Theory Transitive_Closure (Isabelle2005: October 2005)

# Theory Transitive_Closure

Up to index of Isabelle/HOL

theory Transitive_Closure
imports Inductive
uses (../Provers/trancl.ML) [Transitive_Closure.ML]
begin

    (*  Title:      HOL/Transitive_Closure.thy
        ID:         $Id: Transitive_Closure.thy,v 1.34 2005/09/22 21:56:16 nipkow Exp $
        Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
        Copyright   1992  University of Cambridge
    *)

    header {* Reflexive and Transitive closure of a relation *}

    theory Transitive_Closure
    imports Inductive
    uses ("../Provers/trancl.ML")
    begin

    text {*
      @{text rtrancl} is reflexive/transitive closure,
      @{text trancl} is transitive closure,
      @{text reflcl} is reflexive closure.

      These postfix operators have \emph{maximum priority}, forcing their
      operands to be atomic.
    *}

    consts
      rtrancl :: "('a × 'a) set => ('a × 'a) set"    ("(_^*)" [1000] 999)

    inductive "r^*"
      intros
        rtrancl_refl [intro!, Pure.intro!, simp]: "(a, a) : r^*"
        rtrancl_into_rtrancl [Pure.intro]: "(a, b) : r^* ==> (b, c) : r ==> (a, c) : r^*"

    consts
      trancl :: "('a × 'a) set => ('a × 'a) set"    ("(_^+)" [1000] 999)

    inductive "r^+"
      intros
        r_into_trancl [intro, Pure.intro]: "(a, b) : r ==> (a, b) : r^+"
        trancl_into_trancl [Pure.intro]: "(a, b) : r^+ ==> (b, c) : r ==> (a,c) : r^+"

    syntax
      "_reflcl" :: "('a × 'a) set => ('a × 'a) set"    ("(_^=)" [1000] 999)
    translations
      "r^=" == "r ∪ Id"

    syntax (xsymbols)
      rtrancl :: "('a × 'a) set => ('a × 'a) set"    ("(_*)" [1000] 999)
      trancl :: "('a × 'a) set => ('a × 'a) set"    ("(_+)" [1000] 999)
      "_reflcl" :: "('a × 'a) set => ('a × 'a) set"    ("(_=)" [1000] 999)

    syntax (HTML output)
      rtrancl :: "('a × 'a) set => ('a × 'a) set"    ("(_*)" [1000] 999)
      trancl :: "('a × 'a) set => ('a × 'a) set"    ("(_+)" [1000] 999)
      "_reflcl" :: "('a × 'a) set => ('a × 'a) set"    ("(_=)" [1000] 999)

    subsection {* Reflexive-transitive closure *}

    lemma r_into_rtrancl [intro]: "!!p. p ∈ r ==> p ∈ r^*"
      -- {* @{text rtrancl} of @{text r} contains @{text r} *}
      apply (simp only: split_tupled_all)
      apply (erule rtrancl_refl [THEN rtrancl_into_rtrancl])
      done

    lemma rtrancl_mono: "r ⊆ s ==> r^* ⊆ s^*"
      -- {* monotonicity of @{text rtrancl} *}
      apply (rule subsetI)
      apply (simp only: split_tupled_all)
      apply (erule rtrancl.induct)
       apply (rule_tac [2] rtrancl_into_rtrancl, blast+)
      done

    theorem rtrancl_induct [consumes 1, induct set: rtrancl]:
      assumes a: "(a, b) : r^*"
        and cases: "P a" "!!y z. [| (a, y) : r^*; (y, z) : r; P y |] ==> P z"
      shows "P b"
    proof -
      from a have "a = a --> P b"
        by (induct "%x y. x = a --> P y" a b) (iprover intro: cases)+
      thus ?thesis by iprover
    qed

    lemmas rtrancl_induct2 =
      rtrancl_induct[of "(ax,ay)" "(bx,by)", split_format (complete),
                     consumes 1, case_names refl step]

    lemma trans_rtrancl: "trans(r^*)"
      -- {* transitivity of transitive closure!! -- by induction *}
    proof (rule transI)
      fix x y z
      assume "(x, y) ∈ r*"
      assume "(y, z) ∈ r*"
      thus "(x, z) ∈ r*" by induct (iprover!)+
    qed

    lemmas rtrancl_trans = trans_rtrancl [THEN transD, standard]

    lemma rtranclE:
      "[| (a::'a,b) : r^*;  (a = b) ==> P;
          !!y.[| (a,y) : r^*; (y,b) : r |] ==> P
       |] ==> P"
      -- {* elimination of @{text rtrancl} -- by induction on a special formula *}
    proof -
      assume major: "(a::'a,b) : r^*"
      case rule_context
      show ?thesis
        apply (subgoal_tac "(a::'a) = b | (EX y. (a,y) : r^* & (y,b) : r)")
         apply (rule_tac [2] major [THEN rtrancl_induct])
          prefer 2 apply (blast!)
          prefer 2 apply (blast!)
        apply (erule asm_rl exE disjE conjE prems)+
        done
    qed

    lemma converse_rtrancl_into_rtrancl:
      "(a, b) ∈ r ==> (b, c) ∈ r* ==> (a, c) ∈ r*"
      by (rule rtrancl_trans) iprover+

    text {*
      \medskip More @{term "r^*"} equations and inclusions.
    *}

    lemma rtrancl_idemp [simp]: "(r^*)^* = r^*"
      apply auto
      apply (erule rtrancl_induct)
       apply (rule rtrancl_refl)
      apply (blast intro: rtrancl_trans)
      done

    lemma rtrancl_idemp_self_comp [simp]: "R^* O R^* = R^*"
      apply (rule set_ext)
      apply (simp only: split_tupled_all)
      apply (blast intro: rtrancl_trans)
      done

    lemma rtrancl_subset_rtrancl: "r ⊆ s^* ==> r^* ⊆ s^*"
    by (drule rtrancl_mono, simp)

    lemma rtrancl_subset: "R ⊆ S ==> S ⊆ R^* ==> S^* = R^*"
      apply (drule rtrancl_mono)
      apply (drule rtrancl_mono, simp)
      done

    lemma rtrancl_Un_rtrancl: "(R^* ∪ S^*)^* = (R ∪ S)^*"
      by (blast intro!: rtrancl_subset intro: r_into_rtrancl rtrancl_mono [THEN subsetD])

    lemma rtrancl_reflcl [simp]: "(R^=)^* = R^*"
      by (blast intro!: rtrancl_subset intro: r_into_rtrancl)

    lemma rtrancl_r_diff_Id: "(r - Id)^* = r^*"
      apply (rule sym)
      apply (rule rtrancl_subset, blast, clarify)
      apply (rename_tac a b)
      apply (case_tac "a = b", blast)
      apply (blast intro!: r_into_rtrancl)
      done

    theorem rtrancl_converseD:
      assumes r: "(x, y) ∈ (r^-1)^*"
      shows "(y, x) ∈ r^*"
    proof -
      from r show ?thesis
        by induct (iprover intro: rtrancl_trans dest!: converseD)+
    qed

    theorem rtrancl_converseI:
      assumes r: "(y, x) ∈ r^*"
      shows "(x, y) ∈ (r^-1)^*"
    proof -
      from r show ?thesis
        by induct (iprover intro: rtrancl_trans converseI)+
    qed

    lemma rtrancl_converse: "(r^-1)^* = (r^*)^-1"
      by (fast dest!: rtrancl_converseD intro!: rtrancl_converseI)

    theorem converse_rtrancl_induct[consumes 1]:
      assumes major: "(a, b) : r^*"
        and cases: "P b" "!!y z. [| (y, z) : r; (z, b) : r^*; P z |] ==> P y"
      shows "P a"
    proof -
      from rtrancl_converseI [OF major]
      show ?thesis
        by induct (iprover intro: cases dest!: converseD rtrancl_converseD)+
    qed

    lemmas converse_rtrancl_induct2 =
      converse_rtrancl_induct[of "(ax,ay)" "(bx,by)", split_format (complete),
                     consumes 1, case_names refl step]

    lemma converse_rtranclE:
      "[| (x,z):r^*;
          x=z ==> P;
          !!y. [| (x,y):r; (y,z):r^* |] ==> P
       |] ==> P"
    proof -
      assume major: "(x,z):r^*"
      case rule_context
      show ?thesis
        apply (subgoal_tac "x = z | (EX y. (x,y) : r & (y,z) : r^*)")
         apply (rule_tac [2] major [THEN converse_rtrancl_induct])
          prefer 2 apply iprover
         prefer 2 apply iprover
        apply (erule asm_rl exE disjE conjE prems)+
        done
    qed

    ML_setup {*
      bind_thm ("converse_rtranclE2", split_rule
        (read_instantiate [("x","(xa,xb)"), ("z","(za,zb)")] (thm "converse_rtranclE")));
    *}

    lemma r_comp_rtrancl_eq: "r O r^* = r^* O r"
      by (blast elim: rtranclE converse_rtranclE
        intro: rtrancl_into_rtrancl converse_rtrancl_into_rtrancl)

    lemma rtrancl_unfold: "r^* = Id Un (r O r^*)"
      by (auto intro: rtrancl_into_rtrancl elim: rtranclE)

    subsection {* Transitive closure *}

    lemma trancl_mono: "!!p. p ∈ r^+ ==> r ⊆ s ==> p ∈ s^+"
      apply (simp only: split_tupled_all)
      apply (erule trancl.induct)
      apply (iprover dest: subsetD)+
      done

    lemma r_into_trancl': "!!p. p : r ==> p : r^+"
      by (simp only: split_tupled_all) (erule r_into_trancl)

    text {*
      \medskip Conversions between @{text trancl} and @{text rtrancl}.
    *}

    lemma trancl_into_rtrancl: "(a, b) ∈ r^+ ==> (a, b) ∈ r^*"
      by (erule trancl.induct) iprover+

    lemma rtrancl_into_trancl1: assumes r: "(a, b) ∈ r^*"
      shows "!!c. (b, c) ∈ r ==> (a, c) ∈ r^+" using r
      by induct iprover+

    lemma rtrancl_into_trancl2: "[| (a,b) : r;  (b,c) : r^* |]   ==>  (a,c) : r^+"
      -- {* intro rule from @{text r} and @{text rtrancl} *}
      apply (erule rtranclE, iprover)
      apply (rule rtrancl_trans [THEN rtrancl_into_trancl1])
       apply (assumption | rule r_into_rtrancl)+
      done

    lemma trancl_induct [consumes 1, induct set: trancl]:
      assumes a: "(a,b) : r^+"
      and cases: "!!y. (a, y) : r ==> P y"
        "!!y z. (a,y) : r^+ ==> (y, z) : r ==> P y ==> P z"
      shows "P b"
      -- {* Nice induction rule for @{text trancl} *}
    proof -
      from a have "a = a --> P b"
        by (induct "%x y. x = a --> P y" a b) (iprover intro: cases)+
      thus ?thesis by iprover
    qed

    lemma trancl_trans_induct:
      "[| (x,y) : r^+;
          !!x y. (x,y) : r ==> P x y;
          !!x y z. [| (x,y) : r^+; P x y; (y,z) : r^+; P y z |] ==> P x z
       |] ==> P x y"
      -- {* Another induction rule for trancl, incorporating transitivity *}
    proof -
      assume major: "(x,y) : r^+"
      case rule_context
      show ?thesis
        by (iprover intro: r_into_trancl major [THEN trancl_induct] prems)
    qed

    inductive_cases tranclE: "(a, b) : r^+"

    lemma trancl_unfold: "r^+ = r Un (r O r^+)"
      by (auto intro: trancl_into_trancl elim: tranclE)

    lemma trans_trancl: "trans(r^+)"
      -- {* Transitivity of @{term "r^+"} *}
    proof (rule transI)
      fix x y z
      assume "(x, y) ∈ r^+"
      assume "(y, z) ∈ r^+"
      thus "(x, z) ∈ r^+" by induct (iprover!)+
    qed

    lemmas trancl_trans = trans_trancl [THEN transD, standard]

    lemma rtrancl_trancl_trancl: assumes r: "(x, y) ∈ r^*"
      shows "!!z. (y, z) ∈ r^+ ==> (x, z) ∈ r^+" using r
      by induct (iprover intro: trancl_trans)+

    lemma trancl_into_trancl2: "(a, b) ∈ r ==> (b, c) ∈ r^+ ==> (a, c) ∈ r^+"
      by (erule transD [OF trans_trancl r_into_trancl])

    lemma trancl_insert:
      "(insert (y, x) r)^+ = r^+ ∪ {(a, b). (a, y) ∈ r^* ∧ (x, b) ∈ r^*}"
      -- {* primitive recursion for @{text trancl} over finite relations *}
      apply (rule equalityI)
       apply (rule subsetI)
       apply (simp only: split_tupled_all)
       apply (erule trancl_induct, blast)
       apply (blast intro: rtrancl_into_trancl1 trancl_into_rtrancl r_into_trancl trancl_trans)
      apply (rule subsetI)
      apply (blast intro: trancl_mono rtrancl_mono
        [THEN [2] rev_subsetD] rtrancl_trancl_trancl rtrancl_into_trancl2)
      done

    lemma trancl_converseI: "(x, y) ∈ (r^+)^-1 ==> (x, y) ∈ (r^-1)^+"
      apply (drule converseD)
      apply (erule trancl.induct)
      apply (iprover intro: converseI trancl_trans)+
      done

    lemma trancl_converseD: "(x, y) ∈ (r^-1)^+ ==> (x, y) ∈ (r^+)^-1"
      apply (rule converseI)
      apply (erule trancl.induct)
      apply (iprover dest: converseD intro: trancl_trans)+
      done

    lemma trancl_converse: "(r^-1)^+ = (r^+)^-1"
      by (fastsimp simp add: split_tupled_all
        intro!: trancl_converseI trancl_converseD)

    lemma converse_trancl_induct:
      "[| (a,b) : r^+; !!y. (y,b) : r ==> P(y);
          !!y z.[| (y,z) : r;  (z,b) : r^+;  P(z) |] ==> P(y) |]
        ==> P(a)"
    proof -
      assume major: "(a,b) : r^+"
      case rule_context
      show ?thesis
        apply (rule major [THEN converseI, THEN trancl_converseI [THEN trancl_induct]])
         apply (rule prems)
         apply (erule converseD)
        apply (blast intro: prems dest!: trancl_converseD)
        done
    qed

    lemma tranclD: "(x, y) ∈ R^+ ==> EX z. (x, z) ∈ R ∧ (z, y) ∈ R^*"
      apply (erule converse_trancl_induct, auto)
      apply (blast intro: rtrancl_trans)
      done

    lemma irrefl_tranclI: "r^-1 ∩ r^* = {} ==> (x, x) ∉ r^+"
    by(blast elim: tranclE dest: trancl_into_rtrancl)

    lemma irrefl_trancl_rD: "!!X. ALL x. (x, x) ∉ r^+ ==> (x, y) ∈ r ==> x ≠ y"
      by (blast dest: r_into_trancl)

    lemma trancl_subset_Sigma_aux:
        "(a, b) ∈ r^* ==> r ⊆ A × A ==> a = b ∨ a ∈ A"
      apply (erule rtrancl_induct, auto)
      done

    lemma trancl_subset_Sigma: "r ⊆ A × A ==> r^+ ⊆ A × A"
      apply (rule subsetI)
      apply (simp only: split_tupled_all)
      apply (erule tranclE)
      apply (blast dest!: trancl_into_rtrancl trancl_subset_Sigma_aux)+
      done

    lemma reflcl_trancl [simp]: "(r^+)^= = r^*"
      apply safe
       apply (erule trancl_into_rtrancl)
      apply (blast elim: rtranclE dest: rtrancl_into_trancl1)
      done

    lemma trancl_reflcl [simp]: "(r^=)^+ = r^*"
      apply safe
       apply (drule trancl_into_rtrancl, simp)
      apply (erule rtranclE, safe)
       apply (rule r_into_trancl, simp)
      apply (rule rtrancl_into_trancl1)
       apply (erule rtrancl_reflcl [THEN equalityD2, THEN subsetD], fast)
      done

    lemma trancl_empty [simp]: "{}^+ = {}"
      by (auto elim: trancl_induct)

    lemma rtrancl_empty [simp]: "{}^* = Id"
      by (rule subst [OF reflcl_trancl]) simp

    lemma rtranclD: "(a, b) ∈ R^* ==> a = b ∨ a ≠ b ∧ (a, b) ∈ R^+"
      by (force simp add: reflcl_trancl [symmetric] simp del: reflcl_trancl)

    lemma rtrancl_eq_or_trancl:
      "(x,y) ∈ R* = (x=y ∨ x≠y ∧ (x,y) ∈ R+)"
      by (fast elim: trancl_into_rtrancl dest: rtranclD)

    text {* @{text Domain} and @{text Range} *}

    lemma Domain_rtrancl [simp]: "Domain (R^*) = UNIV"
      by blast

    lemma Range_rtrancl [simp]: "Range (R^*) = UNIV"
      by blast

    lemma rtrancl_Un_subset: "(R^* ∪ S^*) ⊆ (R Un S)^*"
      by (rule rtrancl_Un_rtrancl [THEN subst]) fast

    lemma in_rtrancl_UnI: "x ∈ R^* ∨ x ∈ S^* ==> x ∈ (R ∪ S)^*"
      by (blast intro: subsetD [OF rtrancl_Un_subset])

    lemma trancl_domain [simp]: "Domain (r^+) = Domain r"
      by (unfold Domain_def) (blast dest: tranclD)

    lemma trancl_range [simp]: "Range (r^+) = Range r"
      by (simp add: Range_def trancl_converse [symmetric])

    lemma Not_Domain_rtrancl:
        "x ~: Domain R ==> ((x, y) : R^*) = (x = y)"
      apply auto
      by (erule rev_mp, erule rtrancl_induct, auto)

    text {* More about converse @{text rtrancl} and @{text trancl}, should
      be merged with main body. *}

    lemma single_valued_confluent:
      "[| single_valued r; (x,y) ∈ r^*; (x,z) ∈ r^* |]
      ==> (y,z) ∈ r^* ∨ (z,y) ∈ r^*"
    apply(erule rtrancl_induct)
     apply simp
    apply(erule disjE)
     apply(blast elim:converse_rtranclE dest:single_valuedD)
    apply(blast intro:rtrancl_trans)
    done

    lemma r_r_into_trancl: "(a, b) ∈ R ==> (b, c) ∈ R ==> (a, c) ∈ R^+"
      by (fast intro: trancl_trans)

    lemma trancl_into_trancl [rule_format]:
        "(a, b) ∈ r+ ==> (b, c) ∈ r --> (a,c) ∈ r+"
      apply (erule trancl_induct)
       apply (fast intro: r_r_into_trancl)
      apply (fast intro: r_r_into_trancl trancl_trans)
      done

    lemma trancl_rtrancl_trancl:
        "(a, b) ∈ r+ ==> (b, c) ∈ r* ==> (a, c) ∈ r+"
      apply (drule tranclD)
      apply (erule exE, erule conjE)
      apply (drule rtrancl_trans, assumption)
      apply (drule rtrancl_into_trancl2, assumption, assumption)
      done

    lemmas transitive_closure_trans [trans] =
      r_r_into_trancl trancl_trans rtrancl_trans
      trancl_into_trancl trancl_into_trancl2
      rtrancl_into_rtrancl converse_rtrancl_into_rtrancl
      rtrancl_trancl_trancl trancl_rtrancl_trancl

    declare trancl_into_rtrancl [elim]

    declare rtranclE [cases set: rtrancl]
    declare tranclE [cases set: trancl]

    subsection {* Setup of transitivity reasoner *}

    use "../Provers/trancl.ML";

    ML_setup {*

    structure Trancl_Tac = Trancl_Tac_Fun (
      struct
        val r_into_trancl = thm "r_into_trancl";
        val trancl_trans  = thm "trancl_trans";
        val rtrancl_refl = thm "rtrancl_refl";
        val r_into_rtrancl = thm "r_into_rtrancl";
        val trancl_into_rtrancl = thm "trancl_into_rtrancl";
        val rtrancl_trancl_trancl = thm "rtrancl_trancl_trancl";
        val trancl_rtrancl_trancl = thm "trancl_rtrancl_trancl";
        val rtrancl_trans = thm "rtrancl_trans";

      fun decomp (Trueprop $ t) =
        let fun dec (Const ("op :", _) $ (Const ("Pair", _) $ a $ b) $ rel ) =
            let fun decr (Const ("Transitive_Closure.rtrancl", _ ) $ r) = (r,"r*")
                  | decr (Const ("Transitive_Closure.trancl", _ ) $ r)  = (r,"r+")
                  | decr r = (r,"r");
                val (rel,r) = decr rel;
            in SOME (a,b,rel,r) end
          | dec _ =  NONE
        in dec t end;

      end); (* struct *)

    simpset_ref() := simpset ()
        addSolver (mk_solver "Trancl" (fn _ => Trancl_Tac.trancl_tac))
        addSolver (mk_solver "Rtrancl" (fn _ => Trancl_Tac.rtrancl_tac));

    *}

    (* Optional methods

    method_setup trancl =
      {* Method.no_args (Method.SIMPLE_METHOD' HEADGOAL (trancl_tac)) *}
      {* simple transitivity reasoner *}
    method_setup rtrancl =
      {* Method.no_args (Method.SIMPLE_METHOD' HEADGOAL (rtrancl_tac)) *}
      {* simple transitivity reasoner *}

    *)

    end

### Reflexive-transitive closure

lemma r_into_rtrancl:

      p ∈ r ==> p ∈ r*

lemma rtrancl_mono:

      r ⊆ s ==> r* ⊆ s*

theorem rtrancl_induct:

      [| (a, b) ∈ r*; P a; !!y z. [| (a, y) ∈ r*; (y, z) ∈ r; P y |] ==> P z |]
      ==> P b

lemmas rtrancl_induct2:

      [| ((ax, ay), bx, by) ∈ r*; P ax ay;
         !!a b aa ba.
            [| ((ax, ay), a, b) ∈ r*; ((a, b), aa, ba) ∈ r; P a b |] ==> P aa ba |]
      ==> P bx by

lemmas rtrancl_induct2:

      [| ((ax, ay), bx, by) ∈ r*; P ax ay;
         !!a b aa ba.
            [| ((ax, ay), a, b) ∈ r*; ((a, b), aa, ba) ∈ r; P a b |] ==> P aa ba |]
      ==> P bx by

lemma trans_rtrancl:

      trans (r*)

lemmas rtrancl_trans:

      [| (a, b) ∈ r*; (b, c) ∈ r* |] ==> (a, c) ∈ r*

lemmas rtrancl_trans:

      [| (a, b) ∈ r*; (b, c) ∈ r* |] ==> (a, c) ∈ r*

lemma rtranclE:

      [| (a, b) ∈ r*; a = b ==> P; !!y. [| (a, y) ∈ r*; (y, b) ∈ r |] ==> P |] ==> P

lemma converse_rtrancl_into_rtrancl:

      [| (a, b) ∈ r; (b, c) ∈ r* |] ==> (a, c) ∈ r*

lemma rtrancl_idemp:

      (r*)* = r*

lemma rtrancl_idemp_self_comp:

      R* O R* = R*

lemma rtrancl_subset_rtrancl:

      r ⊆ s* ==> r* ⊆ s*

lemma rtrancl_subset:

      [| R ⊆ S; S ⊆ R* |] ==> S* = R*

lemma rtrancl_Un_rtrancl:

      (R* ∪ S*)* = (R ∪ S)*

lemma rtrancl_reflcl:

      (R=)* = R*

lemma rtrancl_r_diff_Id:

      (r - Id)* = r*

theorem rtrancl_converseD:

      (x, y) ∈ (r^-1)* ==> (y, x) ∈ r*

theorem rtrancl_converseI:

      (y, x) ∈ r* ==> (x, y) ∈ (r^-1)*

lemma rtrancl_converse:

      (r^-1)* = (r*)^-1

theorem converse_rtrancl_induct:

      [| (a, b) ∈ r*; P b; !!y z. [| (y, z) ∈ r; (z, b) ∈ r*; P z |] ==> P y |]
      ==> P a

lemmas converse_rtrancl_induct2:

      [| ((ax, ay), bx, by) ∈ r*; P bx by;
         !!a b aa ba.
            [| ((a, b), aa, ba) ∈ r; ((aa, ba), bx, by) ∈ r*; P aa ba |] ==> P a b |]
      ==> P ax ay

lemmas converse_rtrancl_induct2:

      [| ((ax, ay), bx, by) ∈ r*; P bx by;
         !!a b aa ba.
            [| ((a, b), aa, ba) ∈ r; ((aa, ba), bx, by) ∈ r*; P aa ba |] ==> P a b |]
      ==> P ax ay

lemma converse_rtranclE:

      [| (x, z) ∈ r*; x = z ==> P; !!y. [| (x, y) ∈ r; (y, z) ∈ r* |] ==> P |] ==> P

theorem converse_rtranclE2:

      [| ((xa, xb), za, zb) ∈ r*; (xa, xb) = (za, zb) ==> P;
         !!a b. [| ((xa, xb), a, b) ∈ r; ((a, b), za, zb) ∈ r* |] ==> P |]
      ==> P

lemma r_comp_rtrancl_eq:

      r O r* = r* O r

lemma rtrancl_unfold:

      r* = Id ∪ (r O r*)

### Transitive closure

lemma trancl_mono:

      [| p ∈ r+; r ⊆ s |] ==> p ∈ s+

lemma r_into_trancl':

      p ∈ r ==> p ∈ r+

lemma trancl_into_rtrancl:

      (a, b) ∈ r+ ==> (a, b) ∈ r*

lemma rtrancl_into_trancl1:

      [| (a, b) ∈ r*; (b, c) ∈ r |] ==> (a, c) ∈ r+

lemma rtrancl_into_trancl2:

      [| (a, b) ∈ r; (b, c) ∈ r* |] ==> (a, c) ∈ r+

lemma trancl_induct:

      [| (a, b) ∈ r+; !!y. (a, y) ∈ r ==> P y;
         !!y z. [| (a, y) ∈ r+; (y, z) ∈ r; P y |] ==> P z |]
      ==> P b

lemma trancl_trans_induct:

      [| (x, y) ∈ r+; !!x y. (x, y) ∈ r ==> P x y;
         !!x y z. [| (x, y) ∈ r+; P x y; (y, z) ∈ r+; P y z |] ==> P x z |]
      ==> P x y

lemmas tranclE:

      [| (a, b) ∈ r+; (a, b) ∈ r ==> P; !!b. [| (a, b) ∈ r+; (b, b) ∈ r |] ==> P |]
      ==> P

lemma trancl_unfold:

      r+ = r ∪ (r O r+)

lemma trans_trancl:

      trans (r+)

lemmas trancl_trans:

      [| (a, b) ∈ r+; (b, c) ∈ r+ |] ==> (a, c) ∈ r+

lemmas trancl_trans:

      [| (a, b) ∈ r+; (b, c) ∈ r+ |] ==> (a, c) ∈ r+

lemma rtrancl_trancl_trancl:

      [| (x, y) ∈ r*; (y, z) ∈ r+ |] ==> (x, z) ∈ r+

lemma trancl_into_trancl2:

      [| (a, b) ∈ r; (b, c) ∈ r+ |] ==> (a, c) ∈ r+

lemma trancl_insert:

      (insert (y, x) r)+ = r+ ∪ {(a, b). (a, y) ∈ r* ∧ (x, b) ∈ r*}

lemma trancl_converseI:

      (x, y) ∈ (r+)^-1 ==> (x, y) ∈ (r^-1)+

lemma trancl_converseD:

      (x, y) ∈ (r^-1)+ ==> (x, y) ∈ (r+)^-1

lemma trancl_converse:

      (r^-1)+ = (r+)^-1

lemma converse_trancl_induct:

      [| (a, b) ∈ r+; !!y. (y, b) ∈ r ==> P y;
         !!y z. [| (y, z) ∈ r; (z, b) ∈ r+; P z |] ==> P y |]
      ==> P a

lemma tranclD:

      (x, y) ∈ R+ ==> ∃z. (x, z) ∈ R ∧ (z, y) ∈ R*

lemma irrefl_tranclI:

      r^-1 ∩ r* = {} ==> (x, x) ∉ r+

lemma irrefl_trancl_rD:

      [| ∀x. (x, x) ∉ r+; (x, y) ∈ r |] ==> x ≠ y

lemma trancl_subset_Sigma_aux:

      [| (a, b) ∈ r*; r ⊆ A × A |] ==> a = b ∨ a ∈ A

lemma trancl_subset_Sigma:

      r ⊆ A × A ==> r+ ⊆ A × A

lemma reflcl_trancl:

      (r+)= = r*

lemma trancl_reflcl:

      (r=)+ = r*

lemma trancl_empty:

      {}+ = {}

lemma rtrancl_empty:

      {}* = Id

lemma rtranclD:

      (a, b) ∈ R* ==> a = b ∨ a ≠ b ∧ (a, b) ∈ R+

lemma rtrancl_eq_or_trancl:

      ((x, y) ∈ R*) = (x = y ∨ x ≠ y ∧ (x, y) ∈ R+)

lemma Domain_rtrancl:

      Domain (R*) = UNIV

lemma Range_rtrancl:

      Range (R*) = UNIV

lemma rtrancl_Un_subset:

      R* ∪ S* ⊆ (R ∪ S)*

lemma in_rtrancl_UnI:

      x ∈ R* ∨ x ∈ S* ==> x ∈ (R ∪ S)*

lemma trancl_domain:

      Domain (r+) = Domain r

lemma trancl_range:

      Range (r+) = Range r

lemma Not_Domain_rtrancl:

      x ∉ Domain R ==> ((x, y) ∈ R*) = (x = y)

lemma single_valued_confluent:

      [| single_valued r; (x, y) ∈ r*; (x, z) ∈ r* |] ==> (y, z) ∈ r* ∨ (z, y) ∈ r*

lemma r_r_into_trancl:

      [| (a, b) ∈ R; (b, c) ∈ R |] ==> (a, c) ∈ R+

lemma trancl_into_trancl:

      [| (a, b) ∈ r+; (b, c) ∈ r |] ==> (a, c) ∈ r+

lemma trancl_rtrancl_trancl:

      [| (a, b) ∈ r+; (b, c) ∈ r* |] ==> (a, c) ∈ r+

lemmas transitive_closure_trans:

      [| (a, b) ∈ R; (b, c) ∈ R |] ==> (a, c) ∈ R+

      [| (a, b) ∈ r+; (b, c) ∈ r+ |] ==> (a, c) ∈ r+

      [| (a, b) ∈ r*; (b, c) ∈ r* |] ==> (a, c) ∈ r*

      [| (a, b) ∈ r+; (b, c) ∈ r |] ==> (a, c) ∈ r+

      [| (a, b) ∈ r; (b, c) ∈ r+ |] ==> (a, c) ∈ r+

      [| (a, b) ∈ r*; (b, c) ∈ r |] ==> (a, c) ∈ r*

      [| (a, b) ∈ r; (b, c) ∈ r* |] ==> (a, c) ∈ r*

      [| (x, y) ∈ r*; (y, z) ∈ r+ |] ==> (x, z) ∈ r+

      [| (a, b) ∈ r+; (b, c) ∈ r* |] ==> (a, c) ∈ r+

lemmas transitive_closure_trans:

      [| (a, b) ∈ R; (b, c) ∈ R |] ==> (a, c) ∈ R+

      [| (a, b) ∈ r+; (b, c) ∈ r+ |] ==> (a, c) ∈ r+

      [| (a, b) ∈ r*; (b, c) ∈ r* |] ==> (a, c) ∈ r*

      [| (a, b) ∈ r+; (b, c) ∈ r |] ==> (a, c) ∈ r+

      [| (a, b) ∈ r; (b, c) ∈ r+ |] ==> (a, c) ∈ r+

      [| (a, b) ∈ r*; (b, c) ∈ r |] ==> (a, c) ∈ r*

      [| (a, b) ∈ r; (b, c) ∈ r* |] ==> (a, c) ∈ r*

      [| (x, y) ∈ r*; (y, z) ∈ r+ |] ==> (x, z) ∈ r+

      [| (a, b) ∈ r+; (b, c) ∈ r* |] ==> (a, c) ∈ r+

### Setup of transitivity reasoner