poly) |
893 |
||
894 |
context |
|
895 |
begin |
|
896 |
||
897 |
private lemma content_1_mult: |
|
898 |
fixes f g :: "'a :: {semiring_Gcd,factorial_semiring} poly" |
|
899 |
assumes "content f = 1" "content g = 1" |
|
900 |
shows "content (f * g) = 1" |
|
901 |
proof (cases "f * g = 0") |
|
902 |
case False |
|
903 |
from assms have "f \<noteq> 0" "g \<noteq> 0" by auto |
|
904 |
||
905 |
hence "f * g \<noteq> 0" by auto |
|
906 |
{ |
|
907 |
assume "\<not>is_unit (content (f * g))" |
|
63633 | 908 |
with False have "\<exists>p. p dvd content (f * g) \<and> prime p" |
63498 | 909 |
by (intro prime_divisor_exists) simp_all |
63633 | 910 |
then obtain p where "p dvd content (f * g)" "prime p" by blast |
63498 | 911 |
from \<open>p dvd content (f * g)\<close> have "[:p:] dvd f * g" |
912 |
by (simp add: const_poly_dvd_iff_dvd_content) |
|
63633 | 913 |
moreover from \<open>prime p\<close> have "prime_elem [:p:]" by (simp add: lift_prime_elem_poly) |
63498 | 914 |
ultimately have "[:p:] dvd f \<or> [:p:] dvd g" |
63633 | 915 |
by (simp add: prime_elem_dvd_mult_iff) |
63498 | 916 |
with assms have "is_unit p" by (simp add: const_poly_dvd_iff_dvd_content) |
63633 | 917 |
with \<open>prime p\<close> have False by simp |
63498 | 918 |
} |
919 |
hence "is_unit (content (f * g))" by blast |
|
920 |
hence "normalize (content (f * g)) = 1" by (simp add: is_unit_normalize del: normalize_content) |
|
921 |
thus ?thesis by simp |
|
922 |
qed (insert assms, auto) |
|
923 |
||
924 |
lemma content_mult: |
|
925 |
fixes p q :: "'a :: {factorial_semiring, semiring_Gcd} poly" |
|
926 |
shows "content (p * q) = content p * content q" |
|
927 |
proof - |
|
928 |
from content_decompose[of p] guess p' . note p = this |
|
929 |
from content_decompose[of q] guess q' . note q = this |
|
930 |
have "content (p * q) = content p * content q * content (p' * q')" |
|
931 |
by (subst p, subst q) (simp add: mult_ac normalize_mult) |
|
932 |
also from p q have "content (p' * q') = 1" by (intro content_1_mult) |
|
933 |
finally show ?thesis by simp |
|
934 |
qed |
|
935 |
||
936 |
lemma primitive_part_mult: |
|
937 |
fixes p q :: "'a :: {factorial_semiring, semiring_Gcd, ring_gcd, idom_divide} poly" |
|
938 |
shows "primitive_part (p * q) = primitive_part p * primitive_part q" |
|
939 |
proof - |
|
940 |
have "primitive_part (p * q) = p * q div [:content (p * q):]" |
|
941 |
by (simp add: primitive_part_def div_const_poly_conv_map_poly) |
|
942 |
also have "\<dots> = (p div [:content p:]) * (q div [:content q:])" |
|
943 |
by (subst div_mult_div_if_dvd) (simp_all add: content_mult mult_ac) |
|
944 |
also have "\<dots> = primitive_part p * primitive_part q" |
|
945 |
by (simp add: primitive_part_def div_const_poly_conv_map_poly) |
|
946 |
finally show ?thesis . |
|
947 |
qed |
|
948 |
||
949 |
lemma primitive_part_smult: |
|
950 |
fixes p :: "'a :: {factorial_semiring, semiring_Gcd, ring_gcd, idom_divide} poly" |
|
951 |
shows "primitive_part (smult a p) = smult (unit_factor a) (primitive_part p)" |
|
952 |
proof - |
|
953 |
have "smult a p = [:a:] * p" by simp |
|
954 |
also have "primitive_part \<dots> = smult (unit_factor a) (primitive_part p)" |
|
955 |
by (subst primitive_part_mult) simp_all |
|
956 |
finally show ?thesis . |
|
957 |
qed |
|
958 |
||
959 |
lemma primitive_part_dvd_primitive_partI [intro]: |
|
960 |
fixes p q :: "'a :: {factorial_semiring, semiring_Gcd, ring_gcd, idom_divide} poly" |
|
961 |
shows "p dvd q \<Longrightarrow> primitive_part p dvd primitive_part q" |
|
962 |
by (auto elim!: dvdE simp: primitive_part_mult) |
|
963 |
||
63830 | 964 |
lemma content_prod_mset: |
63498 | 965 |
fixes A :: "'a :: {factorial_semiring, semiring_Gcd} poly multiset" |
63830 | 966 |
shows "content (prod_mset A) = prod_mset (image_mset content A)" |
63498 | 967 |
by (induction A) (simp_all add: content_mult mult_ac) |
968 |
||
969 |
lemma fract_poly_dvdD: |
|
970 |
fixes p :: "'a :: {factorial_semiring,semiring_Gcd,ring_gcd,idom_divide} poly" |
|
971 |
assumes "fract_poly p dvd fract_poly q" "content p = 1" |
|
972 |
shows "p dvd q" |
|
973 |
proof - |
|
974 |
from assms(1) obtain r where r: "fract_poly q = fract_poly p * r" by (erule dvdE) |
|
975 |
from content_decompose_fract[of r] guess c r' . note r' = this |
|
976 |
from r r' have eq: "fract_poly q = smult c (fract_poly (p * r'))" by simp |
|
977 |
from fract_poly_smult_eqE[OF this] guess a b . note ab = this |
|
978 |
have "content (smult a q) = content (smult b (p * r'))" by (simp only: ab(2)) |
|
979 |
hence eq': "normalize b = a * content q" by (simp add: assms content_mult r' ab(4)) |
|
980 |
have "1 = gcd a (normalize b)" by (simp add: ab) |
|
981 |
also note eq' |
|
982 |
also have "gcd a (a * content q) = a" by (simp add: gcd_proj1_if_dvd ab(4)) |
|
983 |
finally have [simp]: "a = 1" by simp |
|
984 |
from eq ab have "q = p * ([:b:] * r')" by simp |
|
985 |
thus ?thesis by (rule dvdI) |
|
986 |
qed |
|
987 |
||
988 |
lemma content_prod_eq_1_iff: |
|
989 |
fixes p q :: "'a :: {factorial_semiring, semiring_Gcd} poly" |
|
990 |
shows "content (p * q) = 1 \<longleftrightarrow> content p = 1 \<and> content q = 1" |
|
991 |
proof safe |
|
992 |
assume A: "content (p * q) = 1" |
|
993 |
{ |
|
994 |
fix p q :: "'a poly" assume "content p * content q = 1" |
|
995 |
hence "1 = content p * content q" by simp |
|
996 |
hence "content p dvd 1" by (rule dvdI) |
|
997 |
hence "content p = 1" by simp |
|
998 |
} note B = this |
|
999 |
from A B[of p q] B [of q p] show "content p = 1" "content q = 1" |
|
1000 |
by (simp_all add: content_mult mult_ac) |
|
1001 |
qed (auto simp: content_mult) |
|
1002 |
||
1003 |
end |
|
1004 |
||
1005 |
||
1006 |
subsection \<open>Polynomials over a field are a Euclidean ring\<close> |
|
1007 |
||
63722
b9c8da46443b
Deprivatisation of lemmas in Polynomial_Factorial
Manuel Eberl <eberlm@in.tum.de>
parents:
63705
diff
changeset
|
1008 |
definition unit_factor_field_poly :: "'a :: field poly \<Rightarrow> 'a poly" where |
63498 | 1009 |
"unit_factor_field_poly p = [:lead_coeff p:]" |
1010 |
||
63722
b9c8da46443b
Deprivatisation of lemmas in Polynomial_Factorial
Manuel Eberl <eberlm@in.tum.de>
parents:
63705
diff
changeset
|
1011 |
definition normalize_field_poly :: "'a :: field poly \<Rightarrow> 'a poly" where |
63498 | 1012 |
"normalize_field_poly p = smult (inverse (lead_coeff p)) p" |
1013 |
||
63722
b9c8da46443b
Deprivatisation of lemmas in Polynomial_Factorial
Manuel Eberl <eberlm@in.tum.de>
parents:
63705
diff
changeset
|
1014 |
definition euclidean_size_field_poly :: "'a :: field poly \<Rightarrow> nat" where |
63498 | 1015 |
"euclidean_size_field_poly p = (if p = 0 then 0 else 2 ^ degree p)" |
1016 |
||
63722
b9c8da46443b
Deprivatisation of lemmas in Polynomial_Factorial
Manuel Eberl <eberlm@in.tum.de>
parents:
63705
diff
changeset
|
1017 |
lemma dvd_field_poly: "dvd.dvd (op * :: 'a :: field poly \<Rightarrow> _) = op dvd" |
63498 | 1018 |
by (intro ext) (simp_all add: dvd.dvd_def dvd_def) |
1019 |
||
1020 |
interpretation field_poly: |
|
1021 |
euclidean_ring "op div" "op *" "op mod" "op +" "op -" 0 "1 :: 'a :: field poly" |
|
1022 |
normalize_field_poly unit_factor_field_poly euclidean_size_field_poly uminus |
|
1023 |
proof (standard, unfold dvd_field_poly) |
|
1024 |
fix p :: "'a poly" |
|
1025 |
show "unit_factor_field_poly p * normalize_field_poly p = p" |
|
1026 |
by (cases "p = 0") |
|
1027 |
(simp_all add: unit_factor_field_poly_def normalize_field_poly_def lead_coeff_nonzero) |
|
1028 |
next |
|
1029 |
fix p :: "'a poly" assume "is_unit p" |
|
1030 |
thus "normalize_field_poly p = 1" |
|
1031 |
by (elim is_unit_polyE) (auto simp: normalize_field_poly_def monom_0 one_poly_def field_simps) |
|
1032 |
next |
|
1033 |
fix p :: "'a poly" assume "p \<noteq> 0" |
|
1034 |
thus "is_unit (unit_factor_field_poly p)" |
|
1035 |
by (simp add: unit_factor_field_poly_def lead_coeff_nonzero is_unit_pCons_iff) |
|
1036 |
qed (auto simp: unit_factor_field_poly_def normalize_field_poly_def lead_coeff_mult |
|
1037 |
euclidean_size_field_poly_def intro!: degree_mod_less' degree_mult_right_le) |
|
1038 |
||
63722
b9c8da46443b
Deprivatisation of lemmas in Polynomial_Factorial
Manuel Eberl <eberlm@in.tum.de>
parents:
63705
diff
changeset
|
1039 |
lemma field_poly_irreducible_imp_prime: |
63498 | 1040 |
assumes "irreducible (p :: 'a :: field poly)" |
63633 | 1041 |
shows "prime_elem p" |
63498 | 1042 |
proof - |
1043 |
have A: "class.comm_semiring_1 op * 1 op + (0 :: 'a poly)" .. |
|
63633 | 1044 |
from field_poly.irreducible_imp_prime_elem[of p] assms |
1045 |
show ?thesis unfolding irreducible_def prime_elem_def dvd_field_poly |
|
1046 |
comm_semiring_1.irreducible_def[OF A] comm_semiring_1.prime_elem_def[OF A] by blast |
|
63498 | 1047 |
qed |
1048 |
||
63830 | 1049 |
lemma field_poly_prod_mset_prime_factorization: |
63498 | 1050 |
assumes "(x :: 'a :: field poly) \<noteq> 0" |
63830 | 1051 |
shows "prod_mset (field_poly.prime_factorization x) = normalize_field_poly x" |
63498 | 1052 |
proof - |
1053 |
have A: "class.comm_monoid_mult op * (1 :: 'a poly)" .. |
|
63830 | 1054 |
have "comm_monoid_mult.prod_mset op * (1 :: 'a poly) = prod_mset" |
1055 |
by (intro ext) (simp add: comm_monoid_mult.prod_mset_def[OF A] prod_mset_def) |
|
1056 |
with field_poly.prod_mset_prime_factorization[OF assms] show ?thesis by simp |
|
63498 | 1057 |
qed |
1058 |
||
63722
b9c8da46443b
Deprivatisation of lemmas in Polynomial_Factorial
Manuel Eberl <eberlm@in.tum.de>
parents:
63705
diff
changeset
|
1059 |
lemma field_poly_in_prime_factorization_imp_prime: |
63498 | 1060 |
assumes "(p :: 'a :: field poly) \<in># field_poly.prime_factorization x" |
63633 | 1061 |
shows "prime_elem p" |
63498 | 1062 |
proof - |
1063 |
have A: "class.comm_semiring_1 op * 1 op + (0 :: 'a poly)" .. |
|
1064 |
have B: "class.normalization_semidom op div op + op - (0 :: 'a poly) op * 1 |
|
1065 |
normalize_field_poly unit_factor_field_poly" .. |
|
63905 | 1066 |
from field_poly.in_prime_factors_imp_prime [of p x] assms |
63633 | 1067 |
show ?thesis unfolding prime_elem_def dvd_field_poly |
1068 |
comm_semiring_1.prime_elem_def[OF A] normalization_semidom.prime_def[OF B] by blast |
|
63498 | 1069 |
qed |
1070 |
||
1071 |
||
1072 |
subsection \<open>Primality and irreducibility in polynomial rings\<close> |
|
1073 |
||
1074 |
lemma nonconst_poly_irreducible_iff: |
|
1075 |
fixes p :: "'a :: {factorial_semiring,semiring_Gcd,ring_gcd,idom_divide} poly" |
|
1076 |
assumes "degree p \<noteq> 0" |
|
1077 |
shows "irreducible p \<longleftrightarrow> irreducible (fract_poly p) \<and> content p = 1" |
|
1078 |
proof safe |
|
1079 |
assume p: "irreducible p" |
|
1080 |
||
1081 |
from content_decompose[of p] guess p' . note p' = this |
|
1082 |
hence "p = [:content p:] * p'" by simp |
|
1083 |
from p this have "[:content p:] dvd 1 \<or> p' dvd 1" by (rule irreducibleD) |
|
1084 |
moreover have "\<not>p' dvd 1" |
|
1085 |
proof |
|
1086 |
assume "p' dvd 1" |
|
1087 |
hence "degree p = 0" by (subst p') (auto simp: is_unit_poly_iff) |
|
1088 |
with assms show False by contradiction |
|
1089 |
qed |
|
1090 |
ultimately show [simp]: "content p = 1" by (simp add: is_unit_const_poly_iff) |
|
1091 |
||
1092 |
show "irreducible (map_poly to_fract p)" |
|
1093 |
proof (rule irreducibleI) |
|
1094 |
have "fract_poly p = 0 \<longleftrightarrow> p = 0" by (intro map_poly_eq_0_iff) auto |
|
1095 |
with assms show "map_poly to_fract p \<noteq> 0" by auto |
|
1096 |
next |
|
1097 |
show "\<not>is_unit (fract_poly p)" |
|
1098 |
proof |
|
1099 |
assume "is_unit (map_poly to_fract p)" |
|
1100 |
hence "degree (map_poly to_fract p) = 0" |
|
1101 |
by (auto simp: is_unit_poly_iff) |
|
1102 |
hence "degree p = 0" by (simp add: degree_map_poly) |
|
1103 |
with assms show False by contradiction |
|
1104 |
qed |
|
1105 |
next |
|
1106 |
fix q r assume qr: "fract_poly p = q * r" |
|
1107 |
from content_decompose_fract[of q] guess cg q' . note q = this |
|
1108 |
from content_decompose_fract[of r] guess cr r' . note r = this |
|
1109 |
from qr q r p have nz: "cg \<noteq> 0" "cr \<noteq> 0" by auto |
|
1110 |
from qr have eq: "fract_poly p = smult (cr * cg) (fract_poly (q' * r'))" |
|
1111 |
by (simp add: q r) |
|
1112 |
from fract_poly_smult_eqE[OF this] guess a b . note ab = this |
|
1113 |
hence "content (smult a p) = content (smult b (q' * r'))" by (simp only:) |
|
1114 |
with ab(4) have a: "a = normalize b" by (simp add: content_mult q r) |
|
1115 |
hence "normalize b = gcd a b" by simp |
|
1116 |
also from ab(3) have "\<dots> = 1" . |
|
1117 |
finally have "a = 1" "is_unit b" by (simp_all add: a normalize_1_iff) |
|
1118 |
||
1119 |
note eq |
|
1120 |
also from ab(1) \<open>a = 1\<close> have "cr * cg = to_fract b" by simp |
|
1121 |
also have "smult \<dots> (fract_poly (q' * r')) = fract_poly (smult b (q' * r'))" by simp |
|
1122 |
finally have "p = ([:b:] * q') * r'" by (simp del: fract_poly_smult) |
|
1123 |
from p and this have "([:b:] * q') dvd 1 \<or> r' dvd 1" by (rule irreducibleD) |
|
1124 |
hence "q' dvd 1 \<or> r' dvd 1" by (auto dest: dvd_mult_right simp del: mult_pCons_left) |
|
1125 |
hence "fract_poly q' dvd 1 \<or> fract_poly r' dvd 1" by (auto simp: fract_poly_is_unit) |
|
1126 |
with q r show "is_unit q \<or> is_unit r" |
|
1127 |
by (auto simp add: is_unit_smult_iff dvd_field_iff nz) |
|
1128 |
qed |
|
1129 |
||
1130 |
next |
|
1131 |
||
1132 |
assume irred: "irreducible (fract_poly p)" and primitive: "content p = 1" |
|
1133 |
show "irreducible p" |
|
1134 |
proof (rule irreducibleI) |
|
1135 |
from irred show "p \<noteq> 0" by auto |
|
1136 |
next |
|
1137 |
from irred show "\<not>p dvd 1" |
|
1138 |
by (auto simp: irreducible_def dest: fract_poly_is_unit) |
|
1139 |
next |
|
1140 |
fix q r assume qr: "p = q * r" |
|
1141 |
hence "fract_poly p = fract_poly q * fract_poly r" by simp |
|
1142 |
from irred and this have "fract_poly q dvd 1 \<or> fract_poly r dvd 1" |
|
1143 |
by (rule irreducibleD) |
|
1144 |
with primitive qr show "q dvd 1 \<or> r dvd 1" |
|
1145 |
by (auto simp: content_prod_eq_1_iff is_unit_fract_poly_iff) |
|
1146 |
qed |
|
1147 |
qed |
|
1148 |
||
63722
b9c8da46443b
Deprivatisation of lemmas in Polynomial_Factorial
Manuel Eberl <eberlm@in.tum.de>
parents:
63705
diff
changeset
|
1149 |
context |
b9c8da46443b
Deprivatisation of lemmas in Polynomial_Factorial
Manuel Eberl <eberlm@in.tum.de>
parents:
63705
diff
changeset
|
1150 |
begin |
b9c8da46443b
Deprivatisation of lemmas in Polynomial_Factorial
Manuel Eberl <eberlm@in.tum.de>
parents:
63705
diff
changeset
|
1151 |
|
63498 | 1152 |
private lemma irreducible_imp_prime_poly: |
1153 |
fixes p :: "'a :: {factorial_semiring,semiring_Gcd,ring_gcd,idom_divide} poly" |
|
1154 |
assumes "irreducible p" |
|
63633 | 1155 |
shows "prime_elem p" |
63498 | 1156 |
proof (cases "degree p = 0") |
1157 |
case True |
|
1158 |
with assms show ?thesis |
|
1159 |
by (auto simp: prime_elem_const_poly_iff irreducible_const_poly_iff |
|
63633 | 1160 |
intro!: irreducible_imp_prime_elem elim!: degree_eq_zeroE) |
63498 | 1161 |
next |
1162 |
case False |
|
1163 |
from assms False have irred: "irreducible (fract_poly p)" and primitive: "content p = 1" |
|
1164 |
by (simp_all add: nonconst_poly_irreducible_iff) |
|
63633 | 1165 |
from irred have prime: "prime_elem (fract_poly p)" by (rule field_poly_irreducible_imp_prime) |
63498 | 1166 |
show ?thesis |
63633 | 1167 |
proof (rule prime_elemI) |
63498 | 1168 |
fix q r assume "p dvd q * r" |
1169 |
hence "fract_poly p dvd fract_poly (q * r)" by (rule fract_poly_dvd) |
|
1170 |
hence "fract_poly p dvd fract_poly q * fract_poly r" by simp |
|
1171 |
from prime and this have "fract_poly p dvd fract_poly q \<or> fract_poly p dvd fract_poly r" |
|
63633 | 1172 |
by (rule prime_elem_dvd_multD) |
63498 | 1173 |
with primitive show "p dvd q \<or> p dvd r" by (auto dest: fract_poly_dvdD) |
1174 |
qed (insert assms, auto simp: irreducible_def) |
|
1175 |
qed |
|
1176 |
||
1177 |
||
1178 |
lemma degree_primitive_part_fract [simp]: |
|
1179 |
"degree (primitive_part_fract p) = degree p" |
|
1180 |
proof - |
|
1181 |
have "p = smult (fract_content p) (fract_poly (primitive_part_fract p))" |
|
1182 |
by (simp add: content_times_primitive_part_fract) |
|
1183 |
also have "degree \<dots> = degree (primitive_part_fract p)" |
|
1184 |
by (auto simp: degree_map_poly) |
|
1185 |
finally show ?thesis .. |
|
1186 |
qed |
|
1187 |
||
1188 |
lemma irreducible_primitive_part_fract: |
|
1189 |
fixes p :: "'a :: {idom_divide, ring_gcd, factorial_semiring, semiring_Gcd} fract poly" |
|
1190 |
assumes "irreducible p" |
|
1191 |
shows "irreducible (primitive_part_fract p)" |
|
1192 |
proof - |
|
1193 |
from assms have deg: "degree (primitive_part_fract p) \<noteq> 0" |
|
1194 |
by (intro notI) |
|
1195 |
(auto elim!: degree_eq_zeroE simp: irreducible_def is_unit_poly_iff dvd_field_iff) |
|
1196 |
hence [simp]: "p \<noteq> 0" by auto |
|
1197 |
||
1198 |
note \<open>irreducible p\<close> |
|
1199 |
also have "p = [:fract_content p:] * fract_poly (primitive_part_fract p)" |
|
1200 |
by (simp add: content_times_primitive_part_fract) |
|
1201 |
also have "irreducible \<dots> \<longleftrightarrow> irreducible (fract_poly (primitive_part_fract p))" |
|
1202 |
by (intro irreducible_mult_unit_left) (simp_all add: is_unit_poly_iff dvd_field_iff) |
|
1203 |
finally show ?thesis using deg |
|
1204 |
by (simp add: nonconst_poly_irreducible_iff) |
|
1205 |
qed |
|
1206 |
||
63633 | 1207 |
lemma prime_elem_primitive_part_fract: |
63498 | 1208 |
fixes p :: "'a :: {idom_divide, ring_gcd, factorial_semiring, semiring_Gcd} fract poly" |
63633 | 1209 |
shows "irreducible p \<Longrightarrow> prime_elem (primitive_part_fract p)" |
63498 | 1210 |
by (intro irreducible_imp_prime_poly irreducible_primitive_part_fract) |
1211 |
||
1212 |
lemma irreducible_linear_field_poly: |
|
1213 |
fixes a b :: "'a::field" |
|
1214 |
assumes "b \<noteq> 0" |
|
1215 |
shows "irreducible [:a,b:]" |
|
1216 |
proof (rule irreducibleI) |
|
1217 |
fix p q assume pq: "[:a,b:] = p * q" |
|
63539 | 1218 |
also from pq assms have "degree \<dots> = degree p + degree q" |
63498 | 1219 |
by (intro degree_mult_eq) auto |
1220 |
finally have "degree p = 0 \<or> degree q = 0" using assms by auto |
|
1221 |
with assms pq show "is_unit p \<or> is_unit q" |
|
1222 |
by (auto simp: is_unit_const_poly_iff dvd_field_iff elim!: degree_eq_zeroE) |
|
1223 |
qed (insert assms, auto simp: is_unit_poly_iff) |
|
1224 |
||
63633 | 1225 |
lemma prime_elem_linear_field_poly: |
1226 |
"(b :: 'a :: field) \<noteq> 0 \<Longrightarrow> prime_elem [:a,b:]" |
|
63498 | 1227 |
by (rule field_poly_irreducible_imp_prime, rule irreducible_linear_field_poly) |
1228 |
||
1229 |
lemma irreducible_linear_poly: |
|
1230 |
fixes a b :: "'a::{idom_divide,ring_gcd,factorial_semiring,semiring_Gcd}" |
|
1231 |
shows "b \<noteq> 0 \<Longrightarrow> coprime a b \<Longrightarrow> irreducible [:a,b:]" |
|
1232 |
by (auto intro!: irreducible_linear_field_poly |
|
1233 |
simp: nonconst_poly_irreducible_iff content_def map_poly_pCons) |
|
1234 |
||
63633 | 1235 |
lemma prime_elem_linear_poly: |
63498 | 1236 |
fixes a b :: "'a::{idom_divide,ring_gcd,factorial_semiring,semiring_Gcd}" |
63633 | 1237 |
shows "b \<noteq> 0 \<Longrightarrow> coprime a b \<Longrightarrow> prime_elem [:a,b:]" |
63498 | 1238 |
by (rule irreducible_imp_prime_poly, rule irreducible_linear_poly) |
1239 |
||
63722
b9c8da46443b
Deprivatisation of lemmas in Polynomial_Factorial
Manuel Eberl <eberlm@in.tum.de>
parents:
63705
diff
changeset
|
1240 |
end |
b9c8da46443b
Deprivatisation of lemmas in Polynomial_Factorial
Manuel Eberl <eberlm@in.tum.de>
parents:
63705
diff
changeset
|
1241 |
|
63498 | 1242 |
|
1243 |
subsection \<open>Prime factorisation of polynomials\<close> |
|
1244 |
||
63722
b9c8da46443b
Deprivatisation of lemmas in Polynomial_Factorial
Manuel Eberl <eberlm@in.tum.de>
parents:
63705
diff
changeset
|
1245 |
context |
b9c8da46443b
Deprivatisation of lemmas in Polynomial_Factorial
Manuel Eberl <eberlm@in.tum.de>
parents:
63705
diff
changeset
|
1246 |
begin |
b9c8da46443b
Deprivatisation of lemmas in Polynomial_Factorial
Manuel Eberl <eberlm@in.tum.de>
parents:
63705
diff
changeset
|
1247 |
|
63498 | 1248 |
private lemma poly_prime_factorization_exists_content_1: |
1249 |
fixes p :: "'a :: {factorial_semiring,semiring_Gcd,ring_gcd,idom_divide} poly" |
|
1250 |
assumes "p \<noteq> 0" "content p = 1" |
|
63830 | 1251 |
shows "\<exists>A. (\<forall>p. p \<in># A \<longrightarrow> prime_elem p) \<and> prod_mset A = normalize p" |
63498 | 1252 |
proof - |
1253 |
let ?P = "field_poly.prime_factorization (fract_poly p)" |
|
63830 | 1254 |
define c where "c = prod_mset (image_mset fract_content ?P)" |
63498 | 1255 |
define c' where "c' = c * to_fract (lead_coeff p)" |
63830 | 1256 |
define e where "e = prod_mset (image_mset primitive_part_fract ?P)" |
63498 | 1257 |
define A where "A = image_mset (normalize \<circ> primitive_part_fract) ?P" |
1258 |
have "content e = (\<Prod>x\<in>#field_poly.prime_factorization (map_poly to_fract p). |
|
1259 |
content (primitive_part_fract x))" |
|
63830 | 1260 |
by (simp add: e_def content_prod_mset multiset.map_comp o_def) |
63498 | 1261 |
also have "image_mset (\<lambda>x. content (primitive_part_fract x)) ?P = image_mset (\<lambda>_. 1) ?P" |
1262 |
by (intro image_mset_cong content_primitive_part_fract) auto |
|
63830 | 1263 |
finally have content_e: "content e = 1" by (simp add: prod_mset_const) |
63498 | 1264 |
|
1265 |
have "fract_poly p = unit_factor_field_poly (fract_poly p) * |
|
1266 |
normalize_field_poly (fract_poly p)" by simp |
|
1267 |
also have "unit_factor_field_poly (fract_poly p) = [:to_fract (lead_coeff p):]" |
|
1268 |
by (simp add: unit_factor_field_poly_def lead_coeff_def monom_0 degree_map_poly coeff_map_poly) |
|
63830 | 1269 |
also from assms have "normalize_field_poly (fract_poly p) = prod_mset ?P" |
1270 |
by (subst field_poly_prod_mset_prime_factorization) simp_all |
|
1271 |
also have "\<dots> = prod_mset (image_mset id ?P)" by simp |
|
63498 | 1272 |
also have "image_mset id ?P = |
1273 |
image_mset (\<lambda>x. [:fract_content x:] * fract_poly (primitive_part_fract x)) ?P" |
|
1274 |
by (intro image_mset_cong) (auto simp: content_times_primitive_part_fract) |
|
63830 | 1275 |
also have "prod_mset \<dots> = smult c (fract_poly e)" |
1276 |
by (subst prod_mset_mult) (simp_all add: prod_mset_fract_poly prod_mset_const_poly c_def e_def) |
|
63498 | 1277 |
also have "[:to_fract (lead_coeff p):] * \<dots> = smult c' (fract_poly e)" |
1278 |
by (simp add: c'_def) |
|
1279 |
finally have eq: "fract_poly p = smult c' (fract_poly e)" . |
|
1280 |
also obtain b where b: "c' = to_fract b" "is_unit b" |
|
1281 |
proof - |
|
1282 |
from fract_poly_smult_eqE[OF eq] guess a b . note ab = this |
|
1283 |
from ab(2) have "content (smult a p) = content (smult b e)" by (simp only: ) |
|
1284 |
with assms content_e have "a = normalize b" by (simp add: ab(4)) |
|
1285 |
with ab have ab': "a = 1" "is_unit b" by (simp_all add: normalize_1_iff) |
|
1286 |
with ab ab' have "c' = to_fract b" by auto |
|
1287 |
from this and \<open>is_unit b\<close> show ?thesis by (rule that) |
|
1288 |
qed |
|
1289 |
hence "smult c' (fract_poly e) = fract_poly (smult b e)" by simp |
|
1290 |
finally have "p = smult b e" by (simp only: fract_poly_eq_iff) |
|
1291 |
hence "p = [:b:] * e" by simp |
|
1292 |
with b have "normalize p = normalize e" |
|
1293 |
by (simp only: normalize_mult) (simp add: is_unit_normalize is_unit_poly_iff) |
|
63830 | 1294 |
also have "normalize e = prod_mset A" |
1295 |
by (simp add: multiset.map_comp e_def A_def normalize_prod_mset) |
|
1296 |
finally have "prod_mset A = normalize p" .. |
|
63498 | 1297 |
|
63633 | 1298 |
have "prime_elem p" if "p \<in># A" for p |
1299 |
using that by (auto simp: A_def prime_elem_primitive_part_fract prime_elem_imp_irreducible |
|
63498 | 1300 |
dest!: field_poly_in_prime_factorization_imp_prime ) |
63830 | 1301 |
from this and \<open>prod_mset A = normalize p\<close> show ?thesis |
63498 | 1302 |
by (intro exI[of _ A]) blast |
1303 |
qed |
|
1304 |
||
1305 |
lemma poly_prime_factorization_exists: |
|
1306 |
fixes p :: "'a :: {factorial_semiring,semiring_Gcd,ring_gcd,idom_divide} poly" |
|
1307 |
assumes "p \<noteq> 0" |
|
63830 | 1308 |
shows "\<exists>A. (\<forall>p. p \<in># A \<longrightarrow> prime_elem p) \<and> prod_mset A = normalize p" |
63498 | 1309 |
proof - |
1310 |
define B where "B = image_mset (\<lambda>x. [:x:]) (prime_factorization (content p))" |
|
63830 | 1311 |
have "\<exists>A. (\<forall>p. p \<in># A \<longrightarrow> prime_elem p) \<and> prod_mset A = normalize (primitive_part p)" |
63498 | 1312 |
by (rule poly_prime_factorization_exists_content_1) (insert assms, simp_all) |
1313 |
then guess A by (elim exE conjE) note A = this |
|
63830 | 1314 |
moreover from assms have "prod_mset B = [:content p:]" |
1315 |
by (simp add: B_def prod_mset_const_poly prod_mset_prime_factorization) |
|
63633 | 1316 |
moreover have "\<forall>p. p \<in># B \<longrightarrow> prime_elem p" |
63905 | 1317 |
by (auto simp: B_def intro!: lift_prime_elem_poly dest: in_prime_factors_imp_prime) |
63498 | 1318 |
ultimately show ?thesis by (intro exI[of _ "B + A"]) auto |
1319 |
qed |
|
1320 |
||
1321 |
end |
|
1322 |
||
1323 |
||
1324 |
subsection \<open>Typeclass instances\<close> |
|
1325 |
||
1326 |
instance poly :: (factorial_ring_gcd) factorial_semiring |
|
1327 |
by standard (rule poly_prime_factorization_exists) |
|
1328 |
||
1329 |
instantiation poly :: (factorial_ring_gcd) factorial_ring_gcd |
|
1330 |
begin |
|
1331 |
||
1332 |
definition gcd_poly :: "'a poly \<Rightarrow> 'a poly \<Rightarrow> 'a poly" where |
|
1333 |
[code del]: "gcd_poly = gcd_factorial" |
|
1334 |
||
1335 |
definition lcm_poly :: "'a poly \<Rightarrow> 'a poly \<Rightarrow> 'a poly" where |
|
1336 |
[code del]: "lcm_poly = lcm_factorial" |
|
1337 |
||
1338 |
definition Gcd_poly :: "'a poly set \<Rightarrow> 'a poly" where |
|
1339 |
[code del]: "Gcd_poly = Gcd_factorial" |
|
1340 |
||
1341 |
definition Lcm_poly :: "'a poly set \<Rightarrow> 'a poly" where |
|
1342 |
[code del]: "Lcm_poly = Lcm_factorial" |
|
1343 |
||
1344 |
instance by standard (simp_all add: gcd_poly_def lcm_poly_def Gcd_poly_def Lcm_poly_def) |
|
1345 |
||
1346 |
end |
|
1347 |
||
1348 |
instantiation poly :: ("{field,factorial_ring_gcd}") euclidean_ring |
|
1349 |
begin |
|
1350 |
||
1351 |
definition euclidean_size_poly :: "'a poly \<Rightarrow> nat" where |
|
1352 |
"euclidean_size_poly p = (if p = 0 then 0 else 2 ^ degree p)" |
|
1353 |
||
1354 |
instance |
|
1355 |
by standard (auto simp: euclidean_size_poly_def intro!: degree_mod_less' degree_mult_right_le) |
|
1356 |
end |
|
1357 |
||
63499
9c9a59949887
Tuned looping simp rules in semiring_div
eberlm <eberlm@in.tum.de>
parents:
63498
diff
changeset
|
1358 |
|
63498 | 1359 |
instance poly :: ("{field,factorial_ring_gcd}") euclidean_ring_gcd |
1360 |
by standard (simp_all add: gcd_poly_def lcm_poly_def Gcd_poly_def Lcm_poly_def eucl_eq_factorial) |
|
1361 |
||
1362 |
||
1363 |
subsection \<open>Polynomial GCD\<close> |
|
1364 |
||
1365 |
lemma gcd_poly_decompose: |
|
1366 |
fixes p q :: "'a :: factorial_ring_gcd poly" |
|
1367 |
shows "gcd p q = |
|
1368 |
smult (gcd (content p) (content q)) (gcd (primitive_part p) (primitive_part q))" |
|
1369 |
proof (rule sym, rule gcdI) |
|
1370 |
have "[:gcd (content p) (content q):] * gcd (primitive_part p) (primitive_part q) dvd |
|
1371 |
[:content p:] * primitive_part p" by (intro mult_dvd_mono) simp_all |
|
1372 |
thus "smult (gcd (content p) (content q)) (gcd (primitive_part p) (primitive_part q)) dvd p" |
|
1373 |
by simp |
|
1374 |
next |
|
1375 |
have "[:gcd (content p) (content q):] * gcd (primitive_part p) (primitive_part q) dvd |
|
1376 |
[:content q:] * primitive_part q" by (intro mult_dvd_mono) simp_all |
|
1377 |
thus "smult (gcd (content p) (content q)) (gcd (primitive_part p) (primitive_part q)) dvd q" |
|
1378 |
by simp |
|
1379 |
next |
|
1380 |
fix d assume "d dvd p" "d dvd q" |
|
1381 |
hence "[:content d:] * primitive_part d dvd |
|
1382 |
[:gcd (content p) (content q):] * gcd (primitive_part p) (primitive_part q)" |
|
1383 |
by (intro mult_dvd_mono) auto |
|
1384 |
thus "d dvd smult (gcd (content p) (content q)) (gcd (primitive_part p) (primitive_part q))" |
|
1385 |
by simp |
|
1386 |
qed (auto simp: normalize_smult) |
|
1387 |
||
1388 |
||
1389 |
lemma gcd_poly_pseudo_mod: |
|
1390 |
fixes p q :: "'a :: factorial_ring_gcd poly" |
|
1391 |
assumes nz: "q \<noteq> 0" and prim: "content p = 1" "content q = 1" |
|
1392 |
shows "gcd p q = gcd q (primitive_part (pseudo_mod p q))" |
|
1393 |
proof - |
|
1394 |
define r s where "r = fst (pseudo_divmod p q)" and "s = snd (pseudo_divmod p q)" |
|
1395 |
define a where "a = [:coeff q (degree q) ^ (Suc (degree p) - degree q):]" |
|
1396 |
have [simp]: "primitive_part a = unit_factor a" |
|
1397 |
by (simp add: a_def unit_factor_poly_def unit_factor_power monom_0) |
|
1398 |
from nz have [simp]: "a \<noteq> 0" by (auto simp: a_def) |
|
1399 |
||
1400 |
have rs: "pseudo_divmod p q = (r, s)" by (simp add: r_def s_def) |
|
1401 |
have "gcd (q * r + s) q = gcd q s" |
|
1402 |
using gcd_add_mult[of q r s] by (simp add: gcd.commute add_ac mult_ac) |
|
1403 |
with pseudo_divmod(1)[OF nz rs] |
|
1404 |
have "gcd (p * a) q = gcd q s" by (simp add: a_def) |
|
1405 |
also from prim have "gcd (p * a) q = gcd p q" |
|
1406 |
by (subst gcd_poly_decompose) |
|
1407 |
(auto simp: primitive_part_mult gcd_mult_unit1 primitive_part_prim |
|
1408 |
simp del: mult_pCons_right ) |
|
1409 |
also from prim have "gcd q s = gcd q (primitive_part s)" |
|
1410 |
by (subst gcd_poly_decompose) (simp_all add: primitive_part_prim) |
|
1411 |
also have "s = pseudo_mod p q" by (simp add: s_def pseudo_mod_def) |
|
1412 |
finally show ?thesis . |
|
1413 |
qed |
|
1414 |
||
1415 |
lemma degree_pseudo_mod_less: |
|
1416 |
assumes "q \<noteq> 0" "pseudo_mod p q \<noteq> 0" |
|
1417 |
shows "degree (pseudo_mod p q) < degree q" |
|
1418 |
using pseudo_mod(2)[of q p] assms by auto |
|
1419 |
||
1420 |
function gcd_poly_code_aux :: "'a :: factorial_ring_gcd poly \<Rightarrow> 'a poly \<Rightarrow> 'a poly" where |
|
1421 |
"gcd_poly_code_aux p q = |
|
1422 |
(if q = 0 then normalize p else gcd_poly_code_aux q (primitive_part (pseudo_mod p q)))" |
|
1423 |
by auto |
|
1424 |
termination |
|
1425 |
by (relation "measure ((\<lambda>p. if p = 0 then 0 else Suc (degree p)) \<circ> snd)") |
|
1426 |
(auto simp: degree_primitive_part degree_pseudo_mod_less) |
|
1427 |
||
1428 |
declare gcd_poly_code_aux.simps [simp del] |
|
1429 |
||
1430 |
lemma gcd_poly_code_aux_correct: |
|
1431 |
assumes "content p = 1" "q = 0 \<or> content q = 1" |
|
1432 |
shows "gcd_poly_code_aux p q = gcd p q" |
|
1433 |
using assms |
|
1434 |
proof (induction p q rule: gcd_poly_code_aux.induct) |
|
1435 |
case (1 p q) |
|
1436 |
show ?case |
|
1437 |
proof (cases "q = 0") |
|
1438 |
case True |
|
1439 |
thus ?thesis by (subst gcd_poly_code_aux.simps) auto |
|
1440 |
next |
|
1441 |
case False |
|
1442 |
hence "gcd_poly_code_aux p q = gcd_poly_code_aux q (primitive_part (pseudo_mod p q))" |
|
1443 |
by (subst gcd_poly_code_aux.simps) simp_all |
|
1444 |
also from "1.prems" False |
|
1445 |
have "primitive_part (pseudo_mod p q) = 0 \<or> |
|
1446 |
content (primitive_part (pseudo_mod p q)) = 1" |
|
1447 |
by (cases "pseudo_mod p q = 0") auto |
|
1448 |
with "1.prems" False |
|
1449 |
have "gcd_poly_code_aux q (primitive_part (pseudo_mod p q)) = |
|
1450 |
gcd q (primitive_part (pseudo_mod p q))" |
|
1451 |
by (intro 1) simp_all |
|
1452 |
also from "1.prems" False |
|
1453 |
have "\<dots> = gcd p q" by (intro gcd_poly_pseudo_mod [symmetric]) auto |
|
1454 |
finally show ?thesis . |
|
1455 |
qed |
|
1456 |
qed |
|
1457 |
||
1458 |
definition gcd_poly_code |
|
1459 |
:: "'a :: factorial_ring_gcd poly \<Rightarrow> 'a poly \<Rightarrow> 'a poly" |
|
1460 |
where "gcd_poly_code p q = |
|
1461 |
(if p = 0 then normalize q else if q = 0 then normalize p else |
|
1462 |
smult (gcd (content p) (content q)) |
|
1463 |
(gcd_poly_code_aux (primitive_part p) (primitive_part q)))" |
|
1464 |
||
1465 |
lemma lcm_poly_code [code]: |
|
1466 |
fixes p q :: "'a :: factorial_ring_gcd poly" |
|
1467 |
shows "lcm p q = normalize (p * q) div gcd p q" |
|
1468 |
by (rule lcm_gcd) |
|
1469 |
||
1470 |
lemma gcd_poly_code [code]: "gcd p q = gcd_poly_code p q" |
|
1471 |
by (simp add: gcd_poly_code_def gcd_poly_code_aux_correct gcd_poly_decompose [symmetric]) |
|
1472 |
||
1473 |
declare Gcd_set |
|
1474 |
[where ?'a = "'a :: factorial_ring_gcd poly", code] |
|
1475 |
||
1476 |
declare Lcm_set |
|
1477 |
[where ?'a = "'a :: factorial_ring_gcd poly", code] |
|
1478 |
||
1479 |
value [code] "Lcm {[:1,2,3:], [:2,3,4::int poly:]}" |
|
1480 |
||
63764 | 1481 |
end |