Theory OrderArith (Isabelle2005: October 2005)

# Theory OrderArith

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theory OrderArith
imports Order Sum Ordinal
begin

    (*  Title:      ZF/OrderArith.thy
        ID:         $Id: OrderArith.thy,v 1.17 2005/06/17 14:15:09 haftmann Exp $
        Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
        Copyright   1994  University of Cambridge

    *)

    header{*Combining Orderings: Foundations of Ordinal Arithmetic*}

    theory OrderArith imports Order Sum Ordinal begin
    constdefs

      (*disjoint sum of two relations; underlies ordinal addition*)
      radd    :: "[i,i,i,i]=>i"
        "radd(A,r,B,s) ==
                    {z: (A+B) * (A+B).
                        (EX x y. z = <Inl(x), Inr(y)>)   |
                        (EX x' x. z = <Inl(x'), Inl(x)> & <x',x>:r)   |
                        (EX y' y. z = <Inr(y'), Inr(y)> & <y',y>:s)}"

      (*lexicographic product of two relations; underlies ordinal multiplication*)
      rmult   :: "[i,i,i,i]=>i"
        "rmult(A,r,B,s) ==
                    {z: (A*B) * (A*B).
                        EX x' y' x y. z = <<x',y'>, <x,y>> &
                           (<x',x>: r | (x'=x & <y',y>: s))}"

      (*inverse image of a relation*)
      rvimage :: "[i,i,i]=>i"
        "rvimage(A,f,r) == {z: A*A. EX x y. z = <x,y> & <f`x,f`y>: r}"

      measure :: "[i, i=>i] => i"
        "measure(A,f) == {<x,y>: A*A. f(x) < f(y)}"

    subsection{*Addition of Relations -- Disjoint Sum*}

    subsubsection{*Rewrite rules.  Can be used to obtain introduction rules*}

    lemma radd_Inl_Inr_iff [iff]:
        "<Inl(a), Inr(b)> : radd(A,r,B,s)  <->  a:A & b:B"
    by (unfold radd_def, blast)

    lemma radd_Inl_iff [iff]:
        "<Inl(a'), Inl(a)> : radd(A,r,B,s)  <->  a':A & a:A & <a',a>:r"
    by (unfold radd_def, blast)

    lemma radd_Inr_iff [iff]:
        "<Inr(b'), Inr(b)> : radd(A,r,B,s) <->  b':B & b:B & <b',b>:s"
    by (unfold radd_def, blast)

    lemma radd_Inr_Inl_iff [simp]:
        "<Inr(b), Inl(a)> : radd(A,r,B,s) <-> False"
    by (unfold radd_def, blast)

    declare radd_Inr_Inl_iff [THEN iffD1, dest!]

    subsubsection{*Elimination Rule*}

    lemma raddE:
        "[| <p',p> : radd(A,r,B,s);
            !!x y. [| p'=Inl(x); x:A; p=Inr(y); y:B |] ==> Q;
            !!x' x. [| p'=Inl(x'); p=Inl(x); <x',x>: r; x':A; x:A |] ==> Q;
            !!y' y. [| p'=Inr(y'); p=Inr(y); <y',y>: s; y':B; y:B |] ==> Q
         |] ==> Q"
    by (unfold radd_def, blast)

    subsubsection{*Type checking*}

    lemma radd_type: "radd(A,r,B,s) <= (A+B) * (A+B)"
    apply (unfold radd_def)
    apply (rule Collect_subset)
    done

    lemmas field_radd = radd_type [THEN field_rel_subset]

    subsubsection{*Linearity*}

    lemma linear_radd:
        "[| linear(A,r);  linear(B,s) |] ==> linear(A+B,radd(A,r,B,s))"
    by (unfold linear_def, blast)

    subsubsection{*Well-foundedness*}

    lemma wf_on_radd: "[| wf[A](r);  wf[B](s) |] ==> wf[A+B](radd(A,r,B,s))"
    apply (rule wf_onI2)
    apply (subgoal_tac "ALL x:A. Inl (x) : Ba")
     --{*Proving the lemma, which is needed twice!*}
     prefer 2
     apply (erule_tac V = "y : A + B" in thin_rl)
     apply (rule_tac ballI)
     apply (erule_tac r = r and a = x in wf_on_induct, assumption)
     apply blast
    txt{*Returning to main part of proof*}
    apply safe
    apply blast
    apply (erule_tac r = s and a = ya in wf_on_induct, assumption, blast)
    done

    lemma wf_radd: "[| wf(r);  wf(s) |] ==> wf(radd(field(r),r,field(s),s))"
    apply (simp add: wf_iff_wf_on_field)
    apply (rule wf_on_subset_A [OF _ field_radd])
    apply (blast intro: wf_on_radd)
    done

    lemma well_ord_radd:
         "[| well_ord(A,r);  well_ord(B,s) |] ==> well_ord(A+B, radd(A,r,B,s))"
    apply (rule well_ordI)
    apply (simp add: well_ord_def wf_on_radd)
    apply (simp add: well_ord_def tot_ord_def linear_radd)
    done

    subsubsection{*An @{term ord_iso} congruence law*}

    lemma sum_bij:
         "[| f: bij(A,C);  g: bij(B,D) |]
          ==> (lam z:A+B. case(%x. Inl(f`x), %y. Inr(g`y), z)) : bij(A+B, C+D)"
    apply (rule_tac d = "case (%x. Inl (converse(f)`x), %y. Inr(converse(g)`y))"
           in lam_bijective)
    apply (typecheck add: bij_is_inj inj_is_fun)
    apply (auto simp add: left_inverse_bij right_inverse_bij)
    done

    lemma sum_ord_iso_cong:
        "[| f: ord_iso(A,r,A',r');  g: ord_iso(B,s,B',s') |] ==>
                (lam z:A+B. case(%x. Inl(f`x), %y. Inr(g`y), z))
                : ord_iso(A+B, radd(A,r,B,s), A'+B', radd(A',r',B',s'))"
    apply (unfold ord_iso_def)
    apply (safe intro!: sum_bij)
    (*Do the beta-reductions now*)
    apply (auto cong add: conj_cong simp add: bij_is_fun [THEN apply_type])
    done

    (*Could we prove an ord_iso result?  Perhaps
         ord_iso(A+B, radd(A,r,B,s), A Un B, r Un s) *)
    lemma sum_disjoint_bij: "A Int B = 0 ==>
                (lam z:A+B. case(%x. x, %y. y, z)) : bij(A+B, A Un B)"
    apply (rule_tac d = "%z. if z:A then Inl (z) else Inr (z) " in lam_bijective)
    apply auto
    done

    subsubsection{*Associativity*}

    lemma sum_assoc_bij:
         "(lam z:(A+B)+C. case(case(Inl, %y. Inr(Inl(y))), %y. Inr(Inr(y)), z))
          : bij((A+B)+C, A+(B+C))"
    apply (rule_tac d = "case (%x. Inl (Inl (x)), case (%x. Inl (Inr (x)), Inr))"
           in lam_bijective)
    apply auto
    done

    lemma sum_assoc_ord_iso:
         "(lam z:(A+B)+C. case(case(Inl, %y. Inr(Inl(y))), %y. Inr(Inr(y)), z))
          : ord_iso((A+B)+C, radd(A+B, radd(A,r,B,s), C, t),
                    A+(B+C), radd(A, r, B+C, radd(B,s,C,t)))"
    by (rule sum_assoc_bij [THEN ord_isoI], auto)

    subsection{*Multiplication of Relations -- Lexicographic Product*}

    subsubsection{*Rewrite rule.  Can be used to obtain introduction rules*}

    lemma  rmult_iff [iff]:
        "<<a',b'>, <a,b>> : rmult(A,r,B,s) <->
                (<a',a>: r  & a':A & a:A & b': B & b: B) |
                (<b',b>: s  & a'=a & a:A & b': B & b: B)"

    by (unfold rmult_def, blast)

    lemma rmultE:
        "[| <<a',b'>, <a,b>> : rmult(A,r,B,s);
            [| <a',a>: r;  a':A;  a:A;  b':B;  b:B |] ==> Q;
            [| <b',b>: s;  a:A;  a'=a;  b':B;  b:B |] ==> Q
         |] ==> Q"
    by blast

    subsubsection{*Type checking*}

    lemma rmult_type: "rmult(A,r,B,s) <= (A*B) * (A*B)"
    by (unfold rmult_def, rule Collect_subset)

    lemmas field_rmult = rmult_type [THEN field_rel_subset]

    subsubsection{*Linearity*}

    lemma linear_rmult:
        "[| linear(A,r);  linear(B,s) |] ==> linear(A*B,rmult(A,r,B,s))"
    by (simp add: linear_def, blast)

    subsubsection{*Well-foundedness*}

    lemma wf_on_rmult: "[| wf[A](r);  wf[B](s) |] ==> wf[A*B](rmult(A,r,B,s))"
    apply (rule wf_onI2)
    apply (erule SigmaE)
    apply (erule ssubst)
    apply (subgoal_tac "ALL b:B. <x,b>: Ba", blast)
    apply (erule_tac a = x in wf_on_induct, assumption)
    apply (rule ballI)
    apply (erule_tac a = b in wf_on_induct, assumption)
    apply (best elim!: rmultE bspec [THEN mp])
    done

    lemma wf_rmult: "[| wf(r);  wf(s) |] ==> wf(rmult(field(r),r,field(s),s))"
    apply (simp add: wf_iff_wf_on_field)
    apply (rule wf_on_subset_A [OF _ field_rmult])
    apply (blast intro: wf_on_rmult)
    done

    lemma well_ord_rmult:
         "[| well_ord(A,r);  well_ord(B,s) |] ==> well_ord(A*B, rmult(A,r,B,s))"
    apply (rule well_ordI)
    apply (simp add: well_ord_def wf_on_rmult)
    apply (simp add: well_ord_def tot_ord_def linear_rmult)
    done

    subsubsection{*An @{term ord_iso} congruence law*}

    lemma prod_bij:
         "[| f: bij(A,C);  g: bij(B,D) |]
          ==> (lam <x,y>:A*B. <f`x, g`y>) : bij(A*B, C*D)"
    apply (rule_tac d = "%<x,y>. <converse (f) `x, converse (g) `y>"
           in lam_bijective)
    apply (typecheck add: bij_is_inj inj_is_fun)
    apply (auto simp add: left_inverse_bij right_inverse_bij)
    done

    lemma prod_ord_iso_cong:
        "[| f: ord_iso(A,r,A',r');  g: ord_iso(B,s,B',s') |]
         ==> (lam <x,y>:A*B. <f`x, g`y>)
             : ord_iso(A*B, rmult(A,r,B,s), A'*B', rmult(A',r',B',s'))"
    apply (unfold ord_iso_def)
    apply (safe intro!: prod_bij)
    apply (simp_all add: bij_is_fun [THEN apply_type])
    apply (blast intro: bij_is_inj [THEN inj_apply_equality])
    done

    lemma singleton_prod_bij: "(lam z:A. <x,z>) : bij(A, {x}*A)"
    by (rule_tac d = snd in lam_bijective, auto)

    (*Used??*)
    lemma singleton_prod_ord_iso:
         "well_ord({x},xr) ==>
              (lam z:A. <x,z>) : ord_iso(A, r, {x}*A, rmult({x}, xr, A, r))"
    apply (rule singleton_prod_bij [THEN ord_isoI])
    apply (simp (no_asm_simp))
    apply (blast dest: well_ord_is_wf [THEN wf_on_not_refl])
    done

    (*Here we build a complicated function term, then simplify it using
      case_cong, id_conv, comp_lam, case_case.*)
    lemma prod_sum_singleton_bij:
         "a~:C ==>
           (lam x:C*B + D. case(%x. x, %y.<a,y>, x))
           : bij(C*B + D, C*B Un {a}*D)"
    apply (rule subst_elem)
    apply (rule id_bij [THEN sum_bij, THEN comp_bij])
    apply (rule singleton_prod_bij)
    apply (rule sum_disjoint_bij, blast)
    apply (simp (no_asm_simp) cong add: case_cong)
    apply (rule comp_lam [THEN trans, symmetric])
    apply (fast elim!: case_type)
    apply (simp (no_asm_simp) add: case_case)
    done

    lemma prod_sum_singleton_ord_iso:
     "[| a:A;  well_ord(A,r) |] ==>
        (lam x:pred(A,a,r)*B + pred(B,b,s). case(%x. x, %y.<a,y>, x))
        : ord_iso(pred(A,a,r)*B + pred(B,b,s),
                      radd(A*B, rmult(A,r,B,s), B, s),
                  pred(A,a,r)*B Un {a}*pred(B,b,s), rmult(A,r,B,s))"
    apply (rule prod_sum_singleton_bij [THEN ord_isoI])
    apply (simp (no_asm_simp) add: pred_iff well_ord_is_wf [THEN wf_on_not_refl])
    apply (auto elim!: well_ord_is_wf [THEN wf_on_asym] predE)
    done

    subsubsection{*Distributive law*}

    lemma sum_prod_distrib_bij:
         "(lam <x,z>:(A+B)*C. case(%y. Inl(<y,z>), %y. Inr(<y,z>), x))
          : bij((A+B)*C, (A*C)+(B*C))"
    by (rule_tac d = "case (%<x,y>.<Inl (x),y>, %<x,y>.<Inr (x),y>) "
        in lam_bijective, auto)

    lemma sum_prod_distrib_ord_iso:
     "(lam <x,z>:(A+B)*C. case(%y. Inl(<y,z>), %y. Inr(<y,z>), x))
      : ord_iso((A+B)*C, rmult(A+B, radd(A,r,B,s), C, t),
                (A*C)+(B*C), radd(A*C, rmult(A,r,C,t), B*C, rmult(B,s,C,t)))"
    by (rule sum_prod_distrib_bij [THEN ord_isoI], auto)

    subsubsection{*Associativity*}

    lemma prod_assoc_bij:
         "(lam <<x,y>, z>:(A*B)*C. <x,<y,z>>) : bij((A*B)*C, A*(B*C))"
    by (rule_tac d = "%<x, <y,z>>. <<x,y>, z>" in lam_bijective, auto)

    lemma prod_assoc_ord_iso:
     "(lam <<x,y>, z>:(A*B)*C. <x,<y,z>>)
      : ord_iso((A*B)*C, rmult(A*B, rmult(A,r,B,s), C, t),
                A*(B*C), rmult(A, r, B*C, rmult(B,s,C,t)))"
    by (rule prod_assoc_bij [THEN ord_isoI], auto)

    subsection{*Inverse Image of a Relation*}

    subsubsection{*Rewrite rule*}

    lemma rvimage_iff: "<a,b> : rvimage(A,f,r)  <->  <f`a,f`b>: r & a:A & b:A"
    by (unfold rvimage_def, blast)

    subsubsection{*Type checking*}

    lemma rvimage_type: "rvimage(A,f,r) <= A*A"
    by (unfold rvimage_def, rule Collect_subset)

    lemmas field_rvimage = rvimage_type [THEN field_rel_subset]

    lemma rvimage_converse: "rvimage(A,f, converse(r)) = converse(rvimage(A,f,r))"
    by (unfold rvimage_def, blast)

    subsubsection{*Partial Ordering Properties*}

    lemma irrefl_rvimage:
        "[| f: inj(A,B);  irrefl(B,r) |] ==> irrefl(A, rvimage(A,f,r))"
    apply (unfold irrefl_def rvimage_def)
    apply (blast intro: inj_is_fun [THEN apply_type])
    done

    lemma trans_on_rvimage:
        "[| f: inj(A,B);  trans[B](r) |] ==> trans[A](rvimage(A,f,r))"
    apply (unfold trans_on_def rvimage_def)
    apply (blast intro: inj_is_fun [THEN apply_type])
    done

    lemma part_ord_rvimage:
        "[| f: inj(A,B);  part_ord(B,r) |] ==> part_ord(A, rvimage(A,f,r))"
    apply (unfold part_ord_def)
    apply (blast intro!: irrefl_rvimage trans_on_rvimage)
    done

    subsubsection{*Linearity*}

    lemma linear_rvimage:
        "[| f: inj(A,B);  linear(B,r) |] ==> linear(A,rvimage(A,f,r))"
    apply (simp add: inj_def linear_def rvimage_iff)
    apply (blast intro: apply_funtype)
    done

    lemma tot_ord_rvimage:
        "[| f: inj(A,B);  tot_ord(B,r) |] ==> tot_ord(A, rvimage(A,f,r))"
    apply (unfold tot_ord_def)
    apply (blast intro!: part_ord_rvimage linear_rvimage)
    done

    subsubsection{*Well-foundedness*}

    lemma wf_rvimage [intro!]: "wf(r) ==> wf(rvimage(A,f,r))"
    apply (simp (no_asm_use) add: rvimage_def wf_eq_minimal)
    apply clarify
    apply (subgoal_tac "EX w. w : {w: {f`x. x:Q}. EX x. x: Q & (f`x = w) }")
     apply (erule allE)
     apply (erule impE)
     apply assumption
     apply blast
    apply blast
    done

    text{*But note that the combination of @{text wf_imp_wf_on} and
     @{text wf_rvimage} gives @{term "wf(r) ==> wf[C](rvimage(A,f,r))"}*}
    lemma wf_on_rvimage: "[| f: A->B;  wf[B](r) |] ==> wf[A](rvimage(A,f,r))"
    apply (rule wf_onI2)
    apply (subgoal_tac "ALL z:A. f`z=f`y --> z: Ba")
     apply blast
    apply (erule_tac a = "f`y" in wf_on_induct)
     apply (blast intro!: apply_funtype)
    apply (blast intro!: apply_funtype dest!: rvimage_iff [THEN iffD1])
    done

    (*Note that we need only wf[A](...) and linear(A,...) to get the result!*)
    lemma well_ord_rvimage:
         "[| f: inj(A,B);  well_ord(B,r) |] ==> well_ord(A, rvimage(A,f,r))"
    apply (rule well_ordI)
    apply (unfold well_ord_def tot_ord_def)
    apply (blast intro!: wf_on_rvimage inj_is_fun)
    apply (blast intro!: linear_rvimage)
    done

    lemma ord_iso_rvimage:
        "f: bij(A,B) ==> f: ord_iso(A, rvimage(A,f,s), B, s)"
    apply (unfold ord_iso_def)
    apply (simp add: rvimage_iff)
    done

    lemma ord_iso_rvimage_eq:
        "f: ord_iso(A,r, B,s) ==> rvimage(A,f,s) = r Int A*A"
    by (unfold ord_iso_def rvimage_def, blast)

    subsection{*Every well-founded relation is a subset of some inverse image of
          an ordinal*}

    lemma wf_rvimage_Ord: "Ord(i) ==> wf(rvimage(A, f, Memrel(i)))"
    by (blast intro: wf_rvimage wf_Memrel)

    constdefs
      wfrank :: "[i,i]=>i"
        "wfrank(r,a) == wfrec(r, a, %x f. \<Union>y ∈ r-``{x}. succ(f`y))"

    constdefs
      wftype :: "i=>i"
        "wftype(r) == \<Union>y ∈ range(r). succ(wfrank(r,y))"

    lemma wfrank: "wf(r) ==> wfrank(r,a) = (\<Union>y ∈ r-``{a}. succ(wfrank(r,y)))"
    by (subst wfrank_def [THEN def_wfrec], simp_all)

    lemma Ord_wfrank: "wf(r) ==> Ord(wfrank(r,a))"
    apply (rule_tac a=a in wf_induct, assumption)
    apply (subst wfrank, assumption)
    apply (rule Ord_succ [THEN Ord_UN], blast)
    done

    lemma wfrank_lt: "[|wf(r); <a,b> ∈ r|] ==> wfrank(r,a) < wfrank(r,b)"
    apply (rule_tac a1 = b in wfrank [THEN ssubst], assumption)
    apply (rule UN_I [THEN ltI])
    apply (simp add: Ord_wfrank vimage_iff)+
    done

    lemma Ord_wftype: "wf(r) ==> Ord(wftype(r))"
    by (simp add: wftype_def Ord_wfrank)

    lemma wftypeI: "[|wf(r);  x ∈ field(r)|] ==> wfrank(r,x) ∈ wftype(r)"
    apply (simp add: wftype_def)
    apply (blast intro: wfrank_lt [THEN ltD])
    done

    lemma wf_imp_subset_rvimage:
         "[|wf(r); r ⊆ A*A|] ==> ∃i f. Ord(i) & r <= rvimage(A, f, Memrel(i))"
    apply (rule_tac x="wftype(r)" in exI)
    apply (rule_tac x="λx∈A. wfrank(r,x)" in exI)
    apply (simp add: Ord_wftype, clarify)
    apply (frule subsetD, assumption, clarify)
    apply (simp add: rvimage_iff wfrank_lt [THEN ltD])
    apply (blast intro: wftypeI)
    done

    theorem wf_iff_subset_rvimage:
      "relation(r) ==> wf(r) <-> (∃i f A. Ord(i) & r <= rvimage(A, f, Memrel(i)))"
    by (blast dest!: relation_field_times_field wf_imp_subset_rvimage
              intro: wf_rvimage_Ord [THEN wf_subset])

    subsection{*Other Results*}

    lemma wf_times: "A Int B = 0 ==> wf(A*B)"
    by (simp add: wf_def, blast)

    text{*Could also be used to prove @{text wf_radd}*}
    lemma wf_Un:
         "[| range(r) Int domain(s) = 0; wf(r);  wf(s) |] ==> wf(r Un s)"
    apply (simp add: wf_def, clarify)
    apply (rule equalityI)
     prefer 2 apply blast
    apply clarify
    apply (drule_tac x=Z in spec)
    apply (drule_tac x="Z Int domain(s)" in spec)
    apply simp
    apply (blast intro: elim: equalityE)
    done

    subsubsection{*The Empty Relation*}

    lemma wf0: "wf(0)"
    by (simp add: wf_def, blast)

    lemma linear0: "linear(0,0)"
    by (simp add: linear_def)

    lemma well_ord0: "well_ord(0,0)"
    by (blast intro: wf_imp_wf_on well_ordI wf0 linear0)

    subsubsection{*The "measure" relation is useful with wfrec*}

    lemma measure_eq_rvimage_Memrel:
         "measure(A,f) = rvimage(A,Lambda(A,f),Memrel(Collect(RepFun(A,f),Ord)))"
    apply (simp (no_asm) add: measure_def rvimage_def Memrel_iff)
    apply (rule equalityI, auto)
    apply (auto intro: Ord_in_Ord simp add: lt_def)
    done

    lemma wf_measure [iff]: "wf(measure(A,f))"
    by (simp (no_asm) add: measure_eq_rvimage_Memrel wf_Memrel wf_rvimage)

    lemma measure_iff [iff]: "<x,y> : measure(A,f) <-> x:A & y:A & f(x)<f(y)"
    by (simp (no_asm) add: measure_def)

    lemma linear_measure:
     assumes Ordf: "!!x. x ∈ A ==> Ord(f(x))"
         and inj:  "!!x y. [|x ∈ A; y ∈ A; f(x) = f(y) |] ==> x=y"
     shows "linear(A, measure(A,f))"
    apply (auto simp add: linear_def)
    apply (rule_tac i="f(x)" and j="f(y)" in Ord_linear_lt)
        apply (simp_all add: Ordf)
    apply (blast intro: inj)
    done

    lemma wf_on_measure: "wf[B](measure(A,f))"
    by (rule wf_imp_wf_on [OF wf_measure])

    lemma well_ord_measure:
     assumes Ordf: "!!x. x ∈ A ==> Ord(f(x))"
         and inj:  "!!x y. [|x ∈ A; y ∈ A; f(x) = f(y) |] ==> x=y"
     shows "well_ord(A, measure(A,f))"
    apply (rule well_ordI)
    apply (rule wf_on_measure)
    apply (blast intro: linear_measure Ordf inj)
    done

    lemma measure_type: "measure(A,f) <= A*A"
    by (auto simp add: measure_def)

    subsubsection{*Well-foundedness of Unions*}

    lemma wf_on_Union:
     assumes wfA: "wf[A](r)"
         and wfB: "!!a. a∈A ==> wf[B(a)](s)"
         and ok: "!!a u v. [|<u,v> ∈ s; v ∈ B(a); a ∈ A|]
                           ==> (∃a'∈A. <a',a> ∈ r & u ∈ B(a')) | u ∈ B(a)"
     shows "wf[\<Union>a∈A. B(a)](s)"
    apply (rule wf_onI2)
    apply (erule UN_E)
    apply (subgoal_tac "∀z ∈ B(a). z ∈ Ba", blast)
    apply (rule_tac a = a in wf_on_induct [OF wfA], assumption)
    apply (rule ballI)
    apply (rule_tac a = z in wf_on_induct [OF wfB], assumption, assumption)
    apply (rename_tac u)
    apply (drule_tac x=u in bspec, blast)
    apply (erule mp, clarify)
    apply (frule ok, assumption+, blast)
    done

    subsubsection{*Bijections involving Powersets*}

    lemma Pow_sum_bij:
        "(λZ ∈ Pow(A+B). <{x ∈ A. Inl(x) ∈ Z}, {y ∈ B. Inr(y) ∈ Z}>)
         ∈ bij(Pow(A+B), Pow(A)*Pow(B))"
    apply (rule_tac d = "%<X,Y>. {Inl (x). x ∈ X} Un {Inr (y). y ∈ Y}"
           in lam_bijective)
    apply force+
    done

    text{*As a special case, we have @{term "bij(Pow(A*B), A -> Pow(B))"} *}
    lemma Pow_Sigma_bij:
        "(λr ∈ Pow(Sigma(A,B)). λx ∈ A. r``{x})
         ∈ bij(Pow(Sigma(A,B)), Π x ∈ A. Pow(B(x)))"
    apply (rule_tac d = "%f. \<Union>x ∈ A. \<Union>y ∈ f`x. {<x,y>}" in lam_bijective)
    apply (blast intro: lam_type)
    apply (blast dest: apply_type, simp_all)
    apply fast (*strange, but blast can't do it*)
    apply (rule fun_extension, auto)
    by blast

    ML {*
    val measure_def = thm "measure_def";
    val radd_Inl_Inr_iff = thm "radd_Inl_Inr_iff";
    val radd_Inl_iff = thm "radd_Inl_iff";
    val radd_Inr_iff = thm "radd_Inr_iff";
    val radd_Inr_Inl_iff = thm "radd_Inr_Inl_iff";
    val raddE = thm "raddE";
    val radd_type = thm "radd_type";
    val field_radd = thm "field_radd";
    val linear_radd = thm "linear_radd";
    val wf_on_radd = thm "wf_on_radd";
    val wf_radd = thm "wf_radd";
    val well_ord_radd = thm "well_ord_radd";
    val sum_bij = thm "sum_bij";
    val sum_ord_iso_cong = thm "sum_ord_iso_cong";
    val sum_disjoint_bij = thm "sum_disjoint_bij";
    val sum_assoc_bij = thm "sum_assoc_bij";
    val sum_assoc_ord_iso = thm "sum_assoc_ord_iso";
    val rmult_iff = thm "rmult_iff";
    val rmultE = thm "rmultE";
    val rmult_type = thm "rmult_type";
    val field_rmult = thm "field_rmult";
    val linear_rmult = thm "linear_rmult";
    val wf_on_rmult = thm "wf_on_rmult";
    val wf_rmult = thm "wf_rmult";
    val well_ord_rmult = thm "well_ord_rmult";
    val prod_bij = thm "prod_bij";
    val prod_ord_iso_cong = thm "prod_ord_iso_cong";
    val singleton_prod_bij = thm "singleton_prod_bij";
    val singleton_prod_ord_iso = thm "singleton_prod_ord_iso";
    val prod_sum_singleton_bij = thm "prod_sum_singleton_bij";
    val prod_sum_singleton_ord_iso = thm "prod_sum_singleton_ord_iso";
    val sum_prod_distrib_bij = thm "sum_prod_distrib_bij";
    val sum_prod_distrib_ord_iso = thm "sum_prod_distrib_ord_iso";
    val prod_assoc_bij = thm "prod_assoc_bij";
    val prod_assoc_ord_iso = thm "prod_assoc_ord_iso";
    val rvimage_iff = thm "rvimage_iff";
    val rvimage_type = thm "rvimage_type";
    val field_rvimage = thm "field_rvimage";
    val rvimage_converse = thm "rvimage_converse";
    val irrefl_rvimage = thm "irrefl_rvimage";
    val trans_on_rvimage = thm "trans_on_rvimage";
    val part_ord_rvimage = thm "part_ord_rvimage";
    val linear_rvimage = thm "linear_rvimage";
    val tot_ord_rvimage = thm "tot_ord_rvimage";
    val wf_rvimage = thm "wf_rvimage";
    val wf_on_rvimage = thm "wf_on_rvimage";
    val well_ord_rvimage = thm "well_ord_rvimage";
    val ord_iso_rvimage = thm "ord_iso_rvimage";
    val ord_iso_rvimage_eq = thm "ord_iso_rvimage_eq";
    val measure_eq_rvimage_Memrel = thm "measure_eq_rvimage_Memrel";
    val wf_measure = thm "wf_measure";
    val measure_iff = thm "measure_iff";
    *}

    end

### Addition of Relations -- Disjoint Sum

#### Rewrite rules. Can be used to obtain introduction rules

lemma radd_Inl_Inr_iff:

      ⟨Inl(a), Inr(b)⟩ ∈ radd(A, r, B, s) <-> a ∈ A ∧ b ∈ B

lemma radd_Inl_iff:

      ⟨Inl(a'), Inl(a)⟩ ∈ radd(A, r, B, s) <-> a' ∈ A ∧ a ∈ A ∧ ⟨a', a⟩ ∈ r

lemma radd_Inr_iff:

      ⟨Inr(b'), Inr(b)⟩ ∈ radd(A, r, B, s) <-> b' ∈ B ∧ b ∈ B ∧ ⟨b', b⟩ ∈ s

lemma radd_Inr_Inl_iff:

      ⟨Inr(b), Inl(a)⟩ ∈ radd(A, r, B, s) <-> False

#### Elimination Rule

lemma raddE:

      [| ⟨p', p⟩ ∈ radd(A, r, B, s);
         !!x y. [| p' = Inl(x); x ∈ A; p = Inr(y); y ∈ B |] ==> Q;
         !!x' x. [| p' = Inl(x'); p = Inl(x); ⟨x', x⟩ ∈ r; x' ∈ A; x ∈ A |] ==> Q;
         !!y' y. [| p' = Inr(y'); p = Inr(y); ⟨y', y⟩ ∈ s; y' ∈ B; y ∈ B |] ==> Q |]
      ==> Q

#### Type checking

lemma radd_type:

      radd(A, r, B, s) ⊆ (A + B) × (A + B)

lemmas field_radd:

      field(radd(A1, r1, B1, s1)) ⊆ A1 + B1

lemmas field_radd:

      field(radd(A1, r1, B1, s1)) ⊆ A1 + B1

#### Linearity

lemma linear_radd:

      [| linear(A, r); linear(B, s) |] ==> linear(A + B, radd(A, r, B, s))

#### Well-foundedness

lemma wf_on_radd:

      [| wf[A](r); wf[B](s) |] ==> wf[A + B](radd(A, r, B, s))

lemma wf_radd:

      [| wf(r); wf(s) |] ==> wf(radd(field(r), r, field(s), s))

lemma well_ord_radd:

      [| well_ord(A, r); well_ord(B, s) |] ==> well_ord(A + B, radd(A, r, B, s))

#### An @{term ord_iso} congruence law

lemma sum_bij:

      [| f ∈ bij(A, C); g ∈ bij(B, D) |]
      ==> (λz∈A + B. case(%x. Inl(f ` x), %y. Inr(g ` y), z)) ∈ bij(A + B, C + D)

lemma sum_ord_iso_cong:

      [| f ∈ ord_iso(A, r, A', r'); g ∈ ord_iso(B, s, B', s') |]
      ==> (λz∈A + B. case(%x. Inl(f ` x), %y. Inr(g ` y), z)) ∈
          ord_iso(A + B, radd(A, r, B, s), A' + B', radd(A', r', B', s'))

lemma sum_disjoint_bij:

      A ∩ B = 0 ==> (λz∈A + B. case(%x. x, %y. y, z)) ∈ bij(A + B, A ∪ B)

#### Associativity

lemma sum_assoc_bij:

      (λz∈(A + B) + C. case(case(Inl, %y. Inr(Inl(y))), %y. Inr(Inr(y)), z)) ∈
      bij((A + B) + C, A + B + C)

lemma sum_assoc_ord_iso:

      (λz∈(A + B) + C. case(case(Inl, %y. Inr(Inl(y))), %y. Inr(Inr(y)), z)) ∈
      ord_iso
       ((A + B) + C, radd(A + B, radd(A, r, B, s), C, t), A + B + C,
        radd(A, r, B + C, radd(B, s, C, t)))

### Multiplication of Relations -- Lexicographic Product

#### Rewrite rule. Can be used to obtain introduction rules

lemma rmult_iff:

      ⟨⟨a', b'⟩, a, b⟩ ∈ rmult(A, r, B, s) <->
      ⟨a', a⟩ ∈ r ∧ a' ∈ A ∧ a ∈ A ∧ b' ∈ B ∧ b ∈ B ∨
      ⟨b', b⟩ ∈ s ∧ a' = a ∧ a ∈ A ∧ b' ∈ B ∧ b ∈ B

lemma rmultE:

      [| ⟨⟨a', b'⟩, a, b⟩ ∈ rmult(A, r, B, s);
         [| ⟨a', a⟩ ∈ r; a' ∈ A; a ∈ A; b' ∈ B; b ∈ B |] ==> Q;
         [| ⟨b', b⟩ ∈ s; a ∈ A; a' = a; b' ∈ B; b ∈ B |] ==> Q |]
      ==> Q

#### Type checking

lemma rmult_type:

      rmult(A, r, B, s) ⊆ (A × B) × A × B

lemmas field_rmult:

      field(rmult(A1, r1, B1, s1)) ⊆ A1 × B1

lemmas field_rmult:

      field(rmult(A1, r1, B1, s1)) ⊆ A1 × B1

#### Linearity

lemma linear_rmult:

      [| linear(A, r); linear(B, s) |] ==> linear(A × B, rmult(A, r, B, s))

#### Well-foundedness

lemma wf_on_rmult:

      [| wf[A](r); wf[B](s) |] ==> wf[A × B](rmult(A, r, B, s))

lemma wf_rmult:

      [| wf(r); wf(s) |] ==> wf(rmult(field(r), r, field(s), s))

lemma well_ord_rmult:

      [| well_ord(A, r); well_ord(B, s) |] ==> well_ord(A × B, rmult(A, r, B, s))

#### An @{term ord_iso} congruence law

lemma prod_bij:

      [| f ∈ bij(A, C); g ∈ bij(B, D) |]
      ==> (λ⟨x,y⟩∈A × B. ⟨f ` x, g ` y⟩) ∈ bij(A × B, C × D)

lemma prod_ord_iso_cong:

      [| f ∈ ord_iso(A, r, A', r'); g ∈ ord_iso(B, s, B', s') |]
      ==> (λ⟨x,y⟩∈A × B. ⟨f ` x, g ` y⟩) ∈
          ord_iso(A × B, rmult(A, r, B, s), A' × B', rmult(A', r', B', s'))

lemma singleton_prod_bij:

      (λz∈A. ⟨x, z⟩) ∈ bij(A, {x} × A)

lemma singleton_prod_ord_iso:

      well_ord({x}, xr)
      ==> (λz∈A. ⟨x, z⟩) ∈ ord_iso(A, r, {x} × A, rmult({x}, xr, A, r))

lemma prod_sum_singleton_bij:

      a ∉ C
      ==> (λx∈C × B + D. case(%x. x, %y. ⟨a, y⟩, x)) ∈ bij(C × B + D, C × B ∪ {a} × D)

lemma prod_sum_singleton_ord_iso:

      [| a ∈ A; well_ord(A, r) |]
      ==> (λx∈pred(A, a, r) × B + pred(B, b, s). case(%x. x, %y. ⟨a, y⟩, x)) ∈
          ord_iso
           (pred(A, a, r) × B + pred(B, b, s), radd(A × B, rmult(A, r, B, s), B, s),
            pred(A, a, r) × B ∪ {a} × pred(B, b, s), rmult(A, r, B, s))

#### Distributive law

lemma sum_prod_distrib_bij:

      (λ⟨x,z⟩∈(A + B) × C. case(%y. Inl(⟨y, z⟩), %y. Inr(⟨y, z⟩), x)) ∈
      bij((A + B) × C, A × C + B × C)

lemma sum_prod_distrib_ord_iso:

      (λ⟨x,z⟩∈(A + B) × C. case(%y. Inl(⟨y, z⟩), %y. Inr(⟨y, z⟩), x)) ∈
      ord_iso
       ((A + B) × C, rmult(A + B, radd(A, r, B, s), C, t), A × C + B × C,
        radd(A × C, rmult(A, r, C, t), B × C, rmult(B, s, C, t)))

#### Associativity

lemma prod_assoc_bij:

      (λ⟨⟨x,y⟩,z⟩∈(A × B) × C. ⟨x, y, z⟩) ∈ bij((A × B) × C, A × B × C)

lemma prod_assoc_ord_iso:

      (λ⟨⟨x,y⟩,z⟩∈(A × B) × C. ⟨x, y, z⟩) ∈
      ord_iso
       ((A × B) × C, rmult(A × B, rmult(A, r, B, s), C, t), A × B × C,
        rmult(A, r, B × C, rmult(B, s, C, t)))

### Inverse Image of a Relation

#### Rewrite rule

lemma rvimage_iff:

      ⟨a, b⟩ ∈ rvimage(A, f, r) <-> ⟨f ` a, f ` b⟩ ∈ r ∧ a ∈ A ∧ b ∈ A

#### Type checking

lemma rvimage_type:

      rvimage(A, f, r) ⊆ A × A

lemmas field_rvimage:

      field(rvimage(A, f1, r1)) ⊆ A

lemmas field_rvimage:

      field(rvimage(A, f1, r1)) ⊆ A

lemma rvimage_converse:

      rvimage(A, f, converse(r)) = converse(rvimage(A, f, r))

#### Partial Ordering Properties

lemma irrefl_rvimage:

      [| f ∈ inj(A, B); irrefl(B, r) |] ==> irrefl(A, rvimage(A, f, r))

lemma trans_on_rvimage:

      [| f ∈ inj(A, B); trans[B](r) |] ==> trans[A](rvimage(A, f, r))

lemma part_ord_rvimage:

      [| f ∈ inj(A, B); part_ord(B, r) |] ==> part_ord(A, rvimage(A, f, r))

#### Linearity

lemma linear_rvimage:

      [| f ∈ inj(A, B); linear(B, r) |] ==> linear(A, rvimage(A, f, r))

lemma tot_ord_rvimage:

      [| f ∈ inj(A, B); tot_ord(B, r) |] ==> tot_ord(A, rvimage(A, f, r))

#### Well-foundedness

lemma wf_rvimage:

      wf(r) ==> wf(rvimage(A, f, r))

lemma wf_on_rvimage:

      [| f ∈ A -> B; wf[B](r) |] ==> wf[A](rvimage(A, f, r))

lemma well_ord_rvimage:

      [| f ∈ inj(A, B); well_ord(B, r) |] ==> well_ord(A, rvimage(A, f, r))

lemma ord_iso_rvimage:

      f ∈ bij(A, B) ==> f ∈ ord_iso(A, rvimage(A, f, s), B, s)

lemma ord_iso_rvimage_eq:

      f ∈ ord_iso(A, r, B, s) ==> rvimage(A, f, s) = r ∩ A × A

### Every well-founded relation is a subset of some inverse image of an ordinal

lemma wf_rvimage_Ord:

      Ord(i) ==> wf(rvimage(A, f, Memrel(i)))

lemma wfrank:

      wf(r) ==> wfrank(r, a) = (\<Union>y∈r -`` {a}. succ(wfrank(r, y)))

lemma Ord_wfrank:

      wf(r) ==> Ord(wfrank(r, a))

lemma wfrank_lt:

      [| wf(r); ⟨a, b⟩ ∈ r |] ==> wfrank(r, a) < wfrank(r, b)

lemma Ord_wftype:

      wf(r) ==> Ord(wftype(r))

lemma wftypeI:

      [| wf(r); x ∈ field(r) |] ==> wfrank(r, x) ∈ wftype(r)

lemma wf_imp_subset_rvimage:

      [| wf(r); r ⊆ A × A |] ==> ∃i f. Ord(i) ∧ r ⊆ rvimage(A, f, Memrel(i))

theorem wf_iff_subset_rvimage:

      relation(r) ==> wf(r) <-> (∃i f A. Ord(i) ∧ r ⊆ rvimage(A, f, Memrel(i)))

### Other Results

lemma wf_times:

      A ∩ B = 0 ==> wf(A × B)

lemma wf_Un:

      [| range(r) ∩ domain(s) = 0; wf(r); wf(s) |] ==> wf(r ∪ s)

#### The Empty Relation

lemma wf0:

      wf(0)

lemma linear0:

      linear(0, 0)

lemma well_ord0:

      well_ord(0, 0)

#### The "measure" relation is useful with wfrec

lemma measure_eq_rvimage_Memrel:

      measure(A, f) = rvimage(A, Lambda(A, f), Memrel(Collect(RepFun(A, f), Ord)))

lemma wf_measure:

      wf(measure(A, f))

lemma measure_iff:

      ⟨x, y⟩ ∈ measure(A, f) <-> x ∈ A ∧ y ∈ A ∧ f(x) < f(y)

lemma linear_measure:

      [| !!x. x ∈ A ==> Ord(f(x)); !!x y. [| x ∈ A; y ∈ A; f(x) = f(y) |] ==> x = y |]
      ==> linear(A, measure(A, f))

lemma wf_on_measure:

      wf[B](measure(A, f))

lemma well_ord_measure:

      [| !!x. x ∈ A ==> Ord(f(x)); !!x y. [| x ∈ A; y ∈ A; f(x) = f(y) |] ==> x = y |]
      ==> well_ord(A, measure(A, f))

lemma measure_type:

      measure(A, f) ⊆ A × A

#### Well-foundedness of Unions

lemma wf_on_Union:

      [| wf[A](r); !!a. a ∈ A ==> wf[B(a)](s);
         !!a u v.
            [| ⟨u, v⟩ ∈ s; v ∈ B(a); a ∈ A |]
            ==> (∃a'∈A. ⟨a', a⟩ ∈ r ∧ u ∈ B(a')) ∨ u ∈ B(a) |]
      ==> wf[\<Union>a∈A. B(a)](s)

#### Bijections involving Powersets

lemma Pow_sum_bij:

      (λZ∈Pow(A + B). ⟨{x ∈ A . Inl(x) ∈ Z}, {y ∈ B . Inr(y) ∈ Z}⟩) ∈
      bij(Pow(A + B), Pow(A) × Pow(B))

lemma Pow_Sigma_bij:

      (λr∈Pow(Sigma(A, B)). λx∈A. r `` {x}) ∈ bij(Pow(Sigma(A, B)), Πx∈A. Pow(B(x)))