Theory Set (Isabelle2005: October 2005)

# Theory Set

Up to index of Isabelle/HOL

theory Set
imports LOrder
uses [Set.ML]
begin

    (*  Title:      HOL/Set.thy
        ID:         $Id: Set.thy,v 1.101 2005/09/29 10:43:40 paulson Exp $
        Author:     Tobias Nipkow, Lawrence C Paulson and Markus Wenzel
    *)

    header {* Set theory for higher-order logic *}

    theory Set
    imports LOrder
    begin

    text {* A set in HOL is simply a predicate. *}

    subsection {* Basic syntax *}

    global

    typedecl 'a set
    arities set :: (type) type

    consts
      "{}"          :: "'a set"                             ("{}")
      UNIV          :: "'a set"
      insert        :: "'a => 'a set => 'a set"
      Collect       :: "('a => bool) => 'a set"              -- "comprehension"
      Int           :: "'a set => 'a set => 'a set"          (infixl 70)
      Un            :: "'a set => 'a set => 'a set"          (infixl 65)
      UNION         :: "'a set => ('a => 'b set) => 'b set"  -- "general union"
      INTER         :: "'a set => ('a => 'b set) => 'b set"  -- "general intersection"
      Union         :: "'a set set => 'a set"                -- "union of a set"
      Inter         :: "'a set set => 'a set"                -- "intersection of a set"
      Pow           :: "'a set => 'a set set"                -- "powerset"
      Ball          :: "'a set => ('a => bool) => bool"      -- "bounded universal quantifiers"
      Bex           :: "'a set => ('a => bool) => bool"      -- "bounded existential quantifiers"
      image         :: "('a => 'b) => 'a set => 'b set"      (infixr "`" 90)

    syntax
      "op :"        :: "'a => 'a set => bool"                ("op :")
    consts
      "op :"        :: "'a => 'a set => bool"                ("(_/ : _)" [50, 51] 50)  -- "membership"

    local

    instance set :: (type) "{ord, minus}" ..

    subsection {* Additional concrete syntax *}

    syntax
      range         :: "('a => 'b) => 'b set"             -- "of function"

      "op ~:"       :: "'a => 'a set => bool"                 ("op ~:")  -- "non-membership"
      "op ~:"       :: "'a => 'a set => bool"                 ("(_/ ~: _)" [50, 51] 50)

      "@Finset"     :: "args => 'a set"                       ("{(_)}")
      "@Coll"       :: "pttrn => bool => 'a set"              ("(1{_./ _})")
      "@SetCompr"   :: "'a => idts => bool => 'a set"         ("(1{_ |/_./ _})")
      "@Collect"    :: "idt => 'a set => bool => 'a set"      ("(1{_ :/ _./ _})")
      "@INTER1"     :: "pttrns => 'b set => 'b set"           ("(3INT _./ _)" 10)
      "@UNION1"     :: "pttrns => 'b set => 'b set"           ("(3UN _./ _)" 10)
      "@INTER"      :: "pttrn => 'a set => 'b set => 'b set"  ("(3INT _:_./ _)" 10)
      "@UNION"      :: "pttrn => 'a set => 'b set => 'b set"  ("(3UN _:_./ _)" 10)

      "_Ball"       :: "pttrn => 'a set => bool => bool"      ("(3ALL _:_./ _)" [0, 0, 10] 10)
      "_Bex"        :: "pttrn => 'a set => bool => bool"      ("(3EX _:_./ _)" [0, 0, 10] 10)

    syntax (HOL)
      "_Ball"       :: "pttrn => 'a set => bool => bool"      ("(3! _:_./ _)" [0, 0, 10] 10)
      "_Bex"        :: "pttrn => 'a set => bool => bool"      ("(3? _:_./ _)" [0, 0, 10] 10)

    translations
      "range f"     == "f`UNIV"
      "x ~: y"      == "~ (x : y)"
      "{x, xs}"     == "insert x {xs}"
      "{x}"         == "insert x {}"
      "{x. P}"      == "Collect (%x. P)"
      "{x:A. P}"    => "{x. x:A & P}"
      "UN x y. B"   == "UN x. UN y. B"
      "UN x. B"     == "UNION UNIV (%x. B)"
      "UN x. B"     == "UN x:UNIV. B"
      "INT x y. B"  == "INT x. INT y. B"
      "INT x. B"    == "INTER UNIV (%x. B)"
      "INT x. B"    == "INT x:UNIV. B"
      "UN x:A. B"   == "UNION A (%x. B)"
      "INT x:A. B"  == "INTER A (%x. B)"
      "ALL x:A. P"  == "Ball A (%x. P)"
      "EX x:A. P"   == "Bex A (%x. P)"

    syntax (output)
      "_setle"      :: "'a set => 'a set => bool"             ("op <=")
      "_setle"      :: "'a set => 'a set => bool"             ("(_/ <= _)" [50, 51] 50)
      "_setless"    :: "'a set => 'a set => bool"             ("op <")
      "_setless"    :: "'a set => 'a set => bool"             ("(_/ < _)" [50, 51] 50)

    syntax (xsymbols)
      "_setle"      :: "'a set => 'a set => bool"             ("op ⊆")
      "_setle"      :: "'a set => 'a set => bool"             ("(_/ ⊆ _)" [50, 51] 50)
      "_setless"    :: "'a set => 'a set => bool"             ("op ⊂")
      "_setless"    :: "'a set => 'a set => bool"             ("(_/ ⊂ _)" [50, 51] 50)
      "op Int"      :: "'a set => 'a set => 'a set"           (infixl "∩" 70)
      "op Un"       :: "'a set => 'a set => 'a set"           (infixl "∪" 65)
      "op :"        :: "'a => 'a set => bool"                 ("op ∈")
      "op :"        :: "'a => 'a set => bool"                 ("(_/ ∈ _)" [50, 51] 50)
      "op ~:"       :: "'a => 'a set => bool"                 ("op ∉")
      "op ~:"       :: "'a => 'a set => bool"                 ("(_/ ∉ _)" [50, 51] 50)
      Union         :: "'a set set => 'a set"                 ("\<Union>_" [90] 90)
      Inter         :: "'a set set => 'a set"                 ("\<Inter>_" [90] 90)
      "_Ball"       :: "pttrn => 'a set => bool => bool"      ("(3∀_∈_./ _)" [0, 0, 10] 10)
      "_Bex"        :: "pttrn => 'a set => bool => bool"      ("(3∃_∈_./ _)" [0, 0, 10] 10)

    syntax (HTML output)
      "_setle"      :: "'a set => 'a set => bool"             ("op ⊆")
      "_setle"      :: "'a set => 'a set => bool"             ("(_/ ⊆ _)" [50, 51] 50)
      "_setless"    :: "'a set => 'a set => bool"             ("op ⊂")
      "_setless"    :: "'a set => 'a set => bool"             ("(_/ ⊂ _)" [50, 51] 50)
      "op Int"      :: "'a set => 'a set => 'a set"           (infixl "∩" 70)
      "op Un"       :: "'a set => 'a set => 'a set"           (infixl "∪" 65)
      "op :"        :: "'a => 'a set => bool"                 ("op ∈")
      "op :"        :: "'a => 'a set => bool"                 ("(_/ ∈ _)" [50, 51] 50)
      "op ~:"       :: "'a => 'a set => bool"                 ("op ∉")
      "op ~:"       :: "'a => 'a set => bool"                 ("(_/ ∉ _)" [50, 51] 50)
      "_Ball"       :: "pttrn => 'a set => bool => bool"      ("(3∀_∈_./ _)" [0, 0, 10] 10)
      "_Bex"        :: "pttrn => 'a set => bool => bool"      ("(3∃_∈_./ _)" [0, 0, 10] 10)

    syntax (xsymbols)
      "@Collect"    :: "idt => 'a set => bool => 'a set"      ("(1{_ ∈/ _./ _})")
      "@UNION1"     :: "pttrns => 'b set => 'b set"           ("(3\<Union>_./ _)" 10)
      "@INTER1"     :: "pttrns => 'b set => 'b set"           ("(3\<Inter>_./ _)" 10)
      "@UNION"      :: "pttrn => 'a set => 'b set => 'b set"  ("(3\<Union>_∈_./ _)" 10)
      "@INTER"      :: "pttrn => 'a set => 'b set => 'b set"  ("(3\<Inter>_∈_./ _)" 10)
    (*
    syntax (xsymbols)
      "@UNION1"     :: "pttrns => 'b set => 'b set"           ("(3\<Union>(00_)/ _)" 10)
      "@INTER1"     :: "pttrns => 'b set => 'b set"           ("(3\<Inter>(00_)/ _)" 10)
      "@UNION"      :: "pttrn => 'a set => 'b set => 'b set"  ("(3\<Union>(00_∈_)/ _)" 10)
      "@INTER"      :: "pttrn => 'a set => 'b set => 'b set"  ("(3\<Inter>(00_∈_)/ _)" 10)
    *)
    syntax (latex output)
      "@UNION1"     :: "pttrns => 'b set => 'b set"           ("(3\<Union>(00_)/ _)" 10)
      "@INTER1"     :: "pttrns => 'b set => 'b set"           ("(3\<Inter>(00_)/ _)" 10)
      "@UNION"      :: "pttrn => 'a set => 'b set => 'b set"  ("(3\<Union>(00_∈_)/ _)" 10)
      "@INTER"      :: "pttrn => 'a set => 'b set => 'b set"  ("(3\<Inter>(00_∈_)/ _)" 10)

    text{* Note the difference between ordinary xsymbol syntax of indexed
    unions and intersections (e.g.\ @{text"\<Union>a1∈A1. B"})
    and their \LaTeX\ rendition: @{term"\<Union>a1∈A1. B"}. The
    former does not make the index expression a subscript of the
    union/intersection symbol because this leads to problems with nested
    subscripts in Proof General.  *}

    translations
      "op ⊆" => "op <= :: _ set => _ set => bool"
      "op ⊂" => "op <  :: _ set => _ set => bool"

    typed_print_translation {*
      let
        fun le_tr' _ (Type ("fun", (Type ("set", _) :: _))) ts =
              list_comb (Syntax.const "_setle", ts)
          | le_tr' _ _ _ = raise Match;

        fun less_tr' _ (Type ("fun", (Type ("set", _) :: _))) ts =
              list_comb (Syntax.const "_setless", ts)
          | less_tr' _ _ _ = raise Match;
      in [("op <=", le_tr'), ("op <", less_tr')] end
    *}

    subsubsection "Bounded quantifiers"

    syntax
      "_setlessAll" :: "[idt, 'a, bool] => bool"  ("(3ALL _<_./ _)"  [0, 0, 10] 10)
      "_setlessEx"  :: "[idt, 'a, bool] => bool"  ("(3EX _<_./ _)"  [0, 0, 10] 10)
      "_setleAll"   :: "[idt, 'a, bool] => bool"  ("(3ALL _<=_./ _)" [0, 0, 10] 10)
      "_setleEx"    :: "[idt, 'a, bool] => bool"  ("(3EX _<=_./ _)" [0, 0, 10] 10)

    syntax (xsymbols)
      "_setlessAll" :: "[idt, 'a, bool] => bool"   ("(3∀_⊂_./ _)"  [0, 0, 10] 10)
      "_setlessEx"  :: "[idt, 'a, bool] => bool"   ("(3∃_⊂_./ _)"  [0, 0, 10] 10)
      "_setleAll"   :: "[idt, 'a, bool] => bool"   ("(3∀_⊆_./ _)" [0, 0, 10] 10)
      "_setleEx"    :: "[idt, 'a, bool] => bool"   ("(3∃_⊆_./ _)" [0, 0, 10] 10)

    syntax (HOL)
      "_setlessAll" :: "[idt, 'a, bool] => bool"   ("(3! _<_./ _)"  [0, 0, 10] 10)
      "_setlessEx"  :: "[idt, 'a, bool] => bool"   ("(3? _<_./ _)"  [0, 0, 10] 10)
      "_setleAll"   :: "[idt, 'a, bool] => bool"   ("(3! _<=_./ _)" [0, 0, 10] 10)
      "_setleEx"    :: "[idt, 'a, bool] => bool"   ("(3? _<=_./ _)" [0, 0, 10] 10)

    syntax (HTML output)
      "_setlessAll" :: "[idt, 'a, bool] => bool"   ("(3∀_⊂_./ _)"  [0, 0, 10] 10)
      "_setlessEx"  :: "[idt, 'a, bool] => bool"   ("(3∃_⊂_./ _)"  [0, 0, 10] 10)
      "_setleAll"   :: "[idt, 'a, bool] => bool"   ("(3∀_⊆_./ _)" [0, 0, 10] 10)
      "_setleEx"    :: "[idt, 'a, bool] => bool"   ("(3∃_⊆_./ _)" [0, 0, 10] 10)

    translations
     "∀A⊂B. P"   =>  "ALL A. A ⊂ B --> P"
     "∃A⊂B. P"    =>  "EX A. A ⊂ B & P"
     "∀A⊆B. P"  =>  "ALL A. A ⊆ B --> P"
     "∃A⊆B. P"   =>  "EX A. A ⊆ B & P"

    print_translation {*
    let
      fun
        all_tr' [Const ("_bound",_) $ Free (v,Type(T,_)),
                 Const("op -->",_) $ (Const ("op <",_) $ (Const ("_bound",_) $ Free (v',_)) $ n ) $ P] =
      (if v=v' andalso T="set"
       then Syntax.const "_setlessAll" $ Syntax.mark_bound v' $ n $ P
       else raise Match)

      | all_tr' [Const ("_bound",_) $ Free (v,Type(T,_)),
                 Const("op -->",_) $ (Const ("op <=",_) $ (Const ("_bound",_) $ Free (v',_)) $ n ) $ P] =
      (if v=v' andalso T="set"
       then Syntax.const "_setleAll" $ Syntax.mark_bound v' $ n $ P
       else raise Match);

      fun
        ex_tr' [Const ("_bound",_) $ Free (v,Type(T,_)),
                Const("op &",_) $ (Const ("op <",_) $ (Const ("_bound",_) $ Free (v',_)) $ n ) $ P] =
      (if v=v' andalso T="set"
       then Syntax.const "_setlessEx" $ Syntax.mark_bound v' $ n $ P
       else raise Match)

      | ex_tr' [Const ("_bound",_) $ Free (v,Type(T,_)),
                Const("op &",_) $ (Const ("op <=",_) $ (Const ("_bound",_) $ Free (v',_)) $ n ) $ P] =
      (if v=v' andalso T="set"
       then Syntax.const "_setleEx" $ Syntax.mark_bound v' $ n $ P
       else raise Match)
    in
    [("ALL ", all_tr'), ("EX ", ex_tr')]
    end
    *}

    text {*
      \medskip Translate between @{text "{e | x1...xn. P}"} and @{text
      "{u. EX x1..xn. u = e & P}"}; @{text "{y. EX x1..xn. y = e & P}"} is
      only translated if @{text "[0..n] subset bvs(e)"}.
    *}

    parse_translation {*
      let
        val ex_tr = snd (mk_binder_tr ("EX ", "Ex"));

        fun nvars (Const ("_idts", _) $ _ $ idts) = nvars idts + 1
          | nvars _ = 1;

        fun setcompr_tr [e, idts, b] =
          let
            val eq = Syntax.const "op =" $ Bound (nvars idts) $ e;
            val P = Syntax.const "op &" $ eq $ b;
            val exP = ex_tr [idts, P];
          in Syntax.const "Collect" $ Abs ("", dummyT, exP) end;

      in [("@SetCompr", setcompr_tr)] end;
    *}

    (* To avoid eta-contraction of body: *)
    print_translation {*
    let
      fun btr' syn [A,Abs abs] =
        let val (x,t) = atomic_abs_tr' abs
        in Syntax.const syn $ x $ A $ t end
    in
    [("Ball", btr' "_Ball"),("Bex", btr' "_Bex"),
     ("UNION", btr' "@UNION"),("INTER", btr' "@INTER")]
    end
    *}

    print_translation {*
    let
      val ex_tr' = snd (mk_binder_tr' ("Ex", "DUMMY"));

      fun setcompr_tr' [Abs (abs as (_, _, P))] =
        let
          fun check (Const ("Ex", _) $ Abs (_, _, P), n) = check (P, n + 1)
            | check (Const ("op &", _) $ (Const ("op =", _) $ Bound m $ e) $ P, n) =
                n > 0 andalso m = n andalso not (loose_bvar1 (P, n)) andalso
                ((0 upto (n - 1)) subset add_loose_bnos (e, 0, []))
            | check _ = false

            fun tr' (_ $ abs) =
              let val _ $ idts $ (_ $ (_ $ _ $ e) $ Q) = ex_tr' [abs]
              in Syntax.const "@SetCompr" $ e $ idts $ Q end;
        in if check (P, 0) then tr' P
           else let val (x as _ $ Free(xN,_), t) = atomic_abs_tr' abs
                    val M = Syntax.const "@Coll" $ x $ t
                in case t of
                     Const("op &",_)
                       $ (Const("op :",_) $ (Const("_bound",_) $ Free(yN,_)) $ A)
                       $ P =>
                       if xN=yN then Syntax.const "@Collect" $ x $ A $ P else M
                   | _ => M
                end
        end;
      in [("Collect", setcompr_tr')] end;
    *}

    subsection {* Rules and definitions *}

    text {* Isomorphisms between predicates and sets. *}

    axioms
      mem_Collect_eq: "(a : {x. P(x)}) = P(a)"
      Collect_mem_eq: "{x. x:A} = A"
    finalconsts
      Collect
      "op :"

    defs
      Ball_def:     "Ball A P       == ALL x. x:A --> P(x)"
      Bex_def:      "Bex A P        == EX x. x:A & P(x)"

    defs (overloaded)
      subset_def:   "A <= B         == ALL x:A. x:B"
      psubset_def:  "A < B          == (A::'a set) <= B & ~ A=B"
      Compl_def:    "- A            == {x. ~x:A}"
      set_diff_def: "A - B          == {x. x:A & ~x:B}"

    defs
      Un_def:       "A Un B         == {x. x:A | x:B}"
      Int_def:      "A Int B        == {x. x:A & x:B}"
      INTER_def:    "INTER A B      == {y. ALL x:A. y: B(x)}"
      UNION_def:    "UNION A B      == {y. EX x:A. y: B(x)}"
      Inter_def:    "Inter S        == (INT x:S. x)"
      Union_def:    "Union S        == (UN x:S. x)"
      Pow_def:      "Pow A          == {B. B <= A}"
      empty_def:    "{}             == {x. False}"
      UNIV_def:     "UNIV           == {x. True}"
      insert_def:   "insert a B     == {x. x=a} Un B"
      image_def:    "f`A            == {y. EX x:A. y = f(x)}"

    subsection {* Lemmas and proof tool setup *}

    subsubsection {* Relating predicates and sets *}

    declare mem_Collect_eq [iff]  Collect_mem_eq [simp]

    lemma CollectI: "P(a) ==> a : {x. P(x)}"
      by simp

    lemma CollectD: "a : {x. P(x)} ==> P(a)"
      by simp

    lemma Collect_cong: "(!!x. P x = Q x) ==> {x. P(x)} = {x. Q(x)}"
      by simp

    lemmas CollectE = CollectD [elim_format]

    subsubsection {* Bounded quantifiers *}

    lemma ballI [intro!]: "(!!x. x:A ==> P x) ==> ALL x:A. P x"
      by (simp add: Ball_def)

    lemmas strip = impI allI ballI

    lemma bspec [dest?]: "ALL x:A. P x ==> x:A ==> P x"
      by (simp add: Ball_def)

    lemma ballE [elim]: "ALL x:A. P x ==> (P x ==> Q) ==> (x ~: A ==> Q) ==> Q"
      by (unfold Ball_def) blast
    ML {* bind_thm("rev_ballE",permute_prems 1 1 (thm "ballE")) *}

    text {*
      \medskip This tactic takes assumptions @{prop "ALL x:A. P x"} and
      @{prop "a:A"}; creates assumption @{prop "P a"}.
    *}

    ML {*
      local val ballE = thm "ballE"
      in fun ball_tac i = etac ballE i THEN contr_tac (i + 1) end;
    *}

    text {*
      Gives better instantiation for bound:
    *}

    ML_setup {*
      claset_ref() := claset() addbefore ("bspec", datac (thm "bspec") 1);
    *}

    lemma bexI [intro]: "P x ==> x:A ==> EX x:A. P x"
      -- {* Normally the best argument order: @{prop "P x"} constrains the
        choice of @{prop "x:A"}. *}
      by (unfold Bex_def) blast

    lemma rev_bexI [intro?]: "x:A ==> P x ==> EX x:A. P x"
      -- {* The best argument order when there is only one @{prop "x:A"}. *}
      by (unfold Bex_def) blast

    lemma bexCI: "(ALL x:A. ~P x ==> P a) ==> a:A ==> EX x:A. P x"
      by (unfold Bex_def) blast

    lemma bexE [elim!]: "EX x:A. P x ==> (!!x. x:A ==> P x ==> Q) ==> Q"
      by (unfold Bex_def) blast

    lemma ball_triv [simp]: "(ALL x:A. P) = ((EX x. x:A) --> P)"
      -- {* Trival rewrite rule. *}
      by (simp add: Ball_def)

    lemma bex_triv [simp]: "(EX x:A. P) = ((EX x. x:A) & P)"
      -- {* Dual form for existentials. *}
      by (simp add: Bex_def)

    lemma bex_triv_one_point1 [simp]: "(EX x:A. x = a) = (a:A)"
      by blast

    lemma bex_triv_one_point2 [simp]: "(EX x:A. a = x) = (a:A)"
      by blast

    lemma bex_one_point1 [simp]: "(EX x:A. x = a & P x) = (a:A & P a)"
      by blast

    lemma bex_one_point2 [simp]: "(EX x:A. a = x & P x) = (a:A & P a)"
      by blast

    lemma ball_one_point1 [simp]: "(ALL x:A. x = a --> P x) = (a:A --> P a)"
      by blast

    lemma ball_one_point2 [simp]: "(ALL x:A. a = x --> P x) = (a:A --> P a)"
      by blast

    ML_setup {*
      local
        val Ball_def = thm "Ball_def";
        val Bex_def = thm "Bex_def";

        val simpset = Simplifier.clear_ss HOL_basic_ss;
        fun unfold_tac ss th =
          ALLGOALS (full_simp_tac (Simplifier.inherit_bounds ss simpset addsimps [th]));

        fun prove_bex_tac ss =
          unfold_tac ss Bex_def THEN Quantifier1.prove_one_point_ex_tac;
        val rearrange_bex = Quantifier1.rearrange_bex prove_bex_tac;

        fun prove_ball_tac ss =
          unfold_tac ss Ball_def THEN Quantifier1.prove_one_point_all_tac;
        val rearrange_ball = Quantifier1.rearrange_ball prove_ball_tac;
      in
        val defBEX_regroup = Simplifier.simproc (Theory.sign_of (the_context ()))
          "defined BEX" ["EX x:A. P x & Q x"] rearrange_bex;
        val defBALL_regroup = Simplifier.simproc (Theory.sign_of (the_context ()))
          "defined BALL" ["ALL x:A. P x --> Q x"] rearrange_ball;
      end;

      Addsimprocs [defBALL_regroup, defBEX_regroup];
    *}

    subsubsection {* Congruence rules *}

    lemma ball_cong:
      "A = B ==> (!!x. x:B ==> P x = Q x) ==>
        (ALL x:A. P x) = (ALL x:B. Q x)"
      by (simp add: Ball_def)

    lemma strong_ball_cong [cong]:
      "A = B ==> (!!x. x:B =simp=> P x = Q x) ==>
        (ALL x:A. P x) = (ALL x:B. Q x)"
      by (simp add: simp_implies_def Ball_def)

    lemma bex_cong:
      "A = B ==> (!!x. x:B ==> P x = Q x) ==>
        (EX x:A. P x) = (EX x:B. Q x)"
      by (simp add: Bex_def cong: conj_cong)

    lemma strong_bex_cong [cong]:
      "A = B ==> (!!x. x:B =simp=> P x = Q x) ==>
        (EX x:A. P x) = (EX x:B. Q x)"
      by (simp add: simp_implies_def Bex_def cong: conj_cong)

    subsubsection {* Subsets *}

    lemma subsetI [intro!]: "(!!x. x:A ==> x:B) ==> A ⊆ B"
      by (simp add: subset_def)

    text {*
      \medskip Map the type @{text "'a set => anything"} to just @{typ
      'a}; for overloading constants whose first argument has type @{typ
      "'a set"}.
    *}

    lemma subsetD [elim]: "A ⊆ B ==> c ∈ A ==> c ∈ B"
      -- {* Rule in Modus Ponens style. *}
      by (unfold subset_def) blast

    declare subsetD [intro?] -- FIXME

    lemma rev_subsetD: "c ∈ A ==> A ⊆ B ==> c ∈ B"
      -- {* The same, with reversed premises for use with @{text erule} --
          cf @{text rev_mp}. *}
      by (rule subsetD)

    declare rev_subsetD [intro?] -- FIXME

    text {*
      \medskip Converts @{prop "A ⊆ B"} to @{prop "x ∈ A ==> x ∈ B"}.
    *}

    ML {*
      local val rev_subsetD = thm "rev_subsetD"
      in fun impOfSubs th = th RSN (2, rev_subsetD) end;
    *}

    lemma subsetCE [elim]: "A ⊆  B ==> (c ∉ A ==> P) ==> (c ∈ B ==> P) ==> P"
      -- {* Classical elimination rule. *}
      by (unfold subset_def) blast

    text {*
      \medskip Takes assumptions @{prop "A ⊆ B"}; @{prop "c ∈ A"} and
      creates the assumption @{prop "c ∈ B"}.
    *}

    ML {*
      local val subsetCE = thm "subsetCE"
      in fun set_mp_tac i = etac subsetCE i THEN mp_tac i end;
    *}

    lemma contra_subsetD: "A ⊆ B ==> c ∉ B ==> c ∉ A"
      by blast

    lemma subset_refl: "A ⊆ A"
      by fast

    lemma subset_trans: "A ⊆ B ==> B ⊆ C ==> A ⊆ C"
      by blast

    subsubsection {* Equality *}

    lemma set_ext: assumes prem: "(!!x. (x:A) = (x:B))" shows "A = B"
      apply (rule prem [THEN ext, THEN arg_cong, THEN box_equals])
       apply (rule Collect_mem_eq)
      apply (rule Collect_mem_eq)
      done

    (* Due to Brian Huffman *)
    lemma expand_set_eq: "(A = B) = (ALL x. (x:A) = (x:B))"
    by(auto intro:set_ext)

    lemma subset_antisym [intro!]: "A ⊆ B ==> B ⊆ A ==> A = B"
      -- {* Anti-symmetry of the subset relation. *}
      by (iprover intro: set_ext subsetD)

    lemmas equalityI [intro!] = subset_antisym

    text {*
      \medskip Equality rules from ZF set theory -- are they appropriate
      here?
    *}

    lemma equalityD1: "A = B ==> A ⊆ B"
      by (simp add: subset_refl)

    lemma equalityD2: "A = B ==> B ⊆ A"
      by (simp add: subset_refl)

    text {*
      \medskip Be careful when adding this to the claset as @{text
      subset_empty} is in the simpset: @{prop "A = {}"} goes to @{prop "{}
      ⊆ A"} and @{prop "A ⊆ {}"} and then back to @{prop "A = {}"}!
    *}

    lemma equalityE: "A = B ==> (A ⊆ B ==> B ⊆ A ==> P) ==> P"
      by (simp add: subset_refl)

    lemma equalityCE [elim]:
        "A = B ==> (c ∈ A ==> c ∈ B ==> P) ==> (c ∉ A ==> c ∉ B ==> P) ==> P"
      by blast

    text {*
      \medskip Lemma for creating induction formulae -- for "pattern
      matching" on @{text p}.  To make the induction hypotheses usable,
      apply @{text spec} or @{text bspec} to put universal quantifiers over the free
      variables in @{text p}.
    *}

    lemma setup_induction: "p:A ==> (!!z. z:A ==> p = z --> R) ==> R"
      by simp

    lemma eqset_imp_iff: "A = B ==> (x : A) = (x : B)"
      by simp

    lemma eqelem_imp_iff: "x = y ==> (x : A) = (y : A)"
      by simp

    subsubsection {* The universal set -- UNIV *}

    lemma UNIV_I [simp]: "x : UNIV"
      by (simp add: UNIV_def)

    declare UNIV_I [intro]  -- {* unsafe makes it less likely to cause problems *}

    lemma UNIV_witness [intro?]: "EX x. x : UNIV"
      by simp

    lemma subset_UNIV: "A ⊆ UNIV"
      by (rule subsetI) (rule UNIV_I)

    text {*
      \medskip Eta-contracting these two rules (to remove @{text P})
      causes them to be ignored because of their interaction with
      congruence rules.
    *}

    lemma ball_UNIV [simp]: "Ball UNIV P = All P"
      by (simp add: Ball_def)

    lemma bex_UNIV [simp]: "Bex UNIV P = Ex P"
      by (simp add: Bex_def)

    subsubsection {* The empty set *}

    lemma empty_iff [simp]: "(c : {}) = False"
      by (simp add: empty_def)

    lemma emptyE [elim!]: "a : {} ==> P"
      by simp

    lemma empty_subsetI [iff]: "{} ⊆ A"
        -- {* One effect is to delete the ASSUMPTION @{prop "{} <= A"} *}
      by blast

    lemma equals0I: "(!!y. y ∈ A ==> False) ==> A = {}"
      by blast

    lemma equals0D: "A = {} ==> a ∉ A"
        -- {* Use for reasoning about disjointness: @{prop "A Int B = {}"} *}
      by blast

    lemma ball_empty [simp]: "Ball {} P = True"
      by (simp add: Ball_def)

    lemma bex_empty [simp]: "Bex {} P = False"
      by (simp add: Bex_def)

    lemma UNIV_not_empty [iff]: "UNIV ~= {}"
      by (blast elim: equalityE)

    subsubsection {* The Powerset operator -- Pow *}

    lemma Pow_iff [iff]: "(A ∈ Pow B) = (A ⊆ B)"
      by (simp add: Pow_def)

    lemma PowI: "A ⊆ B ==> A ∈ Pow B"
      by (simp add: Pow_def)

    lemma PowD: "A ∈ Pow B ==> A ⊆ B"
      by (simp add: Pow_def)

    lemma Pow_bottom: "{} ∈ Pow B"
      by simp

    lemma Pow_top: "A ∈ Pow A"
      by (simp add: subset_refl)

    subsubsection {* Set complement *}

    lemma Compl_iff [simp]: "(c ∈ -A) = (c ∉ A)"
      by (unfold Compl_def) blast

    lemma ComplI [intro!]: "(c ∈ A ==> False) ==> c ∈ -A"
      by (unfold Compl_def) blast

    text {*
      \medskip This form, with negated conclusion, works well with the
      Classical prover.  Negated assumptions behave like formulae on the
      right side of the notional turnstile ... *}

    lemma ComplD [dest!]: "c : -A ==> c~:A"
      by (unfold Compl_def) blast

    lemmas ComplE = ComplD [elim_format]

    subsubsection {* Binary union -- Un *}

    lemma Un_iff [simp]: "(c : A Un B) = (c:A | c:B)"
      by (unfold Un_def) blast

    lemma UnI1 [elim?]: "c:A ==> c : A Un B"
      by simp

    lemma UnI2 [elim?]: "c:B ==> c : A Un B"
      by simp

    text {*
      \medskip Classical introduction rule: no commitment to @{prop A} vs
      @{prop B}.
    *}

    lemma UnCI [intro!]: "(c~:B ==> c:A) ==> c : A Un B"
      by auto

    lemma UnE [elim!]: "c : A Un B ==> (c:A ==> P) ==> (c:B ==> P) ==> P"
      by (unfold Un_def) blast

    subsubsection {* Binary intersection -- Int *}

    lemma Int_iff [simp]: "(c : A Int B) = (c:A & c:B)"
      by (unfold Int_def) blast

    lemma IntI [intro!]: "c:A ==> c:B ==> c : A Int B"
      by simp

    lemma IntD1: "c : A Int B ==> c:A"
      by simp

    lemma IntD2: "c : A Int B ==> c:B"
      by simp

    lemma IntE [elim!]: "c : A Int B ==> (c:A ==> c:B ==> P) ==> P"
      by simp

    subsubsection {* Set difference *}

    lemma Diff_iff [simp]: "(c : A - B) = (c:A & c~:B)"
      by (unfold set_diff_def) blast

    lemma DiffI [intro!]: "c : A ==> c ~: B ==> c : A - B"
      by simp

    lemma DiffD1: "c : A - B ==> c : A"
      by simp

    lemma DiffD2: "c : A - B ==> c : B ==> P"
      by simp

    lemma DiffE [elim!]: "c : A - B ==> (c:A ==> c~:B ==> P) ==> P"
      by simp

    subsubsection {* Augmenting a set -- insert *}

    lemma insert_iff [simp]: "(a : insert b A) = (a = b | a:A)"
      by (unfold insert_def) blast

    lemma insertI1: "a : insert a B"
      by simp

    lemma insertI2: "a : B ==> a : insert b B"
      by simp

    lemma insertE [elim!]: "a : insert b A ==> (a = b ==> P) ==> (a:A ==> P) ==> P"
      by (unfold insert_def) blast

    lemma insertCI [intro!]: "(a~:B ==> a = b) ==> a: insert b B"
      -- {* Classical introduction rule. *}
      by auto

    lemma subset_insert_iff: "(A ⊆ insert x B) = (if x:A then A - {x} ⊆ B else A ⊆ B)"
      by auto

    subsubsection {* Singletons, using insert *}

    lemma singletonI [intro!]: "a : {a}"
        -- {* Redundant? But unlike @{text insertCI}, it proves the subgoal immediately! *}
      by (rule insertI1)

    lemma singletonD [dest!]: "b : {a} ==> b = a"
      by blast

    lemmas singletonE = singletonD [elim_format]

    lemma singleton_iff: "(b : {a}) = (b = a)"
      by blast

    lemma singleton_inject [dest!]: "{a} = {b} ==> a = b"
      by blast

    lemma singleton_insert_inj_eq [iff]: "({b} = insert a A) = (a = b & A ⊆ {b})"
      by blast

    lemma singleton_insert_inj_eq' [iff]: "(insert a A = {b}) = (a = b & A ⊆ {b})"
      by blast

    lemma subset_singletonD: "A ⊆ {x} ==> A = {} | A = {x}"
      by fast

    lemma singleton_conv [simp]: "{x. x = a} = {a}"
      by blast

    lemma singleton_conv2 [simp]: "{x. a = x} = {a}"
      by blast

    lemma diff_single_insert: "A - {x} ⊆ B ==> x ∈ A ==> A ⊆ insert x B"
      by blast

    subsubsection {* Unions of families *}

    text {*
      @{term [source] "UN x:A. B x"} is @{term "Union (B`A)"}.
    *}

    lemma UN_iff [simp]: "(b: (UN x:A. B x)) = (EX x:A. b: B x)"
      by (unfold UNION_def) blast

    lemma UN_I [intro]: "a:A ==> b: B a ==> b: (UN x:A. B x)"
      -- {* The order of the premises presupposes that @{term A} is rigid;
        @{term b} may be flexible. *}
      by auto

    lemma UN_E [elim!]: "b : (UN x:A. B x) ==> (!!x. x:A ==> b: B x ==> R) ==> R"
      by (unfold UNION_def) blast

    lemma UN_cong [cong]:
        "A = B ==> (!!x. x:B ==> C x = D x) ==> (UN x:A. C x) = (UN x:B. D x)"
      by (simp add: UNION_def)

    subsubsection {* Intersections of families *}

    text {* @{term [source] "INT x:A. B x"} is @{term "Inter (B`A)"}. *}

    lemma INT_iff [simp]: "(b: (INT x:A. B x)) = (ALL x:A. b: B x)"
      by (unfold INTER_def) blast

    lemma INT_I [intro!]: "(!!x. x:A ==> b: B x) ==> b : (INT x:A. B x)"
      by (unfold INTER_def) blast

    lemma INT_D [elim]: "b : (INT x:A. B x) ==> a:A ==> b: B a"
      by auto

    lemma INT_E [elim]: "b : (INT x:A. B x) ==> (b: B a ==> R) ==> (a~:A ==> R) ==> R"
      -- {* "Classical" elimination -- by the Excluded Middle on @{prop "a:A"}. *}
      by (unfold INTER_def) blast

    lemma INT_cong [cong]:
        "A = B ==> (!!x. x:B ==> C x = D x) ==> (INT x:A. C x) = (INT x:B. D x)"
      by (simp add: INTER_def)

    subsubsection {* Union *}

    lemma Union_iff [simp]: "(A : Union C) = (EX X:C. A:X)"
      by (unfold Union_def) blast

    lemma UnionI [intro]: "X:C ==> A:X ==> A : Union C"
      -- {* The order of the premises presupposes that @{term C} is rigid;
        @{term A} may be flexible. *}
      by auto

    lemma UnionE [elim!]: "A : Union C ==> (!!X. A:X ==> X:C ==> R) ==> R"
      by (unfold Union_def) blast

    subsubsection {* Inter *}

    lemma Inter_iff [simp]: "(A : Inter C) = (ALL X:C. A:X)"
      by (unfold Inter_def) blast

    lemma InterI [intro!]: "(!!X. X:C ==> A:X) ==> A : Inter C"
      by (simp add: Inter_def)

    text {*
      \medskip A ``destruct'' rule -- every @{term X} in @{term C}
      contains @{term A} as an element, but @{prop "A:X"} can hold when
      @{prop "X:C"} does not!  This rule is analogous to @{text spec}.
    *}

    lemma InterD [elim]: "A : Inter C ==> X:C ==> A:X"
      by auto

    lemma InterE [elim]: "A : Inter C ==> (X~:C ==> R) ==> (A:X ==> R) ==> R"
      -- {* ``Classical'' elimination rule -- does not require proving
        @{prop "X:C"}. *}
      by (unfold Inter_def) blast

    text {*
      \medskip Image of a set under a function.  Frequently @{term b} does
      not have the syntactic form of @{term "f x"}.
    *}

    lemma image_eqI [simp, intro]: "b = f x ==> x:A ==> b : f`A"
      by (unfold image_def) blast

    lemma imageI: "x : A ==> f x : f ` A"
      by (rule image_eqI) (rule refl)

    lemma rev_image_eqI: "x:A ==> b = f x ==> b : f`A"
      -- {* This version's more effective when we already have the
        required @{term x}. *}
      by (unfold image_def) blast

    lemma imageE [elim!]:
      "b : (%x. f x)`A ==> (!!x. b = f x ==> x:A ==> P) ==> P"
      -- {* The eta-expansion gives variable-name preservation. *}
      by (unfold image_def) blast

    lemma image_Un: "f`(A Un B) = f`A Un f`B"
      by blast

    lemma image_iff: "(z : f`A) = (EX x:A. z = f x)"
      by blast

    lemma image_subset_iff: "(f`A ⊆ B) = (∀x∈A. f x ∈ B)"
      -- {* This rewrite rule would confuse users if made default. *}
      by blast

    lemma subset_image_iff: "(B ⊆ f`A) = (EX AA. AA ⊆ A & B = f`AA)"
      apply safe
       prefer 2 apply fast
      apply (rule_tac x = "{a. a : A & f a : B}" in exI, fast)
      done

    lemma image_subsetI: "(!!x. x ∈ A ==> f x ∈ B) ==> f`A ⊆ B"
      -- {* Replaces the three steps @{text subsetI}, @{text imageE},
        @{text hypsubst}, but breaks too many existing proofs. *}
      by blast

    text {*
      \medskip Range of a function -- just a translation for image!
    *}

    lemma range_eqI: "b = f x ==> b ∈ range f"
      by simp

    lemma rangeI: "f x ∈ range f"
      by simp

    lemma rangeE [elim?]: "b ∈ range (λx. f x) ==> (!!x. b = f x ==> P) ==> P"
      by blast

    subsubsection {* Set reasoning tools *}

    text {*
      Rewrite rules for boolean case-splitting: faster than @{text
      "split_if [split]"}.
    *}

    lemma split_if_eq1: "((if Q then x else y) = b) = ((Q --> x = b) & (~ Q --> y = b))"
      by (rule split_if)

    lemma split_if_eq2: "(a = (if Q then x else y)) = ((Q --> a = x) & (~ Q --> a = y))"
      by (rule split_if)

    text {*
      Split ifs on either side of the membership relation.  Not for @{text
      "[simp]"} -- can cause goals to blow up!
    *}

    lemma split_if_mem1: "((if Q then x else y) : b) = ((Q --> x : b) & (~ Q --> y : b))"
      by (rule split_if)

    lemma split_if_mem2: "(a : (if Q then x else y)) = ((Q --> a : x) & (~ Q --> a : y))"
      by (rule split_if)

    lemmas split_ifs = if_bool_eq_conj split_if_eq1 split_if_eq2 split_if_mem1 split_if_mem2

    lemmas mem_simps =
      insert_iff empty_iff Un_iff Int_iff Compl_iff Diff_iff
      mem_Collect_eq UN_iff Union_iff INT_iff Inter_iff
      -- {* Each of these has ALREADY been added @{text "[simp]"} above. *}

    (*Would like to add these, but the existing code only searches for the
      outer-level constant, which in this case is just "op :"; we instead need
      to use term-nets to associate patterns with rules.  Also, if a rule fails to
      apply, then the formula should be kept.
      [("uminus", Compl_iff RS iffD1), ("op -", [Diff_iff RS iffD1]),
       ("op Int", [IntD1,IntD2]),
       ("Collect", [CollectD]), ("Inter", [InterD]), ("INTER", [INT_D])]
     *)

    ML_setup {*
      val mksimps_pairs = [("Ball", [thm "bspec"])] @ mksimps_pairs;
      simpset_ref() := simpset() setmksimps (mksimps mksimps_pairs);
    *}

    declare subset_UNIV [simp] subset_refl [simp]

    subsubsection {* The ``proper subset'' relation *}

    lemma psubsetI [intro!]: "A ⊆ B ==> A ≠ B ==> A ⊂ B"
      by (unfold psubset_def) blast

    lemma psubsetE [elim!]:
        "[|A ⊂ B;  [|A ⊆ B; ~ (B⊆A)|] ==> R|] ==> R"
      by (unfold psubset_def) blast

    lemma psubset_insert_iff:
      "(A ⊂ insert x B) = (if x ∈ B then A ⊂ B else if x ∈ A then A - {x} ⊂ B else A ⊆ B)"
      by (auto simp add: psubset_def subset_insert_iff)

    lemma psubset_eq: "(A ⊂ B) = (A ⊆ B & A ≠ B)"
      by (simp only: psubset_def)

    lemma psubset_imp_subset: "A ⊂ B ==> A ⊆ B"
      by (simp add: psubset_eq)

    lemma psubset_trans: "[| A ⊂ B; B ⊂ C |] ==> A ⊂ C"
    apply (unfold psubset_def)
    apply (auto dest: subset_antisym)
    done

    lemma psubsetD: "[| A ⊂ B; c ∈ A |] ==> c ∈ B"
    apply (unfold psubset_def)
    apply (auto dest: subsetD)
    done

    lemma psubset_subset_trans: "A ⊂ B ==> B ⊆ C ==> A ⊂ C"
      by (auto simp add: psubset_eq)

    lemma subset_psubset_trans: "A ⊆ B ==> B ⊂ C ==> A ⊂ C"
      by (auto simp add: psubset_eq)

    lemma psubset_imp_ex_mem: "A ⊂ B ==> ∃b. b ∈ (B - A)"
      by (unfold psubset_def) blast

    lemma atomize_ball:
        "(!!x. x ∈ A ==> P x) == Trueprop (∀x∈A. P x)"
      by (simp only: Ball_def atomize_all atomize_imp)

    declare atomize_ball [symmetric, rulify]

    subsection {* Further set-theory lemmas *}

    subsubsection {* Derived rules involving subsets. *}

    text {* @{text insert}. *}

    lemma subset_insertI: "B ⊆ insert a B"
      apply (rule subsetI)
      apply (erule insertI2)
      done

    lemma subset_insertI2: "A ⊆ B ==> A ⊆ insert b B"
    by blast

    lemma subset_insert: "x ∉ A ==> (A ⊆ insert x B) = (A ⊆ B)"
      by blast

    text {* \medskip Big Union -- least upper bound of a set. *}

    lemma Union_upper: "B ∈ A ==> B ⊆ Union A"
      by (iprover intro: subsetI UnionI)

    lemma Union_least: "(!!X. X ∈ A ==> X ⊆ C) ==> Union A ⊆ C"
      by (iprover intro: subsetI elim: UnionE dest: subsetD)

    text {* \medskip General union. *}

    lemma UN_upper: "a ∈ A ==> B a ⊆ (\<Union>x∈A. B x)"
      by blast

    lemma UN_least: "(!!x. x ∈ A ==> B x ⊆ C) ==> (\<Union>x∈A. B x) ⊆ C"
      by (iprover intro: subsetI elim: UN_E dest: subsetD)

    text {* \medskip Big Intersection -- greatest lower bound of a set. *}

    lemma Inter_lower: "B ∈ A ==> Inter A ⊆ B"
      by blast

    lemma Inter_subset:
      "[| !!X. X ∈ A ==> X ⊆ B; A ~= {} |] ==> \<Inter>A ⊆ B"
      by blast

    lemma Inter_greatest: "(!!X. X ∈ A ==> C ⊆ X) ==> C ⊆ Inter A"
      by (iprover intro: InterI subsetI dest: subsetD)

    lemma INT_lower: "a ∈ A ==> (\<Inter>x∈A. B x) ⊆ B a"
      by blast

    lemma INT_greatest: "(!!x. x ∈ A ==> C ⊆ B x) ==> C ⊆ (\<Inter>x∈A. B x)"
      by (iprover intro: INT_I subsetI dest: subsetD)

    text {* \medskip Finite Union -- the least upper bound of two sets. *}

    lemma Un_upper1: "A ⊆ A ∪ B"
      by blast

    lemma Un_upper2: "B ⊆ A ∪ B"
      by blast

    lemma Un_least: "A ⊆ C ==> B ⊆ C ==> A ∪ B ⊆ C"
      by blast

    text {* \medskip Finite Intersection -- the greatest lower bound of two sets. *}

    lemma Int_lower1: "A ∩ B ⊆ A"
      by blast

    lemma Int_lower2: "A ∩ B ⊆ B"
      by blast

    lemma Int_greatest: "C ⊆ A ==> C ⊆ B ==> C ⊆ A ∩ B"
      by blast

    text {* \medskip Set difference. *}

    lemma Diff_subset: "A - B ⊆ A"
      by blast

    lemma Diff_subset_conv: "(A - B ⊆ C) = (A ⊆ B ∪ C)"
    by blast

    text {* \medskip Monotonicity. *}

    lemma mono_Un: "mono f ==> f A ∪ f B ⊆ f (A ∪ B)"
      by (auto simp add: mono_def)

    lemma mono_Int: "mono f ==> f (A ∩ B) ⊆ f A ∩ f B"
      by (auto simp add: mono_def)

    subsubsection {* Equalities involving union, intersection, inclusion, etc. *}

    text {* @{text "{}"}. *}

    lemma Collect_const [simp]: "{s. P} = (if P then UNIV else {})"
      -- {* supersedes @{text "Collect_False_empty"} *}
      by auto

    lemma subset_empty [simp]: "(A ⊆ {}) = (A = {})"
      by blast

    lemma not_psubset_empty [iff]: "¬ (A < {})"
      by (unfold psubset_def) blast

    lemma Collect_empty_eq [simp]: "(Collect P = {}) = (∀x. ¬ P x)"
      by auto

    lemma Collect_neg_eq: "{x. ¬ P x} = - {x. P x}"
      by blast

    lemma Collect_disj_eq: "{x. P x | Q x} = {x. P x} ∪ {x. Q x}"
      by blast

    lemma Collect_imp_eq: "{x. P x --> Q x} = -{x. P x} ∪ {x. Q x}"
      by blast

    lemma Collect_conj_eq: "{x. P x & Q x} = {x. P x} ∩ {x. Q x}"
      by blast

    lemma Collect_all_eq: "{x. ∀y. P x y} = (\<Inter>y. {x. P x y})"
      by blast

    lemma Collect_ball_eq: "{x. ∀y∈A. P x y} = (\<Inter>y∈A. {x. P x y})"
      by blast

    lemma Collect_ex_eq: "{x. ∃y. P x y} = (\<Union>y. {x. P x y})"
      by blast

    lemma Collect_bex_eq: "{x. ∃y∈A. P x y} = (\<Union>y∈A. {x. P x y})"
      by blast

    text {* \medskip @{text insert}. *}

    lemma insert_is_Un: "insert a A = {a} Un A"
      -- {* NOT SUITABLE FOR REWRITING since @{text "{a} == insert a {}"} *}
      by blast

    lemma insert_not_empty [simp]: "insert a A ≠ {}"
      by blast

    lemmas empty_not_insert = insert_not_empty [symmetric, standard]
    declare empty_not_insert [simp]

    lemma insert_absorb: "a ∈ A ==> insert a A = A"
      -- {* @{text "[simp]"} causes recursive calls when there are nested inserts *}
      -- {* with \emph{quadratic} running time *}
      by blast

    lemma insert_absorb2 [simp]: "insert x (insert x A) = insert x A"
      by blast

    lemma insert_commute: "insert x (insert y A) = insert y (insert x A)"
      by blast

    lemma insert_subset [simp]: "(insert x A ⊆ B) = (x ∈ B & A ⊆ B)"
      by blast

    lemma mk_disjoint_insert: "a ∈ A ==> ∃B. A = insert a B & a ∉ B"
      -- {* use new @{text B} rather than @{text "A - {a}"} to avoid infinite unfolding *}
      apply (rule_tac x = "A - {a}" in exI, blast)
      done

    lemma insert_Collect: "insert a (Collect P) = {u. u ≠ a --> P u}"
      by auto

    lemma UN_insert_distrib: "u ∈ A ==> (\<Union>x∈A. insert a (B x)) = insert a (\<Union>x∈A. B x)"
      by blast

    lemma insert_inter_insert[simp]: "insert a A ∩ insert a B = insert a (A ∩ B)"
      by blast

    lemma insert_disjoint[simp]:
     "(insert a A ∩ B = {}) = (a ∉ B ∧ A ∩ B = {})"
     "({} = insert a A ∩ B) = (a ∉ B ∧ {} = A ∩ B)"
      by auto

    lemma disjoint_insert[simp]:
     "(B ∩ insert a A = {}) = (a ∉ B ∧ B ∩ A = {})"
     "({} = A ∩ insert b B) = (b ∉ A ∧ {} = A ∩ B)"
      by auto

    text {* \medskip @{text image}. *}

    lemma image_empty [simp]: "f`{} = {}"
      by blast

    lemma image_insert [simp]: "f ` insert a B = insert (f a) (f`B)"
      by blast

    lemma image_constant: "x ∈ A ==> (λx. c) ` A = {c}"
      by auto

    lemma image_image: "f ` (g ` A) = (λx. f (g x)) ` A"
      by blast

    lemma insert_image [simp]: "x ∈ A ==> insert (f x) (f`A) = f`A"
      by blast

    lemma image_is_empty [iff]: "(f`A = {}) = (A = {})"
      by blast

    lemma image_Collect: "f ` {x. P x} = {f x | x. P x}"
      -- {* NOT suitable as a default simprule: the RHS isn't simpler than the LHS,
          with its implicit quantifier and conjunction.  Also image enjoys better
          equational properties than does the RHS. *}
      by blast

    lemma if_image_distrib [simp]:
      "(λx. if P x then f x else g x) ` S
        = (f ` (S ∩ {x. P x})) ∪ (g ` (S ∩ {x. ¬ P x}))"
      by (auto simp add: image_def)

    lemma image_cong: "M = N ==> (!!x. x ∈ N ==> f x = g x) ==> f`M = g`N"
      by (simp add: image_def)

    text {* \medskip @{text range}. *}

    lemma full_SetCompr_eq: "{u. ∃x. u = f x} = range f"
      by auto

    lemma range_composition [simp]: "range (λx. f (g x)) = f`range g"
    by (subst image_image, simp)

    text {* \medskip @{text Int} *}

    lemma Int_absorb [simp]: "A ∩ A = A"
      by blast

    lemma Int_left_absorb: "A ∩ (A ∩ B) = A ∩ B"
      by blast

    lemma Int_commute: "A ∩ B = B ∩ A"
      by blast

    lemma Int_left_commute: "A ∩ (B ∩ C) = B ∩ (A ∩ C)"
      by blast

    lemma Int_assoc: "(A ∩ B) ∩ C = A ∩ (B ∩ C)"
      by blast

    lemmas Int_ac = Int_assoc Int_left_absorb Int_commute Int_left_commute
      -- {* Intersection is an AC-operator *}

    lemma Int_absorb1: "B ⊆ A ==> A ∩ B = B"
      by blast

    lemma Int_absorb2: "A ⊆ B ==> A ∩ B = A"
      by blast

    lemma Int_empty_left [simp]: "{} ∩ B = {}"
      by blast

    lemma Int_empty_right [simp]: "A ∩ {} = {}"
      by blast

    lemma disjoint_eq_subset_Compl: "(A ∩ B = {}) = (A ⊆ -B)"
      by blast

    lemma disjoint_iff_not_equal: "(A ∩ B = {}) = (∀x∈A. ∀y∈B. x ≠ y)"
      by blast

    lemma Int_UNIV_left [simp]: "UNIV ∩ B = B"
      by blast

    lemma Int_UNIV_right [simp]: "A ∩ UNIV = A"
      by blast

    lemma Int_eq_Inter: "A ∩ B = \<Inter>{A, B}"
      by blast

    lemma Int_Un_distrib: "A ∩ (B ∪ C) = (A ∩ B) ∪ (A ∩ C)"
      by blast

    lemma Int_Un_distrib2: "(B ∪ C) ∩ A = (B ∩ A) ∪ (C ∩ A)"
      by blast

    lemma Int_UNIV [simp]: "(A ∩ B = UNIV) = (A = UNIV & B = UNIV)"
      by blast

    lemma Int_subset_iff [simp]: "(C ⊆ A ∩ B) = (C ⊆ A & C ⊆ B)"
      by blast

    lemma Int_Collect: "(x ∈ A ∩ {x. P x}) = (x ∈ A & P x)"
      by blast

    text {* \medskip @{text Un}. *}

    lemma Un_absorb [simp]: "A ∪ A = A"
      by blast

    lemma Un_left_absorb: "A ∪ (A ∪ B) = A ∪ B"
      by blast

    lemma Un_commute: "A ∪ B = B ∪ A"
      by blast

    lemma Un_left_commute: "A ∪ (B ∪ C) = B ∪ (A ∪ C)"
      by blast

    lemma Un_assoc: "(A ∪ B) ∪ C = A ∪ (B ∪ C)"
      by blast

    lemmas Un_ac = Un_assoc Un_left_absorb Un_commute Un_left_commute
      -- {* Union is an AC-operator *}

    lemma Un_absorb1: "A ⊆ B ==> A ∪ B = B"
      by blast

    lemma Un_absorb2: "B ⊆ A ==> A ∪ B = A"
      by blast

    lemma Un_empty_left [simp]: "{} ∪ B = B"
      by blast

    lemma Un_empty_right [simp]: "A ∪ {} = A"
      by blast

    lemma Un_UNIV_left [simp]: "UNIV ∪ B = UNIV"
      by blast

    lemma Un_UNIV_right [simp]: "A ∪ UNIV = UNIV"
      by blast

    lemma Un_eq_Union: "A ∪ B = \<Union>{A, B}"
      by blast

    lemma Un_insert_left [simp]: "(insert a B) ∪ C = insert a (B ∪ C)"
      by blast

    lemma Un_insert_right [simp]: "A ∪ (insert a B) = insert a (A ∪ B)"
      by blast

    lemma Int_insert_left:
        "(insert a B) Int C = (if a ∈ C then insert a (B ∩ C) else B ∩ C)"
      by auto

    lemma Int_insert_right:
        "A ∩ (insert a B) = (if a ∈ A then insert a (A ∩ B) else A ∩ B)"
      by auto

    lemma Un_Int_distrib: "A ∪ (B ∩ C) = (A ∪ B) ∩ (A ∪ C)"
      by blast

    lemma Un_Int_distrib2: "(B ∩ C) ∪ A = (B ∪ A) ∩ (C ∪ A)"
      by blast

    lemma Un_Int_crazy:
        "(A ∩ B) ∪ (B ∩ C) ∪ (C ∩ A) = (A ∪ B) ∩ (B ∪ C) ∩ (C ∪ A)"
      by blast

    lemma subset_Un_eq: "(A ⊆ B) = (A ∪ B = B)"
      by blast

    lemma Un_empty [iff]: "(A ∪ B = {}) = (A = {} & B = {})"
      by blast

    lemma Un_subset_iff [simp]: "(A ∪ B ⊆ C) = (A ⊆ C & B ⊆ C)"
      by blast

    lemma Un_Diff_Int: "(A - B) ∪ (A ∩ B) = A"
      by blast

    text {* \medskip Set complement *}

    lemma Compl_disjoint [simp]: "A ∩ -A = {}"
      by blast

    lemma Compl_disjoint2 [simp]: "-A ∩ A = {}"
      by blast

    lemma Compl_partition: "A ∪ -A = UNIV"
      by blast

    lemma Compl_partition2: "-A ∪ A = UNIV"
      by blast

    lemma double_complement [simp]: "- (-A) = (A::'a set)"
      by blast

    lemma Compl_Un [simp]: "-(A ∪ B) = (-A) ∩ (-B)"
      by blast

    lemma Compl_Int [simp]: "-(A ∩ B) = (-A) ∪ (-B)"
      by blast

    lemma Compl_UN [simp]: "-(\<Union>x∈A. B x) = (\<Inter>x∈A. -B x)"
      by blast

    lemma Compl_INT [simp]: "-(\<Inter>x∈A. B x) = (\<Union>x∈A. -B x)"
      by blast

    lemma subset_Compl_self_eq: "(A ⊆ -A) = (A = {})"
      by blast

    lemma Un_Int_assoc_eq: "((A ∩ B) ∪ C = A ∩ (B ∪ C)) = (C ⊆ A)"
      -- {* Halmos, Naive Set Theory, page 16. *}
      by blast

    lemma Compl_UNIV_eq [simp]: "-UNIV = {}"
      by blast

    lemma Compl_empty_eq [simp]: "-{} = UNIV"
      by blast

    lemma Compl_subset_Compl_iff [iff]: "(-A ⊆ -B) = (B ⊆ A)"
      by blast

    lemma Compl_eq_Compl_iff [iff]: "(-A = -B) = (A = (B::'a set))"
      by blast

    text {* \medskip @{text Union}. *}

    lemma Union_empty [simp]: "Union({}) = {}"
      by blast

    lemma Union_UNIV [simp]: "Union UNIV = UNIV"
      by blast

    lemma Union_insert [simp]: "Union (insert a B) = a ∪ \<Union>B"
      by blast

    lemma Union_Un_distrib [simp]: "\<Union>(A Un B) = \<Union>A ∪ \<Union>B"
      by blast

    lemma Union_Int_subset: "\<Union>(A ∩ B) ⊆ \<Union>A ∩ \<Union>B"
      by blast

    lemma Union_empty_conv [iff]: "(\<Union>A = {}) = (∀x∈A. x = {})"
      by blast

    lemma empty_Union_conv [iff]: "({} = \<Union>A) = (∀x∈A. x = {})"
      by blast

    lemma Union_disjoint: "(\<Union>C ∩ A = {}) = (∀B∈C. B ∩ A = {})"
      by blast

    text {* \medskip @{text Inter}. *}

    lemma Inter_empty [simp]: "\<Inter>{} = UNIV"
      by blast

    lemma Inter_UNIV [simp]: "\<Inter>UNIV = {}"
      by blast

    lemma Inter_insert [simp]: "\<Inter>(insert a B) = a ∩ \<Inter>B"
      by blast

    lemma Inter_Un_subset: "\<Inter>A ∪ \<Inter>B ⊆ \<Inter>(A ∩ B)"
      by blast

    lemma Inter_Un_distrib: "\<Inter>(A ∪ B) = \<Inter>A ∩ \<Inter>B"
      by blast

    lemma Inter_UNIV_conv [iff]:
      "(\<Inter>A = UNIV) = (∀x∈A. x = UNIV)"
      "(UNIV = \<Inter>A) = (∀x∈A. x = UNIV)"
      by blast+

    text {*
      \medskip @{text UN} and @{text INT}.

      Basic identities: *}

    lemma UN_empty [simp]: "(\<Union>x∈{}. B x) = {}"
      by blast

    lemma UN_empty2 [simp]: "(\<Union>x∈A. {}) = {}"
      by blast

    lemma UN_singleton [simp]: "(\<Union>x∈A. {x}) = A"
      by blast

    lemma UN_absorb: "k ∈ I ==> A k ∪ (\<Union>i∈I. A i) = (\<Union>i∈I. A i)"
      by auto

    lemma INT_empty [simp]: "(\<Inter>x∈{}. B x) = UNIV"
      by blast

    lemma INT_absorb: "k ∈ I ==> A k ∩ (\<Inter>i∈I. A i) = (\<Inter>i∈I. A i)"
      by blast

    lemma UN_insert [simp]: "(\<Union>x∈insert a A. B x) = B a ∪ UNION A B"
      by blast

    lemma UN_Un: "(\<Union>i ∈ A ∪ B. M i) = (\<Union>i∈A. M i) ∪ (\<Union>i∈B. M i)"
      by blast

    lemma UN_UN_flatten: "(\<Union>x ∈ (\<Union>y∈A. B y). C x) = (\<Union>y∈A. \<Union>x∈B y. C x)"
      by blast

    lemma UN_subset_iff: "((\<Union>i∈I. A i) ⊆ B) = (∀i∈I. A i ⊆ B)"
      by blast

    lemma INT_subset_iff: "(B ⊆ (\<Inter>i∈I. A i)) = (∀i∈I. B ⊆ A i)"
      by blast

    lemma INT_insert [simp]: "(\<Inter>x ∈ insert a A. B x) = B a ∩ INTER A B"
      by blast

    lemma INT_Un: "(\<Inter>i ∈ A ∪ B. M i) = (\<Inter>i ∈ A. M i) ∩ (\<Inter>i∈B. M i)"
      by blast

    lemma INT_insert_distrib:
        "u ∈ A ==> (\<Inter>x∈A. insert a (B x)) = insert a (\<Inter>x∈A. B x)"
      by blast

    lemma Union_image_eq [simp]: "\<Union>(B`A) = (\<Union>x∈A. B x)"
      by blast

    lemma image_Union: "f ` \<Union>S = (\<Union>x∈S. f ` x)"
      by blast

    lemma Inter_image_eq [simp]: "\<Inter>(B`A) = (\<Inter>x∈A. B x)"
      by blast

    lemma UN_constant [simp]: "(\<Union>y∈A. c) = (if A = {} then {} else c)"
      by auto

    lemma INT_constant [simp]: "(\<Inter>y∈A. c) = (if A = {} then UNIV else c)"
      by auto

    lemma UN_eq: "(\<Union>x∈A. B x) = \<Union>({Y. ∃x∈A. Y = B x})"
      by blast

    lemma INT_eq: "(\<Inter>x∈A. B x) = \<Inter>({Y. ∃x∈A. Y = B x})"
      -- {* Look: it has an \emph{existential} quantifier *}
      by blast

    lemma UNION_empty_conv[iff]:
      "({} = (UN x:A. B x)) = (∀x∈A. B x = {})"
      "((UN x:A. B x) = {}) = (∀x∈A. B x = {})"
    by blast+

    lemma INTER_UNIV_conv[iff]:
     "(UNIV = (INT x:A. B x)) = (∀x∈A. B x = UNIV)"
     "((INT x:A. B x) = UNIV) = (∀x∈A. B x = UNIV)"
    by blast+

    text {* \medskip Distributive laws: *}

    lemma Int_Union: "A ∩ \<Union>B = (\<Union>C∈B. A ∩ C)"
      by blast

    lemma Int_Union2: "\<Union>B ∩ A = (\<Union>C∈B. C ∩ A)"
      by blast

    lemma Un_Union_image: "(\<Union>x∈C. A x ∪ B x) = \<Union>(A`C) ∪ \<Union>(B`C)"
      -- {* Devlin, Fundamentals of Contemporary Set Theory, page 12, exercise 5: *}
      -- {* Union of a family of unions *}
      by blast

    lemma UN_Un_distrib: "(\<Union>i∈I. A i ∪ B i) = (\<Union>i∈I. A i) ∪ (\<Union>i∈I. B i)"
      -- {* Equivalent version *}
      by blast

    lemma Un_Inter: "A ∪ \<Inter>B = (\<Inter>C∈B. A ∪ C)"
      by blast

    lemma Int_Inter_image: "(\<Inter>x∈C. A x ∩ B x) = \<Inter>(A`C) ∩ \<Inter>(B`C)"
      by blast

    lemma INT_Int_distrib: "(\<Inter>i∈I. A i ∩ B i) = (\<Inter>i∈I. A i) ∩ (\<Inter>i∈I. B i)"
      -- {* Equivalent version *}
      by blast

    lemma Int_UN_distrib: "B ∩ (\<Union>i∈I. A i) = (\<Union>i∈I. B ∩ A i)"
      -- {* Halmos, Naive Set Theory, page 35. *}
      by blast

    lemma Un_INT_distrib: "B ∪ (\<Inter>i∈I. A i) = (\<Inter>i∈I. B ∪ A i)"
      by blast

    lemma Int_UN_distrib2: "(\<Union>i∈I. A i) ∩ (\<Union>j∈J. B j) = (\<Union>i∈I. \<Union>j∈J. A i ∩ B j)"
      by blast

    lemma Un_INT_distrib2: "(\<Inter>i∈I. A i) ∪ (\<Inter>j∈J. B j) = (\<Inter>i∈I. \<Inter>j∈J. A i ∪ B j)"
      by blast

    text {* \medskip Bounded quantifiers.

      The following are not added to the default simpset because
      (a) they duplicate the body and (b) there are no similar rules for @{text Int}. *}

    lemma ball_Un: "(∀x ∈ A ∪ B. P x) = ((∀x∈A. P x) & (∀x∈B. P x))"
      by blast

    lemma bex_Un: "(∃x ∈ A ∪ B. P x) = ((∃x∈A. P x) | (∃x∈B. P x))"
      by blast

    lemma ball_UN: "(∀z ∈ UNION A B. P z) = (∀x∈A. ∀z ∈ B x. P z)"
      by blast

    lemma bex_UN: "(∃z ∈ UNION A B. P z) = (∃x∈A. ∃z∈B x. P z)"
      by blast

    text {* \medskip Set difference. *}

    lemma Diff_eq: "A - B = A ∩ (-B)"
      by blast

    lemma Diff_eq_empty_iff [simp]: "(A - B = {}) = (A ⊆ B)"
      by blast

    lemma Diff_cancel [simp]: "A - A = {}"
      by blast

    lemma Diff_idemp [simp]: "(A - B) - B = A - (B::'a set)"
    by blast

    lemma Diff_triv: "A ∩ B = {} ==> A - B = A"
      by (blast elim: equalityE)

    lemma empty_Diff [simp]: "{} - A = {}"
      by blast

    lemma Diff_empty [simp]: "A - {} = A"
      by blast

    lemma Diff_UNIV [simp]: "A - UNIV = {}"
      by blast

    lemma Diff_insert0 [simp]: "x ∉ A ==> A - insert x B = A - B"
      by blast

    lemma Diff_insert: "A - insert a B = A - B - {a}"
      -- {* NOT SUITABLE FOR REWRITING since @{text "{a} == insert a 0"} *}
      by blast

    lemma Diff_insert2: "A - insert a B = A - {a} - B"
      -- {* NOT SUITABLE FOR REWRITING since @{text "{a} == insert a 0"} *}
      by blast

    lemma insert_Diff_if: "insert x A - B = (if x ∈ B then A - B else insert x (A - B))"
      by auto

    lemma insert_Diff1 [simp]: "x ∈ B ==> insert x A - B = A - B"
      by blast

    lemma insert_Diff_single[simp]: "insert a (A - {a}) = insert a A"
    by blast

    lemma insert_Diff: "a ∈ A ==> insert a (A - {a}) = A"
      by blast

    lemma Diff_insert_absorb: "x ∉ A ==> (insert x A) - {x} = A"
      by auto

    lemma Diff_disjoint [simp]: "A ∩ (B - A) = {}"
      by blast

    lemma Diff_partition: "A ⊆ B ==> A ∪ (B - A) = B"
      by blast

    lemma double_diff: "A ⊆ B ==> B ⊆ C ==> B - (C - A) = A"
      by blast

    lemma Un_Diff_cancel [simp]: "A ∪ (B - A) = A ∪ B"
      by blast

    lemma Un_Diff_cancel2 [simp]: "(B - A) ∪ A = B ∪ A"
      by blast

    lemma Diff_Un: "A - (B ∪ C) = (A - B) ∩ (A - C)"
      by blast

    lemma Diff_Int: "A - (B ∩ C) = (A - B) ∪ (A - C)"
      by blast

    lemma Un_Diff: "(A ∪ B) - C = (A - C) ∪ (B - C)"
      by blast

    lemma Int_Diff: "(A ∩ B) - C = A ∩ (B - C)"
      by blast

    lemma Diff_Int_distrib: "C ∩ (A - B) = (C ∩ A) - (C ∩ B)"
      by blast

    lemma Diff_Int_distrib2: "(A - B) ∩ C = (A ∩ C) - (B ∩ C)"
      by blast

    lemma Diff_Compl [simp]: "A - (- B) = A ∩ B"
      by auto

    lemma Compl_Diff_eq [simp]: "- (A - B) = -A ∪ B"
      by blast

    text {* \medskip Quantification over type @{typ bool}. *}

    lemma all_bool_eq: "(∀b::bool. P b) = (P True & P False)"
      apply auto
      apply (tactic {* case_tac "b" 1 *}, auto)
      done

    lemma bool_induct: "P True ==> P False ==> P x"
      by (rule conjI [THEN all_bool_eq [THEN iffD2], THEN spec])

    lemma ex_bool_eq: "(∃b::bool. P b) = (P True | P False)"
      apply auto
      apply (tactic {* case_tac "b" 1 *}, auto)
      done

    lemma Un_eq_UN: "A ∪ B = (\<Union>b. if b then A else B)"
      by (auto simp add: split_if_mem2)

    lemma UN_bool_eq: "(\<Union>b::bool. A b) = (A True ∪ A False)"
      apply auto
      apply (tactic {* case_tac "b" 1 *}, auto)
      done

    lemma INT_bool_eq: "(\<Inter>b::bool. A b) = (A True ∩ A False)"
      apply auto
      apply (tactic {* case_tac "b" 1 *}, auto)
      done

    text {* \medskip @{text Pow} *}

    lemma Pow_empty [simp]: "Pow {} = {{}}"
      by (auto simp add: Pow_def)

    lemma Pow_insert: "Pow (insert a A) = Pow A ∪ (insert a ` Pow A)"
      by (blast intro: image_eqI [where ?x = "u - {a}", standard])

    lemma Pow_Compl: "Pow (- A) = {-B | B. A ∈ Pow B}"
      by (blast intro: exI [where ?x = "- u", standard])

    lemma Pow_UNIV [simp]: "Pow UNIV = UNIV"
      by blast

    lemma Un_Pow_subset: "Pow A ∪ Pow B ⊆ Pow (A ∪ B)"
      by blast

    lemma UN_Pow_subset: "(\<Union>x∈A. Pow (B x)) ⊆ Pow (\<Union>x∈A. B x)"
      by blast

    lemma subset_Pow_Union: "A ⊆ Pow (\<Union>A)"
      by blast

    lemma Union_Pow_eq [simp]: "\<Union>(Pow A) = A"
      by blast

    lemma Pow_Int_eq [simp]: "Pow (A ∩ B) = Pow A ∩ Pow B"
      by blast

    lemma Pow_INT_eq: "Pow (\<Inter>x∈A. B x) = (\<Inter>x∈A. Pow (B x))"
      by blast

    text {* \medskip Miscellany. *}

    lemma set_eq_subset: "(A = B) = (A ⊆ B & B ⊆ A)"
      by blast

    lemma subset_iff: "(A ⊆ B) = (∀t. t ∈ A --> t ∈ B)"
      by blast

    lemma subset_iff_psubset_eq: "(A ⊆ B) = ((A ⊂ B) | (A = B))"
      by (unfold psubset_def) blast

    lemma all_not_in_conv [iff]: "(∀x. x ∉ A) = (A = {})"
      by blast

    lemma ex_in_conv: "(∃x. x ∈ A) = (A ≠ {})"
      by blast

    lemma distinct_lemma: "f x ≠ f y ==> x ≠ y"
      by iprover

    text {* \medskip Miniscoping: pushing in quantifiers and big Unions
               and Intersections. *}

    lemma UN_simps [simp]:
      "!!a B C. (UN x:C. insert a (B x)) = (if C={} then {} else insert a (UN x:C. B x))"
      "!!A B C. (UN x:C. A x Un B)   = ((if C={} then {} else (UN x:C. A x) Un B))"
      "!!A B C. (UN x:C. A Un B x)   = ((if C={} then {} else A Un (UN x:C. B x)))"
      "!!A B C. (UN x:C. A x Int B)  = ((UN x:C. A x) Int B)"
      "!!A B C. (UN x:C. A Int B x)  = (A Int (UN x:C. B x))"
      "!!A B C. (UN x:C. A x - B)    = ((UN x:C. A x) - B)"
      "!!A B C. (UN x:C. A - B x)    = (A - (INT x:C. B x))"
      "!!A B. (UN x: Union A. B x) = (UN y:A. UN x:y. B x)"
      "!!A B C. (UN z: UNION A B. C z) = (UN  x:A. UN z: B(x). C z)"
      "!!A B f. (UN x:f`A. B x)     = (UN a:A. B (f a))"
      by auto

    lemma INT_simps [simp]:
      "!!A B C. (INT x:C. A x Int B) = (if C={} then UNIV else (INT x:C. A x) Int B)"
      "!!A B C. (INT x:C. A Int B x) = (if C={} then UNIV else A Int (INT x:C. B x))"
      "!!A B C. (INT x:C. A x - B)   = (if C={} then UNIV else (INT x:C. A x) - B)"
      "!!A B C. (INT x:C. A - B x)   = (if C={} then UNIV else A - (UN x:C. B x))"
      "!!a B C. (INT x:C. insert a (B x)) = insert a (INT x:C. B x)"
      "!!A B C. (INT x:C. A x Un B)  = ((INT x:C. A x) Un B)"
      "!!A B C. (INT x:C. A Un B x)  = (A Un (INT x:C. B x))"
      "!!A B. (INT x: Union A. B x) = (INT y:A. INT x:y. B x)"
      "!!A B C. (INT z: UNION A B. C z) = (INT x:A. INT z: B(x). C z)"
      "!!A B f. (INT x:f`A. B x)    = (INT a:A. B (f a))"
      by auto

    lemma ball_simps [simp]:
      "!!A P Q. (ALL x:A. P x | Q) = ((ALL x:A. P x) | Q)"
      "!!A P Q. (ALL x:A. P | Q x) = (P | (ALL x:A. Q x))"
      "!!A P Q. (ALL x:A. P --> Q x) = (P --> (ALL x:A. Q x))"
      "!!A P Q. (ALL x:A. P x --> Q) = ((EX x:A. P x) --> Q)"
      "!!P. (ALL x:{}. P x) = True"
      "!!P. (ALL x:UNIV. P x) = (ALL x. P x)"
      "!!a B P. (ALL x:insert a B. P x) = (P a & (ALL x:B. P x))"
      "!!A P. (ALL x:Union A. P x) = (ALL y:A. ALL x:y. P x)"
      "!!A B P. (ALL x: UNION A B. P x) = (ALL a:A. ALL x: B a. P x)"
      "!!P Q. (ALL x:Collect Q. P x) = (ALL x. Q x --> P x)"
      "!!A P f. (ALL x:f`A. P x) = (ALL x:A. P (f x))"
      "!!A P. (~(ALL x:A. P x)) = (EX x:A. ~P x)"
      by auto

    lemma bex_simps [simp]:
      "!!A P Q. (EX x:A. P x & Q) = ((EX x:A. P x) & Q)"
      "!!A P Q. (EX x:A. P & Q x) = (P & (EX x:A. Q x))"
      "!!P. (EX x:{}. P x) = False"
      "!!P. (EX x:UNIV. P x) = (EX x. P x)"
      "!!a B P. (EX x:insert a B. P x) = (P(a) | (EX x:B. P x))"
      "!!A P. (EX x:Union A. P x) = (EX y:A. EX x:y. P x)"
      "!!A B P. (EX x: UNION A B. P x) = (EX a:A. EX x:B a. P x)"
      "!!P Q. (EX x:Collect Q. P x) = (EX x. Q x & P x)"
      "!!A P f. (EX x:f`A. P x) = (EX x:A. P (f x))"
      "!!A P. (~(EX x:A. P x)) = (ALL x:A. ~P x)"
      by auto

    lemma ball_conj_distrib:
      "(ALL x:A. P x & Q x) = ((ALL x:A. P x) & (ALL x:A. Q x))"
      by blast

    lemma bex_disj_distrib:
      "(EX x:A. P x | Q x) = ((EX x:A. P x) | (EX x:A. Q x))"
      by blast

    text {* \medskip Maxiscoping: pulling out big Unions and Intersections. *}

    lemma UN_extend_simps:
      "!!a B C. insert a (UN x:C. B x) = (if C={} then {a} else (UN x:C. insert a (B x)))"
      "!!A B C. (UN x:C. A x) Un B    = (if C={} then B else (UN x:C. A x Un B))"
      "!!A B C. A Un (UN x:C. B x)   = (if C={} then A else (UN x:C. A Un B x))"
      "!!A B C. ((UN x:C. A x) Int B) = (UN x:C. A x Int B)"
      "!!A B C. (A Int (UN x:C. B x)) = (UN x:C. A Int B x)"
      "!!A B C. ((UN x:C. A x) - B) = (UN x:C. A x - B)"
      "!!A B C. (A - (INT x:C. B x)) = (UN x:C. A - B x)"
      "!!A B. (UN y:A. UN x:y. B x) = (UN x: Union A. B x)"
      "!!A B C. (UN  x:A. UN z: B(x). C z) = (UN z: UNION A B. C z)"
      "!!A B f. (UN a:A. B (f a)) = (UN x:f`A. B x)"
      by auto

    lemma INT_extend_simps:
      "!!A B C. (INT x:C. A x) Int B = (if C={} then B else (INT x:C. A x Int B))"
      "!!A B C. A Int (INT x:C. B x) = (if C={} then A else (INT x:C. A Int B x))"
      "!!A B C. (INT x:C. A x) - B   = (if C={} then UNIV-B else (INT x:C. A x - B))"
      "!!A B C. A - (UN x:C. B x)   = (if C={} then A else (INT x:C. A - B x))"
      "!!a B C. insert a (INT x:C. B x) = (INT x:C. insert a (B x))"
      "!!A B C. ((INT x:C. A x) Un B)  = (INT x:C. A x Un B)"
      "!!A B C. A Un (INT x:C. B x)  = (INT x:C. A Un B x)"
      "!!A B. (INT y:A. INT x:y. B x) = (INT x: Union A. B x)"
      "!!A B C. (INT x:A. INT z: B(x). C z) = (INT z: UNION A B. C z)"
      "!!A B f. (INT a:A. B (f a))    = (INT x:f`A. B x)"
      by auto

    subsubsection {* Monotonicity of various operations *}

    lemma image_mono: "A ⊆ B ==> f`A ⊆ f`B"
      by blast

    lemma Pow_mono: "A ⊆ B ==> Pow A ⊆ Pow B"
      by blast

    lemma Union_mono: "A ⊆ B ==> \<Union>A ⊆ \<Union>B"
      by blast

    lemma Inter_anti_mono: "B ⊆ A ==> \<Inter>A ⊆ \<Inter>B"
      by blast

    lemma UN_mono:
      "A ⊆ B ==> (!!x. x ∈ A ==> f x ⊆ g x) ==>
        (\<Union>x∈A. f x) ⊆ (\<Union>x∈B. g x)"
      by (blast dest: subsetD)

    lemma INT_anti_mono:
      "B ⊆ A ==> (!!x. x ∈ A ==> f x ⊆ g x) ==>
        (\<Inter>x∈A. f x) ⊆ (\<Inter>x∈A. g x)"
      -- {* The last inclusion is POSITIVE! *}
      by (blast dest: subsetD)

    lemma insert_mono: "C ⊆ D ==> insert a C ⊆ insert a D"
      by blast

    lemma Un_mono: "A ⊆ C ==> B ⊆ D ==> A ∪ B ⊆ C ∪ D"
      by blast

    lemma Int_mono: "A ⊆ C ==> B ⊆ D ==> A ∩ B ⊆ C ∩ D"
      by blast

    lemma Diff_mono: "A ⊆ C ==> D ⊆ B ==> A - B ⊆ C - D"
      by blast

    lemma Compl_anti_mono: "A ⊆ B ==> -B ⊆ -A"
      by blast

    text {* \medskip Monotonicity of implications. *}

    lemma in_mono: "A ⊆ B ==> x ∈ A --> x ∈ B"
      apply (rule impI)
      apply (erule subsetD, assumption)
      done

    lemma conj_mono: "P1 --> Q1 ==> P2 --> Q2 ==> (P1 & P2) --> (Q1 & Q2)"
      by iprover

    lemma disj_mono: "P1 --> Q1 ==> P2 --> Q2 ==> (P1 | P2) --> (Q1 | Q2)"
      by iprover

    lemma imp_mono: "Q1 --> P1 ==> P2 --> Q2 ==> (P1 --> P2) --> (Q1 --> Q2)"
      by iprover

    lemma imp_refl: "P --> P" ..

    lemma ex_mono: "(!!x. P x --> Q x) ==> (EX x. P x) --> (EX x. Q x)"
      by iprover

    lemma all_mono: "(!!x. P x --> Q x) ==> (ALL x. P x) --> (ALL x. Q x)"
      by iprover

    lemma Collect_mono: "(!!x. P x --> Q x) ==> Collect P ⊆ Collect Q"
      by blast

    lemma Int_Collect_mono:
        "A ⊆ B ==> (!!x. x ∈ A ==> P x --> Q x) ==> A ∩ Collect P ⊆ B ∩ Collect Q"
      by blast

    lemmas basic_monos =
      subset_refl imp_refl disj_mono conj_mono
      ex_mono Collect_mono in_mono

    lemma eq_to_mono: "a = b ==> c = d ==> b --> d ==> a --> c"
      by iprover

    lemma eq_to_mono2: "a = b ==> c = d ==> ~ b --> ~ d ==> ~ a --> ~ c"
      by iprover

    lemma Least_mono:
      "mono (f::'a::order => 'b::order) ==> EX x:S. ALL y:S. x <= y
        ==> (LEAST y. y : f ` S) = f (LEAST x. x : S)"
        -- {* Courtesy of Stephan Merz *}
      apply clarify
      apply (erule_tac P = "%x. x : S" in LeastI2_order, fast)
      apply (rule LeastI2_order)
      apply (auto elim: monoD intro!: order_antisym)
      done

    subsection {* Inverse image of a function *}

    constdefs
      vimage :: "('a => 'b) => 'b set => 'a set"    (infixr "-`" 90)
      "f -` B == {x. f x : B}"

    subsubsection {* Basic rules *}

    lemma vimage_eq [simp]: "(a : f -` B) = (f a : B)"
      by (unfold vimage_def) blast

    lemma vimage_singleton_eq: "(a : f -` {b}) = (f a = b)"
      by simp

    lemma vimageI [intro]: "f a = b ==> b:B ==> a : f -` B"
      by (unfold vimage_def) blast

    lemma vimageI2: "f a : A ==> a : f -` A"
      by (unfold vimage_def) fast

    lemma vimageE [elim!]: "a: f -` B ==> (!!x. f a = x ==> x:B ==> P) ==> P"
      by (unfold vimage_def) blast

    lemma vimageD: "a : f -` A ==> f a : A"
      by (unfold vimage_def) fast

    subsubsection {* Equations *}

    lemma vimage_empty [simp]: "f -` {} = {}"
      by blast

    lemma vimage_Compl: "f -` (-A) = -(f -` A)"
      by blast

    lemma vimage_Un [simp]: "f -` (A Un B) = (f -` A) Un (f -` B)"
      by blast

    lemma vimage_Int [simp]: "f -` (A Int B) = (f -` A) Int (f -` B)"
      by fast

    lemma vimage_Union: "f -` (Union A) = (UN X:A. f -` X)"
      by blast

    lemma vimage_UN: "f-`(UN x:A. B x) = (UN x:A. f -` B x)"
      by blast

    lemma vimage_INT: "f-`(INT x:A. B x) = (INT x:A. f -` B x)"
      by blast

    lemma vimage_Collect_eq [simp]: "f -` Collect P = {y. P (f y)}"
      by blast

    lemma vimage_Collect: "(!!x. P (f x) = Q x) ==> f -` (Collect P) = Collect Q"
      by blast

    lemma vimage_insert: "f-`(insert a B) = (f-`{a}) Un (f-`B)"
      -- {* NOT suitable for rewriting because of the recurrence of @{term "{a}"}. *}
      by blast

    lemma vimage_Diff: "f -` (A - B) = (f -` A) - (f -` B)"
      by blast

    lemma vimage_UNIV [simp]: "f -` UNIV = UNIV"
      by blast

    lemma vimage_eq_UN: "f-`B = (UN y: B. f-`{y})"
      -- {* NOT suitable for rewriting *}
      by blast

    lemma vimage_mono: "A ⊆ B ==> f -` A ⊆ f -` B"
      -- {* monotonicity *}
      by blast

    subsection {* Getting the Contents of a Singleton Set *}

    constdefs
      contents :: "'a set => 'a"
       "contents X == THE x. X = {x}"

    lemma contents_eq [simp]: "contents {x} = x"
    by (simp add: contents_def)

    subsection {* Transitivity rules for calculational reasoning *}

    lemma set_rev_mp: "x:A ==> A ⊆ B ==> x:B"
      by (rule subsetD)

    lemma set_mp: "A ⊆ B ==> x:A ==> x:B"
      by (rule subsetD)

    lemma ord_le_eq_trans: "a <= b ==> b = c ==> a <= c"
      by (rule subst)

    lemma ord_eq_le_trans: "a = b ==> b <= c ==> a <= c"
      by (rule ssubst)

    lemma ord_less_eq_trans: "a < b ==> b = c ==> a < c"
      by (rule subst)

    lemma ord_eq_less_trans: "a = b ==> b < c ==> a < c"
      by (rule ssubst)

    lemma order_less_subst2: "(a::'a::order) < b ==> f b < (c::'c::order) ==>
      (!!x y. x < y ==> f x < f y) ==> f a < c"
    proof -
      assume r: "!!x y. x < y ==> f x < f y"
      assume "a < b" hence "f a < f b" by (rule r)
      also assume "f b < c"
      finally (order_less_trans) show ?thesis .
    qed

    lemma order_less_subst1: "(a::'a::order) < f b ==> (b::'b::order) < c ==>
      (!!x y. x < y ==> f x < f y) ==> a < f c"
    proof -
      assume r: "!!x y. x < y ==> f x < f y"
      assume "a < f b"
      also assume "b < c" hence "f b < f c" by (rule r)
      finally (order_less_trans) show ?thesis .
    qed

    lemma order_le_less_subst2: "(a::'a::order) <= b ==> f b < (c::'c::order) ==>
      (!!x y. x <= y ==> f x <= f y) ==> f a < c"
    proof -
      assume r: "!!x y. x <= y ==> f x <= f y"
      assume "a <= b" hence "f a <= f b" by (rule r)
      also assume "f b < c"
      finally (order_le_less_trans) show ?thesis .
    qed

    lemma order_le_less_subst1: "(a::'a::order) <= f b ==> (b::'b::order) < c ==>
      (!!x y. x < y ==> f x < f y) ==> a < f c"
    proof -
      assume r: "!!x y. x < y ==> f x < f y"
      assume "a <= f b"
      also assume "b < c" hence "f b < f c" by (rule r)
      finally (order_le_less_trans) show ?thesis .
    qed

    lemma order_less_le_subst2: "(a::'a::order) < b ==> f b <= (c::'c::order) ==>
      (!!x y. x < y ==> f x < f y) ==> f a < c"
    proof -
      assume r: "!!x y. x < y ==> f x < f y"
      assume "a < b" hence "f a < f b" by (rule r)
      also assume "f b <= c"
      finally (order_less_le_trans) show ?thesis .
    qed

    lemma order_less_le_subst1: "(a::'a::order) < f b ==> (b::'b::order) <= c ==>
      (!!x y. x <= y ==> f x <= f y) ==> a < f c"
    proof -
      assume r: "!!x y. x <= y ==> f x <= f y"
      assume "a < f b"
      also assume "b <= c" hence "f b <= f c" by (rule r)
      finally (order_less_le_trans) show ?thesis .
    qed

    lemma order_subst1: "(a::'a::order) <= f b ==> (b::'b::order) <= c ==>
      (!!x y. x <= y ==> f x <= f y) ==> a <= f c"
    proof -
      assume r: "!!x y. x <= y ==> f x <= f y"
      assume "a <= f b"
      also assume "b <= c" hence "f b <= f c" by (rule r)
      finally (order_trans) show ?thesis .
    qed

    lemma order_subst2: "(a::'a::order) <= b ==> f b <= (c::'c::order) ==>
      (!!x y. x <= y ==> f x <= f y) ==> f a <= c"
    proof -
      assume r: "!!x y. x <= y ==> f x <= f y"
      assume "a <= b" hence "f a <= f b" by (rule r)
      also assume "f b <= c"
      finally (order_trans) show ?thesis .
    qed

    lemma ord_le_eq_subst: "a <= b ==> f b = c ==>
      (!!x y. x <= y ==> f x <= f y) ==> f a <= c"
    proof -
      assume r: "!!x y. x <= y ==> f x <= f y"
      assume "a <= b" hence "f a <= f b" by (rule r)
      also assume "f b = c"
      finally (ord_le_eq_trans) show ?thesis .
    qed

    lemma ord_eq_le_subst: "a = f b ==> b <= c ==>
      (!!x y. x <= y ==> f x <= f y) ==> a <= f c"
    proof -
      assume r: "!!x y. x <= y ==> f x <= f y"
      assume "a = f b"
      also assume "b <= c" hence "f b <= f c" by (rule r)
      finally (ord_eq_le_trans) show ?thesis .
    qed

    lemma ord_less_eq_subst: "a < b ==> f b = c ==>
      (!!x y. x < y ==> f x < f y) ==> f a < c"
    proof -
      assume r: "!!x y. x < y ==> f x < f y"
      assume "a < b" hence "f a < f b" by (rule r)
      also assume "f b = c"
      finally (ord_less_eq_trans) show ?thesis .
    qed

    lemma ord_eq_less_subst: "a = f b ==> b < c ==>
      (!!x y. x < y ==> f x < f y) ==> a < f c"
    proof -
      assume r: "!!x y. x < y ==> f x < f y"
      assume "a = f b"
      also assume "b < c" hence "f b < f c" by (rule r)
      finally (ord_eq_less_trans) show ?thesis .
    qed

    text {*
      Note that this list of rules is in reverse order of priorities.
    *}

    lemmas basic_trans_rules [trans] =
      order_less_subst2
      order_less_subst1
      order_le_less_subst2
      order_le_less_subst1
      order_less_le_subst2
      order_less_le_subst1
      order_subst2
      order_subst1
      ord_le_eq_subst
      ord_eq_le_subst
      ord_less_eq_subst
      ord_eq_less_subst
      forw_subst
      back_subst
      rev_mp
      mp
      set_rev_mp
      set_mp
      order_neq_le_trans
      order_le_neq_trans
      order_less_trans
      order_less_asym'
      order_le_less_trans
      order_less_le_trans
      order_trans
      order_antisym
      ord_le_eq_trans
      ord_eq_le_trans
      ord_less_eq_trans
      ord_eq_less_trans
      trans

    end

### Basic syntax

### Additional concrete syntax

#### Bounded quantifiers

### Rules and definitions

### Lemmas and proof tool setup

#### Relating predicates and sets

lemma CollectI:

      P a ==> a ∈ {x. P x}

lemma CollectD:

      a ∈ {x. P x} ==> P a

lemma Collect_cong:

      (!!x. P x = Q x) ==> {x. P x} = {x. Q x}

lemmas CollectE:

      [| a ∈ {x. P x}; P a ==> PROP W1 |] ==> PROP W1

lemmas CollectE:

      [| a ∈ {x. P x}; P a ==> PROP W1 |] ==> PROP W1

#### Bounded quantifiers

lemma ballI:

      (!!x. x ∈ A ==> P x) ==> ∀x∈A. P x

lemmas strip:

      (P ==> Q) ==> P --> Q

      (!!x. P x) ==> ∀x. P x

      (!!x. x ∈ A ==> P x) ==> ∀x∈A. P x

lemmas strip:

      (P ==> Q) ==> P --> Q

      (!!x. P x) ==> ∀x. P x

      (!!x. x ∈ A ==> P x) ==> ∀x∈A. P x

lemma bspec:

      [| ∀x∈A. P x; x ∈ A |] ==> P x

lemma ballE:

      [| ∀x∈A. P x; P x ==> Q; x ∉ A ==> Q |] ==> Q

theorem rev_ballE:

      [| ∀x∈A. P x; x ∉ A ==> Q; P x ==> Q |] ==> Q

lemma bexI:

      [| P x; x ∈ A |] ==> ∃x∈A. P x

lemma rev_bexI:

      [| x ∈ A; P x |] ==> ∃x∈A. P x

lemma bexCI:

      [| ∀x∈A. ¬ P x ==> P a; a ∈ A |] ==> ∃x∈A. P x

lemma bexE:

      [| ∃x∈A. P x; !!x. [| x ∈ A; P x |] ==> Q |] ==> Q

lemma ball_triv:

      (∀x∈A. P) = ((∃x. x ∈ A) --> P)

lemma bex_triv:

      (∃x∈A. P) = ((∃x. x ∈ A) ∧ P)

lemma bex_triv_one_point1:

      (∃x∈A. x = a) = (a ∈ A)

lemma bex_triv_one_point2:

      (∃x∈A. a = x) = (a ∈ A)

lemma bex_one_point1:

      (∃x∈A. x = a ∧ P x) = (a ∈ A ∧ P a)

lemma bex_one_point2:

      (∃x∈A. a = x ∧ P x) = (a ∈ A ∧ P a)

lemma ball_one_point1:

      (∀x∈A. x = a --> P x) = (a ∈ A --> P a)

lemma ball_one_point2:

      (∀x∈A. a = x --> P x) = (a ∈ A --> P a)

#### Congruence rules

lemma ball_cong:

      [| A = B; !!x. x ∈ B ==> P x = Q x |] ==> (∀x∈A. P x) = (∀x∈B. Q x)

lemma strong_ball_cong:

      [| A = B; !!x. x ∈ B =simp=> P x = Q x |] ==> (∀x∈A. P x) = (∀x∈B. Q x)

lemma bex_cong:

      [| A = B; !!x. x ∈ B ==> P x = Q x |] ==> (∃x∈A. P x) = (∃x∈B. Q x)

lemma strong_bex_cong:

      [| A = B; !!x. x ∈ B =simp=> P x = Q x |] ==> (∃x∈A. P x) = (∃x∈B. Q x)

#### Subsets

lemma subsetI:

      (!!x. x ∈ A ==> x ∈ B) ==> A ⊆ B

lemma subsetD:

      [| A ⊆ B; c ∈ A |] ==> c ∈ B

lemma rev_subsetD:

      [| c ∈ A; A ⊆ B |] ==> c ∈ B

lemma subsetCE:

      [| A ⊆ B; c ∉ A ==> P; c ∈ B ==> P |] ==> P

lemma contra_subsetD:

      [| A ⊆ B; c ∉ B |] ==> c ∉ A

lemma subset_refl:

      A ⊆ A

lemma subset_trans:

      [| A ⊆ B; B ⊆ C |] ==> A ⊆ C

#### Equality

lemma set_ext:

      (!!x. (x ∈ A) = (x ∈ B)) ==> A = B

lemma expand_set_eq:

      (A = B) = (∀x. (x ∈ A) = (x ∈ B))

lemma subset_antisym:

      [| A ⊆ B; B ⊆ A |] ==> A = B

lemmas equalityI:

      [| A ⊆ B; B ⊆ A |] ==> A = B

lemmas equalityI:

      [| A ⊆ B; B ⊆ A |] ==> A = B

lemma equalityD1:

      A = B ==> A ⊆ B

lemma equalityD2:

      A = B ==> B ⊆ A

lemma equalityE:

      [| A = B; [| A ⊆ B; B ⊆ A |] ==> P |] ==> P

lemma equalityCE:

      [| A = B; [| c ∈ A; c ∈ B |] ==> P; [| c ∉ A; c ∉ B |] ==> P |] ==> P

lemma setup_induction:

      [| p ∈ A; !!z. z ∈ A ==> p = z --> R |] ==> R

lemma eqset_imp_iff:

      A = B ==> (x ∈ A) = (x ∈ B)

lemma eqelem_imp_iff:

      x = y ==> (x ∈ A) = (y ∈ A)

#### The universal set -- UNIV

lemma UNIV_I:

      x ∈ UNIV

lemma UNIV_witness:

      ∃x. x ∈ UNIV

lemma subset_UNIV:

      A ⊆ UNIV

lemma ball_UNIV:

      Ball UNIV P = All P

lemma bex_UNIV:

      Bex UNIV P = Ex P

#### The empty set

lemma empty_iff:

      (c ∈ {}) = False

lemma emptyE:

      a ∈ {} ==> P

lemma empty_subsetI:

      {} ⊆ A

lemma equals0I:

      (!!y. y ∈ A ==> False) ==> A = {}

lemma equals0D:

      A = {} ==> a ∉ A

lemma ball_empty:

      Ball {} P = True

lemma bex_empty:

      Bex {} P = False

lemma UNIV_not_empty:

      UNIV ≠ {}

#### The Powerset operator -- Pow

lemma Pow_iff:

      (A ∈ Pow B) = (A ⊆ B)

lemma PowI:

      A ⊆ B ==> A ∈ Pow B

lemma PowD:

      A ∈ Pow B ==> A ⊆ B

lemma Pow_bottom:

      {} ∈ Pow B

lemma Pow_top:

      A ∈ Pow A

#### Set complement

lemma Compl_iff:

      (c ∈ - A) = (c ∉ A)

lemma ComplI:

      (c ∈ A ==> False) ==> c ∈ - A

lemma ComplD:

      c ∈ - A ==> c ∉ A

lemmas ComplE:

      [| c ∈ - A; c ∉ A ==> PROP W1 |] ==> PROP W1

lemmas ComplE:

      [| c ∈ - A; c ∉ A ==> PROP W1 |] ==> PROP W1

#### Binary union -- Un

lemma Un_iff:

      (c ∈ A ∪ B) = (c ∈ A ∨ c ∈ B)

lemma UnI1:

      c ∈ A ==> c ∈ A ∪ B

lemma UnI2:

      c ∈ B ==> c ∈ A ∪ B

lemma UnCI:

      (c ∉ B ==> c ∈ A) ==> c ∈ A ∪ B

lemma UnE:

      [| c ∈ A ∪ B; c ∈ A ==> P; c ∈ B ==> P |] ==> P

#### Binary intersection -- Int

lemma Int_iff:

      (c ∈ A ∩ B) = (c ∈ A ∧ c ∈ B)

lemma IntI:

      [| c ∈ A; c ∈ B |] ==> c ∈ A ∩ B

lemma IntD1:

      c ∈ A ∩ B ==> c ∈ A

lemma IntD2:

      c ∈ A ∩ B ==> c ∈ B

lemma IntE:

      [| c ∈ A ∩ B; [| c ∈ A; c ∈ B |] ==> P |] ==> P

#### Set difference

lemma Diff_iff:

      (c ∈ A - B) = (c ∈ A ∧ c ∉ B)

lemma DiffI:

      [| c ∈ A; c ∉ B |] ==> c ∈ A - B

lemma DiffD1:

      c ∈ A - B ==> c ∈ A

lemma DiffD2:

      [| c ∈ A - B; c ∈ B |] ==> P

lemma DiffE:

      [| c ∈ A - B; [| c ∈ A; c ∉ B |] ==> P |] ==> P

#### Augmenting a set -- insert

lemma insert_iff:

      (a ∈ insert b A) = (a = b ∨ a ∈ A)

lemma insertI1:

      a ∈ insert a B

lemma insertI2:

      a ∈ B ==> a ∈ insert b B

lemma insertE:

      [| a ∈ insert b A; a = b ==> P; a ∈ A ==> P |] ==> P

lemma insertCI:

      (a ∉ B ==> a = b) ==> a ∈ insert b B

lemma subset_insert_iff:

      (A ⊆ insert x B) = (if x ∈ A then A - {x} ⊆ B else A ⊆ B)

#### Singletons, using insert

lemma singletonI:

      a ∈ {a}

lemma singletonD:

      b ∈ {a} ==> b = a

lemmas singletonE:

      [| b ∈ {a}; b = a ==> PROP W1 |] ==> PROP W1

lemmas singletonE:

      [| b ∈ {a}; b = a ==> PROP W1 |] ==> PROP W1

lemma singleton_iff:

      (b ∈ {a}) = (b = a)

lemma singleton_inject:

      {a} = {b} ==> a = b

lemma singleton_insert_inj_eq:

      ({b} = insert a A) = (a = b ∧ A ⊆ {b})

lemma singleton_insert_inj_eq':

      (insert a A = {b}) = (a = b ∧ A ⊆ {b})

lemma subset_singletonD:

      A ⊆ {x} ==> A = {} ∨ A = {x}

lemma singleton_conv:

      {x. x = a} = {a}

lemma singleton_conv2:

      {x. a = x} = {a}

lemma diff_single_insert:

      [| A - {x} ⊆ B; x ∈ A |] ==> A ⊆ insert x B

#### Unions of families

lemma UN_iff:

      (b ∈ (UN x:A. B x)) = (∃x∈A. b ∈ B x)

lemma UN_I:

      [| a ∈ A; b ∈ B a |] ==> b ∈ (UN x:A. B x)

lemma UN_E:

      [| b ∈ (UN x:A. B x); !!x. [| x ∈ A; b ∈ B x |] ==> R |] ==> R

lemma UN_cong:

      [| A = B; !!x. x ∈ B ==> C x = D x |] ==> (UN x:A. C x) = (UN x:B. D x)

#### Intersections of families

lemma INT_iff:

      (b ∈ (INT x:A. B x)) = (∀x∈A. b ∈ B x)

lemma INT_I:

      (!!x. x ∈ A ==> b ∈ B x) ==> b ∈ (INT x:A. B x)

lemma INT_D:

      [| b ∈ (INT x:A. B x); a ∈ A |] ==> b ∈ B a

lemma INT_E:

      [| b ∈ (INT x:A. B x); b ∈ B a ==> R; a ∉ A ==> R |] ==> R

lemma INT_cong:

      [| A = B; !!x. x ∈ B ==> C x = D x |] ==> (INT x:A. C x) = (INT x:B. D x)

#### Union

lemma Union_iff:

      (A ∈ Union C) = (∃X∈C. A ∈ X)

lemma UnionI:

      [| X ∈ C; A ∈ X |] ==> A ∈ Union C

lemma UnionE:

      [| A ∈ Union C; !!X. [| A ∈ X; X ∈ C |] ==> R |] ==> R

#### Inter

lemma Inter_iff:

      (A ∈ Inter C) = (∀X∈C. A ∈ X)

lemma InterI:

      (!!X. X ∈ C ==> A ∈ X) ==> A ∈ Inter C

lemma InterD:

      [| A ∈ Inter C; X ∈ C |] ==> A ∈ X

lemma InterE:

      [| A ∈ Inter C; X ∉ C ==> R; A ∈ X ==> R |] ==> R

lemma image_eqI:

      [| b = f x; x ∈ A |] ==> b ∈ f ` A

lemma imageI:

      x ∈ A ==> f x ∈ f ` A

lemma rev_image_eqI:

      [| x ∈ A; b = f x |] ==> b ∈ f ` A

lemma imageE:

      [| b ∈ f ` A; !!x. [| b = f x; x ∈ A |] ==> P |] ==> P

lemma image_Un:

      f ` (A ∪ B) = f ` A ∪ f ` B

lemma image_iff:

      (z ∈ f ` A) = (∃x∈A. z = f x)

lemma image_subset_iff:

      (f ` A ⊆ B) = (∀x∈A. f x ∈ B)

lemma subset_image_iff:

      (B ⊆ f ` A) = (∃AA⊆A. B = f ` AA)

lemma image_subsetI:

      (!!x. x ∈ A ==> f x ∈ B) ==> f ` A ⊆ B

lemma range_eqI:

      b = f x ==> b ∈ range f

lemma rangeI:

      f x ∈ range f

lemma rangeE:

      [| b ∈ range f; !!x. b = f x ==> P |] ==> P

#### Set reasoning tools

lemma split_if_eq1:

      ((if Q then x else y) = b) = ((Q --> x = b) ∧ (¬ Q --> y = b))

lemma split_if_eq2:

      (a = (if Q then x else y)) = ((Q --> a = x) ∧ (¬ Q --> a = y))

lemma split_if_mem1:

      ((if Q then x else y) ∈ b) = ((Q --> x ∈ b) ∧ (¬ Q --> y ∈ b))

lemma split_if_mem2:

      (a ∈ (if Q then x else y)) = ((Q --> a ∈ x) ∧ (¬ Q --> a ∈ y))

lemmas split_ifs:

      (if P then Q else R) = ((P --> Q) ∧ (¬ P --> R))

      ((if Q then x else y) = b) = ((Q --> x = b) ∧ (¬ Q --> y = b))

      (a = (if Q then x else y)) = ((Q --> a = x) ∧ (¬ Q --> a = y))

      ((if Q then x else y) ∈ b) = ((Q --> x ∈ b) ∧ (¬ Q --> y ∈ b))

      (a ∈ (if Q then x else y)) = ((Q --> a ∈ x) ∧ (¬ Q --> a ∈ y))

lemmas split_ifs:

      (if P then Q else R) = ((P --> Q) ∧ (¬ P --> R))

      ((if Q then x else y) = b) = ((Q --> x = b) ∧ (¬ Q --> y = b))

      (a = (if Q then x else y)) = ((Q --> a = x) ∧ (¬ Q --> a = y))

      ((if Q then x else y) ∈ b) = ((Q --> x ∈ b) ∧ (¬ Q --> y ∈ b))

      (a ∈ (if Q then x else y)) = ((Q --> a ∈ x) ∧ (¬ Q --> a ∈ y))

lemmas mem_simps:

      (a ∈ insert b A) = (a = b ∨ a ∈ A)

      (c ∈ {}) = False

      (c ∈ A ∪ B) = (c ∈ A ∨ c ∈ B)

      (c ∈ A ∩ B) = (c ∈ A ∧ c ∈ B)

      (c ∈ - A) = (c ∉ A)

      (c ∈ A - B) = (c ∈ A ∧ c ∉ B)

      (a ∈ {x. P x}) = P a

      (b ∈ (UN x:A. B x)) = (∃x∈A. b ∈ B x)

      (A ∈ Union C) = (∃X∈C. A ∈ X)

      (b ∈ (INT x:A. B x)) = (∀x∈A. b ∈ B x)

      (A ∈ Inter C) = (∀X∈C. A ∈ X)

lemmas mem_simps:

      (a ∈ insert b A) = (a = b ∨ a ∈ A)

      (c ∈ {}) = False

      (c ∈ A ∪ B) = (c ∈ A ∨ c ∈ B)

      (c ∈ A ∩ B) = (c ∈ A ∧ c ∈ B)

      (c ∈ - A) = (c ∉ A)

      (c ∈ A - B) = (c ∈ A ∧ c ∉ B)

      (a ∈ {x. P x}) = P a

      (b ∈ (UN x:A. B x)) = (∃x∈A. b ∈ B x)

      (A ∈ Union C) = (∃X∈C. A ∈ X)

      (b ∈ (INT x:A. B x)) = (∀x∈A. b ∈ B x)

      (A ∈ Inter C) = (∀X∈C. A ∈ X)

#### The ``proper subset'' relation

lemma psubsetI:

      [| A ⊆ B; A ≠ B |] ==> A ⊂ B

lemma psubsetE:

      [| A ⊂ B; [| A ⊆ B; ¬ B ⊆ A |] ==> R |] ==> R

lemma psubset_insert_iff:

      (A ⊂ insert x B) =
      (if x ∈ B then A ⊂ B else if x ∈ A then A - {x} ⊂ B else A ⊆ B)

lemma psubset_eq:

      (A ⊂ B) = (A ⊆ B ∧ A ≠ B)

lemma psubset_imp_subset:

      A ⊂ B ==> A ⊆ B

lemma psubset_trans:

      [| A ⊂ B; B ⊂ C |] ==> A ⊂ C

lemma psubsetD:

      [| A ⊂ B; c ∈ A |] ==> c ∈ B

lemma psubset_subset_trans:

      [| A ⊂ B; B ⊆ C |] ==> A ⊂ C

lemma subset_psubset_trans:

      [| A ⊆ B; B ⊂ C |] ==> A ⊂ C

lemma psubset_imp_ex_mem:

      A ⊂ B ==> ∃b. b ∈ B - A

lemma atomize_ball:

      (!!x. x ∈ A ==> P x) == ∀x∈A. P x

### Further set-theory lemmas

#### Derived rules involving subsets.

lemma subset_insertI:

      B ⊆ insert a B

lemma subset_insertI2:

      A ⊆ B ==> A ⊆ insert b B

lemma subset_insert:

      x ∉ A ==> (A ⊆ insert x B) = (A ⊆ B)

lemma Union_upper:

      B ∈ A ==> B ⊆ Union A

lemma Union_least:

      (!!X. X ∈ A ==> X ⊆ C) ==> Union A ⊆ C

lemma UN_upper:

      a ∈ A ==> B a ⊆ (UN x:A. B x)

lemma UN_least:

      (!!x. x ∈ A ==> B x ⊆ C) ==> (UN x:A. B x) ⊆ C

lemma Inter_lower:

      B ∈ A ==> Inter A ⊆ B

lemma Inter_subset:

      [| !!X. X ∈ A ==> X ⊆ B; A ≠ {} |] ==> Inter A ⊆ B

lemma Inter_greatest:

      (!!X. X ∈ A ==> C ⊆ X) ==> C ⊆ Inter A

lemma INT_lower:

      a ∈ A ==> (INT x:A. B x) ⊆ B a

lemma INT_greatest:

      (!!x. x ∈ A ==> C ⊆ B x) ==> C ⊆ (INT x:A. B x)

lemma Un_upper1:

      A ⊆ A ∪ B

lemma Un_upper2:

      B ⊆ A ∪ B

lemma Un_least:

      [| A ⊆ C; B ⊆ C |] ==> A ∪ B ⊆ C

lemma Int_lower1:

      A ∩ B ⊆ A

lemma Int_lower2:

      A ∩ B ⊆ B

lemma Int_greatest:

      [| C ⊆ A; C ⊆ B |] ==> C ⊆ A ∩ B

lemma Diff_subset:

      A - B ⊆ A

lemma Diff_subset_conv:

      (A - B ⊆ C) = (A ⊆ B ∪ C)

lemma mono_Un:

      mono f ==> f A ∪ f B ⊆ f (A ∪ B)

lemma mono_Int:

      mono f ==> f (A ∩ B) ⊆ f A ∩ f B

#### Equalities involving union, intersection, inclusion, etc.

lemma Collect_const:

      {s. P} = (if P then UNIV else {})

lemma subset_empty:

      (A ⊆ {}) = (A = {})

lemma not_psubset_empty:

      ¬ A ⊂ {}

lemma Collect_empty_eq:

      (Collect P = {}) = (∀x. ¬ P x)

lemma Collect_neg_eq:

      {x. ¬ P x} = - {x. P x}

lemma Collect_disj_eq:

      {x. P x ∨ Q x} = {x. P x} ∪ {x. Q x}

lemma Collect_imp_eq:

      {x. P x --> Q x} = - {x. P x} ∪ {x. Q x}

lemma Collect_conj_eq:

      {x. P x ∧ Q x} = {x. P x} ∩ {x. Q x}

lemma Collect_all_eq:

      {x. ∀y. P x y} = (INT y. {x. P x y})

lemma Collect_ball_eq:

      {x. ∀y∈A. P x y} = (INT y:A. {x. P x y})

lemma Collect_ex_eq:

      {x. ∃y. P x y} = (UN y. {x. P x y})

lemma Collect_bex_eq:

      {x. ∃y∈A. P x y} = (UN y:A. {x. P x y})

lemma insert_is_Un:

      insert a A = {a} ∪ A

lemma insert_not_empty:

      insert a A ≠ {}

lemmas empty_not_insert:

      {} ≠ insert a A

lemmas empty_not_insert:

      {} ≠ insert a A

lemma insert_absorb:

      a ∈ A ==> insert a A = A

lemma insert_absorb2:

      insert x (insert x A) = insert x A

lemma insert_commute:

      insert x (insert y A) = insert y (insert x A)

lemma insert_subset:

      (insert x A ⊆ B) = (x ∈ B ∧ A ⊆ B)

lemma mk_disjoint_insert:

      a ∈ A ==> ∃B. A = insert a B ∧ a ∉ B

lemma insert_Collect:

      insert a (Collect P) = {u. u ≠ a --> P u}

lemma UN_insert_distrib:

      u ∈ A ==> (UN x:A. insert a (B x)) = insert a (UN x:A. B x)

lemma insert_inter_insert:

      insert a A ∩ insert a B = insert a (A ∩ B)

lemma insert_disjoint:

      (insert a A ∩ B = {}) = (a ∉ B ∧ A ∩ B = {})

      ({} = insert a A ∩ B) = (a ∉ B ∧ {} = A ∩ B)

lemma disjoint_insert:

      (B ∩ insert a A = {}) = (a ∉ B ∧ B ∩ A = {})

      ({} = A ∩ insert b B) = (b ∉ A ∧ {} = A ∩ B)

lemma image_empty:

      f ` {} = {}

lemma image_insert:

      f ` insert a B = insert (f a) (f ` B)

lemma image_constant:

      x ∈ A ==> (%x. c) ` A = {c}

lemma image_image:

      f ` g ` A = (%x. f (g x)) ` A

lemma insert_image:

      x ∈ A ==> insert (f x) (f ` A) = f ` A

lemma image_is_empty:

      (f ` A = {}) = (A = {})

lemma image_Collect:

      f ` {x. P x} = {f x |x. P x}

lemma if_image_distrib:

      (%x. if P x then f x else g x) ` S = f ` (S ∩ {x. P x}) ∪ g ` (S ∩ {x. ¬ P x})

lemma image_cong:

      [| M = N; !!x. x ∈ N ==> f x = g x |] ==> f ` M = g ` N

lemma full_SetCompr_eq:

      {u. ∃x. u = f x} = range f

lemma range_composition:

      range (%x. f (g x)) = f ` range g

lemma Int_absorb:

      A ∩ A = A

lemma Int_left_absorb:

      A ∩ (A ∩ B) = A ∩ B

lemma Int_commute:

      A ∩ B = B ∩ A

lemma Int_left_commute:

      A ∩ (B ∩ C) = B ∩ (A ∩ C)

lemma Int_assoc:

      A ∩ B ∩ C = A ∩ (B ∩ C)

lemmas Int_ac:

      A ∩ B ∩ C = A ∩ (B ∩ C)

      A ∩ (A ∩ B) = A ∩ B

      A ∩ B = B ∩ A

      A ∩ (B ∩ C) = B ∩ (A ∩ C)

lemmas Int_ac:

      A ∩ B ∩ C = A ∩ (B ∩ C)

      A ∩ (A ∩ B) = A ∩ B

      A ∩ B = B ∩ A

      A ∩ (B ∩ C) = B ∩ (A ∩ C)

lemma Int_absorb1:

      B ⊆ A ==> A ∩ B = B

lemma Int_absorb2:

      A ⊆ B ==> A ∩ B = A

lemma Int_empty_left:

      {} ∩ B = {}

lemma Int_empty_right:

      A ∩ {} = {}

lemma disjoint_eq_subset_Compl:

      (A ∩ B = {}) = (A ⊆ - B)

lemma disjoint_iff_not_equal:

      (A ∩ B = {}) = (∀x∈A. ∀y∈B. x ≠ y)

lemma Int_UNIV_left:

      UNIV ∩ B = B

lemma Int_UNIV_right:

      A ∩ UNIV = A

lemma Int_eq_Inter:

      A ∩ B = Inter {A, B}

lemma Int_Un_distrib:

      A ∩ (B ∪ C) = A ∩ B ∪ A ∩ C

lemma Int_Un_distrib2:

      (B ∪ C) ∩ A = B ∩ A ∪ C ∩ A

lemma Int_UNIV:

      (A ∩ B = UNIV) = (A = UNIV ∧ B = UNIV)

lemma Int_subset_iff:

      (C ⊆ A ∩ B) = (C ⊆ A ∧ C ⊆ B)

lemma Int_Collect:

      (x ∈ A ∩ {x. P x}) = (x ∈ A ∧ P x)

lemma Un_absorb:

      A ∪ A = A

lemma Un_left_absorb:

      A ∪ (A ∪ B) = A ∪ B

lemma Un_commute:

      A ∪ B = B ∪ A

lemma Un_left_commute:

      A ∪ (B ∪ C) = B ∪ (A ∪ C)

lemma Un_assoc:

      A ∪ B ∪ C = A ∪ (B ∪ C)

lemmas Un_ac:

      A ∪ B ∪ C = A ∪ (B ∪ C)

      A ∪ (A ∪ B) = A ∪ B

      A ∪ B = B ∪ A

      A ∪ (B ∪ C) = B ∪ (A ∪ C)

lemmas Un_ac:

      A ∪ B ∪ C = A ∪ (B ∪ C)

      A ∪ (A ∪ B) = A ∪ B

      A ∪ B = B ∪ A

      A ∪ (B ∪ C) = B ∪ (A ∪ C)

lemma Un_absorb1:

      A ⊆ B ==> A ∪ B = B

lemma Un_absorb2:

      B ⊆ A ==> A ∪ B = A

lemma Un_empty_left:

      {} ∪ B = B

lemma Un_empty_right:

      A ∪ {} = A

lemma Un_UNIV_left:

      UNIV ∪ B = UNIV

lemma Un_UNIV_right:

      A ∪ UNIV = UNIV

lemma Un_eq_Union:

      A ∪ B = Union {A, B}

lemma Un_insert_left:

      insert a B ∪ C = insert a (B ∪ C)

lemma Un_insert_right:

      A ∪ insert a B = insert a (A ∪ B)

lemma Int_insert_left:

      insert a B ∩ C = (if a ∈ C then insert a (B ∩ C) else B ∩ C)

lemma Int_insert_right:

      A ∩ insert a B = (if a ∈ A then insert a (A ∩ B) else A ∩ B)

lemma Un_Int_distrib:

      A ∪ B ∩ C = (A ∪ B) ∩ (A ∪ C)

lemma Un_Int_distrib2:

      B ∩ C ∪ A = (B ∪ A) ∩ (C ∪ A)

lemma Un_Int_crazy:

      A ∩ B ∪ B ∩ C ∪ C ∩ A = (A ∪ B) ∩ (B ∪ C) ∩ (C ∪ A)

lemma subset_Un_eq:

      (A ⊆ B) = (A ∪ B = B)

lemma Un_empty:

      (A ∪ B = {}) = (A = {} ∧ B = {})

lemma Un_subset_iff:

      (A ∪ B ⊆ C) = (A ⊆ C ∧ B ⊆ C)

lemma Un_Diff_Int:

      A - B ∪ A ∩ B = A

lemma Compl_disjoint:

      A ∩ - A = {}

lemma Compl_disjoint2:

      - A ∩ A = {}

lemma Compl_partition:

      A ∪ - A = UNIV

lemma Compl_partition2:

      - A ∪ A = UNIV

lemma double_complement:

      - (- A) = A

lemma Compl_Un:

      - (A ∪ B) = - A ∩ - B

lemma Compl_Int:

      - (A ∩ B) = - A ∪ - B

lemma Compl_UN:

      - (UN x:A. B x) = (INT x:A. - B x)

lemma Compl_INT:

      - (INT x:A. B x) = (UN x:A. - B x)

lemma subset_Compl_self_eq:

      (A ⊆ - A) = (A = {})

lemma Un_Int_assoc_eq:

      (A ∩ B ∪ C = A ∩ (B ∪ C)) = (C ⊆ A)

lemma Compl_UNIV_eq:

      - UNIV = {}

lemma Compl_empty_eq:

      - {} = UNIV

lemma Compl_subset_Compl_iff:

      (- A ⊆ - B) = (B ⊆ A)

lemma Compl_eq_Compl_iff:

      (- A = - B) = (A = B)

lemma Union_empty:

      Union {} = {}

lemma Union_UNIV:

      Union UNIV = UNIV

lemma Union_insert:

      Union (insert a B) = a ∪ Union B

lemma Union_Un_distrib:

      Union (A ∪ B) = Union A ∪ Union B

lemma Union_Int_subset:

      Union (A ∩ B) ⊆ Union A ∩ Union B

lemma Union_empty_conv:

      (Union A = {}) = (∀x∈A. x = {})

lemma empty_Union_conv:

      ({} = Union A) = (∀x∈A. x = {})

lemma Union_disjoint:

      (Union C ∩ A = {}) = (∀B∈C. B ∩ A = {})

lemma Inter_empty:

      Inter {} = UNIV

lemma Inter_UNIV:

      Inter UNIV = {}

lemma Inter_insert:

      Inter (insert a B) = a ∩ Inter B

lemma Inter_Un_subset:

      Inter A ∪ Inter B ⊆ Inter (A ∩ B)

lemma Inter_Un_distrib:

      Inter (A ∪ B) = Inter A ∩ Inter B

lemma Inter_UNIV_conv:

      (Inter A = UNIV) = (∀x∈A. x = UNIV)

      (UNIV = Inter A) = (∀x∈A. x = UNIV)

lemma UN_empty:

      (UN x:{}. B x) = {}

lemma UN_empty2:

      (UN x:A. {}) = {}

lemma UN_singleton:

      (UN x:A. {x}) = A

lemma UN_absorb:

      k ∈ I ==> A k ∪ (UN i:I. A i) = (UN i:I. A i)

lemma INT_empty:

      (INT x:{}. B x) = UNIV

lemma INT_absorb:

      k ∈ I ==> A k ∩ (INT i:I. A i) = (INT i:I. A i)

lemma UN_insert:

      (UN x:insert a A. B x) = B a ∪ UNION A B

lemma UN_Un:

      (UN i:A ∪ B. M i) = (UN i:A. M i) ∪ (UN i:B. M i)

lemma UN_UN_flatten:

      (UN x:UN y:A. B y. C x) = (UN y:A. UN x:B y. C x)

lemma UN_subset_iff:

      ((UN i:I. A i) ⊆ B) = (∀i∈I. A i ⊆ B)

lemma INT_subset_iff:

      (B ⊆ (INT i:I. A i)) = (∀i∈I. B ⊆ A i)

lemma INT_insert:

      (INT x:insert a A. B x) = B a ∩ INTER A B

lemma INT_Un:

      (INT i:A ∪ B. M i) = (INT i:A. M i) ∩ (INT i:B. M i)

lemma INT_insert_distrib:

      u ∈ A ==> (INT x:A. insert a (B x)) = insert a (INT x:A. B x)

lemma Union_image_eq:

      Union (B ` A) = (UN x:A. B x)

lemma image_Union:

      f ` Union S = (UN x:S. f ` x)

lemma Inter_image_eq:

      Inter (B ` A) = (INT x:A. B x)

lemma UN_constant:

      (UN y:A. c) = (if A = {} then {} else c)

lemma INT_constant:

      (INT y:A. c) = (if A = {} then UNIV else c)

lemma UN_eq:

      (UN x:A. B x) = Union {Y. ∃x∈A. Y = B x}

lemma INT_eq:

      (INT x:A. B x) = Inter {Y. ∃x∈A. Y = B x}

lemma UNION_empty_conv:

      ({} = (UN x:A. B x)) = (∀x∈A. B x = {})

      ((UN x:A. B x) = {}) = (∀x∈A. B x = {})

lemma INTER_UNIV_conv:

      (UNIV = (INT x:A. B x)) = (∀x∈A. B x = UNIV)

      ((INT x:A. B x) = UNIV) = (∀x∈A. B x = UNIV)

lemma Int_Union:

      A ∩ Union B = (UN C:B. A ∩ C)

lemma Int_Union2:

      Union B ∩ A = (UN C:B. C ∩ A)

lemma Un_Union_image:

      (UN x:C. A x ∪ B x) = Union (A ` C) ∪ Union (B ` C)

lemma UN_Un_distrib:

      (UN i:I. A i ∪ B i) = (UN i:I. A i) ∪ (UN i:I. B i)

lemma Un_Inter:

      A ∪ Inter B = (INT C:B. A ∪ C)

lemma Int_Inter_image:

      (INT x:C. A x ∩ B x) = Inter (A ` C) ∩ Inter (B ` C)

lemma INT_Int_distrib:

      (INT i:I. A i ∩ B i) = (INT i:I. A i) ∩ (INT i:I. B i)

lemma Int_UN_distrib:

      B ∩ (UN i:I. A i) = (UN i:I. B ∩ A i)

lemma Un_INT_distrib:

      B ∪ (INT i:I. A i) = (INT i:I. B ∪ A i)

lemma Int_UN_distrib2:

      (UN i:I. A i) ∩ (UN j:J. B j) = (UN i:I. UN j:J. A i ∩ B j)

lemma Un_INT_distrib2:

      (INT i:I. A i) ∪ (INT j:J. B j) = (INT i:I. INT j:J. A i ∪ B j)

lemma ball_Un:

      (∀x∈A ∪ B. P x) = ((∀x∈A. P x) ∧ (∀x∈B. P x))

lemma bex_Un:

      (∃x∈A ∪ B. P x) = ((∃x∈A. P x) ∨ (∃x∈B. P x))

lemma ball_UN:

      (∀z∈UNION A B. P z) = (∀x∈A. ∀z∈B x. P z)

lemma bex_UN:

      (∃z∈UNION A B. P z) = (∃x∈A. ∃z∈B x. P z)

lemma Diff_eq:

      A - B = A ∩ - B

lemma Diff_eq_empty_iff:

      (A - B = {}) = (A ⊆ B)

lemma Diff_cancel:

      A - A = {}

lemma Diff_idemp:

      A - B - B = A - B

lemma Diff_triv:

      A ∩ B = {} ==> A - B = A

lemma empty_Diff:

      {} - A = {}

lemma Diff_empty:

      A - {} = A

lemma Diff_UNIV:

      A - UNIV = {}

lemma Diff_insert0:

      x ∉ A ==> A - insert x B = A - B

lemma Diff_insert:

      A - insert a B = A - B - {a}

lemma Diff_insert2:

      A - insert a B = A - {a} - B

lemma insert_Diff_if:

      insert x A - B = (if x ∈ B then A - B else insert x (A - B))

lemma insert_Diff1:

      x ∈ B ==> insert x A - B = A - B

lemma insert_Diff_single:

      insert a (A - {a}) = insert a A

lemma insert_Diff:

      a ∈ A ==> insert a (A - {a}) = A

lemma Diff_insert_absorb:

      x ∉ A ==> insert x A - {x} = A

lemma Diff_disjoint:

      A ∩ (B - A) = {}

lemma Diff_partition:

      A ⊆ B ==> A ∪ (B - A) = B

lemma double_diff:

      [| A ⊆ B; B ⊆ C |] ==> B - (C - A) = A

lemma Un_Diff_cancel:

      A ∪ (B - A) = A ∪ B

lemma Un_Diff_cancel2:

      B - A ∪ A = B ∪ A

lemma Diff_Un:

      A - (B ∪ C) = (A - B) ∩ (A - C)

lemma Diff_Int:

      A - B ∩ C = A - B ∪ (A - C)

lemma Un_Diff:

      A ∪ B - C = A - C ∪ (B - C)

lemma Int_Diff:

      A ∩ B - C = A ∩ (B - C)

lemma Diff_Int_distrib:

      C ∩ (A - B) = C ∩ A - C ∩ B

lemma Diff_Int_distrib2:

      (A - B) ∩ C = A ∩ C - B ∩ C

lemma Diff_Compl:

      A - - B = A ∩ B

lemma Compl_Diff_eq:

      - (A - B) = - A ∪ B

lemma all_bool_eq:

      (∀b. P b) = (P True ∧ P False)

lemma bool_induct:

      [| P True; P False |] ==> P x

lemma ex_bool_eq:

      (∃b. P b) = (P True ∨ P False)

lemma Un_eq_UN:

      A ∪ B = (UN b. if b then A else B)

lemma UN_bool_eq:

      (UN b. A b) = A True ∪ A False

lemma INT_bool_eq:

      (INT b. A b) = A True ∩ A False

lemma Pow_empty:

      Pow {} = {{}}

lemma Pow_insert:

      Pow (insert a A) = Pow A ∪ insert a ` Pow A

lemma Pow_Compl:

      Pow (- A) = {- B |B. A ∈ Pow B}

lemma Pow_UNIV:

      Pow UNIV = UNIV

lemma Un_Pow_subset:

      Pow A ∪ Pow B ⊆ Pow (A ∪ B)

lemma UN_Pow_subset:

      (UN x:A. Pow (B x)) ⊆ Pow (UN x:A. B x)

lemma subset_Pow_Union:

      A ⊆ Pow (Union A)

lemma Union_Pow_eq:

      Union (Pow A) = A

lemma Pow_Int_eq:

      Pow (A ∩ B) = Pow A ∩ Pow B

lemma Pow_INT_eq:

      Pow (INT x:A. B x) = (INT x:A. Pow (B x))

lemma set_eq_subset:

      (A = B) = (A ⊆ B ∧ B ⊆ A)

lemma subset_iff:

      (A ⊆ B) = (∀t. t ∈ A --> t ∈ B)

lemma subset_iff_psubset_eq:

      (A ⊆ B) = (A ⊂ B ∨ A = B)

lemma all_not_in_conv:

      (∀x. x ∉ A) = (A = {})

lemma ex_in_conv:

      (∃x. x ∈ A) = (A ≠ {})

lemma distinct_lemma:

      f x ≠ f y ==> x ≠ y

lemma UN_simps:

      (UN x:C. insert a (B x)) = (if C = {} then {} else insert a (UN x:C. B x))

      (UN x:C. A x ∪ B) = (if C = {} then {} else (UN x:C. A x) ∪ B)

      (UN x:C. A ∪ B x) = (if C = {} then {} else A ∪ (UN x:C. B x))

      (UN x:C. A x ∩ B) = (UN x:C. A x) ∩ B

      (UN x:C. A ∩ B x) = A ∩ (UN x:C. B x)

      (UN x:C. A x - B) = (UN x:C. A x) - B

      (UN x:C. A - B x) = A - (INT x:C. B x)

      (UN x:Union A. B x) = (UN y:A. UN x:y. B x)

      (UN z:UNION A B. C z) = (UN x:A. UN z:B x. C z)

      (UN x:f ` A. B x) = (UN a:A. B (f a))

lemma INT_simps:

      (INT x:C. A x ∩ B) = (if C = {} then UNIV else (INT x:C. A x) ∩ B)

      (INT x:C. A ∩ B x) = (if C = {} then UNIV else A ∩ (INT x:C. B x))

      (INT x:C. A x - B) = (if C = {} then UNIV else (INT x:C. A x) - B)

      (INT x:C. A - B x) = (if C = {} then UNIV else A - (UN x:C. B x))

      (INT x:C. insert a (B x)) = insert a (INT x:C. B x)

      (INT x:C. A x ∪ B) = (INT x:C. A x) ∪ B

      (INT x:C. A ∪ B x) = A ∪ (INT x:C. B x)

      (INT x:Union A. B x) = (INT y:A. INT x:y. B x)

      (INT z:UNION A B. C z) = (INT x:A. INT z:B x. C z)

      (INT x:f ` A. B x) = (INT a:A. B (f a))

lemma ball_simps:

      (∀x∈A. P x ∨ Q) = ((∀x∈A. P x) ∨ Q)

      (∀x∈A. P ∨ Q x) = (P ∨ (∀x∈A. Q x))

      (∀x∈A. P --> Q x) = (P --> (∀x∈A. Q x))

      (∀x∈A. P x --> Q) = ((∃x∈A. P x) --> Q)

      (∀x∈{}. P x) = True

      (∀x∈UNIV. P x) = (∀x. P x)

      (∀x∈insert a B. P x) = (P a ∧ (∀x∈B. P x))

      (∀x∈Union A. P x) = (∀y∈A. ∀x∈y. P x)

      (∀x∈UNION A B. P x) = (∀a∈A. ∀x∈B a. P x)

      (∀x∈Collect Q. P x) = (∀x. Q x --> P x)

      (∀x∈f ` A. P x) = (∀x∈A. P (f x))

      (¬ (∀x∈A. P x)) = (∃x∈A. ¬ P x)

lemma bex_simps:

      (∃x∈A. P x ∧ Q) = ((∃x∈A. P x) ∧ Q)

      (∃x∈A. P ∧ Q x) = (P ∧ (∃x∈A. Q x))

      (∃x∈{}. P x) = False

      (∃x∈UNIV. P x) = (∃x. P x)

      (∃x∈insert a B. P x) = (P a ∨ (∃x∈B. P x))

      (∃x∈Union A. P x) = (∃y∈A. ∃x∈y. P x)

      (∃x∈UNION A B. P x) = (∃a∈A. ∃x∈B a. P x)

      (∃x∈Collect Q. P x) = (∃x. Q x ∧ P x)

      (∃x∈f ` A. P x) = (∃x∈A. P (f x))

      (¬ (∃x∈A. P x)) = (∀x∈A. ¬ P x)

lemma ball_conj_distrib:

      (∀x∈A. P x ∧ Q x) = ((∀x∈A. P x) ∧ (∀x∈A. Q x))

lemma bex_disj_distrib:

      (∃x∈A. P x ∨ Q x) = ((∃x∈A. P x) ∨ (∃x∈A. Q x))

lemma UN_extend_simps:

      insert a (UN x:C. B x) = (if C = {} then {a} else UN x:C. insert a (B x))

      (UN x:C. A x) ∪ B = (if C = {} then B else UN x:C. A x ∪ B)

      A ∪ (UN x:C. B x) = (if C = {} then A else UN x:C. A ∪ B x)

      (UN x:C. A x) ∩ B = (UN x:C. A x ∩ B)

      A ∩ (UN x:C. B x) = (UN x:C. A ∩ B x)

      (UN x:C. A x) - B = (UN x:C. A x - B)

      A - (INT x:C. B x) = (UN x:C. A - B x)

      (UN y:A. UN x:y. B x) = (UN x:Union A. B x)

      (UN x:A. UN z:B x. C z) = (UN z:UNION A B. C z)

      (UN a:A. B (f a)) = (UN x:f ` A. B x)

lemma INT_extend_simps:

      (INT x:C. A x) ∩ B = (if C = {} then B else INT x:C. A x ∩ B)

      A ∩ (INT x:C. B x) = (if C = {} then A else INT x:C. A ∩ B x)

      (INT x:C. A x) - B = (if C = {} then UNIV - B else INT x:C. A x - B)

      A - (UN x:C. B x) = (if C = {} then A else INT x:C. A - B x)

      insert a (INT x:C. B x) = (INT x:C. insert a (B x))

      (INT x:C. A x) ∪ B = (INT x:C. A x ∪ B)

      A ∪ (INT x:C. B x) = (INT x:C. A ∪ B x)

      (INT y:A. INT x:y. B x) = (INT x:Union A. B x)

      (INT x:A. INT z:B x. C z) = (INT z:UNION A B. C z)

      (INT a:A. B (f a)) = (INT x:f ` A. B x)

#### Monotonicity of various operations

lemma image_mono:

      A ⊆ B ==> f ` A ⊆ f ` B

lemma Pow_mono:

      A ⊆ B ==> Pow A ⊆ Pow B

lemma Union_mono:

      A ⊆ B ==> Union A ⊆ Union B

lemma Inter_anti_mono:

      B ⊆ A ==> Inter A ⊆ Inter B

lemma UN_mono:

      [| A ⊆ B; !!x. x ∈ A ==> f x ⊆ g x |] ==> (UN x:A. f x) ⊆ (UN x:B. g x)

lemma INT_anti_mono:

      [| B ⊆ A; !!x. x ∈ A ==> f x ⊆ g x |] ==> (INT x:A. f x) ⊆ (INT x:A. g x)

lemma insert_mono:

      C ⊆ D ==> insert a C ⊆ insert a D

lemma Un_mono:

      [| A ⊆ C; B ⊆ D |] ==> A ∪ B ⊆ C ∪ D

lemma Int_mono:

      [| A ⊆ C; B ⊆ D |] ==> A ∩ B ⊆ C ∩ D

lemma Diff_mono:

      [| A ⊆ C; D ⊆ B |] ==> A - B ⊆ C - D

lemma Compl_anti_mono:

      A ⊆ B ==> - B ⊆ - A

lemma in_mono:

      A ⊆ B ==> x ∈ A --> x ∈ B

lemma conj_mono:

      [| P1.0 --> Q1.0; P2.0 --> Q2.0 |] ==> P1.0 ∧ P2.0 --> Q1.0 ∧ Q2.0

lemma disj_mono:

      [| P1.0 --> Q1.0; P2.0 --> Q2.0 |] ==> P1.0 ∨ P2.0 --> Q1.0 ∨ Q2.0

lemma imp_mono:

      [| Q1.0 --> P1.0; P2.0 --> Q2.0 |] ==> (P1.0 --> P2.0) --> Q1.0 --> Q2.0

lemma imp_refl:

      P --> P

lemma ex_mono:

      (!!x. P x --> Q x) ==> (∃x. P x) --> (∃x. Q x)

lemma all_mono:

      (!!x. P x --> Q x) ==> (∀x. P x) --> (∀x. Q x)

lemma Collect_mono:

      (!!x. P x --> Q x) ==> Collect P ⊆ Collect Q

lemma Int_Collect_mono:

      [| A ⊆ B; !!x. x ∈ A ==> P x --> Q x |] ==> A ∩ Collect P ⊆ B ∩ Collect Q

lemmas basic_monos:

      A ⊆ A

      P --> P

      [| P1.0 --> Q1.0; P2.0 --> Q2.0 |] ==> P1.0 ∨ P2.0 --> Q1.0 ∨ Q2.0

      [| P1.0 --> Q1.0; P2.0 --> Q2.0 |] ==> P1.0 ∧ P2.0 --> Q1.0 ∧ Q2.0

      (!!x. P x --> Q x) ==> (∃x. P x) --> (∃x. Q x)

      (!!x. P x --> Q x) ==> Collect P ⊆ Collect Q

      A ⊆ B ==> x ∈ A --> x ∈ B

lemmas basic_monos:

      A ⊆ A

      P --> P

      [| P1.0 --> Q1.0; P2.0 --> Q2.0 |] ==> P1.0 ∨ P2.0 --> Q1.0 ∨ Q2.0

      [| P1.0 --> Q1.0; P2.0 --> Q2.0 |] ==> P1.0 ∧ P2.0 --> Q1.0 ∧ Q2.0

      (!!x. P x --> Q x) ==> (∃x. P x) --> (∃x. Q x)

      (!!x. P x --> Q x) ==> Collect P ⊆ Collect Q

      A ⊆ B ==> x ∈ A --> x ∈ B

lemma eq_to_mono:

      [| a = b; c = d; b --> d |] ==> a --> c

lemma eq_to_mono2:

      [| a = b; c = d; ¬ b --> ¬ d |] ==> ¬ a --> ¬ c

lemma Least_mono:

      [| mono f; ∃x∈S. ∀y∈S. x ≤ y |] ==> (LEAST y. y ∈ f ` S) = f (LEAST x. x ∈ S)

### Inverse image of a function

#### Basic rules

lemma vimage_eq:

      (a ∈ f -` B) = (f a ∈ B)

lemma vimage_singleton_eq:

      (a ∈ f -` {b}) = (f a = b)

lemma vimageI:

      [| f a = b; b ∈ B |] ==> a ∈ f -` B

lemma vimageI2:

      f a ∈ A ==> a ∈ f -` A

lemma vimageE:

      [| a ∈ f -` B; !!x. [| f a = x; x ∈ B |] ==> P |] ==> P

lemma vimageD:

      a ∈ f -` A ==> f a ∈ A

#### Equations

lemma vimage_empty:

      f -` {} = {}

lemma vimage_Compl:

      f -` (- A) = - f -` A

lemma vimage_Un:

      f -` (A ∪ B) = f -` A ∪ f -` B

lemma vimage_Int:

      f -` (A ∩ B) = f -` A ∩ f -` B

lemma vimage_Union:

      f -` Union A = (UN X:A. f -` X)

lemma vimage_UN:

      f -` (UN x:A. B x) = (UN x:A. f -` B x)

lemma vimage_INT:

      f -` (INT x:A. B x) = (INT x:A. f -` B x)

lemma vimage_Collect_eq:

      f -` Collect P = {y. P (f y)}

lemma vimage_Collect:

      (!!x. P (f x) = Q x) ==> f -` Collect P = Collect Q

lemma vimage_insert:

      f -` insert a B = f -` {a} ∪ f -` B

lemma vimage_Diff:

      f -` (A - B) = f -` A - f -` B

lemma vimage_UNIV:

      f -` UNIV = UNIV

lemma vimage_eq_UN:

      f -` B = (UN y:B. f -` {y})

lemma vimage_mono:

      A ⊆ B ==> f -` A ⊆ f -` B

### Getting the Contents of a Singleton Set

lemma contents_eq:

      contents {x} = x

### Transitivity rules for calculational reasoning

lemma set_rev_mp:

      [| x ∈ A; A ⊆ B |] ==> x ∈ B

lemma set_mp:

      [| A ⊆ B; x ∈ A |] ==> x ∈ B

lemma ord_le_eq_trans:

      [| a ≤ b; b = c |] ==> a ≤ c

lemma ord_eq_le_trans:

      [| a = b; b ≤ c |] ==> a ≤ c

lemma ord_less_eq_trans:

      [| a < b; b = c |] ==> a < c

lemma ord_eq_less_trans:

      [| a = b; b < c |] ==> a < c

lemma order_less_subst2:

      [| a < b; f b < c; !!x y. x < y ==> f x < f y |] ==> f a < c

lemma order_less_subst1:

      [| a < f b; b < c; !!x y. x < y ==> f x < f y |] ==> a < f c

lemma order_le_less_subst2:

      [| a ≤ b; f b < c; !!x y. x ≤ y ==> f x ≤ f y |] ==> f a < c

lemma order_le_less_subst1:

      [| a ≤ f b; b < c; !!x y. x < y ==> f x < f y |] ==> a < f c

lemma order_less_le_subst2:

      [| a < b; f b ≤ c; !!x y. x < y ==> f x < f y |] ==> f a < c

lemma order_less_le_subst1:

      [| a < f b; b ≤ c; !!x y. x ≤ y ==> f x ≤ f y |] ==> a < f c

lemma order_subst1:

      [| a ≤ f b; b ≤ c; !!x y. x ≤ y ==> f x ≤ f y |] ==> a ≤ f c

lemma order_subst2:

      [| a ≤ b; f b ≤ c; !!x y. x ≤ y ==> f x ≤ f y |] ==> f a ≤ c

lemma ord_le_eq_subst:

      [| a ≤ b; f b = c; !!x y. x ≤ y ==> f x ≤ f y |] ==> f a ≤ c

lemma ord_eq_le_subst:

      [| a = f b; b ≤ c; !!x y. x ≤ y ==> f x ≤ f y |] ==> a ≤ f c

lemma ord_less_eq_subst:

      [| a < b; f b = c; !!x y. x < y ==> f x < f y |] ==> f a < c

lemma ord_eq_less_subst:

      [| a = f b; b < c; !!x y. x < y ==> f x < f y |] ==> a < f c

lemmas basic_trans_rules:

      [| a < b; f b < c; !!x y. x < y ==> f x < f y |] ==> f a < c

      [| a < f b; b < c; !!x y. x < y ==> f x < f y |] ==> a < f c

      [| a ≤ b; f b < c; !!x y. x ≤ y ==> f x ≤ f y |] ==> f a < c

      [| a ≤ f b; b < c; !!x y. x < y ==> f x < f y |] ==> a < f c

      [| a < b; f b ≤ c; !!x y. x < y ==> f x < f y |] ==> f a < c

      [| a < f b; b ≤ c; !!x y. x ≤ y ==> f x ≤ f y |] ==> a < f c

      [| a ≤ b; f b ≤ c; !!x y. x ≤ y ==> f x ≤ f y |] ==> f a ≤ c

      [| a ≤ f b; b ≤ c; !!x y. x ≤ y ==> f x ≤ f y |] ==> a ≤ f c

      [| a ≤ b; f b = c; !!x y. x ≤ y ==> f x ≤ f y |] ==> f a ≤ c

      [| a = f b; b ≤ c; !!x y. x ≤ y ==> f x ≤ f y |] ==> a ≤ f c

      [| a < b; f b = c; !!x y. x < y ==> f x < f y |] ==> f a < c

      [| a = f b; b < c; !!x y. x < y ==> f x < f y |] ==> a < f c

      [| a = b; P b |] ==> P a

      [| P a; a = b |] ==> P b

      [| P; P --> Q |] ==> Q

      [| P --> Q; P |] ==> Q

      [| x ∈ A; A ⊆ B |] ==> x ∈ B

      [| A ⊆ B; x ∈ A |] ==> x ∈ B

      [| a ≠ b; a ≤ b |] ==> a < b

      [| a ≤ b; a ≠ b |] ==> a < b

      [| x < y; y < z |] ==> x < z

      [| a < b; b < a |] ==> P

      [| x ≤ y; y < z |] ==> x < z

      [| x < y; y ≤ z |] ==> x < z

      [| x ≤ y; y ≤ z |] ==> x ≤ z

      [| x ≤ y; y ≤ x |] ==> x = y

      [| a ≤ b; b = c |] ==> a ≤ c

      [| a = b; b ≤ c |] ==> a ≤ c

      [| a < b; b = c |] ==> a < c

      [| a = b; b < c |] ==> a < c

      [| r = s; s = t |] ==> r = t

lemmas basic_trans_rules:

      [| a < b; f b < c; !!x y. x < y ==> f x < f y |] ==> f a < c

      [| a < f b; b < c; !!x y. x < y ==> f x < f y |] ==> a < f c

      [| a ≤ b; f b < c; !!x y. x ≤ y ==> f x ≤ f y |] ==> f a < c

      [| a ≤ f b; b < c; !!x y. x < y ==> f x < f y |] ==> a < f c

      [| a < b; f b ≤ c; !!x y. x < y ==> f x < f y |] ==> f a < c

      [| a < f b; b ≤ c; !!x y. x ≤ y ==> f x ≤ f y |] ==> a < f c

      [| a ≤ b; f b ≤ c; !!x y. x ≤ y ==> f x ≤ f y |] ==> f a ≤ c

      [| a ≤ f b; b ≤ c; !!x y. x ≤ y ==> f x ≤ f y |] ==> a ≤ f c

      [| a ≤ b; f b = c; !!x y. x ≤ y ==> f x ≤ f y |] ==> f a ≤ c

      [| a = f b; b ≤ c; !!x y. x ≤ y ==> f x ≤ f y |] ==> a ≤ f c

      [| a < b; f b = c; !!x y. x < y ==> f x < f y |] ==> f a < c

      [| a = f b; b < c; !!x y. x < y ==> f x < f y |] ==> a < f c

      [| a = b; P b |] ==> P a

      [| P a; a = b |] ==> P b

      [| P; P --> Q |] ==> Q

      [| P --> Q; P |] ==> Q

      [| x ∈ A; A ⊆ B |] ==> x ∈ B

      [| A ⊆ B; x ∈ A |] ==> x ∈ B

      [| a ≠ b; a ≤ b |] ==> a < b

      [| a ≤ b; a ≠ b |] ==> a < b

      [| x < y; y < z |] ==> x < z

      [| a < b; b < a |] ==> P

      [| x ≤ y; y < z |] ==> x < z

      [| x < y; y ≤ z |] ==> x < z

      [| x ≤ y; y ≤ z |] ==> x ≤ z

      [| x ≤ y; y ≤ x |] ==> x = y

      [| a ≤ b; b = c |] ==> a ≤ c

      [| a = b; b ≤ c |] ==> a ≤ c

      [| a < b; b = c |] ==> a < c

      [| a = b; b < c |] ==> a < c

      [| r = s; s = t |] ==> r = t