diff -r a0c7290a4e27 -r 27cdc0a3a763 Nominal/FSet.thy
--- a/Nominal/FSet.thy	Wed Apr 21 12:25:52 2010 +0200
+++ b/Nominal/FSet.thy	Mon Apr 26 10:01:13 2010 +0200
@@ -71,6 +71,85 @@
        else f a (ffold_raw f z A)
      else z)"
 
+text {* Composition Quotient *}
+
+lemma list_rel_refl:
+  shows "(list_rel op \<approx>) r r"
+  by (rule list_rel_refl) (metis equivp_def fset_equivp)
+
+lemma compose_list_refl:
+  shows "(list_rel op \<approx> OOO op \<approx>) r r"
+proof
+  show c: "list_rel op \<approx> r r" by (rule list_rel_refl)
+  have d: "r \<approx> r" by (rule equivp_reflp[OF fset_equivp])
+  show b: "(op \<approx> OO list_rel op \<approx>) r r" by (rule pred_compI) (rule d, rule c)
+qed
+
+lemma Quotient_fset_list:
+  shows "Quotient (list_rel op \<approx>) (map abs_fset) (map rep_fset)"
+  by (fact list_quotient[OF Quotient_fset])
+
+lemma set_in_eq: "(\<forall>e. ((e \<in> A) \<longleftrightarrow> (e \<in> B))) \<equiv> A = B"
+  by (rule eq_reflection) auto
+
+lemma map_rel_cong: "b \<approx> ba \<Longrightarrow> map f b \<approx> map f ba"
+  unfolding list_eq.simps
+  by (simp only: set_map set_in_eq)
+
+lemma quotient_compose_list[quot_thm]:
+  shows  "Quotient ((list_rel op \<approx>) OOO (op \<approx>))
+    (abs_fset \<circ> (map abs_fset)) ((map rep_fset) \<circ> rep_fset)"
+  unfolding Quotient_def comp_def
+proof (intro conjI allI)
+  fix a r s
+  show "abs_fset (map abs_fset (map rep_fset (rep_fset a))) = a"
+    by (simp add: abs_o_rep[OF Quotient_fset] Quotient_abs_rep[OF Quotient_fset] map_id)
+  have b: "list_rel op \<approx> (map rep_fset (rep_fset a)) (map rep_fset (rep_fset a))"
+    by (rule list_rel_refl)
+  have c: "(op \<approx> OO list_rel op \<approx>) (map rep_fset (rep_fset a)) (map rep_fset (rep_fset a))"
+    by (rule, rule equivp_reflp[OF fset_equivp]) (rule b)
+  show "(list_rel op \<approx> OOO op \<approx>) (map rep_fset (rep_fset a)) (map rep_fset (rep_fset a))"
+    by (rule, rule list_rel_refl) (rule c)
+  show "(list_rel op \<approx> OOO op \<approx>) r s = ((list_rel op \<approx> OOO op \<approx>) r r \<and>
+        (list_rel op \<approx> OOO op \<approx>) s s \<and> abs_fset (map abs_fset r) = abs_fset (map abs_fset s))"
+  proof (intro iffI conjI)
+    show "(list_rel op \<approx> OOO op \<approx>) r r" by (rule compose_list_refl)
+    show "(list_rel op \<approx> OOO op \<approx>) s s" by (rule compose_list_refl)
+  next
+    assume a: "(list_rel op \<approx> OOO op \<approx>) r s"
+    then have b: "map abs_fset r \<approx> map abs_fset s" proof (elim pred_compE)
+      fix b ba
+      assume c: "list_rel op \<approx> r b"
+      assume d: "b \<approx> ba"
+      assume e: "list_rel op \<approx> ba s"
+      have f: "map abs_fset r = map abs_fset b"
+        using Quotient_rel[OF Quotient_fset_list] c by blast
+      have "map abs_fset ba = map abs_fset s"
+        using Quotient_rel[OF Quotient_fset_list] e by blast
+      then have g: "map abs_fset s = map abs_fset ba" by simp
+      then show "map abs_fset r \<approx> map abs_fset s" using d f map_rel_cong by simp
+    qed
+    then show "abs_fset (map abs_fset r) = abs_fset (map abs_fset s)"
+      using Quotient_rel[OF Quotient_fset] by blast
+  next
+    assume a: "(list_rel op \<approx> OOO op \<approx>) r r \<and> (list_rel op \<approx> OOO op \<approx>) s s
+      \<and> abs_fset (map abs_fset r) = abs_fset (map abs_fset s)"
+    then have s: "(list_rel op \<approx> OOO op \<approx>) s s" by simp
+    have d: "map abs_fset r \<approx> map abs_fset s"
+      by (subst Quotient_rel[OF Quotient_fset]) (simp add: a)
+    have b: "map rep_fset (map abs_fset r) \<approx> map rep_fset (map abs_fset s)"
+      by (rule map_rel_cong[OF d])
+    have y: "list_rel op \<approx> (map rep_fset (map abs_fset s)) s"
+      by (fact rep_abs_rsp_left[OF Quotient_fset_list, OF list_rel_refl[of s]])
+    have c: "(op \<approx> OO list_rel op \<approx>) (map rep_fset (map abs_fset r)) s"
+      by (rule pred_compI) (rule b, rule y)
+    have z: "list_rel op \<approx> r (map rep_fset (map abs_fset r))"
+      by (fact rep_abs_rsp[OF Quotient_fset_list, OF list_rel_refl[of r]])
+    then show "(list_rel op \<approx> OOO op \<approx>) r s"
+      using a c pred_compI by simp
+  qed
+qed
+
 text {* Respectfullness *}
 
 lemma [quot_respect]:
@@ -178,7 +257,7 @@
   apply (induct b)
   apply (simp_all add: not_memb_nil)
   apply (auto)
-  apply (simp_all add: memb_delete_raw not_memb_delete_raw_ident  rsp_fold_def  memb_cons_iff)
+  apply (simp_all add: memb_delete_raw not_memb_delete_raw_ident rsp_fold_def  memb_cons_iff)
   done
 
 lemma ffold_raw_rsp_pre:
@@ -217,6 +296,44 @@
   "(op = ===> op = ===> op \<approx> ===> op =) ffold_raw ffold_raw"
   by (simp add: memb_def[symmetric] ffold_raw_rsp_pre)
 
+lemma concat_rsp_pre:
+  assumes a: "list_rel op \<approx> x x'"
+  and     b: "x' \<approx> y'"
+  and     c: "list_rel op \<approx> y' y"
+  and     d: "\<exists>x\<in>set x. xa \<in> set x"
+  shows "\<exists>x\<in>set y. xa \<in> set x"
+proof -
+  obtain xb where e: "xb \<in> set x" and f: "xa \<in> set xb" using d by auto
+  have "\<exists>y. y \<in> set x' \<and> xb \<approx> y" by (rule list_rel_find_element[OF e a])
+  then obtain ya where h: "ya \<in> set x'" and i: "xb \<approx> ya" by auto
+  have j: "ya \<in> set y'" using b h by simp
+  have "\<exists>yb. yb \<in> set y \<and> ya \<approx> yb" by (rule list_rel_find_element[OF j c])
+  then show ?thesis using f i by auto
+qed
+
+lemma [quot_respect]:
+  shows "(list_rel op \<approx> OOO op \<approx> ===> op \<approx>) concat concat"
+proof (rule fun_relI, elim pred_compE)
+  fix a b ba bb
+  assume a: "list_rel op \<approx> a ba"
+  assume b: "ba \<approx> bb"
+  assume c: "list_rel op \<approx> bb b"
+  have "\<forall>x. (\<exists>xa\<in>set a. x \<in> set xa) = (\<exists>xa\<in>set b. x \<in> set xa)" proof
+    fix x
+    show "(\<exists>xa\<in>set a. x \<in> set xa) = (\<exists>xa\<in>set b. x \<in> set xa)" proof
+      assume d: "\<exists>xa\<in>set a. x \<in> set xa"
+      show "\<exists>xa\<in>set b. x \<in> set xa" by (rule concat_rsp_pre[OF a b c d])
+    next
+      assume e: "\<exists>xa\<in>set b. x \<in> set xa"
+      have a': "list_rel op \<approx> ba a" by (rule list_rel_symp[OF list_eq_equivp, OF a])
+      have b': "bb \<approx> ba" by (rule equivp_symp[OF list_eq_equivp, OF b])
+      have c': "list_rel op \<approx> b bb" by (rule list_rel_symp[OF list_eq_equivp, OF c])
+      show "\<exists>xa\<in>set a. x \<in> set xa" by (rule concat_rsp_pre[OF c' b' a' e])
+    qed
+  qed
+  then show "concat a \<approx> concat b" by simp
+qed
+
 text {* Distributive lattice with bot *}
 
 lemma sub_list_not_eq:
@@ -375,11 +492,124 @@
   "fin :: 'a \<Rightarrow> 'a fset \<Rightarrow> bool" is "memb"
 
 abbreviation
-  fnotin :: "'a \<Rightarrow> 'a fset \<Rightarrow> bool" ("_ |\<notin>| _" [50, 51] 50)
+  fnotin :: "'a \<Rightarrow> 'a fset \<Rightarrow> bool" (infix "|\<notin>|" 50)
 where
   "x |\<notin>| S \<equiv> \<not> (x |\<in>| S)"
 
-section {* Augmenting an fset -- @{const finsert} *}
+section {* Other constants on the Quotient Type *} 
+
+quotient_definition
+  "fcard :: 'a fset \<Rightarrow> nat" 
+is
+  "fcard_raw"
+
+quotient_definition
+  "fmap :: ('a \<Rightarrow> 'b) \<Rightarrow> 'a fset \<Rightarrow> 'b fset"
+is
+ "map"
+
+quotient_definition
+  "fdelete :: 'a fset \<Rightarrow> 'a \<Rightarrow> 'a fset" 
+  is "delete_raw"
+
+quotient_definition
+  "fset_to_set :: 'a fset \<Rightarrow> 'a set" 
+  is "set"
+
+quotient_definition
+  "ffold :: ('a \<Rightarrow> 'b \<Rightarrow> 'b) \<Rightarrow> 'b \<Rightarrow> 'a fset \<Rightarrow> 'b"
+  is "ffold_raw"
+
+quotient_definition
+  "fconcat :: ('a fset) fset \<Rightarrow> 'a fset"
+is
+  "concat"
+
+text {* Compositional Respectfullness and Preservation *}
+
+lemma [quot_respect]: "(list_rel op \<approx> OOO op \<approx>) [] []"
+  by (fact compose_list_refl)
+
+lemma [quot_preserve]: "(abs_fset \<circ> map f) [] = abs_fset []"
+  by simp
+
+lemma [quot_respect]:
+  "(op \<approx> ===> list_rel op \<approx> OOO op \<approx> ===> list_rel op \<approx> OOO op \<approx>) op # op #"
+  apply auto
+  apply (simp add: set_in_eq)
+  apply (rule_tac b="x # b" in pred_compI)
+  apply auto
+  apply (rule_tac b="x # ba" in pred_compI)
+  apply auto
+  done
+
+lemma [quot_preserve]:
+  "(rep_fset ---> (map rep_fset \<circ> rep_fset) ---> (abs_fset \<circ> map abs_fset)) op # = finsert"
+  by (simp add: expand_fun_eq Quotient_abs_rep[OF Quotient_fset]
+      abs_o_rep[OF Quotient_fset] map_id finsert_def)
+
+lemma [quot_preserve]:
+  "((map rep_fset \<circ> rep_fset) ---> (map rep_fset \<circ> rep_fset) ---> (abs_fset \<circ> map abs_fset)) op @ = funion"
+  by (simp add: expand_fun_eq Quotient_abs_rep[OF Quotient_fset]
+      abs_o_rep[OF Quotient_fset] map_id sup_fset_def)
+
+lemma list_rel_app_l:
+  assumes a: "reflp R"
+  and b: "list_rel R l r"
+  shows "list_rel R (z @ l) (z @ r)"
+  by (induct z) (simp_all add: b rev_iffD1[OF a meta_eq_to_obj_eq[OF reflp_def]])
+
+lemma append_rsp2_pre0:
+  assumes a:"list_rel op \<approx> x x'"
+  shows "list_rel op \<approx> (x @ z) (x' @ z)"
+  using a apply (induct x x' rule: list_induct2')
+  by simp_all (rule list_rel_refl)
+
+lemma append_rsp2_pre1:
+  assumes a:"list_rel op \<approx> x x'"
+  shows "list_rel op \<approx> (z @ x) (z @ x')"
+  using a apply (induct x x' arbitrary: z rule: list_induct2')
+  apply (rule list_rel_refl)
+  apply (simp_all del: list_eq.simps)
+  apply (rule list_rel_app_l)
+  apply (simp_all add: reflp_def)
+  done
+
+lemma append_rsp2_pre:
+  assumes a:"list_rel op \<approx> x x'"
+  and     b: "list_rel op \<approx> z z'"
+  shows "list_rel op \<approx> (x @ z) (x' @ z')"
+  apply (rule list_rel_transp[OF fset_equivp])
+  apply (rule append_rsp2_pre0)
+  apply (rule a)
+  using b apply (induct z z' rule: list_induct2')
+  apply (simp_all only: append_Nil2)
+  apply (rule list_rel_refl)
+  apply simp_all
+  apply (rule append_rsp2_pre1)
+  apply simp
+  done
+
+lemma [quot_respect]:
+  "(list_rel op \<approx> OOO op \<approx> ===> list_rel op \<approx> OOO op \<approx> ===> list_rel op \<approx> OOO op \<approx>) op @ op @"
+proof (intro fun_relI, elim pred_compE)
+  fix x y z w x' z' y' w' :: "'a list list"
+  assume a:"list_rel op \<approx> x x'"
+  and b:    "x' \<approx> y'"
+  and c:    "list_rel op \<approx> y' y"
+  assume aa: "list_rel op \<approx> z z'"
+  and bb:   "z' \<approx> w'"
+  and cc:   "list_rel op \<approx> w' w"
+  have a': "list_rel op \<approx> (x @ z) (x' @ z')" using a aa append_rsp2_pre by auto
+  have b': "x' @ z' \<approx> y' @ w'" using b bb by simp
+  have c': "list_rel op \<approx> (y' @ w') (y @ w)" using c cc append_rsp2_pre by auto
+  have d': "(op \<approx> OO list_rel op \<approx>) (x' @ z') (y @ w)"
+    by (rule pred_compI) (rule b', rule c')
+  show "(list_rel op \<approx> OOO op \<approx>) (x @ z) (y @ w)"
+    by (rule pred_compI) (rule a', rule d')
+qed
+
+text {* Raw theorems. Finsert, memb, singleron, sub_list *}
 
 lemma nil_not_cons:
   shows "\<not> ([] \<approx> x # xs)"
@@ -398,30 +628,20 @@
   shows "memb x xs \<Longrightarrow> memb x (y # xs)"
   by (simp add: memb_def)
 
-section {* Singletons *}
-
 lemma singleton_list_eq:
   shows "[x] \<approx> [y] \<longleftrightarrow> x = y"
   by (simp add: id_simps) auto
 
-section {* sub_list *}
-
 lemma sub_list_cons:
   "sub_list (x # xs) ys = (memb x ys \<and> sub_list xs ys)"
   by (auto simp add: memb_def sub_list_def)
 
-section {* Cardinality of finite sets *}
-
-quotient_definition
-  "fcard :: 'a fset \<Rightarrow> nat" 
-is
-  "fcard_raw"
+text {* Cardinality of finite sets *}
 
 lemma fcard_raw_0:
   shows "fcard_raw xs = 0 \<longleftrightarrow> xs \<approx> []"
   by (induct xs) (auto simp add: memb_def)
 
-
 lemma fcard_raw_not_memb:
   shows "\<not> memb x xs \<longleftrightarrow> fcard_raw (x # xs) = Suc (fcard_raw xs)"
   by auto
@@ -432,7 +652,7 @@
   using a
   by (induct xs) (auto simp add: memb_def split: if_splits)
 
-lemma singleton_fcard_1: 
+lemma singleton_fcard_1:
   shows "set xs = {x} \<Longrightarrow> fcard_raw xs = 1"
   by (induct xs) (auto simp add: memb_def subset_insert)
 
@@ -451,11 +671,7 @@
   assumes a: "fcard_raw A = Suc n"
   shows "\<exists>a. memb a A"
   using a
-  apply (induct A)
-  apply simp
-  apply (rule_tac x="a" in exI)
-  apply (simp add: memb_def)
-  done
+  by (induct A) (auto simp add: memb_def)
 
 lemma memb_card_not_0:
   assumes a: "memb a A"
@@ -466,12 +682,7 @@
   then show ?thesis using fcard_raw_0[of A] by simp
 qed
 
-section {* fmap *}
-
-quotient_definition
-  "fmap :: ('a \<Rightarrow> 'b) \<Rightarrow> 'a fset \<Rightarrow> 'b fset"
-is
- "map"
+text {* fmap *}
 
 lemma map_append:
   "map f (xs @ ys) \<approx> (map f xs) @ (map f ys)"
@@ -526,28 +737,10 @@
   "fcard_raw (delete_raw xs y) = (if memb y xs then fcard_raw xs - 1 else fcard_raw xs)"
   by (simp add: fdelete_raw_filter fcard_raw_delete_one)
 
-
-
-
-
 lemma finter_raw_empty:
   "finter_raw l [] = []"
   by (induct l) (simp_all add: not_memb_nil)
 
-section {* Constants on the Quotient Type *} 
-
-quotient_definition
-  "fdelete :: 'a fset \<Rightarrow> 'a \<Rightarrow> 'a fset" 
-  is "delete_raw"
-
-quotient_definition
-  "fset_to_set :: 'a fset \<Rightarrow> 'a set" 
-  is "set"
-
-quotient_definition
-  "ffold :: ('a \<Rightarrow> 'b \<Rightarrow> 'b) \<Rightarrow> 'b \<Rightarrow> 'a fset \<Rightarrow> 'b"
-  is "ffold_raw"
-
 lemma set_cong: 
   shows "(set x = set y) = (x \<approx> y)"
   by auto
@@ -556,12 +749,6 @@
   "inj f \<Longrightarrow> (map f l \<approx> map f m) = (l \<approx> m)"
   by (simp add: expand_set_eq[symmetric] inj_image_eq_iff)
 
-quotient_definition
-  "fconcat :: ('a fset) fset \<Rightarrow> 'a fset"
-is
-  "concat"
-
-
 text {* alternate formulation with a different decomposition principle
   and a proof of equivalence *}
 
@@ -604,42 +791,44 @@
   "xs \<approx> ys \<Longrightarrow> delete_raw xs x \<approx> delete_raw ys x"
   by (simp add: memb_def[symmetric] memb_delete_raw)
 
-lemma list_eq2_equiv_aux:
-  assumes a: "fcard_raw l = n"
-  and b: "l \<approx> r"
-  shows "list_eq2 l r"
-using a b
-proof (induct n arbitrary: l r)
-  case 0
-  have "fcard_raw l = 0" by fact
-  then have "\<forall>x. \<not> memb x l" using memb_card_not_0[of _ l] by auto
-  then have z: "l = []" using no_memb_nil by auto
-  then have "r = []" using `l \<approx> r` by simp
-  then show ?case using z list_eq2_refl by simp
-next
-  case (Suc m)
-  have b: "l \<approx> r" by fact
-  have d: "fcard_raw l = Suc m" by fact
-  have "\<exists>a. memb a l" by (rule fcard_raw_suc_memb[OF d])
-  then obtain a where e: "memb a l" by auto
-  then have e': "memb a r" using list_eq.simps[simplified memb_def[symmetric], of l r] b by auto
-  have f: "fcard_raw (delete_raw l a) = m" using fcard_raw_delete[of l a] e d by simp
-  have g: "delete_raw l a \<approx> delete_raw r a" using delete_raw_rsp[OF b] by simp
-  have g': "list_eq2 (delete_raw l a) (delete_raw r a)" by (rule Suc.hyps[OF f g])
-  have h: "list_eq2 (a # delete_raw l a) (a # delete_raw r a)" by (rule list_eq2.intros(5)[OF g'])
-  have i: "list_eq2 l (a # delete_raw l a)" by (rule list_eq2.intros(3)[OF memb_delete_list_eq2[OF e]])
-  have "list_eq2 l (a # delete_raw r a)" by (rule list_eq2.intros(6)[OF i h])
-  then show ?case using list_eq2.intros(6)[OF _ memb_delete_list_eq2[OF e']] by simp
-qed
-
 lemma list_eq2_equiv:
   "(l \<approx> r) \<longleftrightarrow> (list_eq2 l r)"
 proof
   show "list_eq2 l r \<Longrightarrow> l \<approx> r" by (induct rule: list_eq2.induct) auto
-  show "l \<approx> r \<Longrightarrow> list_eq2 l r" using list_eq2_equiv_aux by blast
+next
+  {
+    fix n
+    assume a: "fcard_raw l = n" and b: "l \<approx> r"
+    have "list_eq2 l r"
+      using a b
+    proof (induct n arbitrary: l r)
+      case 0
+      have "fcard_raw l = 0" by fact
+      then have "\<forall>x. \<not> memb x l" using memb_card_not_0[of _ l] by auto
+      then have z: "l = []" using no_memb_nil by auto
+      then have "r = []" using `l \<approx> r` by simp
+      then show ?case using z list_eq2_refl by simp
+    next
+      case (Suc m)
+      have b: "l \<approx> r" by fact
+      have d: "fcard_raw l = Suc m" by fact
+      have "\<exists>a. memb a l" by (rule fcard_raw_suc_memb[OF d])
+      then obtain a where e: "memb a l" by auto
+      then have e': "memb a r" using list_eq.simps[simplified memb_def[symmetric], of l r] b by auto
+      have f: "fcard_raw (delete_raw l a) = m" using fcard_raw_delete[of l a] e d by simp
+      have g: "delete_raw l a \<approx> delete_raw r a" using delete_raw_rsp[OF b] by simp
+      have g': "list_eq2 (delete_raw l a) (delete_raw r a)" by (rule Suc.hyps[OF f g])
+      have h: "list_eq2 (a # delete_raw l a) (a # delete_raw r a)" by (rule list_eq2.intros(5)[OF g'])
+      have i: "list_eq2 l (a # delete_raw l a)"
+        by (rule list_eq2.intros(3)[OF memb_delete_list_eq2[OF e]])
+      have "list_eq2 l (a # delete_raw r a)" by (rule list_eq2.intros(6)[OF i h])
+      then show ?case using list_eq2.intros(6)[OF _ memb_delete_list_eq2[OF e']] by simp
+    qed
+    }
+  then show "l \<approx> r \<Longrightarrow> list_eq2 l r" by blast
 qed
 
-section {* lifted part *}
+text {* Lifted theorems *}
 
 lemma not_fin_fnil: "x |\<notin>| {||}"
   by (lifting not_memb_nil)
@@ -742,10 +931,6 @@
   shows "S |\<union>| {||} = S"
   by (lifting append_Nil2)
 
-thm sup.commute[where 'a="'a fset"]
-
-thm sup.assoc[where 'a="'a fset"]
-
 lemma singleton_union_left:
   "{|a|} |\<union>| S = finsert a S"
   by simp
@@ -779,15 +964,7 @@
   case (finsert x S)
   have asm: "P S" by fact
   show "P (finsert x S)"
-  proof(cases "x |\<in>| S")
-    case True
-    have "x |\<in>| S" by fact
-    then show "P (finsert x S)" using asm by simp
-  next
-    case False
-    have "x |\<notin>| S" by fact
-    then show "P (finsert x S)" using prem2 asm by simp
-  qed
+    by (cases "x |\<in>| S") (simp_all add: asm prem2)
 qed
 
 lemma fset_induct2:
@@ -876,7 +1053,8 @@
   "(finsert x xs |\<subseteq>| ys) = (x |\<in>| ys \<and> xs |\<subseteq>| ys)"
   by (lifting sub_list_cons)
 
-thm sub_list_def[simplified memb_def[symmetric], quot_lifted, no_vars]
+lemma "xs |\<subseteq>| ys \<equiv> \<forall>x. x |\<in>| xs \<longrightarrow> x |\<in>| ys"
+  by (lifting sub_list_def[simplified memb_def[symmetric]])
 
 lemma fsubset_fin: "xs |\<subseteq>| ys = (\<forall>x. x |\<in>| xs \<longrightarrow> x |\<in>| ys)"
 by (rule meta_eq_to_obj_eq)
@@ -911,6 +1089,19 @@
   using assms
   by (lifting list_eq2.induct[simplified list_eq2_equiv[symmetric]])
 
+text {* concat *}
+
+lemma fconcat_empty:
+  shows "fconcat {||} = {||}"
+  by (lifting concat.simps(1))
+
+lemma fconcat_insert:
+  shows "fconcat (finsert x S) = x |\<union>| fconcat S"
+  by (lifting concat.simps(2))
+
+lemma "fconcat (xs |\<union>| ys) = fconcat xs |\<union>| fconcat ys"
+  by (lifting concat_append)
+
 ML {*
 fun dest_fsetT (Type ("FSet.fset", [T])) = T
   | dest_fsetT T = raise TYPE ("dest_fsetT: fset type expected", [T], []);