Theory FaceDivisionProps

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theory FaceDivisionProps
imports Plane EnumeratorProps
begin

(*  ID:         $Id: FaceDivisionProps.thy,v 1.3 2006/01/13 19:18:51 nipkow Exp $
    Author:     Gertrud Bauer, Tobias Nipkow
*)

header{*Properties of Face Division*}

theory FaceDivisionProps
imports Plane EnumeratorProps
begin

subsection{* Finality *}

(********************* makeFaceFinal ****************************)

lemma vertices_makeFaceFinal: "vertices(makeFaceFinal f g) = vertices g"
by(induct g)(simp add:vertices_graph_def makeFaceFinal_def)

lemma edges_makeFaceFinal: "\<E> (makeFaceFinal f g) = \<E> g"
proof -
  { fix fs
    have "(\<Union>f∈set (makeFaceFinalFaceList f fs) edges f) = (\<Union>f∈ set fs edges f)"
    apply(unfold makeFaceFinalFaceList_def)
    apply(induct f)
    by(induct fs) simp_all }
  thus ?thesis by(simp add:edges_graph_def makeFaceFinal_def)
qed


lemma nonFins_mkFaceFin:
  "nonFinals(makeFaceFinal f g) = remove1 f (nonFinals g)"
by(simp add:makeFaceFinal_def nonFinals_def makeFaceFinalFaceList_def
            filter_replace)

lemma in_set_repl_setFin:
  "f ∈ set fs ==> final f ==> f ∈ set (replace f' [setFinal f'] fs)"
by (induct fs) auto

lemma in_set_repl:  "f ∈ set fs ==> f ≠ f' ==> f ∈ set (replace f' fs' fs)"
by (induct fs) auto

lemma makeFaceFinals_preserve_finals:
  "f ∈ set (finals g) ==> f ∈ set (finals (makeFaceFinal f' g))"
by (induct g)
   (simp add:makeFaceFinal_def finals_def makeFaceFinalFaceList_def
             in_set_repl_setFin)


lemma len_faces_makeFaceFinal[simp]:
 "|faces (makeFaceFinal f g)| = |faces g|"
by(simp add:makeFaceFinal_def makeFaceFinalFaceList_def)

lemma len_finals_makeFaceFinal:
 "f ∈ \<F> g ==> ¬ final f ==> |finals (makeFaceFinal f g)| = |finals g| + 1"
by(simp add:makeFaceFinal_def finals_def makeFaceFinalFaceList_def
            length_filter_replace1)

lemma len_nonFinals_makeFaceFinal:
 "[| ¬ final f; f ∈ \<F> g|]
  ==> |nonFinals (makeFaceFinal f g)| = |nonFinals g| - 1"
by(simp add:makeFaceFinal_def nonFinals_def makeFaceFinalFaceList_def
            length_filter_replace2)


lemma set_finals_makeFaceFinal[simp]: "distinct(faces g) ==> f ∈ \<F> g ==>
  set(finals (makeFaceFinal f g)) = insert (setFinal f) (set(finals g))"
by(auto simp:finals_def makeFaceFinal_def makeFaceFinalFaceList_def
                distinct_set_replace)


lemma splitFace_preserve_final:
  "f ∈ set (finals g) ==> ¬ final f' ==>
   f ∈ set (finals (snd (snd (splitFace g i j f' ns))))"
  by (induct g) (auto simp add: splitFace_def finals_def split_def
                      intro: in_set_repl)

lemma splitFace_nonFinal_face:
  "¬ final (fst (snd (splitFace g i j f' ns)))"
  by (simp add: splitFace_def split_def split_face_def)


lemma subdivFace'_preserve_finals:
  "!!n i f' g. f ∈ set (finals g) ==>  ¬ final f' ==>
   f ∈ set (finals (subdivFace' g f' i n is))"
proof (induct "is")
  case Nil then show ?case by(simp add:makeFaceFinals_preserve_finals)
next
  case (Cons j "js") then show ?case
  proof (cases j)
    case None with Cons show ?thesis by simp
  next
    case (Some sj)
    with Cons show ?thesis
      by (auto simp: splitFace_preserve_final splitFace_nonFinal_face split_def)
  qed
qed

lemma subdivFace_pres_finals:
  "f ∈ set (finals g) ==> ¬ final f' ==>
   f ∈ set (finals (subdivFace g f' is))"
by(simp add:subdivFace_def subdivFace'_preserve_finals)


declare Nat.diff_is_0_eq' [simp del]

(********************* section is_prefix ****************************)
subsection {* @{text "is_prefix"} *}

constdefs is_prefix :: "'a list => 'a list => bool"
"is_prefix ls vs ≡  (∃ bs. vs = ls @ bs)"

lemma is_prefix_add:
  "is_prefix ls vs ==> is_prefix (as @ ls) (as @ vs)" by (simp add: is_prefix_def)

lemma is_prefix_hd[simp]:
  "is_prefix [l] vs = (l = hd vs ∧ vs ≠ [])"
  apply (rule iffI) apply (auto simp: is_prefix_def)
  apply (intro exI) apply (subgoal_tac "vs = hd vs # tl vs") apply assumption by auto

lemma is_prefix_f[simp]:
  "is_prefix (a#as) (a#vs) = is_prefix as vs" by (auto simp: is_prefix_def)

lemma splitAt_is_prefix: "ram ∈ set vs ==> is_prefix (fst (splitAt ram vs) @ [ram]) vs"
by (auto dest!: splitAt_ram simp: is_prefix_def)


(********************* section is_postfix ****************************)
subsection {* @{text "is_postfix"} *}

constdefs is_postfix :: "'a list => 'a list => bool"
"is_postfix ls vs ≡  (∃ as. vs = as @ ls)"

lemma is_postfix_add:
  "is_postfix ls vs ==> is_postfix (ls @ bs) (vs @ bs)" by (simp add: is_postfix_def)


lemma is_pre_post_eq:
  "distinct vs ==> ls ≠ [] ==> is_prefix ls vs ==> is_postfix ls vs ==> ls = vs"
proof -
  assume d: "distinct vs" and ls: "ls ≠ []" and ispre: "is_prefix ls vs" and ispost:" is_postfix ls vs"
  from ls have "hd ls # tl ls = ls" by auto
  from ispre obtain bs where vs1: "vs = ls @ bs"  apply (simp add: is_prefix_def) by auto
  from ls vs1 have vs2: "vs = hd ls # tl ls @ bs" by auto
  from ispost obtain as where vs3: "vs = as @ ls"  apply (simp add: is_postfix_def) by auto
  from ls vs3 have vs4: "vs = as @ hd ls # tl ls" by auto
  from d vs2 vs4 have "as = []" apply (rule_tac dist_at1) apply assumption apply assumption by auto
  with ls vs4 show ?thesis by auto
qed

lemma splitAt_is_postfix: "ram ∈ set vs ==> is_postfix (ram # snd (splitAt ram vs)) vs"
by (auto dest!: splitAt_ram simp: is_postfix_def)


(******************** section is_sublist *********************************)
subsection {* @{text"is_sublist"} *}

constdefs is_sublist :: "'a list => 'a list => bool"
"is_sublist ls vs ≡  (∃ as bs. vs = as @ ls @ bs)"

lemma is_prefix_sublist:
  "is_prefix ls vs ==> is_sublist ls vs" by (auto simp: is_prefix_def is_sublist_def)

lemma is_postfix_sublist:
  "is_postfix ls vs ==> is_sublist ls vs" by (force simp: is_postfix_def is_sublist_def)

lemma is_sublist_trans: "is_sublist as bs ==> is_sublist bs cs ==> is_sublist as cs"
  apply (simp add: is_sublist_def) apply (elim exE)
  apply (subgoal_tac "cs = (asaa @ asa) @ as @ (bsa @ bsaa)")
  apply (intro exI)  apply assumption by force

lemma is_sublist_add: "is_sublist as bs ==> is_sublist as (xs @ bs @ ys)"
  apply (simp add: is_sublist_def) apply (elim exE)
  apply (subgoal_tac "xs @ bs @ ys = (xs @ asa) @ as @ (bsa @ ys)")
  apply (intro exI) apply assumption by auto


lemma is_sublist_rec:
"is_sublist xs ys =
 (if length xs > length ys then False else
  if xs = take (length xs) ys then True else is_sublist xs (tl ys))"
proof (simp add:is_sublist_def)
  case goal1 show ?case
  proof
    case goal1 show ?case
    proof
      case goal1 note xs = goal1
      show ?case
      proof
        case goal1 show ?case by auto
      next
        case goal2 show ?case
        proof
          case goal1
          have "ys = take |xs| ys @ drop |xs| ys" by simp
          also have "… = [] @ xs @ drop |xs| ys" by(simp add:xs[symmetric])
          finally show ?case by blast
        qed
      qed
    qed
  next
    case goal2 show ?case
    proof
      case goal1 note xs_neq = this
      show ?case
      proof
        case goal1 show ?case by auto
      next
        case goal2 show ?case
        proof
          case goal1 note not_less = this show ?case
          proof
            case goal1
            then obtain as bs where ys: "ys = as @ xs @ bs" by blast
            have "as ≠ []" using xs_neq ys by auto
            then obtain a as' where "as = a # as'"
              by (simp add:neq_Nil_conv) blast
            hence "tl ys = as' @ xs @ bs" by(simp add:ys)
            thus ?case by blast
          next
            case goal2
            then obtain as bs where ys: "tl ys = as @ xs @ bs" by blast
            have "ys ≠ []" using xs_neq not_less by auto
            then obtain y ys' where "ys = y # ys'"
              by (simp add:neq_Nil_conv) blast
            hence "ys = (y#as) @ xs @ bs" using ys by simp
            thus ?case by blast
          qed
        qed
      qed
    qed
  qed
qed


lemma not_sublist_len[simp]:
 "|ys| < |xs| ==> ¬ is_sublist xs ys"
by(simp add:is_sublist_rec)

lemma is_sublist_simp[simp]: "a ≠ v ==> is_sublist (a#as) (v#vs) = is_sublist (a#as) vs"
proof
  assume av: "a ≠ v" and subl: "is_sublist (a # as) (v # vs)"
  then obtain rs ts where vvs: "v#vs = rs @ (a # as) @ ts" by (auto simp: is_sublist_def)
  with av have "rs ≠ []" by auto
  with vvs have "tl (v#vs) = tl rs @ a # as @ ts" by auto
  then have "vs = tl rs @ a # as @ ts" by auto
  then show "is_sublist (a # as) vs" by (auto simp: is_sublist_def)
next
  assume av: "a ≠ v" and subl: "is_sublist (a # as) vs"
  then show "is_sublist (a # as) (v # vs)" apply (auto simp: is_sublist_def)  apply (intro exI)
    apply (subgoal_tac "v # asa @ a # as @ bs = (v # asa) @ a # as @ bs") apply assumption by auto
qed

lemma is_sublist_id[simp]: "is_sublist vs vs" apply (auto simp: is_sublist_def) apply (intro exI)
  apply (subgoal_tac "vs = [] @ vs @ []") by (assumption) auto

lemma is_sublist_in: "is_sublist (a#as) vs ==> a ∈ set vs" by (auto simp: is_sublist_def)

lemma is_sublist_in1: "is_sublist [x,y] vs ==> y ∈ set vs" by (auto simp: is_sublist_def)

lemma is_sublist_notlast[simp]: "distinct vs ==> x = last vs ==> ¬ is_sublist [x,y] vs"
proof
  assume dvs: "distinct vs" and xl: "x = last vs" and subl:"is_sublist [x, y] vs"
  then obtain rs ts where "vs = rs @ x # y # ts" by (auto simp: is_sublist_def)
  def as ≡  "rs @ [x]"
  def bs ≡  "y # ts"
  then have bsne: "bs ≠ []" by auto
  from as_def bs_def have vs: "vs = as @ bs" by auto
  with as_def have xas: "x ∈ set as" by auto
  from bsne vs have "last vs = last bs" by auto
  with xl have "x = last bs" by auto
  with bsne have "bs = (butlast bs) @ [x]" by auto
  then have "x ∈ set bs" by (induct bs) auto
  with xas vs dvs show False by auto
qed

lemma is_sublist_nth1: "is_sublist [x,y] ls ==>
  ∃ i j. i < length ls ∧ j < length ls ∧ ls!i = x ∧ ls!j = y ∧ Suc i = j"
proof -
  assume subl: "is_sublist [x,y] ls"
  then obtain as bs where "ls = as @ x # y # bs" by (auto simp: is_sublist_def)
  then have "(length as) < length ls ∧ (Suc (length as)) < length ls ∧ ls!(length as) = x
       ∧ ls!(Suc (length as)) = y ∧ Suc (length as) = (Suc (length as))"
    apply auto apply (induct as) by auto
  then show ?thesis by auto
qed

lemma is_sublist_nth2: "∃ i j. i < length ls ∧ j < length ls ∧ ls!i = x ∧ ls!j = y ∧ Suc i = j ==>
 is_sublist [x,y] ls "
proof -
  assume "∃ i j. i < length ls ∧ j < length ls ∧ ls!i = x ∧ ls!j = y ∧ Suc i = j"
  then obtain i j where vors: "i < length ls ∧ j < length ls ∧ ls!i = x ∧ ls!j = y ∧ Suc i = j" by auto
  then have "ls = take (Suc (Suc i)) ls @ drop (Suc (Suc i)) ls" by auto
  with vors have "ls = take (Suc i) ls @ [ls! (Suc i)] @ drop (Suc (Suc i)) ls"
    by (auto simp: take_Suc_conv_app_nth)
  with vors have "ls = take i ls @ [ls!i] @ [ls! (Suc i)] @ drop (Suc (Suc i)) ls"
   by (auto simp: take_Suc_conv_app_nth)
  with vors show ?thesis by (auto simp: is_sublist_def)
qed

lemma is_sublist_nth_eq: "(∃ i j. i < length ls ∧ j < length ls ∧ ls!i = x
  ∧ ls!j = y ∧ Suc i = j) = is_sublist [x,y] ls"
apply (intro iffI) apply (rule is_sublist_nth2) apply assumption apply  (rule is_sublist_nth1) .

lemma is_sublist_tl: "is_sublist (a # as) vs ==> is_sublist as vs" apply (simp add: is_sublist_def)
  apply (elim exE) apply (intro exI)
  apply (subgoal_tac "vs = (asa @ [a]) @ as @ bs") apply assumption by auto

lemma is_sublist_hd: "is_sublist (a # as) vs ==> is_sublist [a] vs" apply (simp add: is_sublist_def) by auto

lemma is_sublist_hd_eq[simp]: "(is_sublist [a] vs) = (a ∈ set vs)" apply (rule_tac iffI)
  apply (simp add: is_sublist_def) apply force
  apply (simp add: is_sublist_def) apply (induct vs) apply force apply (case_tac "a = aa") apply force
  apply (subgoal_tac "a ∈ set vs") apply simp apply (elim exE) apply (intro exI)
  apply (subgoal_tac "aa # vs = (aa # as) @ a # bs") apply (assumption) by auto

lemma is_sublist_distinct_prefix:
  "is_sublist (v#as) (v # vs) ==> distinct (v # vs) ==> is_prefix as vs"
proof -
  assume d:  "distinct (v # vs)" and subl: "is_sublist (v # as) (v # vs)"
  from subl obtain rs ts where v_vs: "v # vs = rs @ (v # as) @ ts" by (simp add: is_sublist_def) auto
  from d have v: "v ∉ set vs" by auto
  then have "¬ is_sublist (v # as) vs" by (auto dest: is_sublist_hd)
  with v_vs have "rs = []" apply (cases rs) by (auto simp: is_sublist_def)
  with v_vs show "is_prefix as vs" by (auto simp: is_prefix_def)
qed

lemma is_sublist_distinct[intro]:
  "is_sublist as vs ==> distinct vs ==> distinct as" by (auto simp: is_sublist_def)

lemma is_sublist_x_last: "distinct vs ==> x = last vs ==> ¬ is_sublist [x,y] vs"
proof
  assume d: "distinct vs" and xl: "x = last vs" and subl: "is_sublist [x, y] vs"
  then obtain rs ts where vs: "vs = rs @ x # y # ts" by (auto simp: is_sublist_def)
  def as ≡ "rs @ [x]"
  def bs ≡ "y # ts"
  then have bsne: "bs ≠ []" by auto
  from as_def bs_def have vs: "vs = as @ bs" by auto
  from as_def have xas: "x ∈ set as" by auto
  from vs bs_def have "last vs = last bs" by auto
  with xl have "x = last bs" by auto
  with bsne have "x ∈ set bs" by (induct bs) auto
  with d xas vs show False by auto
qed

lemma is_sublist_y_hd: "distinct vs ==> y = hd vs ==> ¬ is_sublist [x,y] vs"
proof
  assume d: "distinct vs" and yh: "y = hd vs" and subl: "is_sublist [x, y] vs"
  then obtain rs ts where vs: "vs = rs @ x # y # ts" by (auto simp: is_sublist_def)
  def as ≡ "rs @ [x]"
  then have asne: "as ≠ []" by auto
  def bs ≡ "y # ts"
  then have bsne: "bs ≠ []" by auto
  from as_def bs_def have vs2: "vs = as @ bs" by auto
  from bs_def have xbs: "y ∈ set bs" by auto
  from vs2 asne have "hd vs = hd as" by simp
  with yh have "y = hd as" by auto
  with asne have "y ∈ set as" by (induct as) auto
  with d xbs vs2 show False by auto
qed

lemma is_sublist_at1: "distinct (as @ bs) ==> is_sublist [x,y] (as @ bs) ==> x ≠ (last as)  ==>
  is_sublist [x,y] as ∨ is_sublist [x,y] bs"
proof (cases "x ∈ set as")
  assume d: "distinct (as @ bs)"  and subl: "is_sublist [x, y] (as @ bs)" and xnl: "x ≠ last as"
  def vs ≡ "as @ bs"
  with d have dvs: "distinct vs" by auto
  case True
  with xnl subl have ind: "is_sublist (as@bs) vs ==> is_sublist [x, y] as"
  proof (induct as)
    case Nil then show ?case by force
  next
    case (Cons a as)
    assume ih: "[|is_sublist (as@bs) vs; x ≠ last as; is_sublist [x,y] (as @ bs); x ∈ set as|] ==>
      is_sublist [x, y] as" and subl_aas_vs: "is_sublist ((a # as) @ bs) vs"
      and xnl2: "x ≠ last (a # as)" and subl2: "is_sublist [x, y] ((a # as) @ bs)"
      and x: "x ∈ set (a # as)"
    then have rule1: "x ≠ a ==> is_sublist [x,y] as" apply (cases "as = []") apply simp
      apply (rule_tac ih) by (auto dest: is_sublist_tl)

    from dvs subl_aas_vs have daas: "distinct (a # as @ bs)" apply (rule_tac is_sublist_distinct) by auto
    from xnl2 have asne: "x = a ==> as ≠ []" by auto
    with subl2 daas have yhdas: "x = a ==> y = hd as" apply simp apply (drule_tac is_sublist_distinct_prefix) by auto
    with asne have "x = a ==> as = y # tl as" by auto
    with asne yhdas have "x = a ==> is_prefix [x,y] (a # as)" by auto
    then have rule2: "x = a ==> is_sublist [x,y] (a # as)" by (simp add: is_prefix_sublist)

    from rule1 rule2 show ?case by (cases "x = a") auto
  qed
  from vs_def d have "is_sublist [x, y] as" by (rule_tac ind) auto
  then show ?thesis by auto
next
  assume d: "distinct (as @ bs)"  and subl: "is_sublist [x, y] (as @ bs)" and xnl: "x ≠ last as"
  def ars ≡ "as"
  case False
  with ars_def have xars: "x ∉ set ars" by auto
  from subl have ind: "is_sublist as ars ==> is_sublist [x, y] bs"
  proof (induct as)
    case Nil then show ?case by auto
  next
    case (Cons a as)
    assume ih: "[|is_sublist as ars; is_sublist [x, y] (as @ bs)|] ==> is_sublist [x, y] bs"
      and subl_aasbsvs: "is_sublist (a # as) ars" and subl2: "is_sublist [x, y] ((a # as) @ bs)"
    from subl_aasbsvs ars_def False have "x ≠ a" by (auto simp:is_sublist_in)
    with subl_aasbsvs subl2 show ?thesis apply (rule_tac ih) by (auto dest: is_sublist_tl)
  qed
  from ars_def have "is_sublist [x, y] bs" by (rule_tac ind) auto
  then show ?thesis by auto
qed

lemma is_sublist_at2: "distinct (as @ bs) ==> is_sublist [x,y] (as @ bs) ==> x ≠ (last as)  ==>
   is_sublist [x,y] as ≠  is_sublist [x,y] bs"
  apply auto
  apply (subgoal_tac "x ∈ set as")
  apply (subgoal_tac "x ∈ set bs")
  apply (subgoal_tac "x ∈ (set as ∩ set bs)") apply simp apply force apply (force simp:is_sublist_in)
  apply (force simp:is_sublist_in)  (* apply force+ *)
  apply (subgoal_tac "distinct (as @ bs)")
  apply (frule is_sublist_at1) by auto

lemma is_sublist_at3: "distinct (as @ bs) ==> is_sublist [x,y] (as @ bs) ==>
  (is_sublist [x,y] as ∨ is_sublist [x,y] bs) ∨ x = last as"
  apply (rule disjCI) apply (rule is_sublist_at1) by auto

lemma is_sublist_at4: "distinct (as @ bs) ==> is_sublist [x,y] (as @ bs) ==>
  as ≠ [] ==> x = last as ==> y = hd bs"
proof -
  assume d: "distinct (as @ bs)" and subl: "is_sublist [x,y] (as @ bs)"
    and asne: "as ≠ []" and xl: "x = last as"
  def vs ≡ "as @ bs"
  with subl have "is_sublist [x,y] vs" by auto
  then obtain rs ts where vs2: "vs = rs @ x # y # ts" by (auto simp: is_sublist_def)
  from vs_def d have dvs:"distinct vs" by auto
  from asne xl have as:"as = butlast as @ [x]" by auto
  with vs_def have vs3: "vs = butlast as @ x # bs" by auto
  from dvs vs2 vs3 have "rs = butlast as" apply (rule_tac dist_at1) by auto
  then have "rs @ [x] = butlast as @ [x]" by auto
  with as have "rs @ [x] = as" by auto
  then have "as = rs @ [x]" by auto
  with vs2 vs_def have "bs = y # ts" by auto
  then show ?thesis by auto
qed

lemma is_sublist_at5: "distinct (as @ bs) ==> is_sublist [x,y] (as @ bs) ==>
  is_sublist [x,y] as ∨ is_sublist [x,y] bs ∨ x = last as ∧ y = hd bs"
  apply (case_tac "as = []") apply simp apply (cases "x = last as")
  apply (subgoal_tac "y = hd bs") apply simp
  apply (rule is_sublist_at4) apply assumption+  (*apply force+ *)
  apply (drule_tac is_sublist_at1) by auto

lemma is_sublist_rev: "is_sublist [a,b] (rev zs) = is_sublist [b,a] zs"
  apply (simp add: is_sublist_def)
    apply (intro iffI) apply (elim exE) apply (intro exI)
    apply (subgoal_tac "zs = (rev bs) @ b # a # rev as") apply assumption
    apply (subgoal_tac "rev (rev zs) = rev (as @ a # b # bs)")
      apply (thin_tac "rev zs = as @ a # b # bs") apply simp
      apply simp
    apply (elim exE) apply (intro exI) by force

lemma is_sublist_at5'[simp]:
 "distinct as ==> distinct bs ==> set as ∩ set bs = {} ==> is_sublist [x,y] (as @ bs) ==>
 is_sublist [x,y] as ∨ is_sublist [x,y] bs ∨ x = last as ∧ y = hd bs"
apply (subgoal_tac "distinct (as @ bs)") apply (drule is_sublist_at5) by auto

lemma splitAt_is_sublist1: "is_sublist (fst (splitAt ram vs)) vs" apply (cases "ram ∈ set vs")
apply (auto dest!: splitAt_ram splitAt_no_ram simp: is_sublist_def) apply (intro exI)
apply (subgoal_tac "vs = [] @ fst (splitAt ram vs) @ ram # snd (splitAt ram vs)") apply assumption by simp


lemma splitAt_is_sublist1R[simp]: "ram ∈ set vs ==> is_sublist (fst (splitAt ram vs) @ [ram]) vs"
apply (auto dest!: splitAt_ram simp: is_sublist_def) apply (intro exI)
apply (subgoal_tac "vs = [] @ fst (splitAt ram vs) @ ram # snd (splitAt ram vs)") apply assumption by simp

lemma splitAt_is_sublist2:"is_sublist (snd (splitAt ram vs)) vs" apply (cases "ram ∈ set vs")
apply (auto dest!: splitAt_ram splitAt_no_ram simp: is_sublist_def) apply (intro exI)
apply (subgoal_tac "vs = (fst (splitAt ram vs) @ [ram]) @ snd (splitAt ram vs) @ []") apply assumption by auto

lemma splitAt_is_sublist2R[simp]: "ram ∈ set vs ==> is_sublist (ram # snd (splitAt ram vs)) vs"
apply (auto dest!: splitAt_ram splitAt_no_ram simp: is_sublist_def) apply (intro exI)
apply (subgoal_tac "vs = fst (splitAt ram vs) @ ram # snd (splitAt ram vs) @ []") apply assumption by auto



(*********************** section is_nextElem *****************************)
subsection {* @{text "is_nextElem"} *}

constdefs is_nextElem :: "'a list => 'a => 'a => bool"
 "is_nextElem xs x y ≡ is_sublist [x,y] xs ∨ xs ≠ [] ∧ x = last xs ∧ y = hd xs"

lemma is_nextElem_a[intro]: "is_nextElem vs a b ==> a ∈ set vs"
  by (auto simp: is_nextElem_def is_sublist_def)
lemma is_nextElem_b[intro]: "is_nextElem vs a b ==> b ∈ set vs"
  by (auto simp: is_nextElem_def is_sublist_def)
lemma is_nextElem_sublist: "is_nextElem vs x y ==> x ≠ last vs  ==> is_sublist [x,y] vs"
  by (auto simp: is_nextElem_def)
lemma is_nextElem_last_hd[intro]: "distinct vs ==> is_nextElem vs x y ==>
  x = last vs ==> y = hd vs"
  by (auto simp: is_nextElem_def)
lemma is_nextElem_last_ne[intro]: "distinct vs ==> is_nextElem vs x y ==>
  x = last vs ==> vs ≠ []"
  by (auto simp: is_nextElem_def)
lemma is_nextElem_sublist2: "is_nextElem vs x y ==> y ≠ hd vs ==> is_sublist [x,y] vs"
  by (auto simp: is_nextElem_def)
lemma is_nextElem_sublistI: "is_sublist [x,y] vs ==> is_nextElem vs x y"
  by (auto simp: is_nextElem_def)
lemma is_nextElem_hd_lastI: "vs ≠ [] ==> y = hd vs ==> x = last vs ==> is_nextElem vs x y"
  by (auto simp: is_nextElem_def)

lemma is_nextElem_nth1: "is_nextElem ls x y ==> ∃ i j. i < length ls
  ∧ j < length ls ∧ ls!i = x ∧ ls!j = y ∧ (Suc i) mod (length ls) = j"
proof (cases "is_sublist [x,y] ls")
  assume is_nextElem: "is_nextElem ls x y"
  case True then show ?thesis apply (drule_tac is_sublist_nth1) by auto
next
  assume is_nextElem: "is_nextElem ls x y"
  case False with is_nextElem have hl: "ls ≠ [] ∧ last ls = x ∧ hd ls = y"
    by (auto simp: is_nextElem_def)
  then have j: "ls!0 = y" by (cases ls) auto
  from hl have i: "ls!(length ls - 1) = x" by (cases ls rule: rev_exhaust)  auto
  from i j hl have "(length ls - 1) < length ls ∧ 0 < length ls ∧ ls!(length ls - 1) = x
    ∧ ls!0 = y ∧ (Suc (length ls - 1)) mod (length ls) = 0" by auto
  then show ?thesis apply (intro exI) .
qed

lemma is_nextElem_nth2: " ∃ i j. i < length ls ∧ j < length ls ∧ ls!i = x ∧ ls!j = y
   ∧ (Suc i) mod (length ls) = j ==> is_nextElem ls x y"
proof -
  assume "∃ i j. i < length ls ∧ j < length ls ∧ ls!i = x ∧ ls!j = y ∧ (Suc i) mod (length ls) = j"
  then obtain i j where vors: "i < length ls ∧ j < length ls ∧ ls!i = x ∧ ls!j = y
    ∧ (Suc i) mod (length ls) = j" by auto
  then show ?thesis
  proof (cases "Suc i = length ls")
    case True with vors have "j = 0" by auto
      (*ls ! i = last ls*)
    with True vors show ?thesis apply (auto simp: is_nextElem_def)
     apply (cases ls rule: rev_exhaust) apply auto apply (cases ls) by auto
  next
    case False with vors have "is_sublist [x,y] ls"
    apply (rule_tac is_sublist_nth2) by auto
    then show ?thesis by (simp add: is_nextElem_def)
  qed
qed

lemma is_nextElem_rotate1:
  "is_nextElem (rotate m ls) x y ==> is_nextElem ls x y"
proof -
  assume is_nextElem: "is_nextElem (rotate m ls) x y"
  def n ≡ "m mod length ls"
  then have rot_eq: "rotate m ls = rotate n ls" by (auto intro: rotate_conv_mod)
  with is_nextElem have "is_nextElem (rotate n ls) x y" by auto
  then obtain i j where vors:"i < length (rotate n ls) ∧ j < length (rotate n ls) ∧
    (rotate n ls)!i = x ∧ (rotate n ls)!j = y ∧
    (Suc i) mod (length (rotate n ls)) = j" by (drule_tac is_nextElem_nth1) auto
  then have lls: "0 < length ls" by auto
  def k ≡ "(i+n) mod (length ls)"
  with lls have sk: "k < length ls" by auto
  from k_def lls vors have "ls!k = (rotate n ls)!(i mod (length ls))"  by (simp add: nth_rotate)
  with vors have lsk: "ls!k = x" by auto
  def l ≡ "(j+n) mod (length ls)"
  with lls have sl: "l < length ls" by auto
  from l_def lls vors have "ls!l = (rotate n ls)!(j mod (length ls))"  by (simp add: nth_rotate)
  with vors have lsl: "ls!l = y" by auto
  have mod_add1_eq': "!! a b c. (a mod c + b mod c) mod c = (a+b) mod (c::nat)"
    apply (rule sym)  by (rule mod_add1_eq)
  from vors k_def l_def
  have "(Suc i) mod length ls = j " by auto
  then have "(Suc i) mod length ls = j mod length ls" by auto
  then have "(Suc i) mod length ls + n mod (length ls) = j mod length ls + n mod (length ls)"
    by auto
  then have "((Suc i) mod length ls + n mod (length ls)) mod length ls
    = (j mod length ls + n mod (length ls)) mod length ls" by auto
  then have "((Suc i) + n) mod length ls = (j + n ) mod length ls" by (simp add: mod_add1_eq')
  then have "(1 + i + n) mod length ls = (j + n ) mod length ls" by simp
  then have "(1 mod length ls  + (i + n) mod length ls) mod length ls = (j + n ) mod length ls"
    by (simp add: mod_add1_eq')
  with lls have "(1 + (i + n) mod length ls) mod length ls = (j + n ) mod length ls"
    apply (cases "1 < length ls") apply force  apply (subgoal_tac "length ls = 1") apply simp by arith
  with vors k_def l_def have "(Suc k) mod (length ls) = l" by auto
  with sk lsk sl lsl show ?thesis by (auto intro: is_nextElem_nth2)
qed

lemma is_nextElem_rotate_eq[simp]: "is_nextElem (rotate m ls) x y = is_nextElem ls x y"
  apply (auto dest: is_nextElem_rotate1) apply (rule is_nextElem_rotate1)
  apply (subgoal_tac   "is_nextElem (rotate (length ls - m mod length ls) (rotate m ls)) x y")
  apply assumption by simp

lemma is_nextElem_congs_eq: "ls ≅ ms ==> is_nextElem ls x y = is_nextElem ms x y"
by (auto simp: congs_def)

lemma is_nextElem_rotate1: "distinct ls ==> is_nextElem ls x y ==> is_nextElem (rotate1 ls) x y"
proof (cases ls)
  case Nil
  assume "is_nextElem ls x y"
  with Nil show ?thesis by auto
next
  assume d: "distinct ls" and is_nextElem: "is_nextElem ls x y"
  case (Cons m ms)
  then have ls: "ls = m # ms" by auto
  have "ms ≠ [] ==> last ms ∈ set ms" by (induct ms) auto
  with is_nextElem d ls have rule1: "x = m ==> y = hd (ms @ [m])"
    apply (auto simp: is_nextElem_def is_sublist_def) apply (subgoal_tac "ms = y # bs") apply force
    apply (rule dist_at2) apply (rule d) apply (thin_tac " m # ms = as @ m # y # bs")
    apply (simp add: ls) apply force apply (simp add: Cons)
    by (simp split: split_if_asm)
  from is_nextElem d ls have rule2: "x ≠ m ∧  is_sublist [x, y] ms ==> is_nextElem (rotate1 ls) x y"
    apply (simp add: is_nextElem_def split: split_if_asm)
    apply auto apply (subgoal_tac "is_sublist [x,y] ([] @ ms @ [m])") apply force
    apply (rule is_sublist_add) by simp
  from is_nextElem d ls have rule3: "x ≠ m ∧ ¬ is_sublist [x,y] ms ==> is_nextElem (rotate1 ls) x y"
    apply (simp add: is_nextElem_def split: split_if_asm)
    apply auto apply (simp add: is_sublist_def) apply (intro exI)
    apply (subgoal_tac "ms @ [m] = butlast ms @ last ms # m # []") apply assumption
    by auto
  from Cons rule1 rule2 rule3 show ?thesis apply (cases "x ≠ m")
    apply auto by (simp add: is_nextElem_def is_sublist_def split: split_if_asm)
qed

lemma is_nextElem_congsI: "ls1 ≅ ls2 ==> distinct ls1 ==> is_nextElem ls1 x y ==> is_nextElem ls2 x y"
proof -
  assume eq: "ls1 ≅ ls2" and is_nextElem: "is_nextElem ls1 x y" and d: "distinct ls1"
  then obtain n where rot: "ls2 = rotate n ls1" by (unfold congs_def)  auto
  from is_nextElem d have "is_nextElem (rotate n ls1) x y" apply (induct n)
    by (auto intro: is_nextElem_rotate1)
  with rot show ?thesis by auto
qed

lemma is_nextElem_congseq: "ls1 ≅ ls2 ==> distinct ls1 ==> is_nextElem ls1 x y = is_nextElem ls2 x y"
proof
  assume "ls1 ≅ ls2" "distinct ls1" "is_nextElem ls1 x y"
  then show "is_nextElem ls2 x y" by (auto intro: is_nextElem_congsI)
next
  assume eqF: "ls1 ≅ ls2" and d: "distinct ls1" and is_nextElem: "is_nextElem ls2 x y"
  from eqF have eqF': "ls2 ≅ ls1" by (rule congs_sym)
  from eqF d have d': "distinct ls2" by (auto simp: congs_distinct)
  from eqF' d' is_nextElem  show "is_nextElem ls1 x y" by (auto intro: is_nextElem_congsI)
qed

lemma is_nextElem_rev[simp]: "is_nextElem (rev zs) a b = is_nextElem zs b a"
  apply (simp add: is_nextElem_def is_sublist_rev)
  apply (case_tac "zs = []") apply simp apply simp
  apply (case_tac "a = hd zs") apply (case_tac "zs")  apply simp  apply simp apply simp
  apply (case_tac "a = last (rev zs) ∧ b = last zs") apply simp
    apply (case_tac "zs" rule: rev_exhaust) apply simp
    apply (case_tac "ys") apply simp apply simp by force


lemma is_nextElem_circ:
  "[| distinct xs; is_nextElem xs a b; is_nextElem xs b a |] ==> |xs| ≤ 2"
apply(drule is_nextElem_nth1)
apply(drule is_nextElem_nth1)
apply (clarsimp)
apply(rename_tac i j)
apply(frule_tac i=j and j = "Suc i mod |xs|" in nth_eq_iff_index_eq)
  apply assumption+
apply(frule_tac j=i and i = "Suc j mod |xs|" in nth_eq_iff_index_eq)
  apply assumption+
apply(rule ccontr)
apply(simp add: distinct_conv_nth mod_Suc)
done


lemma cong_if_is_nextElem_eq:
 "[| distinct xs; distinct ys; set xs = set ys;
    !x y. is_nextElem xs x y = is_nextElem ys x y |] ==>
  xs ≅ ys"
apply(subgoal_tac "length xs = length ys")
 prefer 2 apply(simp add:distinct_card[symmetric])
apply(clarsimp simp:congs_def list_eq_iff_nth_eq)
apply(cases ys) apply simp
apply(rename_tac a as)
apply simp
apply(subgoal_tac "a ∈ set xs")
 prefer 2 apply blast
apply(drule in_set_conv_nth[THEN iffD1])
apply clarsimp
apply(rename_tac k)
apply(rule_tac x = k in exI)
apply(rule)
apply(rename_tac i)
apply(induct_tac i)
 using nth_rotate[of xs 0, symmetric]apply simp
apply clarsimp
apply(subgoal_tac "is_nextElem (rotate k xs) ((xs ! k # as) ! n) (as ! n)")
 apply(drule is_nextElem_nth1)
 apply (clarsimp simp: nth_eq_iff_index_eq)
apply(subgoal_tac "is_nextElem (xs) ((xs ! k # as) ! n) (as ! n)")
 apply simp
apply(subgoal_tac "is_nextElem (xs ! k # as) ((xs ! k # as) ! n) (as ! n)")
 apply simp
apply (rule is_nextElem_nth2)
apply(rule_tac x=n in exI)
apply(rule_tac x="Suc n" in exI)
apply simp
done


subsection{* @{text "nextElem, sublist, is_nextElem"} *}

lemma is_sublist_eq: "distinct vs ==> c ≠ y ==>
 (nextElem vs c x = y) = is_sublist [x,y] vs"
proof -
  assume d: "distinct vs" and c: "c ≠ y"
  have r1: "nextElem vs c x = y ==> is_sublist [x,y] vs"
  proof -
    assume fn: "nextElem vs c x = y"
    with c show ?thesis by(drule_tac nextElem_cases)(auto simp: is_sublist_def)
  qed
  with d have r2: "is_sublist [x,y] vs ==> nextElem vs c x = y"
  apply (simp add: is_sublist_def) apply (elim exE) by auto
  show ?thesis apply (intro iffI r1) by (auto intro: r2)
qed

lemma is_nextElem1: "distinct vs ==> x ∈ set vs ==> nextElem vs (hd vs) x = y ==> is_nextElem vs x y"
proof -
  assume d: "distinct vs" and x: "x ∈ set vs" and fn: "nextElem vs (hd vs) x = y"
  from x have r0: "vs ≠ []" by auto
  from d fn have r1: "x = last vs ==> y = hd vs" by (auto)
  from d fn have r3: "hd vs ≠ y ==> (∃ a b. vs = a @ [x,y] @ b)" by (drule_tac nextElem_cases) auto

  from x obtain n where xn:"x = vs!n" and nl: "n < length vs" by (auto simp: in_set_conv_nth)
  def as ≡ "take n vs"
  def bs ≡ "drop (Suc n) vs"
  from as_def bs_def xn nl have vs:"vs = as @ [x] @ bs" by (auto intro: id_take_nth_drop)
  then have r2: "x ≠ last vs ==> y ≠ hd vs"
  proof -
    assume notx: "x ≠ last vs"
    from vs notx have "bs ≠ []" by auto
    with vs have r2: "vs = as @ [x, hd bs] @ tl bs" by auto
    with d have ineq: "hd bs ≠ hd vs" by (cases as) auto
    from d fn r2 have "y = hd bs" by auto
    with ineq show ?thesis by auto
  qed
  from r0 r1 r2 r3 show ?thesis apply (simp add:is_nextElem_def is_sublist_def)
   apply (cases "x = last vs") by auto
qed

lemma is_nextElem2: "distinct vs ==> x ∈ set vs ==> is_nextElem vs x y ==> nextElem vs (hd vs) x = y"
proof -
  assume d: "distinct vs" and x: "x ∈ set vs" and is_nextElem: "is_nextElem vs x y"
  then show ?thesis apply (simp add: is_nextElem_def) apply (cases "is_sublist [x,y] vs")
    apply (cases "y = hd vs")
    apply (simp add: is_sublist_def) apply (force dest: distinct_hd_not_cons)
    apply (subgoal_tac "hd vs ≠ y")  apply (simp add: is_sublist_eq) by auto
qed

lemma nextElem_is_nextElem:
 "distinct xs ==> x ∈ set xs ==>
   is_nextElem xs x y = (nextElem xs (hd xs) x = y)"
  by (auto intro!: is_nextElem1 is_nextElem2)

lemma nextElem_congs_eq: "xs ≅ ys ==> distinct xs ==> x ∈ set xs  ==>
   nextElem xs (hd xs) x = nextElem ys (hd ys) x"
proof -
    assume eq: "xs ≅ ys" and dist: "distinct xs" and x: "x ∈ set xs"
    def y ≡ "nextElem xs (hd xs) x"
    then have f1:"nextElem xs (hd xs) x = y" by auto
    with dist x have "is_nextElem xs x y" by (auto intro: is_nextElem1)
    with eq have "is_nextElem ys x y" by (simp add:is_nextElem_congs_eq)
    with eq dist x have f2:"nextElem ys (hd ys) x = y"
      by (auto simp: congs_distinct intro: is_nextElem2)
    from f1 f2 show ?thesis by auto
qed

lemma nextElem_iso_eq:
     "as ≅ as' ==> distinct as ==> x ∈ set as ==>
     nextElem as (hd as) x = nextElem as' (hd as') x"
 by (simp add: nextElem_congs_eq congs_def)


lemma is_sublist_is_nextElem: "distinct vs ==> is_nextElem vs x y ==> is_sublist as vs ==> x ∈ set as ==> x ≠ last as ==> is_sublist [x,y] as"
proof -
  assume d: "distinct vs" and is_nextElem: "is_nextElem vs x y" and subl: "is_sublist as vs" and xin: "x ∈ set as" and xnl: "x ≠ last as"
  from xin have asne: "as ≠ []" by auto
  with subl have vsne: "vs ≠ []" by (auto simp: is_sublist_def)
  from subl obtain rs ts where vs: "vs = rs @ as @ ts"  apply (simp add: is_sublist_def) apply (elim exE) by auto
  with d xnl asne have "x ≠ last vs"
  proof (cases "ts = []")
    case True with d xnl asne vs show ?thesis by force
  next
    def lastvs ≡ "last ts"
    case False
    with vs lastvs_def have vs2: "vs = rs @ as @ butlast ts @ [lastvs]" by auto
    with d have "lastvs ∉ set as" by auto
    with xin have "lastvs ≠ x" by auto
    with vs2 show ?thesis by auto
  qed
  with is_nextElem have subl_vs: "is_sublist [x,y] vs" by (auto simp: is_nextElem_def)
  from d xin vs have "¬ is_sublist [x] rs" by auto
  then have nrs: "¬ is_sublist [x,y] rs" by (auto dest: is_sublist_hd)
  from d xin vs have "¬ is_sublist [x] ts" by auto
  then have nts: "¬ is_sublist [x,y] ts" by (auto dest: is_sublist_hd)
  from d xin vs have xnrs: "x ∉ set rs" by auto
  then have notrs: "¬ is_sublist [x,y] rs" by (auto simp:is_sublist_in)
  from xnrs have xnlrs: "rs ≠ [] ==> x ≠ last rs" by (induct rs) auto
  from d xin vs have xnts: "x ∉ set ts" by auto
  then have notts: "¬ is_sublist [x,y] ts"  by (auto simp:is_sublist_in)
  from d vs subl_vs have "is_sublist [x,y] rs ∨ is_sublist [x,y] (as@ts)" apply (cases "rs = []") apply simp apply (rule_tac is_sublist_at1) by (auto intro!: xnlrs)
  with notrs have "is_sublist [x,y] (as@ts)" by auto
  with d vs xnl have "is_sublist [x,y] as ∨ is_sublist [x,y] ts" apply (rule_tac is_sublist_at1) by auto
  with notts show "is_sublist [x,y] as"  by auto
qed


subsection {* @{text before} *}

constdefs before :: "'a list => 'a => 'a => bool"
"before vs ram1 ram2 ≡ ∃ a b c. vs = a @ ram1 # b @ ram2 # c"

lemma before_dist_fst_fst[simp]: "before vs ram1 ram2 ==> distinct vs ==> fst (splitAt ram2 (fst (splitAt ram1 vs))) = fst (splitAt ram1 (fst (splitAt ram2 vs)))"
  apply (simp add: before_def) apply (elim exE)
  apply (drule splitAt_dist_ram_all) by (auto dest!: pairD)

lemma before_dist_fst_snd[simp]: "before vs ram1 ram2 ==> distinct vs ==> fst (splitAt ram2 (snd (splitAt ram1 vs))) = snd (splitAt ram1 (fst (splitAt ram2 vs)))"
  apply (simp add: before_def) apply (elim exE)
  apply (drule_tac splitAt_dist_ram_all) by (auto dest!: pairD)

lemma before_dist_snd_fst[simp]: "before vs ram1 ram2 ==> distinct vs ==> snd (splitAt ram2 (fst (splitAt ram1 vs))) = snd (splitAt ram1 (snd (splitAt ram2 vs)))"
  apply (simp add: before_def) apply (elim exE)
  apply (drule_tac splitAt_dist_ram_all) by (auto dest!: pairD)

lemma before_dist_snd_snd[simp]: "before vs ram1 ram2 ==> distinct vs ==> snd (splitAt ram2 (snd (splitAt ram1 vs))) = fst (splitAt ram1 (snd (splitAt ram2 vs)))"
  apply (simp add: before_def) apply (elim exE)
  apply (drule_tac splitAt_dist_ram_all) by (auto dest!: pairD)

lemma before_dist_snd[simp]: "before vs ram1 ram2 ==> distinct vs ==> fst (splitAt ram1 (snd (splitAt ram2 vs))) = snd (splitAt ram2 vs)"
  apply (simp add: before_def) apply (elim exE)
  apply (drule_tac splitAt_dist_ram_all)   by (auto dest!: pairD)

lemma before_dist_fst[simp]: "before vs ram1 ram2 ==> distinct vs ==> fst (splitAt ram1 (fst (splitAt ram2 vs))) = fst (splitAt ram1 vs)"
  apply (simp add: before_def) apply (elim exE)
  apply (drule_tac splitAt_dist_ram_all)   by (auto dest!: pairD)

lemma before_or: "ram1 ∈ set vs ==> ram2 ∈ set vs ==> ram1 ≠ ram2 ==> before vs ram1 ram2 ∨ before vs ram2 ram1"
proof -
  assume r1: "ram1 ∈ set vs" and r2: "ram2 ∈ set vs" and r12: "ram1 ≠ ram2"
  then show ?thesis
    proof (cases "ram2 ∈ set (snd (splitAt ram1 vs))")
      def a ≡ "fst (splitAt ram1 vs)"
      def b ≡ "fst (splitAt ram2 (snd (splitAt ram1 vs)))"
      def c ≡ "snd (splitAt ram2 (snd (splitAt ram1 vs)))"
      case True with r1 a_def b_def c_def have "vs = a @ [ram1] @ b @ [ram2] @ c"
        by (auto dest!: splitAt_ram)
      then show ?thesis apply (simp add: before_def) by auto
    next
      def ab ≡ "fst (splitAt ram1 vs)"
      case False with r1 r2 r12 ab_def have r2': "ram2 ∈ set ab" by (auto intro: splitAt_ram3)
      def a ≡ "fst (splitAt ram2 ab)"
      def b ≡ "snd (splitAt ram2 ab)"
      def c ≡ "snd (splitAt ram1 vs)"
      from r1 ab_def c_def have "vs = ab @ [ram1] @ c" by (auto dest!: splitAt_ram)
      with r2' a_def b_def have "vs = (a @ [ram2] @ b) @ [ram1] @ c" by (drule_tac splitAt_ram) simp
      then show ?thesis apply (simp add: before_def) apply (rule disjI2) by auto
    qed
  qed

lemma before_r1:
  "before vs r1 r2 ==> r1 ∈ set vs" by (auto simp: before_def)

lemma before_r2:
  "before vs r1 r2 ==> r2 ∈ set vs" by (auto simp: before_def)

lemma before_dist_r1r2:
  "distinct vs ==> before vs r1 r2 ==> r1 ≠ r2"
  by (auto simp: before_def)

lemma before_dist_r2:
  "distinct vs ==> before vs r1 r2 ==> r2 ∈ set (snd (splitAt r1 vs))"
proof -
  assume d: "distinct vs" and b: "before vs r1 r2"
  from d b have ex1: "∃! s. (vs = (fst s) @ r1 # snd (s))" apply (drule_tac before_r1) apply (rule distinct_unique1)  by auto
  from d b ex1 show ?thesis apply (unfold before_def)
    proof (elim exE ex1E)
      fix a b c s
      assume vs: "vs = a @ r1 # b @ r2 # c" and "∀y. vs = fst y @ r1 # snd y --> y = s"
      then have  "!! y. vs = fst y @ r1 # snd y --> y = s" by auto
      then have single: "!! y. vs = fst y @ r1 # snd y ==> y = s" by auto
      def bc ≡ "b @ r2 # c"
      with vs have vs2: "vs = a @ r1 # bc" by auto
      from bc_def have  r2: "r2 ∈ set bc" by auto
      def t ≡ "(a,bc)"
      with vs2 have vs3: "vs = fst (t) @ r1 # snd (t)" by auto
      with single have ts: "t = s" by (rule_tac single) auto
      from b have "splitAt r1 vs = s" apply (drule_tac before_r1) apply (drule_tac splitAt_ram) by (rule single) auto
      with ts have "t = splitAt r1 vs" by simp
      with t_def have "bc = snd(splitAt r1 vs)" by simp
      with r2 show ?thesis by simp
    qed
  qed

lemma before_dist_not_r2[intro]:
  "distinct vs ==> before vs r1 r2 ==> r2 ∉  set (fst (splitAt r1 vs))" apply (frule before_dist_r2) by (auto dest: splitAt_distinct_fst_snd)

lemma before_dist_r1:
  "distinct vs ==> before vs r1 r2 ==> r1 ∈ set (fst (splitAt r2 vs))"
proof -
  assume d: "distinct vs" and b: "before vs r1 r2"
  from d b have ex1: "∃! s. (vs = (fst s) @ r2 # snd (s))" apply (drule_tac before_r2) apply (rule distinct_unique1)  by auto
  from d b ex1 show ?thesis apply (unfold before_def)
    proof (elim exE ex1E)
      fix a b c s
      assume vs: "vs = a @ r1 # b @ r2 # c" and "∀y. vs = fst y @ r2 # snd y --> y = s"
      then have  "!! y. vs = fst y @ r2 # snd y --> y = s" by auto
      then have single: "!! y. vs = fst y @ r2 # snd y ==> y = s" by auto
      def ab ≡ "a @ r1 # b"
      with vs have vs2: "vs = ab @ r2 # c" by auto
      from ab_def have  r1: "r1 ∈ set ab" by auto
      def t ≡ "(ab,c)"
      with vs2 have vs3: "vs = fst (t) @ r2 # snd (t)" by auto
      with single have ts: "t = s" by (rule_tac single) auto
      from b have "splitAt r2 vs = s" apply (drule_tac before_r2) apply (drule_tac splitAt_ram) by (rule single) auto
      with ts have "t = splitAt r2 vs" by simp
      with t_def have "ab = fst(splitAt r2 vs)" by simp
      with r1 show ?thesis by simp
    qed
  qed

lemma before_dist_not_r1[intro]:
  "distinct vs ==> before vs r1 r2 ==> r1 ∉  set (snd (splitAt r2 vs))" apply (frule before_dist_r1) by (auto dest: splitAt_distinct_fst_snd)

lemma before_snd:
  "r2 ∈ set (snd (splitAt r1 vs)) ==> before vs r1 r2"
proof -
  assume r2: "r2 ∈ set (snd (splitAt r1 vs))"
  from r2 have r1: "r1 ∈ set vs" apply (rule_tac ccontr) apply (drule splitAt_no_ram) by simp
  def a ≡ "fst (splitAt r1 vs)"
  def bc ≡ "snd (splitAt r1 vs)"
  def b ≡ "fst (splitAt r2 bc)"
  def c ≡ "snd (splitAt r2 bc)"
  from r1 a_def bc_def have vs: "vs = a @ [r1] @ bc" by (auto dest: splitAt_ram)
  from r2 bc_def have r2: "r2 ∈ set bc" by simp
  with b_def c_def have "bc = b @ [r2] @ c" by (auto dest: splitAt_ram)
  with vs show ?thesis by (simp add: before_def) auto
qed

lemma before_fst:
"r2 ∈ set vs ==> r1 ∈ set (fst (splitAt r2 vs)) ==> before vs r1 r2"
proof -
  assume r2: "r2 ∈ set vs" and r1: "r1 ∈ set (fst (splitAt r2 vs))"
  def ab ≡ "fst (splitAt r2 vs)"
  def c ≡ "snd (splitAt r2 vs)"
  def a ≡ "fst (splitAt r1 ab)"
  def b ≡ "snd (splitAt r1 ab)"
  from r2 ab_def c_def have vs: "vs = ab @ [r2] @ c" by (auto dest: splitAt_ram)
  from r1 ab_def have r1: "r1 ∈ set ab" by simp
  with a_def b_def have "ab = a @ [r1] @ b" by (auto dest: splitAt_ram)
  with vs show ?thesis by (simp add: before_def) auto
qed

(* usefule simplifier rules *)
lemma before_dist_eq_fst:
"distinct vs ==> r2 ∈ set vs ==> r1 ∈ set (fst (splitAt r2 vs)) = before vs r1 r2"
  by (auto intro: before_fst before_dist_r1)

lemma before_dist_eq_snd:
"distinct vs ==> r2 ∈ set (snd (splitAt r1 vs)) = before vs r1 r2"
  by (auto intro: before_snd before_dist_r2)

lemma pair_snd: "(a,b) = p ==> snd p = b" by auto

lemma before_dist_eq_snd':
 "distinct vs ==> (as, bs) = (splitAt ram1 vs) ==>
    ram2 ∈ set bs = before vs ram1 ram2"
 by (simp add: before_dist_eq_snd[symmetric] pair_snd)

lemma before_dist_not1:
  "distinct vs ==> before vs ram1 ram2 ==> ¬ before vs ram2 ram1"
proof
   assume d: "distinct vs" and b1: "before vs ram2 ram1" and b2: "before vs ram1 ram2"
   from b2 have r1: "ram1 ∈ set vs" by (drule_tac before_r1)
   from d b1 have r2: "ram2 ∈ set (fst (splitAt ram1 vs))" by (rule before_dist_r1)
   from d b2 have r2':"ram2 ∈ set (snd (splitAt ram1 vs))" by (rule before_dist_r2)
   from d r1 r2 r2' show "False" by (drule_tac splitAt_distinct_fst_snd) auto
qed

lemma before_dist_not2:
  "distinct vs ==> ram1 ∈ set vs ==> ram2 ∈ set vs ==> ram1 ≠ ram2 ==> ¬ (before vs ram1 ram2) ==> before vs ram2 ram1"
proof -
  assume "distinct vs" "ram1 ∈ set vs " "ram2 ∈ set vs" "ram1 ≠ ram2" "¬ before vs ram1 ram2"
  then show "before vs ram2 ram1" apply (frule_tac before_or) by auto
qed

lemma before_dist_eq:
  "distinct vs ==> ram1 ∈ set vs ==> ram2 ∈ set vs ==> ram1 ≠ ram2 ==> ( ¬ (before vs ram1 ram2)) = before vs ram2 ram1"
  by (auto intro: before_dist_not2 dest: before_dist_not1)

lemma before_vs:
 "distinct vs ==> before vs ram1 ram2 ==> vs = fst (splitAt ram1 vs) @ ram1 # fst (splitAt ram2 (snd (splitAt ram1 vs))) @ ram2 # snd (splitAt ram2 vs)"
proof -
  assume d: "distinct vs" and b: "before vs ram1 ram2"
  def s ≡ "snd (splitAt ram1 vs)"
  from b have  "ram1 ∈ set vs" by (auto simp: before_def)
  with s_def have vs: "vs = fst (splitAt ram1 vs) @ [ram1] @ s" by (auto dest: splitAt_ram)
  from d b s_def have "ram2 ∈ set s" by (auto intro: before_dist_r2)
  then have snd: "s = fst (splitAt ram2 s) @ [ram2] @  snd (splitAt ram2 s)"
    by (auto dest: splitAt_ram)
  with vs have "vs = fst (splitAt ram1 vs) @ [ram1] @ fst (splitAt ram2 s) @ [ram2] @  snd (splitAt ram2 s)" by auto
  with d b s_def show ?thesis by auto
qed




(************************ between lemmas *************************************)
subsection {* @{const between} *}

constdefs pre_between :: "'a list => 'a => 'a => bool"
"pre_between vs ram1 ram2 ≡
   distinct vs ∧ ram1 ∈ set vs ∧ ram2 ∈ set vs ∧ ram1 ≠ ram2"

declare pre_between_def [simp]

lemma pre_between_dist[intro]:
  "pre_between vs ram1 ram2 ==> distinct vs" by (auto simp: pre_between_def)

lemma pre_between_r1[intro]:
  "pre_between vs ram1 ram2 ==> ram1 ∈ set vs" by auto

lemma pre_between_r2[intro]:
  "pre_between vs ram1 ram2 ==> ram2 ∈ set vs" by auto

lemma pre_between_r12[intro]:
  "pre_between vs ram1 ram2 ==> ram1 ≠ ram2" by auto

lemma pre_between_sym:
  "pre_between vs ram1 ram2 = pre_between vs ram2 ram1" by (auto simp: pre_between_def)

lemma pre_between_symI:
  "pre_between vs ram1 ram2 ==> pre_between vs ram2 ram1" by auto

lemma pre_between_before[dest]:
  "pre_between vs ram1 ram2 ==> before vs ram1 ram2 ∨ before vs ram2 ram1" by (rule_tac before_or) auto

lemma pre_between_rotate1[intro]:
  "pre_between vs ram1 ram2 ==> pre_between (rotate1 vs) ram1 ram2" by auto

lemma pre_between_rotate[intro]:
  "pre_between vs ram1 ram2 ==> pre_between (rotate n vs) ram1 ram2" by auto

lemma(*<*) before_xor: (*>*)
 "pre_between vs ram1 ram2 ==> (¬ before vs ram1 ram2) = before vs ram2 ram1"
  by (simp add: before_dist_eq)

declare pre_between_def [simp del]

lemma between_simp1[simp]:
"before vs ram1 ram2 ==> pre_between vs ram1 ram2 ==>
between vs ram1 ram2 = fst (splitAt ram2 (snd (splitAt ram1 vs)))"
by (simp add: pre_between_def between_def split_def before_dist_eq_snd)


lemma between_simp2[simp]:
"before vs ram1 ram2 ==> pre_between vs ram1 ram2 ==>
  between vs ram2 ram1 = snd (splitAt ram2 vs) @  fst (splitAt ram1 vs)"
proof -
  assume b: "before vs ram1 ram2" and p: "pre_between vs ram1 ram2"
  from p b have b2: "¬ before vs ram2 ram1" apply (simp add: pre_between_def) by (auto dest: before_dist_not1)
  with p have "ram2 ∉ set (fst (splitAt ram1 vs))" by (simp add: pre_between_def before_dist_eq_fst)
  then have "fst (splitAt ram1 vs) = fst (splitAt ram2 (fst (splitAt ram1 vs)))" by (auto dest: splitAt_no_ram)
  then have "fst (splitAt ram2 (fst (splitAt ram1 vs))) = fst (splitAt ram1 vs)" by auto
  with b2 b p show ?thesis apply (simp add: pre_between_def between_def split_def)
    by (auto dest: before_dist_not_r1)
qed

lemma between_not_r1[intro]:
  "distinct vs ==> ram1 ∉ set (between vs ram1 ram2)"
proof (cases "pre_between vs ram1 ram2")
  assume d: "distinct vs"
  case True then have p: "pre_between vs ram1 ram2" by auto
  then show "ram1 ∉ set (between vs ram1 ram2)"
  proof (cases "before vs ram1 ram2")
    case True with d p show ?thesis by (auto del: notI)
  next
    from p have p2: "pre_between vs ram2 ram1" by (auto intro: pre_between_symI)
    case False with p have "before vs ram2 ram1" by auto
    with d p2 show ?thesis  by (auto del: notI)
  qed
next
  assume d:"distinct vs"
  case False then have p: "¬ pre_between vs ram1 ram2" by auto
  then show ?thesis
  proof (cases "ram1 = ram2")
    case True with d have h1:"ram2 ∉ set (snd (splitAt ram2 vs))" by (auto del: notI)
    from True d have h2: "ram2 ∉ set (fst (splitAt ram2 (fst (splitAt ram2 vs))))" by (auto del: notI)
    with True d h1 show ?thesis by (auto simp: between_def split_def)
  next
    case False then have neq: "ram1 ≠ ram2" by auto
    then show ?thesis
    proof (cases "ram1 ∉ set vs")
      case True with d show ?thesis by (auto dest: splitAt_no_ram splitAt_in_fst simp: between_def split_def)
    next
      case False then have r1in: "ram1 ∈ set vs" by auto
      then show ?thesis
      proof (cases "ram2 ∉ set vs")
        from d have h1: "ram1 ∉ set (fst (splitAt ram1 vs))" by (auto del: notI)
        case True with d h1 show ?thesis
        by (auto dest: splitAt_not1 splitAt_in_fst splitAt_ram
        splitAt_no_ram simp: between_def split_def del: notI)
      next
        case False then have r2in: "ram2 ∈ set vs" by auto
        with d neq r1in have "pre_between vs ram1 ram2"
          by (auto simp: pre_between_def)
        with p show ?thesis by auto
      qed
    qed
  qed
qed

lemma between_not_r2[intro]:
  "distinct vs ==> ram2 ∉ set (between vs ram1 ram2)"
proof (cases "pre_between vs ram1 ram2")
  assume d: "distinct vs"
  case True then have p: "pre_between vs ram1 ram2" by auto
  then show "ram2 ∉ set (between vs ram1 ram2)"
  proof (cases "before vs ram1 ram2")
    from d have "ram2 ∉ set (fst (splitAt ram2 vs))" by (auto del: notI)
    then have h1: "ram2 ∉ set (snd (splitAt ram1 (fst (splitAt ram2 vs))))"
      by (auto dest: splitAt_in_fst)
    case True with d p h1 show ?thesis by (auto del: notI)
  next
    from p have p2: "pre_between vs ram2 ram1" by (auto intro: pre_between_symI)
    case False with p have "before vs ram2 ram1" by auto
    with d p2 show ?thesis  by (auto del: notI)
  qed
next
  assume d:"distinct vs"
  case False then have p: "¬ pre_between vs ram1 ram2" by auto
  then show ?thesis
  proof (cases "ram1 = ram2")
    case True with d have h1:"ram2 ∉ set (snd (splitAt ram2 vs))" by (auto del: notI)
    from True d have h2: "ram2 ∉ set (fst (splitAt ram2 (fst (splitAt ram2 vs))))" by (auto del: notI)
    with True d h1 show ?thesis by (auto simp: between_def split_def)
  next
    case False then have neq: "ram1 ≠ ram2" by auto
    then show ?thesis
    proof (cases "ram2 ∉ set vs")
      case True with d show ?thesis
        by (auto dest: splitAt_no_ram splitAt_in_fst
         splitAt_in_fst simp: between_def split_def)
    next
      case False then have r1in: "ram2 ∈ set vs" by auto
      then show ?thesis
      proof (cases "ram1 ∉ set vs")
        from d have h1: "ram1 ∉ set (fst (splitAt ram1 vs))" by (auto del: notI)
        case True with d h1 show ?thesis by  (auto dest: splitAt_ram splitAt_no_ram simp: between_def split_def del: notI)
      next
        case False then have r2in: "ram1 ∈ set vs" by auto
        with d neq r1in have "pre_between vs ram1 ram2" by (auto simp: pre_between_def)
        with p show ?thesis by auto
      qed
    qed
  qed
qed

lemma between_distinct[intro]:
  "distinct vs ==> distinct (between vs ram1 ram2)"
proof -
  assume vs: "distinct vs"
  def a: a ≡ "fst (splitAt ram1 vs)"
  def b: b ≡ "snd (splitAt ram1 vs)"
  from a b have ab: "(a,b) = splitAt ram1 vs" by auto
  with vs have ab_disj:"set a ∩ set b = {}" by (drule_tac splitAt_distinct_ab)  auto
  def c: c ≡ "fst (splitAt ram2 a)"
  def d: d ≡ "snd (splitAt ram2 a)"
  from c d have c_d: "(c,d) = splitAt ram2 a" by auto
  with ab_disj have "set c ∩ set b = {}" by (drule_tac splitAt_subset_ab) auto
  with vs a b c show ?thesis
    by (auto simp: between_def split_def splitAt_no_ram dest: splitAt_ram intro: splitAt_distinct_fst splitAt_distinct_snd)
qed

lemma between_distinct_r12:
  "distinct vs ==> ram1 ≠ ram2 ==> distinct (ram1 # between vs ram1 ram2 @ [ram2])" by (auto del: notI)

lemma between_vs:
  "before vs ram1 ram2 ==> pre_between vs ram1 ram2 ==>
  vs = fst (splitAt ram1 vs) @ ram1 # (between vs ram1 ram2) @ ram2 # snd (splitAt ram2 vs)"
  apply (simp) apply (frule pre_between_dist) apply (drule before_vs) by auto

lemma between_in:
  "before vs ram1 ram2 ==> pre_between vs ram1 ram2 ==> x ∈ set vs ==> x = ram1 ∨ x ∈ set (between vs ram1 ram2) ∨ x = ram2 ∨ x ∈ set (between vs ram2 ram1)"
proof -
  assume b: "before vs ram1 ram2" and p: "pre_between vs ram1 ram2" and xin: "x ∈ set vs"
  def a ≡ "fst (splitAt ram1 vs)"
  def b ≡ "between vs ram1 ram2"
  def c ≡ "snd (splitAt ram2 vs)"
  from p have "distinct vs" by auto
  from p b a_def b_def c_def have "vs = a @ ram1 # b @ ram2 # c" apply (drule_tac between_vs)  by auto
  with xin have "x ∈ set (a @ ram1 # b @ ram2 # c)" by auto
  then have "x ∈ set (a) ∨ x ∈ set (ram1 #b) ∨ x ∈ set (ram2 # c)" by auto
  then have "x ∈ set (a) ∨ x = ram1 ∨ x ∈ set b ∨ x = ram2 ∨ x ∈ set c" by auto
  then have "x ∈ set c ∨ x ∈ set (a) ∨ x = ram1 ∨ x ∈ set b ∨ x = ram2" by auto
  then have "x ∈ set (c @ a) ∨ x = ram1 ∨ x ∈ set b ∨ x = ram2" by auto
  with b p a_def b_def c_def show ?thesis by auto
qed

lemma
  "before vs ram1 ram2 ==> pre_between vs ram1 ram2 ==>
  hd vs ≠ ram1 ==> (a,b) = splitAt (hd vs) (between vs ram2 ram1) ==>
  vs = [hd vs] @ b @ [ram1] @ (between vs ram1 ram2) @ [ram2] @ a"
proof -
  assume b: "before vs ram1 ram2" and p: "pre_between vs ram1 ram2" and vs: "hd vs ≠ ram1" and ab: "(a,b) = splitAt (hd vs) (between vs ram2 ram1)"
  from p have dist_b: "distinct (between vs ram2 ram1)" by (auto intro: between_distinct simp: pre_between_def)
  with ab have "distinct a ∧ distinct b" by (auto intro: splitAt_distinct_a splitAt_distinct_b)
  def r ≡ "snd (splitAt ram1 vs)"
  def btw ≡ "between vs ram2 ram1"
  from p r_def have vs2: "vs = fst (splitAt ram1 vs) @ [ram1] @ r" by (auto dest: splitAt_ram simp: pre_between_def)
  then have "fst (splitAt ram1 vs) = [] ==> hd vs = ram1" by auto
  with vs have neq: "fst (splitAt ram1 vs) ≠ []" by auto
  with vs2 have vs_fst: "hd vs = hd (fst (splitAt ram1 vs))" by (induct "fst (splitAt ram1 vs)") auto
  with neq have "hd vs ∈ set (fst (splitAt ram1 vs))"  by (induct "fst (splitAt ram1 vs)") auto
  with b p have "hd vs ∈ set (between vs ram2 ram1)" by auto
  with btw_def have help1: "btw =  fst (splitAt (hd vs) btw) @ [hd vs] @ snd (splitAt (hd vs) btw)" by (auto dest: splitAt_ram)
  from p b btw_def have "btw = snd (splitAt ram2 vs) @  fst (splitAt ram1 vs)" by auto
  with neq have "btw = snd (splitAt ram2 vs) @ hd (fst (splitAt ram1 vs)) # tl (fst (splitAt ram1 vs))" by auto
  with vs_fst have "btw = snd (splitAt ram2 vs) @ [hd vs] @ tl (fst (splitAt ram1 vs))" by auto
  with help1 have eq: "snd (splitAt ram2 vs) @ [hd vs] @ tl (fst (splitAt ram1 vs)) = fst (splitAt (hd vs) btw) @ [hd vs] @ snd (splitAt (hd vs) btw)" by auto
  from dist_b btw_def help1 have "distinct (fst (splitAt (hd vs) btw) @ [hd vs] @ snd (splitAt (hd vs) btw))" by auto
  with eq have  eq2: "snd (splitAt ram2 vs) = fst (splitAt (hd vs) btw) ∧ tl (fst (splitAt ram1 vs)) = snd (splitAt (hd vs) btw)" apply (rule_tac dist_at) by auto
  with btw_def ab have a: "a = snd (splitAt ram2 vs)" by (auto dest: pairD)
  from eq2 vs_fst have "hd (fst (splitAt ram1 vs)) # tl (fst (splitAt ram1 vs)) = hd vs # snd (splitAt (hd vs) btw)" by auto
  with ab btw_def neq have hdb: "hd vs # b = fst (splitAt ram1 vs)"  by (auto dest: pairD)

  from b p have "vs = fst (splitAt ram1 vs) @ [ram1] @ fst (splitAt ram2 (snd (splitAt ram1 vs))) @ [ram2] @ snd (splitAt ram2 vs)" apply simp
    apply (rule_tac before_vs) by (auto simp: pre_between_def)
  with hdb have "vs = (hd vs # b) @ [ram1] @ fst (splitAt ram2 (snd (splitAt ram1 vs))) @ [ram2] @ snd (splitAt ram2 vs)" by auto
  with a b p show ?thesis by (simp)
qed

lemma between1: "ram1 ∈ set vs ==> ram2 ∈ set vs ==>
  ram2 ∈ set (snd (splitAt ram1 vs)) ==>
  vs = fst (splitAt ram1 vs)  @ [ram1] @ (between vs ram1 ram2)
       @ [ram2] @ snd (splitAt ram2 (snd(splitAt ram1 vs)))"
  apply (simp add: between_def splitAt_ram split_def) by (auto dest!: splitAt_ram)

lemma between2: "ram1 ∈ set vs ==> ram2 ∈ set vs ==> ram1 ≠ ram2 ==>
  ram2 ∉ set (snd (splitAt ram1 vs)) ==>
  vs @ vs = fst (splitAt ram1 vs)  @ [ram1] @ (between vs ram1 ram2)
            @ [ram2] @ snd (splitAt ram2 (fst(splitAt ram1 vs))) @ [ram1]
            @ snd (splitAt ram1 vs)"
proof -
  assume r1: "ram1 ∈ set vs" and r2: "ram2 ∈ set vs" and r12: "ram1 ≠ ram2" and rnot2: "ram2 ∉ set (snd (splitAt ram1 vs))"
  then have r2in: "ram2 ∈ set (fst (splitAt ram1 vs))"
   by (auto dest!: splitAt_ram2)
  then have xx: "fst (splitAt ram2 (fst (splitAt ram1 vs))) @ ram2 # snd (splitAt ram2 (fst (splitAt ram1 vs))) = fst (splitAt ram1 vs)" by (auto dest!: splitAt_ram)
  from r1 have "vs = fst (splitAt ram1 vs) @ ram1 # snd (splitAt ram1 vs)" by (auto dest!: splitAt_ram)
  with r2in have "vs = (fst (splitAt ram2 (fst(splitAt ram1 vs))) @ ram2 # (snd (splitAt ram2 (fst (splitAt ram1 vs))))) @ ram1 # snd (splitAt ram1 vs)" by (simp add: xx)
  with r1 rnot2 show ?thesis
  by (simp add: between_def splitAt_ram split_def)
qed


lemma between_congs: "pre_between vs ram1 ram2 ==> vs ≅ vs' ==> between vs ram1 ram2 = between vs' ram1 ram2"
proof -
  have "!! us. pre_between us ram1 ram2 ==> before us ram1 ram2 ==> between us ram1 ram2 = between (rotate1 us) ram1 ram2"
  proof -
    fix us
    assume vors: "pre_between us ram1 ram2"  "before us ram1 ram2"
    then have pb2: "pre_between (rotate1 us) ram1 ram2" by auto
    with vors show "between us ram1 ram2 = between (rotate1 us) ram1 ram2"
    proof (cases "us")
      case Nil then show ?thesis by auto
    next
      case (Cons u' us')
      with vors pb2 show ?thesis apply (auto simp: before_def)
        apply (case_tac "a") apply auto
        by (simp_all add: between_def split_def pre_between_def)
    qed
  qed

  moreover have "!! us. pre_between us ram1 ram2 ==> before us ram2 ram1 ==> between us ram1 ram2 = between (rotate1 us) ram1 ram2"
  proof -
    fix us
    assume vors: " pre_between us ram1 ram2"  "before us ram2 ram1"
    then have pb2: "pre_between (rotate1 us) ram1 ram2" by auto
    with vors show "between us ram1 ram2 = between (rotate1 us) ram1 ram2"
    proof (cases "us")
      case Nil then show ?thesis by auto
    next
      case (Cons u' us')
      with vors pb2 show ?thesis apply (auto simp: before_def)
        apply (case_tac "a") apply auto
        by (simp_all add: between_def split_def pre_between_def)
    qed
  qed

  ultimately have help: "!! us. pre_between us ram1 ram2 ==> between us ram1 ram2 = between (rotate1 us) ram1 ram2"
    apply (subgoal_tac "before us ram1 ram2 ∨ before us ram2 ram1") by auto

  assume "vs ≅ vs'" and pre_b: "pre_between vs ram1 ram2"
  then obtain n where vs': "vs' = rotate n vs" by (auto simp: congs_def)
  have "between vs ram1 ram2 = between (rotate n vs) ram1 ram2"
  proof (induct n)
    case 0 then show ?case by auto
  next
    case (Suc m) then show ?case apply simp
      apply (subgoal_tac " between (rotate1 (rotate m vs)) ram1 ram2 = between (rotate m vs) ram1 ram2")
      by (auto intro: help [symmetric] pre_b)
  qed
  with vs' show ?thesis by auto
qed

lemma between_inter_empty:
 "pre_between vs ram1 ram2 ==>
  set (between vs ram1 ram2) ∩ set (between vs ram2 ram1) = {}"
apply (case_tac "before vs ram1 ram2")
 apply (simp add: pre_between_def)
 apply (elim conjE)
 apply (frule (1) before_vs)
 apply (subgoal_tac "distinct (fst (splitAt ram1 vs) @
          ram1 # fst (splitAt ram2 (snd (splitAt ram1 vs))) @ ram2 # snd (splitAt ram2 vs))")
  apply (thin_tac "vs = fst (splitAt ram1 vs) @
          ram1 # fst (splitAt ram2 (snd (splitAt ram1 vs))) @ ram2 # snd (splitAt ram2 vs)")
  apply (frule (1) before_dist_fst_snd)
  apply(simp)
  apply blast
 apply (simp only:)
apply (simp add: before_xor)
apply (subgoal_tac "pre_between vs ram2 ram1")
 apply (simp add: pre_between_def)
 apply (elim conjE)
 apply (frule (1) before_vs)
 apply (subgoal_tac "distinct (fst (splitAt ram2 vs) @
          ram2 # fst (splitAt ram1 (snd (splitAt ram2 vs))) @ ram1 # snd (splitAt ram1 vs))")
  apply (thin_tac "vs = fst (splitAt ram2 vs) @
          ram2 # fst (splitAt ram1 (snd (splitAt ram2 vs))) @ ram1 # snd (splitAt ram1 vs)")
  apply simp
  apply blast
 apply (simp only:)
by (rule pre_between_symI)


(*********************** between - is_nextElem *************************)
subsubsection {* @{text "between is_nextElem"} *}



lemma is_nextElem_or1: "pre_between vs ram1 ram2 ==>
  is_nextElem vs x y ==> before vs ram1 ram2 ==>
  is_sublist [x,y] (ram1 # between vs ram1 ram2 @ [ram2])
 ∨  is_sublist [x,y] (ram2 # between vs ram2 ram1 @ [ram1])"
proof -
  assume p: "pre_between vs ram1 ram2" and is_nextElem: "is_nextElem vs x y" and b: "before vs ram1 ram2"
  from p have r1: "ram1 ∈ set vs" by (auto simp: pre_between_def)
  def bs ≡ "[ram1] @ (between vs ram1 ram2) @ [ram2]"
  have rule1: "x ∈ set (ram1 # (between vs ram1 ram2)) ==> is_sublist [x,y] bs"
  proof -
    assume xin:"x ∈ set (ram1 # (between vs ram1 ram2))"
    with bs_def have xin2: "x ∈ set bs" by auto
    def s ≡ "snd (splitAt ram1 vs)"
    from r1 s_def have sub1:"is_sublist (ram1 # s) vs" by (auto intro: splitAt_is_sublist2R)
    from b p s_def have "ram2 ∈ set s" by (auto intro!: before_dist_r2 simp: pre_between_def)
    then have "is_prefix (fst (splitAt ram2 s) @ [ram2]) s" by (auto intro!: splitAt_is_prefix)
    then have "is_prefix ([ram1] @ ((fst (splitAt ram2 s)) @ [ram2])) ([ram1] @ s)" by (rule_tac is_prefix_add) auto
    with sub1 have "is_sublist (ram1 # (fst (splitAt ram2 s)) @ [ram2]) vs" apply (rule_tac is_sublist_trans) apply (rule is_prefix_sublist)
      by simp_all
    with p b s_def bs_def have subl: "is_sublist bs vs" by (auto)
    with p have db: "distinct bs" by (auto simp: pre_between_def)
    with xin bs_def have xnlb:"x ≠ last bs" by auto
    with p is_nextElem subl xin2 show "is_sublist [x,y] bs" apply (rule_tac is_sublist_is_nextElem) by (auto simp: pre_between_def)
  qed
  def bs2 ≡ "[ram2] @ (between vs ram2 ram1) @ [ram1]"
  have rule2: "x ∈ set (ram2 # (between vs ram2 ram1)) ==> is_sublist [x,y] bs2"
  proof -
    assume xin:"x ∈ set (ram2 # (between vs ram2 ram1))"
    with bs2_def have xin2: "x ∈ set bs2" by auto
    def cs1 ≡ "ram2 # snd (splitAt ram2 vs)"
    then have cs1ne: "cs1 ≠ []" by auto
    def cs2 ≡ "fst (splitAt ram1 vs)"
    def cs2ram1 ≡ "cs2 @ [ram1]"
    from cs1_def cs2_def bs2_def p b have bs2: "bs2 = cs1 @ cs2 @ [ram1]" by (auto simp: pre_between_def)
    have "x ∈ set cs1 ==> x ≠ last cs1 ==> is_sublist [x,y] cs1"
    proof-
      assume xin2: "x ∈ set cs1" and xnlcs1: "x ≠ last cs1"
      from cs1_def p have "is_sublist cs1 vs" by (simp add: pre_between_def)
      with p is_nextElem xnlcs1  xin2 show ?thesis  apply (rule_tac is_sublist_is_nextElem) by (auto simp: pre_between_def)
    qed
    with bs2 have incs1nl: "x ∈ set cs1 ==> x ≠ last cs1 ==> is_sublist [x,y] bs2"
      apply (auto simp: is_sublist_def) apply (intro exI)
      apply (subgoal_tac "as @ x # y # bs @ cs2 @ [ram1] = as @ x # y # (bs @ cs2 @ [ram1])")
      apply assumption by auto
    have "x = last cs1 ==> y = hd (cs2 @ [ram1])"
    proof -
      assume xl: "x = last cs1"
      from p have "distinct vs" by auto
      with p have "vs = fst (splitAt ram2 vs) @ ram2 # snd (splitAt ram2 vs)" by (auto intro: splitAt_ram)
      with cs1_def have "last vs = last (fst (splitAt ram2 vs) @ cs1)" by auto
      with cs1ne have "last vs = last cs1" by auto
      with xl have "x = last vs" by auto
      with p is_nextElem have yhd: "y = hd vs" by auto
      from p have "vs = fst (splitAt ram1 vs) @ ram1 # snd (splitAt ram1 vs)" by (auto intro: splitAt_ram)
      with yhd cs2ram1_def cs2_def have yhd2: "y = hd (cs2ram1 @ snd (splitAt ram1 vs))" by auto
      from cs2ram1_def have "cs2ram1 ≠ []" by auto
      then have "hd (cs2ram1 @ snd(splitAt ram1 vs)) = hd (cs2ram1)" by auto
      with yhd2 cs2ram1_def show ?thesis by auto
    qed
    with bs2 cs1ne have "x = last cs1 ==> is_sublist [x,y] bs2"
      apply (auto simp: is_sublist_def) apply (intro exI)
      apply (subgoal_tac "cs1 @ cs2 @ [ram1] = butlast cs1 @ last cs1 # hd (cs2 @ [ram1]) # tl (cs2 @ [ram1])")
      apply assumption by auto
    with incs1nl have incs1: "x ∈ set cs1 ==> is_sublist [x,y] bs2" by auto
    have "x ∈ set cs2 ==> is_sublist [x,y] (cs2 @ [ram1])"
    proof-
      assume xin2': "x ∈ set cs2"
      then have xin2: "x ∈ set (cs2 @ [ram1])" by auto
      def fr2 ≡ "snd (splitAt ram1 vs)"
      from p have "vs = fst (splitAt ram1 vs) @ ram1 # snd (splitAt ram1 vs)" by (auto intro: splitAt_ram)
      with fr2_def cs2_def have "vs = cs2 @ [ram1] @ fr2" by simp
      with p xin2'  have "x ≠ ram1" by (auto simp: pre_between_def)
      then have  xnlcs2: "x ≠ last (cs2 @ [ram1])" by auto
      from cs2_def p have "is_sublist (cs2 @ [ram1]) vs" by (simp add: pre_between_def)
      with p is_nextElem xnlcs2  xin2 show ?thesis  apply (rule_tac is_sublist_is_nextElem) by (auto simp: pre_between_def)
    qed
    with bs2 have "x ∈ set cs2 ==> is_sublist [x,y] bs2"
      apply (auto simp: is_sublist_def) apply (intro exI)
      apply (subgoal_tac "cs1 @ as @ x # y # bs = (cs1 @ as) @ x # y # bs")
      apply assumption by auto
    with p b cs1_def cs2_def incs1 xin show ?thesis by auto
  qed
  from is_nextElem have "x ∈ set vs" by auto
  with b p have "x = ram1 ∨ x ∈ set (between vs ram1 ram2) ∨ x = ram2 ∨ x ∈ set (between vs ram2 ram1)" by (rule_tac between_in) auto
  then have "x ∈ set (ram1 # (between vs ram1 ram2)) ∨ x ∈ set (ram2 # (between vs ram2 ram1))" by auto
  with rule1 rule2 bs_def bs2_def show ?thesis by auto
qed


lemma is_nextElem_or: "pre_between vs ram1 ram2 ==> is_nextElem vs x y ==>
  is_sublist [x,y] (ram1 # between vs ram1 ram2 @ [ram2]) ∨  is_sublist [x,y] (ram2 # between vs ram2 ram1 @ [ram1])"
proof (cases "before vs ram1 ram2")
  case True
  assume "pre_between vs ram1 ram2" "is_nextElem vs x y"
  with True show ?thesis by (rule_tac is_nextElem_or1)
next
  assume p: "pre_between vs ram1 ram2" and is_nextElem: "is_nextElem vs x y"
  from p have p': "pre_between vs ram2 ram1" by (auto intro: pre_between_symI)
  case False with p have "before vs ram2 ram1" by auto
  with p' is_nextElem show ?thesis apply (drule_tac is_nextElem_or1) apply assumption+ by auto
qed

declare  distinct_append distinct.simps [simp del]

lemma(*<*) between_xor1: (*>*)
 "pre_between vs ram1 ram2 ==> is_nextElem vs x y  ==> before vs ram1 ram2 ==>
     (is_sublist [x,y] (ram1 # between vs ram1 ram2 @ [ram2])
     = (¬ is_sublist [x,y] (ram2 # between vs ram2 ram1 @ [ram1])))"
  apply (rule iffI)

  apply (subgoal_tac "distinct (ram1 # between vs ram1 ram2 @ [ram2])")
  apply (subgoal_tac "distinct (ram2 # between vs ram2 ram1 @ [ram1])")
  defer
  apply (rule between_distinct_r12) apply (simp add: pre_between_def) apply (simp add: pre_between_def) apply force
  apply (rule between_distinct_r12) apply (simp add: pre_between_def) apply (simp add: pre_between_def)
  apply (drule is_nextElem_or) apply simp  apply simp

  apply (subgoal_tac "x ∈ set vs ∧ y ∈ set vs")
  defer
  apply force

  apply (elim conjE) apply (frule between_in) apply simp apply assumption
  apply (subgoal_tac "distinct (fst (splitAt ram1 vs) @ ram1 # between vs ram1 ram2 @ ram2 # snd (splitAt ram2 vs))")
  defer
  apply (subgoal_tac "fst (splitAt ram1 vs) @ ram1 # between vs ram1 ram2 @ ram2 # snd (splitAt ram2 vs) = vs")
  apply (simp add: pre_between_def between_vs) apply (rule sym) apply (rule between_vs) apply simp apply simp

  apply (case_tac "x = ram1") apply simp
  apply (case_tac "x = ram2") apply (rule ccontr)  apply (simp add: distinct_append distinct.simps)
  apply (case_tac "x ∈ set (between vs ram1 ram2)")
    apply (thin_tac "distinct (ram1 # between vs ram1 ram2 @ [ram2])") apply (thin_tac "distinct (ram2 # between vs ram2 ram1 @ [ram1])")
    apply (rule ccontr) apply (case_tac "x ∈ set (snd (splitAt ram2 vs))")
    apply (subgoal_tac "x ∈  set (between vs ram1 ram2) ∩ set (snd (splitAt ram2 vs))")
    apply (simp add: distinct_append distinct.simps) apply simp
    apply (subgoal_tac "x ∈ set (fst (splitAt ram1 vs))") apply (simp add: distinct_append distinct.simps)

    apply (subgoal_tac "x ∈ set (fst (splitAt ram1 vs)) ∩ (set (fst (splitAt ram2 (snd (splitAt ram1 vs)))) ∪ set (snd (splitAt ram2 vs)))")
    apply (simp) apply (rule IntI) apply simp apply simp apply (rule ccontr) apply (simp add: distinct_append distinct.simps)
    apply (subgoal_tac "x ∈ set (snd (splitAt ram2 vs) @ fst (splitAt ram1 vs) @ [ram1])") apply simp apply (rule is_sublist_in) apply assumption
  apply (subgoal_tac "x ∈ set (between vs ram2 ram1)")
  apply (subgoal_tac "x ∈  set ((ram1 # between vs ram1 ram2) @ [ram2])") apply simp
  apply (rule is_sublist_in) apply simp by simp

declare  distinct_append distinct.simps [simp]

lemma(*<*) between_xor: (*>*)
 "pre_between vs ram1 ram2 ==> is_nextElem vs x y  ==>
     (is_sublist [x,y] (ram1 # between vs ram1 ram2 @ [ram2])
     = (¬ is_sublist [x,y] (ram2 # between vs ram2 ram1 @ [ram1])))"
proof (cases "before vs ram1 ram2")
  case True
  assume "pre_between vs ram1 ram2" "is_nextElem vs x y"
  with True show ?thesis by (rule_tac between_xor1)
next
  assume p: "pre_between vs ram1 ram2" and is_nextElem: "is_nextElem vs x y"
  from p have p': "pre_between vs ram2 ram1" by (auto intro: pre_between_symI)
  case False with p have "before vs ram2 ram1" by auto
  with p' is_nextElem show ?thesis apply (drule_tac between_xor1) apply assumption+ by auto
qed

lemma(*<*) between_eq1: (*>*)
  "pre_between vs ram1 ram2 ==>
  before vs ram1 ram2 ==>
   ∃as bs. vs = as @[ram1] @ between vs ram1 ram2 @ [ram2] @ bs"
apply auto apply (intro exI) apply (simp add: pre_between_def) apply auto apply (frule_tac before_vs) by auto


lemma(*<*) between_eq2: (*>*)
  "pre_between vs ram1 ram2 ==>
  before vs ram2 ram1 ==>
   ∃as bs cs. between vs ram1 ram2 = cs @ as ∧ vs = as @[ram2] @ bs @ [ram1] @ cs"
  apply (subgoal_tac "pre_between vs ram2 ram1")
  apply auto apply (intro exI conjI) apply simp  apply (simp add: pre_between_def) apply auto
  apply (frule_tac before_vs) apply auto by (auto simp: pre_between_def)

lemma is_sublist_same_len[simp]:
 "length xs = length ys ==> is_sublist xs ys = (xs = ys)"
apply(cases xs)
 apply simp
apply(rename_tac a as)
apply(cases ys)
 apply simp
apply(rename_tac b bs)
apply(case_tac "a = b")
 apply(subst is_sublist_rec)
 apply simp
apply simp
done


lemma is_nextElem_between_empty[simp]:
 "distinct vs ==> is_nextElem vs a b ==> between vs a b = []"
apply (simp add: is_nextElem_def between_def split_def)
apply (cases "vs") apply simp+
 apply (case_tac "list")
 apply (simp add: is_sublist_def)
 apply (erule disjE)
  apply (elim exE) apply (case_tac "as") apply simp+
apply (simp split: split_if_asm)
 apply (case_tac "a=aaa")
  apply simp
 apply (rule conjI)
  apply (rule impI) apply simp
 apply simp
apply (case_tac "b = aa")
 apply (simp add: is_sublist_def)
 apply (erule disjE)
  apply (elim exE)
  apply (case_tac "as")
   apply simp
  apply simp
  apply (case_tac "listb")
   apply simp
  apply simp
 apply simp
 apply (case_tac "lista" rule: rev_exhaust)
  apply simp
 apply simp
apply simp
apply (subgoal_tac "aa # aaa # lista = vs")
 apply (thin_tac "vs = aa # aaa # lista")
 apply simp
 apply (subgoal_tac "distinct vs")
  apply (simp add: is_sublist_def)
  apply (elim exE)
  by auto


lemma is_nextElem_between_empty': "between vs a b = [] ==> distinct vs ==> a ∈ set vs ==> b ∈ set vs  ==>
  a ≠ b ==> is_nextElem vs a b"
apply (simp add: is_nextElem_def between_def split_def split: split_if_asm)
 apply (case_tac vs) apply simp
 apply simp
 apply (rule conjI)
  apply (rule impI)
  apply simp
 apply (case_tac "aa = b")
  apply simp
  apply (rule impI)
  apply (case_tac "list" rule: rev_exhaust)
   apply simp
  apply simp
  apply (case_tac "a = y") apply simp
  apply simp
  apply (elim conjE)
  apply (drule split_list_first)
  apply (elim exE)
  apply simp
 apply (rule impI)
 apply (subgoal_tac "b ≠ aa")
  apply simp
  apply (case_tac "a = aa")
   apply simp
   apply (case_tac "list") apply simp
   apply simp
   apply (case_tac "aaa = b") apply (simp add: is_sublist_def) apply force
   apply simp
  apply simp
  apply (drule split_list_first)
  apply (elim exE)
  apply simp
  apply (case_tac "zs") apply simp
  apply simp
  apply (case_tac "aaa = b")
   apply simp
   apply (simp add: is_sublist_def) apply force
  apply simp
 apply force
apply (case_tac vs) apply simp
apply simp
apply (rule conjI)
 apply (rule impI) apply simp
apply (rule impI)
apply (case_tac "b = aa")
 apply simp
 apply (case_tac "list" rule: rev_exhaust) apply simp
 apply simp
 apply (case_tac "a = y") apply simp
 apply simp
 apply (drule split_list_first)
 apply (elim exE)
 apply simp
apply simp apply (case_tac "a = aa") by auto


lemma between_nextElem: "pre_between vs u v ==>
 between vs u (nextElem vs (hd vs) v) = between vs u v @ [v]"
apply(subgoal_tac "pre_between vs v u")
 prefer 2 apply (clarsimp simp add:pre_between_def)
apply(case_tac "before vs u v")
apply(drule (1) between_eq2)
 apply(clarsimp simp:pre_between_def hd_append split:list.split)
 apply(simp add:between_def split_def)
 apply(fastsimp simp:neq_Nil_conv)
apply (simp only:before_xor)
apply(drule (1) between_eq2)
apply(clarsimp simp:pre_between_def hd_append split:list.split)
apply (simp add: append_eq_Cons_conv)
apply(fastsimp simp:between_def split_def)
done



(******************** section split_face ********************************)

lemma nextVertices_in_face[simp]: "v ∈ \<V> f ==> fn • v ∈ \<V> f"
proof -
  assume v: "v ∈ \<V> f"
  then have f: "vertices f ≠ []" by auto
  show ?thesis apply (simp add: nextVertices_def)
    apply (induct n) by (auto simp: f v)
qed



subsubsection {* @{text "is_nextElem edges"} equivalence *}


lemma is_nextElem_edges1: "distinct (vertices f) ==> (a,b) ∈ edges (f::face) ==> is_nextElem (vertices f) a b" apply (simp add: edges_face_def nextVertex_def) apply (rule is_nextElem1) by auto


lemma is_nextElem_edges2:
 "distinct (vertices f) ==> is_nextElem (vertices f) a b ==>
 (a,b) ∈ edges (f::face)"
apply (auto simp add: edges_face_def nextVertex_def)
apply (rule sym)
apply (rule is_nextElem2) by (auto  intro: is_nextElem_a)

lemma is_nextElem_edges_eq[simp]:
 "distinct (vertices (f::face)) ==>
 (a,b) ∈ edges f = is_nextElem (vertices f) a b"
by (auto intro: is_nextElem_edges1 is_nextElem_edges2)



(*********************** nextVertex *****************************)
subsubsection {* @{const nextVertex} *}

lemma nextElem_suc2: "distinct (vertices f) ==> last (vertices f) = v ==> v ∈ set (vertices f) ==> f • v = hd (vertices f)"
proof -
  assume dist: "distinct (vertices f)" and last: "last (vertices f) = v" and v: "v ∈ set (vertices f)"
  def ls ≡ "vertices f"
  have ind: "!! c. distinct ls ==> last ls = v ==> v ∈ set ls ==> nextElem ls c v = c"
  proof (induct ls)
    case Nil then show ?case by auto
  next
    case (Cons m ms)
    then show ?case
    proof (cases "m = v")
      case True with Cons have "ms = []"  apply (cases ms rule: rev_exhaust) by auto
      then show ?thesis by auto
    next
      case False with Cons have a1: "v ∈ set ms" by auto
      then have ms: "ms ≠ []" by auto

      with False Cons ms have "nextElem ms c v = c" apply (rule_tac Cons) by simp_all
      with False ms show ?thesis by simp
    qed
  qed
  from dist ls_def last v have "nextElem ls (hd ls) v = hd ls" apply (rule_tac ind) by auto
  with ls_def show ?thesis by (simp add: nextVertex_def)
qed

lemma nextVertex_congs_eq: "f1 ≅ f2 ==> distinct (vertices f1) ==> v ∈ \<V> f1 ==> f1 • v = f2 • v"
 by (simp add: cong_face_def nextVertex_def)
  (rule nextElem_congs_eq)



(*********************** split_face ****************************)
subsection {* @{const split_face} *}


constdefs pre_split_face :: "face => nat => nat => nat list => bool"
"pre_split_face oldF ram1 ram2 newVertexList ≡
   distinct (vertices oldF) ∧ distinct (newVertexList)
  ∧ \<V> oldF ∩ set newVertexList = {}
  ∧ ram1 ∈ \<V> oldF ∧ ram2 ∈ \<V> oldF ∧ ram1 ≠ ram2"

declare pre_split_face_def [simp]


lemma pre_split_face_p_between[intro]:
  "pre_split_face oldF ram1 ram2 newVertexList ==> pre_between (vertices oldF) ram1 ram2"  by (simp add: pre_between_def)

lemma pre_split_face_symI:
  "pre_split_face oldF ram1 ram2 newVertexList ==> pre_split_face oldF ram2 ram1 newVertexList" by auto


lemma pre_split_face_rev[intro]:
  "pre_split_face oldF ram1 ram2 newVertexList ==> pre_split_face oldF ram1 ram2 (rev newVertexList)" by auto

lemma split_face_distinct1:
  "(f12, f21) = split_face oldF ram1 ram2 newVertexList ==> pre_split_face oldF ram1 ram2 newVertexList ==>
    distinct (vertices f12)"
proof -
  assume split: "(f12, f21) = split_face oldF ram1 ram2 newVertexList" and p: "pre_split_face oldF ram1 ram2 newVertexList"
  def old_vs ≡ "vertices oldF"
  with p have d_old_vs: "distinct old_vs" by auto
  from p have p2: "pre_between (vertices oldF) ram1 ram2" by auto
  have rule1: "before old_vs ram1 ram2 ==> distinct (vertices f12)"
  proof -
    assume b: "before old_vs ram1 ram2"
    with split p have "f12 = Face (rev newVertexList @ ram1 # between (vertices oldF) ram1 ram2 @ [ram2]) Nonfinal" by (simp add: split_face_def)
    then have h1:"vertices f12 = rev newVertexList @ ram1 # between (vertices oldF) ram1 ram2 @ [ram2]" by auto
    from p have d1: "distinct(ram1 # between (vertices oldF) ram1 ram2 @ [ram2])" by (auto del: notI)
    from b p p2 old_vs_def have d2: "set (ram1 # between (vertices oldF) ram1 ram2 @ [ram2]) ∩ set newVertexList = {}"
      by (auto dest!: splitAt_in_fst splitAt_in_snd)
    with h1 d1 p show ?thesis by auto
  qed
  have rule2: "before old_vs ram2 ram1 ==> distinct (vertices f12)"
  proof -
    assume b: "before old_vs ram2 ram1"
    from p have p3: "pre_split_face oldF ram1 ram2 newVertexList"
       by (auto intro: pre_split_face_symI)
    then have p4: "pre_between (vertices oldF) ram2 ram1" by auto
    with split p have
     "f12 = Face (rev newVertexList @ ram1 # between (vertices oldF) ram1 ram2 @ [ram2]) Nonfinal"
      by (simp add: split_face_def)
    then have h1:"vertices f12 = rev newVertexList @ ram1 # between (vertices oldF) ram1 ram2 @ [ram2]"
      by auto
    from p3 have d1: "distinct(ram1 # between (vertices oldF) ram1 ram2 @ [ram2])"
    by (auto del: notI)
    from b p3 p4 old_vs_def
    have d2: "set (ram1 # between (vertices oldF) ram1 ram2 @ [ram2]) ∩ set newVertexList = {}"
      by auto
    with h1 d1 p show ?thesis by auto
  qed
  from p2 rule1 rule2 old_vs_def show ?thesis by auto
qed

lemma split_face_distinct1'[intro]:
  "pre_split_face oldF ram1 ram2 newVertexList ==>
    distinct (vertices (fst(split_face oldF ram1 ram2 newVertexList)))"
apply (rule_tac split_face_distinct1)
  by (auto simp del: pre_split_face_def simp: split_face_def)

lemma split_face_distinct2:
  "(f12, f21) = split_face oldF ram1 ram2 newVertexList ==>
   pre_split_face oldF ram1 ram2 newVertexList ==> distinct (vertices f21)"
proof -
  assume split: "(f12, f21) = split_face oldF ram1 ram2 newVertexList"
    and p: "pre_split_face oldF ram1 ram2 newVertexList"
  def old_vs ≡ "vertices oldF"
  with p have d_old_vs: "distinct old_vs" by auto
  with p have p1: "pre_split_face oldF ram1 ram2 newVertexList" by auto
  from p have p2: "pre_between (vertices oldF) ram1 ram2" by auto
  have rule1: "before old_vs ram1 ram2 ==> distinct (vertices f21)"
  proof -
    assume b: "before old_vs ram1 ram2"
    with split p
    have "f21 = Face (ram2 # between (vertices oldF) ram2 ram1 @ [ram1] @ newVertexList) Nonfinal"
      by (simp add: split_face_def)
    then have h1:"vertices f21 = ram2 # between (vertices oldF) ram2 ram1 @ [ram1] @ newVertexList"
      by auto
    from p have d1: "distinct(ram1 # between (vertices oldF) ram2 ram1 @ [ram2])"
       by (auto del: notI)
    from b p1 p2 old_vs_def
    have d2: "set (ram2 # between (vertices oldF) ram2 ram1 @ [ram1]) ∩ set newVertexList = {}"
      by auto
    with h1 d1 p1 show ?thesis by auto
  qed
  have rule2: "before old_vs ram2 ram1 ==> distinct (vertices f21)"
  proof -
    assume b: "before old_vs ram2 ram1"
    from p have p3: "pre_split_face oldF ram1 ram2 newVertexList"
      by (auto intro: pre_split_face_symI)
    then have p4: "pre_between (vertices oldF) ram2 ram1" by auto
    with split p
    have "f21 = Face (ram2 # between (vertices oldF) ram2 ram1 @ [ram1] @ newVertexList) Nonfinal"
      by (simp add: split_face_def)
    then have h1:"vertices f21 = ram2 # between (vertices oldF) ram2 ram1 @ [ram1] @ newVertexList"
      by auto
    from p3 have d1: "distinct(ram2 # between (vertices oldF) ram2 ram1 @ [ram1])"
      by (auto del: notI)
    from b p3 p4 old_vs_def
    have d2: "set (ram2 # between (vertices oldF) ram2 ram1 @ [ram1]) ∩ set newVertexList = {}"
      by auto
    with h1 d1 p1 show ?thesis by auto
  qed
  from p2 rule1 rule2 old_vs_def show ?thesis by auto
qed

lemma split_face_distinct2'[intro]:
  "pre_split_face oldF ram1 ram2 newVertexList ==> distinct (vertices (snd(split_face oldF ram1 ram2 newVertexList)))"
apply (rule_tac split_face_distinct2) by (auto simp del: pre_split_face_def simp: split_face_def)


declare pre_split_face_def [simp del]

lemma split_face_edges_or: "(f12, f21) = split_face oldF ram1 ram2 newVertexList ==> pre_split_face oldF ram1 ram2 newVertexList ==> (a, b) ∈ edges oldF ==> (a,b) ∈ edges f12 ∨ (a,b) ∈ edges f21"
proof -
  assume nf: "(f12, f21) = split_face oldF ram1 ram2 newVertexList" and p: "pre_split_face oldF ram1 ram2 newVertexList" and old:"(a, b) ∈ edges oldF"
  from p have d1:"distinct (vertices oldF)" by auto
  from nf p have d2: "distinct (vertices f12)" by (auto dest: pairD)
  from nf p have d3: "distinct (vertices f21)" by (auto dest: pairD)
  from p have p': "pre_between (vertices oldF) ram1 ram2" by auto
  from old d1 have is_nextElem: "is_nextElem (vertices oldF) a b" by simp
  with p have "is_sublist [a,b] (ram1 # (between (vertices oldF) ram1 ram2) @ [ram2]) ∨ is_sublist [a,b] (ram2 # (between (vertices oldF) ram2 ram1) @ [ram1])" apply (rule_tac is_nextElem_or) by auto
  then have "is_nextElem (rev newVertexList @ ram1 # between (vertices oldF) ram1 ram2 @ [ram2]) a b
    ∨ is_nextElem (ram2 # between (vertices oldF) ram2 ram1 @ ram1 # newVertexList) a b"
  proof (cases "is_sublist [a,b] (ram1 # (between (vertices oldF) ram1 ram2) @ [ram2])")
    case True then show ?thesis by (auto dest: is_sublist_add intro!: is_nextElem_sublistI)
  next
    case False
    assume "is_sublist [a,b] (ram1 # (between (vertices oldF) ram1 ram2) @ [ram2])
      ∨ is_sublist [a,b] (ram2 # (between (vertices oldF) ram2 ram1) @ [ram1])"
    with False have "is_sublist [a,b] (ram2 # (between (vertices oldF) ram2 ram1) @ [ram1])" by auto
    then show ?thesis apply (rule_tac disjI2) apply (rule_tac is_nextElem_sublistI)
      apply (subgoal_tac "is_sublist [a, b] ([] @ (ram2 # between (vertices oldF) ram2 ram1 @ [ram1]) @ newVertexList)") apply force by (frule is_sublist_add)
  qed
  with nf d1 d2 d3 show ?thesis by (simp add: split_face_def)
qed


lemma is_nextElem_hd_last: "distinct vs ==> is_nextElem vs x y ==> y = hd vs ==> x = last vs"
apply (cases vs) apply (simp add: is_nextElem_def is_sublist_def) apply simp apply auto apply (auto simp: is_nextElem_def is_sublist_def)
apply (case_tac as) apply simp+ apply (case_tac as) by simp+


lemma split_face_xor: "(f12, f21) = split_face oldF ram1 ram2 newVertexList ==>
  pre_split_face oldF ram1 ram2 newVertexList ==>
  (ram1,ram2) ∉ edges oldF ==> (ram2,ram1) ∉ edges oldF ==>
  (a, b) ∈ edges oldF ==> (a,b) ∈ edges f12 = ((a,b) ∉ edges f21)"
proof
  assume split: "(f12, f21) = split_face oldF ram1 ram2 newVertexList" and
    pre_fdg: "pre_split_face oldF ram1 ram2 newVertexList" and
    oldF: "(ram1, ram2) ∉ edges oldF" "(ram2, ram1) ∉ edges oldF" "(a, b) ∈ edges oldF" and
    f12_edge: "(a, b) ∈ edges f12"
  from pre_fdg split oldF
  have oldF': "is_nextElem (vertices oldF) a b"
    by (auto simp: pre_split_face_def)

  from pre_fdg split oldF
  have "¬ is_nextElem (vertices oldF) ram1 ram2 ∧ ¬ is_nextElem (vertices oldF) ram2 ram1"
    by (auto simp: pre_split_face_def split_face_distinct1 split_face_distinct2 )
  then have oldF_ram: "¬ is_nextElem (vertices oldF) ram1 ram2" "¬ is_nextElem (vertices oldF) ram2 ram1"by auto


  from pre_fdg split f12_edge have f12_edge': "is_nextElem (vertices f12) a b" by (simp add: split_face_distinct1)

  from pre_fdg oldF' have a': "a ∉ set newVertexList" by (auto simp: pre_split_face_def)
  from pre_fdg oldF' have b': "b ∉ set newVertexList" by (auto simp: pre_split_face_def)

  from a' have rule1: "¬ is_sublist [a, b] (newVertexList)" by (auto simp:is_sublist_in)
  from a' have rule2: "¬ is_sublist [a, b] (rev newVertexList)" apply (rule_tac ccontr) apply simp apply (drule is_sublist_in) by simp

  from pre_fdg split have f21: "f21 = Face (ram2 # between (vertices oldF) ram2 ram1 @ ram1 # newVertexList) Nonfinal"
    by (simp add: split_face_def)
  from pre_fdg split have f12: "f12 = Face (rev newVertexList @ ram1 # between (vertices oldF) ram1 ram2 @ [ram2]) Nonfinal"
    by (simp add: split_face_def)


  from f12_edge' f12 have "a ≠ ram2 ==> is_sublist [a, b] (vertices f12)"
    by (simp add: is_nextElem_def)
  with pre_fdg split f12 rule2 a' have "a ≠ ram2 ==> is_sublist [a,b] (ram1 # between (vertices oldF) ram1 ram2 @ [ram2])"
    apply (subgoal_tac "distinct (rev newVertexList @ ram1 # between (vertices oldF) ram1 ram2 @ [ram2])")
     prefer 2 apply (drule (1) split_face_distinct1) apply simp
    apply (drule is_sublist_at5) apply simp
    apply (case_tac newVertexList) by auto
  with pre_fdg oldF' have "a ≠ ram2 ==> ¬ is_sublist [a,b] (ram2 # between (vertices oldF) ram2 ram1 @ [ram1])"
    apply (subgoal_tac "pre_between (vertices oldF) ram1 ram2") apply (drule between_xor) by auto
  with pre_fdg split f21 rule1 f12_edge' b' have rule_a: "a ≠ ram2 ==> ¬ is_sublist [a, b] (vertices f21)"  apply (rule_tac ccontr) apply simp
    apply (subgoal_tac "distinct ((between (vertices oldF) ram2 ram1 @ [ram1]) @ newVertexList)")
    apply (drule is_sublist_at5) apply simp apply simp
    apply (case_tac newVertexList) apply simp apply (elim conjE) apply simp
    apply (drule split_face_distinct2) by auto

  have help: "!! A B C. C ∩ (A ∪ B) = {} ==> B ∩ C = {}" by auto

  from pre_fdg have "before (vertices oldF) ram1 ram2 ∨ before (vertices oldF) ram2 ram1"
    apply (rule_tac before_or) by (auto simp: pre_split_face_def)
  with pre_fdg oldF_ram  have rule3: "¬ is_sublist [ram2, ram1] (ram2 # between (vertices oldF) ram2 ram1 @ [ram1])"
    apply (elim disjE) apply (frule between_vs) apply force
    apply (subgoal_tac "pre_between (vertices oldF) ram1 ram2") apply (rule ccontr)
    apply (subgoal_tac "between (vertices oldF) ram2 ram1 = []")
    apply (simp  add: is_nextElem_def) apply (elim conjE) apply (case_tac "(vertices oldF)" rule: rev_exhaust)  apply simp apply simp
    apply (case_tac "ys") apply simp apply simp  apply simp
    apply (case_tac "snd (splitAt ram2 (vertices oldF))") apply simp
    apply (case_tac "fst (splitAt ram1 (vertices oldF))") apply simp apply simp apply (simp add: pre_split_face_def)
    apply (subgoal_tac "distinct (ram2 # a # list @ [ram1])") apply (rotate_tac -1) apply (frule is_sublist_distinct_prefix)
    apply simp apply simp apply (case_tac "snd (splitAt ram1 (fst (splitAt ram2 (vertices oldF))))") apply force apply force
    apply simp
    apply (subgoal_tac "distinct (ram2 # a # list @ fst (splitAt ram1 (vertices oldF)) @ [ram1])")  apply (rotate_tac -1) apply (frule is_sublist_distinct_prefix)
    apply simp apply simp
    apply (subgoal_tac "distinct (fst (splitAt ram1 (vertices oldF)) @ ram1 # fst (splitAt ram2 (snd (splitAt ram1 (vertices oldF)))) @ ram2 # a # list)")
    apply (thin_tac "vertices oldF =
      fst (splitAt ram1 (vertices oldF)) @ ram1 # fst (splitAt ram2 (snd (splitAt ram1 (vertices oldF)))) @ ram2 # a # list")
    apply simp apply (elim conjE) apply (rule help) apply simp
    apply (simp add: pre_split_face_def)
    apply force

    apply (frule between_vs) apply (simp add: pre_between_def pre_split_face_def)
    apply (subgoal_tac "pre_between (vertices oldF) ram2 ram1") apply (rule ccontr) apply simp
    apply (subgoal_tac "fst (splitAt ram1 (snd (splitAt ram2 (vertices oldF)))) = []")
    apply (simp  add: is_nextElem_def) apply (elim conjE) apply (simp add: is_sublist_def)
    apply (subgoal_tac  "distinct (ram2 # fst (splitAt ram1 (snd (splitAt ram2 (vertices oldF)))) @ [ram1])")
    apply (rotate_tac -1) apply (frule is_sublist_distinct_prefix) apply simp
    apply (case_tac "fst (splitAt ram1 (snd (splitAt ram2 (vertices oldF))))") apply simp apply simp

    apply (subgoal_tac "distinct (fst (splitAt ram2 (vertices oldF)) @
     ram2 # fst (splitAt ram1 (snd (splitAt ram2 (vertices oldF)))) @ ram1 # snd (splitAt ram1 (vertices oldF)))")
    apply (thin_tac "vertices oldF =
     fst (splitAt ram2 (vertices oldF)) @
     ram2 # fst (splitAt ram1 (snd (splitAt ram2 (vertices oldF)))) @ ram1 # snd (splitAt ram1 (vertices oldF))")
    apply force apply (simp add: pre_split_face_def) apply (rule pre_between_symI) by force


  from pre_fdg have "before (vertices oldF) ram2 ram1 ∨ before (vertices oldF) ram1 ram2"
    apply (rule_tac before_or) by (auto simp: pre_split_face_def)
  with pre_fdg oldF_ram  have rule4: "¬ is_sublist [ram1, ram2] (ram1 # between (vertices oldF) ram1 ram2 @ [ram2])"
    apply (elim disjE) apply (frule between_vs) apply (simp add: pre_split_face_def pre_between_def)
    apply (subgoal_tac "pre_between (vertices oldF) ram2 ram1") apply (rule ccontr)
    apply (subgoal_tac "between (vertices oldF) ram1 ram2 = []")
    apply (simp  add: is_nextElem_def) apply (elim conjE) apply (case_tac "(vertices oldF)" rule: rev_exhaust)  apply simp apply simp
    apply (case_tac "ys") apply simp apply simp  apply simp
    apply (case_tac "snd (splitAt ram1 (vertices oldF))") apply simp
    apply (case_tac "fst (splitAt ram2 (vertices oldF))") apply simp apply simp apply (simp add: pre_split_face_def)
    apply (subgoal_tac "distinct (ram1 # a # list @ [ram2])") apply (rotate_tac -1) apply (frule is_sublist_distinct_prefix)
    apply simp apply simp apply (case_tac "snd (splitAt ram2 (fst (splitAt ram1 (vertices oldF))))") apply force apply bestsimp
    apply simp
    apply (subgoal_tac "distinct (ram1 # a # list @ fst (splitAt ram2 (vertices oldF)) @ [ram2])")  apply (rotate_tac -1) apply (frule is_sublist_distinct_prefix)
    apply simp apply simp
    apply (subgoal_tac "distinct (fst (splitAt ram2 (vertices oldF)) @ ram2 # fst (splitAt ram1 (snd (splitAt ram2 (vertices oldF)))) @ ram1 # a # list)")
    apply (thin_tac "vertices oldF =
      fst (splitAt ram2 (vertices oldF)) @ ram2 # fst (splitAt ram1 (snd (splitAt ram2 (vertices oldF)))) @ ram1 # a # list")
    apply simp apply (elim conjE) apply (rule help) apply simp
    apply (simp add: pre_split_face_def) apply (simp add: pre_split_face_def pre_between_def)

    apply (frule between_vs) apply force
    apply (subgoal_tac "pre_between (vertices oldF) ram1 ram2") apply (rule ccontr) apply simp
    apply (subgoal_tac "fst (splitAt ram2 (snd (splitAt ram1 (vertices oldF)))) = []")
    apply (simp  add: is_nextElem_def) apply (elim conjE) apply (simp add: is_sublist_def)
    apply (subgoal_tac  "distinct (ram1 # fst (splitAt ram2 (snd (splitAt ram1 (vertices oldF)))) @ [ram2])")
    apply (rotate_tac -1) apply (frule is_sublist_distinct_prefix) apply simp
    apply (case_tac "fst (splitAt ram2 (snd (splitAt ram1 (vertices oldF))))") apply simp apply simp

    apply (subgoal_tac "distinct (fst (splitAt ram1 (vertices oldF)) @
     ram1 # fst (splitAt ram2 (snd (splitAt ram1 (vertices oldF)))) @ ram2 # snd (splitAt ram2 (vertices oldF)))")
    apply (thin_tac "vertices oldF =
     fst (splitAt ram1 (vertices oldF)) @
     ram1 # fst (splitAt ram2 (snd (splitAt ram1 (vertices oldF)))) @ ram2 # snd (splitAt ram2 (vertices oldF))")
    apply force apply (simp add: pre_split_face_def) by force


  from pre_fdg f12_edge' split have "¬ is_nextElem (vertices f21) a b"
    apply (rule_tac ccontr) apply simp
    apply (simp add: is_nextElem_def)
    apply (case_tac "a = ram2")
     apply (simp  add: f12 f21)
     apply (case_tac "newVertexList" rule:rev_exhaust)
      apply (subgoal_tac "ram2 ≠ ram1")
       apply simp
       apply (case_tac "b = ram1") apply (simp add: rule3) apply simp
       apply (subgoal_tac "distinct (between (vertices oldF) ram1 ram2 @ [ram2])")
        apply (rotate_tac -1)
         apply (drule is_sublist_x_last) apply simp apply force
        apply (drule split_face_distinct1) apply simp
        apply simp
       apply (force simp: pre_split_face_def)
      apply simp
      apply (case_tac "ram2 = y") apply (simp add: pre_split_face_def) apply force
      apply (case_tac "b = y")
       apply (subgoal_tac "b ∉ set (newVertexList)") apply simp
       apply (rule b')
      apply simp
      apply (subgoal_tac "distinct (rev ys @ ram1 # between (vertices oldF) ram1 ram2 @ [ram2])")
       apply (drule  is_sublist_x_last)  apply simp apply force
      apply (drule split_face_distinct1) apply simp
      apply simp
     apply (frule rule_a)  apply (simp add: f12 f21)
     apply (case_tac newVertexList rule:rev_exhaust)
      apply simp
      apply (case_tac "ram1 = ram2")  apply (simp only: pre_split_face_def) apply (elim conjE)  apply (simp only:)  apply simp
      apply (simp add: rule4)
     apply simp
     apply (subgoal_tac "distinct(y # rev ys @ ram1 # between (vertices oldF) ram1 ram2 @ [ram2])")
      prefer 2 apply (drule split_face_distinct1) apply simp apply simp
     apply (frule is_sublist_distinct_prefix) apply simp
     apply (case_tac "ys" rule:rev_exhaust) by simp_all

  with pre_fdg split show "(a,b) ∉ edges f21" by (simp add: split_face_distinct2)
next
  assume "(f12, f21) = split_face oldF ram1 ram2 newVertexList" "pre_split_face oldF ram1 ram2 newVertexList"
     "(ram1, ram2) ∉ edges oldF" "(ram2, ram1) ∉ edges oldF" "(a, b) ∈ edges oldF" "(a, b) ∉ edges f21"
  then show "(a,b) ∈  edges f12" apply (drule_tac split_face_edges_or) by auto
qed


subsection {* @{text verticesFrom} *}

constdefs verticesFrom :: "face => vertex => vertex list"
 "verticesFrom f ≡ rotate_to (vertices f)"

lemmas verticesFrom_Def = verticesFrom_def rotate_to_def

lemma len_vFrom[simp]:
 "v ∈ \<V> f ==> |verticesFrom f v| = |vertices f|"
apply(drule split_list_first)
apply(clarsimp simp: verticesFrom_Def)
done

lemma verticesFrom_empty[simp]:
 "v ∈ \<V> f ==> (verticesFrom f v = []) = (vertices f = [])"
by(clarsimp simp: verticesFrom_Def)

lemma verticesFrom_congs:
 "v ∈ \<V> f ==> (vertices f) ≅ (verticesFrom f v)"
by(simp add:verticesFrom_def cong_rotate_to)

lemma verticesFrom_eq_if_vertices_cong:
  "[|distinct(vertices f); distinct(vertices f'); 
    vertices f ≅ vertices f'; x ∈ \<V> f |] ==>
   verticesFrom f x = verticesFrom f' x"
by(clarsimp simp:congs_def verticesFrom_Def splitAt_rotate_pair_conv)


lemma verticesFrom_in[intro]: "v ∈ \<V> f ==> a ∈ \<V> f ==> a ∈ set (verticesFrom f v)"
by (auto dest: verticesFrom_congs congs_pres_nodes)

lemma verticesFrom_in': "a ∈ set (verticesFrom f v) ==> a ≠ v ==> a ∈ \<V> f"
  apply (cases "v ∈ \<V> f") apply (auto dest: verticesFrom_congs congs_pres_nodes)
  by (simp add: verticesFrom_Def)

lemma set_verticesFrom:
 "v ∈ \<V> f ==> set (verticesFrom f v) = \<V> f"
apply(auto)
apply (auto simp add: verticesFrom_Def)
done

lemma verticesFrom_hd: "hd (verticesFrom f v) = v" by (simp add: verticesFrom_Def)

lemma verticesFrom_distinct[simp]: "distinct (vertices f) ==> v ∈ \<V> f ==> distinct (verticesFrom f v)" apply (frule_tac verticesFrom_congs) by (auto simp: congs_distinct)

lemma verticesFrom_nextElem_eq:
 "distinct (vertices f) ==> v ∈ \<V> f ==> u ∈ \<V> f ==>
 nextElem (verticesFrom f v) (hd (verticesFrom f v)) u
 = nextElem (vertices f) (hd (vertices f)) u" apply (subgoal_tac "(verticesFrom f v) ≅ (vertices f)")
 apply (rule nextElem_congs_eq) apply (auto simp: verticesFrom_congs congs_pres_nodes) apply (rule congs_sym)
 by (simp add: verticesFrom_congs)

lemma nextElem_vFrom_suc1: "distinct (vertices f) ==> v ∈ \<V> f ==> i < length (vertices f) ==> last (verticesFrom f v) ≠ u ==> (verticesFrom f v)!i = u ==> f • u = (verticesFrom f v)!(Suc i)"
proof -
  assume dist: "distinct (vertices f)" and ith: "(verticesFrom f v)!i = u" and small_i: "i < length (vertices f)" and notlast: "last (verticesFrom f v) ≠ u" and v: "v ∈ \<V> f"
  hence eq: "(vertices f) ≅ (verticesFrom f v)" by (auto simp: verticesFrom_congs)
  from ith eq small_i have "u ∈ set (verticesFrom f v)" by (auto simp: congs_length)
  with eq have u: "u ∈ \<V> f" by (auto simp: congs_pres_nodes)
  def ls ≡ "verticesFrom f v"
  with dist ith have
    "ls!i = u" by auto
  have ind: "!! c i. i < length ls ==> distinct ls ==> last ls ≠ u ==> ls!i = u ==> u ∈ set ls ==>
     nextElem ls c u = ls ! Suc i"
  proof (induct ls)
    case Nil then show ?case by auto
  next
    case (Cons m ms)
    then show ?case
    proof (cases "m = u")
      case True with Cons have "u ∉ set ms" by auto
      with Cons True have i: "i = 0" apply (induct i) by auto
      with Cons show ?thesis  apply (simp split: split_if_asm) apply (cases ms) by simp_all
    next
      case False with Cons have a1: "u ∈ set ms" by auto
      then have ms: "ms ≠ []" by auto
      from False Cons have i: "0 < i" by auto
      def i' ≡ "i - 1"
      with i have i': "i = Suc i'" by auto
      with False Cons i' ms have "nextElem ms c u = ms ! Suc i'" apply (rule_tac Cons) by simp_all
      with False Cons i' ms show ?thesis by simp
    qed
  qed
  from eq dist ith ls_def small_i notlast v
  have "nextElem ls (hd ls) u = ls ! Suc i"
    apply (rule_tac ind) by (auto simp: congs_length)
  with dist u v ls_def show ?thesis by (simp add: nextVertex_def verticesFrom_nextElem_eq)
qed

lemma nextElem_vFrom_suc2: "distinct (vertices f) ==> last (verticesFrom f v) = u ==> v ∈ \<V> f ==> u ∈ \<V> f ==> f • u = hd (verticesFrom f v)"
proof -
  assume dist: "distinct (vertices f)" and last: "last (verticesFrom f v) = u"
    and v: "v ∈ \<V> f" and u: "u ∈ \<V> f"
  def ls ≡ "verticesFrom f v"
  have ind: "!! c. distinct ls ==> last ls = u ==> u ∈ set ls ==> nextElem ls c u = c"
  proof (induct ls)
    case Nil then show ?case by auto
  next
    case (Cons m ms)
    then show ?case
    proof (cases "m = u")
      case True with Cons have "ms = []"  apply (cases ms rule: rev_exhaust) by auto
      then show ?thesis by auto
    next
      case False with Cons have a1: "u ∈ set ms" by auto
      then have ms: "ms ≠ []" by auto

      with False Cons ms have "nextElem ms c u = c" apply (rule_tac Cons) by simp_all
      with False ms show ?thesis by simp
    qed
  qed
  from dist ls_def last v u have "nextElem ls (hd ls) u = hd ls" apply (rule_tac ind) by auto
  with dist u v ls_def show ?thesis by (simp add: nextVertex_def verticesFrom_nextElem_eq)
qed

lemma verticesFrom_nth: "distinct (vertices f) ==> d < length (vertices f) ==>
  v ∈ \<V> f ==> (verticesFrom f v)!d = fd • v"
proof (induct d)
  case 0 then show ?case by (simp add: verticesFrom_Def nextVertices_def)
next
  case (Suc n)
  then have dist2: "distinct (verticesFrom f v)"
     apply (frule_tac verticesFrom_congs) by (auto simp: congs_distinct)
  from Suc have in2: "v ∈ set (verticesFrom f v)"
     apply (frule_tac verticesFrom_congs) by (auto dest: congs_pres_nodes)
  then have vFrom: "(verticesFrom f v) = butlast (verticesFrom f v) @ [last (verticesFrom f v)]"
    apply (cases "(verticesFrom f v)" rule: rev_exhaust) by auto
  from Suc show ?case
  proof (cases "last (verticesFrom f v) = fn • v")
    case True with Suc have "verticesFrom f v ! n = fn • v" by (rule_tac Suc) auto
    with True have "last (verticesFrom f v) = verticesFrom f v ! n" by auto
    with Suc dist2 in2 have "Suc n = length (verticesFrom f v)"
      apply (rule_tac nth_last_Suc_n) by auto
    with Suc show ?thesis by auto
  next
    case False with Suc show ?thesis apply (simp add: nextVertices_def) apply (rule sym)
    apply (rule_tac nextElem_vFrom_suc1) by simp_all
  qed
qed


lemma verticesFrom_length: "distinct (vertices f) ==> v ∈ set (vertices f) ==>
  length (verticesFrom f v) = length (vertices f)"
by (auto intro: congs_length verticesFrom_congs)

lemma verticesFrom_between: "v' ∈ \<V> f ==> pre_between (vertices f) u v ==>
  between (vertices f) u v = between (verticesFrom f v') u v"
by (auto intro!: between_congs verticesFrom_congs)


lemma verticesFrom_is_nextElem: "v ∈ \<V> f ==>
   is_nextElem (vertices f) a b = is_nextElem (verticesFrom f v) a b"
    apply (rule is_nextElem_congs_eq) by (rule verticesFrom_congs)

lemma verticesFrom_is_nextElem_last: "v' ∈ \<V> f ==> distinct (vertices f)
  ==> is_nextElem (verticesFrom f v') (last (verticesFrom f v')) v  ==> v = v'"
apply (subgoal_tac "distinct (verticesFrom f v')")
apply (subgoal_tac "last (verticesFrom f v') ∈ set (verticesFrom f v')")
apply (simp add: nextElem_is_nextElem)
apply (simp add: verticesFrom_hd)
apply (cases "(verticesFrom f v')" rule: rev_exhaust) apply (simp add: verticesFrom_Def)
by auto

lemma  verticesFrom_is_nextElem_hd: "v' ∈ \<V> f ==> distinct (vertices f)
  ==> is_nextElem (verticesFrom f v') u v' ==> u = last (verticesFrom f v')"
apply (subgoal_tac "distinct (verticesFrom f v')")
apply (thin_tac "distinct (vertices f)") apply (auto simp: is_nextElem_def)
apply (drule is_sublist_y_hd) apply (simp add: verticesFrom_hd)
by auto

lemma verticesFrom_pres_nodes1: "v ∈ \<V> f ==> \<V> f = set(verticesFrom f v)"
proof -
  assume "v ∈ \<V> f"
  then have "fst (splitAt v (vertices f)) @ [v] @ snd (splitAt v (vertices f)) = vertices f"
    apply (drule_tac splitAt_ram) by simp
  moreover have "set (fst (splitAt v (vertices f)) @ [v] @ snd (splitAt v (vertices f))) = set (verticesFrom f v)"
    by (auto simp: verticesFrom_Def)
  ultimately show ?thesis by simp
qed

lemma verticesFrom_pres_nodes: "v ∈ \<V> f ==> w ∈ \<V> f ==> w ∈ set (verticesFrom f v)"
by (auto dest: verticesFrom_pres_nodes1)


lemma before_verticesFrom: "distinct (vertices f) ==> v ∈ \<V> f ==> w ∈ \<V> f ==>
  v ≠ w ==> before (verticesFrom f v) v w"
proof -
  assume v: "v ∈ \<V> f" and w: "w ∈ \<V> f" and neq: "v ≠ w"
  have "hd (verticesFrom f v) = v" by (rule verticesFrom_hd)
  with v have vf:"verticesFrom f v = v # tl (verticesFrom f v)"
    apply (frule_tac verticesFrom_pres_nodes1)
    apply (cases "verticesFrom f v") by auto
  moreover with v w have "w ∈ set (verticesFrom f v)" by (auto simp: verticesFrom_pres_nodes)
  ultimately have "w ∈ set (v # tl (verticesFrom f v))" by auto
  with neq have "w ∈ set (tl (verticesFrom f v))" by auto
  with vf have "verticesFrom f v =
    [] @ v # fst (splitAt w (tl (verticesFrom f v))) @ w # snd (splitAt w (tl (verticesFrom f v)))"
    by (auto dest: splitAt_ram)
  then show ?thesis apply (unfold before_def) by (intro exI)
qed

lemma next_not_before:
 "[| distinct(vertices f); x ∈ \<V> f; y ∈ \<V> f; x ≠ f • y |] ==>
  ¬ before (verticesFrom f x) (f • y) y"
apply(drule split_list)
apply(clarsimp)
apply(clarsimp simp:before_def verticesFrom_Def)
apply(erule disjE)
 apply(clarsimp simp:Cons_eq_append_conv append_eq_append_conv2)
 apply(erule disjE)
  apply(clarsimp simp:append_eq_Cons_conv)
  apply(erule disjE)
   apply clarsimp
  apply(clarsimp simp:append_eq_append_conv2)
  apply(fastsimp simp:append_eq_Cons_conv)
 apply clarsimp
apply(erule disjE)
 apply(drule split_list)
 apply(clarsimp simp:nextVertex_def Cons_eq_append_conv split:list.splits)
 apply(clarsimp simp:append_eq_append_conv2)
 apply(erule disjE)
  apply(fastsimp simp:append_eq_Cons_conv)
 apply clarsimp
 apply(erule disjE)
  apply(clarsimp simp:append_eq_Cons_conv)
 apply(fastsimp simp:Cons_eq_append_conv)
apply(drule split_list)
apply(clarsimp simp:nextVertex_def split:list.splits)
 apply(clarsimp simp:hd_append split: split_if_asm)
 apply(clarsimp simp:Cons_eq_append_conv)
 apply(clarsimp simp:append_eq_append_conv2)
 apply(erule disjE)
  apply(fastsimp simp:append_eq_Cons_conv)
 apply(fastsimp simp:Cons_eq_append_conv neq_Nil_conv)
apply(clarsimp simp:Cons_eq_append_conv)
apply(clarsimp simp:append_eq_append_conv2)
apply(erule disjE)
 apply(clarsimp simp:append_eq_Cons_conv)
apply(clarsimp simp:Cons_eq_append_conv)
apply(erule disjE)
 apply(clarsimp simp:append_eq_append_conv2)
 apply(erule disjE)
  apply(fastsimp simp:append_eq_Cons_conv)
 apply clarsimp
apply(clarsimp simp:append_eq_append_conv2)
apply(fastsimp simp:append_eq_Cons_conv)
done

lemma last_vFrom:
 "[| distinct(vertices f); x ∈ \<V> f |] ==> last(verticesFrom f x) = f-1 • x"
apply(frule split_list)
apply(clarsimp simp:prevVertex_def verticesFrom_Def split:list.split)
done


ML"fast_arith_neq_limit := 1"
lemma rotate_before_vFrom:
  "[| distinct(vertices f); r ∈ \<V> f; r≠u |] ==>
   before (verticesFrom f r) u v ==> before (verticesFrom f v) r u"
apply(frule split_list)
apply(clarsimp simp:verticesFrom_Def)
apply(rename_tac as bs)
apply(clarsimp simp:before_def)
apply(rename_tac xs ys zs)
apply(subst (asm) Cons_eq_append_conv)
apply clarsimp
apply(rename_tac bs')
apply(subst (asm) append_eq_append_conv2)
apply clarsimp
apply(rename_tac as')
apply(erule disjE)
 defer
 apply clarsimp
 apply(rule_tac x = "v#zs" in exI)
 apply(rule_tac x = "bs@as'" in exI)
 apply simp
apply clarsimp
apply(subst (asm) append_eq_Cons_conv)
apply(erule disjE)
apply clarsimp
apply(rule_tac x = "v#zs" in exI)
apply simp apply blast
apply clarsimp
apply(rename_tac ys')
apply(subst (asm) append_eq_append_conv2)
apply clarsimp
apply(rename_tac vs')
apply(erule disjE)
 apply clarsimp
 apply(subst (asm) append_eq_Cons_conv)
 apply(erule disjE)
  apply clarsimp
  apply(rule_tac x = "v#zs" in exI)
  apply simp apply blast
 apply clarsimp
 apply(rule_tac x = "v#ys'@as" in exI)
 apply simp apply blast
apply clarsimp
apply(rule_tac x = "v#zs" in exI)
apply simp apply blast
done

lemma before_between:
 "[| before(verticesFrom f x) y z; distinct(vertices f); x ∈ \<V> f; x ≠ y |] ==>
  y ∈ set(between (vertices f) x z)"
apply(induct f)
apply(clarsimp simp:verticesFrom_Def before_def)
apply(frule split_list)
apply(clarsimp simp:Cons_eq_append_conv)
apply(subst (asm) append_eq_append_conv2)
apply clarsimp
apply(erule disjE)
 apply(clarsimp simp:append_eq_Cons_conv)
 prefer 2 apply(clarsimp simp add:between_def split_def)
apply(erule disjE)
 apply (clarsimp simp:between_def split_def)
apply clarsimp
apply(subst (asm) append_eq_append_conv2)
apply clarsimp
apply(erule disjE)
 prefer 2 apply(clarsimp simp add:between_def split_def)
apply(clarsimp simp:append_eq_Cons_conv)
apply(fastsimp simp:between_def split_def)
done
ML"fast_arith_neq_limit := 3"

lemma before_between2:
 "[| before (verticesFrom f u) v w; distinct(vertices f); u ∈ \<V> f |]
  ==> u = v ∨ u ∈ set (between (vertices f) w v)"
apply(subgoal_tac "pre_between (vertices f) v w")
 apply(subst verticesFrom_between)
   apply assumption
  apply(erule pre_between_symI)
 apply(frule pre_between_r1)
 apply(drule (1) verticesFrom_distinct)
 using verticesFrom_hd[of f u]
 apply(clarsimp simp add:before_def between_def split_def hd_append
                split:split_if_asm)
apply(frule (1) verticesFrom_distinct)
apply(clarsimp simp:pre_between_def before_def simp del:verticesFrom_distinct)
apply(rule conjI)
 apply(cases "v = u")
  apply simp
 apply(rule verticesFrom_in'[of v f u])apply simp apply assumption
apply(cases "w = u")
 apply simp
apply(rule verticesFrom_in'[of w f u])apply simp apply assumption
done


(************************** splitFace ********************************)


subsection {* @{const splitFace} *}


constdefs pre_splitFace :: "graph => vertex => vertex => face => vertex list => bool"
  "pre_splitFace g ram1 ram2 oldF nvs ≡
  oldF ∈ \<F> g ∧ ¬ final oldF ∧ distinct (vertices oldF) ∧ distinct nvs
  ∧ \<V> g ∩ set nvs = {}
  ∧ \<V> oldF ∩ set nvs = {}
  ∧ ram1 ∈ \<V> oldF ∧ ram2 ∈ \<V> oldF
  ∧ ram1 ≠ ram2
  ∧ (((ram1,ram2) ∉ edges oldF ∧ (ram2,ram1) ∉ edges oldF
     ∧ (ram1, ram2) ∉ edges g ∧ (ram2, ram1) ∉ edges g) ∨ nvs ≠ [])"

declare pre_splitFace_def [simp]

lemma pre_splitFace_pre_split_face[simp]:
  "pre_splitFace g ram1 ram2 oldF nvs ==> pre_split_face oldF ram1 ram2 nvs"
 by (simp add: pre_splitFace_def pre_split_face_def)

lemma pre_splitFace_oldF[simp]:
  "pre_splitFace g ram1 ram2 oldF nvs ==> oldF ∈ \<F> g"
  apply (unfold pre_splitFace_def) by force

declare pre_splitFace_def [simp del]

lemma p_splitFace_ne:
  "pre_splitFace g ram1 ram2 oldF nvs ==> (ram1, ram2) ∈ edges oldF ==> nvs ≠ []"
  apply (unfold pre_splitFace_def) by force


lemma splitFace_preserve_face_not_empty:
  "f ∉ \<F> g  ==>  vertices f' = vs ==> ram2 ∈ set vs ==>
   f ∈ \<F> (snd (snd (splitFace g ram1 ram2 f' ns))) ==> vertices f ≠ []"
proof (induct g)
  assume r2: "ram2 ∈ set vs"
  then have vs: "vs ≠ []" by auto
  def x ≡  "hd vs"
  def xs ≡ "tl vs"
  with x_def xs_def vs have vs_eq: "vs = x # xs" by simp
  note vs_eq_sym = vs_eq [symmetric]

  case (Graph fs n Fs hs) then  show ?thesis apply (case_tac "f = Face (rev ns @ ram1 # between vs ram1 ram2 @ [ram2]) Nonfinal")
    apply (simp add: Graph r2 splitFace_def split_face_def split_def)
    apply (simp add: splitFace_def split_face_def split_def)
    apply (drule_tac replace1) by (auto simp: vs_eq_sym)
qed

lemma splitFace_preserve_faces:
  " f ∈ \<F> g ==> f ≠ oldF ==>
   f ∈ \<F> (snd (snd (splitFace g ram1 ram2 oldF nvs)))"
apply (induct g)
by (auto intro: replace4 simp: splitFace_def split_def split_face_def)

lemma splitFace_split_face:
     "oldF ∈ \<F> g ==>
     (f1, f2, newGraph) = splitFace g ram1 ram2 oldF newVs ==>
     (f1, f2) = split_face oldF ram1 ram2 newVs"
  by (simp add: splitFace_def split_def)


lemma splitFace_add_f21:
"(f12, f21, g') = splitFace g ram1 ram2 oldF newVertexList ==> oldF ∈ \<F> g
 ==> f21 ∈ \<F> g'"
  by (auto simp add: splitFace_def split_def)

(* split_face *)
lemma split_face_empty_ram2_ram1_in_f12:
  "pre_split_face oldF ram1 ram2 [] ==>
  (f12, f21) = split_face oldF ram1 ram2 [] ==> (ram2, ram1) ∈ edges f12"
proof -
  assume split: "(f12, f21) = split_face oldF ram1 ram2 []"
  "pre_split_face oldF ram1 ram2 []"
  then have "ram2 ∈ \<V> f12" by (simp add: split_face_def)
  moreover with split have "f12 • ram2 = hd (vertices f12)"
   apply (rule_tac nextElem_suc2)
   apply (simp add: pre_split_face_def split_face_distinct1)
   by (simp add: split_face_def)
  with split have "ram1 = f12 • ram2"
   by (simp add: split_face_def)
  ultimately show ?thesis by (simp add: edges_face_def)
qed

lemma split_face_empty_ram2_ram1_in_f12':
  "pre_split_face oldF ram1 ram2 [] ==>
  (ram2, ram1) ∈ edges (fst (split_face oldF ram1 ram2 []))"
proof -
  assume split: "pre_split_face oldF ram1 ram2 []"
  def f12 ≡ "fst (split_face oldF ram1 ram2 [])"
  def f21 ≡ "snd (split_face oldF ram1 ram2 [])"
  then have "(f12, f21) = split_face oldF ram1 ram2 []" by (simp add: f12_def f21_def)
  with split have "(ram2, ram1) ∈ edges f12"
    by (rule split_face_empty_ram2_ram1_in_f12)
  with f12_def show ?thesis by simp
qed

lemma splitFace_empty_ram2_ram1_in_f12:
  "pre_splitFace g ram1 ram2 oldF [] ==>
  (f12, f21, newGraph) = splitFace g ram1 ram2 oldF [] ==>
  (ram2, ram1) ∈ edges f12"
proof -
  assume pre: "pre_splitFace g ram1 ram2 oldF []"
  then have oldF: "oldF ∈ \<F> g" by (unfold pre_splitFace_def) simp
  assume sp: "(f12, f21, newGraph) = splitFace g ram1 ram2 oldF []"
  with oldF have "(f12, f21) = split_face oldF ram1 ram2 []"
    by (rule splitFace_split_face)

  with pre sp show ?thesis
  apply (unfold  splitFace_def pre_splitFace_def)
  apply (simp add: split_def)
  apply (rule split_face_empty_ram2_ram1_in_f12')
  by (rule pre_splitFace_pre_split_face)
qed

lemma splitFace_f12_new_vertices:
  "(f12, f21, newGraph) = splitFace g ram1 ram2 oldF newVs ==>
  v ∈ set  newVs ==> v ∈ \<V> f12"
  apply (unfold splitFace_def)
  apply (simp add: split_def)
  apply (unfold split_face_def Let_def)
  by simp


lemma splitFace_add_vertices:
  "newVertexList = [countVertices g ..< countVertices g + n]
  ==> (f12, f21, newGraph) = splitFace g ram1 ram2 oldF (rev newVertexList)
  ==> vertices newGraph = vertices g @ newVertexList"
  apply (auto simp: splitFace_def split_def) apply (cases g) apply simp apply auto
  apply (induct n) by auto

lemma splitFace_add_vertices_direct[simp]:
"vertices (snd (snd (splitFace g ram1 ram2 oldF [countVertices g ..< countVertices g + n])))
  = vertices g @ [countVertices g ..< countVertices g + n]"
  apply (auto simp: splitFace_def split_def) apply (cases g)
  apply auto  apply (induct n) by auto

lemma splitFace_delete_oldF:
" (f12, f21, newGraph) = splitFace g ram1 ram2 oldF newVertexList ==>
 oldF ≠ f12 ==> oldF ≠ f21 ==> distinct (faces g) ==>
 oldF ∉ \<F> newGraph"
by (simp add: splitFace_def split_def distinct_set_replace)

lemma splitFace_faces_1:
"(f12, f21, newGraph) = splitFace g ram1 ram2 oldF newVertexList ==>
oldF ∈ \<F> g ==>
set (faces newGraph) ∪ {oldF} = {f12, f21} ∪ set (faces g)"
(is "?oldF ==> ?C ==> ?A = ?B")
proof (intro equalityI subsetI)
  fix x
  assume "x ∈ ?A" and "?C" and "?oldF"
  then show "x ∈ ?B" apply (simp add: splitFace_def split_def) by (auto dest: replace1)
next
  fix x
  assume "x ∈ ?B" and "?C" and "?oldF"
  then show "x ∈ ?A" apply (simp add: splitFace_def split_def)
    apply (cases "x = oldF") apply simp_all
    apply (cases "x = f12")  apply simp_all
    apply (cases "x = f21")  by (auto intro: replace3 replace4)
qed


lemma splitFace_distinct1[intro]:"pre_splitFace g ram1 ram2 oldF newVertexList ==>
  distinct (vertices (fst (snd (splitFace g ram1 ram2 oldF newVertexList))))"
  apply (unfold  splitFace_def split_def)
  by (auto simp add: split_def)

lemma splitFace_distinct2[intro]:"pre_splitFace g ram1 ram2 oldF newVertexList ==>
  distinct (vertices (fst (splitFace g ram1 ram2 oldF newVertexList)))"
  apply (unfold  splitFace_def split_def)
  by (auto simp add: split_def)


lemma splitFace_add_f21': "f' ∈ \<F> g' ==> fst (snd (splitFace g' v a f' nvl))
           ∈ \<F> (snd (snd (splitFace g' v a f' nvl)))"
apply (simp add: splitFace_def split_def) apply (rule disjI2)
apply (rule replace3) by simp_all

lemma split_face_help[simp]: "Suc 0 < |vertices (fst (split_face f' v a nvl))|"
  by (simp add: split_face_def)

lemma split_face_help'[simp]: "Suc 0 < |vertices (snd (split_face f' v a nvl))|"
 by (simp add: split_face_def)

lemma splitFace_split: "f ∈ \<F> (snd (snd (splitFace g v a f' nvl))) ==>
  f ∈ \<F> g
  ∨  f = fst (splitFace g v a f' nvl)
  ∨  f = (fst (snd (splitFace g v a f' nvl)))"
 apply (simp add: splitFace_def split_def)
 apply safe by (frule replace5)  simp

lemma pre_FaceDiv_between1: "pre_splitFace g' ram1 ram2 f [] ==>
  ¬ between (vertices f) ram1 ram2 = []"
proof -
  assume pre_f: "pre_splitFace g' ram1 ram2 f []"
  then have pre_bet: "pre_between (vertices f) ram1 ram2" apply (unfold pre_splitFace_def)
    by (simp add: pre_between_def)
  then have pre_bet': "pre_between (verticesFrom f ram1) ram1 ram2"
    by (simp add: pre_between_def set_verticesFrom)
  from pre_f have dist': "distinct (verticesFrom f ram1)" apply (unfold pre_splitFace_def) by simp
  from pre_f have ram2: "ram2 ∈ \<V> f" apply (unfold pre_splitFace_def) by simp
  from pre_f have "¬ is_nextElem (vertices f) ram1 ram2" apply (unfold pre_splitFace_def) by auto
  with pre_f have "¬ is_nextElem (verticesFrom f ram1) ram1 ram2" apply (unfold pre_splitFace_def)
    by (simp add: verticesFrom_is_nextElem [symmetric])
  moreover
  from pre_f have "ram2 ∈ set (verticesFrom f ram1)" apply (unfold pre_splitFace_def) by auto
  moreover
  from pre_f have "ram2 ≠  ram1" apply (unfold pre_splitFace_def) by auto
  ultimately have ram2_not: "ram2 ≠  hd (snd (splitAt ram1 (vertices f)) @ fst (splitAt ram1 (vertices f)))"
    apply (simp add: is_nextElem_def verticesFrom_Def)
    apply (cases "snd (splitAt ram1 (vertices f)) @ fst (splitAt ram1 (vertices f))")
    apply simp apply simp
    apply (simp add: is_sublist_def) by auto


  from pre_f have before: "before (verticesFrom f ram1) ram1 ram2" apply (unfold pre_splitFace_def)
    apply safe apply (rule before_verticesFrom) by auto
  have "fst (splitAt ram2 (snd (splitAt ram1 (verticesFrom f ram1)))) = [] ==> False"
  proof -
    assume  "fst (splitAt ram2 (snd (splitAt ram1 (verticesFrom f ram1)))) = []"
    moreover
    from ram2 pre_f have "ram2 ∈ set (verticesFrom f ram1)"apply (unfold pre_splitFace_def)
      by auto
    with pre_f have "ram2 ∈ set (snd (splitAt ram1 (vertices f)) @ fst (splitAt ram1 (vertices f)))"
      apply (simp add: verticesFrom_Def)
      apply (unfold pre_splitFace_def)  by auto
    moreover
    note dist'
    ultimately  have "ram2 = hd (snd (splitAt ram1 (vertices f)) @ fst (splitAt ram1 (vertices f)))"
      apply (rule_tac ccontr)
      apply (cases "(snd (splitAt ram1 (vertices f)) @ fst (splitAt ram1 (vertices f)))")
      apply simp
      apply simp
      by (simp add: verticesFrom_Def del: distinct_append)
    with ram2_not show ?thesis by auto
  qed
  with before pre_bet' have  "between (verticesFrom f ram1) ram1 ram2 ≠  []" by auto
  with pre_f pre_bet show ?thesis apply (unfold pre_splitFace_def) apply safe
  by (simp add: verticesFrom_between)
qed

lemma pre_FaceDiv_between2: "pre_splitFace g' ram1 ram2 f [] ==>
  ¬ between (vertices f) ram2 ram1 = []"
proof -
  assume pre_f: "pre_splitFace g' ram1 ram2 f []"
  then have "pre_splitFace g' ram2 ram1 f []" apply (unfold pre_splitFace_def) by auto
  then show ?thesis by (rule pre_FaceDiv_between1)
qed


(********************** Edges *******************)

constdefs
 Edges :: "vertex list => (vertex × vertex) set"
"Edges vs ≡ {(a,b). is_sublist [a,b] vs}"

lemma Edges_Nil[simp]: "Edges [] = {}"
by(simp add:Edges_def is_sublist_def)

lemma Edges_rev:
 "Edges (rev (zs::vertex list)) = {(b,a). (a,b) ∈ Edges zs}"
  by (auto simp add: Edges_def is_sublist_rev)

lemma in_Edges_rev[simp]:
 "((a,b) : Edges (rev (zs::vertex list))) = ((b,a) ∈ Edges zs)"
by (simp add: Edges_rev)

lemma notinset_notinEdge1: "x ∉ set xs ==> (x,y) ∉ Edges xs"
by(unfold Edges_def)(blast intro:is_sublist_in)

lemma notinset_notinEdge2: "y ∉ set xs ==> (x,y) ∉ Edges xs"
by(unfold Edges_def)(blast intro:is_sublist_in1)

lemma in_Edges_in_set: "(x,y) : Edges vs ==> x ∈ set vs ∧ y ∈ set vs"
by(unfold Edges_def)(blast intro:is_sublist_in is_sublist_in1)


lemma edges_conv_Edges:
  "distinct(vertices(f::face)) ==> \<E> f =
   Edges (vertices f) ∪
  (if vertices f = [] then {} else {(last(vertices f), hd(vertices f))})"
by(induct f) (auto simp: Edges_def is_nextElem_def)


lemma edges_conv_Edges_if_cong:
 "[| vertices (f::face) ≅ vs; distinct vs; vs ≠ [] |] ==>
 \<E> f = Edges vs ∪ {(last vs,hd vs)}"
apply(frule congs_distinct)
apply(clarsimp simp: expand_set_eq is_nextElem_congs_eq)
using is_nextElem_edges_eq[of "Face vs Final",symmetric]
apply(simp del:is_nextElem_edges_eq)
apply(simp add:edges_conv_Edges)
done

lemma Edges_Cons: "Edges(x#xs) =
  (if xs = [] then {} else Edges xs ∪ {(x,hd xs)})"
apply(auto simp:Edges_def)
   apply(rule ccontr)
   apply(simp add:is_sublist_simp)
  apply(erule thin_rl)
  apply(erule contrapos_np)
  apply(clarsimp simp:is_sublist_def Cons_eq_append_conv)
  apply(rename_tac as bs)
  apply(erule disjE)
   apply simp
  apply(clarsimp)
  apply(rename_tac cs)
  apply(rule_tac x = cs in exI)
  apply(rule_tac x = bs in exI)
  apply(rule HOL.refl)
 apply(clarsimp simp:neq_Nil_conv)
 apply(subst is_sublist_rec)
 apply simp
apply(simp add:is_sublist_def)
apply(erule exE)+
apply(rename_tac as bs)
apply simp
apply(rule_tac x = "x#as" in exI)
apply(rule_tac x = bs in exI)
apply simp
done

lemma Edges_append: "Edges(xs @ ys) =
  (if xs = [] then Edges ys else
   if ys = [] then Edges xs else
   Edges xs ∪ Edges ys ∪ {(last xs, hd ys)})"
apply(induct xs)
 apply simp
apply (simp add:Edges_Cons)
apply blast
done


lemma Edges_rev_disj: "distinct xs ==> Edges(rev xs) ∩ Edges(xs) = {}"
apply(induct xs)
 apply simp
apply(auto simp:Edges_Cons Edges_append last_rev
      notinset_notinEdge1 notinset_notinEdge2)
done

lemma disj_sets_disj_Edges:
 "set xs ∩ set ys = {} ==> Edges xs ∩ Edges ys = {}"
by(unfold Edges_def)(blast intro:is_sublist_in is_sublist_in1)

lemma disj_sets_disj_Edges2:
 "set ys ∩ set xs = {} ==> Edges xs ∩ Edges ys = {}"
by(blast intro!:disj_sets_disj_Edges)


lemma finite_Edges[iff]: "finite(Edges xs)"
by(induct xs)(simp_all add:Edges_Cons)


lemma length_conv_card_Edges:
 "distinct xs ==> |xs| = (if |xs| = 0 then 0 else card (Edges xs) + 1)"
apply(induct xs)
 apply simp
apply(clarsimp simp:Edges_Cons notinset_notinEdge1)
done

lemma card_edges:
 "distinct(vertices(f::face)) ==> card(\<E> f) = |vertices f|"
apply(frule length_conv_card_Edges)
apply(simp add:edges_conv_Edges)
apply(clarsimp simp:Edges_Cons notinset_notinEdge2 card_insert_if neq_Nil_conv
  split:split_if_asm)
done


ML"fast_arith_neq_limit := 1"
lemma Edges_compl:
 "[| distinct vs; x ∈ set vs; y ∈ set vs; x ≠ y |] ==>
 Edges(x # between vs x y @ [y]) ∩ Edges(y # between vs y x @ [x]) = {}"
apply(subgoal_tac
 "!!xs (ys::vertex list). xs ≠ [] ==> set xs ∩ set ys = {} ==> hd xs ∉ set ys")
 prefer 2 apply(drule hd_in_set) apply(blast)
apply(frule split_list[of  x])
apply clarsimp
apply(erule disjE)
 apply(frule split_list[of y])
 apply(clarsimp simp add:between_def split_def)
 apply (clarsimp simp add:Edges_Cons Edges_append
    notinset_notinEdge1 notinset_notinEdge2
    disj_sets_disj_Edges disj_sets_disj_Edges2
    Int_Un_distrib Int_Un_distrib2)
 apply(fastsimp)
apply(frule split_list[of y])
apply(clarsimp simp add:between_def split_def)
apply (clarsimp simp add:Edges_Cons Edges_append notinset_notinEdge1
 notinset_notinEdge2 disj_sets_disj_Edges disj_sets_disj_Edges2
 Int_Un_distrib Int_Un_distrib2)
apply fastsimp
done

lemma Edges_disj:
 "[| distinct vs; x ∈ set vs; z ∈ set vs; x ≠ y; y ≠ z;
    y ∈ set(between vs x z) |] ==>
 Edges(x # between vs x y @ [y]) ∩ Edges(y # between vs y z @ [z]) = {}"
apply(subgoal_tac
 "!!xs (ys::vertex list). xs ≠ [] ==> set xs ∩ set ys = {} ==> hd xs ∉ set ys")
 prefer 2 apply(drule hd_in_set) apply(blast)
apply(frule split_list[of x])
apply clarsimp
apply(erule disjE)
 apply simp
 apply(drule inbetween_inset)
 apply(rule Edges_compl)
    apply simp
   apply simp
  apply simp
 apply simp
apply(erule disjE)
 apply(frule split_list[of z])
 apply(clarsimp simp add:between_def split_def)
 apply(erule disjE)
  apply(frule split_list[of y])
  apply clarsimp
  apply (clarsimp simp add:Edges_Cons Edges_append
    notinset_notinEdge1 notinset_notinEdge2
    disj_sets_disj_Edges disj_sets_disj_Edges2
    Int_Un_distrib Int_Un_distrib2)
  apply fastsimp
 apply(frule split_list[of y])
 apply clarsimp
 apply (clarsimp simp add:Edges_Cons Edges_append notinset_notinEdge1
 notinset_notinEdge2 disj_sets_disj_Edges disj_sets_disj_Edges2
 Int_Un_distrib Int_Un_distrib2)
 apply fastsimp
apply(frule split_list[of z])
apply(clarsimp simp add:between_def split_def)
apply(frule split_list[of y])
apply clarsimp
apply (clarsimp simp add:Edges_Cons Edges_append notinset_notinEdge1
 notinset_notinEdge2 disj_sets_disj_Edges disj_sets_disj_Edges2
 Int_Un_distrib Int_Un_distrib2)
apply fastsimp
done

lemma edges_conv_Un_Edges:
 "[| distinct(vertices(f::face)); x ∈ \<V> f; y ∈ \<V> f; x ≠ y |] ==>
  \<E> f = Edges(x # between (vertices f) x y @ [y]) ∪
           Edges(y # between (vertices f) y x @ [x])"
apply(simp add:edges_conv_Edges)
apply(rule conjI)
 apply clarsimp
apply clarsimp
apply(frule split_list[of  x])
apply clarsimp
apply(erule disjE)
 apply(frule split_list[of y])
 apply(clarsimp simp add:between_def split_def)
 apply (clarsimp simp add:Edges_Cons Edges_append
    notinset_notinEdge1 notinset_notinEdge2
    disj_sets_disj_Edges disj_sets_disj_Edges2
    Int_Un_distrib Int_Un_distrib2)
 apply(fastsimp)
apply(frule split_list[of y])
apply(clarsimp simp add:between_def split_def)
apply (clarsimp simp add:Edges_Cons Edges_append
    notinset_notinEdge1 notinset_notinEdge2
    disj_sets_disj_Edges disj_sets_disj_Edges2
    Int_Un_distrib Int_Un_distrib2)
apply(fastsimp)
done
ML"fast_arith_neq_limit := 3"


lemma Edges_between_edges:
  "[| (a,b) ∈ Edges (u # between (vertices(f::face)) u v @ [v]);
    pre_split_face f u v vs |] ==> (a,b) ∈ \<E> f"
apply(simp add:pre_split_face_def)
apply(induct f)
apply(simp add:edges_conv_Edges Edges_Cons)
apply clarify
apply(case_tac "between list u v = []")
 apply simp
 apply(drule (4) is_nextElem_between_empty')
 apply(simp add:Edges_def)
apply(subgoal_tac "pre_between list u v")
 prefer 2 apply (simp add:pre_between_def)
apply(subgoal_tac "pre_between list v u")
 prefer 2 apply (simp add:pre_between_def)
apply(case_tac "before list u v")
 apply(drule (1) between_eq2)
 apply clarsimp
 apply(erule disjE)
  apply (clarsimp simp:neq_Nil_conv)
  apply(rule is_nextElem_sublistI)
  apply(simp (no_asm) add:is_sublist_def)
  apply blast
 apply(rule is_nextElem_sublistI)
 apply(clarsimp simp add:Edges_def is_sublist_def)
 apply(rename_tac as bs cs xs ys)
 apply(rule_tac x = "as @ u # xs" in exI)
 apply(rule_tac x = "ys @ cs" in exI)
 apply simp
apply (simp only:before_xor)
apply(drule (1) between_eq2)
apply clarsimp
apply(rename_tac as bs cs)
apply(erule disjE)
 apply (clarsimp simp:neq_Nil_conv)
 apply(case_tac cs)
  apply clarsimp
  apply(simp add:is_nextElem_def)
 apply simp
 apply(rule is_nextElem_sublistI)
 apply(simp (no_asm) add:is_sublist_def)
 apply(rule_tac x = "as @ v # bs" in exI)
 apply simp
apply(rule_tac m = "|as|+1" in is_nextElem_rotate_eq[THEN iffD1,standard])
apply simp
apply(simp add:rotate_drop_take)
apply(rule is_nextElem_sublistI)
apply(clarsimp simp add:Edges_def is_sublist_def)
apply(rename_tac xs ys)
apply(rule_tac x = "bs @ u # xs" in exI)
apply simp
done


ML"fast_arith_neq_limit := 10"
lemma triangle_if_3circular:
 "[| distinct[a,b,c]; distinct(vertices(f::face));
    (a,b) ∈ \<E> f; (b,c) ∈ \<E> f; (c,a) ∈ \<E> f |]
  ==> \<E> f = {(a,b),(b,c),(c,a)}"
apply(rule card_seteq[OF finite_edges, symmetric])
 apply simp
apply(simp add:card_edges)
apply(rule ccontr)
apply(drule is_nextElem_nth1)+
apply clarsimp
apply(simp add:nth_eq_iff_index_eq)
apply(case_tac "Suc i = |vertices f|")
 apply(simp)
apply(case_tac "Suc(Suc i) = |vertices f|")
 apply(simp)
apply(case_tac "Suc(Suc(Suc i)) = |vertices f|")
 apply simp
apply simp
done
ML"fast_arith_neq_limit := 3"


(******************** split_face_edges ********************************)


(* split_face *)

lemma edges_split_face1: "pre_split_face f u v vs ==>
 \<E>(fst(split_face f u v vs)) =
 Edges(v # rev vs @ [u]) ∪ Edges(u # between (vertices f) u v @ [v])"
apply(simp add: edges_conv_Edges split_face_distinct1');
apply(auto simp add:split_face_def Edges_Cons Edges_append)
done

lemma edges_split_face2: "pre_split_face f u v vs ==>
 \<E>(snd(split_face f u v vs)) =
 Edges(u # vs @ [v]) ∪ Edges(v # between (vertices f) v u @ [u])"
apply(simp add: edges_conv_Edges split_face_distinct2');
apply(auto simp add:split_face_def Edges_Cons Edges_append)
done

lemma split_face_empty_ram1_ram2_in_f21:
  "pre_split_face oldF ram1 ram2 [] ==>
  (f12, f21) = split_face oldF ram1 ram2 [] ==> (ram1, ram2) ∈ edges f21"
proof -
  assume split: "(f12, f21) = split_face oldF ram1 ram2 []"
  "pre_split_face oldF ram1 ram2 []"
  then have "ram1 ∈ \<V> f21" by (simp add: split_face_def)
  moreover with split have "f21 • ram1 = hd (vertices f21)"
   apply (rule_tac nextElem_suc2)
   apply (simp add: pre_split_face_def split_face_distinct2)
   by (simp add: split_face_def)
  with split have "ram2 = f21 • ram1"
   by (simp add: split_face_def)
  ultimately show ?thesis by (simp add: edges_face_def)
qed

lemma split_face_empty_ram1_ram2_in_f21':
  "pre_split_face oldF ram1 ram2 [] ==>
  (ram1, ram2) ∈ edges (snd (split_face oldF ram1 ram2 []))"
proof -
  assume split: "pre_split_face oldF ram1 ram2 []"
  def f12 ≡ "fst (split_face oldF ram1 ram2 [])"
  def f21 ≡ "snd (split_face oldF ram1 ram2 [])"
  then have "(f12, f21) = split_face oldF ram1 ram2 []" by (simp add: f12_def f21_def)
  with split have "(ram1, ram2) ∈ edges f21"
    by (rule split_face_empty_ram1_ram2_in_f21)
  with f21_def show ?thesis by simp
qed

lemma splitFace_empty_ram1_ram2_in_f21:
  "pre_splitFace g ram1 ram2 oldF [] ==>
  (f12, f21, newGraph) = splitFace g ram1 ram2 oldF [] ==>
  (ram1, ram2) ∈ edges f21"
proof -
  assume pre: "pre_splitFace g ram1 ram2 oldF []"
  then have oldF: "oldF ∈ \<F> g" by (unfold pre_splitFace_def) simp
  assume sp: "(f12, f21, newGraph) = splitFace g ram1 ram2 oldF []"
  with oldF have "(f12, f21) = split_face oldF ram1 ram2 []"
    by (rule splitFace_split_face)

  with pre sp show ?thesis
  apply (unfold  splitFace_def pre_splitFace_def)
  apply (simp add: split_def)
  apply (rule split_face_empty_ram1_ram2_in_f21')
  by (rule pre_splitFace_pre_split_face)
qed

lemma splitFace_f21_new_vertices:
  "(f12, f21, newGraph) = splitFace g ram1 ram2 oldF newVs ==>
  v ∈ set  newVs ==> v ∈ \<V> f21"
  apply (unfold splitFace_def)
  apply (simp add: split_def)
  apply (unfold split_face_def)
  by simp

lemma split_face_f12_f21_neq:
  "pre_split_face oldF ram1 ram2 vs ==>
  (f12, f21) = split_face oldF ram1 ram2 vs ==> f12 ≠ f21"
proof -
  assume split: "(f12, f21) = split_face oldF ram1 ram2 vs"
  "pre_split_face oldF ram1 ram2 vs"
  then have "distinct (vertices f12)" by (rule split_face_distinct1)
  with split show ?thesis apply (simp add: split_face_def)
    apply (case_tac vs rule:rev_exhaust) apply (simp add: pre_split_face_def) by simp
qed


lemma split_face_edges_f12: "pre_split_face f ram1 ram2 vs ==>
  (f12, f21) = split_face f ram1 ram2 vs ==> vs ≠ [] ==> vs1 = between (vertices f) ram1 ram2 ==> vs1 ≠ [] ==>
  edges f12 = {(hd vs, ram1) , (ram1, hd vs1), (last vs1, ram2), (ram2, last vs)} ∪
  Edges(rev vs) ∪ Edges vs1" (concl is "?lhs = ?rhs")
proof (intro equalityI subsetI)
  fix x
  assume x: "x ∈ ?lhs" and vors: "pre_split_face f ram1 ram2 vs"
    "(f12, f21) = split_face f ram1 ram2 vs" "vs ≠ []"  "vs1 = between (vertices f) ram1 ram2 " "vs1 ≠ []"
  def c ≡ "fst x"
  def d ≡ "snd x"
  with c_def  have [simp]: "x = (c,d)" by simp
  from vors have dist_f12: "distinct (vertices f12)" apply (rule_tac split_face_distinct1) by auto
  from x vors show "x ∈ ?rhs"
    apply (simp add: split_face_def is_nextElem_def is_sublist_def dist_f12)
    apply (case_tac "c = ram2 ∧ d = last vs") apply simp apply simp apply (elim exE)
    apply (case_tac "c = ram1") apply simp
     apply (subgoal_tac "between (vertices f) ram1 ram2 @ [ram2] = d # bs")
      apply (case_tac "between (vertices f) ram1 ram2") apply simp apply simp
     apply (rule dist_at2) apply (rule dist_f12) apply (rule sym) apply simp  apply simp
    (* c ≠ ram1 *)
    apply (case_tac "c ∈ set(rev vs)")
     apply (subgoal_tac "distinct(rev vs)") apply (simp only: in_set_conv_decomp) apply (elim exE) apply simp
      apply (case_tac "zs") apply simp
       apply (subgoal_tac "ys = as") apply(drule last_rev) apply (simp)
       apply (rule dist_at1) apply (rule dist_f12) apply (rule sym) apply simp
       apply simp
      apply (simp add:rev_swap)
      apply (subgoal_tac "ys = as")
       apply (clarsimp simp add: Edges_def is_sublist_def)
       apply (rule conjI)
        apply (subgoal_tac "∃as bs. rev list @ [d, c] = as @ d # c # bs") apply simp apply (intro exI) apply simp
       apply (subgoal_tac "∃asa bs. rev list @ d # c # rev as = asa @ d # c # bs") apply simp  apply (intro exI) apply simp
      apply (rule dist_at1) apply (rule dist_f12) apply (rule sym) apply simp apply simp
    apply (simp add: pre_split_face_def)
    (* c ∉ set vs *)
    apply (case_tac "c ∈ set (between (vertices f) ram1 ram2)")
     apply (subgoal_tac "distinct (between (vertices f) ram1 ram2)") apply (simp add: in_set_conv_decomp) apply (elim exE) apply simp
      apply (case_tac zs) apply simp apply (subgoal_tac "rev vs @ ram1 # ys = as") apply force
       apply (rule dist_at1) apply (rule dist_f12) apply (rule sym) apply simp apply simp
      apply simp
      apply (subgoal_tac "rev vs @ ram1 # ys = as") apply (simp add: Edges_def is_sublist_def)
       apply (subgoal_tac "(rev vs @ ram1 # ys) @ c # a # list @ [ram2] = as @ c # d # bs") apply simp
        apply (rule conjI) apply (rule impI) apply (rule disjI2)+ apply (rule exI) apply force
        apply (rule impI) apply (rule disjI2)+ apply force
       apply force
      apply (rule dist_at1) apply (rule dist_f12) apply (rule sym) apply simp apply simp
     apply (thin_tac "rev vs @ ram1 # between (vertices f) ram1 ram2 @ [ram2] = as @ c # d # bs")
     apply (subgoal_tac "distinct (vertices f12)") apply simp
     apply (rule dist_f12)
      (* c ∉  set (between (vertices f) ram1 ram2) *)
    apply (subgoal_tac "c = ram2") apply simp
     apply (subgoal_tac "rev vs @ ram1 # between (vertices f) ram1 ram2 = as") apply force
     apply (rule dist_at1) apply (rule dist_f12) apply (rule sym)  apply simp apply simp

    (* c ≠ ram2 *)
    apply (subgoal_tac "c ∈ set (rev vs @ ram1 # between (vertices f) ram1 ram2 @ [ram2])")
     apply (thin_tac "rev vs @ ram1 # between (vertices f) ram1 ram2 @ [ram2] = as @ c # d # bs") apply simp
    by simp
next
  fix x
  assume x: "x ∈ ?rhs" and vors: "pre_split_face f ram1 ram2 vs"
    "(f12, f21) = split_face f ram1 ram2 vs" "vs ≠ []"  "vs1 = between (vertices f) ram1 ram2 " "vs1 ≠ []"
  def c ≡ "fst x"
  def d ≡ "snd x"
  with c_def  have [simp]: "x = (c,d)" by simp
  from vors have dist_f12: "distinct (vertices f12)" apply (rule_tac split_face_distinct1) by auto
  from x vors show "x ∈ ?lhs"
    apply (simp add: dist_f12 is_nextElem_def is_sublist_def) apply (simp add: split_face_def)
    apply (case_tac "c = ram2 ∧ d = last vs") apply simp
    apply (rule disjCI) apply simp
    apply (case_tac "c = hd vs ∧ d = ram1")
     apply (case_tac "vs") apply simp
     apply force
    apply simp
    apply (case_tac "c = ram1 ∧ d = hd (between (vertices f) ram1 ram2)")
     apply (case_tac "between (vertices f) ram1 ram2") apply simp apply force
    apply simp
    apply (case_tac "c = last (between (vertices f) ram1 ram2) ∧ d = ram2")
     apply (case_tac "between (vertices f) ram1 ram2" rule: rev_exhaust) apply simp
     apply simp
     apply (intro exI) apply (subgoal_tac "rev vs @ ram1 # ys @ [y, ram2] = (rev vs @ ram1 # ys) @ y # ram2 # []")
      apply assumption
     apply simp
    apply simp
    apply (case_tac "(d,c) ∈ Edges vs") apply (simp add: Edges_def is_sublist_def)
     apply (elim exE) apply simp apply (intro exI) apply simp
    apply (simp add: Edges_def is_sublist_def)
    apply (elim exE) apply simp apply (intro exI)
    apply (subgoal_tac "rev vs @ ram1 # as @ c # d # bs @ [ram2] = (rev vs @ ram1 # as) @ c # d # bs @ [ram2]")
     apply assumption
    by simp
qed

lemma split_face_edges_f12_vs: "pre_split_face f ram1 ram2 [] ==>
  (f12, f21) = split_face f ram1 ram2 [] ==> vs1 = between (vertices f) ram1 ram2 ==> vs1 ≠ [] ==>
  edges f12 = {(ram2, ram1) , (ram1, hd vs1), (last vs1, ram2)} ∪
  Edges vs1" (concl is "?lhs = ?rhs")
proof (intro equalityI subsetI)
  fix x
  assume x: "x ∈ ?lhs" and vors: "pre_split_face f ram1 ram2 []"
    "(f12, f21) = split_face f ram1 ram2 []"  "vs1 = between (vertices f) ram1 ram2 " "vs1 ≠ []"
  def c ≡ "fst x"
  def d ≡ "snd x"
  with c_def  have [simp]: "x = (c,d)" by simp
  from vors have dist_f12: "distinct (vertices f12)" apply (rule_tac split_face_distinct1) by auto
  from x vors show "x ∈ ?rhs"
    apply (simp add: split_face_def is_nextElem_def is_sublist_def dist_f12)
    apply (case_tac " c = ram2 ∧ d = ram1") apply simp
    apply simp apply (elim exE)
    apply (case_tac "c = ram1") apply simp
     apply (subgoal_tac "as = []") apply simp
      apply (case_tac "between (vertices f) ram1 ram2") apply simp
      apply simp
     apply (rule dist_at1) apply (rule dist_f12) apply force apply (rule sym) apply simp
    (* a ≠ ram1 *)
    apply (case_tac "c ∈ set (between (vertices f) ram1 ram2)")
     apply (subgoal_tac "distinct (between (vertices f) ram1 ram2)") apply (simp add: in_set_conv_decomp) apply (elim exE) apply simp
      apply (case_tac zs) apply simp apply (subgoal_tac "ram1 # ys = as") apply force
       apply (rule dist_at1) apply (rule dist_f12) apply (rule sym) apply simp apply simp
      apply simp
      apply (subgoal_tac "ram1 # ys = as") apply (simp add: Edges_def is_sublist_def)
       apply (subgoal_tac "(ram1 # ys) @ c # a # list @ [ram2] = as @ c # d # bs") apply simp
        apply (rule conjI) apply (rule impI) apply (rule disjI2)+ apply (rule exI) apply force
        apply (rule impI) apply (rule disjI2)+ apply force
       apply force
      apply (rule dist_at1) apply (rule dist_f12) apply (rule sym) apply simp apply simp
     apply (thin_tac "ram1 # between (vertices f) ram1 ram2 @ [ram2] = as @ c # d # bs")
     apply (subgoal_tac "distinct (vertices f12)") apply simp
     apply (rule dist_f12)
      (* c ∉  set (between (vertices f) ram1 ram2) *)
    apply (subgoal_tac "c = ram2") apply simp
     apply (subgoal_tac "ram1 # between (vertices f) ram1 ram2 = as") apply force
     apply (rule dist_at1) apply (rule dist_f12) apply (rule sym)  apply simp apply simp

    (* c ≠ ram2 *)
    apply (subgoal_tac "c ∈ set (ram1 # between (vertices f) ram1 ram2 @ [ram2])")
     apply (thin_tac "ram1 # between (vertices f) ram1 ram2 @ [ram2] = as @ c # d # bs") apply simp
    by simp
next
  fix x
  assume x: "x ∈ ?rhs" and vors: "pre_split_face f ram1 ram2 []"
    "(f12, f21) = split_face f ram1 ram2 []" "vs1 = between (vertices f) ram1 ram2 " "vs1 ≠ []"
  def c ≡ "fst x"
  def d ≡ "snd x"
  with c_def  have [simp]: "x = (c,d)" by simp
  from vors have dist_f12: "distinct (vertices f12)" apply (rule_tac split_face_distinct1) by auto
  from x vors show "x ∈ ?lhs"
    apply (simp add: dist_f12 is_nextElem_def is_sublist_def) apply (simp add: split_face_def)
    apply (case_tac "c = ram2 ∧ d = ram1") apply simp
    apply (rule disjCI) apply simp
    apply (case_tac "c = ram1 ∧ d = hd (between (vertices f) ram1 ram2)")
     apply (case_tac "between (vertices f) ram1 ram2") apply simp
     apply force
    apply simp
    apply (case_tac "c = last (between (vertices f) ram1 ram2) ∧ d = ram2")
     apply (case_tac "between (vertices f) ram1 ram2" rule: rev_exhaust) apply simp
     apply simp
     apply (intro exI) apply (subgoal_tac "ram1 # ys @ [y, ram2] = (ram1 # ys) @ y # ram2 # []")
      apply assumption
     apply simp
    apply simp
    apply (case_tac "(c, d) ∈ Edges vs") apply (simp add: Edges_def is_sublist_def)
     apply (elim exE) apply simp apply (intro exI)
     apply (subgoal_tac "ram1 # as @ c # d # bs @ [ram2] = (ram1 # as) @ c # d # (bs @ [ram2])") apply assumption
     apply simp
    apply (simp add: Edges_def is_sublist_def)
    apply (elim exE) apply simp apply (intro exI)
    apply (subgoal_tac "ram1 # as @ c # d # bs @ [ram2] = (ram1 # as) @ c # d # bs @ [ram2]")
     apply assumption
    by simp
qed

lemma split_face_edges_f12_bet: "pre_split_face f ram1 ram2 vs ==>
  (f12, f21) = split_face f ram1 ram2 vs ==> vs ≠ [] ==> between (vertices f) ram1 ram2 = [] ==>
  edges f12 = {(hd vs, ram1) , (ram1, ram2), (ram2, last vs)} ∪
  Edges(rev vs)" (concl is "?lhs = ?rhs")
proof (intro equalityI subsetI)
  fix x
  assume x: "x ∈ ?lhs" and vors: "pre_split_face f ram1 ram2 vs"
    "(f12, f21) = split_face f ram1 ram2 vs" "vs ≠ []"  "between (vertices f) ram1 ram2 = []"
  def c ≡ "fst x"
  def d ≡ "snd x"
  with c_def  have [simp]: "x = (c,d)" by simp
  from vors have dist_f12: "distinct (vertices f12)" apply (rule_tac split_face_distinct1) by auto
  from x vors show "x ∈ ?rhs"
    apply (simp add: split_face_def is_nextElem_def is_sublist_def dist_f12)
    apply (case_tac " c = ram2 ∧ d = last vs") apply simp
    apply simp apply (elim exE)
    apply (case_tac "c = ram1") apply simp
     apply (subgoal_tac "rev vs = as") apply simp
     apply (rule dist_at1) apply (rule dist_f12) apply (rule sym) apply simp  apply simp
    (* a ≠ ram1 *)
    apply (case_tac "c ∈ set(rev vs)")
     apply (subgoal_tac "distinct(rev vs)") apply (simp only: in_set_conv_decomp) apply (elim exE) apply simp
      apply (case_tac "zs") apply simp apply (subgoal_tac "ys = as") apply (simp add:rev_swap)
       apply (rule dist_at1) apply (rule dist_f12) apply (rule sym) apply simp apply simp apply simp
      apply (subgoal_tac "ys = as") apply (simp add: Edges_def is_sublist_def rev_swap)
       apply (rule conjI)
        apply (subgoal_tac "∃as bs. rev list @ [d, c] = as @ d # c # bs") apply simp apply (intro exI) apply simp
       apply (subgoal_tac "∃asa bs. rev list @ d # c # rev as = asa @ d # c # bs") apply simp  apply (intro exI) apply simp
      apply (rule dist_at1) apply (rule dist_f12) apply (rule sym) apply simp apply simp
     apply (simp add: pre_split_face_def)
    (* c ∉ set vs *)
    apply (subgoal_tac "c = ram2") apply simp
     apply (subgoal_tac "rev vs @ [ram1] = as") apply force
     apply (rule dist_at1) apply (rule dist_f12) apply (rule sym)  apply simp apply simp

    (* c ≠ ram2 *)
    apply (subgoal_tac "c ∈ set (rev vs @ ram1 # [ram2])")
     apply (thin_tac "rev vs @ ram1 # [ram2] = as @ c # d # bs") apply simp
    by simp
next
  fix x
  assume x: "x ∈ ?rhs" and vors: "pre_split_face f ram1 ram2 vs"
    "(f12, f21) = split_face f ram1 ram2 vs" "vs ≠ []"  "between (vertices f) ram1 ram2 = []"
  def c ≡ "fst x"
  def d ≡ "snd x"
  with c_def  have [simp]: "x = (c,d)" by simp
  from vors have dist_f12: "distinct (vertices f12)" apply (rule_tac split_face_distinct1) by auto
  from x vors show "x ∈ ?lhs"
    apply (simp add: dist_f12 is_nextElem_def is_sublist_def) apply (simp add: split_face_def)
    apply (case_tac "c = hd vs ∧ d = ram1")
     apply (case_tac "vs") apply simp
     apply force
    apply simp
    apply (case_tac "c = ram1 ∧ d = ram2") apply force
    apply simp
    apply (case_tac "c = ram2 ∧ d = last vs")
     apply (case_tac "vs" rule:rev_exhaust) apply simp
     apply simp
    apply (simp add: Edges_def is_sublist_def)
    apply (elim exE) apply simp apply (rule conjI)
     apply (rule impI) apply (rule disjI1) apply (intro exI)
     apply (subgoal_tac "c # d # rev as @ [ram1, ram2] = [] @ c # d # rev as @ [ram1,ram2]") apply assumption apply simp
    apply (rule impI) apply (rule disjI1) apply (intro exI) by simp
qed

lemma split_face_edges_f12_bet_vs: "pre_split_face f ram1 ram2 [] ==>
  (f12, f21) = split_face f ram1 ram2 [] ==> between (vertices f) ram1 ram2 = [] ==>
  edges f12 = {(ram2, ram1) , (ram1, ram2)}" (concl is "?lhs = ?rhs")
proof (intro equalityI subsetI)
  fix x
  assume x: "x ∈ ?lhs" and vors: "pre_split_face f ram1 ram2 []"
    "(f12, f21) = split_face f ram1 ram2 []" "between (vertices f) ram1 ram2 = []"
  def c ≡ "fst x"
  def d ≡ "snd x"
  with c_def  have [simp]: "x = (c,d)" by simp
  from vors have dist_f12: "distinct (vertices f12)" apply (rule_tac split_face_distinct1) by auto
  from x vors show "x ∈ ?rhs"
    apply (simp add: split_face_def is_nextElem_def is_sublist_def dist_f12)
    apply (case_tac " c = ram2 ∧ d = ram1") apply force
    apply simp apply (elim exE)
    apply (case_tac "c = ram1")  apply simp
     apply (case_tac "as") apply simp
    apply (case_tac "list") apply simp apply simp
    apply (case_tac "as") apply simp apply (case_tac "list") apply simp by simp
next
  fix x
  assume x: "x ∈ ?rhs" and vors: "pre_split_face f ram1 ram2 []"
    "(f12, f21) = split_face f ram1 ram2 []"  "between (vertices f) ram1 ram2 = []"
  def c ≡ "fst x"
  def d ≡ "snd x"
  with c_def  have [simp]: "x = (c,d)" by simp
  from vors have dist_f12: "distinct (vertices f12)" apply (rule_tac split_face_distinct1) by auto
  from x vors show "x ∈ ?lhs"
    apply (simp add: dist_f12 is_nextElem_def is_sublist_def) apply (simp add: split_face_def)
    by auto
qed


lemma split_face_edges_f12_subset: "pre_split_face f ram1 ram2 vs ==>
  (f12, f21) = split_face f ram1 ram2 vs ==> vs ≠ [] ==>
  {(hd vs, ram1), (ram2, last vs)} ∪ Edges(rev vs) ⊆ edges f12"
  apply (case_tac "between (vertices f) ram1 ram2")
    apply (frule split_face_edges_f12_bet)  apply simp apply simp apply simp apply force
    apply (frule split_face_edges_f12) apply simp+ by force

(*declare in_Edges_rev [simp del] rev_eq_Cons_iff [simp del]*)

lemma split_face_edges_f21: "pre_split_face f ram1 ram2 vs ==>
  (f12, f21) = split_face f ram1 ram2 vs ==> vs ≠ [] ==> vs2 = between (vertices f) ram2 ram1 ==> vs2 ≠ [] ==>
  edges f21 = {(last vs2, ram1) , (ram1, hd vs), (last vs, ram2), (ram2, hd vs2)} ∪
  Edges vs ∪ Edges vs2" (concl is "?lhs = ?rhs")
proof (intro equalityI subsetI)
  fix x
  assume x: "x ∈ ?lhs" and vors: "pre_split_face f ram1 ram2 vs"
    "(f12, f21) = split_face f ram1 ram2 vs" "vs ≠ []"  "vs2 = between (vertices f) ram2 ram1 " "vs2 ≠ []"
  def c ≡ "fst x"
  def d ≡ "snd x"
  with c_def  have [simp]: "x = (c,d)" by simp
  from vors have dist_f21: "distinct (vertices f21)" apply (rule_tac split_face_distinct2) by auto
  from x vors show "x ∈ ?rhs"
    apply (simp add: split_face_def is_nextElem_def is_sublist_def dist_f21)
    apply (case_tac " c = last vs ∧ d = ram2") apply simp
    apply simp apply (elim exE)
    apply (case_tac "c = ram1") apply simp
     apply (subgoal_tac "ram2 # between (vertices f) ram2 ram1 = as")
      apply clarsimp
     apply (rule dist_at1) apply (rule dist_f21) apply (rule sym) apply simp apply simp
    (* a ≠ ram1 *)
    apply (case_tac "c ∈ set vs")
     apply (subgoal_tac "distinct vs")
      apply (simp add: in_set_conv_decomp) apply (elim exE) apply simp
      apply (case_tac "zs") apply simp
       apply (subgoal_tac "ram2 # between (vertices f) ram2 ram1 @ ram1 # ys = as") apply force
       apply (rule dist_at1) apply (rule dist_f21) apply (rule sym) apply simp apply simp
      apply simp
      apply (subgoal_tac "ram2 # between (vertices f) ram2 ram1 @ ram1 # ys = as")
       apply (subgoal_tac "(ram2 # between (vertices f) ram2 ram1 @ ram1 # ys) @ c # a # list = as @ c # d # bs")
        apply (thin_tac "ram2 # between (vertices f) ram2 ram1 @ ram1 # ys @ c # a # list = as @ c # d # bs")
        apply (simp add: Edges_def is_sublist_def)
        apply(rule conjI)
         apply (subgoal_tac "∃as bs. ys @ [c, d] = as @ c # d # bs") apply simp apply force
        apply force
       apply force
      apply (rule dist_at1) apply (rule dist_f21) apply (rule sym) apply simp apply simp
     apply (simp add: pre_split_face_def)
    (* c ∉ set (rev vs) *)
    apply (case_tac "c ∈ set (between (vertices f) ram2 ram1)")
     apply (subgoal_tac "distinct (between (vertices f) ram2 ram1)") apply (simp add: in_set_conv_decomp) apply (elim exE) apply simp
      apply (case_tac zs) apply simp apply (subgoal_tac "ram2 # ys = as") apply force
       apply (rule dist_at1) apply (rule dist_f21) apply (rule sym) apply simp apply simp
      apply simp
      apply (subgoal_tac "ram2 # ys = as") apply (simp add: Edges_def is_sublist_def)
       apply (subgoal_tac "(ram2 # ys) @ c # a # list @ ram1 # vs = as @ c # d # bs")
        apply (thin_tac "ram2 # ys @ c # a # list @ ram1 # vs = as @ c # d # bs")
        apply (rule conjI) apply (rule impI) apply (rule disjI2)+ apply force
        apply (rule impI) apply (rule disjI2)+ apply force
       apply force
      apply (rule dist_at1) apply (rule dist_f21) apply (rule sym) apply simp apply simp
     apply (subgoal_tac "distinct (vertices f21)")
     apply (thin_tac "ram2 # between (vertices f) ram2 ram1 @ ram1 # vs = as @ c # d # bs") apply simp
     apply (rule dist_f21)
      (* c ∉  set (between (vertices f) ram2 ram1) *)
    apply (subgoal_tac "c = ram2") apply simp
     apply (subgoal_tac "[] = as") apply simp apply (case_tac "between (vertices f) ram2 ram1") apply simp apply simp
     apply (rule dist_at1) apply (rule dist_f21) apply (rule sym)  apply simp apply simp

    (* c ≠ ram2 *)
    apply (subgoal_tac "c ∈ set (ram2 # between (vertices f) ram2 ram1 @ ram1 # vs)")
     apply (thin_tac "ram2 # between (vertices f) ram2 ram1 @ ram1 # vs = as @ c # d # bs") apply simp
    by simp
next
  fix x
  assume x: "x ∈ ?rhs" and vors: "pre_split_face f ram1 ram2 vs"
    "(f12, f21) = split_face f ram1 ram2 vs" "vs ≠ []"  "vs2 = between (vertices f) ram2 ram1 " "vs2 ≠ []"
  def c ≡ "fst x"
  def d ≡ "snd x"
  with c_def  have [simp]: "x = (c,d)" by simp
  from vors have dist_f21: "distinct (vertices f21)" apply (rule_tac split_face_distinct2) by auto
  from x vors show "x ∈ ?lhs"
    apply (simp add: dist_f21 is_nextElem_def is_sublist_def) apply (simp add: split_face_def)
    apply (case_tac "c = ram2 ∧ d = hd (between (vertices f) ram2 ram1)") apply simp apply (rule disjI1)
     apply (intro exI) apply (subgoal_tac "ram2 # between (vertices f) ram2 ram1 @ ram1 # vs =
       [] @ ram2 # hd (between (vertices f) ram2 ram1) # tl (between (vertices f) ram2 ram1) @ ram1 # vs") apply assumption apply simp
    apply (case_tac "c = ram1 ∧ d = hd vs") apply (rule disjI1)
     apply (case_tac "vs")  apply simp
     apply simp apply (intro exI)
     apply (subgoal_tac "ram2 # between (vertices f) ram2 ram1 @ ram1 # a # list =
        (ram2 # between (vertices f) ram2 ram1) @ ram1 # a # list") apply assumption apply simp
    apply (case_tac "c = last vs ∧ d = ram2")
     apply (case_tac vs rule:rev_exhaust) apply simp
     apply simp
    apply simp
    apply (case_tac "c = last (between (vertices f) ram2 ram1) ∧ d = ram1") apply (rule disjI1)
     apply (case_tac "between (vertices f) ram2 ram1" rule: rev_exhaust) apply simp
     apply (intro exI) apply simp
     apply (subgoal_tac "ram2 # ys @ y # ram1 # vs = (ram2 # ys) @ y # ram1 # vs")
      apply assumption
     apply simp
    apply simp
    apply (case_tac "(c, d) ∈ Edges vs") apply (simp add: Edges_def is_sublist_def)
     apply (elim exE) apply simp apply (rule conjI) apply (rule impI) apply (rule disjI1) apply (intro exI)
      apply (subgoal_tac "ram2 # between (vertices f) ram2 ram1 @ ram1 # as @ [c, d]
        = (ram2 # between (vertices f) ram2 ram1 @ ram1 # as) @ c # d # []") apply assumption apply simp
     apply (rule impI) apply (rule disjI1) apply (intro exI)
     apply (subgoal_tac "ram2 # between (vertices f) ram2 ram1 @ ram1 # as @ c # d # bs
        = (ram2 # between (vertices f) ram2 ram1 @ ram1 # as) @ c # d # bs") apply assumption apply simp
    apply (simp add: Edges_def is_sublist_def)
    apply (elim exE) apply simp apply (rule disjI1) apply (intro exI)
    apply (subgoal_tac "ram2 # as @ c # d # bs @ ram1 # vs = (ram2 # as) @ c # d # (bs @ ram1 # vs)")
     apply assumption by simp
qed


lemma split_face_edges_f21_vs: "pre_split_face f ram1 ram2 [] ==>
  (f12, f21) = split_face f ram1 ram2 [] ==> vs2 = between (vertices f) ram2 ram1 ==> vs2 ≠ [] ==>
  edges f21 = {(last vs2, ram1) , (ram1, ram2), (ram2, hd vs2)} ∪
  Edges vs2" (concl is "?lhs = ?rhs")
proof (intro equalityI subsetI)
  fix x
  assume x: "x ∈ ?lhs" and vors: "pre_split_face f ram1 ram2 []"
    "(f12, f21) = split_face f ram1 ram2 []" "vs2 = between (vertices f) ram2 ram1 " "vs2 ≠ []"
  def c ≡ "fst x"
  def d ≡ "snd x"
  with c_def  have [simp]: "x = (c,d)" by simp
  from vors have dist_f21: "distinct (vertices f21)" apply (rule_tac split_face_distinct2) by auto
  from x vors show "x ∈ ?rhs"
    apply (simp add: split_face_def is_nextElem_def is_sublist_def dist_f21)
    apply (case_tac " c = ram1 ∧ d = ram2") apply simp apply simp  apply (elim exE)

    apply (case_tac "c = ram1") apply simp
    apply (subgoal_tac "ram2 # between (vertices f) ram2 ram1 = as")
    apply (subgoal_tac "(ram2 # between (vertices f) ram2 ram1) @ [ram1]  = as @ ram1 # d # bs")
    apply (thin_tac "ram2 # between (vertices f) ram2 ram1 @ [ram1]  = as @ ram1 # d # bs")
    apply simp apply force
    apply (rule dist_at1) apply (rule dist_f21) apply (rule sym) apply simp apply simp
    (* a ≠ ram1 *)
    apply (case_tac "c ∈ set (between (vertices f) ram2 ram1)")
    apply (subgoal_tac "distinct (between (vertices f) ram2 ram1)") apply (simp add: in_set_conv_decomp) apply (elim exE) apply simp
    apply (case_tac zs) apply simp apply (subgoal_tac "ram2 # ys = as") apply force
    apply (rule dist_at1) apply (rule dist_f21) apply (rule sym) apply simp apply simp apply simp
    apply (subgoal_tac "ram2 # ys = as") apply (simp add: Edges_def is_sublist_def)
    apply (subgoal_tac "(ram2 # ys) @ c # a # list @ [ram1] = as @ c # d # bs")
    apply (thin_tac "ram2 # ys @ c # a # list @ [ram1] = as @ c # d # bs")
    apply (rule conjI) apply (rule impI) apply (rule disjI2)+ apply force
    apply (rule impI) apply (rule disjI2)+ apply force apply force
    apply (rule dist_at1) apply (rule dist_f21) apply (rule sym) apply simp apply simp
    apply (subgoal_tac "distinct (vertices f21)")
    apply (thin_tac "ram2 # between (vertices f) ram2 ram1 @ [ram1] = as @ c # d # bs") apply simp
    apply (rule dist_f21)
      (* c ∉  set (between (vertices f) ram2 ram1) *)
    apply (subgoal_tac "c = ram2") apply simp
    apply (subgoal_tac "[] = as") apply simp apply (case_tac "between (vertices f) ram2 ram1") apply simp apply simp
    apply (rule dist_at1) apply (rule dist_f21) apply (rule sym)  apply simp apply simp

    (* c ≠ ram2 *)
    apply (subgoal_tac "c ∈ set (ram2 # between (vertices f) ram2 ram1 @ [ram1])")
    apply (thin_tac "ram2 # between (vertices f) ram2 ram1 @ [ram1] = as @ c # d # bs") apply simp
    by simp
next
  fix x
  assume x: "x ∈ ?rhs" and vors: "pre_split_face f ram1 ram2 []"
    "(f12, f21) = split_face f ram1 ram2 []" "vs2 = between (vertices f) ram2 ram1 " "vs2 ≠ []"
  def c ≡ "fst x"
  def d ≡ "snd x"
  with c_def  have [simp]: "x = (c,d)" by simp
  from vors have dist_f21: "distinct (vertices f21)" apply (rule_tac split_face_distinct2) by auto
  from x vors show "x ∈ ?lhs"
    apply (simp add: dist_f21 is_nextElem_def is_sublist_def) apply (simp add: split_face_def)
    apply (case_tac "c = ram2 ∧ d = hd (between (vertices f) ram2 ram1)") apply simp apply (rule disjI1)
    apply (intro exI) apply (subgoal_tac "ram2 # between (vertices f) ram2 ram1 @ [ram1] =
       [] @ ram2 # hd (between (vertices f) ram2 ram1) # tl (between (vertices f) ram2 ram1) @ [ram1]") apply assumption apply simp
    apply (case_tac "c = ram1 ∧ d = ram2") apply (rule disjI2) apply simp apply simp
    apply (case_tac "c = last (between (vertices f) ram2 ram1) ∧ d = ram1") apply (rule disjI1)
      apply (case_tac "between (vertices f) ram2 ram1" rule: rev_exhaust) apply simp
      apply (intro exI) apply simp
      apply (subgoal_tac "ram2 # ys @ y # [ram1] = (ram2 # ys) @ y # [ram1]")
      apply assumption apply simp apply simp
    apply (simp add: Edges_def is_sublist_def)
      apply (elim exE) apply simp apply (rule disjI1) apply (intro exI)
      apply (subgoal_tac "ram2 # as @ c # d # bs @ [ram1] = (ram2 # as) @ c # d # (bs @ [ram1])")
      apply assumption by simp
qed


lemma split_face_edges_f21_bet: "pre_split_face f ram1 ram2 vs ==>
  (f12, f21) = split_face f ram1 ram2 vs ==> vs ≠ [] ==> between (vertices f) ram2 ram1 = [] ==>
  edges f21 = {(ram1, hd vs), (last vs, ram2), (ram2, ram1)} ∪
  Edges vs" (concl is "?lhs = ?rhs")
proof (intro equalityI subsetI)
  fix x
  assume x: "x ∈ ?lhs" and vors: "pre_split_face f ram1 ram2 vs"
    "(f12, f21) = split_face f ram1 ram2 vs" "vs ≠ []"  "between (vertices f) ram2 ram1 = []"
  def c ≡ "fst x"
  def d ≡ "snd x"
  with c_def  have [simp]: "x = (c,d)" by simp
  from vors have dist_f21: "distinct (vertices f21)" apply (rule_tac split_face_distinct2) by auto
  from x vors show "x ∈ ?rhs"
    apply (simp add: split_face_def is_nextElem_def is_sublist_def dist_f21)
    apply (case_tac " c = last vs ∧ d = ram2") apply simp
    apply simp apply (elim exE)
    apply (case_tac "c = ram1") apply simp
     apply (subgoal_tac "[ram2] = as") apply clarsimp
     apply (rule dist_at1) apply (rule dist_f21) apply (rule sym) apply simp apply simp
    (* a ≠ ram1 *)
    apply (case_tac "c ∈ set vs")
     apply (subgoal_tac "distinct vs") apply (simp add: in_set_conv_decomp) apply (elim exE) apply simp
      apply (case_tac "zs") apply simp
       apply (subgoal_tac "ram2 #  ram1 # ys = as") apply force
       apply (rule dist_at1) apply (rule dist_f21) apply (rule sym) apply simp apply simp
      apply simp
      apply (subgoal_tac "ram2 # ram1 # ys = as")
       apply (subgoal_tac "(ram2 # ram1 # ys) @ c # a # list = as @ c # d # bs")
        apply (thin_tac "ram2 #  ram1 # ys @ c # a # list = as @ c # d # bs")
        apply (simp add: Edges_def is_sublist_def) apply force
       apply force
      apply (rule dist_at1) apply (rule dist_f21) apply (rule sym) apply simp apply simp
     apply (simp add: pre_split_face_def)
    (* c ∉ set (rev vs) *)
    apply (subgoal_tac "c = ram2") apply simp
     apply (subgoal_tac "[] = as") apply simp
     apply (rule dist_at1) apply (rule dist_f21) apply (rule sym)  apply simp apply simp
    (* c ≠ ram2 *)
    apply (subgoal_tac "c ∈ set (ram2 # ram1 # vs)")
     apply (thin_tac "ram2 # ram1 # vs = as @ c # d # bs") apply simp
    by simp
next
  fix x
  assume x: "x ∈ ?rhs" and vors: "pre_split_face f ram1 ram2 vs"
    "(f12, f21) = split_face f ram1 ram2 vs" "vs ≠ []"  "between (vertices f) ram2 ram1 = []"
  def c ≡ "fst x"
  def d ≡ "snd x"
  with c_def  have [simp]: "x = (c,d)" by simp
  from vors have dist_f21: "distinct (vertices f21)" apply (rule_tac split_face_distinct2) by auto
  from x vors show "x ∈ ?lhs"
    apply (simp add: dist_f21 is_nextElem_def is_sublist_def) apply (simp add: split_face_def)
    apply (case_tac "c = ram2 ∧ d = ram1") apply simp apply (rule disjI1) apply force
    apply (case_tac "c = ram1 ∧ d = hd vs") apply (rule disjI1)
     apply (case_tac "vs")  apply simp
     apply simp apply (intro exI)
     apply (subgoal_tac "ram2 # ram1 # a # list =
        [ram2] @ ram1 # a # list") apply assumption  apply simp
    apply (case_tac "c = last vs ∧ d = ram2")
     apply (case_tac vs rule: rev_exhaust) apply simp
     apply simp
    apply (simp add: Edges_def is_sublist_def)
    apply (elim exE) apply simp apply (rule conjI) apply (rule impI) apply (rule disjI1) apply (intro exI)
     apply (subgoal_tac "ram2 # ram1 # as @ [c, d]
        = (ram2 # ram1 # as) @ c # d # []") apply assumption apply simp
    apply (rule impI) apply (rule disjI1) apply (intro exI)
    apply (subgoal_tac "ram2 #  ram1 # as @ c # d # bs
        = (ram2 # ram1 # as) @ c # d # bs") apply assumption by simp
qed


lemma split_face_edges_f21_bet_vs: "pre_split_face f ram1 ram2 [] ==>
  (f12, f21) = split_face f ram1 ram2 [] ==> between (vertices f) ram2 ram1 = [] ==>
  edges f21 = {(ram1, ram2), (ram2, ram1)}" (concl is "?lhs = ?rhs")
proof (intro equalityI subsetI)
  fix x
  assume x: "x ∈ ?lhs" and vors: "pre_split_face f ram1 ram2 []"
    "(f12, f21) = split_face f ram1 ram2 []" "between (vertices f) ram2 ram1 = []"
  def c ≡ "fst x"
  def d ≡ "snd x"
  with c_def  have [simp]: "x = (c,d)" by simp
  from vors have dist_f21: "distinct (vertices f21)" apply (rule_tac split_face_distinct2) by auto
  from x vors show "x ∈ ?rhs"
    apply (simp add: split_face_def is_nextElem_def is_sublist_def dist_f21)
    apply (case_tac " c = ram1 ∧ d = ram2") apply simp  apply simp apply (elim exE)
    apply (case_tac "as") apply  simp  apply (case_tac "list") by auto
next
  fix x
  assume x: "x ∈ ?rhs" and vors: "pre_split_face f ram1 ram2 []"
    "(f12, f21) = split_face f ram1 ram2 []" "between (vertices f) ram2 ram1 = []"
  def c ≡ "fst x"
  def d ≡ "snd x"
  with c_def  have [simp]: "x = (c,d)" by simp
  from vors have dist_f21: "distinct (vertices f21)" apply (rule_tac split_face_distinct2) by auto
  from x vors show "x ∈ ?lhs"
    apply (simp add: dist_f21 is_nextElem_def is_sublist_def) apply (simp add: split_face_def)
    by auto
qed

lemma split_face_edges_f21_subset: "pre_split_face f ram1 ram2 vs ==>
  (f12, f21) = split_face f ram1 ram2 vs ==> vs ≠ [] ==>
  {(last vs, ram2), (ram1, hd vs)} ∪ Edges vs ⊆ edges f21"
  apply (case_tac "between (vertices f) ram2 ram1")
    apply (frule split_face_edges_f21_bet)  apply simp apply simp apply simp apply force
    apply (frule split_face_edges_f21) apply simp+ by force

lemma verticesFrom_ram1: "pre_split_face f ram1 ram2 vs ==>
  verticesFrom f ram1 = ram1 # between (vertices f) ram1 ram2 @ ram2 # between (vertices f) ram2 ram1"
  apply (subgoal_tac "pre_between (vertices f) ram1 ram2")
  apply (subgoal_tac "distinct (vertices f)")
  apply (case_tac "before (vertices f) ram1 ram2")
  apply (simp add: verticesFrom_Def)
  apply (subgoal_tac "ram2 ∈ set (snd (splitAt ram1 (vertices f)))") apply (drule splitAt_ram)
  apply (subgoal_tac "snd (splitAt ram2 (snd (splitAt ram1 (vertices f)))) = snd (splitAt ram2 (vertices f))")
  apply simp apply (thin_tac "snd (splitAt ram1 (vertices f)) =
     fst (splitAt ram2 (snd (splitAt ram1 (vertices f)))) @
     ram2 # snd (splitAt ram2 (snd (splitAt ram1 (vertices f))))")  apply simp
  apply (rule before_dist_r2) apply simp apply simp
  apply (subgoal_tac "before (vertices f) ram2 ram1")
  apply (subgoal_tac "pre_between (vertices f) ram2 ram1")
  apply (simp add: verticesFrom_Def)
  apply (subgoal_tac "ram2 ∈ set (fst (splitAt ram1 (vertices f)))") apply (drule splitAt_ram)
  apply (subgoal_tac "fst (splitAt ram2 (fst (splitAt ram1 (vertices f)))) = fst (splitAt ram2 (vertices f))")
  apply simp apply (thin_tac "fst (splitAt ram1 (vertices f)) =
     fst (splitAt ram2 (fst (splitAt ram1 (vertices f)))) @
     ram2 # snd (splitAt ram2 (fst (splitAt ram1 (vertices f))))") apply simp
  apply (rule before_dist_r1) apply simp apply simp apply (simp add: pre_between_def) apply force
  apply (simp add: pre_split_face_def) by (rule pre_split_face_p_between)

lemma split_face_edges_f_vs1_vs2: "pre_split_face f ram1 ram2 vs ==>
  between (vertices f) ram1 ram2 = [] ==>
  between (vertices f) ram2 ram1 = [] ==>
  edges f = {(ram2, ram1) , (ram1, ram2)}" (concl is "?lhs = ?rhs")
proof (intro equalityI subsetI)
  fix x
  assume x: "x ∈ ?lhs" and vors: "pre_split_face f ram1 ram2 vs"
     "between (vertices f) ram1 ram2 = []"
     "between (vertices f) ram2 ram1 = []"
  def c ≡ "fst x"
  def d ≡ "snd x"
  with c_def  have [simp]: "x = (c,d)" by simp
  from vors have dist_f: "distinct (vertices f)" by (simp add: pre_split_face_def)
  from x vors show "x ∈ ?rhs" apply (simp add: dist_f)
    apply (subgoal_tac "pre_between (vertices f) ram1 ram2")
     apply (drule is_nextElem_or) apply assumption
     apply (simp add: Edges_def)
     apply (case_tac "is_sublist [c, d] [ram1, ram2]") apply (simp)
     apply (simp) apply blast
    by (rule pre_split_face_p_between)
  next
  fix x
  assume x: "x ∈ ?rhs" and vors: "pre_split_face f ram1 ram2 vs"
    "between (vertices f) ram1 ram2 = []"
    "between (vertices f) ram2 ram1 = []"
  def c ≡ "fst x"
  def d ≡ "snd x"
  with c_def  have [simp]: "x = (c,d)" by simp
  from vors have dist_f: "distinct (vertices f)" by (simp add: pre_split_face_def)
  from x vors show "x ∈ ?lhs" apply (simp add: dist_f)
    apply (subgoal_tac "ram1 ∈ \<V> f") apply (simp add: verticesFrom_is_nextElem verticesFrom_ram1)
    apply (simp add: is_nextElem_def) apply blast
    by (simp add: pre_split_face_def)
qed

lemma split_face_edges_f_vs1: "pre_split_face f ram1 ram2 vs ==>
  between (vertices f) ram1 ram2 = [] ==>
  vs2 = between (vertices f) ram2 ram1 ==> vs2 ≠ [] ==>
  edges f = {(last vs2, ram1) , (ram1, ram2), (ram2, hd vs2)} ∪
  Edges vs2" (concl is "?lhs = ?rhs")
proof (intro equalityI subsetI)
  fix x
  assume x: "x ∈ ?lhs" and vors: "pre_split_face f ram1 ram2 vs"
     "between (vertices f) ram1 ram2 = []"
     "vs2 = between (vertices f) ram2 ram1 " "vs2 ≠ []"
  def c ≡ "fst x"
  def d ≡ "snd x"
  with c_def  have [simp]: "x = (c,d)" by simp
  from vors have dist_f: "distinct (vertices f)" by (simp add: pre_split_face_def)
  from vors have dist_vs2: "distinct (ram2 # vs2 @ [ram1])" apply (simp only:)
    apply (rule between_distinct_r12) apply (rule dist_f) apply (rule not_sym) by (simp add: pre_split_face_def)
  from x vors show "x ∈ ?rhs" apply (simp add: dist_f)
    apply (subgoal_tac "pre_between (vertices f) ram1 ram2")
     apply (drule is_nextElem_or) apply assumption
     apply (simp add: Edges_def)
     apply (case_tac "is_sublist [c, d] [ram1, ram2]")
      apply simp
     apply simp
     apply(erule disjE) apply blast
     apply (case_tac "c = ram2")
      apply (case_tac "between (vertices f) ram2 ram1") apply simp
      apply simp
      apply (drule is_sublist_distinct_prefix)
       apply (subgoal_tac "distinct (ram2 # vs2 @ [ram1])")
        apply simp
       apply (rule dist_vs2)
      apply simp
     apply (case_tac "c = ram1")
      apply (subgoal_tac "¬ is_sublist [c, d] (ram2 # vs2 @ [ram1])")
       apply simp
      apply (rule is_sublist_notlast)
       apply (rule_tac dist_vs2)
      apply simp
     apply simp
     apply (simp add: is_sublist_def)
     apply (elim exE)
     apply (case_tac "between (vertices f) ram2 ram1" rule: rev_exhaust) apply simp
     apply simp
     apply (case_tac "bs" rule: rev_exhaust) apply simp
     apply simp
     apply (rule disjI2)
     apply (intro exI)
     apply simp
    apply (rule pre_split_face_p_between) by simp
  next
  fix x
  assume x: "x ∈ ?rhs" and vors: "pre_split_face f ram1 ram2 vs"
    "between (vertices f) ram1 ram2 = []"
    "vs2 = between (vertices f) ram2 ram1 " "vs2 ≠ []"
  def c ≡ "fst x"
  def d ≡ "snd x"
  with c_def  have [simp]: "x = (c,d)" by simp
  from vors have dist_f: "distinct (vertices f)" by (simp add: pre_split_face_def)
  from vors have dist_vs2: "distinct (ram2 # vs2 @ [ram1])" apply (simp only:)
    apply (rule between_distinct_r12) apply (rule dist_f) apply (rule not_sym) by (simp add: pre_split_face_def)
  from x vors show "x ∈ ?lhs" apply (simp add: dist_f)
    apply (subgoal_tac "ram1 ∈ set (vertices f)") apply (simp add: verticesFrom_is_nextElem verticesFrom_ram1)
    apply (simp add: is_nextElem_def)
    apply (case_tac "c = last (between (vertices f) ram2 ram1) ∧ d = ram1") apply simp apply simp apply (rule disjI1)
    apply (case_tac "c = ram1 ∧ d = ram2")  apply (simp add: is_sublist_def) apply force apply simp
    apply (case_tac "c = ram2 ∧ d = hd (between (vertices f) ram2 ram1)")
      apply (case_tac "between (vertices f) ram2 ram1") apply simp apply (simp add: is_sublist_def) apply (intro exI)
      apply (subgoal_tac "ram1 # ram2 # a # list =
        [ram1] @ ram2 # a # (list)") apply assumption apply simp
    apply simp
      apply (subgoal_tac "is_sublist [c, d] ((ram1 #
                        [ram2]) @ between (vertices f) ram2 ram1 @ [])")
      apply simp apply (rule is_sublist_add) apply (simp add: Edges_def)
    by (simp add: pre_split_face_def)
qed


lemma split_face_edges_f_vs2: "pre_split_face f ram1 ram2 vs ==>
  vs1 = between (vertices f) ram1 ram2 ==> vs1 ≠ [] ==>
  between (vertices f) ram2 ram1 = [] ==>
  edges f = {(ram2, ram1) , (ram1, hd vs1), (last vs1, ram2)} ∪
  Edges vs1" (concl is "?lhs = ?rhs")
proof (intro equalityI subsetI)
  fix x
  assume x: "x ∈ ?lhs" and vors: "pre_split_face f ram1 ram2 vs"
     "vs1 = between (vertices f) ram1 ram2 " "vs1 ≠ []"
     "between (vertices f) ram2 ram1 = []"
  def c ≡ "fst x"
  def d ≡ "snd x"
  with c_def  have [simp]: "x = (c,d)" by simp
  from vors have dist_f: "distinct (vertices f)" by (simp add: pre_split_face_def)
  from vors have dist_vs1: "distinct (ram1 # vs1 @ [ram2])" apply (simp only:)
    apply (rule between_distinct_r12) apply (rule dist_f) by (simp add: pre_split_face_def)
  from x vors show "x ∈ ?rhs" apply (simp add: dist_f)
    apply (subgoal_tac "pre_between (vertices f) ram1 ram2")
     apply (drule is_nextElem_or) apply assumption
     apply (simp add: Edges_def)
     apply (case_tac "is_sublist [c, d] (ram1 # between (vertices f) ram1 ram2 @ [ram2])")
      apply simp
      apply (case_tac "c = ram1")
       apply (case_tac "between (vertices f) ram1 ram2") apply simp
       apply simp
       apply (drule is_sublist_distinct_prefix)
        apply (subgoal_tac "distinct (ram1 # vs1 @ [ram2])") apply simp
        apply (rule dist_vs1)
       apply simp
      apply (case_tac "c = ram2")
       apply (subgoal_tac "¬ is_sublist [c, d] (ram1 # vs1 @ [ram2])") apply simp
       apply (rule is_sublist_notlast) apply (rule_tac dist_vs1)
       apply simp
      apply simp
      apply (simp add: is_sublist_def)
      apply (elim exE)
      apply (case_tac "between (vertices f) ram1 ram2" rule: rev_exhaust) apply simp
      apply simp
      apply (case_tac "bs" rule: rev_exhaust) apply simp
      apply simp
      apply (rule disjI2)
      apply (intro exI)
      apply simp
     apply simp
    apply (rule pre_split_face_p_between) by simp
  next
  fix x
  assume x: "x ∈ ?rhs" and vors: "pre_split_face f ram1 ram2 vs"
    "vs1 = between (vertices f) ram1 ram2 " "vs1 ≠ []"
    "between (vertices f) ram2 ram1 = []"
  def c ≡ "fst x"
  def d ≡ "snd x"
  with c_def  have [simp]: "x = (c,d)" by simp
  from vors have dist_f: "distinct (vertices f)" by (simp add: pre_split_face_def)
  from vors have dist_vs1: "distinct (ram1 # vs1 @ [ram2])" apply (simp only:)
    apply (rule between_distinct_r12) apply (rule dist_f) by (simp add: pre_split_face_def)
  from x vors show "x ∈ ?lhs" apply (simp add: dist_f)
    apply (subgoal_tac "ram1 ∈ \<V> f") apply (simp add: verticesFrom_is_nextElem verticesFrom_ram1)
    apply (simp add: is_nextElem_def)
    apply (case_tac "c = ram2 ∧ d = ram1") apply simp apply simp apply (rule disjI1)
    apply (case_tac "c = ram1 ∧ d = hd (between (vertices f) ram1 ram2)")
      apply (case_tac "between (vertices f) ram1 ram2") apply simp apply (force simp: is_sublist_def) apply simp
    apply (case_tac "c = last (between (vertices f) ram1 ram2) ∧ d = ram2")
      apply (case_tac "between (vertices f) ram1 ram2" rule: rev_exhaust) apply simp apply (simp add: is_sublist_def)
      apply (intro exI)
      apply (subgoal_tac "ram1 # ys @ [y, ram2] =
        (ram1 # ys) @ y # ram2 # []") apply assumption apply simp
    apply simp
      apply (simp add: Edges_def)
      apply (subgoal_tac "is_sublist [c, d] ([ram1] @ between (vertices f) ram1 ram2 @ [ram2])")
      apply simp apply (rule is_sublist_add) apply simp
    by (simp add: pre_split_face_def)
qed


lemma split_face_edges_f: "pre_split_face f ram1 ram2 vs ==>
  vs1 = between (vertices f) ram1 ram2 ==> vs1 ≠ [] ==>
  vs2 = between (vertices f) ram2 ram1 ==> vs2 ≠ [] ==>
  edges f = {(last vs2, ram1) , (ram1, hd vs1), (last vs1, ram2), (ram2, hd vs2)} ∪
  Edges vs1 ∪ Edges vs2" (concl is "?lhs = ?rhs")
proof (intro equalityI subsetI)
  fix x
  assume x: "x ∈ ?lhs" and vors: "pre_split_face f ram1 ram2 vs"
     "vs1 = between (vertices f) ram1 ram2 " "vs1 ≠ []"
     "vs2 = between (vertices f) ram2 ram1 " "vs2 ≠ []"
  def c ≡ "fst x"
  def d ≡ "snd x"
  with c_def  have [simp]: "x = (c,d)" by simp
  from vors have dist_f: "distinct (vertices f)" by (simp add: pre_split_face_def)
  from vors have dist_vs1: "distinct (ram1 # vs1 @ [ram2])" apply (simp only:)
    apply (rule between_distinct_r12) apply (rule dist_f) by (simp add: pre_split_face_def)
  from vors have dist_vs2: "distinct (ram2 # vs2 @ [ram1])" apply (simp only:)
    apply (rule between_distinct_r12) apply (rule dist_f) apply (rule not_sym) by (simp add: pre_split_face_def)
  from x vors show "x ∈ ?rhs" apply (simp add: dist_f)
    apply (subgoal_tac "pre_between (vertices f) ram1 ram2")
    apply (drule is_nextElem_or) apply assumption apply (simp add: Edges_def)
    apply (case_tac "is_sublist [c, d] (ram1 # between (vertices f) ram1 ram2 @ [ram2])") apply simp
      apply (case_tac "c = ram1")
        apply (case_tac "between (vertices f) ram1 ram2") apply simp apply simp
        apply (drule is_sublist_distinct_prefix) apply (subgoal_tac "distinct (ram1 # vs1 @ [ram2])")
        apply simp apply (rule dist_vs1) apply simp
      apply (case_tac "c = ram2")
        apply (subgoal_tac "¬ is_sublist [c, d] (ram1 # vs1 @ [ram2])") apply simp
        apply (rule is_sublist_notlast) apply (rule_tac dist_vs1) apply simp
      apply simp apply (simp add: is_sublist_def) apply (elim exE)
        apply (case_tac "between (vertices f) ram1 ram2" rule: rev_exhaust) apply simp apply simp
        apply (case_tac "bs" rule: rev_exhaust) apply simp apply simp
        apply (rule disjI2) apply (rule disjI2) apply (rule disjI1) apply (intro exI) apply simp
    apply simp
      apply (case_tac "c = ram2")
        apply (case_tac "between (vertices f) ram2 ram1") apply simp apply simp
        apply (drule is_sublist_distinct_prefix) apply (subgoal_tac "distinct (ram2 # vs2 @ [ram1])")
        apply simp apply (rule dist_vs2) apply simp
      apply (case_tac "c = ram1")
        apply (subgoal_tac "¬ is_sublist [c, d] (ram2 # vs2 @ [ram1])") apply simp
        apply (rule is_sublist_notlast) apply (rule_tac dist_vs2) apply simp
      apply simp apply (simp add: is_sublist_def) apply (elim exE)
        apply (case_tac "between (vertices f) ram2 ram1" rule: rev_exhaust) apply simp apply simp
        apply (case_tac "bs" rule: rev_exhaust) apply simp apply simp
        apply (rule disjI2) apply (rule disjI2) apply (rule disjI2) apply (intro exI) apply simp
   apply (rule pre_split_face_p_between) by simp
  next
  fix x
  assume x: "x ∈ ?rhs" and vors: "pre_split_face f ram1 ram2 vs"
    "vs1 = between (vertices f) ram1 ram2 " "vs1 ≠ []"
    "vs2 = between (vertices f) ram2 ram1 " "vs2 ≠ []"
  def c ≡ "fst x"
  def d ≡ "snd x"
  with c_def  have [simp]: "x = (c,d)" by simp
  from vors have dist_f: "distinct (vertices f)" by (simp add: pre_split_face_def)
  from vors have dist_vs1: "distinct (ram1 # vs1 @ [ram2])" apply (simp only:)
    apply (rule between_distinct_r12) apply (rule dist_f) by (simp add: pre_split_face_def)
  from vors have dist_vs2: "distinct (ram2 # vs2 @ [ram1])" apply (simp only:)
    apply (rule between_distinct_r12) apply (rule dist_f) apply (rule not_sym) by (simp add: pre_split_face_def)
  from x vors show "x ∈ ?lhs" apply (simp add: dist_f)
    apply (subgoal_tac "ram1 ∈ \<V> f") apply (simp add: verticesFrom_is_nextElem verticesFrom_ram1)
    apply (simp add: is_nextElem_def)
    apply (case_tac "c = last (between (vertices f) ram2 ram1) ∧ d = ram1") apply simp apply simp apply (rule disjI1)
    apply (case_tac "c = ram1 ∧ d = hd (between (vertices f) ram1 ram2)")
      apply (case_tac "between (vertices f) ram1 ram2") apply simp apply (force simp: is_sublist_def) apply simp
    apply (case_tac "c = last (between (vertices f) ram1 ram2) ∧ d = ram2")
      apply (case_tac "between (vertices f) ram1 ram2" rule: rev_exhaust) apply simp apply (simp add: is_sublist_def)
      apply (intro exI)
      apply (subgoal_tac "ram1 # ys @ y # ram2 # between (vertices f) ram2 ram1 =
        (ram1 # ys) @ y # ram2 # (between (vertices f) ram2 ram1)") apply assumption apply simp apply simp
    apply (case_tac "c = ram2 ∧ d = hd (between (vertices f) ram2 ram1)")
      apply (case_tac "between (vertices f) ram2 ram1") apply simp apply (simp add: is_sublist_def) apply (intro exI)
      apply (subgoal_tac "ram1 # between (vertices f) ram1 ram2 @ ram2 # a # list =
        (ram1 # between (vertices f) ram1 ram2) @ ram2 # a # (list)") apply assumption apply simp apply simp
    apply (case_tac "(c, d) ∈ Edges (between (vertices f) ram1 ram2)") apply (simp add: Edges_def)
      apply (subgoal_tac "is_sublist [c, d] ([ram1] @ between (vertices f) ram1 ram2 @
                        (ram2 # between (vertices f) ram2 ram1))")
      apply simp apply (rule is_sublist_add) apply simp
    apply simp
      apply (subgoal_tac "is_sublist [c, d] ((ram1 # between (vertices f) ram1 ram2 @
                        [ram2]) @ between (vertices f) ram2 ram1 @ [])")
      apply simp apply (rule is_sublist_add) apply (simp add: Edges_def)
    by (simp add: pre_split_face_def)
qed


lemma split_face_edges_f12_f21:
  "pre_split_face f ram1 ram2 vs ==> (f12, f21) = split_face f ram1 ram2 vs ==>
   vs ≠ []
  ==> edges f12 ∪ edges f21 = edges f ∪
     {(hd vs, ram1), (ram1, hd vs), (last vs, ram2), (ram2, last vs)} ∪
     Edges vs ∪
     Edges (rev vs)"
  apply (case_tac "between (vertices f) ram1 ram2 = []")
    apply (case_tac "between (vertices f) ram2 ram1 = []")
      apply (simp add: split_face_edges_f12_bet split_face_edges_f21_bet split_face_edges_f_vs1_vs2)
      apply force
    apply (simp add: split_face_edges_f12_bet split_face_edges_f21 split_face_edges_f_vs1) apply force
  apply (case_tac "between (vertices f) ram2 ram1 = []")
    apply (simp add: split_face_edges_f21_bet split_face_edges_f12 split_face_edges_f_vs2) apply force
  apply (simp add: split_face_edges_f21 split_face_edges_f12 split_face_edges_f) by force


lemma split_face_edges_f12_f21_vs:
  "pre_split_face f ram1 ram2 [] ==> (f12, f21) = split_face f ram1 ram2 []
  ==> edges f12 ∪ edges f21 = edges f ∪
     {(ram2, ram1), (ram1, ram2)}"
  apply (case_tac "between (vertices f) ram1 ram2 = []")
    apply (case_tac "between (vertices f) ram2 ram1 = []")
      apply (simp add: split_face_edges_f12_bet_vs split_face_edges_f21_bet_vs split_face_edges_f_vs1_vs2)
      apply force
    apply (simp add: split_face_edges_f12_bet_vs split_face_edges_f21_vs split_face_edges_f_vs1) apply force
  apply (case_tac "between (vertices f) ram2 ram1 = []")
    apply (simp add: split_face_edges_f21_bet_vs split_face_edges_f12_vs split_face_edges_f_vs2) apply force
  apply (simp add: split_face_edges_f21_vs split_face_edges_f12_vs split_face_edges_f) by force


lemma split_face_edges_f12_f21_sym:
  "f ∈ \<F> g ==>
  pre_split_face f ram1 ram2 vs ==> (f12, f21) = split_face f ram1 ram2 vs
  ==> ((a,b) ∈ edges f12 ∨ (a,b) ∈  edges f21) =
     ((a,b) ∈ edges f  ∨
  (((b,a) ∈ edges f12 ∨ (b,a) ∈  edges f21) ∧
  ((a,b) ∈ edges f12 ∨ (a,b) ∈ edges f21)))"
  apply (subgoal_tac "((a,b) ∈ edges f12 ∪ edges f21) =
     ((a,b) ∈ edges f ∨ ((b,a) ∈ edges f12 ∪ edges f21) ∧ (a,b) ∈ edges f12 ∪ edges f21)") apply force
  apply (case_tac "vs = []")
    apply (subgoal_tac "pre_split_face f ram1 ram2 []")
    apply (drule split_face_edges_f12_f21_vs) apply simp apply simp apply force apply simp
  apply (drule split_face_edges_f12_f21) apply simp apply simp
    apply simp by force

lemma splitFace_edges_g'_help: "pre_splitFace g ram1 ram2 f vs ==>
  (f12, f21, g') = splitFace g ram1 ram2 f vs ==> vs ≠ [] ==>
  edges g' = edges g ∪ edges f ∪ Edges vs ∪ Edges(rev vs) ∪
  {(ram2, last vs), (hd vs, ram1), (ram1, hd vs), (last vs, ram2)}"
proof -
  assume pre: "pre_splitFace g ram1 ram2 f vs"
    and fdg: "(f12, f21, g') = splitFace g ram1 ram2 f vs"
    and vs_neq: "vs ≠ []"

  from pre fdg have split: "(f12, f21) = split_face f ram1 ram2 vs"
    apply (unfold pre_splitFace_def) apply (elim conjE)
    by (simp add: splitFace_split_face)

  from fdg pre have "edges g' = (\<Union>a∈set (replace f [f21] (faces g)) edges a) ∪
       edges (f12)" by(auto simp: splitFace_def split_def edges_graph_def)
  with pre vs_neq show ?thesis apply (simp add: UNION_def) apply (rule equalityI) apply simp
    apply (rule conjI) apply (rule subsetI) apply simp apply (erule bexE) apply (drule replace5)
    apply (case_tac "xa ∈ \<F> g") apply simp
    apply (subgoal_tac "x ∈ edges g") apply simp
    apply (simp add: edges_graph_def) apply force
    apply simp
    apply (subgoal_tac "pre_split_face f ram1 ram2 vs")
    apply (case_tac "between (vertices f) ram2 ram1 = []")
      apply (frule split_face_edges_f21_bet) apply (rule split) apply simp apply simp
      apply (case_tac "between (vertices f) ram1 ram2 = []")
        apply (frule split_face_edges_f_vs1_vs2) apply simp apply simp apply simp apply force
        apply (frule split_face_edges_f_vs2) apply simp apply simp apply simp apply force
    apply (frule split_face_edges_f21) apply (rule split) apply simp apply simp apply simp
      apply (case_tac "between (vertices f) ram1 ram2 = []")
        apply (frule split_face_edges_f_vs1) apply simp apply simp apply simp apply simp apply force
        apply (frule split_face_edges_f) apply simp apply simp apply simp apply simp apply force
    apply simp
    apply (subgoal_tac "pre_split_face f ram1 ram2 vs")
    apply (case_tac "between (vertices f) ram1 ram2 = []")
      apply (frule split_face_edges_f12_bet) apply (rule split) apply simp apply simp
      apply (case_tac "between (vertices f) ram2 ram1 = []")
        apply (frule split_face_edges_f_vs1_vs2) apply simp apply simp apply simp apply force
        apply (frule split_face_edges_f_vs1) apply simp apply simp apply simp apply force
    apply (frule split_face_edges_f12) apply (rule split) apply simp apply simp apply simp
      apply (case_tac "between (vertices f) ram2 ram1 = []")
        apply (frule split_face_edges_f_vs2) apply simp apply simp apply simp apply simp apply force
        apply (frule split_face_edges_f) apply simp apply simp apply simp apply simp apply force
    apply simp
    apply simp
    apply (subgoal_tac "pre_split_face f ram1 ram2 vs")
    apply (subgoal_tac "(ram2, last vs) ∈ edges f12 ∧ (hd vs, ram1) ∈ edges f12")
      apply (rule conjI) apply simp
      apply (rule conjI) apply simp
    apply (subgoal_tac "(ram1, hd vs) ∈ edges f21 ∧ (last vs, ram2) ∈ edges f21")
      apply (rule conjI) apply (rule disjI1) apply (rule bexI) apply (elim conjE) apply simp
        apply (rule replace3) apply(erule pre_splitFace_oldF) apply simp
      apply (rule conjI) apply (rule disjI1) apply (rule bexI) apply (elim conjE) apply simp
        apply (rule replace3) apply(erule pre_splitFace_oldF)
    apply simp
    apply (subgoal_tac "edges f ⊆ {y. ∃x∈set (replace f [f21] (faces g)). y ∈ edges x} ∪ edges f12")
    apply (subgoal_tac "edges g ⊆ {y. ∃x∈set (replace f [f21] (faces g)). y ∈ edges x} ∪ edges f12")
      apply (rule conjI) apply simp
      apply (rule conjI) apply simp
    apply (subgoal_tac "Edges(rev vs) ⊆ edges f12") apply (rule conjI) prefer 2 apply blast
    apply (subgoal_tac "Edges vs ⊆ edges f21")
      apply (subgoal_tac "Edges vs ⊆ {y. ∃x∈set (replace f [f21] (faces g)). y ∈ edges x}") apply blast
      apply (rule subset_trans) apply  assumption apply (rule subsetI) apply simp apply (rule bexI) apply simp
      apply (rule replace3) apply(erule pre_splitFace_oldF) apply simp
    (* jetzt alle 7 subgoals aufloesen *)
    apply (frule split_face_edges_f21_subset) apply (rule split)  apply simp apply simp
    apply (frule split_face_edges_f12_subset) apply (rule split) apply simp apply simp
    apply (simp add: edges_graph_def)  apply (rule subsetI) apply simp apply (elim bexE)
      apply (case_tac "xa = f") apply simp apply blast
      apply (rule disjI1) apply (rule bexI) apply simp apply (rule replace4) apply simp apply force
    apply (rule subsetI)
      apply (subgoal_tac "∃ u v. x = (u,v)") apply (elim exE conjE)
      apply (frule split_face_edges_or [OF split]) apply simp
      apply (case_tac "(u, v) ∈ edges f12") apply simp apply simp
      apply (rule bexI) apply (thin_tac "(u, v) ∈ edges f")  apply assumption
      apply (rule replace3) apply(erule pre_splitFace_oldF) apply simp apply simp
    apply (frule split_face_edges_f21_subset) apply (rule split) apply simp apply simp
    apply (frule split_face_edges_f12_subset) apply (rule split) apply simp apply simp
  by simp
qed

lemma pre_splitFace_edges_f_in_g: "pre_splitFace g ram1 ram2 f vs ==> edges f ⊆ edges g"
  apply (simp add: edges_graph_def) by (force)

lemma pre_splitFace_edges_f_in_g2: "pre_splitFace g ram1 ram2 f vs ==> x ∈ edges f ==> x ∈ edges g"
  apply (simp add: edges_graph_def) by (force)

lemma splitFace_edges_g': "pre_splitFace g ram1 ram2 f vs ==>
  (f12, f21, g') = splitFace g ram1 ram2 f vs ==> vs ≠ [] ==>
  edges g' = edges g ∪ Edges vs ∪ Edges(rev vs) ∪
  {(ram2, last vs), (hd vs, ram1), (ram1, hd vs), (last vs, ram2)}"
  apply (subgoal_tac "edges g ∪ edges f = edges g")
  apply (frule splitFace_edges_g'_help) apply simp apply simp apply simp
  apply (frule pre_splitFace_edges_f_in_g) by blast


lemma splitFace_edges_g'_vs: "pre_splitFace g ram1 ram2 f [] ==>
  (f12, f21, g') = splitFace g ram1 ram2 f []  ==>
  edges g' = edges g ∪ {(ram1, ram2), (ram2, ram1)}"
proof -
  assume pre: "pre_splitFace g ram1 ram2 f []"
    and fdg: "(f12, f21, g') = splitFace g ram1 ram2 f []"

  from pre fdg have split: "(f12, f21) = split_face f ram1 ram2 []"
    apply (unfold pre_splitFace_def) apply (elim conjE)
    by (simp add: splitFace_split_face)

  from fdg pre have "edges g' = (\<Union>a∈set (replace f [f21] (faces g)) edges a) ∪
       edges (f12)" by (auto simp: splitFace_def split_def edges_graph_def)
  with pre show ?thesis apply (simp add: UNION_def) apply (rule equalityI) apply simp
    apply (rule conjI) apply (rule subsetI) apply simp apply (erule bexE) apply (drule replace5)
    apply (case_tac "xa ∈ \<F> g") apply simp
    apply (subgoal_tac "x ∈ edges g") apply simp
    apply (simp add: edges_graph_def) apply force
    apply simp
    apply (subgoal_tac "pre_split_face f ram1 ram2 []")
    apply (case_tac "between (vertices f) ram2 ram1 = []") apply (simp add: pre_FaceDiv_between2)
      apply (frule split_face_edges_f21_vs) apply (rule split) apply simp apply simp apply simp
      apply (case_tac "x = (ram1, ram2)") apply simp apply simp apply (rule disjI2)
      apply (rule pre_splitFace_edges_f_in_g2)  apply simp
      apply (subgoal_tac "pre_split_face f ram1 ram2 []")
      apply (frule split_face_edges_f) apply simp apply simp apply (rule pre_FaceDiv_between1) apply simp apply simp
      apply simp apply force  apply simp apply simp

    apply (rule subsetI) apply simp
    apply (subgoal_tac "pre_split_face f ram1 ram2 []")
    apply (case_tac "between (vertices f) ram1 ram2 = []") apply (simp add: pre_FaceDiv_between1)
      apply (frule split_face_edges_f12_vs) apply (rule split) apply simp apply simp apply simp
      apply (case_tac "x = (ram2, ram1)") apply simp apply simp apply (rule disjI2)
      apply (rule pre_splitFace_edges_f_in_g2)  apply simp
      apply (subgoal_tac "pre_split_face f ram1 ram2 []")
      apply (frule split_face_edges_f) apply simp apply simp apply simp apply (rule pre_FaceDiv_between2) apply simp
      apply simp apply force apply simp apply simp
   apply simp
   apply (subgoal_tac "pre_split_face f ram1 ram2 []")
   apply (subgoal_tac "(ram1, ram2) ∈ edges f21")
   apply (rule conjI) apply (rule disjI1) apply (rule bexI) apply simp apply (force)
   apply (subgoal_tac "(ram2, ram1) ∈ edges f12")
   apply (rule conjI) apply force
   apply (rule subsetI) apply (simp add: edges_graph_def) apply (elim bexE)
     apply (case_tac "xa = f") apply simp
     apply (subgoal_tac "∃ u v. x = (u,v)") apply (elim exE conjE)
     apply (subgoal_tac "pre_split_face f ram1 ram2 []")
     apply (frule split_face_edges_or [OF split]) apply simp
     apply (case_tac "(u, v) ∈ edges f12") apply simp apply simp apply force apply simp  apply simp
     apply (rule disjI1) apply (rule bexI) apply simp apply (rule replace4) apply simp apply force
   apply (frule split_face_edges_f12_vs) apply simp apply (rule split) apply simp
     apply (rule pre_FaceDiv_between1) apply simp apply simp
   apply (frule split_face_edges_f21_vs) apply simp apply (rule split) apply simp
     apply (rule pre_FaceDiv_between2) apply simp apply simp
   by simp
qed


lemma splitFace_edges_incr:
 "pre_splitFace g ram1 ram2 f vs ==>
  (f1, f2, g') = splitFace g ram1 ram2 f vs  ==>
  edges g ⊆ edges g'"
apply(cases vs)
 apply(simp add:splitFace_edges_g'_vs)
 apply blast
apply(simp add:splitFace_edges_g')
apply blast
done

lemma snd_snd_splitFace_edges_incr:
 "pre_splitFace g v1 v2 f vs ==>
  edges g ⊆ edges(snd(snd(splitFace g v1 v2 f vs)))"
apply(erule splitFace_edges_incr
 [where f1 = "fst(splitFace g v1 v2 f vs)"
  and f2 = "fst(snd(splitFace g v1 v2 f vs))"])
apply(auto)
done


(********************* Vorbereitung für subdivFace *****************)

(**** computes the list of ram vertices **********)
subsection {* @{text removeNones} *}

constdefs removeNones :: "'a option list => 'a list"
"removeNones vOptionList ≡ [the x. x ∈ vOptionList, (λx. x ≠ None)]"

(* "removeNones vOptionList ≡ map the [x ∈ vOptionList. x ≠ None]" *)

declare  removeNones_def [simp]
lemma removeNones_inI[intro]: "Some a ∈ set ls ==> a ∈ set (removeNones ls)" by (induct ls)  auto
lemma removeNones_hd[simp]: "removeNones ( Some a # ls) = a # removeNones ls" by auto
lemma removeNones_last[simp]: "removeNones (ls @ [Some a]) = removeNones ls @ [a]" by auto
lemma removeNones_in[simp]: "removeNones (as @ Some a # bs) = removeNones as @ a # removeNones bs" by auto
lemma removeNones_none_hd[simp]: "removeNones ( None # ls) = removeNones ls" by auto
lemma removeNones_none_last[simp]: "removeNones (ls @ [None]) = removeNones ls" by auto
lemma removeNones_none_in[simp]: "removeNones (as @ None # bs) = removeNones (as @ bs)" by auto
lemma removeNones_inI[intro]: "Some a ∈ set ls ==> a ∈ set (removeNones ls)" by (induct ls)  auto
lemma removeNones_empty[simp]: "removeNones [] = []" by auto
declare removeNones_def [simp del]





(************* natToVertexList ************)
subsection{* @{text natToVertexList} *}

(* Hilfskonstrukt natToVertexList *)
consts natToVertexListRec ::
  "nat => vertex => face => nat list => vertex option list"
primrec
  "natToVertexListRec old v f [] = []"
  "natToVertexListRec old v f (i#is) =
    (if i = old then None#natToVertexListRec i v f is
     else Some (fi • v)
          # natToVertexListRec i v f is)"

consts natToVertexList ::
  "vertex => face => nat list => vertex option list"
primrec
  "natToVertexList v f [] = []"
  "natToVertexList v f (i#is) =
    (if i = 0 then (Some v)#(natToVertexListRec i v f is) else [])"


subsection {* @{const indexToVertexList} *}

lemma  nextVertex_inj:
 "distinct (vertices f) ==> v ∈ \<V> f ==>
 i < length (vertices (f::face)) ==> a < length (vertices f) ==>
 fa•v = fi•v ==> i = a"
proof -
  assume d: "distinct (vertices f)" and v: "v ∈ \<V> f" and i: "i < length (vertices (f::face))"
    and a: "a < length (vertices f)" and eq:" fa•v = fi•v"
  then have eq: "(verticesFrom f v)!a = (verticesFrom f v)!i " by (simp add: verticesFrom_nth)
  def xs ≡ "verticesFrom f v"
  with eq have eq: "xs!a = xs!i" by auto
  from d v have z: "distinct (verticesFrom f v)" by auto
  moreover
  from xs_def a v d have "(verticesFrom f v) = take a xs @ xs ! a # drop (Suc a) xs"
    by (auto intro: id_take_nth_drop simp: verticesFrom_length)
  with eq have "(verticesFrom f v) = take a xs @ xs ! i # drop (Suc a) xs" by simp
  moreover
  from xs_def i v d have "(verticesFrom f v) = take i xs @ xs ! i # drop (Suc i) xs"
    by (auto intro: id_take_nth_drop simp: verticesFrom_length)
  ultimately have "take a xs = take i xs" by (rule dist_at1)
  moreover
  from v d have vertFrom[simp]: "length (vertices f) = length (verticesFrom f v)"
    by (auto simp: verticesFrom_length)
  from xs_def a i have "a < length xs" "i < length xs" by auto
  moreover
  have "!! a i. a < length xs ==> i < length xs ==> take a xs = take i xs ==> a = i"
  proof (induct xs)
    case Nil then show ?case by auto
  next
    case (Cons x xs) then show ?case
      apply (cases a) apply auto
      apply (cases i) apply auto
      apply (cases i) by auto
  qed
  ultimately show ?thesis by simp
qed

lemma a: "distinct (vertices f) ==> v ∈ \<V> f ==> (∀i ∈ set is. i < length (vertices f)) ==>
 (!!a. a < length (vertices f) ==> hideDupsRec ((f • ^ a) v) [(f • ^ k) v. k ∈ is] = natToVertexListRec a v f is)"
proof (induct "is")
  case Nil then show ?case by simp
next
  case (Cons i "is") then show ?case
   by (auto simp: nextVertices_def intro: nextVertex_inj)
qed

lemma indexToVertexList_natToVertexList_eq: "distinct (vertices f) ==> v ∈ \<V> f ==>
  (∀i ∈ set is. i < length (vertices f)) ==> is ≠ [] ==>
 hd is = 0 ==> indexToVertexList f v is = natToVertexList v f is"
apply (cases "is") by (auto simp: a [where a = 0, simplified] indexToVertexList_def nextVertices_def)



(********************* Einschub Ende ***************************************)


(******** natToVertexListRec ************)

lemma nvlr_length: "!! old.  (length (natToVertexListRec old v f ls)) = length ls"
apply (induct ls) by auto

lemma nvl_length[simp]: "hd e = 0 ==> length (natToVertexList v f e) = length e"
apply (cases "e")
by (auto intro: nvlr_length)


lemma nvl_nvlRec: "1 < i ==> incrIndexList e i (length (vertices f)) ==> natToVertexList v f e = (Some v) # natToVertexListRec 0 v f (tl e)"
apply (case_tac "e") apply simp  apply (subgoal_tac "a = 0") by auto

lemma natToVertexListRec_length[simp]: "!! e f. length (natToVertexListRec e v f es) = length es"
by (induct es) auto

lemma natToVertexList_length[simp]: "incrIndexList es (length es) (length (vertices f)) ==>
length (natToVertexList v f es) = length es" apply (case_tac es) by simp_all


lemma  natToVertexList_nth_Suc: "incrIndexList es (length es) (length (vertices f)) ==> Suc n < length es ==>
(natToVertexList v f es)!(Suc n) = (if (es!n = es!(Suc n)) then None else (Some f(es!Suc n) • v))"
proof -
  assume incr: "incrIndexList es (length es) (length (vertices f))" and n: "Suc n < length es"
  have rec: "!! old n. Suc n < length es ==>
    (natToVertexListRec old v f es)!(Suc n) = (if (es!n = es!(Suc n)) then None else (Some f(es!Suc n) • v))"
  proof (induct es)
    case Nil then show ?case by auto
  next
    case (Cons e es)
    note cons1 = this
    then show ?case
    proof (cases es)
      case Nil with cons1 show ?thesis by simp
    next
      case (Cons e' es')
      with cons1 show ?thesis
      proof (cases n)
        case 0 with Cons cons1 show ?thesis by simp
      next
        case (Suc m) with Cons cons1
        have "!! old. natToVertexListRec old v f es ! Suc m = (if es ! m = es ! Suc m then None else Some fes ! Suc m • v)"
          by (rule_tac cons1) auto
        then show ?thesis apply (cases "e = old") by (simp_all add: Suc)
      qed
    qed
  qed
  with  n have "natToVertexListRec 0 v f es ! Suc n = (if es ! n = es ! Suc n then None else Some fes ! Suc n • v)" by (rule_tac rec) auto
  with incr show ?thesis by (cases es) auto
qed

lemma  natToVertexList_nth_0: "incrIndexList es (length es) (length (vertices f)) ==> 0 < length es ==>
(natToVertexList v f es)!0 = (Some f(es!0) • v)" apply (cases es) apply (simp_all add: nextVertices_def) by (subgoal_tac "a = 0")  auto

lemma  natToVertexList_hd[simp]:
  "incrIndexList es (length es) (length (vertices f)) ==> hd (natToVertexList v f es) = Some v"
  apply (cases es) by (simp_all add: nextVertices_def)

lemma nth_last[intro]: "Suc i = length xs ==>  xs!i = last xs"
by (cases xs rule: rev_exhaust)  auto


declare incrIndexList_help4 [simp del]

lemma natToVertexList_last[simp]:
  "distinct (vertices f) ==> v ∈ \<V> f ==> incrIndexList es (length es) (length (vertices f)) ==> last (natToVertexList v f es) = Some (last (verticesFrom f v))"
proof -
  assume vors: "distinct (vertices f)" "v ∈ \<V> f" and incr: "incrIndexList es (length es) (length (vertices f))"
  def n' ≡ "length es - 2"
  from incr have "1 < length es" by auto
  with n'_def have n'l: "Suc (Suc n') = length es" by arith
  from incr n'l have last_ntvl: "(natToVertexList v f es)!(Suc n') = last (natToVertexList v f es)" by auto
  from n'l have last_es: "es!(Suc n') = last es" by auto
  from n'l  have "es!n' = last (butlast es)" apply (cases es rule: rev_exhaust) by (auto simp: nth_append)
  with last_es incr have less: "es!n' < es!(Suc n')" by auto
  from n'l have "Suc n' < length es" by arith
  with incr less have "(natToVertexList v f es)!(Suc n') = (Some f(es!Suc n') • v)" by (auto dest: natToVertexList_nth_Suc)
  with incr last_ntvl last_es have rule1: "last (natToVertexList v f es) = Some f((length (vertices f)) - (Suc 0)) • v" by auto

  from incr have lvf: "1 < length (vertices f)" by auto
  with vors have rule2: "verticesFrom f v ! ((length (vertices f)) - (Suc 0)) = f((length (vertices f)) - (Suc 0)) • v" apply (auto intro!: verticesFrom_nth) by arith

  from vors lvf have "verticesFrom f v ! ((length (vertices f)) - (Suc 0)) = last (verticesFrom f v)"
    apply (rule_tac nth_last)
    apply (auto simp: verticesFrom_length)
    by arith
  with rule1 rule2 show ?thesis by auto
qed

lemma indexToVertexList_last[simp]:
  "distinct (vertices f) ==> v ∈ \<V> f ==> incrIndexList es (length es) (length (vertices f)) ==> last (indexToVertexList f v es) = Some (last (verticesFrom f v))"
apply (subgoal_tac "indexToVertexList f v es = natToVertexList v f es") apply simp
apply (rule indexToVertexList_natToVertexList_eq) by auto

lemma sublist_take: "!! n iset. ∀ i ∈ iset. i < n ==> sublist (take n xs) iset = sublist xs iset"
proof (induct xs)
  case Nil then show ?case by simp
next
  case (Cons x xs) then show ?case apply (simp add: sublist_Cons) apply (cases n) apply simp apply (simp add: sublist_Cons) apply (rule Cons) by auto
qed


lemma sublist_reduceIndices: "!! iset. sublist xs iset = sublist xs {i. i < length xs ∧ i ∈ iset}"
proof (induct xs)
  case Nil then show ?case by simp
next
  case (Cons x xs) then
  have "sublist xs {j. Suc j ∈ iset} = sublist xs {i. i < length xs ∧ i ∈ {j. Suc j ∈ iset}}" by (rule_tac Cons)
  then show ?case by (simp add: sublist_Cons)
qed

lemma natToVertexList_sublist1: "distinct (vertices f) ==>
  v ∈ \<V> f ==> vs = verticesFrom f v ==>
  incrIndexList es (length es) (length vs) ==> n ≤  length es ==>
  sublist (take (Suc (es!(n - 1))) vs) (set (take n es))
  = removeNones (take n (natToVertexList v f es))"
proof (induct n)
  case 0 then show ?case by simp
next
  case (Suc n)
  then have "sublist (take (Suc (es ! (n - Suc 0))) (verticesFrom f v)) (set (take n es)) = removeNones (take n (natToVertexList v f es))"
    "distinct (vertices f)" "v ∈ \<V> f" "vs = verticesFrom f v" "incrIndexList es (length es) (length (verticesFrom f v))" "Suc n ≤ length es" by auto  (* does this improve the performance? *)
  note suc1 = this
  then have lvs: "length vs = length (vertices f)" by (auto intro: verticesFrom_length)
  with suc1 have vsne: "vs ≠ []" by auto
  with suc1 show ?case
  proof (cases "natToVertexList v f es ! n")
    case None then show ?thesis
    proof (cases n)
      case 0 with None suc1 lvs show ?thesis by (simp add: take_Suc_conv_app_nth natToVertexList_nth_0)
    next
      case (Suc n')
      with None suc1 lvs have esn: "es!n = es!n'" by (simp add: natToVertexList_nth_Suc split: split_if_asm)
      from Suc have n': "n - Suc 0 = n'" by auto
      show ?thesis
      proof (cases "Suc n = length es")
        case True then
        have small_n: "n < length es" by auto
        from True have "take (Suc n) es = es" by auto
        with small_n have "take n es @ [es!n] = es" by (simp add: take_Suc_conv_app_nth)
        then have esn_simps: "take n es = butlast es ∧  es!n = last es" by (cases es rule: rev_exhaust) auto

        from True Suc have n'l: "Suc n' = length (butlast es)" apply auto by arith
        then have small_n': "n' < length (butlast es)" by auto

        from Suc small_n have take_n': "take (Suc n') (butlast es @ [last es]) = take (Suc n') (butlast es)" by auto
        
        from small_n have es_exh: "es = butlast es @ [last es]" by (cases es rule: rev_exhaust) auto
        
        from n'l have "take (Suc n') (butlast es @ [last es]) = butlast es" by auto
        with es_exh have "take (Suc n') es = butlast es" by auto
        with small_n Suc have "take n' es @ [es!n'] = (butlast es)" by (simp add: take_Suc_conv_app_nth)
        with small_n' have esn'_simps: "take n' es = butlast (butlast es) ∧  es!n' = last (butlast es)"
          by (cases "butlast es" rule: rev_exhaust) auto

        from suc1 have "last (butlast es) < last es" by auto
        with esn esn_simps esn'_simps have False by auto (* have "last (butlast es) = last es" by auto  *)
        then show ?thesis by auto
      next
        case False with suc1 have le: "Suc n < length es" by auto
        from suc1 le have "es = take (Suc n) es @ es!(Suc n) # drop (Suc (Suc n)) es" by (auto intro: id_take_nth_drop)
        with suc1 have "increasing (take (Suc n) es @ es!(Suc n) # drop (Suc (Suc n)) es)" by auto
        then have "∀ i ∈ (set (take (Suc n) es)). i ≤  es ! (Suc n)" by (auto intro: increasing2)
        with suc1 have  "∀ i ∈ (set (take n es)). i ≤  es ! (Suc n)" by (simp add: take_Suc_conv_app_nth)
        then have seq: "sublist (take (Suc (es ! Suc n)) (verticesFrom f v)) (set (take n es))
          = sublist (verticesFrom f v) (set (take n es))"
          apply (rule_tac sublist_take) by auto
        from suc1 have "es = take n es @ es!n # drop (Suc n) es" by (auto intro: id_take_nth_drop)
        with suc1 have "increasing (take n es @ es!n # drop (Suc n) es)" by auto
        then have "∀ i ∈ (set (take n es)). i ≤  es ! n" by (auto intro: increasing2)
        with suc1 esn have  "∀ i ∈ (set (take n es)). i ≤  es ! n'" by (simp add: take_Suc_conv_app_nth)
        with Suc have seq2: "sublist (take (Suc (es ! n')) (verticesFrom f v)) (set (take n es))
         = sublist  (verticesFrom f v) (set (take n es))"
          apply (rule_tac sublist_take) by auto
        from Suc suc1 have "(insert (es ! n') (set (take n es))) = set (take n es)"
        apply auto by (simp add: take_Suc_conv_app_nth)
        with esn None suc1 seq seq2 n' show ?thesis by (simp add: take_Suc_conv_app_nth)
      qed
    qed
  next
    case (Some v') then show ?thesis
    proof (cases n)
      case 0
      from suc1 lvs have "verticesFrom f v ≠ []" by auto
      then have "verticesFrom f v = hd (verticesFrom f v) # tl (verticesFrom f v)" by auto
      then have "verticesFrom f v = v # tl (verticesFrom f v)" by (simp add: verticesFrom_hd)
      then obtain z where "verticesFrom f v = v # z" by auto
      then have sub: "sublist (verticesFrom f v) {0} = [v]" by (auto simp: sublist_Cons)
      from 0 suc1 have "es!0 = 0" by (cases es)  auto
      with 0 Some suc1 lvs sub vsne show ?thesis
        by (simp add: take_Suc_conv_app_nth natToVertexList_nth_0 nextVertices_def take_Suc
        sublist_Cons verticesFrom_hd del:verticesFrom_empty)
    next
      case (Suc n')
      with Some suc1 lvs have esn: "es!n ≠ es!n'" by (simp add: natToVertexList_nth_Suc split: split_if_asm)
      from suc1 Suc have "Suc n' < length es" by auto
      with suc1 lvs esn  have "natToVertexList v f es !(Suc n') = Some f(es!(Suc n')) • v"
      apply (simp add: natToVertexList_nth_Suc)
        by (simp add: Suc)
      with Suc have "natToVertexList v f es ! n = Some f(es!n) • v" by auto
      with Some have v': "v' = f(es!n) • v" by simp
      from Suc have n': "n - Suc 0 = n'" by auto
      from suc1 Suc have "es = take (Suc n') es @ es!n # drop (Suc n) es" by (auto intro: id_take_nth_drop)
      with suc1 have  "increasing (take (Suc n') es @ es!n # drop (Suc n) es)" by auto
      with suc1 Suc have "es!n' ≤  es!n" apply (auto intro!: increasing2)
      by (auto simp: take_Suc_conv_app_nth)
      with esn have smaller_n: "es!n' < es!n" by auto
      from suc1 lvs have smaller: "(es!n) < length vs" by auto
      from suc1 smaller lvs have "(verticesFrom f v)!(es!n) =  f(es!n) • v" by (auto intro: verticesFrom_nth)
      with v' have "(verticesFrom f v)!(es!n) = v'" by auto
      then have sub1: "sublist ([((verticesFrom f v)!(es!n))])
          {j. j + (es!n) : (insert (es ! n) (set (take n es)))} = [v']" by auto

      from suc1 smaller lvs have len: "length (take (es ! n) (verticesFrom f v)) = es!n" apply auto by arith

      have "!!x. x ∈ (set (take n es)) ==> x < (es ! n)"
      proof -
        fix x
        assume x: "x ∈ set (take n es)"
        from suc1 Suc have "es = take n' es @ es!n' # drop (Suc n') es" by (auto intro: id_take_nth_drop)
        with suc1 have "increasing (take n' es @ es!n' # drop (Suc n') es)" by auto
        then have "!! x. x ∈ set (take n' es) ==> x ≤ es!n'" by (auto intro!: increasing2)
        with x Suc suc1 have "x ≤ es!n'" by (auto simp: take_Suc_conv_app_nth)
        with smaller_n show "x < es!n" by auto
      qed
      then have "{i. i < es ! n ∧ i ∈ set (take n es)} = (set (take n es))" by auto
      then have elim_insert: "{i. i < es ! n ∧ i ∈ insert (es ! n) (set (take n es))} = (set (take n es))" by auto

      have "sublist (take (es ! n) (verticesFrom f v)) (insert (es ! n) (set (take n es))) =
        sublist (take (es ! n) (verticesFrom f v)) {i. i < length (take (es ! n) (verticesFrom f v))
         ∧ i ∈ (insert (es ! n) (set (take n es)))}" by (rule sublist_reduceIndices)
      with len have "sublist (take (es ! n) (verticesFrom f v)) (insert (es ! n) (set (take n es))) =
        sublist (take (es ! n) (verticesFrom f v)) {i. i < (es ! n) ∧ i ∈ (insert (es ! n) (set (take n es)))}"
        by simp
      with elim_insert have sub2: "sublist (take (es ! n) (verticesFrom f v)) (insert (es ! n) (set (take n es))) =
        sublist (take (es ! n) (verticesFrom f v)) (set (take n es))" by simp

      def m ≡ "es!n - es!n'"
      with smaller_n have mgz: "0 < m" by auto
      with m_def have esn: "es!n = (es!n') + m" by auto

      have helper: "!!x. x ∈ (set (take n es)) ==> x ≤  (es ! n')"
      proof -
        fix x
        assume x: "x ∈ set (take n es)"
        from suc1 Suc have "es = take n' es @ es!n' # drop (Suc n') es" by (auto intro: id_take_nth_drop)
        with suc1 have "increasing (take n' es @ es!n' # drop (Suc n') es)" by auto
        then have "!! x. x ∈ set (take n' es) ==> x ≤ es!n'" by (auto intro!: increasing2)
        with x Suc suc1 show "x ≤ es!n'" by (auto simp: take_Suc_conv_app_nth)
      qed

      def m' ≡ "m - 1"
      def Suc_es_n' ≡ "Suc (es!n')"

      from smaller smaller_n have "Suc (es!n') < length vs" by auto
      then have "min (length vs) (Suc (es ! n')) = Suc (es!n')" by arith
      with Suc_es_n'_def have empty: "{j. j + length (take Suc_es_n' vs) ∈ set (take n es)} = {}"
        apply auto apply (frule helper) by arith


      from Suc_es_n'_def mgz esn m'_def have esn': "es!n = Suc_es_n' + m'" by auto

      with smaller have "(take (Suc_es_n' + m') vs) = take (Suc_es_n') vs @ take m' (drop (Suc_es_n') vs)"
        by (auto intro: take_add)
      with esn' have "sublist (take (es ! n) vs) (set (take n es))
         = sublist (take (Suc_es_n') vs @ take m' (drop (Suc_es_n') vs)) (set (take n es))" by auto
      then have "sublist (take (es ! n) vs) (set (take n es)) =
        sublist (take (Suc_es_n') vs) (set (take n es)) @
        sublist (take m' (drop (Suc_es_n') vs)) {j. j + length (take (Suc_es_n') vs) : (set (take n es))}"
        by (simp add: sublist_append)
      with empty Suc_es_n'_def have "sublist (take (es ! n) vs) (set (take n es)) =
        sublist (take (Suc (es!n')) vs) (set (take n es))" by simp
      with suc1 sub2 have sub3: "sublist (take (es ! n) (verticesFrom f v)) (insert (es ! n) (set (take n es))) =
        sublist (take (Suc (es!n')) (verticesFrom f v)) (set (take n es))" by simp
        
      from smaller suc1 have "take (Suc (es ! n)) (verticesFrom f v)
       = take (es ! n) (verticesFrom f v) @ [((verticesFrom f v)!(es!n))]"
       by (auto simp: take_Suc_conv_app_nth)
      with suc1 smaller have
        "sublist (take (Suc (es ! n)) (verticesFrom f v)) (insert (es ! n) (set (take n es))) =
         sublist (take (es ! n) (verticesFrom f v)) (insert (es ! n) (set (take n es)))
         @ sublist ([((verticesFrom f v)!(es!n))])  {j. j + (es!n) : (insert (es ! n) (set (take n es)))}"
        apply (auto simp: sublist_append) by arith
      with sub1 sub3 have "sublist (take (Suc (es ! n)) (verticesFrom f v)) (insert (es ! n) (set (take n es)))
       = sublist (take (Suc (es ! n')) (verticesFrom f v)) (set (take n es)) @ [v']" by auto
      with Some suc1 lvs n' show ?thesis by (simp add: take_Suc_conv_app_nth)
    qed
  qed
qed

lemma natToVertexList_sublist: "distinct (vertices f) ==> v ∈ \<V> f ==>
  incrIndexList es (length es) (length (vertices f)) ==>
  sublist (verticesFrom f v) (set es) = removeNones (natToVertexList v f es)"
proof -
  assume vors1: "distinct (vertices f)" "v ∈ \<V> f"
     "incrIndexList es (length es) (length (vertices f))"
  def vs ≡ "verticesFrom f v"
  with vors1 have lvs: "length vs = length (vertices f)"  by (auto intro: verticesFrom_length)
  with vors1 vs_def have vors: "distinct (vertices f)" "v ∈ \<V> f"
    "vs = verticesFrom f v"  "incrIndexList es (length es) (length vs)" by auto

  with lvs have vsne: "vs ≠ []" by auto
  def n ≡ "length es"
  then have "es!(n - 1) = last es"
  proof (cases n)
    case 0 with n_def vors show ?thesis by (cases es)  auto
  next
    case (Suc n')
    with n_def have small_n': "n' < length es" by arith
    from Suc n_def have "take (Suc n') es = es" by auto
    with small_n' have "take n' es @ [es!n'] = es" by (simp add: take_Suc_conv_app_nth)
    then have "es!n' = last es" by (cases es rule: rev_exhaust) auto
    with Suc show ?thesis by auto
  qed
  with vors have "es!(n - 1) = (length vs) - 1" by auto
  with vsne have "Suc (es! (n - 1)) = (length vs)" by auto
  then have take_vs: "take (Suc (es!(n - 1))) vs = vs" by auto

  from n_def vors have "n =  length (natToVertexList v f es)" by auto
  then have take_nTVL: "take n (natToVertexList v f es) = natToVertexList v f es" by auto

  from n_def have take_es: "take n es = es" by auto

  from n_def have "n ≤ length es" by auto
  with vors   have "sublist (take (Suc (es!(n - 1))) vs) (set (take n es))
    = removeNones (take n (natToVertexList v f es))" by (rule natToVertexList_sublist1)
  with take_vs take_nTVL take_es vs_def show ?thesis by simp
qed


lemma filter_Cons2:
 "x ∉ set ys ==> [y ∈ ys.  y = x ∨ P y] = [y ∈ ys. P y]"
 by (induct ys) (auto)

lemma natToVertexList_removeNones:
  "distinct (vertices f) ==> v ∈ \<V> f ==>
  incrIndexList es (length es) (length (vertices f)) ==>
  [x ∈ verticesFrom f v. x ∈ set (removeNones (natToVertexList v f es))]
 = removeNones (natToVertexList v f es)"
proof -
  assume vors: "distinct (vertices f)" "v ∈ \<V> f"
    "incrIndexList es (length es) (length (vertices f))"
  then have dist: "distinct (verticesFrom f v)" by auto
  from vors have sub_eq: "sublist (verticesFrom f v) (set es)
    = removeNones (natToVertexList v f es)" by (rule natToVertexList_sublist)
  from dist have "[x ∈ verticesFrom f v.
    x ∈ set (sublist (verticesFrom f v) (set es))] = removeNones (natToVertexList v f es)"
  apply (simp add: filter_in_sublist)
    by (simp add: sub_eq)
  with sub_eq show ?thesis by simp
qed

lemma indexToVertexList_removeNones:
  "distinct (vertices f) ==> v ∈ \<V> f ==>
  incrIndexList es (length es) (length (vertices f)) ==>
  [x ∈ verticesFrom f v. x ∈ set (removeNones (indexToVertexList f v es))]
 = removeNones (indexToVertexList f v es)"
apply (subgoal_tac "indexToVertexList f v es = natToVertexList v f es")
 apply simp apply (rule natToVertexList_removeNones) apply assumption+
apply (rule indexToVertexList_natToVertexList_eq) apply (simp_all) by auto


(**************************** invalidVertexList ************)

constdefs is_duplicateEdge :: "graph => face => vertex => vertex => bool"
 "is_duplicateEdge g f a b ≡
   ((a, b) ∈ edges g ∧ (a, b) ∉ edges f ∧ (b, a) ∉ edges f)
 ∨ ((b, a) ∈ edges g ∧ (b, a) ∉ edges f ∧ (a, b) ∉ edges f)"

constdefs invalidVertexList :: "graph => face => vertex option list => bool"
 "invalidVertexList g f vs ≡
     ∃i < |vs|- 1.
         case vs!i of None => False
             | Some a => case vs!(i+1) of None => False
             | Some b => is_duplicateEdge g f a b"


(**************************** subdivFace **********************)

subsection {* @{text"pre_subdivFace(')"} *}

constdefs pre_subdivFace_face :: "face => vertex => vertex option list => bool"
"pre_subdivFace_face f v' vOptionList ≡
     [v ∈ verticesFrom f v'. v ∈ set (removeNones vOptionList)]
       = (removeNones vOptionList)
  ∧ ¬ final f ∧ distinct (vertices f)
  ∧ hd (vOptionList) = Some v'
  ∧ v' ∈ \<V> f
  ∧ last (vOptionList) =  Some (last (verticesFrom f v'))
  ∧ hd (tl (vOptionList)) ≠ last (vOptionList)
  ∧ 2 < | vOptionList |
  ∧ vOptionList ≠  []
  ∧ tl (vOptionList) ≠ []"

constdefs pre_subdivFace :: "graph => face => vertex => vertex option list => bool"
"pre_subdivFace g f v' vOptionList ≡
  pre_subdivFace_face f v' vOptionList ∧ ¬ invalidVertexList g f vOptionList"

(* zu teilende Fläche, ursprüngliches v, erster Ram-Punkt, Anzahl der überlaufenen NOnes, rest der vol *)
constdefs pre_subdivFace' :: "graph => face => vertex => vertex => nat => vertex option list => bool"
"pre_subdivFace' g f v' ram1 n vOptionList ≡
  ¬ final f ∧ v' ∈ \<V> f ∧ ram1 ∈ \<V> f
  ∧ v' ∉ set (removeNones vOptionList)
  ∧ distinct (vertices f)
  ∧ (
    [v ∈ verticesFrom f v'. v ∈ set (removeNones vOptionList)]
        =  (removeNones vOptionList)
  ∧ before (verticesFrom f v') ram1 (hd (removeNones vOptionList))
  ∧ last (vOptionList) =  Some (last (verticesFrom f v'))
  ∧ vOptionList ≠  []
  ∧ ((v' = ram1 ∧ (0 < n)) ∨ ((v' = ram1 ∧ (hd (vOptionList) ≠ Some (last (verticesFrom f v'))))  ∨ (v' ≠ ram1)))
  ∧ ¬ invalidVertexList g f vOptionList
  ∧ (n = 0 ∧ hd (vOptionList) ≠ None -->  ¬ is_duplicateEdge g f ram1 (the (hd (vOptionList))))
  ∨ (vOptionList = [] ∧ v' ≠ ram1)
  )"


lemma pre_subdivFace_face_in_f[intro]: "pre_subdivFace_face f v ls ==> Some a ∈ set ls ==> a ∈ set (verticesFrom f v)"
  apply (subgoal_tac "a ∈ set (removeNones ls)") apply (auto  simp: pre_subdivFace_face_def)
  apply (subgoal_tac "a ∈ set [v∈verticesFrom f v . v ∈ set (removeNones ls)]")
  apply (thin_tac "[v∈verticesFrom f v . v ∈ set (removeNones ls)] = removeNones ls") by auto

lemma pre_subdivFace_in_f[intro]: "pre_subdivFace g f v ls ==> Some a ∈ set ls ==> a ∈ set (verticesFrom f v)"
 by (auto simp: pre_subdivFace_def)


lemma pre_subdivFace_face_in_f'[intro]: "pre_subdivFace_face f v ls ==> Some a ∈ set ls ==> a ∈ \<V> f"
  apply (cases "a = v") apply (force simp: pre_subdivFace_face_def)
 apply (rule verticesFrom_in') apply (rule pre_subdivFace_face_in_f)
by auto




lemma hilf1: "a ∈ set b ==> (v = a ∨ v ∈ set b) = (v ∈ set b)" by auto

lemma filter_congs_shorten1': "distinct (vertices f) ==> [v∈vertices f . v = a ∨ v ∈ set vs] ≅ (a # vs)
    ==> [v∈vertices f . v ∈ set vs] ≅ vs"
proof -
  assume dist: "distinct (vertices f)" and "[v∈vertices f . v = a ∨ v ∈ set vs] ≅ (a # vs)"
  then obtain n where removeNones_vol: "a # vs = rotate n [v∈vertices f . v = a ∨ v ∈ set vs]"
    by (auto simp: congs_def)
  have "∃ m. rotate n [v∈vertices f . v = a ∨ v ∈ set vs] = [v∈(rotate m (vertices f)) . v = a ∨ v ∈ set vs]"
    by (auto intro: rotate_help6) (* rotate_help6 *)
  then obtain m where " rotate n [v∈vertices f . v = a ∨ v ∈ set vs]
     = [v∈(rotate m (vertices f)) . v = a ∨ v ∈ set vs]" by auto
  with removeNones_vol have a_removeNones_vol: "[v∈(rotate m (vertices f)) . v = a ∨ v ∈ set vs] = a # vs" by simp

  have rule1: "!! vs a ys. distinct vs ==> [v∈vs . v = a ∨ v ∈ set ys] = a # ys ==>
    [v ∈ vs. v ∈ set ys] = ys"
  proof -
    fix vs a ys
    assume dist: "distinct vs" and ays:  "[v∈vs . v = a ∨ v ∈ set ys] = a # ys"
    then have "distinct ([v∈vs . v = a ∨ v ∈ set ys])" by (rule_tac distinct_filter)
    with ays have distys: "distinct (a # ys)" by simp
    from dist distys ays show "[v ∈ vs. v ∈ set ys] = ys"
      apply (induct vs) by (auto  split: split_if_asm simp: filter_Cons2)
  qed

  from dist have "distinct (rotate m (vertices f))" by auto
  with a_removeNones_vol have "[v ∈ (rotate m (vertices f)). v ∈ set vs] = vs" by (rule_tac rule1)
  also have "∃ l. [v ∈ (rotate m (vertices f)). v ∈ set vs] = rotate l [v ∈ vertices f. v ∈ set vs]"
    by (rule  rotate_help5) (* rotate_help5 *)
  then obtain l where "[v ∈ (rotate m (vertices f)). v ∈ set vs] = rotate l [v ∈ vertices f. v ∈ set vs]" by auto
  ultimately have "vs = rotate l [v∈vertices f . v ∈ set vs]" by simp
  thus ?thesis by (auto simp: congs_def)
qed

lemma filter_congs_shorten1: "distinct (verticesFrom f v) ==> [v∈verticesFrom f v . v = a ∨ v ∈ set vs] = (a # vs)
    ==> [v∈verticesFrom f v . v ∈ set vs] = vs"
proof -
  assume dist: "distinct (verticesFrom f v)" and eq: "[v∈verticesFrom  f v . v = a ∨ v ∈ set vs] = (a # vs)"
  have rule1: "!! vs a ys. distinct vs ==> [v∈vs . v = a ∨ v ∈ set ys] = a # ys ==> [v ∈ vs. v ∈ set ys] = ys"
  proof -
    fix vs a ys
    assume dist: "distinct vs" and ays:  "[v∈vs . v = a ∨ v ∈ set ys] = a # ys"
    then have "distinct ([v∈vs . v = a ∨ v ∈ set ys])" by (rule_tac distinct_filter)
    with ays have distys: "distinct (a # ys)" by simp
    from dist distys ays show "[v ∈ vs. v ∈ set ys] = ys"
     apply (induct vs) by (auto  split: split_if_asm simp: filter_Cons2)
  qed

  from dist eq show ?thesis  by (rule_tac rule1)
qed

lemma ovl_shorten': "distinct (vertices f) ==> [v∈vertices f . v ∈ set (removeNones (va # vol))] ≅ (removeNones (va # vol))
    ==> [v∈vertices f . v ∈ set (removeNones (vol))] ≅ (removeNones (vol))"
proof -
  assume dist: "distinct (vertices f)" and vors: "[v∈vertices f . v ∈ set (removeNones (va # vol))] ≅ (removeNones (va # vol))"
  then show ?thesis
  proof (cases va)
    case None with vors Cons show ?thesis by auto
  next
    case (Some a) with vors dist show ?thesis by (auto intro!: filter_congs_shorten1')
  qed
qed

lemma ovl_shorten: "distinct (verticesFrom f v) ==>
  [v∈verticesFrom f v . v ∈ set (removeNones (va # vol))] = (removeNones (va # vol))
    ==> [v∈verticesFrom f v . v ∈ set (removeNones (vol))] =  (removeNones (vol))"
proof -
  assume dist: "distinct (verticesFrom f v)"
  and vors: "[v∈verticesFrom f v . v ∈ set (removeNones (va # vol))] = (removeNones (va # vol))"
  then show ?thesis
  proof (cases va)
    case None with vors Cons show ?thesis by auto
  next
    case (Some a) with vors dist show ?thesis by (auto intro!: filter_congs_shorten1)
  qed
qed

lemma pre_subdivFace_face_distinct: "pre_subdivFace_face f v vol ==> distinct (removeNones vol)"
  apply (auto dest!: verticesFrom_distinct simp: pre_subdivFace_face_def)
  apply (subgoal_tac "distinct ([v∈verticesFrom f v . v ∈ set (removeNones vol)])") apply simp
  apply (thin_tac "[v∈verticesFrom f v . v ∈ set (removeNones vol)] = removeNones vol") by auto

lemma pre_subdivFace_face_not_empty: "pre_subdivFace_face f v (vo # vol) ==> vol ≠ []"
  by (simp split: split_if_asm add: pre_subdivFace_face_def)

lemma invalidVertexList_shorten: "invalidVertexList g f vol ==> invalidVertexList g f (v # vol)"
apply (simp add: invalidVertexList_def) apply auto apply (rule exI) apply safe
apply (subgoal_tac "(Suc i) < | vol |") apply assumption apply arith
apply auto apply (case_tac "vol!i") by auto

lemma edges_in_faces_in_graph: "x ∈ edges f ==> f ∈ \<F> g ==> x ∈ edges g"
  apply (simp add: edges_graph_def) by auto

lemma pre_subdivFace_pre_subdivFace': "v ∈ \<V> f ==> pre_subdivFace g f v (vo # vol) ==>
  pre_subdivFace' g f v v 0 (vol)"
proof -
  assume vors:  "v ∈ \<V> f"  "pre_subdivFace g f v (vo # vol)"
  then have vors': "v ∈ \<V> f" "pre_subdivFace_face f v (vo # vol)" "¬ invalidVertexList g f (vo # vol)"
    by (auto simp: pre_subdivFace_def)
  then have r: "removeNones vol ≠ []" apply (cases "vol" rule: rev_exhaust) by  (auto  simp: pre_subdivFace_face_def)
  then have "Some (hd (removeNones vol)) ∈ set vol" apply (induct vol) apply auto apply (case_tac a) by auto
  then have "Some (hd (removeNones vol)) ∈ set (vo # vol)" by auto
  with vors' have hd: "hd (removeNones vol) ∈ \<V> f" by (rule_tac pre_subdivFace_face_in_f')

  from vors' have "Some v = vo" by (auto  simp: pre_subdivFace_face_def)
  with vors'  have "v ∉ set (tl (removeNones (vo # vol)))" apply (drule_tac pre_subdivFace_face_distinct) by auto
  with vors' r have ne: "v ≠ hd (removeNones vol)" by (cases  "removeNones vol")  (auto  simp: pre_subdivFace_face_def)

  from vors' have dist: "distinct (removeNones (vo # vol))"  apply (rule_tac pre_subdivFace_face_distinct) .

  from vors' have invalid: "¬ invalidVertexList g f vol" by (auto simp: invalidVertexList_shorten)


  from ne hd vors' invalid dist show ?thesis apply (unfold pre_subdivFace'_def)
    apply (simp add: pre_subdivFace'_def pre_subdivFace_face_def)
    apply safe
        apply (rule ovl_shorten)
         apply (simp add: pre_subdivFace_face_def) apply assumption
       apply (rule before_verticesFrom)
          apply simp+
    apply (simp add: invalidVertexList_def)
    apply (erule allE)
    apply (erule impE)
    apply (subgoal_tac "0 <  |vol|")
      apply (thin_tac "Suc 0 < | vol |")
      apply  assumption
     apply simp
    apply (simp)
    apply (case_tac "vol") apply simp by (simp add: is_duplicateEdge_def)
qed


lemma pre_subdivFace'_distinct: "pre_subdivFace' g f v' v n vol ==> distinct (removeNones vol)"
  apply (unfold pre_subdivFace'_def)
  apply (cases vol) apply simp+
  apply (elim conjE)
  apply (drule_tac verticesFrom_distinct) apply assumption
  apply (subgoal_tac "distinct [v∈verticesFrom f v' . v ∈ set (removeNones (a # list))]") apply force
  apply (thin_tac "[v∈verticesFrom f v' . v ∈ set (removeNones (a # list))] = removeNones (a # list)")
  by auto


lemma natToVertexList_pre_subdivFace_face:
 "¬ final f ==> distinct (vertices f) ==> v ∈ \<V> f ==> 2 < |es| ==>
 incrIndexList es (length es) (length (vertices f)) ==>
 pre_subdivFace_face f v (natToVertexList v f es)"
proof -
  assume vors: "¬ final f" "distinct (vertices f)" "v ∈ \<V> f" "2 < |es|"
     "incrIndexList es (length es) (length (vertices f))"
  then have lastOvl: "last (natToVertexList v f es) =  Some (last (verticesFrom f v))" by auto

  from vors have nvl_l: "2 < | natToVertexList v f es |"
    by auto

  from vors have "distinct [x∈verticesFrom f v . x ∈ set (removeNones (natToVertexList v f es))]" by auto
  with vors have "distinct (removeNones (natToVertexList v f es))" by (simp add: natToVertexList_removeNones)
  with nvl_l lastOvl have hd_last: "hd (tl (natToVertexList v f es)) ≠ last (natToVertexList v f es)" apply auto
    apply (cases "natToVertexList v f es") apply simp
    apply (case_tac "list" rule: rev_exhaust) apply simp
    apply (case_tac "ys") apply simp
    apply (case_tac "a") apply simp by simp

  from vors lastOvl hd_last nvl_l show ?thesis
    apply (auto intro: natToVertexList_removeNones simp: pre_subdivFace_face_def)
    apply (cases es) apply auto
    apply (cases es) apply auto
    apply (subgoal_tac "0 < length list") apply (case_tac list) by (auto split: split_if_asm)
qed


lemma indexToVertexList_pre_subdivFace_face:
 "¬ final f ==> distinct (vertices f) ==> v ∈ \<V> f ==> 2 < |es| ==>
 incrIndexList es (length es) (length (vertices f)) ==>
 pre_subdivFace_face f v (indexToVertexList f v es)"
apply (subgoal_tac "indexToVertexList f v es = natToVertexList v f es") apply simp
apply (rule natToVertexList_pre_subdivFace_face) apply assumption+
apply (rule indexToVertexList_natToVertexList_eq) by auto

lemma subdivFace_subdivFace'_eq: "pre_subdivFace g f v vol ==>  subdivFace g f vol = subdivFace' g f v 0 (tl vol)"
by (simp_all add: subdivFace_def pre_subdivFace_def pre_subdivFace_face_def)

lemma pre_subdivFace'_None:
 "pre_subdivFace' g f v' v n (None # vol) ==>
  pre_subdivFace' g f v' v (Suc n) vol"
by(auto simp: pre_subdivFace'_def dest:invalidVertexList_shorten
        split:split_if_asm)

declare verticesFrom_between [simp del]


(* zu zeigen:
 1. vol ≠ [] ==> [v∈verticesFrom f21 v' . v ∈ set (removeNones vol)] = removeNones vol
 2. vol ≠ [] ==> before (verticesFrom f21 v') u (hd (removeNones vol))
 3. vol ≠ [] ==> distinct (vertices f21)
 4. vol ≠ [] ==> last vol = Some (last (verticesFrom f21 v'))
*)

lemma verticesFrom_split: "v # tl (verticesFrom f v) = verticesFrom f v" by (auto simp: verticesFrom_Def)

lemma verticesFrom_v: "distinct (vertices f) ==> vertices f = a @ v # b ==> verticesFrom f v = v # b @ a"
by (simp add: verticesFrom_Def)


lemma splitAt_fst[simp]: "distinct xs ==> xs = a @ v # b ==> fst (splitAt v xs) = a"
by auto

lemma splitAt_snd[simp]: "distinct xs ==> xs = a @ v # b ==> snd (splitAt v xs) = b"
by auto

lemma verticesFrom_splitAt_v_fst[simp]:
  "distinct (verticesFrom f v) ==> fst (splitAt v (verticesFrom f v)) = []"
  by (simp add: verticesFrom_Def)
lemma verticesFrom_splitAt_v_snd[simp]:
  "distinct (verticesFrom f v) ==> snd (splitAt v (verticesFrom f v)) = tl (verticesFrom f v)"
  by (simp add: verticesFrom_Def)


lemma filter_distinct_at:
  "distinct xs ==> xs = (as @ u # bs) ==> [v ∈ xs. v = u ∨ P v] = u # us ==>
  [v ∈ bs. P v] = us ∧ [v ∈ as. P v] = []"
apply (subgoal_tac "filter P as @ u # filter P bs = [] @ u # us")
apply (drule local_help')  by (auto simp: filter_Cons2)

lemma filter_distinct_at2: "distinct xs ==> xs = (as @ u # bs) ==>
  [v ∈ xs. v = u ∨ P v] = u # us ==> filter P zs = [] ==> [v ∈ zs@bs. P v] = us"
  apply (drule filter_distinct_at) apply assumption+ by simp

lemma filter_distinct_at3: "distinct xs ==> xs = (as @ u # bs) ==>
  [v ∈ xs. v = u ∨ P v] = u # us ==> ∀ z ∈ set zs. z ∈ set as ∨ ¬ ( P z) ==>
  [v ∈ zs@bs. P v] = us"
apply (drule filter_distinct_at) apply assumption+ apply simp
by (induct zs) auto

lemma filter_distinct_at4: "distinct xs ==> xs = (as @ u # bs)
  ==> [v ∈ xs. v = u ∨ v ∈ set us] = u # us
  ==> set zs ∩ set us ⊆ {u} ∪ set as
  ==> [v ∈ zs@bs. v ∈ set us] = us"
proof -
  assume vors: "distinct xs" "xs = (as @ u # bs)"
    "[v ∈ xs. v = u ∨ v ∈ set us] = u # us"
    "set zs ∩ set us ⊆ {u} ∪ set as"
  then have "distinct ([v ∈ xs. v = u ∨ v ∈ set us])"  apply (rule_tac distinct_filter) by simp
  with vors have dist: "distinct (u # us)" by auto
  with vors show ?thesis
  apply (rule_tac filter_distinct_at3) by assumption+  auto
qed

lemma filter_distinct_at5: "distinct xs ==> xs = (as @ u # bs)
  ==> [v ∈ xs. v = u ∨ v ∈ set us] = u # us
  ==> set zs ∩ set xs ⊆ {u} ∪ set as
  ==> [v ∈ zs@bs. v ∈ set us] = us"
proof -
  assume vors: "distinct xs" "xs = (as @ u # bs)"
    "[v ∈ xs. v = u ∨ v ∈ set us] = u # us"
    "set zs ∩ set xs ⊆ {u} ∪ set as"
  have "set ([v ∈ xs. v = u ∨ v ∈ set us]) ⊆ set xs" by auto
  with vors have "set (u # us) ⊆ set xs" by simp
  then have "set us ⊆ set xs" by simp
  with vors have "set zs ∩ set us ⊆ set zs ∩ insert u (set as ∪ set bs)" by auto
  with vors show ?thesis apply (rule_tac filter_distinct_at4) apply assumption+ by auto
qed

lemma filter_distinct_at6: "distinct xs ==> xs = (as @ u # bs)
  ==> [v ∈ xs. v = u ∨ v ∈ set us] = u # us
  ==> set zs ∩ set xs ⊆ {u} ∪ set as
  ==> [v ∈ zs@bs. v ∈ set us] = us ∧ [v ∈ bs. v ∈ set us] = us"
proof -
  assume vors: "distinct xs" "xs = (as @ u # bs)"
    "[v ∈ xs. v = u ∨ v ∈ set us] = u # us"
    "set zs ∩ set xs ⊆ {u} ∪ set as"
  then show ?thesis apply (rule_tac conjI)  apply (rule_tac filter_distinct_at5) apply assumption+
  apply (drule filter_distinct_at) apply assumption+ by auto
qed

lemma filter_distinct_at_special:
  "distinct xs ==> xs = (as @ u # bs)
  ==> [v ∈ xs. v = u ∨ v ∈ set us] = u # us
  ==> set zs ∩ set xs ⊆ {u} ∪ set as
  ==> us = hd_us # tl_us
  ==> [v ∈ zs@bs. v ∈ set us] = us ∧ hd_us ∈ set bs"
proof -
  assume vors: "distinct xs" "xs = (as @ u # bs)"
    "[v ∈ xs. v = u ∨ v ∈ set us] = u # us"
    "set zs ∩ set xs ⊆ {u} ∪ set as"
    "us = hd_us # tl_us"
  then have "[v ∈ zs@bs. v ∈ set us] = us ∧ [v ∈ bs. v ∈ set us] = us"
    by (rule_tac filter_distinct_at6)
  with vors show ?thesis apply (rule_tac conjI) apply safe apply simp
    apply (subgoal_tac "set (hd_us # tl_us) ⊆ set bs") apply simp
    apply (subgoal_tac "set [v∈bs . v = hd_us ∨ v ∈ set tl_us] ⊆ set bs")  apply simp
    by (rule_tac filter_is_subset)
qed




(* später ggf. pre_splitFace eliminieren *)
(* nein, Elimination nicht sinnvoll *)
lemma pre_subdivFace'_Some1':
assumes pre_add: "pre_subdivFace' g f v' v n ((Some u) # vol)"
    and pre_fdg: "pre_splitFace g v u f ws"
    and fdg:  "f21 = fst (snd (splitFace g v u f ws))"
    and g': "g' =  snd (snd (splitFace g v u f ws))"
shows "pre_subdivFace' g' f21 v' u 0 vol"
proof (cases "vol = []")
  case True then show ?thesis using pre_add fdg pre_fdg
    apply(unfold pre_subdivFace'_def pre_splitFace_def)
    apply (simp add: splitFace_def split_face_def split_def del:distinct.simps)
    apply (rule conjI)
     apply(clarsimp)
     apply(rule before_between)
        apply(erule (5) rotate_before_vFrom)
     apply(erule not_sym)
    apply (clarsimp simp:between_distinct between_not_r1 between_not_r2)
    apply(blast dest:inbetween_inset)
    done
next
  case False
  with pre_add
  have "removeNones vol ≠ []" apply (cases "vol" rule: rev_exhaust) by (auto simp: pre_subdivFace'_def)
  then have removeNones_split: "removeNones vol = hd (removeNones vol) # tl (removeNones vol)" by auto


  from pre_add have dist: "distinct (removeNones ((Some u) # vol))" by (rule_tac pre_subdivFace'_distinct)

  from pre_add have v': "v' ∈ \<V> f" by (auto simp: pre_subdivFace'_def)
  hence "(vertices f) ≅ (verticesFrom f v')" by (rule verticesFrom_congs)
  hence set_eq: "set (verticesFrom f v') = \<V> f"
     apply (rule_tac sym) by (rule congs_pres_nodes)

  from pre_fdg fdg have dist_f21: "distinct (vertices f21)" by auto

  from pre_add have pre_bet': "pre_between (verticesFrom f v') u v"
    apply (simp add: pre_between_def pre_subdivFace'_def)
    apply (elim conjE) apply (thin_tac "n = 0 --> ¬ is_duplicateEdge g f v u")
    apply (thin_tac "v' = v ∧ 0 < n ∨ v' = v ∧ u ≠ last (verticesFrom f v') ∨ v' ≠ v")
    apply (auto simp add: before_def)
    apply (subgoal_tac "distinct (verticesFrom f v')")  apply simp
    apply (rule_tac verticesFrom_distinct) by auto

  with pre_add have pre_bet: "pre_between (vertices f) u v"
    apply (subgoal_tac "(vertices f) ≅ (verticesFrom f v')")
     apply (simp add: pre_between_def pre_subdivFace'_def)
    by (auto dest: congs_pres_nodes intro: verticesFrom_congs simp: pre_subdivFace'_def)

   from pre_bet pre_add have bet_eq[simp]: "between (vertices f) u v = between (verticesFrom f v') u v"
    by (auto intro: verticesFrom_between simp: pre_subdivFace'_def)

  from fdg have f21_split_face: "f21 = snd (split_face f v u ws)"
    by (simp add: splitFace_def split_def)
  then have f21: "f21 = Face (u # between (vertices f) u v @ v # ws) Nonfinal"
    by (simp add: split_face_def)
  with pre_add pre_bet'
  have vert_f21: "vertices f21
   = u # snd (splitAt u (verticesFrom f v')) @ fst (splitAt v (verticesFrom f v')) @ v # ws"
    apply (drule_tac pre_between_symI)
    by (auto simp: pre_subdivFace'_def between_simp2 intro: pre_between_symI)

  moreover
  from pre_add have "v ∈ set (verticesFrom f v')" by (auto simp: pre_subdivFace'_def before_def)
  then have "verticesFrom f v' =
   fst (splitAt v (verticesFrom f v')) @ v # snd (splitAt v (verticesFrom f v'))"
   by (auto dest: splitAt_ram)
  then have m: "v' # tl (verticesFrom f v')
    =  fst (splitAt v (verticesFrom f v')) @ v # snd (splitAt v (verticesFrom f v'))"
    by (simp add: verticesFrom_split)

  then have vv': "v ≠ v' ==> fst (splitAt v (verticesFrom f v'))
    = v' # tl (fst (splitAt v (verticesFrom f v')))"
   by (cases "fst (splitAt v (verticesFrom f v'))") auto

  ultimately have "v ≠ v' ==> vertices f21
    = u # snd (splitAt u (verticesFrom f v')) @ v' # tl (fst (splitAt v (verticesFrom f v'))) @ v # ws"
    by auto

  moreover
  with f21 have rule2: "v' ∈ \<V> f21" by auto
  with dist_f21 have dist_f21_v': "distinct (verticesFrom f21 v')" by auto

  ultimately have m1: "v ≠ v' ==> verticesFrom f21 v'
     = v' # tl (fst (splitAt v (verticesFrom f v'))) @ v # ws @ u # snd (splitAt u (verticesFrom f v'))"
    apply auto
    apply (subgoal_tac "snd (splitAt v' (vertices f21)) = tl (fst (splitAt v (verticesFrom f v'))) @ v # ws")
     apply (subgoal_tac "fst (splitAt v' (vertices f21)) = u # snd (splitAt u (verticesFrom f v'))")
      apply (subgoal_tac "verticesFrom f21 v' = v' # snd (splitAt v' (vertices f21)) @ fst (splitAt v' (vertices f21))")
       apply simp
      apply (intro verticesFrom_v dist_f21) apply force
     apply (subgoal_tac "distinct (vertices f21)") apply simp
     apply (rule_tac dist_f21)
    apply (subgoal_tac "distinct (vertices f21)") apply simp
    by (rule_tac dist_f21)

  from pre_add have dist_vf_v': "distinct (verticesFrom f v')" by (simp add: pre_subdivFace'_def)
  with  vert_f21 have m2: "v = v' ==> verticesFrom f21 v' = v' # ws @ u # snd (splitAt u (verticesFrom f v'))"
    apply auto apply (intro verticesFrom_v dist_f21) by simp

  from pre_add have u: "u ∈ set (verticesFrom f v')" by (fastsimp simp: pre_subdivFace'_def before_def)
  then have split_u: "verticesFrom f v'
    = fst (splitAt u (verticesFrom f v')) @ u # snd (splitAt u (verticesFrom f v'))"
    by (auto dest!: splitAt_ram)

  then have rule1': "[v∈snd (splitAt u (verticesFrom f v')) . v ∈ set (removeNones vol)] = removeNones vol"
  proof -
    from split_u have "v' # tl (verticesFrom f v')
       =  fst (splitAt u (verticesFrom f v')) @ u # snd (splitAt u (verticesFrom f v'))"
      by (simp add: verticesFrom_split)
    have help: "set [] ∩ set (verticesFrom f v') ⊆ {u} ∪ set (fst (splitAt u (verticesFrom f v')))" by auto
    from split_u  dist_vf_v'  pre_add
    have "[v∈ [] @ snd (splitAt u (verticesFrom f v')) . v ∈ set (removeNones vol)] = removeNones vol"
      apply (rule_tac filter_distinct_at5) apply assumption+
      apply (simp add: pre_subdivFace'_def) by (rule help)
    then show ?thesis by auto
  qed
  then have inSnd_u: "!! x. x ∈ set (removeNones vol) ==> x ∈ set (snd (splitAt u (verticesFrom f v')))"
    apply (subgoal_tac "x ∈ set [v∈snd (splitAt u (verticesFrom f v')) . v ∈ set (removeNones vol)] ==>
      x ∈ set (snd (splitAt u (verticesFrom f v')))")
    apply force apply (thin_tac "[v∈snd (splitAt u (verticesFrom f v')) . v ∈ set (removeNones vol)] = removeNones vol")
    by simp

  from split_u dist_vf_v' have notinFst_u: "!! x. x ∈ set (removeNones vol) ==>
      x ∉ set ((fst (splitAt u (verticesFrom f v'))) @ [u])" apply (drule_tac inSnd_u)
    apply (subgoal_tac "distinct ( fst (splitAt u (verticesFrom f v')) @ u # snd (splitAt u (verticesFrom f v')))")
    apply (thin_tac "verticesFrom f v'
       = fst (splitAt u (verticesFrom f v')) @ u # snd (splitAt u (verticesFrom f v'))")
    apply simp apply safe
    apply (subgoal_tac "x ∈ set (fst (splitAt u (verticesFrom f v'))) ∩ set (snd (splitAt u (verticesFrom f v')))")
    apply simp
    apply (thin_tac "set (fst (splitAt u (verticesFrom f v'))) ∩ set (snd (splitAt u (verticesFrom f v'))) = {}")
    apply simp
    by (simp only:)

  from rule2 v' have "!! a b. is_nextElem (vertices f) a b ∧ a ∈ set (removeNones vol) ∧ b ∈ set (removeNones vol)  ==>
   is_nextElem (vertices f21) a b"
  proof -
    fix a b
    assume vors: "is_nextElem (vertices f) a b ∧ a ∈ set (removeNones vol) ∧ b ∈ set (removeNones vol)"
    def vor_u ≡ "fst (splitAt u (verticesFrom f v'))"
    def nach_u ≡ "snd (splitAt u (verticesFrom f v'))"
    from vors v' have "is_nextElem (verticesFrom f v') a b"  by (simp add: verticesFrom_is_nextElem)
    moreover
    from vors inSnd_u nach_u_def have "a ∈ set (nach_u)" by auto
    moreover
    from vors inSnd_u nach_u_def have "b ∈ set (nach_u)" by auto
    moreover
    from split_u vor_u_def nach_u_def have "verticesFrom f v' = vor_u @ u # nach_u" by auto
    moreover
    note dist_vf_v'
    ultimately have "is_sublist [a,b] (nach_u)" apply (simp add: is_nextElem_def split:split_if_asm)
      apply (subgoal_tac "b ≠ hd (vor_u @ u # nach_u)")
       apply simp
       apply (subgoal_tac "distinct (vor_u @ (u # nach_u))")
        apply (drule is_sublist_at5)
         apply simp
        apply simp
        apply (erule disjE)
         apply (drule is_sublist_in1)+
         apply (subgoal_tac "b ∈ set vor_u ∩ set nach_u") apply simp
         apply (thin_tac "set vor_u ∩ set nach_u = {}")
         apply simp
        apply (erule disjE)
         apply (subgoal_tac "distinct ([u] @ nach_u)")
          apply (drule is_sublist_at5)
           apply simp
          apply simp
          apply (erule disjE)
           apply simp
          apply simp
         apply simp
        apply (subgoal_tac "distinct (vor_u @ (u # nach_u))")
         apply (drule is_sublist_at5) apply simp
        apply (erule disjE)
         apply (drule is_sublist_in1)+
         apply simp
        apply (erule disjE)
         apply  (drule is_sublist_in1)+ apply simp
        apply simp
       apply simp
      apply simp
     apply (cases "vor_u") by auto

    with nach_u_def have "is_sublist [a,b] (snd (splitAt u (verticesFrom f v')))" by auto
    then have "is_sublist [a,b] (verticesFrom f21 v')"
      apply (cases "v = v'") apply (simp_all add: m1 m2)
      apply (subgoal_tac "is_sublist [a, b] ((v' # ws @ [u]) @ snd (splitAt u (verticesFrom f v')) @ [])")
      apply simp apply (rule is_sublist_add) apply simp
      apply (subgoal_tac "is_sublist [a, b]
       ((v' # tl (fst (splitAt v (verticesFrom f v'))) @ v # ws @ [u]) @ (snd (splitAt u (verticesFrom f v'))) @ [])")
      apply simp apply (rule is_sublist_add) by simp
    with rule2 show "is_nextElem (vertices f) a b ∧ a ∈ set (removeNones vol) ∧ b ∈ set (removeNones vol)  ==>
      is_nextElem (vertices f21) a b" apply (simp add: verticesFrom_is_nextElem) by (auto simp: is_nextElem_def)
  qed
  with pre_add dist_f21 have rule5':
     "!! a b. (a,b) ∈ edges f ∧ a ∈ set (removeNones vol) ∧ b ∈ set (removeNones vol) ==> (a, b) ∈ edges f21"
    by (simp add:  is_nextElem_edges_eq pre_subdivFace'_def)


  have rule1: "[v∈verticesFrom f21 v' . v ∈ set (removeNones vol)]
    = removeNones vol ∧ hd (removeNones vol) ∈ set (snd (splitAt u (verticesFrom f v')))"
  proof (cases "v = v'")
    case True
    from split_u have "v' # tl (verticesFrom f v')
      =  fst (splitAt u (verticesFrom f v')) @ u # snd (splitAt u (verticesFrom f v'))"
      by (simp add: verticesFrom_split)
    then have "u ≠ v' ==> fst (splitAt u (verticesFrom f v'))
      = v' # tl (fst (splitAt u (verticesFrom f v')))" by (cases "fst (splitAt u (verticesFrom f v'))") auto
    moreover
    have "v' ∈ set (v' # tl (fst (splitAt u (verticesFrom f v'))))" by simp
    ultimately have "u ≠ v' ==> v' ∈ set (fst (splitAt u (verticesFrom f v')))" by simp
    moreover
    from pre_fdg have "set (v' # ws @ [u]) ∩ set (verticesFrom f v') ⊆  {v', u}"
      apply (simp add: set_eq)
      by (unfold pre_splitFace_def) auto
    ultimately have help: "set (v' # ws @ [u]) ∩ set (verticesFrom f v')
      ⊆ {u} ∪ set (fst (splitAt u (verticesFrom f v')))" apply (rule_tac subset_trans)
      apply assumption apply (cases "u = v'") by simp_all
    from split_u dist_vf_v' pre_add pre_fdg removeNones_split have
      "[v∈ (v' # ws @ [u]) @ snd (splitAt u (verticesFrom f v')) . v ∈ set (removeNones vol)]
      = removeNones vol ∧ hd (removeNones vol) ∈ set (snd (splitAt u (verticesFrom f v')))"
      apply (rule_tac filter_distinct_at_special) apply assumption+
      apply (simp add: pre_subdivFace'_def) apply (rule help) .
    with True m2 show ?thesis by auto
  next
    case False

    with m1 dist_f21_v' have ne_uv': "u ≠ v'" by auto
    def fst_u ≡  "fst (splitAt u (verticesFrom f v'))"
    def fst_v ≡  "fst (splitAt v (verticesFrom f v'))"

    from pre_add u dist_vf_v' have "v ∈ set (fst (splitAt u (verticesFrom f v')))"
      apply (rule_tac before_dist_r1) by (auto  simp: pre_subdivFace'_def)
    with fst_u_def have "fst_u = fst (splitAt v (fst (splitAt u (verticesFrom f v'))))
         @ v # snd (splitAt v (fst (splitAt u (verticesFrom f v'))))"
      by (auto dest: splitAt_ram)
    with pre_add fst_v_def pre_bet' have fst_u':"fst_u
      = fst_v @ v # snd (splitAt v (fst (splitAt u (verticesFrom f v'))))" by (simp add: pre_subdivFace'_def)

    from pre_fdg have "set (v # ws @ [u]) ∩ set (verticesFrom f v') ⊆  {v, u}" apply (simp add: set_eq)
      by (unfold pre_splitFace_def) auto

    with fst_u' have "set (v # ws @ [u]) ∩ set (verticesFrom f v') ⊆ {u} ∪ set fst_u" by auto
    moreover
    from fst_u' have "set fst_v ⊆ set fst_u" by auto
    ultimately
    have "(set (v # ws @ [u]) ∪ set fst_v) ∩ set (verticesFrom f v') ⊆ {u} ∪ set fst_u" by auto
    with fst_u_def fst_v_def
    have "set (fst (splitAt v (verticesFrom f v')) @ v # ws @ [u]) ∩ set (verticesFrom f v')
      ⊆ {u} ∪ set (fst (splitAt u (verticesFrom f v')))" by auto
    moreover
    with False vv' have  "v' # tl (fst (splitAt v (verticesFrom f v')))
      = fst (splitAt v (verticesFrom f v'))" by auto
    ultimately have "set ((v' # tl (fst (splitAt v (verticesFrom f v')))) @ v # ws @ [u]) ∩ set (verticesFrom f v')
      ⊆ {u} ∪ set (fst (splitAt u (verticesFrom f v')))"
     by (simp only:)
    then have help: "set (v' # tl (fst (splitAt v (verticesFrom f v'))) @ v # ws @ [u]) ∩ set (verticesFrom f v')
      ⊆ {u} ∪ set (fst (splitAt u (verticesFrom f v')))" by auto


    from split_u dist_vf_v' pre_add pre_fdg removeNones_split have
      "[v∈ (v' # tl (fst (splitAt v (verticesFrom f v'))) @ v # ws @ [u])
          @ snd (splitAt u (verticesFrom f v')) . v ∈ set (removeNones vol)]
       = removeNones vol ∧ hd (removeNones vol) ∈ set (snd (splitAt u (verticesFrom f v')))"
      apply (rule_tac filter_distinct_at_special) apply assumption+
      apply (simp add: pre_subdivFace'_def) apply (rule help) .
    with False m1 show ?thesis by auto
  qed


  from rule1 have "(hd (removeNones vol)) ∈ set (snd (splitAt u (verticesFrom f v')))" by auto
  with m1 m2  dist_f21_v' have rule3: "before (verticesFrom f21 v') u (hd (removeNones vol))"
  proof -
    assume hd_ram: "(hd (removeNones vol)) ∈ set (snd (splitAt u (verticesFrom f v')))"
    from m1 m2 dist_f21_v' have "distinct (snd (splitAt u (verticesFrom f v')))" apply (cases "v = v'")
      by auto
    moreover
    def z1 ≡ "fst (splitAt (hd (removeNones vol)) (snd (splitAt u (verticesFrom f v'))))"
    def z2 ≡ "snd (splitAt (hd (removeNones vol)) (snd (splitAt u (verticesFrom f v'))))"
    note z1_def z2_def hd_ram
    ultimately have "snd (splitAt u (verticesFrom f v')) = z1 @ (hd (removeNones vol)) # z2"
      by (auto intro: splitAt_ram)
    with m1 m2 show ?thesis apply (cases "v = v'") apply (auto simp: before_def)
      apply (intro exI )
      apply (subgoal_tac "v' # ws @ u # z1 @ hd (removeNones vol) # z2 = (v' # ws) @ u # z1 @ hd (removeNones vol) # z2")
      apply assumption apply simp
      apply (intro exI )
      apply (subgoal_tac "v' # tl (fst (splitAt v (verticesFrom f v'))) @ v # ws @ u # z1 @ hd (removeNones vol) # z2 =
        (v' # tl (fst (splitAt v (verticesFrom f v'))) @ v # ws) @ u # z1 @ hd (removeNones vol) # z2")
      apply assumption by simp
  qed

  from rule1 have ne:"(hd (removeNones vol)) ∈ set (snd (splitAt u (verticesFrom f v')))" by auto
  with m1 m2  have "last (verticesFrom f21 v') = last (snd (splitAt u (verticesFrom f v')))"
    apply (cases "snd (splitAt u (verticesFrom f v'))" rule: rev_exhaust) apply simp_all
    apply (cases "v = v'") by simp_all
  moreover
  from ne have "last (fst (splitAt u (verticesFrom f v')) @ u # snd (splitAt u (verticesFrom f v')))
    = last (snd (splitAt u (verticesFrom f v')))" by auto
  moreover
  note split_u
  ultimately  have rule4: "last (verticesFrom f v') = last (verticesFrom f21 v')" by simp


  have l: "!! a b f v. v ∈ set (vertices f) ==> is_nextElem (vertices f) a b = is_nextElem (verticesFrom f v) a b "
    apply (rule is_nextElem_congs_eq) by (rule verticesFrom_congs)

  def f12 ≡ "fst (split_face f v u ws)"
  then have f12_fdg: "f12 = fst (splitFace g v u f ws)"
    by (simp add: splitFace_def split_def)

   from pre_bet pre_add have bet_eq2[simp]: "between (vertices f) v u = between (verticesFrom f v') v u"
     apply (drule_tac pre_between_symI)
     by (auto intro: verticesFrom_between simp: pre_subdivFace'_def)


  from f12_fdg have f12_split_face: "f12 = fst (split_face f v u ws)"
    by (simp add: splitFace_def split_def)
  then have f12: "f12 = Face (rev ws @ v # between (verticesFrom f v') v u @ [u]) Nonfinal"
    by (simp add: split_face_def)
  then have "vertices f12 = rev ws @ v # between (verticesFrom f v') v u @ [u]" by simp
  with pre_add pre_bet' have vert_f12: "vertices f12
     = rev ws @ v # snd (splitAt v (fst (splitAt u (verticesFrom f v')))) @ [u]"
    apply (subgoal_tac "between (verticesFrom f v') v u = fst (splitAt u (snd (splitAt v (verticesFrom f v'))))")
     apply (simp  add: pre_subdivFace'_def)
    apply (rule between_simp1)
     apply (simp add: pre_subdivFace'_def)
    apply (rule pre_between_symI) .
  with dist_f21_v' have removeNones_vol_not_f12: "!! x. x ∈ set (removeNones vol) ==> x ∉ set (vertices f12)"
    apply (frule_tac notinFst_u) apply (drule inSnd_u) apply simp
    apply (case_tac "v = v'") apply (simp add: m1 m2)
    apply (rule conjI) apply force
    apply (rule conjI) apply (rule ccontr)  apply simp
    apply (subgoal_tac "x ∈ set ws ∩ set (snd (splitAt u (verticesFrom f v')))")
    apply simp apply (elim conjE)
    apply (thin_tac "set ws ∩ set (snd (splitAt u (verticesFrom f v'))) = {}")
    apply simp
    apply force

    apply (simp add: m1 m2)
    apply (rule conjI) apply force
    apply (rule conjI) apply (rule ccontr) apply simp
    apply (subgoal_tac "x ∈ set ws ∩ set (snd (splitAt u (verticesFrom f v')))")
    apply simp apply (elim conjE)
    apply (thin_tac "set ws ∩ set (snd (splitAt u (verticesFrom f v'))) = {}") apply simp
    by force

  from pre_fdg f12_split_face have dist_f12: "distinct (vertices f12)" by (auto intro: split_face_distinct1')

  then have removeNones_vol_edges_not_f12: "!! x y. x ∈ set (removeNones vol) ==> (x,y) ∉ edges f12" (* ? *)
    apply (drule_tac removeNones_vol_not_f12) by auto
  from dist_f12 have removeNones_vol_edges_not_f12': "!! x y. y ∈ set (removeNones vol) ==> (x,y) ∉ edges f12"
    apply (drule_tac removeNones_vol_not_f12) by auto

  from f12_fdg pre_fdg g' fdg have face_set_eq: "\<F> g' ∪ {f} = {f12, f21} ∪ \<F> g"
    apply (rule_tac splitFace_faces_1)
    by (simp_all)

  have rule5'': "!! a b. (a,b) ∈ edges g' ∧ (a,b) ∉ edges g
     ∧ a ∈ set (removeNones vol) ∧ b ∈ set (removeNones vol) ==> (a, b) ∈ edges f21" (* ? *)
    apply (simp add: edges_graph_def) apply safe
    apply (case_tac "x = f") apply simp apply (rule rule5') apply safe
    apply (subgoal_tac "x ∈ \<F> g' ∪ {f}") apply (thin_tac "x ≠ f")
    apply (thin_tac "x ∈ set (faces g')") apply (simp only: add: face_set_eq)
    apply safe apply (drule removeNones_vol_edges_not_f12) by auto
 have rule5''': "!! a b. (a,b) ∈ edges g' ∧ (a,b) ∉ edges g
     ∧ a ∈ set (removeNones vol) ∧ b ∈ set (removeNones vol) ==> (a, b) ∈ edges f21" (* ? *)

    apply (simp add: edges_graph_def) apply safe
    apply (case_tac "x = f") apply simp apply (rule rule5') apply safe
    apply (subgoal_tac "x ∈ \<F> g' ∪ {f}") apply (thin_tac "x ≠ f")
    apply (thin_tac "x ∈ \<F> g'") apply (simp only: add: face_set_eq)
    apply safe apply (drule removeNones_vol_edges_not_f12) by auto


 from pre_fdg fdg f12_fdg  g' have edges_g'1: "ws ≠ [] ==> edges g' = edges g ∪ Edges ws ∪ Edges(rev ws) ∪
   {(u, last ws), (hd ws, v), (v, hd ws), (last ws, u)}"
   apply (rule_tac splitFace_edges_g') apply simp
   apply (subgoal_tac "(f12, f21, g') = splitFace g v u f ws")  apply assumption by auto

 from pre_fdg fdg f12_fdg  g' have edges_g'2: "ws = [] ==> edges g' = edges g ∪
   {(v, u), (u, v)}"
   apply (rule_tac splitFace_edges_g'_vs) apply simp
   apply (subgoal_tac "(f12, f21, g') = splitFace g v u f []")  apply assumption by auto


 from f12_split_face f21_split_face have split: "(f12,f21) = split_face f v u ws" by simp


  from pre_add have "¬ invalidVertexList g f vol"
    by (auto simp: pre_subdivFace'_def dest: invalidVertexList_shorten)
  then have rule5: "¬ invalidVertexList g' f21 vol"

    apply (simp add: invalidVertexList_def)
    apply (intro allI impI)
    apply (case_tac "vol!i")  apply simp+
    apply (case_tac "vol!Suc i") apply simp+
    apply (subgoal_tac "¬ is_duplicateEdge g f a aa")
     apply (thin_tac "∀i<|vol| - Suc 0. ¬ (case vol ! i of None => False
        | Some a => option_case False (is_duplicateEdge g f a) (vol ! (i+1)))")
     apply (simp add: is_duplicateEdge_def)
     apply (subgoal_tac "a ∈ set (removeNones vol) ∧ aa ∈ set (removeNones vol)")
      apply (rule conjI)
       apply (rule impI)
       apply (case_tac "(a, aa) ∈ edges f")
        apply simp
        apply (subgoal_tac "pre_split_face f v u ws")
         apply (frule split_face_edges_or [OF split]) apply simp
         apply (simp add:  removeNones_vol_edges_not_f12)
        apply (rule pre_splitFace_pre_split_face) apply (rule pre_fdg)
       apply (case_tac "(aa, a) ∈ edges f")
        apply simp
        apply (subgoal_tac "pre_split_face f v u ws")
         apply (frule split_face_edges_or [OF split]) apply simp
         apply (simp add:  removeNones_vol_edges_not_f12)
        apply (rule pre_splitFace_pre_split_face) apply (rule pre_fdg)
       apply simp
       apply (case_tac "ws = []") apply (frule edges_g'2)  apply simp
        apply (subgoal_tac "pre_split_face f v u []")
         apply (subgoal_tac "(f12, f21) = split_face f v u ws")
          apply (case_tac "between (vertices f) u v = []")
           apply (frule split_face_edges_f21_bet_vs) apply simp apply simp
           apply simp
          apply (frule split_face_edges_f21_vs) apply simp apply simp apply simp
          apply (case_tac "a = v ∧ aa = u") apply simp apply simp
         apply (rule split)
        apply (subgoal_tac "pre_split_face f v u ws") apply simp
        apply (rule pre_splitFace_pre_split_face) apply (rule pre_fdg)
       apply (frule edges_g'1) apply simp
       apply (subgoal_tac "pre_split_face f v u ws")
        apply (subgoal_tac "(f12, f21) = split_face f v u ws")
         apply (case_tac "between (vertices f) u v = []")
          apply (frule split_face_edges_f21_bet) apply simp apply simp apply simp
          apply simp
          apply (case_tac "a = u ∧ aa = last ws") apply simp apply simp
          apply (case_tac "a = hd ws ∧ aa = v") apply simp apply simp
          apply (case_tac "a = v ∧ aa = hd ws") apply simp apply simp
          apply (case_tac "a = last ws ∧ aa = u") apply simp apply simp
          apply (case_tac "(a, aa) ∈ Edges ws") apply simp
          apply simp
         apply (frule split_face_edges_f21) apply simp apply simp apply simp apply simp
         apply (force)
        apply (rule split)
       apply (rule pre_splitFace_pre_split_face) apply (rule pre_fdg)
      apply (rule impI)
      apply (case_tac "(aa,a) ∈ edges f") apply simp
       apply (subgoal_tac "pre_split_face f v u ws")
        apply (frule split_face_edges_or [OF split]) apply simp
        apply (simp add:  removeNones_vol_edges_not_f12)
       apply (rule pre_splitFace_pre_split_face) apply (rule pre_fdg)
      apply (case_tac "(a,aa) ∈ edges f") apply simp
       apply (subgoal_tac "pre_split_face f v u ws")
        apply (frule split_face_edges_or [OF split]) apply simp
        apply (simp add:  removeNones_vol_edges_not_f12)
       apply (rule pre_splitFace_pre_split_face) apply (rule pre_fdg)
      apply simp
      apply (case_tac "ws = []") apply (frule edges_g'2) apply simp
       apply (subgoal_tac "pre_split_face f v u []")
        apply (subgoal_tac "(f12, f21) = split_face f v u ws")
         apply (case_tac "between (vertices f) u v = []")
          apply (frule split_face_edges_f21_bet_vs) apply simp apply simp
          apply simp
         apply (frule split_face_edges_f21_vs) apply simp apply simp apply simp
         apply force
        apply (rule split)
       apply (subgoal_tac "pre_split_face f v u ws") apply simp
       apply (rule pre_splitFace_pre_split_face) apply (rule pre_fdg)
      apply (frule edges_g'1) apply simp
      apply (subgoal_tac "pre_split_face f v u ws")
       apply (subgoal_tac "(f12, f21) = split_face f v u ws")
        apply (case_tac "between (vertices f) u v = []")
         apply (frule split_face_edges_f21_bet) apply simp apply simp apply simp
         apply (force)
        apply (frule split_face_edges_f21) apply simp apply simp apply simp apply simp
        apply (force)
       apply (rule split)
      apply (rule pre_splitFace_pre_split_face) apply (rule pre_fdg)
     apply (rule conjI)
      apply (subgoal_tac "Some a ∈ set vol") apply (induct vol) apply simp apply force
      apply (subgoal_tac "vol ! i ∈ set vol") apply simp
      apply (rule nth_mem) apply arith
     apply (subgoal_tac "Some aa ∈ set vol") apply (induct vol) apply simp apply force
     apply (subgoal_tac "vol ! (Suc i) ∈ set vol") apply simp apply (rule nth_mem) apply arith
    by auto


  from pre_fdg dist_f21 v' have dists: "distinct (vertices f)"  "distinct (vertices f12)"
     "distinct (vertices f21)"  "v' ∈ \<V> f"
    apply auto defer
    apply (drule splitFace_distinct2) apply (simp add: f12_fdg)
    apply (unfold pre_splitFace_def) by simp
  with pre_fdg have edges_or: "!! a b. (a,b) ∈ edges f ==> (a,b) ∈ edges f12 ∨ (a,b) ∈ edges f21"
    apply (rule_tac split_face_edges_or) apply (simp add: f12_split_face f21_split_face)
   by simp+

 from pre_fdg have dist_f: "distinct (vertices f)" apply (unfold pre_splitFace_def) by simp

(* lemma *)
 from g' have edges_g': "edges g'
    = (UN h:set(replace f [snd (split_face f v u ws)] (faces g)). edges h)
    ∪ edges (fst (split_face f v u ws))"
  by (auto simp add: splitFace_def split_def edges_graph_def)


(* lemma *)
 from pre_fdg edges_g' have edges_g'_or:
   "!! a b. (a,b) ∈ edges g' ==>
    (a,b) ∈ edges g ∨ (a,b) ∈ edges f12 ∨ (a,b) ∈ edges f21"
   apply simp apply (case_tac "(a, b) ∈ edges (fst (split_face f v u ws))")
   apply (simp add:f12_split_face) apply simp
   apply (elim bexE) apply (simp add: f12_split_face) apply (case_tac "x ∈ \<F> g")
   apply (induct g) apply (simp  add: edges_graph_def) apply (rule disjI1)
   apply (rule bexI) apply simp apply simp
   apply (drule replace1) apply simp by (simp add: f21_split_face)

  have rule6: "0 < |vol| ==> ¬ invalidVertexList g f (Some u # vol) ==>
    (∃y. hd vol = Some y) --> ¬ is_duplicateEdge g' f21 u (the (hd vol))"

    apply (rule impI)
    apply (erule exE) apply simp apply (case_tac vol) apply simp+
    apply (simp add: invalidVertexList_def) apply (erule allE) apply (erule impE) apply force
    apply (simp)
    apply (subgoal_tac "y ∉ \<V> f12") defer apply (rule removeNones_vol_not_f12) apply simp
    apply (simp add: is_duplicateEdge_def)
    apply (subgoal_tac "y ∈ set (removeNones vol)")
     apply (rule conjI)
      apply (rule impI)
      apply (case_tac "(u, y) ∈ edges f") apply simp
       apply (subgoal_tac "pre_split_face f v u ws")
        apply (frule split_face_edges_or [OF split]) apply simp
        apply (simp add:  removeNones_vol_edges_not_f12')
       apply (rule pre_splitFace_pre_split_face) apply simp  apply (rule pre_fdg)
      apply (case_tac "(y, u) ∈ edges f") apply simp
       apply (subgoal_tac "pre_split_face f v u ws")
        apply (frule split_face_edges_or [OF split]) apply simp
        apply (simp add:  removeNones_vol_edges_not_f12)
       apply (rule pre_splitFace_pre_split_face) apply simp  apply (rule pre_fdg)
      apply simp
      apply (case_tac "ws = []") apply (frule edges_g'2)  apply simp
       apply (subgoal_tac "pre_split_face f v u []")
        apply (subgoal_tac "(f12, f21) = split_face f v u ws")
         apply (case_tac "between (vertices f) u v = []")
          apply (frule split_face_edges_f21_bet_vs) apply simp apply simp apply simp
         apply (frule split_face_edges_f21_vs) apply simp apply simp apply simp
         apply force
        apply (rule split)
       apply (subgoal_tac "pre_split_face f v u ws") apply simp
       apply (rule pre_splitFace_pre_split_face) apply (rule pre_fdg)
      apply (frule edges_g'1) apply simp
      apply (subgoal_tac "pre_split_face f v u ws")
       apply (subgoal_tac "(f12, f21) = split_face f v u ws")
        apply (case_tac "between (vertices f) u v = []")
         apply (frule split_face_edges_f21_bet) apply simp apply simp apply simp
         apply (force)
        apply (frule split_face_edges_f21) apply simp apply simp apply simp apply simp
        apply (force)
       apply (rule split)
      apply (rule pre_splitFace_pre_split_face) apply (rule pre_fdg)
     apply (rule impI)
     apply (case_tac "(u, y) ∈ edges f") apply simp
     apply (subgoal_tac "pre_split_face f v u ws")
      apply (frule split_face_edges_or [OF split]) apply simp apply (simp add:  removeNones_vol_edges_not_f12')
      apply (rule pre_splitFace_pre_split_face) apply simp  apply (rule pre_fdg)
     apply (case_tac "(y, u) ∈ edges f") apply simp
      apply (subgoal_tac "pre_split_face f v u ws")
       apply (frule split_face_edges_or [OF split]) apply simp apply (simp add:  removeNones_vol_edges_not_f12)
      apply (rule pre_splitFace_pre_split_face) apply simp  apply (rule pre_fdg)
     apply simp
     apply (case_tac "ws = []") apply (frule edges_g'2)  apply simp
      apply (subgoal_tac "pre_split_face f v u []")
       apply (subgoal_tac "(f12, f21) = split_face f v u ws")
        apply (case_tac "between (vertices f) u v = []")
         apply (frule split_face_edges_f21_bet_vs) apply simp apply simp
         apply simp
        apply (frule split_face_edges_f21_vs) apply simp apply simp apply simp
        apply force
       apply (rule split)
      apply (subgoal_tac "pre_split_face f v u ws") apply simp
      apply (rule pre_splitFace_pre_split_face) apply (rule pre_fdg)
     apply (frule edges_g'1) apply simp
     apply (subgoal_tac "pre_split_face f v u ws")
      apply (subgoal_tac "(f12, f21) = split_face f v u ws")
       apply (case_tac "between (vertices f) u v = []")
        apply (frule split_face_edges_f21_bet) apply simp apply simp apply simp
        apply (force)
       apply (frule split_face_edges_f21) apply simp apply simp apply simp apply simp
       apply (force)
      apply (rule split)
     apply (rule pre_splitFace_pre_split_face) apply (rule pre_fdg)
    by simp
  have u21: "u ∈ \<V> f21" by(simp add:f21)
  from fdg have "¬ final f21"
    by(simp add:splitFace_def split_face_def split_def)
  with pre_add rule1 rule2 rule3 rule4 rule5 rule6 dist_f21 False dist u21
  show ?thesis by (simp_all add: pre_subdivFace'_def l)
qed


lemma before_filter: "!!  ys. filter P xs = ys ==> distinct xs ==> before ys  u v ==> before xs u v"
  apply (subgoal_tac "P u")
  apply (subgoal_tac "P v")
  apply (subgoal_tac "pre_between xs u v")
  apply (rule ccontr) apply (simp add: before_xor)
  apply (subgoal_tac "before ys v u")
  apply (subgoal_tac "¬ before ys v u")
  apply simp
  apply (rule before_dist_not1) apply force apply simp
  apply (simp add: before_def) apply (elim exE) apply simp
  apply (subgoal_tac "a @ u # b @ v # c = filter P aa @ v # filter P ba @ u # filter P ca")
  apply (intro exI) apply assumption
  apply simp
  apply (subgoal_tac "u ∈ set ys ∧ v ∈ set ys ∧ u ≠ v") apply (simp add: pre_between_def) apply force
  apply (subgoal_tac "distinct ys")
  apply (simp add: before_def) apply (elim exE) apply simp
  apply force
  apply (subgoal_tac "v ∈ set (filter P xs)") apply force
  apply (simp add: before_def) apply (elim exE) apply simp
  apply (subgoal_tac "u ∈ set (filter P xs)") apply force
  apply (simp add: before_def) apply (elim exE) by simp


lemma pre_subdivFace'_Some2: "pre_subdivFace' g f v' v 0 ((Some u) # vol) ==> pre_subdivFace' g f v' u 0 vol"
apply (cases "vol = []")
 apply (simp add: pre_subdivFace'_def)
  apply (cases "u = v'") apply simp
 apply(rule verticesFrom_in')
  apply(rule last_in_set)
  apply(simp add:verticesFrom_Def)
 apply clarsimp
apply (simp add: pre_subdivFace'_def)
apply (elim conjE)
apply (thin_tac "v' = v ∧ u ≠ last (verticesFrom f v') ∨ v' ≠ v")
apply auto
    apply(rule verticesFrom_in'[where v = v'])
     apply(clarsimp simp:before_def)
    apply simp
   apply (rule ovl_shorten) apply simp
   apply (subgoal_tac "[v∈verticesFrom f v' . v ∈ set (removeNones ((Some u) # vol))] = removeNones ((Some u) # vol)")
    apply assumption
   apply simp
  apply (rule before_filter)
    apply assumption
   apply simp
  apply (simp add: before_def)
  apply (intro exI)
  apply (subgoal_tac "u # removeNones vol = [] @ u # [] @ hd (removeNones vol) # tl (removeNones vol)") apply assumption
  apply simp
  apply (subgoal_tac "removeNones vol ≠ []") apply simp
  apply (cases vol rule: rev_exhaust) apply simp_all
 apply (simp add: invalidVertexList_shorten)
apply (simp add: is_duplicateEdge_def)
apply (case_tac "vol") apply simp
apply simp
apply (simp add: invalidVertexList_def)
apply (elim allE)
apply (rotate_tac -1)
apply (erule impE)
 apply (subgoal_tac "0 < Suc |list|")
  apply assumption
 apply simp
apply simp
by (simp add: is_duplicateEdge_def)

lemma pre_subdivFace'_preFaceDiv: "pre_subdivFace' g f v' v n ((Some u) # vol)
  ==> f ∈ \<F> g ==> (f • v = u --> n ≠ 0) ==> \<V> f ⊆ \<V> g
  ==> pre_splitFace g v u f [countVertices g ..< countVertices g + n]"
proof -
  assume pre_add: "pre_subdivFace' g f v' v n ((Some u) # vol)" and f: "f ∈ \<F> g"
  and nextVert: "(f • v = u --> n ≠ 0)" and subset: "\<V> f ⊆ \<V> g"
  have "distinct [countVertices g ..< countVertices g + n]" by (induct n) auto
  moreover
  have "\<V> g ∩ set [countVertices g ..< countVertices g + n] = {}"
    apply (cases g) by auto
  with subset have "\<V> f ∩ set [countVertices g ..< countVertices g + n] = {}" by auto
  moreover
  from pre_add have "\<V> f = set (verticesFrom f v')" apply (intro congs_pres_nodes verticesFrom_congs)
    by (simp add: pre_subdivFace'_def)
  with pre_add have help: "v ∈ \<V> f ∧ u ∈ \<V> f ∧ v ≠ u"
    apply (simp add: pre_subdivFace'_def before_def)
    apply (elim conjE exE)
    apply (subgoal_tac "distinct (verticesFrom f v')") apply force
    apply (rule verticesFrom_distinct) by simp_all
  moreover
  from help pre_add nextVert have help1: "is_nextElem (vertices f) v u ==> 0 < n" apply auto
    apply (simp add: nextVertex_def)
    by (simp add: nextElem_is_nextElem pre_subdivFace'_def)
  moreover
 have help2: "before (verticesFrom f v') v u ==> distinct (verticesFrom f v') ==> v ≠ v' ==> ¬ is_nextElem (verticesFrom f v') u v"
   apply (simp add: before_def is_nextElem_def verticesFrom_hd is_sublist_def) apply safe
   apply (frule dist_at)
   apply simp
   apply (thin_tac "verticesFrom f v' = a @ v # b @ u # c")
   apply (subgoal_tac "verticesFrom f v' = (as @ [u]) @ v # bs") apply assumption
   apply simp apply (subgoal_tac "distinct (a @ v # b @ u # c)") apply force by simp
  note pre_add f
  moreover
  have "!! m. {k. k < m} ∩ {k. m ≤ k ∧ k < (m + n)} = {}" by auto
  moreover

  from pre_add f help2 help1 help have "[countVertices g..<countVertices g + n] = [] ==> (v, u) ∉ edges f ∧ (u, v) ∉ edges f"
    apply (cases "0 < n") apply (induct g) apply simp+
    apply (simp add: pre_subdivFace'_def)
    apply (rule conjI) apply force
    apply (simp split: split_if_asm)
     apply (rule ccontr)  apply simp
     apply (subgoal_tac "v = v'") apply simp  apply (elim conjE) apply (simp only:)
     apply (rule verticesFrom_is_nextElem_last) apply force apply force
     apply (simp add: verticesFrom_is_nextElem [symmetric])
    apply (cases "v = v'") apply simp
     apply (subgoal_tac "v' ∈ \<V> f")
      apply (thin_tac "u ∈ \<V> f")

      apply (simp add: verticesFrom_is_nextElem)
      apply (rule ccontr) apply simp
      apply (subgoal_tac "v' ∈ \<V> f")
       apply (drule verticesFrom_is_nextElem_hd) apply simp+

    apply (elim conjE) apply (drule help2)
      apply simp apply simp
    apply (subgoal_tac "is_nextElem (vertices f) u v = is_nextElem (verticesFrom f v') u v")
     apply simp
    apply (rule verticesFrom_is_nextElem) by simp
  ultimately

  show ?thesis
    apply (simp add: pre_subdivFace'_def)
    apply (unfold pre_splitFace_def)
    apply simp
    apply (cases "0 < n") apply (induct g) apply simp+

    apply (rule conjI) apply (induct g) apply simp
    apply (rule ccontr) apply (elim conjE)
    by (simp add: invalidVertexList_def is_duplicateEdge_def)
qed


lemma pre_subdivFace'_Some1:
  "pre_subdivFace' g f v' v n ((Some u) # vol)
  ==> f ∈ \<F> g ==> (f • v = u --> n ≠ 0) ==> \<V> f ⊆ \<V> g
  ==> f21 = fst (snd (splitFace g v u f [countVertices g ..< countVertices g + n]))
  ==> g' =  snd (snd (splitFace g v u f [countVertices g ..< countVertices g + n]))
  ==> pre_subdivFace' g' f21 v' u 0 vol"
  apply (subgoal_tac "pre_splitFace g v u f [countVertices g ..< countVertices g + n]")
   apply (rule pre_subdivFace'_Some1') apply assumption+
  apply simp
  apply (rule pre_subdivFace'_preFaceDiv)
  by auto

end

Finality

lemma vertices_makeFaceFinal:

  vertices (makeFaceFinal f g) = vertices g

lemma edges_makeFaceFinal:

  \<E> (makeFaceFinal f g) = \<E> g

lemma nonFins_mkFaceFin:

  nonFinals (makeFaceFinal f g) = remove1 f (nonFinals g)

lemma in_set_repl_setFin:

  [| f ∈ set fs; final f |] ==> f ∈ set (replace f' [setFinal f'] fs)

lemma in_set_repl:

  [| f ∈ set fs; ff' |] ==> f ∈ set (replace f' fs' fs)

lemma makeFaceFinals_preserve_finals:

  f ∈ set (finals g) ==> f ∈ set (finals (makeFaceFinal f' g))

lemma len_faces_makeFaceFinal:

  |faces (makeFaceFinal f g)| = |faces g|

lemma len_finals_makeFaceFinal:

  [| f ∈ \<F> g; ¬ final f |] ==> |finals (makeFaceFinal f g)| = |finals g| + 1

lemma len_nonFinals_makeFaceFinal:

  [| ¬ final f; f ∈ \<F> g |]
  ==> |nonFinals (makeFaceFinal f g)| = |nonFinals g| - 1

lemma set_finals_makeFaceFinal:

  [| distinct (faces g); f ∈ \<F> g |]
  ==> set (finals (makeFaceFinal f g)) = insert (setFinal f) (set (finals g))

lemma splitFace_preserve_final:

  [| f ∈ set (finals g); ¬ final f' |]
  ==> f ∈ set (finals (snd (snd (splitFace g i j f' ns))))

lemma splitFace_nonFinal_face:

  ¬ final (fst (snd (splitFace g i j f' ns)))

lemma subdivFace'_preserve_finals:

  [| f ∈ set (finals g); ¬ final f' |]
  ==> f ∈ set (finals (subdivFace' g f' i n is))

lemma subdivFace_pres_finals:

  [| f ∈ set (finals g); ¬ final f' |] ==> f ∈ set (finals (subdivFace g f' is))

@{text "is_prefix"}

lemma is_prefix_add:

  is_prefix ls vs ==> is_prefix (as @ ls) (as @ vs)

lemma is_prefix_hd:

  is_prefix [l] vs = (l = hd vsvs ≠ [])

lemma is_prefix_f:

  is_prefix (a # as) (a # vs) = is_prefix as vs

lemma splitAt_is_prefix:

  ram ∈ set vs ==> is_prefix (fst (splitAt ram vs) @ [ram]) vs

@{text "is_postfix"}

lemma is_postfix_add:

  is_postfix ls vs ==> is_postfix (ls @ bs) (vs @ bs)

lemma is_pre_post_eq:

  [| distinct vs; ls ≠ []; is_prefix ls vs; is_postfix ls vs |] ==> ls = vs

lemma splitAt_is_postfix:

  ram ∈ set vs ==> is_postfix (ram # snd (splitAt ram vs)) vs

@{text"is_sublist"}

lemma is_prefix_sublist:

  is_prefix ls vs ==> is_sublist ls vs

lemma is_postfix_sublist:

  is_postfix ls vs ==> is_sublist ls vs

lemma is_sublist_trans:

  [| is_sublist as bs; is_sublist bs cs |] ==> is_sublist as cs

lemma is_sublist_add:

  is_sublist as bs ==> is_sublist as (xs @ bs @ ys)

lemma is_sublist_rec:

  is_sublist xs ys =
  (if |ys| < |xs| then False
   else if xs = take |xs| ys then True else is_sublist xs (tl ys))

lemma not_sublist_len:

  |ys| < |xs| ==> ¬ is_sublist xs ys

lemma is_sublist_simp:

  av ==> is_sublist (a # as) (v # vs) = is_sublist (a # as) vs

lemma is_sublist_id:

  is_sublist vs vs

lemma is_sublist_in:

  is_sublist (a # as) vs ==> a ∈ set vs

lemma is_sublist_in1:

  is_sublist [x, y] vs ==> y ∈ set vs

lemma is_sublist_notlast:

  [| distinct vs; x = last vs |] ==> ¬ is_sublist [x, y] vs

lemma is_sublist_nth1:

  is_sublist [x, y] ls
  ==> ∃i j. i < |ls| ∧ j < |ls| ∧ ls ! i = xls ! j = y ∧ Suc i = j

lemma is_sublist_nth2:

i j. i < |ls| ∧ j < |ls| ∧ ls ! i = xls ! j = y ∧ Suc i = j
  ==> is_sublist [x, y] ls

lemma is_sublist_nth_eq:

  (∃i j. i < |ls| ∧ j < |ls| ∧ ls ! i = xls ! j = y ∧ Suc i = j) =
  is_sublist [x, y] ls

lemma is_sublist_tl:

  is_sublist (a # as) vs ==> is_sublist as vs

lemma is_sublist_hd:

  is_sublist (a # as) vs ==> is_sublist [a] vs

lemma is_sublist_hd_eq:

  is_sublist [a] vs = (a ∈ set vs)

lemma is_sublist_distinct_prefix:

  [| is_sublist (v # as) (v # vs); distinct (v # vs) |] ==> is_prefix as vs

lemma is_sublist_distinct:

  [| is_sublist as vs; distinct vs |] ==> distinct as

lemma is_sublist_x_last:

  [| distinct vs; x = last vs |] ==> ¬ is_sublist [x, y] vs

lemma is_sublist_y_hd:

  [| distinct vs; y = hd vs |] ==> ¬ is_sublist [x, y] vs

lemma is_sublist_at1:

  [| distinct (as @ bs); is_sublist [x, y] (as @ bs); x ≠ last as |]
  ==> is_sublist [x, y] as ∨ is_sublist [x, y] bs

lemma is_sublist_at2:

  [| distinct (as @ bs); is_sublist [x, y] (as @ bs); x ≠ last as |]
  ==> is_sublist [x, y] as ≠ is_sublist [x, y] bs

lemma is_sublist_at3:

  [| distinct (as @ bs); is_sublist [x, y] (as @ bs) |]
  ==> (is_sublist [x, y] as ∨ is_sublist [x, y] bs) ∨ x = last as

lemma is_sublist_at4:

  [| distinct (as @ bs); is_sublist [x, y] (as @ bs); as ≠ []; x = last as |]
  ==> y = hd bs

lemma is_sublist_at5:

  [| distinct (as @ bs); is_sublist [x, y] (as @ bs) |]
  ==> is_sublist [x, y] as ∨ is_sublist [x, y] bsx = last asy = hd bs

lemma is_sublist_rev:

  is_sublist [a, b] (rev zs) = is_sublist [b, a] zs

lemma is_sublist_at5':

  [| distinct as; distinct bs; set as ∩ set bs = {};
     is_sublist [x, y] (as @ bs) |]
  ==> is_sublist [x, y] as ∨ is_sublist [x, y] bsx = last asy = hd bs

lemma splitAt_is_sublist1:

  is_sublist (fst (splitAt ram vs)) vs

lemma splitAt_is_sublist1R:

  ram ∈ set vs ==> is_sublist (fst (splitAt ram vs) @ [ram]) vs

lemma splitAt_is_sublist2:

  is_sublist (snd (splitAt ram vs)) vs

lemma splitAt_is_sublist2R:

  ram ∈ set vs ==> is_sublist (ram # snd (splitAt ram vs)) vs

@{text "is_nextElem"}

lemma is_nextElem_a:

  is_nextElem vs a b ==> a ∈ set vs

lemma is_nextElem_b:

  is_nextElem vs a b ==> b ∈ set vs

lemma is_nextElem_sublist:

  [| is_nextElem vs x y; x ≠ last vs |] ==> is_sublist [x, y] vs

lemma is_nextElem_last_hd:

  [| distinct vs; is_nextElem vs x y; x = last vs |] ==> y = hd vs

lemma is_nextElem_last_ne:

  [| distinct vs; is_nextElem vs x y; x = last vs |] ==> vs ≠ []

lemma is_nextElem_sublist2:

  [| is_nextElem vs x y; y ≠ hd vs |] ==> is_sublist [x, y] vs

lemma is_nextElem_sublistI:

  is_sublist [x, y] vs ==> is_nextElem vs x y

lemma is_nextElem_hd_lastI:

  [| vs ≠ []; y = hd vs; x = last vs |] ==> is_nextElem vs x y

lemma is_nextElem_nth1:

  is_nextElem ls x y
  ==> ∃i j. i < |ls| ∧ j < |ls| ∧ ls ! i = xls ! j = y ∧ Suc i mod |ls| = j

lemma is_nextElem_nth2:

i j. i < |ls| ∧ j < |ls| ∧ ls ! i = xls ! j = y ∧ Suc i mod |ls| = j
  ==> is_nextElem ls x y

lemma is_nextElem_rotate1:

  is_nextElem (rotate m ls) x y ==> is_nextElem ls x y

lemma is_nextElem_rotate_eq:

  is_nextElem (rotate m ls) x y = is_nextElem ls x y

lemma is_nextElem_congs_eq:

  lsms ==> is_nextElem ls x y = is_nextElem ms x y

lemma is_nextElem_rotate1:

  [| distinct ls; is_nextElem ls x y |] ==> is_nextElem (rotate1 ls) x y

lemma is_nextElem_congsI:

  [| ls1.0ls2.0; distinct ls1.0; is_nextElem ls1.0 x y |]
  ==> is_nextElem ls2.0 x y

lemma is_nextElem_congseq:

  [| ls1.0ls2.0; distinct ls1.0 |]
  ==> is_nextElem ls1.0 x y = is_nextElem ls2.0 x y

lemma is_nextElem_rev:

  is_nextElem (rev zs) a b = is_nextElem zs b a

lemma is_nextElem_circ:

  [| distinct xs; is_nextElem xs a b; is_nextElem xs b a |] ==> |xs| ≤ 2

lemma cong_if_is_nextElem_eq:

  [| distinct xs; distinct ys; set xs = set ys;
     ∀x y. is_nextElem xs x y = is_nextElem ys x y |]
  ==> xsys

@{text "nextElem, sublist, is_nextElem"}

lemma is_sublist_eq:

  [| distinct vs; cy |] ==> (nextElem vs c x = y) = is_sublist [x, y] vs

lemma is_nextElem1:

  [| distinct vs; x ∈ set vs; nextElem vs (hd vs) x = y |] ==> is_nextElem vs x y

lemma is_nextElem2:

  [| distinct vs; x ∈ set vs; is_nextElem vs x y |] ==> nextElem vs (hd vs) x = y

lemma nextElem_is_nextElem:

  [| distinct xs; x ∈ set xs |]
  ==> is_nextElem xs x y = (nextElem xs (hd xs) x = y)

lemma nextElem_congs_eq:

  [| xsys; distinct xs; x ∈ set xs |]
  ==> nextElem xs (hd xs) x = nextElem ys (hd ys) x

lemma nextElem_iso_eq:

  [| asas'; distinct as; x ∈ set as |]
  ==> nextElem as (hd as) x = nextElem as' (hd as') x

lemma is_sublist_is_nextElem:

  [| distinct vs; is_nextElem vs x y; is_sublist as vs; x ∈ set as; x ≠ last as |]
  ==> is_sublist [x, y] as

@{text before}

lemma before_dist_fst_fst:

  [| before vs ram1.0 ram2.0; distinct vs |]
  ==> fst (splitAt ram2.0 (fst (splitAt ram1.0 vs))) =
      fst (splitAt ram1.0 (fst (splitAt ram2.0 vs)))

lemma before_dist_fst_snd:

  [| before vs ram1.0 ram2.0; distinct vs |]
  ==> fst (splitAt ram2.0 (snd (splitAt ram1.0 vs))) =
      snd (splitAt ram1.0 (fst (splitAt ram2.0 vs)))

lemma before_dist_snd_fst:

  [| before vs ram1.0 ram2.0; distinct vs |]
  ==> snd (splitAt ram2.0 (fst (splitAt ram1.0 vs))) =
      snd (splitAt ram1.0 (snd (splitAt ram2.0 vs)))

lemma before_dist_snd_snd:

  [| before vs ram1.0 ram2.0; distinct vs |]
  ==> snd (splitAt ram2.0 (snd (splitAt ram1.0 vs))) =
      fst (splitAt ram1.0 (snd (splitAt ram2.0 vs)))

lemma before_dist_snd:

  [| before vs ram1.0 ram2.0; distinct vs |]
  ==> fst (splitAt ram1.0 (snd (splitAt ram2.0 vs))) = snd (splitAt ram2.0 vs)

lemma before_dist_fst:

  [| before vs ram1.0 ram2.0; distinct vs |]
  ==> fst (splitAt ram1.0 (fst (splitAt ram2.0 vs))) = fst (splitAt ram1.0 vs)

lemma before_or:

  [| ram1.0 ∈ set vs; ram2.0 ∈ set vs; ram1.0ram2.0 |]
  ==> before vs ram1.0 ram2.0 ∨ before vs ram2.0 ram1.0

lemma before_r1:

  before vs r1.0 r2.0 ==> r1.0 ∈ set vs

lemma before_r2:

  before vs r1.0 r2.0 ==> r2.0 ∈ set vs

lemma before_dist_r1r2:

  [| distinct vs; before vs r1.0 r2.0 |] ==> r1.0r2.0

lemma before_dist_r2:

  [| distinct vs; before vs r1.0 r2.0 |] ==> r2.0 ∈ set (snd (splitAt r1.0 vs))

lemma before_dist_not_r2:

  [| distinct vs; before vs r1.0 r2.0 |] ==> r2.0 ∉ set (fst (splitAt r1.0 vs))

lemma before_dist_r1:

  [| distinct vs; before vs r1.0 r2.0 |] ==> r1.0 ∈ set (fst (splitAt r2.0 vs))

lemma before_dist_not_r1:

  [| distinct vs; before vs r1.0 r2.0 |] ==> r1.0 ∉ set (snd (splitAt r2.0 vs))

lemma before_snd:

  r2.0 ∈ set (snd (splitAt r1.0 vs)) ==> before vs r1.0 r2.0

lemma before_fst:

  [| r2.0 ∈ set vs; r1.0 ∈ set (fst (splitAt r2.0 vs)) |] ==> before vs r1.0 r2.0

lemma before_dist_eq_fst:

  [| distinct vs; r2.0 ∈ set vs |]
  ==> (r1.0 ∈ set (fst (splitAt r2.0 vs))) = before vs r1.0 r2.0

lemma before_dist_eq_snd:

  distinct vs ==> (r2.0 ∈ set (snd (splitAt r1.0 vs))) = before vs r1.0 r2.0

lemma pair_snd:

  (a, b) = p ==> snd p = b

lemma before_dist_eq_snd':

  [| distinct vs; (as, bs) = splitAt ram1 vs |]
  ==> (ram2 ∈ set bs) = before vs ram1 ram2

lemma before_dist_not1:

  [| distinct vs; before vs ram1.0 ram2.0 |] ==> ¬ before vs ram2.0 ram1.0

lemma before_dist_not2:

  [| distinct vs; ram1.0 ∈ set vs; ram2.0 ∈ set vs; ram1.0ram2.0;
     ¬ before vs ram1.0 ram2.0 |]
  ==> before vs ram2.0 ram1.0

lemma before_dist_eq:

  [| distinct vs; ram1.0 ∈ set vs; ram2.0 ∈ set vs; ram1.0ram2.0 |]
  ==> (¬ before vs ram1.0 ram2.0) = before vs ram2.0 ram1.0

lemma before_vs:

  [| distinct vs; before vs ram1.0 ram2.0 |]
  ==> vs =
      fst (splitAt ram1.0 vs) @
      ram1.0 #
      fst (splitAt ram2.0 (snd (splitAt ram1.0 vs))) @
      ram2.0 # snd (splitAt ram2.0 vs)

@{const between}

lemma pre_between_dist:

  pre_between vs ram1.0 ram2.0 ==> distinct vs

lemma pre_between_r1:

  pre_between vs ram1.0 ram2.0 ==> ram1.0 ∈ set vs

lemma pre_between_r2:

  pre_between vs ram1.0 ram2.0 ==> ram2.0 ∈ set vs

lemma pre_between_r12:

  pre_between vs ram1.0 ram2.0 ==> ram1.0ram2.0

lemma pre_between_sym:

  pre_between vs ram1.0 ram2.0 = pre_between vs ram2.0 ram1.0

lemma pre_between_symI:

  pre_between vs ram1.0 ram2.0 ==> pre_between vs ram2.0 ram1.0

lemma pre_between_before:

  pre_between vs ram1.0 ram2.0
  ==> before vs ram1.0 ram2.0 ∨ before vs ram2.0 ram1.0

lemma pre_between_rotate1:

  pre_between vs ram1.0 ram2.0 ==> pre_between (rotate1 vs) ram1.0 ram2.0

lemma pre_between_rotate:

  pre_between vs ram1.0 ram2.0 ==> pre_between (rotate n vs) ram1.0 ram2.0

lemma before_xor:

  pre_between vs ram1.0 ram2.0
  ==> (¬ before vs ram1.0 ram2.0) = before vs ram2.0 ram1.0

lemma between_simp1:

  [| before vs ram1.0 ram2.0; pre_between vs ram1.0 ram2.0 |]
  ==> between vs ram1.0 ram2.0 = fst (splitAt ram2.0 (snd (splitAt ram1.0 vs)))

lemma between_simp2:

  [| before vs ram1.0 ram2.0; pre_between vs ram1.0 ram2.0 |]
  ==> between vs ram2.0 ram1.0 = snd (splitAt ram2.0 vs) @ fst (splitAt ram1.0 vs)

lemma between_not_r1:

  distinct vs ==> ram1.0 ∉ set (between vs ram1.0 ram2.0)

lemma between_not_r2:

  distinct vs ==> ram2.0 ∉ set (between vs ram1.0 ram2.0)

lemma between_distinct:

  distinct vs ==> distinct (between vs ram1.0 ram2.0)

lemma between_distinct_r12:

  [| distinct vs; ram1.0ram2.0 |]
  ==> distinct (ram1.0 # between vs ram1.0 ram2.0 @ [ram2.0])

lemma between_vs:

  [| before vs ram1.0 ram2.0; pre_between vs ram1.0 ram2.0 |]
  ==> vs =
      fst (splitAt ram1.0 vs) @
      ram1.0 # between vs ram1.0 ram2.0 @ ram2.0 # snd (splitAt ram2.0 vs)

lemma between_in:

  [| before vs ram1.0 ram2.0; pre_between vs ram1.0 ram2.0; x ∈ set vs |]
  ==> x = ram1.0x ∈ set (between vs ram1.0 ram2.0) ∨
      x = ram2.0x ∈ set (between vs ram2.0 ram1.0)

lemma

  [| before vs ram1.0 ram2.0; pre_between vs ram1.0 ram2.0; hd vsram1.0;
     (a, b) = splitAt (hd vs) (between vs ram2.0 ram1.0) |]
  ==> vs = [hd vs] @ b @ [ram1.0] @ between vs ram1.0 ram2.0 @ [ram2.0] @ a

lemma between1:

  [| ram1.0 ∈ set vs; ram2.0 ∈ set vs; ram2.0 ∈ set (snd (splitAt ram1.0 vs)) |]
  ==> vs =
      fst (splitAt ram1.0 vs) @
      [ram1.0] @
      between vs ram1.0 ram2.0 @
      [ram2.0] @ snd (splitAt ram2.0 (snd (splitAt ram1.0 vs)))

lemma between2:

  [| ram1.0 ∈ set vs; ram2.0 ∈ set vs; ram1.0ram2.0;
     ram2.0 ∉ set (snd (splitAt ram1.0 vs)) |]
  ==> vs @ vs =
      fst (splitAt ram1.0 vs) @
      [ram1.0] @
      between vs ram1.0 ram2.0 @
      [ram2.0] @
      snd (splitAt ram2.0 (fst (splitAt ram1.0 vs))) @
      [ram1.0] @ snd (splitAt ram1.0 vs)

lemma between_congs:

  [| pre_between vs ram1.0 ram2.0; vsvs' |]
  ==> between vs ram1.0 ram2.0 = between vs' ram1.0 ram2.0

lemma between_inter_empty:

  pre_between vs ram1.0 ram2.0
  ==> set (between vs ram1.0 ram2.0) ∩ set (between vs ram2.0 ram1.0) = {}

@{text "between is_nextElem"}

lemma is_nextElem_or1:

  [| pre_between vs ram1.0 ram2.0; is_nextElem vs x y; before vs ram1.0 ram2.0 |]
  ==> is_sublist [x, y] (ram1.0 # between vs ram1.0 ram2.0 @ [ram2.0]) ∨
      is_sublist [x, y] (ram2.0 # between vs ram2.0 ram1.0 @ [ram1.0])

lemma is_nextElem_or:

  [| pre_between vs ram1.0 ram2.0; is_nextElem vs x y |]
  ==> is_sublist [x, y] (ram1.0 # between vs ram1.0 ram2.0 @ [ram2.0]) ∨
      is_sublist [x, y] (ram2.0 # between vs ram2.0 ram1.0 @ [ram1.0])

lemma between_xor1:

  [| pre_between vs ram1.0 ram2.0; is_nextElem vs x y; before vs ram1.0 ram2.0 |]
  ==> is_sublist [x, y] (ram1.0 # between vs ram1.0 ram2.0 @ [ram2.0]) =
      (¬ is_sublist [x, y] (ram2.0 # between vs ram2.0 ram1.0 @ [ram1.0]))

lemma between_xor:

  [| pre_between vs ram1.0 ram2.0; is_nextElem vs x y |]
  ==> is_sublist [x, y] (ram1.0 # between vs ram1.0 ram2.0 @ [ram2.0]) =
      (¬ is_sublist [x, y] (ram2.0 # between vs ram2.0 ram1.0 @ [ram1.0]))

lemma between_eq1:

  [| pre_between vs ram1.0 ram2.0; before vs ram1.0 ram2.0 |]
  ==> ∃as bs. vs = as @ [ram1.0] @ between vs ram1.0 ram2.0 @ [ram2.0] @ bs

lemma between_eq2:

  [| pre_between vs ram1.0 ram2.0; before vs ram2.0 ram1.0 |]
  ==> ∃as bs cs.
         between vs ram1.0 ram2.0 = cs @ asvs = as @ [ram2.0] @ bs @ [ram1.0] @ cs

lemma is_sublist_same_len:

  |xs| = |ys| ==> is_sublist xs ys = (xs = ys)

lemma is_nextElem_between_empty:

  [| distinct vs; is_nextElem vs a b |] ==> between vs a b = []

lemma is_nextElem_between_empty':

  [| between vs a b = []; distinct vs; a ∈ set vs; b ∈ set vs; ab |]
  ==> is_nextElem vs a b

lemma between_nextElem:

  pre_between vs u v
  ==> between vs u (nextElem vs (hd vs) v) = between vs u v @ [v]

lemma nextVertices_in_face:

  v ∈ \<V> f ==> fnv ∈ \<V> f

@{text "is_nextElem edges"} equivalence

lemma is_nextElem_edges1:

  [| distinct (vertices f); (a, b) ∈ \<E> f |] ==> is_nextElem (vertices f) a b

lemma is_nextElem_edges2:

  [| distinct (vertices f); is_nextElem (vertices f) a b |] ==> (a, b) ∈ \<E> f

lemma is_nextElem_edges_eq:

  distinct (vertices f) ==> ((a, b) ∈ \<E> f) = is_nextElem (vertices f) a b

@{const nextVertex}

lemma nextElem_suc2:

  [| distinct (vertices f); last (vertices f) = v; v ∈ \<V> f |]
  ==> fv = hd (vertices f)

lemma nextVertex_congs_eq:

  [| f1f2; distinct (vertices f1); v ∈ \<V> f1 |] ==> f1v = f2v

@{const split_face}

lemma pre_split_face_p_between:

  pre_split_face oldF ram1.0 ram2.0 newVertexList
  ==> pre_between (vertices oldF) ram1.0 ram2.0

lemma pre_split_face_symI:

  pre_split_face oldF ram1.0 ram2.0 newVertexList
  ==> pre_split_face oldF ram2.0 ram1.0 newVertexList

lemma pre_split_face_rev:

  pre_split_face oldF ram1.0 ram2.0 newVertexList
  ==> pre_split_face oldF ram1.0 ram2.0 (rev newVertexList)

lemma split_face_distinct1:

  [| (f12.0, f21.0) = split_face oldF ram1.0 ram2.0 newVertexList;
     pre_split_face oldF ram1.0 ram2.0 newVertexList |]
  ==> distinct (vertices f12.0)

lemma split_face_distinct1':

  pre_split_face oldF ram1.0 ram2.0 newVertexList
  ==> distinct (vertices (fst (split_face oldF ram1.0 ram2.0 newVertexList)))

lemma split_face_distinct2:

  [| (f12.0, f21.0) = split_face oldF ram1.0 ram2.0 newVertexList;
     pre_split_face oldF ram1.0 ram2.0 newVertexList |]
  ==> distinct (vertices f21.0)

lemma split_face_distinct2':

  pre_split_face oldF ram1.0 ram2.0 newVertexList
  ==> distinct (vertices (snd (split_face oldF ram1.0 ram2.0 newVertexList)))

lemma split_face_edges_or:

  [| (f12.0, f21.0) = split_face oldF ram1.0 ram2.0 newVertexList;
     pre_split_face oldF ram1.0 ram2.0 newVertexList; (a, b) ∈ \<E> oldF |]
  ==> (a, b) ∈ \<E> f12.0 ∨ (a, b) ∈ \<E> f21.0

lemma is_nextElem_hd_last:

  [| distinct vs; is_nextElem vs x y; y = hd vs |] ==> x = last vs

lemma split_face_xor:

  [| (f12.0, f21.0) = split_face oldF ram1.0 ram2.0 newVertexList;
     pre_split_face oldF ram1.0 ram2.0 newVertexList;
     (ram1.0, ram2.0) ∉ \<E> oldF; (ram2.0, ram1.0) ∉ \<E> oldF;
     (a, b) ∈ \<E> oldF |]
  ==> ((a, b) ∈ \<E> f12.0) = ((a, b) ∉ \<E> f21.0)

@{text verticesFrom}

lemmas verticesFrom_Def:

  verticesFrom f == rotate_to (vertices f)
  rotate_to vs v == v # snd (splitAt v vs) @ fst (splitAt v vs)

lemmas verticesFrom_Def:

  verticesFrom f == rotate_to (vertices f)
  rotate_to vs v == v # snd (splitAt v vs) @ fst (splitAt v vs)

lemma len_vFrom:

  v ∈ \<V> f ==> |verticesFrom f v| = |vertices f|

lemma verticesFrom_empty:

  v ∈ \<V> f ==> (verticesFrom f v = []) = (vertices f = [])

lemma verticesFrom_congs:

  v ∈ \<V> f ==> vertices f ≅ verticesFrom f v

lemma verticesFrom_eq_if_vertices_cong:

  [| distinct (vertices f); distinct (vertices f'); vertices f ≅ vertices f';
     x ∈ \<V> f |]
  ==> verticesFrom f x = verticesFrom f' x

lemma verticesFrom_in:

  [| v ∈ \<V> f; a ∈ \<V> f |] ==> a ∈ set (verticesFrom f v)

lemma verticesFrom_in':

  [| a ∈ set (verticesFrom f v); av |] ==> a ∈ \<V> f

lemma set_verticesFrom:

  v ∈ \<V> f ==> set (verticesFrom f v) = \<V> f

lemma verticesFrom_hd:

  hd (verticesFrom f v) = v

lemma verticesFrom_distinct:

  [| distinct (vertices f); v ∈ \<V> f |] ==> distinct (verticesFrom f v)

lemma verticesFrom_nextElem_eq:

  [| distinct (vertices f); v ∈ \<V> f; u ∈ \<V> f |]
  ==> nextElem (verticesFrom f v) (hd (verticesFrom f v)) u =
      nextElem (vertices f) (hd (vertices f)) u

lemma nextElem_vFrom_suc1:

  [| distinct (vertices f); v ∈ \<V> f; i < |vertices f|;
     last (verticesFrom f v) ≠ u; verticesFrom f v ! i = u |]
  ==> fu = verticesFrom f v ! Suc i

lemma nextElem_vFrom_suc2:

  [| distinct (vertices f); last (verticesFrom f v) = u; v ∈ \<V> f; u ∈ \<V> f |]
  ==> fu = hd (verticesFrom f v)

lemma verticesFrom_nth:

  [| distinct (vertices f); d < |vertices f|; v ∈ \<V> f |]
  ==> verticesFrom f v ! d = fdv

lemma verticesFrom_length:

  [| distinct (vertices f); v ∈ \<V> f |] ==> |verticesFrom f v| = |vertices f|

lemma verticesFrom_between:

  [| v' ∈ \<V> f; pre_between (vertices f) u v |]
  ==> between (vertices f) u v = between (verticesFrom f v') u v

lemma verticesFrom_is_nextElem:

  v ∈ \<V> f ==> is_nextElem (vertices f) a b = is_nextElem (verticesFrom f v) a b

lemma verticesFrom_is_nextElem_last:

  [| v' ∈ \<V> f; distinct (vertices f);
     is_nextElem (verticesFrom f v') (last (verticesFrom f v')) v |]
  ==> v = v'

lemma verticesFrom_is_nextElem_hd:

  [| v' ∈ \<V> f; distinct (vertices f); is_nextElem (verticesFrom f v') u v' |]
  ==> u = last (verticesFrom f v')

lemma verticesFrom_pres_nodes1:

  v ∈ \<V> f ==> \<V> f = set (verticesFrom f v)

lemma verticesFrom_pres_nodes:

  [| v ∈ \<V> f; w ∈ \<V> f |] ==> w ∈ set (verticesFrom f v)

lemma before_verticesFrom:

  [| distinct (vertices f); v ∈ \<V> f; w ∈ \<V> f; vw |]
  ==> before (verticesFrom f v) v w

lemma next_not_before:

  [| distinct (vertices f); x ∈ \<V> f; y ∈ \<V> f; xfy |]
  ==> ¬ before (verticesFrom f x) (fy) y

lemma last_vFrom:

  [| distinct (vertices f); x ∈ \<V> f |] ==> last (verticesFrom f x) = f-1x

lemma rotate_before_vFrom:

  [| distinct (vertices f); r ∈ \<V> f; ru; before (verticesFrom f r) u v |]
  ==> before (verticesFrom f v) r u

lemma before_between:

  [| before (verticesFrom f x) y z; distinct (vertices f); x ∈ \<V> f; xy |]
  ==> y ∈ set (between (vertices f) x z)

lemma before_between2:

  [| before (verticesFrom f u) v w; distinct (vertices f); u ∈ \<V> f |]
  ==> u = vu ∈ set (between (vertices f) w v)

@{const splitFace}

lemma pre_splitFace_pre_split_face:

  pre_splitFace g ram1.0 ram2.0 oldF nvs ==> pre_split_face oldF ram1.0 ram2.0 nvs

lemma pre_splitFace_oldF:

  pre_splitFace g ram1.0 ram2.0 oldF nvs ==> oldF ∈ \<F> g

lemma p_splitFace_ne:

  [| pre_splitFace g ram1.0 ram2.0 oldF nvs; (ram1.0, ram2.0) ∈ \<E> oldF |]
  ==> nvs ≠ []

lemma splitFace_preserve_face_not_empty:

  [| f ∉ \<F> g; vertices f' = vs; ram2.0 ∈ set vs;
     f ∈ \<F> (snd (snd (splitFace g ram1.0 ram2.0 f' ns))) |]
  ==> vertices f ≠ []

lemma splitFace_preserve_faces:

  [| f ∈ \<F> g; foldF |]
  ==> f ∈ \<F> (snd (snd (splitFace g ram1.0 ram2.0 oldF nvs)))

lemma splitFace_split_face:

  [| oldF ∈ \<F> g; (f1, f2, newGraph) = splitFace g ram1 ram2 oldF newVs |]
  ==> (f1, f2) = split_face oldF ram1 ram2 newVs

lemma splitFace_add_f21:

  [| (f12.0, f21.0, g') = splitFace g ram1.0 ram2.0 oldF newVertexList;
     oldF ∈ \<F> g |]
  ==> f21.0 ∈ \<F> g'

lemma split_face_empty_ram2_ram1_in_f12:

  [| pre_split_face oldF ram1.0 ram2.0 [];
     (f12.0, f21.0) = split_face oldF ram1.0 ram2.0 [] |]
  ==> (ram2.0, ram1.0) ∈ \<E> f12.0

lemma split_face_empty_ram2_ram1_in_f12':

  pre_split_face oldF ram1.0 ram2.0 []
  ==> (ram2.0, ram1.0) ∈ \<E> (fst (split_face oldF ram1.0 ram2.0 []))

lemma splitFace_empty_ram2_ram1_in_f12:

  [| pre_splitFace g ram1.0 ram2.0 oldF [];
     (f12.0, f21.0, newGraph) = splitFace g ram1.0 ram2.0 oldF [] |]
  ==> (ram2.0, ram1.0) ∈ \<E> f12.0

lemma splitFace_f12_new_vertices:

  [| (f12.0, f21.0, newGraph) = splitFace g ram1.0 ram2.0 oldF newVs;
     v ∈ set newVs |]
  ==> v ∈ \<V> f12.0

lemma splitFace_add_vertices:

  [| newVertexList = [countVertices g..<countVertices g + n];
     (f12.0, f21.0, newGraph) =
     splitFace g ram1.0 ram2.0 oldF (rev newVertexList) |]
  ==> vertices newGraph = vertices g @ newVertexList

lemma splitFace_add_vertices_direct:

  vertices
   (snd (snd (splitFace g ram1.0 ram2.0 oldF
               [countVertices g..<countVertices g + n]))) =
  vertices g @ [countVertices g..<countVertices g + n]

lemma splitFace_delete_oldF:

  [| (f12.0, f21.0, newGraph) = splitFace g ram1.0 ram2.0 oldF newVertexList;
     oldFf12.0; oldFf21.0; distinct (faces g) |]
  ==> oldF ∉ \<F> newGraph

lemma splitFace_faces_1:

  [| (f12.0, f21.0, newGraph) = splitFace g ram1.0 ram2.0 oldF newVertexList;
     oldF ∈ \<F> g |]
  ==> \<F> newGraph ∪ {oldF} = {f12.0, f21.0} ∪ \<F> g

lemma splitFace_distinct1:

  pre_splitFace g ram1.0 ram2.0 oldF newVertexList
  ==> distinct
       (vertices (fst (snd (splitFace g ram1.0 ram2.0 oldF newVertexList))))

lemma splitFace_distinct2:

  pre_splitFace g ram1.0 ram2.0 oldF newVertexList
  ==> distinct (vertices (fst (splitFace g ram1.0 ram2.0 oldF newVertexList)))

lemma splitFace_add_f21':

  f' ∈ \<F> g'
  ==> fst (snd (splitFace g' v a f' nvl))
      ∈ \<F> (snd (snd (splitFace g' v a f' nvl)))

lemma split_face_help:

  Suc 0 < |vertices (fst (split_face f' v a nvl))|

lemma split_face_help':

  Suc 0 < |vertices (snd (split_face f' v a nvl))|

lemma splitFace_split:

  f ∈ \<F> (snd (snd (splitFace g v a f' nvl)))
  ==> f ∈ \<F> gf = fst (splitFace g v a f' nvl) ∨ f = fst (snd (splitFace g v a f' nvl))

lemma pre_FaceDiv_between1:

  pre_splitFace g' ram1.0 ram2.0 f [] ==> between (vertices f) ram1.0 ram2.0 ≠ []

lemma pre_FaceDiv_between2:

  pre_splitFace g' ram1.0 ram2.0 f [] ==> between (vertices f) ram2.0 ram1.0 ≠ []

lemma Edges_Nil:

  Edges [] = {}

lemma Edges_rev:

  Edges (rev zs) = {(b, a). (a, b) ∈ Edges zs}

lemma in_Edges_rev:

  ((a, b) ∈ Edges (rev zs)) = ((b, a) ∈ Edges zs)

lemma notinset_notinEdge1:

  x ∉ set xs ==> (x, y) ∉ Edges xs

lemma notinset_notinEdge2:

  y ∉ set xs ==> (x, y) ∉ Edges xs

lemma in_Edges_in_set:

  (x, y) ∈ Edges vs ==> x ∈ set vsy ∈ set vs

lemma edges_conv_Edges:

  distinct (vertices f)
  ==> \<E> f =
      Edges (vertices f) ∪
      (if vertices f = [] then {} else {(last (vertices f), hd (vertices f))})

lemma edges_conv_Edges_if_cong:

  [| vertices fvs; distinct vs; vs ≠ [] |]
  ==> \<E> f = Edges vs ∪ {(last vs, hd vs)}

lemma Edges_Cons:

  Edges (x # xs) = (if xs = [] then {} else Edges xs ∪ {(x, hd xs)})

lemma Edges_append:

  Edges (xs @ ys) =
  (if xs = [] then Edges ys
   else if ys = [] then Edges xs else Edges xs ∪ Edges ys ∪ {(last xs, hd ys)})

lemma Edges_rev_disj:

  distinct xs ==> Edges (rev xs) ∩ Edges xs = {}

lemma disj_sets_disj_Edges:

  set xs ∩ set ys = {} ==> Edges xs ∩ Edges ys = {}

lemma disj_sets_disj_Edges2:

  set ys ∩ set xs = {} ==> Edges xs ∩ Edges ys = {}

lemma finite_Edges:

  finite (Edges xs)

lemma length_conv_card_Edges:

  distinct xs ==> |xs| = (if |xs| = 0 then 0 else card (Edges xs) + 1)

lemma card_edges:

  distinct (vertices f) ==> card (\<E> f) = |vertices f|

lemma Edges_compl:

  [| distinct vs; x ∈ set vs; y ∈ set vs; xy |]
  ==> Edges (x # between vs x y @ [y]) ∩ Edges (y # between vs y x @ [x]) = {}

lemma Edges_disj:

  [| distinct vs; x ∈ set vs; z ∈ set vs; xy; yz;
     y ∈ set (between vs x z) |]
  ==> Edges (x # between vs x y @ [y]) ∩ Edges (y # between vs y z @ [z]) = {}

lemma edges_conv_Un_Edges:

  [| distinct (vertices f); x ∈ \<V> f; y ∈ \<V> f; xy |]
  ==> \<E> f =
      Edges (x # between (vertices f) x y @ [y]) ∪
      Edges (y # between (vertices f) y x @ [x])

lemma Edges_between_edges:

  [| (a, b) ∈ Edges (u # between (vertices f) u v @ [v]);
     pre_split_face f u v vs |]
  ==> (a, b) ∈ \<E> f

lemma triangle_if_3circular:

  [| distinct [a, b, c]; distinct (vertices f); (a, b) ∈ \<E> f; (b, c) ∈ \<E> f;
     (c, a) ∈ \<E> f |]
  ==> \<E> f = {(a, b), (b, c), (c, a)}

lemma edges_split_face1:

  pre_split_face f u v vs
  ==> \<E> (fst (split_face f u v vs)) =
      Edges (v # rev vs @ [u]) ∪ Edges (u # between (vertices f) u v @ [v])

lemma edges_split_face2:

  pre_split_face f u v vs
  ==> \<E> (snd (split_face f u v vs)) =
      Edges (u # vs @ [v]) ∪ Edges (v # between (vertices f) v u @ [u])

lemma split_face_empty_ram1_ram2_in_f21:

  [| pre_split_face oldF ram1.0 ram2.0 [];
     (f12.0, f21.0) = split_face oldF ram1.0 ram2.0 [] |]
  ==> (ram1.0, ram2.0) ∈ \<E> f21.0

lemma split_face_empty_ram1_ram2_in_f21':

  pre_split_face oldF ram1.0 ram2.0 []
  ==> (ram1.0, ram2.0) ∈ \<E> (snd (split_face oldF ram1.0 ram2.0 []))

lemma splitFace_empty_ram1_ram2_in_f21:

  [| pre_splitFace g ram1.0 ram2.0 oldF [];
     (f12.0, f21.0, newGraph) = splitFace g ram1.0 ram2.0 oldF [] |]
  ==> (ram1.0, ram2.0) ∈ \<E> f21.0

lemma splitFace_f21_new_vertices:

  [| (f12.0, f21.0, newGraph) = splitFace g ram1.0 ram2.0 oldF newVs;
     v ∈ set newVs |]
  ==> v ∈ \<V> f21.0

lemma split_face_f12_f21_neq:

  [| pre_split_face oldF ram1.0 ram2.0 vs;
     (f12.0, f21.0) = split_face oldF ram1.0 ram2.0 vs |]
  ==> f12.0f21.0

lemma split_face_edges_f12:

  [| pre_split_face f ram1.0 ram2.0 vs;
     (f12.0, f21.0) = split_face f ram1.0 ram2.0 vs; vs ≠ [];
     vs1.0 = between (vertices f) ram1.0 ram2.0; vs1.0 ≠ [] |]
  ==> \<E> f12.0 =
      {(hd vs, ram1.0), (ram1.0, hd vs1.0), (last vs1.0, ram2.0),
       (ram2.0, last vs)} ∪
      Edges (rev vs) ∪
      Edges vs1.0

lemma split_face_edges_f12_vs:

  [| pre_split_face f ram1.0 ram2.0 [];
     (f12.0, f21.0) = split_face f ram1.0 ram2.0 [];
     vs1.0 = between (vertices f) ram1.0 ram2.0; vs1.0 ≠ [] |]
  ==> \<E> f12.0 =
      {(ram2.0, ram1.0), (ram1.0, hd vs1.0), (last vs1.0, ram2.0)} ∪ Edges vs1.0

lemma split_face_edges_f12_bet:

  [| pre_split_face f ram1.0 ram2.0 vs;
     (f12.0, f21.0) = split_face f ram1.0 ram2.0 vs; vs ≠ [];
     between (vertices f) ram1.0 ram2.0 = [] |]
  ==> \<E> f12.0 =
      {(hd vs, ram1.0), (ram1.0, ram2.0), (ram2.0, last vs)} ∪ Edges (rev vs)

lemma split_face_edges_f12_bet_vs:

  [| pre_split_face f ram1.0 ram2.0 [];
     (f12.0, f21.0) = split_face f ram1.0 ram2.0 [];
     between (vertices f) ram1.0 ram2.0 = [] |]
  ==> \<E> f12.0 = {(ram2.0, ram1.0), (ram1.0, ram2.0)}

lemma split_face_edges_f12_subset:

  [| pre_split_face f ram1.0 ram2.0 vs;
     (f12.0, f21.0) = split_face f ram1.0 ram2.0 vs; vs ≠ [] |]
  ==> {(hd vs, ram1.0), (ram2.0, last vs)} ∪ Edges (rev vs) ⊆ \<E> f12.0

lemma split_face_edges_f21:

  [| pre_split_face f ram1.0 ram2.0 vs;
     (f12.0, f21.0) = split_face f ram1.0 ram2.0 vs; vs ≠ [];
     vs2.0 = between (vertices f) ram2.0 ram1.0; vs2.0 ≠ [] |]
  ==> \<E> f21.0 =
      {(last vs2.0, ram1.0), (ram1.0, hd vs), (last vs, ram2.0),
       (ram2.0, hd vs2.0)} ∪
      Edges vs ∪
      Edges vs2.0

lemma split_face_edges_f21_vs:

  [| pre_split_face f ram1.0 ram2.0 [];
     (f12.0, f21.0) = split_face f ram1.0 ram2.0 [];
     vs2.0 = between (vertices f) ram2.0 ram1.0; vs2.0 ≠ [] |]
  ==> \<E> f21.0 =
      {(last vs2.0, ram1.0), (ram1.0, ram2.0), (ram2.0, hd vs2.0)} ∪ Edges vs2.0

lemma split_face_edges_f21_bet:

  [| pre_split_face f ram1.0 ram2.0 vs;
     (f12.0, f21.0) = split_face f ram1.0 ram2.0 vs; vs ≠ [];
     between (vertices f) ram2.0 ram1.0 = [] |]
  ==> \<E> f21.0 =
      {(ram1.0, hd vs), (last vs, ram2.0), (ram2.0, ram1.0)} ∪ Edges vs

lemma split_face_edges_f21_bet_vs:

  [| pre_split_face f ram1.0 ram2.0 [];
     (f12.0, f21.0) = split_face f ram1.0 ram2.0 [];
     between (vertices f) ram2.0 ram1.0 = [] |]
  ==> \<E> f21.0 = {(ram1.0, ram2.0), (ram2.0, ram1.0)}

lemma split_face_edges_f21_subset:

  [| pre_split_face f ram1.0 ram2.0 vs;
     (f12.0, f21.0) = split_face f ram1.0 ram2.0 vs; vs ≠ [] |]
  ==> {(last vs, ram2.0), (ram1.0, hd vs)} ∪ Edges vs ⊆ \<E> f21.0

lemma verticesFrom_ram1:

  pre_split_face f ram1.0 ram2.0 vs
  ==> verticesFrom f ram1.0 =
      ram1.0 #
      between (vertices f) ram1.0 ram2.0 @
      ram2.0 # between (vertices f) ram2.0 ram1.0

lemma split_face_edges_f_vs1_vs2:

  [| pre_split_face f ram1.0 ram2.0 vs; between (vertices f) ram1.0 ram2.0 = [];
     between (vertices f) ram2.0 ram1.0 = [] |]
  ==> \<E> f = {(ram2.0, ram1.0), (ram1.0, ram2.0)}

lemma split_face_edges_f_vs1:

  [| pre_split_face f ram1.0 ram2.0 vs; between (vertices f) ram1.0 ram2.0 = [];
     vs2.0 = between (vertices f) ram2.0 ram1.0; vs2.0 ≠ [] |]
  ==> \<E> f =
      {(last vs2.0, ram1.0), (ram1.0, ram2.0), (ram2.0, hd vs2.0)} ∪ Edges vs2.0

lemma split_face_edges_f_vs2:

  [| pre_split_face f ram1.0 ram2.0 vs;
     vs1.0 = between (vertices f) ram1.0 ram2.0; vs1.0 ≠ [];
     between (vertices f) ram2.0 ram1.0 = [] |]
  ==> \<E> f =
      {(ram2.0, ram1.0), (ram1.0, hd vs1.0), (last vs1.0, ram2.0)} ∪ Edges vs1.0

lemma split_face_edges_f:

  [| pre_split_face f ram1.0 ram2.0 vs;
     vs1.0 = between (vertices f) ram1.0 ram2.0; vs1.0 ≠ [];
     vs2.0 = between (vertices f) ram2.0 ram1.0; vs2.0 ≠ [] |]
  ==> \<E> f =
      {(last vs2.0, ram1.0), (ram1.0, hd vs1.0), (last vs1.0, ram2.0),
       (ram2.0, hd vs2.0)} ∪
      Edges vs1.0 ∪
      Edges vs2.0

lemma split_face_edges_f12_f21:

  [| pre_split_face f ram1.0 ram2.0 vs;
     (f12.0, f21.0) = split_face f ram1.0 ram2.0 vs; vs ≠ [] |]
  ==> \<E> f12.0 ∪ \<E> f21.0 =
      \<E> f ∪
      {(hd vs, ram1.0), (ram1.0, hd vs), (last vs, ram2.0), (ram2.0, last vs)} ∪
      Edges vs ∪
      Edges (rev vs)

lemma split_face_edges_f12_f21_vs:

  [| pre_split_face f ram1.0 ram2.0 [];
     (f12.0, f21.0) = split_face f ram1.0 ram2.0 [] |]
  ==> \<E> f12.0 ∪ \<E> f21.0 = \<E> f ∪ {(ram2.0, ram1.0), (ram1.0, ram2.0)}

lemma split_face_edges_f12_f21_sym:

  [| f ∈ \<F> g; pre_split_face f ram1.0 ram2.0 vs;
     (f12.0, f21.0) = split_face f ram1.0 ram2.0 vs |]
  ==> ((a, b) ∈ \<E> f12.0 ∨ (a, b) ∈ \<E> f21.0) =
      ((a, b) ∈ \<E> f ∨
       ((b, a) ∈ \<E> f12.0 ∨ (b, a) ∈ \<E> f21.0) ∧
       ((a, b) ∈ \<E> f12.0 ∨ (a, b) ∈ \<E> f21.0))

lemma splitFace_edges_g'_help:

  [| pre_splitFace g ram1.0 ram2.0 f vs;
     (f12.0, f21.0, g') = splitFace g ram1.0 ram2.0 f vs; vs ≠ [] |]
  ==> \<E> g' =
      \<E> g ∪ \<E> f ∪ Edges vs ∪ Edges (rev vs) ∪
      {(ram2.0, last vs), (hd vs, ram1.0), (ram1.0, hd vs), (last vs, ram2.0)}

lemma pre_splitFace_edges_f_in_g:

  pre_splitFace g ram1.0 ram2.0 f vs ==> \<E> f ⊆ \<E> g

lemma pre_splitFace_edges_f_in_g2:

  [| pre_splitFace g ram1.0 ram2.0 f vs; x ∈ \<E> f |] ==> x ∈ \<E> g

lemma splitFace_edges_g':

  [| pre_splitFace g ram1.0 ram2.0 f vs;
     (f12.0, f21.0, g') = splitFace g ram1.0 ram2.0 f vs; vs ≠ [] |]
  ==> \<E> g' =
      \<E> g ∪ Edges vs ∪ Edges (rev vs) ∪
      {(ram2.0, last vs), (hd vs, ram1.0), (ram1.0, hd vs), (last vs, ram2.0)}

lemma splitFace_edges_g'_vs:

  [| pre_splitFace g ram1.0 ram2.0 f [];
     (f12.0, f21.0, g') = splitFace g ram1.0 ram2.0 f [] |]
  ==> \<E> g' = \<E> g ∪ {(ram1.0, ram2.0), (ram2.0, ram1.0)}

lemma splitFace_edges_incr:

  [| pre_splitFace g ram1.0 ram2.0 f vs;
     (f1, f2, g') = splitFace g ram1.0 ram2.0 f vs |]
  ==> \<E> g ⊆ \<E> g'

lemma snd_snd_splitFace_edges_incr:

  pre_splitFace g v1 v2 f vs
  ==> \<E> g ⊆ \<E> (snd (snd (splitFace g v1 v2 f vs)))

@{text removeNones}

lemma removeNones_inI:

  Some a ∈ set ls ==> a ∈ set (removeNones ls)

lemma removeNones_hd:

  removeNones (Some a # ls) = a # removeNones ls

lemma removeNones_last:

  removeNones (ls @ [Some a]) = removeNones ls @ [a]

lemma removeNones_in:

  removeNones (as @ Some a # bs) = removeNones as @ a # removeNones bs

lemma removeNones_none_hd:

  removeNones (None # ls) = removeNones ls

lemma removeNones_none_last:

  removeNones (ls @ [None]) = removeNones ls

lemma removeNones_none_in:

  removeNones (as @ None # bs) = removeNones (as @ bs)

lemma removeNones_inI:

  Some a ∈ set ls ==> a ∈ set (removeNones ls)

lemma removeNones_empty:

  removeNones [] = []

@{text natToVertexList}

@{const indexToVertexList}

lemma nextVertex_inj:

  [| distinct (vertices f); v ∈ \<V> f; i < |vertices f|; a < |vertices f|;
     fav = fiv |]
  ==> i = a

lemma a:

  [| distinct (vertices f); v ∈ \<V> f; ∀i∈set is. i < |vertices f|;
     a < |vertices f| |]
  ==> hideDupsRec ((f • ^ a) v) [(f • ^ k) v. k : is] =
      natToVertexListRec a v f is

lemma indexToVertexList_natToVertexList_eq:

  [| distinct (vertices f); v ∈ \<V> f; ∀i∈set is. i < |vertices f|; is ≠ [];
     hd is = 0 |]
  ==> indexToVertexList f v is = natToVertexList v f is

lemma nvlr_length:

  |natToVertexListRec old v f ls| = |ls|

lemma nvl_length:

  hd e = 0 ==> |natToVertexList v f e| = |e|

lemma nvl_nvlRec:

  [| 1 < i; incrIndexList e i |vertices f| |]
  ==> natToVertexList v f e = Some v # natToVertexListRec 0 v f (tl e)

lemma natToVertexListRec_length:

  |natToVertexListRec e v f es| = |es|

lemma natToVertexList_length:

  incrIndexList es |es| |vertices f| ==> |natToVertexList v f es| = |es|

lemma natToVertexList_nth_Suc:

  [| incrIndexList es |es| |vertices f|; Suc n < |es| |]
  ==> natToVertexList v f es ! Suc n =
      (if es ! n = es ! Suc n then None else Some fes ! Suc nv)

lemma natToVertexList_nth_0:

  [| incrIndexList es |es| |vertices f|; 0 < |es| |]
  ==> natToVertexList v f es ! 0 = Some fes ! 0v

lemma natToVertexList_hd:

  incrIndexList es |es| |vertices f| ==> hd (natToVertexList v f es) = Some v

lemma nth_last:

  Suc i = |xs| ==> xs ! i = last xs

lemma natToVertexList_last:

  [| distinct (vertices f); v ∈ \<V> f; incrIndexList es |es| |vertices f| |]
  ==> last (natToVertexList v f es) = Some (last (verticesFrom f v))

lemma indexToVertexList_last:

  [| distinct (vertices f); v ∈ \<V> f; incrIndexList es |es| |vertices f| |]
  ==> last (indexToVertexList f v es) = Some (last (verticesFrom f v))

lemma sublist_take:

iiset. i < n ==> sublist (take n xs) iset = sublist xs iset

lemma sublist_reduceIndices:

  sublist xs iset = sublist xs {i. i < |xs| ∧ iiset}

lemma natToVertexList_sublist1:

  [| distinct (vertices f); v ∈ \<V> f; vs = verticesFrom f v;
     incrIndexList es |es| |vs|; n ≤ |es| |]
  ==> sublist (take (Suc (es ! (n - 1))) vs) (set (take n es)) =
      removeNones (take n (natToVertexList v f es))

lemma natToVertexList_sublist:

  [| distinct (vertices f); v ∈ \<V> f; incrIndexList es |es| |vertices f| |]
  ==> sublist (verticesFrom f v) (set es) = removeNones (natToVertexList v f es)

lemma filter_Cons2:

  x ∉ set ys ==> [yys . y = xP y] = filter P ys

lemma natToVertexList_removeNones:

  [| distinct (vertices f); v ∈ \<V> f; incrIndexList es |es| |vertices f| |]
  ==> [x∈verticesFrom f v . x ∈ set (removeNones (natToVertexList v f es))] =
      removeNones (natToVertexList v f es)

lemma indexToVertexList_removeNones:

  [| distinct (vertices f); v ∈ \<V> f; incrIndexList es |es| |vertices f| |]
  ==> [x∈verticesFrom f v . x ∈ set (removeNones (indexToVertexList f v es))] =
      removeNones (indexToVertexList f v es)

@{text"pre_subdivFace(')"}

lemma pre_subdivFace_face_in_f:

  [| pre_subdivFace_face f v ls; Some a ∈ set ls |] ==> a ∈ set (verticesFrom f v)

lemma pre_subdivFace_in_f:

  [| pre_subdivFace g f v ls; Some a ∈ set ls |] ==> a ∈ set (verticesFrom f v)

lemma pre_subdivFace_face_in_f':

  [| pre_subdivFace_face f v ls; Some a ∈ set ls |] ==> a ∈ \<V> f

lemma hilf1:

  a ∈ set b ==> (v = av ∈ set b) = (v ∈ set b)

lemma filter_congs_shorten1':

  [| distinct (vertices f); [v∈vertices f . v = av ∈ set vs] ≅ a # vs |]
  ==> [v∈vertices f . v ∈ set vs] ≅ vs

lemma filter_congs_shorten1:

  [| distinct (verticesFrom f v);
     [v∈verticesFrom f v . v = av ∈ set vs] = a # vs |]
  ==> [v∈verticesFrom f v . v ∈ set vs] = vs

lemma ovl_shorten':

  [| distinct (vertices f);
     [v∈vertices f . v ∈ set (removeNones (va # vol))] ≅ removeNones (va # vol) |]
  ==> [v∈vertices f . v ∈ set (removeNones vol)] ≅ removeNones vol

lemma ovl_shorten:

  [| distinct (verticesFrom f v);
     [v∈verticesFrom f v . v ∈ set (removeNones (va # vol))] =
     removeNones (va # vol) |]
  ==> [v∈verticesFrom f v . v ∈ set (removeNones vol)] = removeNones vol

lemma pre_subdivFace_face_distinct:

  pre_subdivFace_face f v vol ==> distinct (removeNones vol)

lemma pre_subdivFace_face_not_empty:

  pre_subdivFace_face f v (vo # vol) ==> vol ≠ []

lemma invalidVertexList_shorten:

  invalidVertexList g f vol ==> invalidVertexList g f (v # vol)

lemma edges_in_faces_in_graph:

  [| x ∈ \<E> f; f ∈ \<F> g |] ==> x ∈ \<E> g

lemma pre_subdivFace_pre_subdivFace':

  [| v ∈ \<V> f; pre_subdivFace g f v (vo # vol) |]
  ==> pre_subdivFace' g f v v 0 vol

lemma pre_subdivFace'_distinct:

  pre_subdivFace' g f v' v n vol ==> distinct (removeNones vol)

lemma natToVertexList_pre_subdivFace_face:

  [| ¬ final f; distinct (vertices f); v ∈ \<V> f; 2 < |es|;
     incrIndexList es |es| |vertices f| |]
  ==> pre_subdivFace_face f v (natToVertexList v f es)

lemma indexToVertexList_pre_subdivFace_face:

  [| ¬ final f; distinct (vertices f); v ∈ \<V> f; 2 < |es|;
     incrIndexList es |es| |vertices f| |]
  ==> pre_subdivFace_face f v (indexToVertexList f v es)

lemma subdivFace_subdivFace'_eq:

  pre_subdivFace g f v vol ==> subdivFace g f vol = subdivFace' g f v 0 (tl vol)

lemma pre_subdivFace'_None:

  pre_subdivFace' g f v' v n (None # vol) ==> pre_subdivFace' g f v' v (Suc n) vol

lemma verticesFrom_split:

  v # tl (verticesFrom f v) = verticesFrom f v

lemma verticesFrom_v:

  [| distinct (vertices f); vertices f = a @ v # b |]
  ==> verticesFrom f v = v # b @ a

lemma splitAt_fst:

  [| distinct xs; xs = a @ v # b |] ==> fst (splitAt v xs) = a

lemma splitAt_snd:

  [| distinct xs; xs = a @ v # b |] ==> snd (splitAt v xs) = b

lemma verticesFrom_splitAt_v_fst:

  distinct (verticesFrom f v) ==> fst (splitAt v (verticesFrom f v)) = []

lemma verticesFrom_splitAt_v_snd:

  distinct (verticesFrom f v)
  ==> snd (splitAt v (verticesFrom f v)) = tl (verticesFrom f v)

lemma filter_distinct_at:

  [| distinct xs; xs = as @ u # bs; [vxs . v = uP v] = u # us |]
  ==> filter P bs = us ∧ filter P as = []

lemma filter_distinct_at2:

  [| distinct xs; xs = as @ u # bs; [vxs . v = uP v] = u # us;
     filter P zs = [] |]
  ==> filter P (zs @ bs) = us

lemma filter_distinct_at3:

  [| distinct xs; xs = as @ u # bs; [vxs . v = uP v] = u # us;
     ∀z∈set zs. z ∈ set as ∨ ¬ P z |]
  ==> filter P (zs @ bs) = us

lemma filter_distinct_at4:

  [| distinct xs; xs = as @ u # bs; [vxs . v = uv ∈ set us] = u # us;
     set zs ∩ set us ⊆ {u} ∪ set as |]
  ==> [vzs @ bs . v ∈ set us] = us

lemma filter_distinct_at5:

  [| distinct xs; xs = as @ u # bs; [vxs . v = uv ∈ set us] = u # us;
     set zs ∩ set xs ⊆ {u} ∪ set as |]
  ==> [vzs @ bs . v ∈ set us] = us

lemma filter_distinct_at6:

  [| distinct xs; xs = as @ u # bs; [vxs . v = uv ∈ set us] = u # us;
     set zs ∩ set xs ⊆ {u} ∪ set as |]
  ==> [vzs @ bs . v ∈ set us] = us ∧ [vbs . v ∈ set us] = us

lemma filter_distinct_at_special:

  [| distinct xs; xs = as @ u # bs; [vxs . v = uv ∈ set us] = u # us;
     set zs ∩ set xs ⊆ {u} ∪ set as; us = hd_us # tl_us |]
  ==> [vzs @ bs . v ∈ set us] = ushd_us ∈ set bs

lemma pre_subdivFace'_Some1':

  [| pre_subdivFace' g f v' v n (Some u # vol); pre_splitFace g v u f ws;
     f21.0 = fst (snd (splitFace g v u f ws));
     g' = snd (snd (splitFace g v u f ws)) |]
  ==> pre_subdivFace' g' f21.0 v' u 0 vol

lemma before_filter:

  [| filter P xs = ys; distinct xs; before ys u v |] ==> before xs u v

lemma pre_subdivFace'_Some2:

  pre_subdivFace' g f v' v 0 (Some u # vol) ==> pre_subdivFace' g f v' u 0 vol

lemma pre_subdivFace'_preFaceDiv:

  [| pre_subdivFace' g f v' v n (Some u # vol); f ∈ \<F> g; fv = u --> n ≠ 0;
     \<V> f ⊆ \<V> g |]
  ==> pre_splitFace g v u f [countVertices g..<countVertices g + n]

lemma pre_subdivFace'_Some1:

  [| pre_subdivFace' g f v' v n (Some u # vol); f ∈ \<F> g; fv = u --> n ≠ 0;
     \<V> f ⊆ \<V> g;
     f21.0 =
     fst (snd (splitFace g v u f [countVertices g..<countVertices g + n]));
     g' = snd (snd (splitFace g v u f [countVertices g..<countVertices g + n])) |]
  ==> pre_subdivFace' g' f21.0 v' u 0 vol