src/HOL/Algebra/UnivPoly.thy
author wenzelm
Thu Apr 22 11:01:34 2004 +0200 (2004-04-22)
changeset 14651 02b8f3bcf7fe
parent 14590 276ef51cedbf
child 14666 65f8680c3f16
permissions -rw-r--r--
improved notation;
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(*
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  Title:     Univariate Polynomials
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  Id:        $Id$
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  Author:    Clemens Ballarin, started 9 December 1996
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  Copyright: Clemens Ballarin
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*)
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header {* Univariate Polynomials *}
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theory UnivPoly = Module:
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text {*
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  Polynomials are formalised as modules with additional operations for 
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  extracting coefficients from polynomials and for obtaining monomials 
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  from coefficients and exponents (record @{text "up_ring"}).
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  The carrier set is 
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  a set of bounded functions from Nat to the coefficient domain.  
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  Bounded means that these functions return zero above a certain bound 
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  (the degree).  There is a chapter on the formalisation of polynomials 
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  in my PhD thesis (http://www4.in.tum.de/\~{}ballarin/publications/), 
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  which was implemented with axiomatic type classes.  This was later
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  ported to Locales.
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*}
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subsection {* The Constructor for Univariate Polynomials *}
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(* Could alternatively use locale ...
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locale bound = cring + var bound +
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  defines ...
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*)
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constdefs
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  bound  :: "['a, nat, nat => 'a] => bool"
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  "bound z n f == (ALL i. n < i --> f i = z)"
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lemma boundI [intro!]:
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  "[| !! m. n < m ==> f m = z |] ==> bound z n f"
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  by (unfold bound_def) fast
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lemma boundE [elim?]:
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  "[| bound z n f; (!! m. n < m ==> f m = z) ==> P |] ==> P"
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  by (unfold bound_def) fast
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lemma boundD [dest]:
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  "[| bound z n f; n < m |] ==> f m = z"
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  by (unfold bound_def) fast
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lemma bound_below:
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  assumes bound: "bound z m f" and nonzero: "f n ~= z" shows "n <= m"
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proof (rule classical)
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  assume "~ ?thesis"
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  then have "m < n" by arith
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  with bound have "f n = z" ..
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  with nonzero show ?thesis by contradiction
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qed
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record ('a, 'p) up_ring = "('a, 'p) module" +
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  monom :: "['a, nat] => 'p"
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  coeff :: "['p, nat] => 'a"
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constdefs (structure R)
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  up :: "_ => (nat => 'a) set"
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  "up R == {f. f \<in> UNIV -> carrier R & (EX n. bound \<zero> n f)}"
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  UP :: "_ => ('a, nat => 'a) up_ring"
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  "UP R == (|
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    carrier = up R,
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    mult = (%p:up R. %q:up R. %n. \<Oplus>i \<in> {..n}. p i \<otimes> q (n-i)),
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    one = (%i. if i=0 then \<one> else \<zero>),
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    zero = (%i. \<zero>),
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    add = (%p:up R. %q:up R. %i. p i \<oplus> q i),
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    smult = (%a:carrier R. %p:up R. %i. a \<otimes> p i),
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    monom = (%a:carrier R. %n i. if i=n then a else \<zero>),
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    coeff = (%p:up R. %n. p n) |)"
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text {*
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  Properties of the set of polynomials @{term up}.
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*}
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lemma mem_upI [intro]:
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  "[| !!n. f n \<in> carrier R; EX n. bound (zero R) n f |] ==> f \<in> up R"
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  by (simp add: up_def Pi_def)
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lemma mem_upD [dest]:
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  "f \<in> up R ==> f n \<in> carrier R"
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  by (simp add: up_def Pi_def)
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lemma (in cring) bound_upD [dest]:
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  "f \<in> up R ==> EX n. bound \<zero> n f"
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  by (simp add: up_def)
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lemma (in cring) up_one_closed:
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   "(%n. if n = 0 then \<one> else \<zero>) \<in> up R"
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  using up_def by force
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lemma (in cring) up_smult_closed:
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  "[| a \<in> carrier R; p \<in> up R |] ==> (%i. a \<otimes> p i) \<in> up R"
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  by force
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lemma (in cring) up_add_closed:
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  "[| p \<in> up R; q \<in> up R |] ==> (%i. p i \<oplus> q i) \<in> up R"
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proof
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  fix n
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  assume "p \<in> up R" and "q \<in> up R"
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  then show "p n \<oplus> q n \<in> carrier R"
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    by auto
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next
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  assume UP: "p \<in> up R" "q \<in> up R"
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  show "EX n. bound \<zero> n (%i. p i \<oplus> q i)"
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  proof -
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    from UP obtain n where boundn: "bound \<zero> n p" by fast
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    from UP obtain m where boundm: "bound \<zero> m q" by fast
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    have "bound \<zero> (max n m) (%i. p i \<oplus> q i)"
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    proof
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      fix i
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      assume "max n m < i"
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      with boundn and boundm and UP show "p i \<oplus> q i = \<zero>" by fastsimp
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    qed
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    then show ?thesis ..
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  qed
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qed
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lemma (in cring) up_a_inv_closed:
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  "p \<in> up R ==> (%i. \<ominus> (p i)) \<in> up R"
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proof
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  assume R: "p \<in> up R"
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  then obtain n where "bound \<zero> n p" by auto
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  then have "bound \<zero> n (%i. \<ominus> p i)" by auto
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  then show "EX n. bound \<zero> n (%i. \<ominus> p i)" by auto
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qed auto
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lemma (in cring) up_mult_closed:
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  "[| p \<in> up R; q \<in> up R |] ==>
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  (%n. finsum R (%i. p i \<otimes> q (n-i)) {..n}) \<in> up R"
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proof
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  fix n
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  assume "p \<in> up R" "q \<in> up R"
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  then show "finsum R (%i. p i \<otimes> q (n-i)) {..n} \<in> carrier R"
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    by (simp add: mem_upD  funcsetI)
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next
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  assume UP: "p \<in> up R" "q \<in> up R"
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  show "EX n. bound \<zero> n (%n. finsum R (%i. p i \<otimes> q (n - i)) {..n})"
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  proof -
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    from UP obtain n where boundn: "bound \<zero> n p" by fast
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    from UP obtain m where boundm: "bound \<zero> m q" by fast
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    have "bound \<zero> (n + m) (%n. finsum R (%i. p i \<otimes> q (n - i)) {..n})"
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    proof
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      fix k
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      assume bound: "n + m < k"
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      {
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	fix i
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	have "p i \<otimes> q (k-i) = \<zero>"
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	proof (cases "n < i")
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	  case True
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	  with boundn have "p i = \<zero>" by auto
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          moreover from UP have "q (k-i) \<in> carrier R" by auto
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	  ultimately show ?thesis by simp
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	next
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	  case False
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	  with bound have "m < k-i" by arith
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	  with boundm have "q (k-i) = \<zero>" by auto
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	  moreover from UP have "p i \<in> carrier R" by auto
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	  ultimately show ?thesis by simp
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	qed
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      }
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      then show "finsum R (%i. p i \<otimes> q (k-i)) {..k} = \<zero>"
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	by (simp add: Pi_def)
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    qed
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    then show ?thesis by fast
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  qed
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qed
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subsection {* Effect of operations on coefficients *}
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locale UP = struct R + struct P +
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  defines P_def: "P == UP R"
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locale UP_cring = UP + cring R
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locale UP_domain = UP_cring + "domain" R
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text {*
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  Temporarily declare @{text UP.P_def} as simp rule.
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*}  (* TODO: use antiquotation once text (in locale) is supported. *)
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declare (in UP) P_def [simp]
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lemma (in UP_cring) coeff_monom [simp]:
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  "a \<in> carrier R ==>
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  coeff P (monom P a m) n = (if m=n then a else \<zero>)"
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proof -
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  assume R: "a \<in> carrier R"
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  then have "(%n. if n = m then a else \<zero>) \<in> up R"
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    using up_def by force
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  with R show ?thesis by (simp add: UP_def)
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qed
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lemma (in UP_cring) coeff_zero [simp]:
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  "coeff P \<zero>\<^sub>2 n = \<zero>"
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  by (auto simp add: UP_def)
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lemma (in UP_cring) coeff_one [simp]:
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  "coeff P \<one>\<^sub>2 n = (if n=0 then \<one> else \<zero>)"
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  using up_one_closed by (simp add: UP_def)
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lemma (in UP_cring) coeff_smult [simp]:
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  "[| a \<in> carrier R; p \<in> carrier P |] ==>
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  coeff P (a \<odot>\<^sub>2 p) n = a \<otimes> coeff P p n"
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  by (simp add: UP_def up_smult_closed)
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lemma (in UP_cring) coeff_add [simp]:
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  "[| p \<in> carrier P; q \<in> carrier P |] ==>
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  coeff P (p \<oplus>\<^sub>2 q) n = coeff P p n \<oplus> coeff P q n"
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  by (simp add: UP_def up_add_closed)
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lemma (in UP_cring) coeff_mult [simp]:
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  "[| p \<in> carrier P; q \<in> carrier P |] ==>
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  coeff P (p \<otimes>\<^sub>2 q) n = finsum R (%i. coeff P p i \<otimes> coeff P q (n-i)) {..n}"
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  by (simp add: UP_def up_mult_closed)
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lemma (in UP) up_eqI:
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  assumes prem: "!!n. coeff P p n = coeff P q n"
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    and R: "p \<in> carrier P" "q \<in> carrier P"
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  shows "p = q"
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proof
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  fix x
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  from prem and R show "p x = q x" by (simp add: UP_def)
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qed
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subsection {* Polynomials form a commutative ring. *}
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text {* Operations are closed over @{term "P"}. *}
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lemma (in UP_cring) UP_mult_closed [simp]:
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  "[| p \<in> carrier P; q \<in> carrier P |] ==> p \<otimes>\<^sub>2 q \<in> carrier P"
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  by (simp add: UP_def up_mult_closed)
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lemma (in UP_cring) UP_one_closed [simp]:
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  "\<one>\<^sub>2 \<in> carrier P"
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  by (simp add: UP_def up_one_closed)
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lemma (in UP_cring) UP_zero_closed [intro, simp]:
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  "\<zero>\<^sub>2 \<in> carrier P"
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  by (auto simp add: UP_def)
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lemma (in UP_cring) UP_a_closed [intro, simp]:
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  "[| p \<in> carrier P; q \<in> carrier P |] ==> p \<oplus>\<^sub>2 q \<in> carrier P"
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  by (simp add: UP_def up_add_closed)
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lemma (in UP_cring) monom_closed [simp]:
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  "a \<in> carrier R ==> monom P a n \<in> carrier P"
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  by (auto simp add: UP_def up_def Pi_def)
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lemma (in UP_cring) UP_smult_closed [simp]:
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  "[| a \<in> carrier R; p \<in> carrier P |] ==> a \<odot>\<^sub>2 p \<in> carrier P"
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  by (simp add: UP_def up_smult_closed)
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lemma (in UP) coeff_closed [simp]:
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  "p \<in> carrier P ==> coeff P p n \<in> carrier R"
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  by (auto simp add: UP_def)
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declare (in UP) P_def [simp del]
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text {* Algebraic ring properties *}
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lemma (in UP_cring) UP_a_assoc:
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  assumes R: "p \<in> carrier P" "q \<in> carrier P" "r \<in> carrier P"
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  shows "(p \<oplus>\<^sub>2 q) \<oplus>\<^sub>2 r = p \<oplus>\<^sub>2 (q \<oplus>\<^sub>2 r)"
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  by (rule up_eqI, simp add: a_assoc R, simp_all add: R)
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lemma (in UP_cring) UP_l_zero [simp]:
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  assumes R: "p \<in> carrier P"
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  shows "\<zero>\<^sub>2 \<oplus>\<^sub>2 p = p"
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  by (rule up_eqI, simp_all add: R)
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lemma (in UP_cring) UP_l_neg_ex:
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  assumes R: "p \<in> carrier P"
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  shows "EX q : carrier P. q \<oplus>\<^sub>2 p = \<zero>\<^sub>2"
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proof -
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  let ?q = "%i. \<ominus> (p i)"
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  from R have closed: "?q \<in> carrier P"
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    by (simp add: UP_def P_def up_a_inv_closed)
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  from R have coeff: "!!n. coeff P ?q n = \<ominus> (coeff P p n)"
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    by (simp add: UP_def P_def up_a_inv_closed)
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  show ?thesis
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  proof
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    show "?q \<oplus>\<^sub>2 p = \<zero>\<^sub>2"
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      by (auto intro!: up_eqI simp add: R closed coeff R.l_neg)
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  qed (rule closed)
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qed
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lemma (in UP_cring) UP_a_comm:
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  assumes R: "p \<in> carrier P" "q \<in> carrier P"
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  shows "p \<oplus>\<^sub>2 q = q \<oplus>\<^sub>2 p"
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  by (rule up_eqI, simp add: a_comm R, simp_all add: R)
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ML_setup {*
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  simpset_ref() := simpset() setsubgoaler asm_full_simp_tac;
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*}
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lemma (in UP_cring) UP_m_assoc:
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  assumes R: "p \<in> carrier P" "q \<in> carrier P" "r \<in> carrier P"
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  shows "(p \<otimes>\<^sub>2 q) \<otimes>\<^sub>2 r = p \<otimes>\<^sub>2 (q \<otimes>\<^sub>2 r)"
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proof (rule up_eqI)
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  fix n
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  {
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    fix k and a b c :: "nat=>'a"
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    assume R: "a \<in> UNIV -> carrier R" "b \<in> UNIV -> carrier R"
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      "c \<in> UNIV -> carrier R"
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    then have "k <= n ==>
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      finsum R (%j. finsum R (%i. a i \<otimes> b (j-i)) {..j} \<otimes> c (n-j)) {..k} =
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      finsum R (%j. a j \<otimes> finsum R (%i. b i \<otimes> c (n-j-i)) {..k-j}) {..k}"
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      (is "_ ==> ?eq k")
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    proof (induct k)
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      case 0 then show ?case by (simp add: Pi_def m_assoc)
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    next
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      case (Suc k)
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      then have "k <= n" by arith
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      then have "?eq k" by (rule Suc)
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      with R show ?case
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	by (simp cong: finsum_cong
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             add: Suc_diff_le Pi_def l_distr r_distr m_assoc)
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          (simp cong: finsum_cong add: Pi_def a_ac finsum_ldistr m_assoc)
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   323
    qed
ballarin@13940
   324
  }
ballarin@13940
   325
  with R show "coeff P ((p \<otimes>\<^sub>2 q) \<otimes>\<^sub>2 r) n = coeff P (p \<otimes>\<^sub>2 (q \<otimes>\<^sub>2 r)) n"
ballarin@13940
   326
    by (simp add: Pi_def)
ballarin@13940
   327
qed (simp_all add: R)
ballarin@13940
   328
ballarin@13940
   329
ML_setup {*
wenzelm@14590
   330
  simpset_ref() := simpset() setsubgoaler asm_simp_tac;
wenzelm@14590
   331
*}
ballarin@13940
   332
ballarin@13940
   333
lemma (in UP_cring) UP_l_one [simp]:
ballarin@13940
   334
  assumes R: "p \<in> carrier P"
ballarin@13940
   335
  shows "\<one>\<^sub>2 \<otimes>\<^sub>2 p = p"
ballarin@13940
   336
proof (rule up_eqI)
ballarin@13940
   337
  fix n
ballarin@13940
   338
  show "coeff P (\<one>\<^sub>2 \<otimes>\<^sub>2 p) n = coeff P p n"
ballarin@13940
   339
  proof (cases n)
ballarin@13940
   340
    case 0 with R show ?thesis by simp
ballarin@13940
   341
  next
ballarin@13940
   342
    case Suc with R show ?thesis
ballarin@13940
   343
      by (simp del: finsum_Suc add: finsum_Suc2 Pi_def)
ballarin@13940
   344
  qed
ballarin@13940
   345
qed (simp_all add: R)
ballarin@13940
   346
ballarin@13940
   347
lemma (in UP_cring) UP_l_distr:
ballarin@13940
   348
  assumes R: "p \<in> carrier P" "q \<in> carrier P" "r \<in> carrier P"
ballarin@13940
   349
  shows "(p \<oplus>\<^sub>2 q) \<otimes>\<^sub>2 r = (p \<otimes>\<^sub>2 r) \<oplus>\<^sub>2 (q \<otimes>\<^sub>2 r)"
ballarin@13940
   350
  by (rule up_eqI) (simp add: l_distr R Pi_def, simp_all add: R)
ballarin@13940
   351
ballarin@13940
   352
lemma (in UP_cring) UP_m_comm:
ballarin@13940
   353
  assumes R: "p \<in> carrier P" "q \<in> carrier P"
ballarin@13940
   354
  shows "p \<otimes>\<^sub>2 q = q \<otimes>\<^sub>2 p"
ballarin@13940
   355
proof (rule up_eqI)
ballarin@13940
   356
  fix n 
ballarin@13940
   357
  {
ballarin@13940
   358
    fix k and a b :: "nat=>'a"
ballarin@13940
   359
    assume R: "a \<in> UNIV -> carrier R" "b \<in> UNIV -> carrier R"
ballarin@13940
   360
    then have "k <= n ==> 
ballarin@13940
   361
      finsum R (%i. a i \<otimes> b (n-i)) {..k} =
ballarin@13940
   362
      finsum R (%i. a (k-i) \<otimes> b (i+n-k)) {..k}"
ballarin@13940
   363
      (is "_ ==> ?eq k")
ballarin@13940
   364
    proof (induct k)
ballarin@13940
   365
      case 0 then show ?case by (simp add: Pi_def)
ballarin@13940
   366
    next
ballarin@13940
   367
      case (Suc k) then show ?case
ballarin@13940
   368
	by (subst finsum_Suc2) (simp add: Pi_def a_comm)+
ballarin@13940
   369
    qed
ballarin@13940
   370
  }
ballarin@13940
   371
  note l = this
ballarin@13940
   372
  from R show "coeff P (p \<otimes>\<^sub>2 q) n =  coeff P (q \<otimes>\<^sub>2 p) n"
ballarin@13940
   373
    apply (simp add: Pi_def)
ballarin@13940
   374
    apply (subst l)
ballarin@13940
   375
    apply (auto simp add: Pi_def)
ballarin@13940
   376
    apply (simp add: m_comm)
ballarin@13940
   377
    done
ballarin@13940
   378
qed (simp_all add: R)
ballarin@13940
   379
ballarin@13940
   380
theorem (in UP_cring) UP_cring:
ballarin@13940
   381
  "cring P"
ballarin@13940
   382
  by (auto intro!: cringI abelian_groupI comm_monoidI UP_a_assoc UP_l_zero
ballarin@13940
   383
    UP_l_neg_ex UP_a_comm UP_m_assoc UP_l_one UP_m_comm UP_l_distr)
ballarin@13940
   384
ballarin@14399
   385
lemma (in UP_cring) UP_ring:  (* preliminary *)
ballarin@14399
   386
  "ring P"
ballarin@14399
   387
  by (auto intro: ring.intro cring.axioms UP_cring)
ballarin@14399
   388
ballarin@13940
   389
lemma (in UP_cring) UP_a_inv_closed [intro, simp]:
ballarin@13940
   390
  "p \<in> carrier P ==> \<ominus>\<^sub>2 p \<in> carrier P"
ballarin@13940
   391
  by (rule abelian_group.a_inv_closed
ballarin@14399
   392
    [OF ring.is_abelian_group [OF UP_ring]])
ballarin@13940
   393
ballarin@13940
   394
lemma (in UP_cring) coeff_a_inv [simp]:
ballarin@13940
   395
  assumes R: "p \<in> carrier P"
ballarin@13940
   396
  shows "coeff P (\<ominus>\<^sub>2 p) n = \<ominus> (coeff P p n)"
ballarin@13940
   397
proof -
ballarin@13940
   398
  from R coeff_closed UP_a_inv_closed have
ballarin@13940
   399
    "coeff P (\<ominus>\<^sub>2 p) n = \<ominus> coeff P p n \<oplus> (coeff P p n \<oplus> coeff P (\<ominus>\<^sub>2 p) n)"
ballarin@13940
   400
    by algebra
ballarin@13940
   401
  also from R have "... =  \<ominus> (coeff P p n)"
ballarin@13940
   402
    by (simp del: coeff_add add: coeff_add [THEN sym]
ballarin@14399
   403
      abelian_group.r_neg [OF ring.is_abelian_group [OF UP_ring]])
ballarin@13940
   404
  finally show ?thesis .
ballarin@13940
   405
qed
ballarin@13940
   406
ballarin@13940
   407
text {*
ballarin@13940
   408
  Instantiation of lemmas from @{term cring}.
ballarin@13940
   409
*}
ballarin@13940
   410
ballarin@13940
   411
lemma (in UP_cring) UP_monoid:
ballarin@13940
   412
  "monoid P"
ballarin@13940
   413
  by (fast intro!: cring.is_comm_monoid comm_monoid.axioms monoid.intro
ballarin@13940
   414
    UP_cring)
ballarin@13940
   415
(* TODO: provide cring.is_monoid *)
ballarin@13940
   416
ballarin@13940
   417
lemma (in UP_cring) UP_comm_semigroup:
ballarin@13940
   418
  "comm_semigroup P"
ballarin@13940
   419
  by (fast intro!: cring.is_comm_monoid comm_monoid.axioms comm_semigroup.intro
ballarin@13940
   420
    UP_cring)
ballarin@13940
   421
ballarin@13940
   422
lemma (in UP_cring) UP_comm_monoid:
ballarin@13940
   423
  "comm_monoid P"
ballarin@13940
   424
  by (fast intro!: cring.is_comm_monoid UP_cring)
ballarin@13940
   425
ballarin@13940
   426
lemma (in UP_cring) UP_abelian_monoid:
ballarin@13940
   427
  "abelian_monoid P"
ballarin@14399
   428
  by (fast intro!: abelian_group.axioms ring.is_abelian_group UP_ring)
ballarin@13940
   429
ballarin@13940
   430
lemma (in UP_cring) UP_abelian_group:
ballarin@13940
   431
  "abelian_group P"
ballarin@14399
   432
  by (fast intro!: ring.is_abelian_group UP_ring)
ballarin@13940
   433
ballarin@13940
   434
lemmas (in UP_cring) UP_r_one [simp] =
ballarin@13940
   435
  monoid.r_one [OF UP_monoid]
ballarin@13940
   436
ballarin@13940
   437
lemmas (in UP_cring) UP_nat_pow_closed [intro, simp] =
ballarin@13940
   438
  monoid.nat_pow_closed [OF UP_monoid]
ballarin@13940
   439
ballarin@13940
   440
lemmas (in UP_cring) UP_nat_pow_0 [simp] =
ballarin@13940
   441
  monoid.nat_pow_0 [OF UP_monoid]
ballarin@13940
   442
ballarin@13940
   443
lemmas (in UP_cring) UP_nat_pow_Suc [simp] =
ballarin@13940
   444
  monoid.nat_pow_Suc [OF UP_monoid]
ballarin@13940
   445
ballarin@13940
   446
lemmas (in UP_cring) UP_nat_pow_one [simp] =
ballarin@13940
   447
  monoid.nat_pow_one [OF UP_monoid]
ballarin@13940
   448
ballarin@13940
   449
lemmas (in UP_cring) UP_nat_pow_mult =
ballarin@13940
   450
  monoid.nat_pow_mult [OF UP_monoid]
ballarin@13940
   451
ballarin@13940
   452
lemmas (in UP_cring) UP_nat_pow_pow =
ballarin@13940
   453
  monoid.nat_pow_pow [OF UP_monoid]
ballarin@13940
   454
ballarin@13940
   455
lemmas (in UP_cring) UP_m_lcomm =
ballarin@13940
   456
  comm_semigroup.m_lcomm [OF UP_comm_semigroup]
ballarin@13940
   457
ballarin@13940
   458
lemmas (in UP_cring) UP_m_ac = UP_m_assoc UP_m_comm UP_m_lcomm
ballarin@13940
   459
ballarin@13940
   460
lemmas (in UP_cring) UP_nat_pow_distr =
ballarin@13940
   461
  comm_monoid.nat_pow_distr [OF UP_comm_monoid]
ballarin@13940
   462
ballarin@13940
   463
lemmas (in UP_cring) UP_a_lcomm = abelian_monoid.a_lcomm [OF UP_abelian_monoid]
ballarin@13940
   464
ballarin@13940
   465
lemmas (in UP_cring) UP_r_zero [simp] =
ballarin@13940
   466
  abelian_monoid.r_zero [OF UP_abelian_monoid]
ballarin@13940
   467
ballarin@13940
   468
lemmas (in UP_cring) UP_a_ac = UP_a_assoc UP_a_comm UP_a_lcomm
ballarin@13940
   469
ballarin@13940
   470
lemmas (in UP_cring) UP_finsum_empty [simp] =
ballarin@13940
   471
  abelian_monoid.finsum_empty [OF UP_abelian_monoid]
ballarin@13940
   472
ballarin@13940
   473
lemmas (in UP_cring) UP_finsum_insert [simp] =
ballarin@13940
   474
  abelian_monoid.finsum_insert [OF UP_abelian_monoid]
ballarin@13940
   475
ballarin@13940
   476
lemmas (in UP_cring) UP_finsum_zero [simp] =
ballarin@13940
   477
  abelian_monoid.finsum_zero [OF UP_abelian_monoid]
ballarin@13940
   478
ballarin@13940
   479
lemmas (in UP_cring) UP_finsum_closed [simp] =
ballarin@13940
   480
  abelian_monoid.finsum_closed [OF UP_abelian_monoid]
ballarin@13940
   481
ballarin@13940
   482
lemmas (in UP_cring) UP_finsum_Un_Int =
ballarin@13940
   483
  abelian_monoid.finsum_Un_Int [OF UP_abelian_monoid]
ballarin@13940
   484
ballarin@13940
   485
lemmas (in UP_cring) UP_finsum_Un_disjoint =
ballarin@13940
   486
  abelian_monoid.finsum_Un_disjoint [OF UP_abelian_monoid]
ballarin@13940
   487
ballarin@13940
   488
lemmas (in UP_cring) UP_finsum_addf =
ballarin@13940
   489
  abelian_monoid.finsum_addf [OF UP_abelian_monoid]
ballarin@13940
   490
ballarin@13940
   491
lemmas (in UP_cring) UP_finsum_cong' =
ballarin@13940
   492
  abelian_monoid.finsum_cong' [OF UP_abelian_monoid]
ballarin@13940
   493
ballarin@13940
   494
lemmas (in UP_cring) UP_finsum_0 [simp] =
ballarin@13940
   495
  abelian_monoid.finsum_0 [OF UP_abelian_monoid]
ballarin@13940
   496
ballarin@13940
   497
lemmas (in UP_cring) UP_finsum_Suc [simp] =
ballarin@13940
   498
  abelian_monoid.finsum_Suc [OF UP_abelian_monoid]
ballarin@13940
   499
ballarin@13940
   500
lemmas (in UP_cring) UP_finsum_Suc2 =
ballarin@13940
   501
  abelian_monoid.finsum_Suc2 [OF UP_abelian_monoid]
ballarin@13940
   502
ballarin@13940
   503
lemmas (in UP_cring) UP_finsum_add [simp] =
ballarin@13940
   504
  abelian_monoid.finsum_add [OF UP_abelian_monoid]
ballarin@13940
   505
ballarin@13940
   506
lemmas (in UP_cring) UP_finsum_cong =
ballarin@13940
   507
  abelian_monoid.finsum_cong [OF UP_abelian_monoid]
ballarin@13940
   508
ballarin@13940
   509
lemmas (in UP_cring) UP_minus_closed [intro, simp] =
ballarin@13940
   510
  abelian_group.minus_closed [OF UP_abelian_group]
ballarin@13940
   511
ballarin@13940
   512
lemmas (in UP_cring) UP_a_l_cancel [simp] =
ballarin@13940
   513
  abelian_group.a_l_cancel [OF UP_abelian_group]
ballarin@13940
   514
ballarin@13940
   515
lemmas (in UP_cring) UP_a_r_cancel [simp] =
ballarin@13940
   516
  abelian_group.a_r_cancel [OF UP_abelian_group]
ballarin@13940
   517
ballarin@13940
   518
lemmas (in UP_cring) UP_l_neg =
ballarin@13940
   519
  abelian_group.l_neg [OF UP_abelian_group]
ballarin@13940
   520
ballarin@13940
   521
lemmas (in UP_cring) UP_r_neg =
ballarin@13940
   522
  abelian_group.r_neg [OF UP_abelian_group]
ballarin@13940
   523
ballarin@13940
   524
lemmas (in UP_cring) UP_minus_zero [simp] =
ballarin@13940
   525
  abelian_group.minus_zero [OF UP_abelian_group]
ballarin@13940
   526
ballarin@13940
   527
lemmas (in UP_cring) UP_minus_minus [simp] =
ballarin@13940
   528
  abelian_group.minus_minus [OF UP_abelian_group]
ballarin@13940
   529
ballarin@13940
   530
lemmas (in UP_cring) UP_minus_add =
ballarin@13940
   531
  abelian_group.minus_add [OF UP_abelian_group]
ballarin@13940
   532
ballarin@13940
   533
lemmas (in UP_cring) UP_r_neg2 =
ballarin@13940
   534
  abelian_group.r_neg2 [OF UP_abelian_group]
ballarin@13940
   535
ballarin@13940
   536
lemmas (in UP_cring) UP_r_neg1 =
ballarin@13940
   537
  abelian_group.r_neg1 [OF UP_abelian_group]
ballarin@13940
   538
ballarin@13940
   539
lemmas (in UP_cring) UP_r_distr =
ballarin@14399
   540
  ring.r_distr [OF UP_ring]
ballarin@13940
   541
ballarin@13940
   542
lemmas (in UP_cring) UP_l_null [simp] =
ballarin@14399
   543
  ring.l_null [OF UP_ring]
ballarin@13940
   544
ballarin@13940
   545
lemmas (in UP_cring) UP_r_null [simp] =
ballarin@14399
   546
  ring.r_null [OF UP_ring]
ballarin@13940
   547
ballarin@13940
   548
lemmas (in UP_cring) UP_l_minus =
ballarin@14399
   549
  ring.l_minus [OF UP_ring]
ballarin@13940
   550
ballarin@13940
   551
lemmas (in UP_cring) UP_r_minus =
ballarin@14399
   552
  ring.r_minus [OF UP_ring]
ballarin@13940
   553
ballarin@13940
   554
lemmas (in UP_cring) UP_finsum_ldistr =
ballarin@13940
   555
  cring.finsum_ldistr [OF UP_cring]
ballarin@13940
   556
ballarin@13940
   557
lemmas (in UP_cring) UP_finsum_rdistr =
ballarin@13940
   558
  cring.finsum_rdistr [OF UP_cring]
ballarin@13940
   559
ballarin@13940
   560
subsection {* Polynomials form an Algebra *}
ballarin@13940
   561
ballarin@13940
   562
lemma (in UP_cring) UP_smult_l_distr:
ballarin@13940
   563
  "[| a \<in> carrier R; b \<in> carrier R; p \<in> carrier P |] ==>
ballarin@13940
   564
  (a \<oplus> b) \<odot>\<^sub>2 p = a \<odot>\<^sub>2 p \<oplus>\<^sub>2 b \<odot>\<^sub>2 p"
ballarin@13940
   565
  by (rule up_eqI) (simp_all add: R.l_distr)
ballarin@13940
   566
ballarin@13940
   567
lemma (in UP_cring) UP_smult_r_distr:
ballarin@13940
   568
  "[| a \<in> carrier R; p \<in> carrier P; q \<in> carrier P |] ==>
ballarin@13940
   569
  a \<odot>\<^sub>2 (p \<oplus>\<^sub>2 q) = a \<odot>\<^sub>2 p \<oplus>\<^sub>2 a \<odot>\<^sub>2 q"
ballarin@13940
   570
  by (rule up_eqI) (simp_all add: R.r_distr)
ballarin@13940
   571
ballarin@13940
   572
lemma (in UP_cring) UP_smult_assoc1:
ballarin@13940
   573
      "[| a \<in> carrier R; b \<in> carrier R; p \<in> carrier P |] ==>
ballarin@13940
   574
      (a \<otimes> b) \<odot>\<^sub>2 p = a \<odot>\<^sub>2 (b \<odot>\<^sub>2 p)"
ballarin@13940
   575
  by (rule up_eqI) (simp_all add: R.m_assoc)
ballarin@13940
   576
ballarin@13940
   577
lemma (in UP_cring) UP_smult_one [simp]:
ballarin@13940
   578
      "p \<in> carrier P ==> \<one> \<odot>\<^sub>2 p = p"
ballarin@13940
   579
  by (rule up_eqI) simp_all
ballarin@13940
   580
ballarin@13940
   581
lemma (in UP_cring) UP_smult_assoc2:
ballarin@13940
   582
  "[| a \<in> carrier R; p \<in> carrier P; q \<in> carrier P |] ==>
ballarin@13940
   583
  (a \<odot>\<^sub>2 p) \<otimes>\<^sub>2 q = a \<odot>\<^sub>2 (p \<otimes>\<^sub>2 q)"
ballarin@13940
   584
  by (rule up_eqI) (simp_all add: R.finsum_rdistr R.m_assoc Pi_def)
ballarin@13940
   585
ballarin@13940
   586
text {*
ballarin@13940
   587
  Instantiation of lemmas from @{term algebra}.
ballarin@13940
   588
*}
ballarin@13940
   589
ballarin@13940
   590
(* TODO: move to CRing.thy, really a fact missing from the locales package *)
ballarin@13940
   591
ballarin@13940
   592
lemma (in cring) cring:
ballarin@13940
   593
  "cring R"
ballarin@13940
   594
  by (fast intro: cring.intro prems)
ballarin@13940
   595
ballarin@13940
   596
lemma (in UP_cring) UP_algebra:
ballarin@13940
   597
  "algebra R P"
ballarin@13940
   598
  by (auto intro: algebraI cring UP_cring UP_smult_l_distr UP_smult_r_distr
ballarin@13940
   599
    UP_smult_assoc1 UP_smult_assoc2)
ballarin@13940
   600
ballarin@13940
   601
lemmas (in UP_cring) UP_smult_l_null [simp] =
ballarin@13940
   602
  algebra.smult_l_null [OF UP_algebra]
ballarin@13940
   603
ballarin@13940
   604
lemmas (in UP_cring) UP_smult_r_null [simp] =
ballarin@13940
   605
  algebra.smult_r_null [OF UP_algebra]
ballarin@13940
   606
ballarin@13940
   607
lemmas (in UP_cring) UP_smult_l_minus =
ballarin@13940
   608
  algebra.smult_l_minus [OF UP_algebra]
ballarin@13940
   609
ballarin@13940
   610
lemmas (in UP_cring) UP_smult_r_minus =
ballarin@13940
   611
  algebra.smult_r_minus [OF UP_algebra]
ballarin@13940
   612
ballarin@13949
   613
subsection {* Further lemmas involving monomials *}
ballarin@13940
   614
ballarin@13940
   615
lemma (in UP_cring) monom_zero [simp]:
ballarin@13940
   616
  "monom P \<zero> n = \<zero>\<^sub>2"
ballarin@13940
   617
  by (simp add: UP_def P_def)
ballarin@13940
   618
ballarin@13940
   619
ML_setup {*
wenzelm@14590
   620
  simpset_ref() := simpset() setsubgoaler asm_full_simp_tac;
wenzelm@14590
   621
*}
ballarin@13940
   622
ballarin@13940
   623
lemma (in UP_cring) monom_mult_is_smult:
ballarin@13940
   624
  assumes R: "a \<in> carrier R" "p \<in> carrier P"
ballarin@13940
   625
  shows "monom P a 0 \<otimes>\<^sub>2 p = a \<odot>\<^sub>2 p"
ballarin@13940
   626
proof (rule up_eqI)
ballarin@13940
   627
  fix n
ballarin@13940
   628
  have "coeff P (p \<otimes>\<^sub>2 monom P a 0) n = coeff P (a \<odot>\<^sub>2 p) n"
ballarin@13940
   629
  proof (cases n)
ballarin@13940
   630
    case 0 with R show ?thesis by (simp add: R.m_comm)
ballarin@13940
   631
  next
ballarin@13940
   632
    case Suc with R show ?thesis
ballarin@13940
   633
      by (simp cong: finsum_cong add: R.r_null Pi_def)
ballarin@13940
   634
        (simp add: m_comm)
ballarin@13940
   635
  qed
ballarin@13940
   636
  with R show "coeff P (monom P a 0 \<otimes>\<^sub>2 p) n = coeff P (a \<odot>\<^sub>2 p) n"
ballarin@13940
   637
    by (simp add: UP_m_comm)
ballarin@13940
   638
qed (simp_all add: R)
ballarin@13940
   639
ballarin@13940
   640
ML_setup {*
wenzelm@14590
   641
  simpset_ref() := simpset() setsubgoaler asm_simp_tac;
wenzelm@14590
   642
*}
ballarin@13940
   643
ballarin@13940
   644
lemma (in UP_cring) monom_add [simp]:
ballarin@13940
   645
  "[| a \<in> carrier R; b \<in> carrier R |] ==>
ballarin@13940
   646
  monom P (a \<oplus> b) n = monom P a n \<oplus>\<^sub>2 monom P b n"
ballarin@13940
   647
  by (rule up_eqI) simp_all
ballarin@13940
   648
ballarin@13940
   649
ML_setup {*
wenzelm@14590
   650
  simpset_ref() := simpset() setsubgoaler asm_full_simp_tac;
wenzelm@14590
   651
*}
ballarin@13940
   652
ballarin@13940
   653
lemma (in UP_cring) monom_one_Suc:
ballarin@13940
   654
  "monom P \<one> (Suc n) = monom P \<one> n \<otimes>\<^sub>2 monom P \<one> 1"
ballarin@13940
   655
proof (rule up_eqI)
ballarin@13940
   656
  fix k
ballarin@13940
   657
  show "coeff P (monom P \<one> (Suc n)) k = coeff P (monom P \<one> n \<otimes>\<^sub>2 monom P \<one> 1) k"
ballarin@13940
   658
  proof (cases "k = Suc n")
ballarin@13940
   659
    case True show ?thesis
ballarin@13940
   660
    proof -
ballarin@13940
   661
      from True have less_add_diff: 
ballarin@13940
   662
	"!!i. [| n < i; i <= n + m |] ==> n + m - i < m" by arith
ballarin@13940
   663
      from True have "coeff P (monom P \<one> (Suc n)) k = \<one>" by simp
ballarin@13940
   664
      also from True
ballarin@13940
   665
      have "... = finsum R (%i. coeff P (monom P \<one> n) i \<otimes>
ballarin@13940
   666
	coeff P (monom P \<one> 1) (k - i)) ({..n(} Un {n})"
ballarin@13940
   667
	by (simp cong: finsum_cong add: finsum_Un_disjoint Pi_def)
ballarin@13940
   668
      also have "... = finsum R (%i. coeff P (monom P \<one> n) i \<otimes>
ballarin@13940
   669
	coeff P (monom P \<one> 1) (k - i)) {..n}"
ballarin@13940
   670
	by (simp only: ivl_disj_un_singleton)
ballarin@13940
   671
      also from True have "... = finsum R (%i. coeff P (monom P \<one> n) i \<otimes>
ballarin@13940
   672
	coeff P (monom P \<one> 1) (k - i)) ({..n} Un {)n..k})"
ballarin@13940
   673
	by (simp cong: finsum_cong add: finsum_Un_disjoint ivl_disj_int_one
ballarin@13940
   674
	  order_less_imp_not_eq Pi_def)
ballarin@13940
   675
      also from True have "... = coeff P (monom P \<one> n \<otimes>\<^sub>2 monom P \<one> 1) k"
ballarin@13940
   676
	by (simp add: ivl_disj_un_one)
ballarin@13940
   677
      finally show ?thesis .
ballarin@13940
   678
    qed
ballarin@13940
   679
  next
ballarin@13940
   680
    case False
ballarin@13940
   681
    note neq = False
ballarin@13940
   682
    let ?s =
ballarin@13940
   683
      "(\<lambda>i. (if n = i then \<one> else \<zero>) \<otimes> (if Suc 0 = k - i then \<one> else \<zero>))"
ballarin@13940
   684
    from neq have "coeff P (monom P \<one> (Suc n)) k = \<zero>" by simp
ballarin@13940
   685
    also have "... = finsum R ?s {..k}"
ballarin@13940
   686
    proof -
ballarin@13940
   687
      have f1: "finsum R ?s {..n(} = \<zero>" by (simp cong: finsum_cong add: Pi_def)
ballarin@13940
   688
      from neq have f2: "finsum R ?s {n} = \<zero>"
ballarin@13940
   689
	by (simp cong: finsum_cong add: Pi_def) arith
ballarin@13940
   690
      have f3: "n < k ==> finsum R ?s {)n..k} = \<zero>"
ballarin@13940
   691
	by (simp cong: finsum_cong add: order_less_imp_not_eq Pi_def)
ballarin@13940
   692
      show ?thesis
ballarin@13940
   693
      proof (cases "k < n")
ballarin@13940
   694
	case True then show ?thesis by (simp cong: finsum_cong add: Pi_def)
ballarin@13940
   695
      next
ballarin@13940
   696
	case False then have n_le_k: "n <= k" by arith
ballarin@13940
   697
	show ?thesis
ballarin@13940
   698
	proof (cases "n = k")
ballarin@13940
   699
	  case True
ballarin@13940
   700
	  then have "\<zero> = finsum R ?s ({..n(} \<union> {n})"
ballarin@13940
   701
	    by (simp cong: finsum_cong add: finsum_Un_disjoint
ballarin@13940
   702
	      ivl_disj_int_singleton Pi_def)
ballarin@13940
   703
	  also from True have "... = finsum R ?s {..k}"
ballarin@13940
   704
	    by (simp only: ivl_disj_un_singleton)
ballarin@13940
   705
	  finally show ?thesis .
ballarin@13940
   706
	next
ballarin@13940
   707
	  case False with n_le_k have n_less_k: "n < k" by arith
ballarin@13940
   708
	  with neq have "\<zero> = finsum R ?s ({..n(} \<union> {n})"
ballarin@13940
   709
	    by (simp add: finsum_Un_disjoint f1 f2
ballarin@13940
   710
	      ivl_disj_int_singleton Pi_def del: Un_insert_right)
ballarin@13940
   711
	  also have "... = finsum R ?s {..n}"
ballarin@13940
   712
	    by (simp only: ivl_disj_un_singleton)
ballarin@13940
   713
	  also from n_less_k neq have "... = finsum R ?s ({..n} \<union> {)n..k})"
ballarin@13940
   714
	    by (simp add: finsum_Un_disjoint f3 ivl_disj_int_one Pi_def)
ballarin@13940
   715
	  also from n_less_k have "... = finsum R ?s {..k}"
ballarin@13940
   716
	    by (simp only: ivl_disj_un_one)
ballarin@13940
   717
	  finally show ?thesis .
ballarin@13940
   718
	qed
ballarin@13940
   719
      qed
ballarin@13940
   720
    qed
ballarin@13940
   721
    also have "... = coeff P (monom P \<one> n \<otimes>\<^sub>2 monom P \<one> 1) k" by simp
ballarin@13940
   722
    finally show ?thesis .
ballarin@13940
   723
  qed
ballarin@13940
   724
qed (simp_all)
ballarin@13940
   725
ballarin@13940
   726
ML_setup {*
wenzelm@14590
   727
  simpset_ref() := simpset() setsubgoaler asm_simp_tac;
wenzelm@14590
   728
*}
ballarin@13940
   729
ballarin@13940
   730
lemma (in UP_cring) monom_mult_smult:
ballarin@13940
   731
  "[| a \<in> carrier R; b \<in> carrier R |] ==> monom P (a \<otimes> b) n = a \<odot>\<^sub>2 monom P b n"
ballarin@13940
   732
  by (rule up_eqI) simp_all
ballarin@13940
   733
ballarin@13940
   734
lemma (in UP_cring) monom_one [simp]:
ballarin@13940
   735
  "monom P \<one> 0 = \<one>\<^sub>2"
ballarin@13940
   736
  by (rule up_eqI) simp_all
ballarin@13940
   737
ballarin@13940
   738
lemma (in UP_cring) monom_one_mult:
ballarin@13940
   739
  "monom P \<one> (n + m) = monom P \<one> n \<otimes>\<^sub>2 monom P \<one> m"
ballarin@13940
   740
proof (induct n)
ballarin@13940
   741
  case 0 show ?case by simp
ballarin@13940
   742
next
ballarin@13940
   743
  case Suc then show ?case
ballarin@13940
   744
    by (simp only: add_Suc monom_one_Suc) (simp add: UP_m_ac)
ballarin@13940
   745
qed
ballarin@13940
   746
ballarin@13940
   747
lemma (in UP_cring) monom_mult [simp]:
ballarin@13940
   748
  assumes R: "a \<in> carrier R" "b \<in> carrier R"
ballarin@13940
   749
  shows "monom P (a \<otimes> b) (n + m) = monom P a n \<otimes>\<^sub>2 monom P b m"
ballarin@13940
   750
proof -
ballarin@13940
   751
  from R have "monom P (a \<otimes> b) (n + m) = monom P (a \<otimes> b \<otimes> \<one>) (n + m)" by simp
ballarin@13940
   752
  also from R have "... = a \<otimes> b \<odot>\<^sub>2 monom P \<one> (n + m)"
ballarin@13940
   753
    by (simp add: monom_mult_smult del: r_one)
ballarin@13940
   754
  also have "... = a \<otimes> b \<odot>\<^sub>2 (monom P \<one> n \<otimes>\<^sub>2 monom P \<one> m)"
ballarin@13940
   755
    by (simp only: monom_one_mult)
ballarin@13940
   756
  also from R have "... = a \<odot>\<^sub>2 (b \<odot>\<^sub>2 (monom P \<one> n \<otimes>\<^sub>2 monom P \<one> m))"
ballarin@13940
   757
    by (simp add: UP_smult_assoc1)
ballarin@13940
   758
  also from R have "... = a \<odot>\<^sub>2 (b \<odot>\<^sub>2 (monom P \<one> m \<otimes>\<^sub>2 monom P \<one> n))"
ballarin@13940
   759
    by (simp add: UP_m_comm)
ballarin@13940
   760
  also from R have "... = a \<odot>\<^sub>2 ((b \<odot>\<^sub>2 monom P \<one> m) \<otimes>\<^sub>2 monom P \<one> n)"
ballarin@13940
   761
    by (simp add: UP_smult_assoc2)
ballarin@13940
   762
  also from R have "... = a \<odot>\<^sub>2 (monom P \<one> n \<otimes>\<^sub>2 (b \<odot>\<^sub>2 monom P \<one> m))"
ballarin@13940
   763
    by (simp add: UP_m_comm)
ballarin@13940
   764
  also from R have "... = (a \<odot>\<^sub>2 monom P \<one> n) \<otimes>\<^sub>2 (b \<odot>\<^sub>2 monom P \<one> m)"
ballarin@13940
   765
    by (simp add: UP_smult_assoc2)
ballarin@13940
   766
  also from R have "... = monom P (a \<otimes> \<one>) n \<otimes>\<^sub>2 monom P (b \<otimes> \<one>) m"
ballarin@13940
   767
    by (simp add: monom_mult_smult del: r_one)
ballarin@13940
   768
  also from R have "... = monom P a n \<otimes>\<^sub>2 monom P b m" by simp
ballarin@13940
   769
  finally show ?thesis .
ballarin@13940
   770
qed
ballarin@13940
   771
ballarin@13940
   772
lemma (in UP_cring) monom_a_inv [simp]:
ballarin@13940
   773
  "a \<in> carrier R ==> monom P (\<ominus> a) n = \<ominus>\<^sub>2 monom P a n"
ballarin@13940
   774
  by (rule up_eqI) simp_all
ballarin@13940
   775
ballarin@13940
   776
lemma (in UP_cring) monom_inj:
ballarin@13940
   777
  "inj_on (%a. monom P a n) (carrier R)"
ballarin@13940
   778
proof (rule inj_onI)
ballarin@13940
   779
  fix x y
ballarin@13940
   780
  assume R: "x \<in> carrier R" "y \<in> carrier R" and eq: "monom P x n = monom P y n"
ballarin@13940
   781
  then have "coeff P (monom P x n) n = coeff P (monom P y n) n" by simp
ballarin@13940
   782
  with R show "x = y" by simp
ballarin@13940
   783
qed
ballarin@13940
   784
ballarin@13949
   785
subsection {* The degree function *}
ballarin@13940
   786
wenzelm@14651
   787
constdefs (structure R)
wenzelm@14651
   788
  deg :: "[_, nat => 'a] => nat"
wenzelm@14651
   789
  "deg R p == LEAST n. bound \<zero> n (coeff (UP R) p)"
ballarin@13940
   790
ballarin@13940
   791
lemma (in UP_cring) deg_aboveI:
ballarin@13940
   792
  "[| (!!m. n < m ==> coeff P p m = \<zero>); p \<in> carrier P |] ==> deg R p <= n" 
ballarin@13940
   793
  by (unfold deg_def P_def) (fast intro: Least_le)
ballarin@13940
   794
(*
ballarin@13940
   795
lemma coeff_bound_ex: "EX n. bound n (coeff p)"
ballarin@13940
   796
proof -
ballarin@13940
   797
  have "(%n. coeff p n) : UP" by (simp add: coeff_def Rep_UP)
ballarin@13940
   798
  then obtain n where "bound n (coeff p)" by (unfold UP_def) fast
ballarin@13940
   799
  then show ?thesis ..
ballarin@13940
   800
qed
ballarin@13940
   801
  
ballarin@13940
   802
lemma bound_coeff_obtain:
ballarin@13940
   803
  assumes prem: "(!!n. bound n (coeff p) ==> P)" shows "P"
ballarin@13940
   804
proof -
ballarin@13940
   805
  have "(%n. coeff p n) : UP" by (simp add: coeff_def Rep_UP)
ballarin@13940
   806
  then obtain n where "bound n (coeff p)" by (unfold UP_def) fast
ballarin@13940
   807
  with prem show P .
ballarin@13940
   808
qed
ballarin@13940
   809
*)
ballarin@13940
   810
lemma (in UP_cring) deg_aboveD:
ballarin@13940
   811
  "[| deg R p < m; p \<in> carrier P |] ==> coeff P p m = \<zero>"
ballarin@13940
   812
proof -
ballarin@13940
   813
  assume R: "p \<in> carrier P" and "deg R p < m"
ballarin@13940
   814
  from R obtain n where "bound \<zero> n (coeff P p)" 
ballarin@13940
   815
    by (auto simp add: UP_def P_def)
ballarin@13940
   816
  then have "bound \<zero> (deg R p) (coeff P p)"
ballarin@13940
   817
    by (auto simp: deg_def P_def dest: LeastI)
ballarin@13940
   818
  then show ?thesis by (rule boundD)
ballarin@13940
   819
qed
ballarin@13940
   820
ballarin@13940
   821
lemma (in UP_cring) deg_belowI:
ballarin@13940
   822
  assumes non_zero: "n ~= 0 ==> coeff P p n ~= \<zero>"
ballarin@13940
   823
    and R: "p \<in> carrier P"
ballarin@13940
   824
  shows "n <= deg R p"
ballarin@13940
   825
-- {* Logically, this is a slightly stronger version of 
ballarin@13940
   826
  @{thm [source] deg_aboveD} *}
ballarin@13940
   827
proof (cases "n=0")
ballarin@13940
   828
  case True then show ?thesis by simp
ballarin@13940
   829
next
ballarin@13940
   830
  case False then have "coeff P p n ~= \<zero>" by (rule non_zero)
ballarin@13940
   831
  then have "~ deg R p < n" by (fast dest: deg_aboveD intro: R)
ballarin@13940
   832
  then show ?thesis by arith
ballarin@13940
   833
qed
ballarin@13940
   834
ballarin@13940
   835
lemma (in UP_cring) lcoeff_nonzero_deg:
ballarin@13940
   836
  assumes deg: "deg R p ~= 0" and R: "p \<in> carrier P"
ballarin@13940
   837
  shows "coeff P p (deg R p) ~= \<zero>"
ballarin@13940
   838
proof -
ballarin@13940
   839
  from R obtain m where "deg R p <= m" and m_coeff: "coeff P p m ~= \<zero>"
ballarin@13940
   840
  proof -
ballarin@13940
   841
    have minus: "!!(n::nat) m. n ~= 0 ==> (n - Suc 0 < m) = (n <= m)"
ballarin@13940
   842
      by arith
ballarin@13940
   843
(* TODO: why does proof not work with "1" *)
ballarin@13940
   844
    from deg have "deg R p - 1 < (LEAST n. bound \<zero> n (coeff P p))"
ballarin@13940
   845
      by (unfold deg_def P_def) arith
ballarin@13940
   846
    then have "~ bound \<zero> (deg R p - 1) (coeff P p)" by (rule not_less_Least)
ballarin@13940
   847
    then have "EX m. deg R p - 1 < m & coeff P p m ~= \<zero>"
ballarin@13940
   848
      by (unfold bound_def) fast
ballarin@13940
   849
    then have "EX m. deg R p <= m & coeff P p m ~= \<zero>" by (simp add: deg minus)
ballarin@13940
   850
    then show ?thesis by auto 
ballarin@13940
   851
  qed
ballarin@13940
   852
  with deg_belowI R have "deg R p = m" by fastsimp
ballarin@13940
   853
  with m_coeff show ?thesis by simp
ballarin@13940
   854
qed
ballarin@13940
   855
ballarin@13940
   856
lemma (in UP_cring) lcoeff_nonzero_nonzero:
ballarin@13940
   857
  assumes deg: "deg R p = 0" and nonzero: "p ~= \<zero>\<^sub>2" and R: "p \<in> carrier P"
ballarin@13940
   858
  shows "coeff P p 0 ~= \<zero>"
ballarin@13940
   859
proof -
ballarin@13940
   860
  have "EX m. coeff P p m ~= \<zero>"
ballarin@13940
   861
  proof (rule classical)
ballarin@13940
   862
    assume "~ ?thesis"
ballarin@13940
   863
    with R have "p = \<zero>\<^sub>2" by (auto intro: up_eqI)
ballarin@13940
   864
    with nonzero show ?thesis by contradiction
ballarin@13940
   865
  qed
ballarin@13940
   866
  then obtain m where coeff: "coeff P p m ~= \<zero>" ..
ballarin@13940
   867
  then have "m <= deg R p" by (rule deg_belowI)
ballarin@13940
   868
  then have "m = 0" by (simp add: deg)
ballarin@13940
   869
  with coeff show ?thesis by simp
ballarin@13940
   870
qed
ballarin@13940
   871
ballarin@13940
   872
lemma (in UP_cring) lcoeff_nonzero:
ballarin@13940
   873
  assumes neq: "p ~= \<zero>\<^sub>2" and R: "p \<in> carrier P"
ballarin@13940
   874
  shows "coeff P p (deg R p) ~= \<zero>"
ballarin@13940
   875
proof (cases "deg R p = 0")
ballarin@13940
   876
  case True with neq R show ?thesis by (simp add: lcoeff_nonzero_nonzero)
ballarin@13940
   877
next
ballarin@13940
   878
  case False with neq R show ?thesis by (simp add: lcoeff_nonzero_deg)
ballarin@13940
   879
qed
ballarin@13940
   880
ballarin@13940
   881
lemma (in UP_cring) deg_eqI:
ballarin@13940
   882
  "[| !!m. n < m ==> coeff P p m = \<zero>;
ballarin@13940
   883
      !!n. n ~= 0 ==> coeff P p n ~= \<zero>; p \<in> carrier P |] ==> deg R p = n"
ballarin@13940
   884
by (fast intro: le_anti_sym deg_aboveI deg_belowI)
ballarin@13940
   885
ballarin@13940
   886
(* Degree and polynomial operations *)
ballarin@13940
   887
ballarin@13940
   888
lemma (in UP_cring) deg_add [simp]:
ballarin@13940
   889
  assumes R: "p \<in> carrier P" "q \<in> carrier P"
ballarin@13940
   890
  shows "deg R (p \<oplus>\<^sub>2 q) <= max (deg R p) (deg R q)"
ballarin@13940
   891
proof (cases "deg R p <= deg R q")
ballarin@13940
   892
  case True show ?thesis
ballarin@13940
   893
    by (rule deg_aboveI) (simp_all add: True R deg_aboveD) 
ballarin@13940
   894
next
ballarin@13940
   895
  case False show ?thesis
ballarin@13940
   896
    by (rule deg_aboveI) (simp_all add: False R deg_aboveD)
ballarin@13940
   897
qed
ballarin@13940
   898
ballarin@13940
   899
lemma (in UP_cring) deg_monom_le:
ballarin@13940
   900
  "a \<in> carrier R ==> deg R (monom P a n) <= n"
ballarin@13940
   901
  by (intro deg_aboveI) simp_all
ballarin@13940
   902
ballarin@13940
   903
lemma (in UP_cring) deg_monom [simp]:
ballarin@13940
   904
  "[| a ~= \<zero>; a \<in> carrier R |] ==> deg R (monom P a n) = n"
ballarin@13940
   905
  by (fastsimp intro: le_anti_sym deg_aboveI deg_belowI)
ballarin@13940
   906
ballarin@13940
   907
lemma (in UP_cring) deg_const [simp]:
ballarin@13940
   908
  assumes R: "a \<in> carrier R" shows "deg R (monom P a 0) = 0"
ballarin@13940
   909
proof (rule le_anti_sym)
ballarin@13940
   910
  show "deg R (monom P a 0) <= 0" by (rule deg_aboveI) (simp_all add: R)
ballarin@13940
   911
next
ballarin@13940
   912
  show "0 <= deg R (monom P a 0)" by (rule deg_belowI) (simp_all add: R)
ballarin@13940
   913
qed
ballarin@13940
   914
ballarin@13940
   915
lemma (in UP_cring) deg_zero [simp]:
ballarin@13940
   916
  "deg R \<zero>\<^sub>2 = 0"
ballarin@13940
   917
proof (rule le_anti_sym)
ballarin@13940
   918
  show "deg R \<zero>\<^sub>2 <= 0" by (rule deg_aboveI) simp_all
ballarin@13940
   919
next
ballarin@13940
   920
  show "0 <= deg R \<zero>\<^sub>2" by (rule deg_belowI) simp_all
ballarin@13940
   921
qed
ballarin@13940
   922
ballarin@13940
   923
lemma (in UP_cring) deg_one [simp]:
ballarin@13940
   924
  "deg R \<one>\<^sub>2 = 0"
ballarin@13940
   925
proof (rule le_anti_sym)
ballarin@13940
   926
  show "deg R \<one>\<^sub>2 <= 0" by (rule deg_aboveI) simp_all
ballarin@13940
   927
next
ballarin@13940
   928
  show "0 <= deg R \<one>\<^sub>2" by (rule deg_belowI) simp_all
ballarin@13940
   929
qed
ballarin@13940
   930
ballarin@13940
   931
lemma (in UP_cring) deg_uminus [simp]:
ballarin@13940
   932
  assumes R: "p \<in> carrier P" shows "deg R (\<ominus>\<^sub>2 p) = deg R p"
ballarin@13940
   933
proof (rule le_anti_sym)
ballarin@13940
   934
  show "deg R (\<ominus>\<^sub>2 p) <= deg R p" by (simp add: deg_aboveI deg_aboveD R)
ballarin@13940
   935
next
ballarin@13940
   936
  show "deg R p <= deg R (\<ominus>\<^sub>2 p)" 
ballarin@13940
   937
    by (simp add: deg_belowI lcoeff_nonzero_deg
ballarin@13940
   938
      inj_on_iff [OF a_inv_inj, of _ "\<zero>", simplified] R)
ballarin@13940
   939
qed
ballarin@13940
   940
ballarin@13940
   941
lemma (in UP_domain) deg_smult_ring:
ballarin@13940
   942
  "[| a \<in> carrier R; p \<in> carrier P |] ==>
ballarin@13940
   943
  deg R (a \<odot>\<^sub>2 p) <= (if a = \<zero> then 0 else deg R p)"
ballarin@13940
   944
  by (cases "a = \<zero>") (simp add: deg_aboveI deg_aboveD)+
ballarin@13940
   945
ballarin@13940
   946
lemma (in UP_domain) deg_smult [simp]:
ballarin@13940
   947
  assumes R: "a \<in> carrier R" "p \<in> carrier P"
ballarin@13940
   948
  shows "deg R (a \<odot>\<^sub>2 p) = (if a = \<zero> then 0 else deg R p)"
ballarin@13940
   949
proof (rule le_anti_sym)
ballarin@13940
   950
  show "deg R (a \<odot>\<^sub>2 p) <= (if a = \<zero> then 0 else deg R p)"
ballarin@13940
   951
    by (rule deg_smult_ring)
ballarin@13940
   952
next
ballarin@13940
   953
  show "(if a = \<zero> then 0 else deg R p) <= deg R (a \<odot>\<^sub>2 p)"
ballarin@13940
   954
  proof (cases "a = \<zero>")
ballarin@13940
   955
  qed (simp, simp add: deg_belowI lcoeff_nonzero_deg integral_iff R)
ballarin@13940
   956
qed
ballarin@13940
   957
ballarin@13940
   958
lemma (in UP_cring) deg_mult_cring:
ballarin@13940
   959
  assumes R: "p \<in> carrier P" "q \<in> carrier P"
ballarin@13940
   960
  shows "deg R (p \<otimes>\<^sub>2 q) <= deg R p + deg R q"
ballarin@13940
   961
proof (rule deg_aboveI)
ballarin@13940
   962
  fix m
ballarin@13940
   963
  assume boundm: "deg R p + deg R q < m"
ballarin@13940
   964
  {
ballarin@13940
   965
    fix k i
ballarin@13940
   966
    assume boundk: "deg R p + deg R q < k"
ballarin@13940
   967
    then have "coeff P p i \<otimes> coeff P q (k - i) = \<zero>"
ballarin@13940
   968
    proof (cases "deg R p < i")
ballarin@13940
   969
      case True then show ?thesis by (simp add: deg_aboveD R)
ballarin@13940
   970
    next
ballarin@13940
   971
      case False with boundk have "deg R q < k - i" by arith
ballarin@13940
   972
      then show ?thesis by (simp add: deg_aboveD R)
ballarin@13940
   973
    qed
ballarin@13940
   974
  }
ballarin@13940
   975
  with boundm R show "coeff P (p \<otimes>\<^sub>2 q) m = \<zero>" by simp
ballarin@13940
   976
qed (simp add: R)
ballarin@13940
   977
ballarin@13940
   978
ML_setup {*
wenzelm@14590
   979
  simpset_ref() := simpset() setsubgoaler asm_full_simp_tac;
wenzelm@14590
   980
*}
ballarin@13940
   981
ballarin@13940
   982
lemma (in UP_domain) deg_mult [simp]:
ballarin@13940
   983
  "[| p ~= \<zero>\<^sub>2; q ~= \<zero>\<^sub>2; p \<in> carrier P; q \<in> carrier P |] ==>
ballarin@13940
   984
  deg R (p \<otimes>\<^sub>2 q) = deg R p + deg R q"
ballarin@13940
   985
proof (rule le_anti_sym)
ballarin@13940
   986
  assume "p \<in> carrier P" " q \<in> carrier P"
ballarin@13940
   987
  show "deg R (p \<otimes>\<^sub>2 q) <= deg R p + deg R q" by (rule deg_mult_cring)
ballarin@13940
   988
next
ballarin@13940
   989
  let ?s = "(%i. coeff P p i \<otimes> coeff P q (deg R p + deg R q - i))"
ballarin@13940
   990
  assume R: "p \<in> carrier P" "q \<in> carrier P" and nz: "p ~= \<zero>\<^sub>2" "q ~= \<zero>\<^sub>2"
ballarin@13940
   991
  have less_add_diff: "!!(k::nat) n m. k < n ==> m < n + m - k" by arith
ballarin@13940
   992
  show "deg R p + deg R q <= deg R (p \<otimes>\<^sub>2 q)"
ballarin@13940
   993
  proof (rule deg_belowI, simp add: R)
ballarin@13940
   994
    have "finsum R ?s {.. deg R p + deg R q}
ballarin@13940
   995
      = finsum R ?s ({.. deg R p(} Un {deg R p .. deg R p + deg R q})"
ballarin@13940
   996
      by (simp only: ivl_disj_un_one)
ballarin@13940
   997
    also have "... = finsum R ?s {deg R p .. deg R p + deg R q}"
ballarin@13940
   998
      by (simp cong: finsum_cong add: finsum_Un_disjoint ivl_disj_int_one
ballarin@13940
   999
        deg_aboveD less_add_diff R Pi_def)
ballarin@13940
  1000
    also have "...= finsum R ?s ({deg R p} Un {)deg R p .. deg R p + deg R q})"
ballarin@13940
  1001
      by (simp only: ivl_disj_un_singleton)
ballarin@13940
  1002
    also have "... = coeff P p (deg R p) \<otimes> coeff P q (deg R q)" 
ballarin@13940
  1003
      by (simp cong: finsum_cong add: finsum_Un_disjoint
ballarin@13940
  1004
	ivl_disj_int_singleton deg_aboveD R Pi_def)
ballarin@13940
  1005
    finally have "finsum R ?s {.. deg R p + deg R q} 
ballarin@13940
  1006
      = coeff P p (deg R p) \<otimes> coeff P q (deg R q)" .
ballarin@13940
  1007
    with nz show "finsum R ?s {.. deg R p + deg R q} ~= \<zero>"
ballarin@13940
  1008
      by (simp add: integral_iff lcoeff_nonzero R)
ballarin@13940
  1009
    qed (simp add: R)
ballarin@13940
  1010
  qed
ballarin@13940
  1011
ballarin@13940
  1012
lemma (in UP_cring) coeff_finsum:
ballarin@13940
  1013
  assumes fin: "finite A"
ballarin@13940
  1014
  shows "p \<in> A -> carrier P ==>
ballarin@13940
  1015
    coeff P (finsum P p A) k == finsum R (%i. coeff P (p i) k) A"
ballarin@13940
  1016
  using fin by induct (auto simp: Pi_def)
ballarin@13940
  1017
ballarin@13940
  1018
ML_setup {*
wenzelm@14590
  1019
  simpset_ref() := simpset() setsubgoaler asm_full_simp_tac;
wenzelm@14590
  1020
*}
ballarin@13940
  1021
ballarin@13940
  1022
lemma (in UP_cring) up_repr:
ballarin@13940
  1023
  assumes R: "p \<in> carrier P"
ballarin@13940
  1024
  shows "finsum P (%i. monom P (coeff P p i) i) {..deg R p} = p"
ballarin@13940
  1025
proof (rule up_eqI)
ballarin@13940
  1026
  let ?s = "(%i. monom P (coeff P p i) i)"
ballarin@13940
  1027
  fix k
ballarin@13940
  1028
  from R have RR: "!!i. (if i = k then coeff P p i else \<zero>) \<in> carrier R"
ballarin@13940
  1029
    by simp
ballarin@13940
  1030
  show "coeff P (finsum P ?s {..deg R p}) k = coeff P p k"
ballarin@13940
  1031
  proof (cases "k <= deg R p")
ballarin@13940
  1032
    case True
ballarin@13940
  1033
    hence "coeff P (finsum P ?s {..deg R p}) k = 
ballarin@13940
  1034
          coeff P (finsum P ?s ({..k} Un {)k..deg R p})) k"
ballarin@13940
  1035
      by (simp only: ivl_disj_un_one)
ballarin@13940
  1036
    also from True
ballarin@13940
  1037
    have "... = coeff P (finsum P ?s {..k}) k"
ballarin@13940
  1038
      by (simp cong: finsum_cong add: finsum_Un_disjoint
ballarin@13940
  1039
	ivl_disj_int_one order_less_imp_not_eq2 coeff_finsum R RR Pi_def)
ballarin@13940
  1040
    also
ballarin@13940
  1041
    have "... = coeff P (finsum P ?s ({..k(} Un {k})) k"
ballarin@13940
  1042
      by (simp only: ivl_disj_un_singleton)
ballarin@13940
  1043
    also have "... = coeff P p k"
ballarin@13940
  1044
      by (simp cong: finsum_cong add: setsum_Un_disjoint
ballarin@13940
  1045
	ivl_disj_int_singleton coeff_finsum deg_aboveD R RR Pi_def)
ballarin@13940
  1046
    finally show ?thesis .
ballarin@13940
  1047
  next
ballarin@13940
  1048
    case False
ballarin@13940
  1049
    hence "coeff P (finsum P ?s {..deg R p}) k = 
ballarin@13940
  1050
          coeff P (finsum P ?s ({..deg R p(} Un {deg R p})) k"
ballarin@13940
  1051
      by (simp only: ivl_disj_un_singleton)
ballarin@13940
  1052
    also from False have "... = coeff P p k"
ballarin@13940
  1053
      by (simp cong: finsum_cong add: setsum_Un_disjoint ivl_disj_int_singleton
ballarin@13940
  1054
        coeff_finsum deg_aboveD R Pi_def)
ballarin@13940
  1055
    finally show ?thesis .
ballarin@13940
  1056
  qed
ballarin@13940
  1057
qed (simp_all add: R Pi_def)
ballarin@13940
  1058
ballarin@13940
  1059
lemma (in UP_cring) up_repr_le:
ballarin@13940
  1060
  "[| deg R p <= n; p \<in> carrier P |] ==>
ballarin@13940
  1061
  finsum P (%i. monom P (coeff P p i) i) {..n} = p"
ballarin@13940
  1062
proof -
ballarin@13940
  1063
  let ?s = "(%i. monom P (coeff P p i) i)"
ballarin@13940
  1064
  assume R: "p \<in> carrier P" and "deg R p <= n"
ballarin@13940
  1065
  then have "finsum P ?s {..n} = finsum P ?s ({..deg R p} Un {)deg R p..n})"
ballarin@13940
  1066
    by (simp only: ivl_disj_un_one)
ballarin@13940
  1067
  also have "... = finsum P ?s {..deg R p}"
ballarin@13940
  1068
    by (simp cong: UP_finsum_cong add: UP_finsum_Un_disjoint ivl_disj_int_one
ballarin@13940
  1069
      deg_aboveD R Pi_def)
ballarin@13940
  1070
  also have "... = p" by (rule up_repr)
ballarin@13940
  1071
  finally show ?thesis .
ballarin@13940
  1072
qed
ballarin@13940
  1073
ballarin@13940
  1074
ML_setup {*
wenzelm@14590
  1075
  simpset_ref() := simpset() setsubgoaler asm_simp_tac;
wenzelm@14590
  1076
*}
ballarin@13940
  1077
ballarin@13949
  1078
subsection {* Polynomials over an integral domain form an integral domain *}
ballarin@13940
  1079
ballarin@13940
  1080
lemma domainI:
ballarin@13940
  1081
  assumes cring: "cring R"
ballarin@13940
  1082
    and one_not_zero: "one R ~= zero R"
ballarin@13940
  1083
    and integral: "!!a b. [| mult R a b = zero R; a \<in> carrier R;
ballarin@13940
  1084
      b \<in> carrier R |] ==> a = zero R | b = zero R"
ballarin@13940
  1085
  shows "domain R"
ballarin@13940
  1086
  by (auto intro!: domain.intro domain_axioms.intro cring.axioms prems
ballarin@13940
  1087
    del: disjCI)
ballarin@13940
  1088
ballarin@13940
  1089
lemma (in UP_domain) UP_one_not_zero:
ballarin@13940
  1090
  "\<one>\<^sub>2 ~= \<zero>\<^sub>2"
ballarin@13940
  1091
proof
ballarin@13940
  1092
  assume "\<one>\<^sub>2 = \<zero>\<^sub>2"
ballarin@13940
  1093
  hence "coeff P \<one>\<^sub>2 0 = (coeff P \<zero>\<^sub>2 0)" by simp
ballarin@13940
  1094
  hence "\<one> = \<zero>" by simp
ballarin@13940
  1095
  with one_not_zero show "False" by contradiction
ballarin@13940
  1096
qed
ballarin@13940
  1097
ballarin@13940
  1098
lemma (in UP_domain) UP_integral:
ballarin@13940
  1099
  "[| p \<otimes>\<^sub>2 q = \<zero>\<^sub>2; p \<in> carrier P; q \<in> carrier P |] ==> p = \<zero>\<^sub>2 | q = \<zero>\<^sub>2"
ballarin@13940
  1100
proof -
ballarin@13940
  1101
  fix p q
ballarin@13940
  1102
  assume pq: "p \<otimes>\<^sub>2 q = \<zero>\<^sub>2" and R: "p \<in> carrier P" "q \<in> carrier P"
ballarin@13940
  1103
  show "p = \<zero>\<^sub>2 | q = \<zero>\<^sub>2"
ballarin@13940
  1104
  proof (rule classical)
ballarin@13940
  1105
    assume c: "~ (p = \<zero>\<^sub>2 | q = \<zero>\<^sub>2)"
ballarin@13940
  1106
    with R have "deg R p + deg R q = deg R (p \<otimes>\<^sub>2 q)" by simp
ballarin@13940
  1107
    also from pq have "... = 0" by simp
ballarin@13940
  1108
    finally have "deg R p + deg R q = 0" .
ballarin@13940
  1109
    then have f1: "deg R p = 0 & deg R q = 0" by simp
ballarin@13940
  1110
    from f1 R have "p = finsum P (%i. (monom P (coeff P p i) i)) {..0}"
ballarin@13940
  1111
      by (simp only: up_repr_le)
ballarin@13940
  1112
    also from R have "... = monom P (coeff P p 0) 0" by simp
ballarin@13940
  1113
    finally have p: "p = monom P (coeff P p 0) 0" .
ballarin@13940
  1114
    from f1 R have "q = finsum P (%i. (monom P (coeff P q i) i)) {..0}"
ballarin@13940
  1115
      by (simp only: up_repr_le)
ballarin@13940
  1116
    also from R have "... = monom P (coeff P q 0) 0" by simp
ballarin@13940
  1117
    finally have q: "q = monom P (coeff P q 0) 0" .
ballarin@13940
  1118
    from R have "coeff P p 0 \<otimes> coeff P q 0 = coeff P (p \<otimes>\<^sub>2 q) 0" by simp
ballarin@13940
  1119
    also from pq have "... = \<zero>" by simp
ballarin@13940
  1120
    finally have "coeff P p 0 \<otimes> coeff P q 0 = \<zero>" .
ballarin@13940
  1121
    with R have "coeff P p 0 = \<zero> | coeff P q 0 = \<zero>"
ballarin@13940
  1122
      by (simp add: R.integral_iff)
ballarin@13940
  1123
    with p q show "p = \<zero>\<^sub>2 | q = \<zero>\<^sub>2" by fastsimp
ballarin@13940
  1124
  qed
ballarin@13940
  1125
qed
ballarin@13940
  1126
ballarin@13940
  1127
theorem (in UP_domain) UP_domain:
ballarin@13940
  1128
  "domain P"
ballarin@13940
  1129
  by (auto intro!: domainI UP_cring UP_one_not_zero UP_integral del: disjCI)
ballarin@13940
  1130
ballarin@13940
  1131
text {*
ballarin@13940
  1132
  Instantiation of results from @{term domain}.
ballarin@13940
  1133
*}
ballarin@13940
  1134
ballarin@13940
  1135
lemmas (in UP_domain) UP_zero_not_one [simp] =
ballarin@13940
  1136
  domain.zero_not_one [OF UP_domain]
ballarin@13940
  1137
ballarin@13940
  1138
lemmas (in UP_domain) UP_integral_iff =
ballarin@13940
  1139
  domain.integral_iff [OF UP_domain]
ballarin@13940
  1140
ballarin@13940
  1141
lemmas (in UP_domain) UP_m_lcancel =
ballarin@13940
  1142
  domain.m_lcancel [OF UP_domain]
ballarin@13940
  1143
ballarin@13940
  1144
lemmas (in UP_domain) UP_m_rcancel =
ballarin@13940
  1145
  domain.m_rcancel [OF UP_domain]
ballarin@13940
  1146
ballarin@13940
  1147
lemma (in UP_domain) smult_integral:
ballarin@13940
  1148
  "[| a \<odot>\<^sub>2 p = \<zero>\<^sub>2; a \<in> carrier R; p \<in> carrier P |] ==> a = \<zero> | p = \<zero>\<^sub>2"
ballarin@13940
  1149
  by (simp add: monom_mult_is_smult [THEN sym] UP_integral_iff
ballarin@13940
  1150
    inj_on_iff [OF monom_inj, of _ "\<zero>", simplified])
ballarin@13940
  1151
ballarin@13949
  1152
subsection {* Evaluation Homomorphism and Universal Property*}
ballarin@13940
  1153
ballarin@13940
  1154
ML_setup {*
wenzelm@14590
  1155
  simpset_ref() := simpset() setsubgoaler asm_full_simp_tac;
wenzelm@14590
  1156
*}
ballarin@13940
  1157
ballarin@13949
  1158
(* alternative congruence rule (possibly more efficient)
ballarin@13940
  1159
lemma (in abelian_monoid) finsum_cong2:
ballarin@13940
  1160
  "[| !!i. i \<in> A ==> f i \<in> carrier G = True; A = B;
ballarin@13940
  1161
  !!i. i \<in> B ==> f i = g i |] ==> finsum G f A = finsum G g B"
ballarin@13940
  1162
  sorry
ballarin@13940
  1163
*)
ballarin@13940
  1164
ballarin@13940
  1165
theorem (in cring) diagonal_sum:
ballarin@13940
  1166
  "[| f \<in> {..n + m::nat} -> carrier R; g \<in> {..n + m} -> carrier R |] ==>
ballarin@13940
  1167
  finsum R (%k. finsum R (%i. f i \<otimes> g (k - i)) {..k}) {..n + m} =
ballarin@13940
  1168
  finsum R (%k. finsum R (%i. f k \<otimes> g i) {..n + m - k}) {..n + m}"
ballarin@13940
  1169
proof -
ballarin@13940
  1170
  assume Rf: "f \<in> {..n + m} -> carrier R" and Rg: "g \<in> {..n + m} -> carrier R"
ballarin@13940
  1171
  {
ballarin@13940
  1172
    fix j
ballarin@13940
  1173
    have "j <= n + m ==>
ballarin@13940
  1174
      finsum R (%k. finsum R (%i. f i \<otimes> g (k - i)) {..k}) {..j} =
ballarin@13940
  1175
      finsum R (%k. finsum R (%i. f k \<otimes> g i) {..j - k}) {..j}"
ballarin@13940
  1176
    proof (induct j)
ballarin@13940
  1177
      case 0 from Rf Rg show ?case by (simp add: Pi_def)
ballarin@13940
  1178
    next
ballarin@13940
  1179
      case (Suc j) 
ballarin@13940
  1180
      (* The following could be simplified if there was a reasoner for
ballarin@13940
  1181
	total orders integrated with simip. *)
ballarin@13940
  1182
      have R6: "!!i k. [| k <= j; i <= Suc j - k |] ==> g i \<in> carrier R"
ballarin@13940
  1183
	using Suc by (auto intro!: funcset_mem [OF Rg]) arith
ballarin@13940
  1184
      have R8: "!!i k. [| k <= Suc j; i <= k |] ==> g (k - i) \<in> carrier R"
ballarin@13940
  1185
	using Suc by (auto intro!: funcset_mem [OF Rg]) arith
ballarin@13940
  1186
      have R9: "!!i k. [| k <= Suc j |] ==> f k \<in> carrier R"
ballarin@13940
  1187
	using Suc by (auto intro!: funcset_mem [OF Rf])
ballarin@13940
  1188
      have R10: "!!i k. [| k <= Suc j; i <= Suc j - k |] ==> g i \<in> carrier R"
ballarin@13940
  1189
	using Suc by (auto intro!: funcset_mem [OF Rg]) arith
ballarin@13940
  1190
      have R11: "g 0 \<in> carrier R"
ballarin@13940
  1191
	using Suc by (auto intro!: funcset_mem [OF Rg])
ballarin@13940
  1192
      from Suc show ?case
ballarin@13940
  1193
	by (simp cong: finsum_cong add: Suc_diff_le a_ac
ballarin@13940
  1194
	  Pi_def R6 R8 R9 R10 R11)
ballarin@13940
  1195
    qed
ballarin@13940
  1196
  }
ballarin@13940
  1197
  then show ?thesis by fast
ballarin@13940
  1198
qed
ballarin@13940
  1199
ballarin@13940
  1200
lemma (in abelian_monoid) boundD_carrier:
ballarin@13940
  1201
  "[| bound \<zero> n f; n < m |] ==> f m \<in> carrier G"
ballarin@13940
  1202
  by auto
ballarin@13940
  1203
ballarin@13940
  1204
theorem (in cring) cauchy_product:
ballarin@13940
  1205
  assumes bf: "bound \<zero> n f" and bg: "bound \<zero> m g"
ballarin@13940
  1206
    and Rf: "f \<in> {..n} -> carrier R" and Rg: "g \<in> {..m} -> carrier R"
ballarin@13940
  1207
  shows "finsum R (%k. finsum R (%i. f i \<otimes> g (k-i)) {..k}) {..n + m} =
ballarin@13940
  1208
    finsum R f {..n} \<otimes> finsum R g {..m}"
ballarin@13940
  1209
(* State revese direction? *)
ballarin@13940
  1210
proof -
ballarin@13940
  1211
  have f: "!!x. f x \<in> carrier R"
ballarin@13940
  1212
  proof -
ballarin@13940
  1213
    fix x
ballarin@13940
  1214
    show "f x \<in> carrier R"
ballarin@13940
  1215
      using Rf bf boundD_carrier by (cases "x <= n") (auto simp: Pi_def)
ballarin@13940
  1216
  qed
ballarin@13940
  1217
  have g: "!!x. g x \<in> carrier R"
ballarin@13940
  1218
  proof -
ballarin@13940
  1219
    fix x
ballarin@13940
  1220
    show "g x \<in> carrier R"
ballarin@13940
  1221
      using Rg bg boundD_carrier by (cases "x <= m") (auto simp: Pi_def)
ballarin@13940
  1222
  qed
ballarin@13940
  1223
  from f g have "finsum R (%k. finsum R (%i. f i \<otimes> g (k-i)) {..k}) {..n + m} =
ballarin@13940
  1224
    finsum R (%k. finsum R (%i. f k \<otimes> g i) {..n + m - k}) {..n + m}"
ballarin@13940
  1225
    by (simp add: diagonal_sum Pi_def)
ballarin@13940
  1226
  also have "... = finsum R
ballarin@13940
  1227
      (%k. finsum R (%i. f k \<otimes> g i) {..n + m - k}) ({..n} Un {)n..n + m})"
ballarin@13940
  1228
    by (simp only: ivl_disj_un_one)
ballarin@13940
  1229
  also from f g have "... = finsum R
ballarin@13940
  1230
      (%k. finsum R (%i. f k \<otimes> g i) {..n + m - k}) {..n}"
ballarin@13940
  1231
    by (simp cong: finsum_cong
ballarin@13940
  1232
      add: boundD [OF bf] finsum_Un_disjoint ivl_disj_int_one Pi_def)
ballarin@13940
  1233
  also from f g have "... = finsum R
ballarin@13940
  1234
      (%k. finsum R (%i. f k \<otimes> g i) ({..m} Un {)m..n + m - k})) {..n}"
ballarin@13940
  1235
    by (simp cong: finsum_cong add: ivl_disj_un_one le_add_diff Pi_def)
ballarin@13940
  1236
  also from f g have "... = finsum R
ballarin@13940
  1237
      (%k. finsum R (%i. f k \<otimes> g i) {..m}) {..n}"
ballarin@13940
  1238
    by (simp cong: finsum_cong
ballarin@13940
  1239
      add: boundD [OF bg] finsum_Un_disjoint ivl_disj_int_one Pi_def)
ballarin@13940
  1240
  also from f g have "... = finsum R f {..n} \<otimes> finsum R g {..m}"
ballarin@13940
  1241
    by (simp add: finsum_ldistr diagonal_sum Pi_def,
ballarin@13940
  1242
      simp cong: finsum_cong add: finsum_rdistr Pi_def)
ballarin@13940
  1243
  finally show ?thesis .
ballarin@13940
  1244
qed
ballarin@13940
  1245
ballarin@13940
  1246
lemma (in UP_cring) const_ring_hom:
ballarin@13940
  1247
  "(%a. monom P a 0) \<in> ring_hom R P"
ballarin@13940
  1248
  by (auto intro!: ring_hom_memI intro: up_eqI simp: monom_mult_is_smult)
ballarin@13940
  1249
wenzelm@14651
  1250
constdefs (structure S)
wenzelm@14651
  1251
  eval :: "[_, _, 'a => 'b, 'b, nat => 'a] => 'b"
wenzelm@14651
  1252
  "eval R S phi s == \<lambda>p \<in> carrier (UP R).
wenzelm@14651
  1253
    \<Oplus>i \<in> {..deg R p}. phi (coeff (UP R) p i) \<otimes> pow S s i"
ballarin@13940
  1254
(*
ballarin@13940
  1255
  "eval R S phi s p == if p \<in> carrier (UP R)
ballarin@13940
  1256
  then finsum S (%i. mult S (phi (coeff (UP R) p i)) (pow S s i)) {..deg R p}
ballarin@13940
  1257
  else arbitrary"
ballarin@13940
  1258
*)
ballarin@13940
  1259
                                                         
ballarin@13940
  1260
locale ring_hom_UP_cring = ring_hom_cring R S + UP_cring R
ballarin@13940
  1261
ballarin@13940
  1262
lemma (in ring_hom_UP_cring) eval_on_carrier:
ballarin@13940
  1263
  "p \<in> carrier P ==>
ballarin@13940
  1264
    eval R S phi s p =
ballarin@13940
  1265
    finsum S (%i. mult S (phi (coeff P p i)) (pow S s i)) {..deg R p}"
ballarin@13940
  1266
  by (unfold eval_def, fold P_def) simp
ballarin@13940
  1267
ballarin@13940
  1268
lemma (in ring_hom_UP_cring) eval_extensional:
ballarin@13940
  1269
  "eval R S phi s \<in> extensional (carrier P)"
ballarin@13940
  1270
  by (unfold eval_def, fold P_def) simp
ballarin@13940
  1271
ballarin@13940
  1272
theorem (in ring_hom_UP_cring) eval_ring_hom:
ballarin@13940
  1273
  "s \<in> carrier S ==> eval R S h s \<in> ring_hom P S"
ballarin@13940
  1274
proof (rule ring_hom_memI)
ballarin@13940
  1275
  fix p
ballarin@13940
  1276
  assume RS: "p \<in> carrier P" "s \<in> carrier S"
ballarin@13940
  1277
  then show "eval R S h s p \<in> carrier S"
ballarin@13940
  1278
    by (simp only: eval_on_carrier) (simp add: Pi_def)
ballarin@13940
  1279
next
ballarin@13940
  1280
  fix p q
ballarin@13940
  1281
  assume RS: "p \<in> carrier P" "q \<in> carrier P" "s \<in> carrier S"
ballarin@13940
  1282
  then show "eval R S h s (p \<otimes>\<^sub>3 q) = eval R S h s p \<otimes>\<^sub>2 eval R S h s q"
ballarin@13940
  1283
  proof (simp only: eval_on_carrier UP_mult_closed)
ballarin@13940
  1284
    from RS have
ballarin@13940
  1285
      "finsum S (%i. h (coeff P (p \<otimes>\<^sub>3 q) i) \<otimes>\<^sub>2 s (^)\<^sub>2 i) {..deg R (p \<otimes>\<^sub>3 q)} =
ballarin@13940
  1286
      finsum S (%i. h (coeff P (p \<otimes>\<^sub>3 q) i) \<otimes>\<^sub>2 s (^)\<^sub>2 i)
ballarin@13940
  1287
        ({..deg R (p \<otimes>\<^sub>3 q)} Un {)deg R (p \<otimes>\<^sub>3 q)..deg R p + deg R q})"
ballarin@13940
  1288
      by (simp cong: finsum_cong
ballarin@13940
  1289
	add: deg_aboveD finsum_Un_disjoint ivl_disj_int_one Pi_def
ballarin@13940
  1290
	del: coeff_mult)
ballarin@13940
  1291
    also from RS have "... =
ballarin@13940
  1292
      finsum S (%i. h (coeff P (p \<otimes>\<^sub>3 q) i) \<otimes>\<^sub>2 s (^)\<^sub>2 i) {..deg R p + deg R q}"
ballarin@13940
  1293
      by (simp only: ivl_disj_un_one deg_mult_cring)
ballarin@13940
  1294
    also from RS have "... =
ballarin@13940
  1295
      finsum S (%i.
ballarin@13940
  1296
        finsum S (%k. 
ballarin@13940
  1297
        (h (coeff P p k) \<otimes>\<^sub>2 h (coeff P q (i-k))) \<otimes>\<^sub>2 (s (^)\<^sub>2 k \<otimes>\<^sub>2 s (^)\<^sub>2 (i-k)))
ballarin@13940
  1298
      {..i}) {..deg R p + deg R q}"
ballarin@13940
  1299
      by (simp cong: finsum_cong add: nat_pow_mult Pi_def
ballarin@13940
  1300
	S.m_ac S.finsum_rdistr)
ballarin@13940
  1301
    also from RS have "... =
ballarin@13940
  1302
      finsum S (%i. h (coeff P p i) \<otimes>\<^sub>2 s (^)\<^sub>2 i) {..deg R p} \<otimes>\<^sub>2
ballarin@13940
  1303
      finsum S (%i. h (coeff P q i) \<otimes>\<^sub>2 s (^)\<^sub>2 i) {..deg R q}"
ballarin@13940
  1304
      by (simp add: S.cauchy_product [THEN sym] boundI deg_aboveD S.m_ac
ballarin@13940
  1305
	Pi_def)
ballarin@13940
  1306
    finally show
ballarin@13940
  1307
      "finsum S (%i. h (coeff P (p \<otimes>\<^sub>3 q) i) \<otimes>\<^sub>2 s (^)\<^sub>2 i) {..deg R (p \<otimes>\<^sub>3 q)} =
ballarin@13940
  1308
      finsum S (%i. h (coeff P p i) \<otimes>\<^sub>2 s (^)\<^sub>2 i) {..deg R p} \<otimes>\<^sub>2
ballarin@13940
  1309
      finsum S (%i. h (coeff P q i) \<otimes>\<^sub>2 s (^)\<^sub>2 i) {..deg R q}" .
ballarin@13940
  1310
  qed
ballarin@13940
  1311
next
ballarin@13940
  1312
  fix p q
ballarin@13940
  1313
  assume RS: "p \<in> carrier P" "q \<in> carrier P" "s \<in> carrier S"
ballarin@13940
  1314
  then show "eval R S h s (p \<oplus>\<^sub>3 q) = eval R S h s p \<oplus>\<^sub>2 eval R S h s q"
ballarin@13940
  1315
  proof (simp only: eval_on_carrier UP_a_closed)
ballarin@13940
  1316
    from RS have
ballarin@13940
  1317
      "finsum S (%i. h (coeff P (p \<oplus>\<^sub>3 q) i) \<otimes>\<^sub>2 s (^)\<^sub>2 i) {..deg R (p \<oplus>\<^sub>3 q)} =
ballarin@13940
  1318
      finsum S (%i. h (coeff P (p \<oplus>\<^sub>3 q) i) \<otimes>\<^sub>2 s (^)\<^sub>2 i)
ballarin@13940
  1319
        ({..deg R (p \<oplus>\<^sub>3 q)} Un {)deg R (p \<oplus>\<^sub>3 q)..max (deg R p) (deg R q)})"
ballarin@13940
  1320
      by (simp cong: finsum_cong
ballarin@13940
  1321
	add: deg_aboveD finsum_Un_disjoint ivl_disj_int_one Pi_def
ballarin@13940
  1322
	del: coeff_add)
ballarin@13940
  1323
    also from RS have "... =
ballarin@13940
  1324
      finsum S (%i. h (coeff P (p \<oplus>\<^sub>3 q) i) \<otimes>\<^sub>2 s (^)\<^sub>2 i)
ballarin@13940
  1325
        {..max (deg R p) (deg R q)}"
ballarin@13940
  1326
      by (simp add: ivl_disj_un_one)
ballarin@13940
  1327
    also from RS have "... =
ballarin@13940
  1328
      finsum S (%i. h (coeff P p i) \<otimes>\<^sub>2 s (^)\<^sub>2 i) {..max (deg R p) (deg R q)} \<oplus>\<^sub>2
ballarin@13940
  1329
      finsum S (%i. h (coeff P q i) \<otimes>\<^sub>2 s (^)\<^sub>2 i) {..max (deg R p) (deg R q)}"
ballarin@13940
  1330
      by (simp cong: finsum_cong
ballarin@13940
  1331
	add: l_distr deg_aboveD finsum_Un_disjoint ivl_disj_int_one Pi_def)
ballarin@13940
  1332
    also have "... =
ballarin@13940
  1333
      finsum S (%i. h (coeff P p i) \<otimes>\<^sub>2 s (^)\<^sub>2 i)
ballarin@13940
  1334
        ({..deg R p} Un {)deg R p..max (deg R p) (deg R q)}) \<oplus>\<^sub>2
ballarin@13940
  1335
      finsum S (%i. h (coeff P q i) \<otimes>\<^sub>2 s (^)\<^sub>2 i)
ballarin@13940
  1336
        ({..deg R q} Un {)deg R q..max (deg R p) (deg R q)})"
ballarin@13940
  1337
      by (simp only: ivl_disj_un_one le_maxI1 le_maxI2)
ballarin@13940
  1338
    also from RS have "... =
ballarin@13940
  1339
      finsum S (%i. h (coeff P p i) \<otimes>\<^sub>2 s (^)\<^sub>2 i) {..deg R p} \<oplus>\<^sub>2
ballarin@13940
  1340
      finsum S (%i. h (coeff P q i) \<otimes>\<^sub>2 s (^)\<^sub>2 i) {..deg R q}"
ballarin@13940
  1341
      by (simp cong: finsum_cong
ballarin@13940
  1342
	add: deg_aboveD finsum_Un_disjoint ivl_disj_int_one Pi_def)
ballarin@13940
  1343
    finally show
ballarin@13940
  1344
      "finsum S (%i. h (coeff P (p \<oplus>\<^sub>3 q) i) \<otimes>\<^sub>2 s (^)\<^sub>2 i) {..deg R (p \<oplus>\<^sub>3 q)} =
ballarin@13940
  1345
      finsum S (%i. h (coeff P p i) \<otimes>\<^sub>2 s (^)\<^sub>2 i) {..deg R p} \<oplus>\<^sub>2
ballarin@13940
  1346
      finsum S (%i. h (coeff P q i) \<otimes>\<^sub>2 s (^)\<^sub>2 i) {..deg R q}"
ballarin@13940
  1347
      .
ballarin@13940
  1348
  qed
ballarin@13940
  1349
next
ballarin@13940
  1350
  assume S: "s \<in> carrier S"
ballarin@13940
  1351
  then show "eval R S h s \<one>\<^sub>3 = \<one>\<^sub>2"
ballarin@13940
  1352
    by (simp only: eval_on_carrier UP_one_closed) simp
ballarin@13940
  1353
qed
ballarin@13940
  1354
ballarin@13940
  1355
text {* Instantiation of ring homomorphism lemmas. *}
ballarin@13940
  1356
ballarin@13940
  1357
lemma (in ring_hom_UP_cring) ring_hom_cring_P_S:
ballarin@13940
  1358
  "s \<in> carrier S ==> ring_hom_cring P S (eval R S h s)"
ballarin@13940
  1359
  by (fast intro!: ring_hom_cring.intro UP_cring cring.axioms prems
ballarin@13940
  1360
  intro: ring_hom_cring_axioms.intro eval_ring_hom)
ballarin@13940
  1361
ballarin@13940
  1362
lemma (in ring_hom_UP_cring) UP_hom_closed [intro, simp]:
ballarin@13940
  1363
  "[| s \<in> carrier S; p \<in> carrier P |] ==> eval R S h s p \<in> carrier S"
ballarin@13940
  1364
  by (rule ring_hom_cring.hom_closed [OF ring_hom_cring_P_S])
ballarin@13940
  1365
ballarin@13940
  1366
lemma (in ring_hom_UP_cring) UP_hom_mult [simp]:
ballarin@13940
  1367
  "[| s \<in> carrier S; p \<in> carrier P; q \<in> carrier P |] ==>
ballarin@13940
  1368
  eval R S h s (p \<otimes>\<^sub>3 q) = eval R S h s p \<otimes>\<^sub>2 eval R S h s q"
ballarin@13940
  1369
  by (rule ring_hom_cring.hom_mult [OF ring_hom_cring_P_S])
ballarin@13940
  1370
ballarin@13940
  1371
lemma (in ring_hom_UP_cring) UP_hom_add [simp]:
ballarin@13940
  1372
  "[| s \<in> carrier S; p \<in> carrier P; q \<in> carrier P |] ==>
ballarin@13940
  1373
  eval R S h s (p \<oplus>\<^sub>3 q) = eval R S h s p \<oplus>\<^sub>2 eval R S h s q"
ballarin@13940
  1374
  by (rule ring_hom_cring.hom_add [OF ring_hom_cring_P_S])
ballarin@13940
  1375
ballarin@13940
  1376
lemma (in ring_hom_UP_cring) UP_hom_one [simp]:
ballarin@13940
  1377
  "s \<in> carrier S ==> eval R S h s \<one>\<^sub>3 = \<one>\<^sub>2"
ballarin@13940
  1378
  by (rule ring_hom_cring.hom_one [OF ring_hom_cring_P_S])
ballarin@13940
  1379
ballarin@13940
  1380
lemma (in ring_hom_UP_cring) UP_hom_zero [simp]:
ballarin@13940
  1381
  "s \<in> carrier S ==> eval R S h s \<zero>\<^sub>3 = \<zero>\<^sub>2"
ballarin@13940
  1382
  by (rule ring_hom_cring.hom_zero [OF ring_hom_cring_P_S])
ballarin@13940
  1383
ballarin@13940
  1384
lemma (in ring_hom_UP_cring) UP_hom_a_inv [simp]:
ballarin@13940
  1385
  "[| s \<in> carrier S; p \<in> carrier P |] ==>
ballarin@13940
  1386
  (eval R S h s) (\<ominus>\<^sub>3 p) = \<ominus>\<^sub>2 (eval R S h s) p"
ballarin@13940
  1387
  by (rule ring_hom_cring.hom_a_inv [OF ring_hom_cring_P_S])
ballarin@13940
  1388
ballarin@13940
  1389
lemma (in ring_hom_UP_cring) UP_hom_finsum [simp]:
ballarin@13940
  1390
  "[| s \<in> carrier S; finite A; f \<in> A -> carrier P |] ==>
ballarin@13940
  1391
  (eval R S h s) (finsum P f A) = finsum S (eval R S h s o f) A"
ballarin@13940
  1392
  by (rule ring_hom_cring.hom_finsum [OF ring_hom_cring_P_S])
ballarin@13940
  1393
ballarin@13940
  1394
lemma (in ring_hom_UP_cring) UP_hom_finprod [simp]:
ballarin@13940
  1395
  "[| s \<in> carrier S; finite A; f \<in> A -> carrier P |] ==>
ballarin@13940
  1396
  (eval R S h s) (finprod P f A) = finprod S (eval R S h s o f) A"
ballarin@13940
  1397
  by (rule ring_hom_cring.hom_finprod [OF ring_hom_cring_P_S])
ballarin@13940
  1398
ballarin@13940
  1399
text {* Further properties of the evaluation homomorphism. *}
ballarin@13940
  1400
ballarin@13940
  1401
(* The following lemma could be proved in UP\_cring with the additional
ballarin@13940
  1402
   assumption that h is closed. *)
ballarin@13940
  1403
ballarin@13940
  1404
lemma (in ring_hom_UP_cring) eval_const:
ballarin@13940
  1405
  "[| s \<in> carrier S; r \<in> carrier R |] ==> eval R S h s (monom P r 0) = h r"
ballarin@13940
  1406
  by (simp only: eval_on_carrier monom_closed) simp
ballarin@13940
  1407
ballarin@13940
  1408
text {* The following proof is complicated by the fact that in arbitrary
ballarin@13940
  1409
  rings one might have @{term "one R = zero R"}. *}
ballarin@13940
  1410
ballarin@13940
  1411
(* TODO: simplify by cases "one R = zero R" *)
ballarin@13940
  1412
ballarin@13940
  1413
lemma (in ring_hom_UP_cring) eval_monom1:
ballarin@13940
  1414
  "s \<in> carrier S ==> eval R S h s (monom P \<one> 1) = s"
ballarin@13940
  1415
proof (simp only: eval_on_carrier monom_closed R.one_closed)
ballarin@13940
  1416
  assume S: "s \<in> carrier S"
ballarin@13940
  1417
  then have "finsum S (\<lambda>i. h (coeff P (monom P \<one> 1) i) \<otimes>\<^sub>2 s (^)\<^sub>2 i)
ballarin@13940
  1418
      {..deg R (monom P \<one> 1)} =
ballarin@13940
  1419
    finsum S (\<lambda>i. h (coeff P (monom P \<one> 1) i) \<otimes>\<^sub>2 s (^)\<^sub>2 i)
ballarin@13940
  1420
      ({..deg R (monom P \<one> 1)} Un {)deg R (monom P \<one> 1)..1})"
ballarin@13940
  1421
    by (simp cong: finsum_cong del: coeff_monom
ballarin@13940
  1422
      add: deg_aboveD finsum_Un_disjoint ivl_disj_int_one Pi_def)
ballarin@13940
  1423
  also have "... = 
ballarin@13940
  1424
    finsum S (\<lambda>i. h (coeff P (monom P \<one> 1) i) \<otimes>\<^sub>2 s (^)\<^sub>2 i) {..1}"
ballarin@13940
  1425
    by (simp only: ivl_disj_un_one deg_monom_le R.one_closed)
ballarin@13940
  1426
  also have "... = s"
ballarin@13940
  1427
  proof (cases "s = \<zero>\<^sub>2")
ballarin@13940
  1428
    case True then show ?thesis by (simp add: Pi_def)
ballarin@13940
  1429
  next
ballarin@13940
  1430
    case False with S show ?thesis by (simp add: Pi_def)
ballarin@13940
  1431
  qed
ballarin@13940
  1432
  finally show "finsum S (\<lambda>i. h (coeff P (monom P \<one> 1) i) \<otimes>\<^sub>2 s (^)\<^sub>2 i)
ballarin@13940
  1433
      {..deg R (monom P \<one> 1)} = s" .
ballarin@13940
  1434
qed
ballarin@13940
  1435
ballarin@13940
  1436
lemma (in UP_cring) monom_pow:
ballarin@13940
  1437
  assumes R: "a \<in> carrier R"
ballarin@13940
  1438
  shows "(monom P a n) (^)\<^sub>2 m = monom P (a (^) m) (n * m)"
ballarin@13940
  1439
proof (induct m)
ballarin@13940
  1440
  case 0 from R show ?case by simp
ballarin@13940
  1441
next
ballarin@13940
  1442
  case Suc with R show ?case
ballarin@13940
  1443
    by (simp del: monom_mult add: monom_mult [THEN sym] add_commute)
ballarin@13940
  1444
qed
ballarin@13940
  1445
ballarin@13940
  1446
lemma (in ring_hom_cring) hom_pow [simp]:
ballarin@13940
  1447
  "x \<in> carrier R ==> h (x (^) n) = h x (^)\<^sub>2 (n::nat)"
ballarin@13940
  1448
  by (induct n) simp_all
ballarin@13940
  1449
ballarin@13940
  1450
lemma (in ring_hom_UP_cring) UP_hom_pow [simp]:
ballarin@13940
  1451
  "[| s \<in> carrier S; p \<in> carrier P |] ==>
ballarin@13940
  1452
  (eval R S h s) (p (^)\<^sub>3 n) = eval R S h s p (^)\<^sub>2 (n::nat)"
ballarin@13940
  1453
  by (rule ring_hom_cring.hom_pow [OF ring_hom_cring_P_S])
ballarin@13940
  1454
ballarin@13940
  1455
lemma (in ring_hom_UP_cring) eval_monom:
ballarin@13940
  1456
  "[| s \<in> carrier S; r \<in> carrier R |] ==>
ballarin@13940
  1457
  eval R S h s (monom P r n) = h r \<otimes>\<^sub>2 s (^)\<^sub>2 n"
ballarin@13940
  1458
proof -
ballarin@13940
  1459
  assume RS: "s \<in> carrier S" "r \<in> carrier R"
ballarin@13940
  1460
  then have "eval R S h s (monom P r n) =
ballarin@13940
  1461
    eval R S h s (monom P r 0 \<otimes>\<^sub>3 (monom P \<one> 1) (^)\<^sub>3 n)"
ballarin@13940
  1462
    by (simp del: monom_mult UP_hom_mult UP_hom_pow
ballarin@13940
  1463
      add: monom_mult [THEN sym] monom_pow)
ballarin@13940
  1464
  also from RS eval_monom1 have "... = h r \<otimes>\<^sub>2 s (^)\<^sub>2 n"
ballarin@13940
  1465
    by (simp add: eval_const)
ballarin@13940
  1466
  finally show ?thesis .
ballarin@13940
  1467
qed
ballarin@13940
  1468
ballarin@13940
  1469
lemma (in ring_hom_UP_cring) eval_smult:
ballarin@13940
  1470
  "[| s \<in> carrier S; r \<in> carrier R; p \<in> carrier P |] ==>
ballarin@13940
  1471
  eval R S h s (r \<odot>\<^sub>3 p) = h r \<otimes>\<^sub>2 eval R S h s p"
ballarin@13940
  1472
  by (simp add: monom_mult_is_smult [THEN sym] eval_const)
ballarin@13940
  1473
ballarin@13940
  1474
lemma ring_hom_cringI:
ballarin@13940
  1475
  assumes "cring R"
ballarin@13940
  1476
    and "cring S"
ballarin@13940
  1477
    and "h \<in> ring_hom R S"
ballarin@13940
  1478
  shows "ring_hom_cring R S h"
ballarin@13940
  1479
  by (fast intro: ring_hom_cring.intro ring_hom_cring_axioms.intro
ballarin@13940
  1480
    cring.axioms prems)
ballarin@13940
  1481
ballarin@13940
  1482
lemma (in ring_hom_UP_cring) UP_hom_unique:
ballarin@13940
  1483
  assumes Phi: "Phi \<in> ring_hom P S" "Phi (monom P \<one> (Suc 0)) = s"
ballarin@13940
  1484
      "!!r. r \<in> carrier R ==> Phi (monom P r 0) = h r"
ballarin@13940
  1485
    and Psi: "Psi \<in> ring_hom P S" "Psi (monom P \<one> (Suc 0)) = s"
ballarin@13940
  1486
      "!!r. r \<in> carrier R ==> Psi (monom P r 0) = h r"
ballarin@13940
  1487
    and RS: "s \<in> carrier S" "p \<in> carrier P"
ballarin@13940
  1488
  shows "Phi p = Psi p"
ballarin@13940
  1489
proof -
ballarin@13940
  1490
  have Phi_hom: "ring_hom_cring P S Phi"
ballarin@13940
  1491
    by (auto intro: ring_hom_cringI UP_cring S.cring Phi)
ballarin@13940
  1492
  have Psi_hom: "ring_hom_cring P S Psi"
ballarin@13940
  1493
    by (auto intro: ring_hom_cringI UP_cring S.cring Psi)
ballarin@13940
  1494
  have "Phi p = Phi (finsum P
ballarin@13940
  1495
    (%i. monom P (coeff P p i) 0 \<otimes>\<^sub>3 (monom P \<one> 1) (^)\<^sub>3 i) {..deg R p})"
ballarin@13940
  1496
    by (simp add: up_repr RS monom_mult [THEN sym] monom_pow del: monom_mult)
ballarin@13940
  1497
  also have "... = Psi (finsum P
ballarin@13940
  1498
    (%i. monom P (coeff P p i) 0 \<otimes>\<^sub>3 (monom P \<one> 1) (^)\<^sub>3 i) {..deg R p})"
ballarin@13940
  1499
    by (simp add: ring_hom_cring.hom_finsum [OF Phi_hom] 
ballarin@13940
  1500
      ring_hom_cring.hom_mult [OF Phi_hom]
ballarin@13940
  1501
      ring_hom_cring.hom_pow [OF Phi_hom] Phi
ballarin@13940
  1502
      ring_hom_cring.hom_finsum [OF Psi_hom] 
ballarin@13940
  1503
      ring_hom_cring.hom_mult [OF Psi_hom]
ballarin@13940
  1504
      ring_hom_cring.hom_pow [OF Psi_hom] Psi RS Pi_def comp_def)
ballarin@13940
  1505
  also have "... = Psi p"
ballarin@13940
  1506
    by (simp add: up_repr RS monom_mult [THEN sym] monom_pow del: monom_mult)
ballarin@13940
  1507
  finally show ?thesis .
ballarin@13940
  1508
qed
ballarin@13940
  1509
ballarin@13940
  1510
ballarin@13940
  1511
theorem (in ring_hom_UP_cring) UP_universal_property:
ballarin@13940
  1512
  "s \<in> carrier S ==>
ballarin@13940
  1513
  EX! Phi. Phi \<in> ring_hom P S \<inter> extensional (carrier P) &
ballarin@13940
  1514
    Phi (monom P \<one> 1) = s & 
ballarin@13940
  1515
    (ALL r : carrier R. Phi (monom P r 0) = h r)"
ballarin@13940
  1516
  using eval_monom1                              
ballarin@13940
  1517
  apply (auto intro: eval_ring_hom eval_const eval_extensional)
ballarin@13940
  1518
  apply (rule extensionalityI)                                 
ballarin@13940
  1519
  apply (auto intro: UP_hom_unique)                            
ballarin@13940
  1520
  done                                                         
ballarin@13940
  1521
ballarin@13940
  1522
subsection {* Sample application of evaluation homomorphism *}
ballarin@13940
  1523
ballarin@13940
  1524
lemma ring_hom_UP_cringI:
ballarin@13940
  1525
  assumes "cring R"
ballarin@13940
  1526
    and "cring S"
ballarin@13940
  1527
    and "h \<in> ring_hom R S"
ballarin@13940
  1528
  shows "ring_hom_UP_cring R S h"
ballarin@13940
  1529
  by (fast intro: ring_hom_UP_cring.intro ring_hom_cring_axioms.intro
ballarin@13940
  1530
    cring.axioms prems)
ballarin@13940
  1531
ballarin@13975
  1532
constdefs
ballarin@13975
  1533
  INTEG :: "int ring"
ballarin@13975
  1534
  "INTEG == (| carrier = UNIV, mult = op *, one = 1, zero = 0, add = op + |)"
ballarin@13975
  1535
ballarin@13975
  1536
lemma cring_INTEG:
ballarin@13975
  1537
  "cring INTEG"
ballarin@13975
  1538
  by (unfold INTEG_def) (auto intro!: cringI abelian_groupI comm_monoidI
ballarin@13975
  1539
    zadd_zminus_inverse2 zadd_zmult_distrib)
ballarin@13975
  1540
ballarin@13940
  1541
lemma INTEG_id:
ballarin@13940
  1542
  "ring_hom_UP_cring INTEG INTEG id"
ballarin@13940
  1543
  by (fast intro: ring_hom_UP_cringI cring_INTEG id_ring_hom)
ballarin@13940
  1544
ballarin@13940
  1545
text {*
ballarin@13940
  1546
  An instantiation mechanism would now import all theorems and lemmas
ballarin@13940
  1547
  valid in the context of homomorphisms between @{term INTEG} and @{term
ballarin@13940
  1548
  "UP INTEG"}.  *}
ballarin@13940
  1549
ballarin@13940
  1550
lemma INTEG_closed [intro, simp]:
ballarin@13940
  1551
  "z \<in> carrier INTEG"
ballarin@13940
  1552
  by (unfold INTEG_def) simp
ballarin@13940
  1553
ballarin@13940
  1554
lemma INTEG_mult [simp]:
ballarin@13940
  1555
  "mult INTEG z w = z * w"
ballarin@13940
  1556
  by (unfold INTEG_def) simp
ballarin@13940
  1557
ballarin@13940
  1558
lemma INTEG_pow [simp]:
ballarin@13940
  1559
  "pow INTEG z n = z ^ n"
ballarin@13940
  1560
  by (induct n) (simp_all add: INTEG_def nat_pow_def)
ballarin@13940
  1561
ballarin@13940
  1562
lemma "eval INTEG INTEG id 10 (monom (UP INTEG) 5 2) = 500"
ballarin@13940
  1563
  by (simp add: ring_hom_UP_cring.eval_monom [OF INTEG_id])
ballarin@13940
  1564
ballarin@13940
  1565
-- {* Calculates @{term "x = 500"} *}
ballarin@13940
  1566
wenzelm@14590
  1567
end