diff -r c0eac04ae3b4 -r c34347ec7ab3 Nominal-General/Nominal2_Supp.thy
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Nominal-General/Nominal2_Supp.thy	Sun Apr 04 21:39:28 2010 +0200
@@ -0,0 +1,501 @@
+(*  Title:      Nominal2_Supp
+    Authors:    Brian Huffman, Christian Urban
+
+    Supplementary Lemmas and Definitions for 
+    Nominal Isabelle. 
+*)
+theory Nominal2_Supp
+imports Nominal2_Base Nominal2_Eqvt Nominal2_Atoms
+begin
+
+
+section {* Fresh-Star *}
+
+text {* The fresh-star generalisation of fresh is used in strong
+  induction principles. *}
+
+definition 
+  fresh_star :: "atom set \<Rightarrow> 'a::pt \<Rightarrow> bool" ("_ \<sharp>* _" [80,80] 80)
+where 
+  "as \<sharp>* x \<equiv> \<forall>a \<in> as. a \<sharp> x"
+
+lemma fresh_star_prod:
+  fixes as::"atom set"
+  shows "as \<sharp>* (x, y) = (as \<sharp>* x \<and> as \<sharp>* y)"
+  by (auto simp add: fresh_star_def fresh_Pair)
+
+lemma fresh_star_union:
+  shows "(as \<union> bs) \<sharp>* x = (as \<sharp>* x \<and> bs \<sharp>* x)"
+  by (auto simp add: fresh_star_def)
+
+lemma fresh_star_insert:
+  shows "(insert a as) \<sharp>* x = (a \<sharp> x \<and> as \<sharp>* x)"
+  by (auto simp add: fresh_star_def)
+
+lemma fresh_star_Un_elim:
+  "((as \<union> bs) \<sharp>* x \<Longrightarrow> PROP C) \<equiv> (as \<sharp>* x \<Longrightarrow> bs \<sharp>* x \<Longrightarrow> PROP C)"
+  unfolding fresh_star_def
+  apply(rule)
+  apply(erule meta_mp)
+  apply(auto)
+  done
+
+lemma fresh_star_insert_elim:
+  "(insert a as \<sharp>* x \<Longrightarrow> PROP C) \<equiv> (a \<sharp> x \<Longrightarrow> as \<sharp>* x \<Longrightarrow> PROP C)"
+  unfolding fresh_star_def
+  by rule (simp_all add: fresh_star_def)
+
+lemma fresh_star_empty_elim:
+  "({} \<sharp>* x \<Longrightarrow> PROP C) \<equiv> PROP C"
+  by (simp add: fresh_star_def)
+
+lemma fresh_star_unit_elim: 
+  shows "(a \<sharp>* () \<Longrightarrow> PROP C) \<equiv> PROP C"
+  by (simp add: fresh_star_def fresh_unit) 
+
+lemma fresh_star_prod_elim: 
+  shows "(a \<sharp>* (x, y) \<Longrightarrow> PROP C) \<equiv> (a \<sharp>* x \<Longrightarrow> a \<sharp>* y \<Longrightarrow> PROP C)"
+  by (rule, simp_all add: fresh_star_prod)
+
+lemma fresh_star_plus:
+  fixes p q::perm
+  shows "\<lbrakk>a \<sharp>* p;  a \<sharp>* q\<rbrakk> \<Longrightarrow> a \<sharp>* (p + q)"
+  unfolding fresh_star_def
+  by (simp add: fresh_plus_perm)
+
+lemma fresh_star_permute_iff:
+  shows "(p \<bullet> a) \<sharp>* (p \<bullet> x) \<longleftrightarrow> a \<sharp>* x"
+  unfolding fresh_star_def
+  by (metis mem_permute_iff permute_minus_cancel fresh_permute_iff)
+
+lemma fresh_star_eqvt:
+  shows "(p \<bullet> (as \<sharp>* x)) = (p \<bullet> as) \<sharp>* (p \<bullet> x)"
+unfolding fresh_star_def
+unfolding Ball_def
+apply(simp add: all_eqvt)
+apply(subst permute_fun_def)
+apply(simp add: imp_eqvt fresh_eqvt mem_eqvt)
+done
+
+section {* Avoiding of atom sets *}
+
+text {* 
+  For every set of atoms, there is another set of atoms
+  avoiding a finitely supported c and there is a permutation
+  which 'translates' between both sets.
+*}
+
+lemma at_set_avoiding_aux:
+  fixes Xs::"atom set"
+  and   As::"atom set"
+  assumes b: "Xs \<subseteq> As"
+  and     c: "finite As"
+  shows "\<exists>p. (p \<bullet> Xs) \<inter> As = {} \<and> (supp p) \<subseteq> (Xs \<union> (p \<bullet> Xs))"
+proof -
+  from b c have "finite Xs" by (rule finite_subset)
+  then show ?thesis using b
+  proof (induct rule: finite_subset_induct)
+    case empty
+    have "0 \<bullet> {} \<inter> As = {}" by simp
+    moreover
+    have "supp (0::perm) \<subseteq> {} \<union> 0 \<bullet> {}" by (simp add: supp_zero_perm)
+    ultimately show ?case by blast
+  next
+    case (insert x Xs)
+    then obtain p where
+      p1: "(p \<bullet> Xs) \<inter> As = {}" and 
+      p2: "supp p \<subseteq> (Xs \<union> (p \<bullet> Xs))" by blast
+    from `x \<in> As` p1 have "x \<notin> p \<bullet> Xs" by fast
+    with `x \<notin> Xs` p2 have "x \<notin> supp p" by fast
+    hence px: "p \<bullet> x = x" unfolding supp_perm by simp
+    have "finite (As \<union> p \<bullet> Xs)"
+      using `finite As` `finite Xs`
+      by (simp add: permute_set_eq_image)
+    then obtain y where "y \<notin> (As \<union> p \<bullet> Xs)" "sort_of y = sort_of x"
+      by (rule obtain_atom)
+    hence y: "y \<notin> As" "y \<notin> p \<bullet> Xs" "sort_of y = sort_of x"
+      by simp_all
+    let ?q = "(x \<rightleftharpoons> y) + p"
+    have q: "?q \<bullet> insert x Xs = insert y (p \<bullet> Xs)"
+      unfolding insert_eqvt
+      using `p \<bullet> x = x` `sort_of y = sort_of x`
+      using `x \<notin> p \<bullet> Xs` `y \<notin> p \<bullet> Xs`
+      by (simp add: swap_atom swap_set_not_in)
+    have "?q \<bullet> insert x Xs \<inter> As = {}"
+      using `y \<notin> As` `p \<bullet> Xs \<inter> As = {}`
+      unfolding q by simp
+    moreover
+    have "supp ?q \<subseteq> insert x Xs \<union> ?q \<bullet> insert x Xs"
+      using p2 unfolding q
+      apply (intro subset_trans [OF supp_plus_perm])
+      apply (auto simp add: supp_swap)
+      done
+    ultimately show ?case by blast
+  qed
+qed
+
+lemma at_set_avoiding:
+  assumes a: "finite Xs"
+  and     b: "finite (supp c)"
+  obtains p::"perm" where "(p \<bullet> Xs)\<sharp>*c" and "(supp p) \<subseteq> (Xs \<union> (p \<bullet> Xs))"
+  using a b at_set_avoiding_aux [where Xs="Xs" and As="Xs \<union> supp c"]
+  unfolding fresh_star_def fresh_def by blast
+
+
+section {* The freshness lemma according to Andrew Pitts *}
+
+lemma fresh_conv_MOST: 
+  shows "a \<sharp> x \<longleftrightarrow> (MOST b. (a \<rightleftharpoons> b) \<bullet> x = x)"
+  unfolding fresh_def supp_def MOST_iff_cofinite by simp
+
+lemma fresh_apply:
+  assumes "a \<sharp> f" and "a \<sharp> x" 
+  shows "a \<sharp> f x"
+  using assms unfolding fresh_conv_MOST
+  unfolding permute_fun_app_eq [where f=f]
+  by (elim MOST_rev_mp, simp)
+
+lemma freshness_lemma:
+  fixes h :: "'a::at \<Rightarrow> 'b::pt"
+  assumes a: "\<exists>a. atom a \<sharp> (h, h a)"
+  shows  "\<exists>x. \<forall>a. atom a \<sharp> h \<longrightarrow> h a = x"
+proof -
+  from a obtain b where a1: "atom b \<sharp> h" and a2: "atom b \<sharp> h b"
+    by (auto simp add: fresh_Pair)
+  show "\<exists>x. \<forall>a. atom a \<sharp> h \<longrightarrow> h a = x"
+  proof (intro exI allI impI)
+    fix a :: 'a
+    assume a3: "atom a \<sharp> h"
+    show "h a = h b"
+    proof (cases "a = b")
+      assume "a = b"
+      thus "h a = h b" by simp
+    next
+      assume "a \<noteq> b"
+      hence "atom a \<sharp> b" by (simp add: fresh_at_base)
+      with a3 have "atom a \<sharp> h b" by (rule fresh_apply)
+      with a2 have d1: "(atom b \<rightleftharpoons> atom a) \<bullet> (h b) = (h b)"
+        by (rule swap_fresh_fresh)
+      from a1 a3 have d2: "(atom b \<rightleftharpoons> atom a) \<bullet> h = h"
+        by (rule swap_fresh_fresh)
+      from d1 have "h b = (atom b \<rightleftharpoons> atom a) \<bullet> (h b)" by simp
+      also have "\<dots> = ((atom b \<rightleftharpoons> atom a) \<bullet> h) ((atom b \<rightleftharpoons> atom a) \<bullet> b)"
+        by (rule permute_fun_app_eq)
+      also have "\<dots> = h a"
+        using d2 by simp
+      finally show "h a = h b"  by simp
+    qed
+  qed
+qed
+
+lemma freshness_lemma_unique:
+  fixes h :: "'a::at \<Rightarrow> 'b::pt"
+  assumes a: "\<exists>a. atom a \<sharp> (h, h a)"
+  shows "\<exists>!x. \<forall>a. atom a \<sharp> h \<longrightarrow> h a = x"
+proof (rule ex_ex1I)
+  from a show "\<exists>x. \<forall>a. atom a \<sharp> h \<longrightarrow> h a = x"
+    by (rule freshness_lemma)
+next
+  fix x y
+  assume x: "\<forall>a. atom a \<sharp> h \<longrightarrow> h a = x"
+  assume y: "\<forall>a. atom a \<sharp> h \<longrightarrow> h a = y"
+  from a x y show "x = y"
+    by (auto simp add: fresh_Pair)
+qed
+
+text {* packaging the freshness lemma into a function *}
+
+definition
+  fresh_fun :: "('a::at \<Rightarrow> 'b::pt) \<Rightarrow> 'b"
+where
+  "fresh_fun h = (THE x. \<forall>a. atom a \<sharp> h \<longrightarrow> h a = x)"
+
+lemma fresh_fun_app:
+  fixes h :: "'a::at \<Rightarrow> 'b::pt"
+  assumes a: "\<exists>a. atom a \<sharp> (h, h a)"
+  assumes b: "atom a \<sharp> h"
+  shows "fresh_fun h = h a"
+unfolding fresh_fun_def
+proof (rule the_equality)
+  show "\<forall>a'. atom a' \<sharp> h \<longrightarrow> h a' = h a"
+  proof (intro strip)
+    fix a':: 'a
+    assume c: "atom a' \<sharp> h"
+    from a have "\<exists>x. \<forall>a. atom a \<sharp> h \<longrightarrow> h a = x" by (rule freshness_lemma)
+    with b c show "h a' = h a" by auto
+  qed
+next
+  fix fr :: 'b
+  assume "\<forall>a. atom a \<sharp> h \<longrightarrow> h a = fr"
+  with b show "fr = h a" by auto
+qed
+
+lemma fresh_fun_app':
+  fixes h :: "'a::at \<Rightarrow> 'b::pt"
+  assumes a: "atom a \<sharp> h" "atom a \<sharp> h a"
+  shows "fresh_fun h = h a"
+  apply (rule fresh_fun_app)
+  apply (auto simp add: fresh_Pair intro: a)
+  done
+
+lemma fresh_fun_eqvt:
+  fixes h :: "'a::at \<Rightarrow> 'b::pt"
+  assumes a: "\<exists>a. atom a \<sharp> (h, h a)"
+  shows "p \<bullet> (fresh_fun h) = fresh_fun (p \<bullet> h)"
+  using a
+  apply (clarsimp simp add: fresh_Pair)
+  apply (subst fresh_fun_app', assumption+)
+  apply (drule fresh_permute_iff [where p=p, THEN iffD2])
+  apply (drule fresh_permute_iff [where p=p, THEN iffD2])
+  apply (simp add: atom_eqvt permute_fun_app_eq [where f=h])
+  apply (erule (1) fresh_fun_app' [symmetric])
+  done
+
+lemma fresh_fun_supports:
+  fixes h :: "'a::at \<Rightarrow> 'b::pt"
+  assumes a: "\<exists>a. atom a \<sharp> (h, h a)"
+  shows "(supp h) supports (fresh_fun h)"
+  apply (simp add: supports_def fresh_def [symmetric])
+  apply (simp add: fresh_fun_eqvt [OF a] swap_fresh_fresh)
+  done
+
+notation fresh_fun (binder "FRESH " 10)
+
+lemma FRESH_f_iff:
+  fixes P :: "'a::at \<Rightarrow> 'b::pure"
+  fixes f :: "'b \<Rightarrow> 'c::pure"
+  assumes P: "finite (supp P)"
+  shows "(FRESH x. f (P x)) = f (FRESH x. P x)"
+proof -
+  obtain a::'a where "atom a \<notin> supp P"
+    using P by (rule obtain_at_base)
+  hence "atom a \<sharp> P"
+    by (simp add: fresh_def)
+  show "(FRESH x. f (P x)) = f (FRESH x. P x)"
+    apply (subst fresh_fun_app' [where a=a, OF _ pure_fresh])
+    apply (cut_tac `atom a \<sharp> P`)
+    apply (simp add: fresh_conv_MOST)
+    apply (elim MOST_rev_mp, rule MOST_I, clarify)
+    apply (simp add: permute_fun_def permute_pure expand_fun_eq)
+    apply (subst fresh_fun_app' [where a=a, OF `atom a \<sharp> P` pure_fresh])
+    apply (rule refl)
+    done
+qed
+
+lemma FRESH_binop_iff:
+  fixes P :: "'a::at \<Rightarrow> 'b::pure"
+  fixes Q :: "'a::at \<Rightarrow> 'c::pure"
+  fixes binop :: "'b \<Rightarrow> 'c \<Rightarrow> 'd::pure"
+  assumes P: "finite (supp P)" 
+  and     Q: "finite (supp Q)"
+  shows "(FRESH x. binop (P x) (Q x)) = binop (FRESH x. P x) (FRESH x. Q x)"
+proof -
+  from assms have "finite (supp P \<union> supp Q)" by simp
+  then obtain a::'a where "atom a \<notin> (supp P \<union> supp Q)"
+    by (rule obtain_at_base)
+  hence "atom a \<sharp> P" and "atom a \<sharp> Q"
+    by (simp_all add: fresh_def)
+  show ?thesis
+    apply (subst fresh_fun_app' [where a=a, OF _ pure_fresh])
+    apply (cut_tac `atom a \<sharp> P` `atom a \<sharp> Q`)
+    apply (simp add: fresh_conv_MOST)
+    apply (elim MOST_rev_mp, rule MOST_I, clarify)
+    apply (simp add: permute_fun_def permute_pure expand_fun_eq)
+    apply (subst fresh_fun_app' [where a=a, OF `atom a \<sharp> P` pure_fresh])
+    apply (subst fresh_fun_app' [where a=a, OF `atom a \<sharp> Q` pure_fresh])
+    apply (rule refl)
+    done
+qed
+
+lemma FRESH_conj_iff:
+  fixes P Q :: "'a::at \<Rightarrow> bool"
+  assumes P: "finite (supp P)" and Q: "finite (supp Q)"
+  shows "(FRESH x. P x \<and> Q x) \<longleftrightarrow> (FRESH x. P x) \<and> (FRESH x. Q x)"
+using P Q by (rule FRESH_binop_iff)
+
+lemma FRESH_disj_iff:
+  fixes P Q :: "'a::at \<Rightarrow> bool"
+  assumes P: "finite (supp P)" and Q: "finite (supp Q)"
+  shows "(FRESH x. P x \<or> Q x) \<longleftrightarrow> (FRESH x. P x) \<or> (FRESH x. Q x)"
+using P Q by (rule FRESH_binop_iff)
+
+
+section {* An example of a function without finite support *}
+
+primrec
+  nat_of :: "atom \<Rightarrow> nat"
+where
+  "nat_of (Atom s n) = n"
+
+lemma atom_eq_iff:
+  fixes a b :: atom
+  shows "a = b \<longleftrightarrow> sort_of a = sort_of b \<and> nat_of a = nat_of b"
+  by (induct a, induct b, simp)
+
+lemma not_fresh_nat_of:
+  shows "\<not> a \<sharp> nat_of"
+unfolding fresh_def supp_def
+proof (clarsimp)
+  assume "finite {b. (a \<rightleftharpoons> b) \<bullet> nat_of \<noteq> nat_of}"
+  hence "finite ({a} \<union> {b. (a \<rightleftharpoons> b) \<bullet> nat_of \<noteq> nat_of})"
+    by simp
+  then obtain b where
+    b1: "b \<noteq> a" and
+    b2: "sort_of b = sort_of a" and
+    b3: "(a \<rightleftharpoons> b) \<bullet> nat_of = nat_of"
+    by (rule obtain_atom) auto
+  have "nat_of a = (a \<rightleftharpoons> b) \<bullet> (nat_of a)" by (simp add: permute_nat_def)
+  also have "\<dots> = ((a \<rightleftharpoons> b) \<bullet> nat_of) ((a \<rightleftharpoons> b) \<bullet> a)" by (simp add: permute_fun_app_eq)
+  also have "\<dots> = nat_of ((a \<rightleftharpoons> b) \<bullet> a)" using b3 by simp
+  also have "\<dots> = nat_of b" using b2 by simp
+  finally have "nat_of a = nat_of b" by simp
+  with b2 have "a = b" by (simp add: atom_eq_iff)
+  with b1 show "False" by simp
+qed
+
+lemma supp_nat_of:
+  shows "supp nat_of = UNIV"
+  using not_fresh_nat_of [unfolded fresh_def] by auto
+
+
+section {* Support for sets of atoms *}
+
+lemma supp_finite_atom_set:
+  fixes S::"atom set"
+  assumes "finite S"
+  shows "supp S = S"
+  apply(rule finite_supp_unique)
+  apply(simp add: supports_def)
+  apply(simp add: swap_set_not_in)
+  apply(rule assms)
+  apply(simp add: swap_set_in)
+done
+
+
+section {* transpositions of permutations *}
+
+fun
+  add_perm 
+where
+  "add_perm [] = 0"
+| "add_perm ((a, b) # xs) = (a \<rightleftharpoons> b) + add_perm xs"
+
+lemma add_perm_append:
+  shows "add_perm (xs @ ys) = add_perm xs + add_perm ys"
+by (induct xs arbitrary: ys)
+   (auto simp add: add_assoc)
+
+lemma perm_list_exists:
+  fixes p::perm
+  shows "\<exists>xs. p = add_perm xs \<and> supp xs \<subseteq> supp p"
+apply(induct p taking: "\<lambda>p::perm. card (supp p)" rule: measure_induct)
+apply(rename_tac p)
+apply(case_tac "supp p = {}")
+apply(simp)
+apply(simp add: supp_perm)
+apply(rule_tac x="[]" in exI)
+apply(simp add: supp_Nil)
+apply(simp add: expand_perm_eq)
+apply(subgoal_tac "\<exists>x. x \<in> supp p")
+defer
+apply(auto)[1]
+apply(erule exE)
+apply(drule_tac x="p + (((- p) \<bullet> x) \<rightleftharpoons> x)" in spec)
+apply(drule mp)
+defer
+apply(erule exE)
+apply(rule_tac x="xs @ [((- p) \<bullet> x, x)]" in exI)
+apply(simp add: add_perm_append)
+apply(erule conjE)
+apply(drule sym)
+apply(simp)
+apply(simp add: expand_perm_eq)
+apply(simp add: supp_append)
+apply(simp add: supp_perm supp_Cons supp_Nil supp_Pair supp_atom)
+apply(rule conjI)
+prefer 2
+apply(auto)[1]
+apply (metis permute_atom_def_raw permute_minus_cancel(2))
+defer
+apply(rule psubset_card_mono)
+apply(simp add: finite_supp)
+apply(rule psubsetI)
+defer
+apply(subgoal_tac "x \<notin> supp (p + (- p \<bullet> x \<rightleftharpoons> x))")
+apply(blast)
+apply(simp add: supp_perm)
+defer
+apply(auto simp add: supp_perm)[1]
+apply(case_tac "x = xa")
+apply(simp)
+apply(case_tac "((- p) \<bullet> x) = xa")
+apply(simp)
+apply(case_tac "sort_of xa = sort_of x")
+apply(simp)
+apply(auto)[1]
+apply(simp)
+apply(simp)
+apply(subgoal_tac "{a. p \<bullet> (- p \<bullet> x \<rightleftharpoons> x) \<bullet> a \<noteq> a} \<subseteq> {a. p \<bullet> a \<noteq> a}")
+apply(blast)
+apply(auto simp add: supp_perm)[1]
+apply(case_tac "x = xa")
+apply(simp)
+apply(case_tac "((- p) \<bullet> x) = xa")
+apply(simp)
+apply(case_tac "sort_of xa = sort_of x")
+apply(simp)
+apply(auto)[1]
+apply(simp)
+apply(simp)
+done
+
+section {* Lemma about support and permutations *}
+
+lemma supp_perm_eq:
+  assumes a: "(supp x) \<sharp>* p"
+  shows "p \<bullet> x = x"
+proof -
+  obtain xs where eq: "p = add_perm xs" and sub: "supp xs \<subseteq> supp p"
+    using perm_list_exists by blast
+  from a have "\<forall>a \<in> supp p. a \<sharp> x"
+    by (auto simp add: fresh_star_def fresh_def supp_perm)
+  with eq sub have "\<forall>a \<in> supp xs. a \<sharp> x" by auto
+  then have "add_perm xs \<bullet> x = x" 
+    by (induct xs rule: add_perm.induct)
+       (simp_all add: supp_Cons supp_Pair supp_atom swap_fresh_fresh)
+  then show "p \<bullet> x = x" using eq by simp
+qed
+
+section {* at_set_avoiding2 *}
+
+lemma at_set_avoiding2:
+  assumes "finite xs"
+  and     "finite (supp c)" "finite (supp x)"
+  and     "xs \<sharp>* x"
+  shows "\<exists>p. (p \<bullet> xs) \<sharp>* c \<and> supp x \<sharp>* p"
+using assms
+apply(erule_tac c="(c, x)" in at_set_avoiding)
+apply(simp add: supp_Pair)
+apply(rule_tac x="p" in exI)
+apply(simp add: fresh_star_prod)
+apply(subgoal_tac "\<forall>a \<in> supp p. a \<sharp> x")
+apply(auto simp add: fresh_star_def fresh_def supp_perm)[1]
+apply(auto simp add: fresh_star_def fresh_def)
+done
+
+lemma at_set_avoiding2_atom:
+  assumes "finite (supp c)" "finite (supp x)"
+  and     b: "xa \<sharp> x"
+  shows "\<exists>p. (p \<bullet> xa) \<sharp> c \<and> supp x \<sharp>* p"
+proof -
+  have a: "{xa} \<sharp>* x" unfolding fresh_star_def by (simp add: b)
+  obtain p where p1: "(p \<bullet> {xa}) \<sharp>* c" and p2: "supp x \<sharp>* p"
+    using at_set_avoiding2[of "{xa}" "c" "x"] assms a by blast
+  have c: "(p \<bullet> xa) \<sharp> c" using p1
+    unfolding fresh_star_def Ball_def 
+    by (erule_tac x="p \<bullet> xa" in allE) (simp add: eqvts)
+  hence "p \<bullet> xa \<sharp> c \<and> supp x \<sharp>* p" using p2 by blast
+  then show ?thesis by blast
+qed
+
+end