Theory Orderings

theory Orderings
imports HOL
(*  Title:      HOL/Orderings.thy
    Author:     Tobias Nipkow, Markus Wenzel, and Larry Paulson
*)

section ‹Abstract orderings›

theory Orderings
imports HOL
keywords "print_orders" :: diag
begin

ML_file "~~/src/Provers/order.ML"
ML_file "~~/src/Provers/quasi.ML"  (* FIXME unused? *)

subsection ‹Abstract ordering›

locale ordering =
  fixes less_eq :: "'a ⇒ 'a ⇒ bool" (infix "" 50)
   and less :: "'a ⇒ 'a ⇒ bool" (infix "<" 50)
  assumes strict_iff_order: "a < b ⟷ a  b ∧ a ≠ b"
  assumes refl: "a  a"  ‹not ‹iff›: makes problems due to multiple (dual) interpretations›
    and antisym: "a  b ⟹ b  a ⟹ a = b"
    and trans: "a  b ⟹ b  c ⟹ a  c"
begin

lemma strict_implies_order:
  "a < b ⟹ a  b"
  by (simp add: strict_iff_order)

lemma strict_implies_not_eq:
  "a < b ⟹ a ≠ b"
  by (simp add: strict_iff_order)

lemma not_eq_order_implies_strict:
  "a ≠ b ⟹ a  b ⟹ a < b"
  by (simp add: strict_iff_order)

lemma order_iff_strict:
  "a  b ⟷ a < b ∨ a = b"
  by (auto simp add: strict_iff_order refl)

lemma irrefl:  ‹not ‹iff›: makes problems due to multiple (dual) interpretations›
  "¬ a < a"
  by (simp add: strict_iff_order)

lemma asym:
  "a < b ⟹ b < a ⟹ False"
  by (auto simp add: strict_iff_order intro: antisym)

lemma strict_trans1:
  "a  b ⟹ b < c ⟹ a < c"
  by (auto simp add: strict_iff_order intro: trans antisym)

lemma strict_trans2:
  "a < b ⟹ b  c ⟹ a < c"
  by (auto simp add: strict_iff_order intro: trans antisym)

lemma strict_trans:
  "a < b ⟹ b < c ⟹ a < c"
  by (auto intro: strict_trans1 strict_implies_order)

end

text ‹Alternative introduction rule with bias towards strict order›

lemma ordering_strictI:
  fixes less_eq (infix "" 50)
    and less (infix "<" 50)
  assumes less_eq_less: "⋀a b. a  b ⟷ a < b ∨ a = b"
    assumes asym: "⋀a b. a < b ⟹ ¬ b < a"
  assumes irrefl: "⋀a. ¬ a < a"
  assumes trans: "⋀a b c. a < b ⟹ b < c ⟹ a < c"
  shows "ordering less_eq less"
proof
  fix a b
  show "a < b ⟷ a  b ∧ a ≠ b"
    by (auto simp add: less_eq_less asym irrefl)
next
  fix a
  show "a  a"
    by (auto simp add: less_eq_less)
next
  fix a b c
  assume "a  b" and "b  c" then show "a  c"
    by (auto simp add: less_eq_less intro: trans)
next
  fix a b
  assume "a  b" and "b  a" then show "a = b"
    by (auto simp add: less_eq_less asym)
qed

lemma ordering_dualI:
  fixes less_eq (infix "" 50)
    and less (infix "<" 50)
  assumes "ordering (λa b. b  a) (λa b. b < a)"
  shows "ordering less_eq less"
proof -
  from assms interpret ordering "λa b. b  a" "λa b. b < a" .
  show ?thesis
    by standard (auto simp: strict_iff_order refl intro: antisym trans)
qed

locale ordering_top = ordering +
  fixes top :: "'a"  ("")
  assumes extremum [simp]: "a  "
begin

lemma extremum_uniqueI:
  "  a ⟹ a = "
  by (rule antisym) auto

lemma extremum_unique:
  "  a ⟷ a = "
  by (auto intro: antisym)

lemma extremum_strict [simp]:
  "¬ ( < a)"
  using extremum [of a] by (auto simp add: order_iff_strict intro: asym irrefl)

lemma not_eq_extremum:
  "a ≠  ⟷ a < "
  by (auto simp add: order_iff_strict intro: not_eq_order_implies_strict extremum)

end


subsection ‹Syntactic orders›

class ord =
  fixes less_eq :: "'a ⇒ 'a ⇒ bool"
    and less :: "'a ⇒ 'a ⇒ bool"
begin

notation
  less_eq  ("op ≤") and
  less_eq  ("(_/ ≤ _)"  [51, 51] 50) and
  less  ("op <") and
  less  ("(_/ < _)"  [51, 51] 50)

abbreviation (input)
  greater_eq  (infix "≥" 50)
  where "x ≥ y ≡ y ≤ x"

abbreviation (input)
  greater  (infix ">" 50)
  where "x > y ≡ y < x"

notation (ASCII)
  less_eq  ("op <=") and
  less_eq  ("(_/ <= _)" [51, 51] 50)

notation (input)
  greater_eq  (infix ">=" 50)

end


subsection ‹Quasi orders›

class preorder = ord +
  assumes less_le_not_le: "x < y ⟷ x ≤ y ∧ ¬ (y ≤ x)"
  and order_refl [iff]: "x ≤ x"
  and order_trans: "x ≤ y ⟹ y ≤ z ⟹ x ≤ z"
begin

text ‹Reflexivity.›

lemma eq_refl: "x = y ⟹ x ≤ y"
     ‹This form is useful with the classical reasoner.›
by (erule ssubst) (rule order_refl)

lemma less_irrefl [iff]: "¬ x < x"
by (simp add: less_le_not_le)

lemma less_imp_le: "x < y ⟹ x ≤ y"
by (simp add: less_le_not_le)


text ‹Asymmetry.›

lemma less_not_sym: "x < y ⟹ ¬ (y < x)"
by (simp add: less_le_not_le)

lemma less_asym: "x < y ⟹ (¬ P ⟹ y < x) ⟹ P"
by (drule less_not_sym, erule contrapos_np) simp


text ‹Transitivity.›

lemma less_trans: "x < y ⟹ y < z ⟹ x < z"
by (auto simp add: less_le_not_le intro: order_trans)

lemma le_less_trans: "x ≤ y ⟹ y < z ⟹ x < z"
by (auto simp add: less_le_not_le intro: order_trans)

lemma less_le_trans: "x < y ⟹ y ≤ z ⟹ x < z"
by (auto simp add: less_le_not_le intro: order_trans)


text ‹Useful for simplification, but too risky to include by default.›

lemma less_imp_not_less: "x < y ⟹ (¬ y < x) ⟷ True"
by (blast elim: less_asym)

lemma less_imp_triv: "x < y ⟹ (y < x ⟶ P) ⟷ True"
by (blast elim: less_asym)


text ‹Transitivity rules for calculational reasoning›

lemma less_asym': "a < b ⟹ b < a ⟹ P"
by (rule less_asym)


text ‹Dual order›

lemma dual_preorder:
  "class.preorder (op ≥) (op >)"
  by standard (auto simp add: less_le_not_le intro: order_trans)

end


subsection ‹Partial orders›

class order = preorder +
  assumes antisym: "x ≤ y ⟹ y ≤ x ⟹ x = y"
begin

lemma less_le: "x < y ⟷ x ≤ y ∧ x ≠ y"
  by (auto simp add: less_le_not_le intro: antisym)

sublocale order: ordering less_eq less + dual_order: ordering greater_eq greater
proof -
  interpret ordering less_eq less
    by standard (auto intro: antisym order_trans simp add: less_le)
  show "ordering less_eq less"
    by (fact ordering_axioms)
  then show "ordering greater_eq greater"
    by (rule ordering_dualI)
qed

text ‹Reflexivity.›

lemma le_less: "x ≤ y ⟷ x < y ∨ x = y"
     ‹NOT suitable for iff, since it can cause PROOF FAILED.›
by (fact order.order_iff_strict)

lemma le_imp_less_or_eq: "x ≤ y ⟹ x < y ∨ x = y"
by (simp add: less_le)


text ‹Useful for simplification, but too risky to include by default.›

lemma less_imp_not_eq: "x < y ⟹ (x = y) ⟷ False"
by auto

lemma less_imp_not_eq2: "x < y ⟹ (y = x) ⟷ False"
by auto


text ‹Transitivity rules for calculational reasoning›

lemma neq_le_trans: "a ≠ b ⟹ a ≤ b ⟹ a < b"
by (fact order.not_eq_order_implies_strict)

lemma le_neq_trans: "a ≤ b ⟹ a ≠ b ⟹ a < b"
by (rule order.not_eq_order_implies_strict)


text ‹Asymmetry.›

lemma eq_iff: "x = y ⟷ x ≤ y ∧ y ≤ x"
by (blast intro: antisym)

lemma antisym_conv: "y ≤ x ⟹ x ≤ y ⟷ x = y"
by (blast intro: antisym)

lemma less_imp_neq: "x < y ⟹ x ≠ y"
by (fact order.strict_implies_not_eq)


text ‹Least value operator›

definition (in ord)
  Least :: "('a ⇒ bool) ⇒ 'a" (binder "LEAST " 10) where
  "Least P = (THE x. P x ∧ (∀y. P y ⟶ x ≤ y))"

lemma Least_equality:
  assumes "P x"
    and "⋀y. P y ⟹ x ≤ y"
  shows "Least P = x"
unfolding Least_def by (rule the_equality)
  (blast intro: assms antisym)+

lemma LeastI2_order:
  assumes "P x"
    and "⋀y. P y ⟹ x ≤ y"
    and "⋀x. P x ⟹ ∀y. P y ⟶ x ≤ y ⟹ Q x"
  shows "Q (Least P)"
unfolding Least_def by (rule theI2)
  (blast intro: assms antisym)+

text ‹Greatest value operator›

definition Greatest :: "('a ⇒ bool) ⇒ 'a" (binder "GREATEST " 10) where
"Greatest P = (THE x. P x ∧ (∀y. P y ⟶ x ≥ y))"

lemma GreatestI2_order:
  "⟦ P x;
    ⋀y. P y ⟹ x ≥ y;
    ⋀x. ⟦ P x; ∀y. P y ⟶ x ≥ y ⟧ ⟹ Q x ⟧
  ⟹ Q (Greatest P)"
unfolding Greatest_def
by (rule theI2) (blast intro: antisym)+

lemma Greatest_equality:
  "⟦ P x;  ⋀y. P y ⟹ x ≥ y ⟧ ⟹ Greatest P = x"
unfolding Greatest_def
by (rule the_equality) (blast intro: antisym)+

end

lemma ordering_orderI:
  fixes less_eq (infix "" 50)
    and less (infix "<" 50)
  assumes "ordering less_eq less"
  shows "class.order less_eq less"
proof -
  from assms interpret ordering less_eq less .
  show ?thesis
    by standard (auto intro: antisym trans simp add: refl strict_iff_order)
qed

lemma order_strictI:
  fixes less (infix "⊏" 50)
    and less_eq (infix "⊑" 50)
  assumes "⋀a b. a ⊑ b ⟷ a ⊏ b ∨ a = b"
    assumes "⋀a b. a ⊏ b ⟹ ¬ b ⊏ a"
  assumes "⋀a. ¬ a ⊏ a"
  assumes "⋀a b c. a ⊏ b ⟹ b ⊏ c ⟹ a ⊏ c"
  shows "class.order less_eq less"
  by (rule ordering_orderI) (rule ordering_strictI, (fact assms)+)

context order
begin

text ‹Dual order›

lemma dual_order:
  "class.order (op ≥) (op >)"
  using dual_order.ordering_axioms by (rule ordering_orderI)

end


subsection ‹Linear (total) orders›

class linorder = order +
  assumes linear: "x ≤ y ∨ y ≤ x"
begin

lemma less_linear: "x < y ∨ x = y ∨ y < x"
unfolding less_le using less_le linear by blast

lemma le_less_linear: "x ≤ y ∨ y < x"
by (simp add: le_less less_linear)

lemma le_cases [case_names le ge]:
  "(x ≤ y ⟹ P) ⟹ (y ≤ x ⟹ P) ⟹ P"
using linear by blast

lemma (in linorder) le_cases3:
  "⟦⟦x ≤ y; y ≤ z⟧ ⟹ P; ⟦y ≤ x; x ≤ z⟧ ⟹ P; ⟦x ≤ z; z ≤ y⟧ ⟹ P;
    ⟦z ≤ y; y ≤ x⟧ ⟹ P; ⟦y ≤ z; z ≤ x⟧ ⟹ P; ⟦z ≤ x; x ≤ y⟧ ⟹ P⟧ ⟹ P"
by (blast intro: le_cases)

lemma linorder_cases [case_names less equal greater]:
  "(x < y ⟹ P) ⟹ (x = y ⟹ P) ⟹ (y < x ⟹ P) ⟹ P"
using less_linear by blast

lemma linorder_wlog[case_names le sym]:
  "(⋀a b. a ≤ b ⟹ P a b) ⟹ (⋀a b. P b a ⟹ P a b) ⟹ P a b"
  by (cases rule: le_cases[of a b]) blast+

lemma not_less: "¬ x < y ⟷ y ≤ x"
apply (simp add: less_le)
using linear apply (blast intro: antisym)
done

lemma not_less_iff_gr_or_eq:
 "¬(x < y) ⟷ (x > y | x = y)"
apply(simp add:not_less le_less)
apply blast
done

lemma not_le: "¬ x ≤ y ⟷ y < x"
apply (simp add: less_le)
using linear apply (blast intro: antisym)
done

lemma neq_iff: "x ≠ y ⟷ x < y ∨ y < x"
by (cut_tac x = x and y = y in less_linear, auto)

lemma neqE: "x ≠ y ⟹ (x < y ⟹ R) ⟹ (y < x ⟹ R) ⟹ R"
by (simp add: neq_iff) blast

lemma antisym_conv1: "¬ x < y ⟹ x ≤ y ⟷ x = y"
by (blast intro: antisym dest: not_less [THEN iffD1])

lemma antisym_conv2: "x ≤ y ⟹ ¬ x < y ⟷ x = y"
by (blast intro: antisym dest: not_less [THEN iffD1])

lemma antisym_conv3: "¬ y < x ⟹ ¬ x < y ⟷ x = y"
by (blast intro: antisym dest: not_less [THEN iffD1])

lemma leI: "¬ x < y ⟹ y ≤ x"
unfolding not_less .

lemma leD: "y ≤ x ⟹ ¬ x < y"
unfolding not_less .

lemma not_le_imp_less: "¬ y ≤ x ⟹ x < y"
unfolding not_le .

lemma linorder_less_wlog[case_names less refl sym]:
     "⟦⋀a b. a < b ⟹ P a b;  ⋀a. P a a;  ⋀a b. P b a ⟹ P a b⟧ ⟹ P a b"
  using antisym_conv3 by blast

text ‹Dual order›

lemma dual_linorder:
  "class.linorder (op ≥) (op >)"
by (rule class.linorder.intro, rule dual_order) (unfold_locales, rule linear)

end


text ‹Alternative introduction rule with bias towards strict order›

lemma linorder_strictI:
  fixes less_eq (infix "" 50)
    and less (infix "<" 50)
  assumes "class.order less_eq less"
  assumes trichotomy: "⋀a b. a < b ∨ a = b ∨ b < a"
  shows "class.linorder less_eq less"
proof -
  interpret order less_eq less
    by (fact ‹class.order less_eq less›)
  show ?thesis
  proof
    fix a b
    show "a  b ∨ b  a"
      using trichotomy by (auto simp add: le_less)
  qed
qed


subsection ‹Reasoning tools setup›

ML ‹
signature ORDERS =
sig
  val print_structures: Proof.context -> unit
  val order_tac: Proof.context -> thm list -> int -> tactic
  val add_struct: string * term list -> string -> attribute
  val del_struct: string * term list -> attribute
end;

structure Orders: ORDERS =
struct

(* context data *)

fun struct_eq ((s1: string, ts1), (s2, ts2)) =
  s1 = s2 andalso eq_list (op aconv) (ts1, ts2);

structure Data = Generic_Data
(
  type T = ((string * term list) * Order_Tac.less_arith) list;
    (* Order structures:
       identifier of the structure, list of operations and record of theorems
       needed to set up the transitivity reasoner,
       identifier and operations identify the structure uniquely. *)
  val empty = [];
  val extend = I;
  fun merge data = AList.join struct_eq (K fst) data;
);

fun print_structures ctxt =
  let
    val structs = Data.get (Context.Proof ctxt);
    fun pretty_term t = Pretty.block
      [Pretty.quote (Syntax.pretty_term ctxt t), Pretty.brk 1,
        Pretty.str "::", Pretty.brk 1,
        Pretty.quote (Syntax.pretty_typ ctxt (type_of t))];
    fun pretty_struct ((s, ts), _) = Pretty.block
      [Pretty.str s, Pretty.str ":", Pretty.brk 1,
       Pretty.enclose "(" ")" (Pretty.breaks (map pretty_term ts))];
  in
    Pretty.writeln (Pretty.big_list "order structures:" (map pretty_struct structs))
  end;

val _ =
  Outer_Syntax.command @{command_keyword print_orders}
    "print order structures available to transitivity reasoner"
    (Scan.succeed (Toplevel.keep (print_structures o Toplevel.context_of)));


(* tactics *)

fun struct_tac ((s, ops), thms) ctxt facts =
  let
    val [eq, le, less] = ops;
    fun decomp thy (@{const Trueprop} $ t) =
          let
            fun excluded t =
              (* exclude numeric types: linear arithmetic subsumes transitivity *)
              let val T = type_of t
              in
                T = HOLogic.natT orelse T = HOLogic.intT orelse T = HOLogic.realT
              end;
            fun rel (bin_op $ t1 $ t2) =
                  if excluded t1 then NONE
                  else if Pattern.matches thy (eq, bin_op) then SOME (t1, "=", t2)
                  else if Pattern.matches thy (le, bin_op) then SOME (t1, "<=", t2)
                  else if Pattern.matches thy (less, bin_op) then SOME (t1, "<", t2)
                  else NONE
              | rel _ = NONE;
            fun dec (Const (@{const_name Not}, _) $ t) =
                  (case rel t of NONE =>
                    NONE
                  | SOME (t1, rel, t2) => SOME (t1, "~" ^ rel, t2))
              | dec x = rel x;
          in dec t end
      | decomp _ _ = NONE;
  in
    (case s of
      "order" => Order_Tac.partial_tac decomp thms ctxt facts
    | "linorder" => Order_Tac.linear_tac decomp thms ctxt facts
    | _ => error ("Unknown order kind " ^ quote s ^ " encountered in transitivity reasoner"))
  end

fun order_tac ctxt facts =
  FIRST' (map (fn s => CHANGED o struct_tac s ctxt facts) (Data.get (Context.Proof ctxt)));


(* attributes *)

fun add_struct s tag =
  Thm.declaration_attribute
    (fn thm => Data.map (AList.map_default struct_eq (s, Order_Tac.empty TrueI) (Order_Tac.update tag thm)));
fun del_struct s =
  Thm.declaration_attribute
    (fn _ => Data.map (AList.delete struct_eq s));

end;
›

attribute_setup order = ‹
  Scan.lift ((Args.add -- Args.name >> (fn (_, s) => SOME s) || Args.del >> K NONE) --|
    Args.colon (* FIXME || Scan.succeed true *) ) -- Scan.lift Args.name --
    Scan.repeat Args.term
    >> (fn ((SOME tag, n), ts) => Orders.add_struct (n, ts) tag
         | ((NONE, n), ts) => Orders.del_struct (n, ts))
› "theorems controlling transitivity reasoner"

method_setup order = ‹
  Scan.succeed (fn ctxt => SIMPLE_METHOD' (Orders.order_tac ctxt []))
› "transitivity reasoner"


text ‹Declarations to set up transitivity reasoner of partial and linear orders.›

context order
begin

(* The type constraint on @{term op =} below is necessary since the operation
   is not a parameter of the locale. *)

declare less_irrefl [THEN notE, order add less_reflE: order "op = :: 'a ⇒ 'a ⇒ bool" "op <=" "op <"]

declare order_refl  [order add le_refl: order "op = :: 'a => 'a => bool" "op <=" "op <"]

declare less_imp_le [order add less_imp_le: order "op = :: 'a => 'a => bool" "op <=" "op <"]

declare antisym [order add eqI: order "op = :: 'a => 'a => bool" "op <=" "op <"]

declare eq_refl [order add eqD1: order "op = :: 'a => 'a => bool" "op <=" "op <"]

declare sym [THEN eq_refl, order add eqD2: order "op = :: 'a => 'a => bool" "op <=" "op <"]

declare less_trans [order add less_trans: order "op = :: 'a => 'a => bool" "op <=" "op <"]

declare less_le_trans [order add less_le_trans: order "op = :: 'a => 'a => bool" "op <=" "op <"]

declare le_less_trans [order add le_less_trans: order "op = :: 'a => 'a => bool" "op <=" "op <"]

declare order_trans [order add le_trans: order "op = :: 'a => 'a => bool" "op <=" "op <"]

declare le_neq_trans [order add le_neq_trans: order "op = :: 'a => 'a => bool" "op <=" "op <"]

declare neq_le_trans [order add neq_le_trans: order "op = :: 'a => 'a => bool" "op <=" "op <"]

declare less_imp_neq [order add less_imp_neq: order "op = :: 'a => 'a => bool" "op <=" "op <"]

declare eq_neq_eq_imp_neq [order add eq_neq_eq_imp_neq: order "op = :: 'a => 'a => bool" "op <=" "op <"]

declare not_sym [order add not_sym: order "op = :: 'a => 'a => bool" "op <=" "op <"]

end

context linorder
begin

declare [[order del: order "op = :: 'a => 'a => bool" "op <=" "op <"]]

declare less_irrefl [THEN notE, order add less_reflE: linorder "op = :: 'a => 'a => bool" "op <=" "op <"]

declare order_refl [order add le_refl: linorder "op = :: 'a => 'a => bool" "op <=" "op <"]

declare less_imp_le [order add less_imp_le: linorder "op = :: 'a => 'a => bool" "op <=" "op <"]

declare not_less [THEN iffD2, order add not_lessI: linorder "op = :: 'a => 'a => bool" "op <=" "op <"]

declare not_le [THEN iffD2, order add not_leI: linorder "op = :: 'a => 'a => bool" "op <=" "op <"]

declare not_less [THEN iffD1, order add not_lessD: linorder "op = :: 'a => 'a => bool" "op <=" "op <"]

declare not_le [THEN iffD1, order add not_leD: linorder "op = :: 'a => 'a => bool" "op <=" "op <"]

declare antisym [order add eqI: linorder "op = :: 'a => 'a => bool" "op <=" "op <"]

declare eq_refl [order add eqD1: linorder "op = :: 'a => 'a => bool" "op <=" "op <"]

declare sym [THEN eq_refl, order add eqD2: linorder "op = :: 'a => 'a => bool" "op <=" "op <"]

declare less_trans [order add less_trans: linorder "op = :: 'a => 'a => bool" "op <=" "op <"]

declare less_le_trans [order add less_le_trans: linorder "op = :: 'a => 'a => bool" "op <=" "op <"]

declare le_less_trans [order add le_less_trans: linorder "op = :: 'a => 'a => bool" "op <=" "op <"]

declare order_trans [order add le_trans: linorder "op = :: 'a => 'a => bool" "op <=" "op <"]

declare le_neq_trans [order add le_neq_trans: linorder "op = :: 'a => 'a => bool" "op <=" "op <"]

declare neq_le_trans [order add neq_le_trans: linorder "op = :: 'a => 'a => bool" "op <=" "op <"]

declare less_imp_neq [order add less_imp_neq: linorder "op = :: 'a => 'a => bool" "op <=" "op <"]

declare eq_neq_eq_imp_neq [order add eq_neq_eq_imp_neq: linorder "op = :: 'a => 'a => bool" "op <=" "op <"]

declare not_sym [order add not_sym: linorder "op = :: 'a => 'a => bool" "op <=" "op <"]

end

setup ‹
  map_theory_simpset (fn ctxt0 => ctxt0 addSolver
    mk_solver "Transitivity" (fn ctxt => Orders.order_tac ctxt (Simplifier.prems_of ctxt)))
  (*Adding the transitivity reasoners also as safe solvers showed a slight
    speed up, but the reasoning strength appears to be not higher (at least
    no breaking of additional proofs in the entire HOL distribution, as
    of 5 March 2004, was observed).*)
›

ML ‹
local
  fun prp t thm = Thm.prop_of thm = t;  (* FIXME proper aconv!? *)
in

fun antisym_le_simproc ctxt ct =
  (case Thm.term_of ct of
    (le as Const (_, T)) $ r $ s =>
     (let
        val prems = Simplifier.prems_of ctxt;
        val less = Const (@{const_name less}, T);
        val t = HOLogic.mk_Trueprop(le $ s $ r);
      in
        (case find_first (prp t) prems of
          NONE =>
            let val t = HOLogic.mk_Trueprop(HOLogic.Not $ (less $ r $ s)) in
              (case find_first (prp t) prems of
                NONE => NONE
              | SOME thm => SOME(mk_meta_eq(thm RS @{thm linorder_class.antisym_conv1})))
             end
         | SOME thm => SOME (mk_meta_eq (thm RS @{thm order_class.antisym_conv})))
      end handle THM _ => NONE)
  | _ => NONE);

fun antisym_less_simproc ctxt ct =
  (case Thm.term_of ct of
    NotC $ ((less as Const(_,T)) $ r $ s) =>
     (let
       val prems = Simplifier.prems_of ctxt;
       val le = Const (@{const_name less_eq}, T);
       val t = HOLogic.mk_Trueprop(le $ r $ s);
      in
        (case find_first (prp t) prems of
          NONE =>
            let val t = HOLogic.mk_Trueprop (NotC $ (less $ s $ r)) in
              (case find_first (prp t) prems of
                NONE => NONE
              | SOME thm => SOME (mk_meta_eq(thm RS @{thm linorder_class.antisym_conv3})))
            end
        | SOME thm => SOME (mk_meta_eq (thm RS @{thm linorder_class.antisym_conv2})))
      end handle THM _ => NONE)
  | _ => NONE);

end;
›

simproc_setup antisym_le ("(x::'a::order) ≤ y") = "K antisym_le_simproc"
simproc_setup antisym_less ("¬ (x::'a::linorder) < y") = "K antisym_less_simproc"


subsection ‹Bounded quantifiers›

syntax (ASCII)
  "_All_less" :: "[idt, 'a, bool] => bool"    ("(3ALL _<_./ _)"  [0, 0, 10] 10)
  "_Ex_less" :: "[idt, 'a, bool] => bool"    ("(3EX _<_./ _)"  [0, 0, 10] 10)
  "_All_less_eq" :: "[idt, 'a, bool] => bool"    ("(3ALL _<=_./ _)" [0, 0, 10] 10)
  "_Ex_less_eq" :: "[idt, 'a, bool] => bool"    ("(3EX _<=_./ _)" [0, 0, 10] 10)

  "_All_greater" :: "[idt, 'a, bool] => bool"    ("(3ALL _>_./ _)"  [0, 0, 10] 10)
  "_Ex_greater" :: "[idt, 'a, bool] => bool"    ("(3EX _>_./ _)"  [0, 0, 10] 10)
  "_All_greater_eq" :: "[idt, 'a, bool] => bool"    ("(3ALL _>=_./ _)" [0, 0, 10] 10)
  "_Ex_greater_eq" :: "[idt, 'a, bool] => bool"    ("(3EX _>=_./ _)" [0, 0, 10] 10)

syntax
  "_All_less" :: "[idt, 'a, bool] => bool"    ("(3∀_<_./ _)"  [0, 0, 10] 10)
  "_Ex_less" :: "[idt, 'a, bool] => bool"    ("(3∃_<_./ _)"  [0, 0, 10] 10)
  "_All_less_eq" :: "[idt, 'a, bool] => bool"    ("(3∀_≤_./ _)" [0, 0, 10] 10)
  "_Ex_less_eq" :: "[idt, 'a, bool] => bool"    ("(3∃_≤_./ _)" [0, 0, 10] 10)

  "_All_greater" :: "[idt, 'a, bool] => bool"    ("(3∀_>_./ _)"  [0, 0, 10] 10)
  "_Ex_greater" :: "[idt, 'a, bool] => bool"    ("(3∃_>_./ _)"  [0, 0, 10] 10)
  "_All_greater_eq" :: "[idt, 'a, bool] => bool"    ("(3∀_≥_./ _)" [0, 0, 10] 10)
  "_Ex_greater_eq" :: "[idt, 'a, bool] => bool"    ("(3∃_≥_./ _)" [0, 0, 10] 10)

syntax (input)
  "_All_less" :: "[idt, 'a, bool] => bool"    ("(3! _<_./ _)"  [0, 0, 10] 10)
  "_Ex_less" :: "[idt, 'a, bool] => bool"    ("(3? _<_./ _)"  [0, 0, 10] 10)
  "_All_less_eq" :: "[idt, 'a, bool] => bool"    ("(3! _<=_./ _)" [0, 0, 10] 10)
  "_Ex_less_eq" :: "[idt, 'a, bool] => bool"    ("(3? _<=_./ _)" [0, 0, 10] 10)

translations
  "ALL x<y. P"   =>  "ALL x. x < y ⟶ P"
  "EX x<y. P"    =>  "EX x. x < y ∧ P"
  "ALL x<=y. P"  =>  "ALL x. x <= y ⟶ P"
  "EX x<=y. P"   =>  "EX x. x <= y ∧ P"
  "ALL x>y. P"   =>  "ALL x. x > y ⟶ P"
  "EX x>y. P"    =>  "EX x. x > y ∧ P"
  "ALL x>=y. P"  =>  "ALL x. x >= y ⟶ P"
  "EX x>=y. P"   =>  "EX x. x >= y ∧ P"

print_translation ‹
let
  val All_binder = Mixfix.binder_name @{const_syntax All};
  val Ex_binder = Mixfix.binder_name @{const_syntax Ex};
  val impl = @{const_syntax HOL.implies};
  val conj = @{const_syntax HOL.conj};
  val less = @{const_syntax less};
  val less_eq = @{const_syntax less_eq};

  val trans =
   [((All_binder, impl, less),
    (@{syntax_const "_All_less"}, @{syntax_const "_All_greater"})),
    ((All_binder, impl, less_eq),
    (@{syntax_const "_All_less_eq"}, @{syntax_const "_All_greater_eq"})),
    ((Ex_binder, conj, less),
    (@{syntax_const "_Ex_less"}, @{syntax_const "_Ex_greater"})),
    ((Ex_binder, conj, less_eq),
    (@{syntax_const "_Ex_less_eq"}, @{syntax_const "_Ex_greater_eq"}))];

  fun matches_bound v t =
    (case t of
      Const (@{syntax_const "_bound"}, _) $ Free (v', _) => v = v'
    | _ => false);
  fun contains_var v = Term.exists_subterm (fn Free (x, _) => x = v | _ => false);
  fun mk x c n P = Syntax.const c $ Syntax_Trans.mark_bound_body x $ n $ P;

  fun tr' q = (q, fn _ =>
    (fn [Const (@{syntax_const "_bound"}, _) $ Free (v, T),
        Const (c, _) $ (Const (d, _) $ t $ u) $ P] =>
        (case AList.lookup (op =) trans (q, c, d) of
          NONE => raise Match
        | SOME (l, g) =>
            if matches_bound v t andalso not (contains_var v u) then mk (v, T) l u P
            else if matches_bound v u andalso not (contains_var v t) then mk (v, T) g t P
            else raise Match)
      | _ => raise Match));
in [tr' All_binder, tr' Ex_binder] end
›


subsection ‹Transitivity reasoning›

context ord
begin

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)

end

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 (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 (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 (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 (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 (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 (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 [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

lemmas (in order) [trans] =
  neq_le_trans
  le_neq_trans

lemmas (in preorder) [trans] =
  less_trans
  less_asym'
  le_less_trans
  less_le_trans
  order_trans

lemmas (in order) [trans] =
  antisym

lemmas (in ord) [trans] =
  ord_le_eq_trans
  ord_eq_le_trans
  ord_less_eq_trans
  ord_eq_less_trans

lemmas [trans] =
  trans

lemmas order_trans_rules =
  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
  neq_le_trans
  le_neq_trans
  less_trans
  less_asym'
  le_less_trans
  less_le_trans
  order_trans
  antisym
  ord_le_eq_trans
  ord_eq_le_trans
  ord_less_eq_trans
  ord_eq_less_trans
  trans

text ‹These support proving chains of decreasing inequalities
    a >= b >= c ... in Isar proofs.›

lemma xt1 [no_atp]:
  "a = b ==> b > c ==> a > c"
  "a > b ==> b = c ==> a > c"
  "a = b ==> b >= c ==> a >= c"
  "a >= b ==> b = c ==> a >= c"
  "(x::'a::order) >= y ==> y >= x ==> x = y"
  "(x::'a::order) >= y ==> y >= z ==> x >= z"
  "(x::'a::order) > y ==> y >= z ==> x > z"
  "(x::'a::order) >= y ==> y > z ==> x > z"
  "(a::'a::order) > b ==> b > a ==> P"
  "(x::'a::order) > y ==> y > z ==> x > z"
  "(a::'a::order) >= b ==> a ~= b ==> a > b"
  "(a::'a::order) ~= b ==> a >= b ==> a > b"
  "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"
  by auto

lemma xt2 [no_atp]:
  "(a::'a::order) >= f b ==> b >= c ==> (!!x y. x >= y ==> f x >= f y) ==> a >= f c"
by (subgoal_tac "f b >= f c", force, force)

lemma xt3 [no_atp]: "(a::'a::order) >= b ==> (f b::'b::order) >= c ==>
    (!!x y. x >= y ==> f x >= f y) ==> f a >= c"
by (subgoal_tac "f a >= f b", force, force)

lemma xt4 [no_atp]: "(a::'a::order) > f b ==> (b::'b::order) >= c ==>
  (!!x y. x >= y ==> f x >= f y) ==> a > f c"
by (subgoal_tac "f b >= f c", force, force)

lemma xt5 [no_atp]: "(a::'a::order) > b ==> (f b::'b::order) >= c==>
    (!!x y. x > y ==> f x > f y) ==> f a > c"
by (subgoal_tac "f a > f b", force, force)

lemma xt6 [no_atp]: "(a::'a::order) >= f b ==> b > c ==>
    (!!x y. x > y ==> f x > f y) ==> a > f c"
by (subgoal_tac "f b > f c", force, force)

lemma xt7 [no_atp]: "(a::'a::order) >= b ==> (f b::'b::order) > c ==>
    (!!x y. x >= y ==> f x >= f y) ==> f a > c"
by (subgoal_tac "f a >= f b", force, force)

lemma xt8 [no_atp]: "(a::'a::order) > f b ==> (b::'b::order) > c ==>
    (!!x y. x > y ==> f x > f y) ==> a > f c"
by (subgoal_tac "f b > f c", force, force)

lemma xt9 [no_atp]: "(a::'a::order) > b ==> (f b::'b::order) > c ==>
    (!!x y. x > y ==> f x > f y) ==> f a > c"
by (subgoal_tac "f a > f b", force, force)

lemmas xtrans = xt1 xt2 xt3 xt4 xt5 xt6 xt7 xt8 xt9

(*
  Since "a >= b" abbreviates "b <= a", the abbreviation "..." stands
  for the wrong thing in an Isar proof.

  The extra transitivity rules can be used as follows:

lemma "(a::'a::order) > z"
proof -
  have "a >= b" (is "_ >= ?rhs")
    sorry
  also have "?rhs >= c" (is "_ >= ?rhs")
    sorry
  also (xtrans) have "?rhs = d" (is "_ = ?rhs")
    sorry
  also (xtrans) have "?rhs >= e" (is "_ >= ?rhs")
    sorry
  also (xtrans) have "?rhs > f" (is "_ > ?rhs")
    sorry
  also (xtrans) have "?rhs > z"
    sorry
  finally (xtrans) show ?thesis .
qed

  Alternatively, one can use "declare xtrans [trans]" and then
  leave out the "(xtrans)" above.
*)


subsection ‹Monotonicity›

context order
begin

definition mono :: "('a ⇒ 'b::order) ⇒ bool" where
  "mono f ⟷ (∀x y. x ≤ y ⟶ f x ≤ f y)"

lemma monoI [intro?]:
  fixes f :: "'a ⇒ 'b::order"
  shows "(⋀x y. x ≤ y ⟹ f x ≤ f y) ⟹ mono f"
  unfolding mono_def by iprover

lemma monoD [dest?]:
  fixes f :: "'a ⇒ 'b::order"
  shows "mono f ⟹ x ≤ y ⟹ f x ≤ f y"
  unfolding mono_def by iprover

lemma monoE:
  fixes f :: "'a ⇒ 'b::order"
  assumes "mono f"
  assumes "x ≤ y"
  obtains "f x ≤ f y"
proof
  from assms show "f x ≤ f y" by (simp add: mono_def)
qed

definition antimono :: "('a ⇒ 'b::order) ⇒ bool" where
  "antimono f ⟷ (∀x y. x ≤ y ⟶ f x ≥ f y)"

lemma antimonoI [intro?]:
  fixes f :: "'a ⇒ 'b::order"
  shows "(⋀x y. x ≤ y ⟹ f x ≥ f y) ⟹ antimono f"
  unfolding antimono_def by iprover

lemma antimonoD [dest?]:
  fixes f :: "'a ⇒ 'b::order"
  shows "antimono f ⟹ x ≤ y ⟹ f x ≥ f y"
  unfolding antimono_def by iprover

lemma antimonoE:
  fixes f :: "'a ⇒ 'b::order"
  assumes "antimono f"
  assumes "x ≤ y"
  obtains "f x ≥ f y"
proof
  from assms show "f x ≥ f y" by (simp add: antimono_def)
qed

definition strict_mono :: "('a ⇒ 'b::order) ⇒ bool" where
  "strict_mono f ⟷ (∀x y. x < y ⟶ f x < f y)"

lemma strict_monoI [intro?]:
  assumes "⋀x y. x < y ⟹ f x < f y"
  shows "strict_mono f"
  using assms unfolding strict_mono_def by auto

lemma strict_monoD [dest?]:
  "strict_mono f ⟹ x < y ⟹ f x < f y"
  unfolding strict_mono_def by auto

lemma strict_mono_mono [dest?]:
  assumes "strict_mono f"
  shows "mono f"
proof (rule monoI)
  fix x y
  assume "x ≤ y"
  show "f x ≤ f y"
  proof (cases "x = y")
    case True then show ?thesis by simp
  next
    case False with ‹x ≤ y› have "x < y" by simp
    with assms strict_monoD have "f x < f y" by auto
    then show ?thesis by simp
  qed
qed

end

context linorder
begin

lemma mono_invE:
  fixes f :: "'a ⇒ 'b::order"
  assumes "mono f"
  assumes "f x < f y"
  obtains "x ≤ y"
proof
  show "x ≤ y"
  proof (rule ccontr)
    assume "¬ x ≤ y"
    then have "y ≤ x" by simp
    with ‹mono f› obtain "f y ≤ f x" by (rule monoE)
    with ‹f x < f y› show False by simp
  qed
qed

lemma strict_mono_eq:
  assumes "strict_mono f"
  shows "f x = f y ⟷ x = y"
proof
  assume "f x = f y"
  show "x = y" proof (cases x y rule: linorder_cases)
    case less with assms strict_monoD have "f x < f y" by auto
    with ‹f x = f y› show ?thesis by simp
  next
    case equal then show ?thesis .
  next
    case greater with assms strict_monoD have "f y < f x" by auto
    with ‹f x = f y› show ?thesis by simp
  qed
qed simp

lemma strict_mono_less_eq:
  assumes "strict_mono f"
  shows "f x ≤ f y ⟷ x ≤ y"
proof
  assume "x ≤ y"
  with assms strict_mono_mono monoD show "f x ≤ f y" by auto
next
  assume "f x ≤ f y"
  show "x ≤ y" proof (rule ccontr)
    assume "¬ x ≤ y" then have "y < x" by simp
    with assms strict_monoD have "f y < f x" by auto
    with ‹f x ≤ f y› show False by simp
  qed
qed

lemma strict_mono_less:
  assumes "strict_mono f"
  shows "f x < f y ⟷ x < y"
  using assms
    by (auto simp add: less_le Orderings.less_le strict_mono_eq strict_mono_less_eq)

end


subsection ‹min and max -- fundamental›

definition (in ord) min :: "'a ⇒ 'a ⇒ 'a" where
  "min a b = (if a ≤ b then a else b)"

definition (in ord) max :: "'a ⇒ 'a ⇒ 'a" where
  "max a b = (if a ≤ b then b else a)"

lemma min_absorb1: "x ≤ y ⟹ min x y = x"
  by (simp add: min_def)

lemma max_absorb2: "x ≤ y ⟹ max x y = y"
  by (simp add: max_def)

lemma min_absorb2: "(y::'a::order) ≤ x ⟹ min x y = y"
  by (simp add:min_def)

lemma max_absorb1: "(y::'a::order) ≤ x ⟹ max x y = x"
  by (simp add: max_def)

lemma max_min_same [simp]:
  fixes x y :: "'a :: linorder"
  shows "max x (min x y) = x" "max (min x y) x = x" "max (min x y) y = y" "max y (min x y) = y"
by(auto simp add: max_def min_def)

subsection ‹(Unique) top and bottom elements›

class bot =
  fixes bot :: 'a ("⊥")

class order_bot = order + bot +
  assumes bot_least: "⊥ ≤ a"
begin

sublocale bot: ordering_top greater_eq greater bot
  by standard (fact bot_least)

lemma le_bot:
  "a ≤ ⊥ ⟹ a = ⊥"
  by (fact bot.extremum_uniqueI)

lemma bot_unique:
  "a ≤ ⊥ ⟷ a = ⊥"
  by (fact bot.extremum_unique)

lemma not_less_bot:
  "¬ a < ⊥"
  by (fact bot.extremum_strict)

lemma bot_less:
  "a ≠ ⊥ ⟷ ⊥ < a"
  by (fact bot.not_eq_extremum)

end

class top =
  fixes top :: 'a ("⊤")

class order_top = order + top +
  assumes top_greatest: "a ≤ ⊤"
begin

sublocale top: ordering_top less_eq less top
  by standard (fact top_greatest)

lemma top_le:
  "⊤ ≤ a ⟹ a = ⊤"
  by (fact top.extremum_uniqueI)

lemma top_unique:
  "⊤ ≤ a ⟷ a = ⊤"
  by (fact top.extremum_unique)

lemma not_top_less:
  "¬ ⊤ < a"
  by (fact top.extremum_strict)

lemma less_top:
  "a ≠ ⊤ ⟷ a < ⊤"
  by (fact top.not_eq_extremum)

end


subsection ‹Dense orders›

class dense_order = order +
  assumes dense: "x < y ⟹ (∃z. x < z ∧ z < y)"

class dense_linorder = linorder + dense_order
begin

lemma dense_le:
  fixes y z :: 'a
  assumes "⋀x. x < y ⟹ x ≤ z"
  shows "y ≤ z"
proof (rule ccontr)
  assume "¬ ?thesis"
  hence "z < y" by simp
  from dense[OF this]
  obtain x where "x < y" and "z < x" by safe
  moreover have "x ≤ z" using assms[OF ‹x < y›] .
  ultimately show False by auto
qed

lemma dense_le_bounded:
  fixes x y z :: 'a
  assumes "x < y"
  assumes *: "⋀w. ⟦ x < w ; w < y ⟧ ⟹ w ≤ z"
  shows "y ≤ z"
proof (rule dense_le)
  fix w assume "w < y"
  from dense[OF ‹x < y›] obtain u where "x < u" "u < y" by safe
  from linear[of u w]
  show "w ≤ z"
  proof (rule disjE)
    assume "u ≤ w"
    from less_le_trans[OF ‹x < u› ‹u ≤ w›] ‹w < y›
    show "w ≤ z" by (rule *)
  next
    assume "w ≤ u"
    from ‹w ≤ u› *[OF ‹x < u› ‹u < y›]
    show "w ≤ z" by (rule order_trans)
  qed
qed

lemma dense_ge:
  fixes y z :: 'a
  assumes "⋀x. z < x ⟹ y ≤ x"
  shows "y ≤ z"
proof (rule ccontr)
  assume "¬ ?thesis"
  hence "z < y" by simp
  from dense[OF this]
  obtain x where "x < y" and "z < x" by safe
  moreover have "y ≤ x" using assms[OF ‹z < x›] .
  ultimately show False by auto
qed

lemma dense_ge_bounded:
  fixes x y z :: 'a
  assumes "z < x"
  assumes *: "⋀w. ⟦ z < w ; w < x ⟧ ⟹ y ≤ w"
  shows "y ≤ z"
proof (rule dense_ge)
  fix w assume "z < w"
  from dense[OF ‹z < x›] obtain u where "z < u" "u < x" by safe
  from linear[of u w]
  show "y ≤ w"
  proof (rule disjE)
    assume "w ≤ u"
    from ‹z < w› le_less_trans[OF ‹w ≤ u› ‹u < x›]
    show "y ≤ w" by (rule *)
  next
    assume "u ≤ w"
    from *[OF ‹z < u› ‹u < x›] ‹u ≤ w›
    show "y ≤ w" by (rule order_trans)
  qed
qed

end

class no_top = order +
  assumes gt_ex: "∃y. x < y"

class no_bot = order +
  assumes lt_ex: "∃y. y < x"

class unbounded_dense_linorder = dense_linorder + no_top + no_bot


subsection ‹Wellorders›

class wellorder = linorder +
  assumes less_induct [case_names less]: "(⋀x. (⋀y. y < x ⟹ P y) ⟹ P x) ⟹ P a"
begin

lemma wellorder_Least_lemma:
  fixes k :: 'a
  assumes "P k"
  shows LeastI: "P (LEAST x. P x)" and Least_le: "(LEAST x. P x) ≤ k"
proof -
  have "P (LEAST x. P x) ∧ (LEAST x. P x) ≤ k"
  using assms proof (induct k rule: less_induct)
    case (less x) then have "P x" by simp
    show ?case proof (rule classical)
      assume assm: "¬ (P (LEAST a. P a) ∧ (LEAST a. P a) ≤ x)"
      have "⋀y. P y ⟹ x ≤ y"
      proof (rule classical)
        fix y
        assume "P y" and "¬ x ≤ y"
        with less have "P (LEAST a. P a)" and "(LEAST a. P a) ≤ y"
          by (auto simp add: not_le)
        with assm have "x < (LEAST a. P a)" and "(LEAST a. P a) ≤ y"
          by auto
        then show "x ≤ y" by auto
      qed
      with ‹P x› have Least: "(LEAST a. P a) = x"
        by (rule Least_equality)
      with ‹P x› show ?thesis by simp
    qed
  qed
  then show "P (LEAST x. P x)" and "(LEAST x. P x) ≤ k" by auto
qed

 "The following 3 lemmas are due to Brian Huffman"
lemma LeastI_ex: "∃x. P x ⟹ P (Least P)"
  by (erule exE) (erule LeastI)

lemma LeastI2:
  "P a ⟹ (⋀x. P x ⟹ Q x) ⟹ Q (Least P)"
  by (blast intro: LeastI)

lemma LeastI2_ex:
  "∃a. P a ⟹ (⋀x. P x ⟹ Q x) ⟹ Q (Least P)"
  by (blast intro: LeastI_ex)

lemma LeastI2_wellorder:
  assumes "P a"
  and "⋀a. ⟦ P a; ∀b. P b ⟶ a ≤ b ⟧ ⟹ Q a"
  shows "Q (Least P)"
proof (rule LeastI2_order)
  show "P (Least P)" using ‹P a› by (rule LeastI)
next
  fix y assume "P y" thus "Least P ≤ y" by (rule Least_le)
next
  fix x assume "P x" "∀y. P y ⟶ x ≤ y" thus "Q x" by (rule assms(2))
qed

lemma LeastI2_wellorder_ex:
  assumes "∃x. P x"
  and "⋀a. ⟦ P a; ∀b. P b ⟶ a ≤ b ⟧ ⟹ Q a"
  shows "Q (Least P)"
using assms by clarify (blast intro!: LeastI2_wellorder)

lemma not_less_Least: "k < (LEAST x. P x) ⟹ ¬ P k"
apply (simp add: not_le [symmetric])
apply (erule contrapos_nn)
apply (erule Least_le)
done

lemma exists_least_iff: "(∃n. P n) ⟷ (∃n. P n ∧ (∀m < n. ¬ P m))" (is "?lhs ⟷ ?rhs")
proof
  assume ?rhs thus ?lhs by blast
next
  assume H: ?lhs then obtain n where n: "P n" by blast
  let ?x = "Least P"
  { fix m assume m: "m < ?x"
    from not_less_Least[OF m] have "¬ P m" . }
  with LeastI_ex[OF H] show ?rhs by blast
qed

end


subsection ‹Order on @{typ bool}›

instantiation bool :: "{order_bot, order_top, linorder}"
begin

definition
  le_bool_def [simp]: "P ≤ Q ⟷ P ⟶ Q"

definition
  [simp]: "(P::bool) < Q ⟷ ¬ P ∧ Q"

definition
  [simp]: "⊥ ⟷ False"

definition
  [simp]: "⊤ ⟷ True"

instance proof
qed auto

end

lemma le_boolI: "(P ⟹ Q) ⟹ P ≤ Q"
  by simp

lemma le_boolI': "P ⟶ Q ⟹ P ≤ Q"
  by simp

lemma le_boolE: "P ≤ Q ⟹ P ⟹ (Q ⟹ R) ⟹ R"
  by simp

lemma le_boolD: "P ≤ Q ⟹ P ⟶ Q"
  by simp

lemma bot_boolE: "⊥ ⟹ P"
  by simp

lemma top_boolI: 
  by simp

lemma [code]:
  "False ≤ b ⟷ True"
  "True ≤ b ⟷ b"
  "False < b ⟷ b"
  "True < b ⟷ False"
  by simp_all


subsection ‹Order on @{typ "_ ⇒ _"}›

instantiation "fun" :: (type, ord) ord
begin

definition
  le_fun_def: "f ≤ g ⟷ (∀x. f x ≤ g x)"

definition
  "(f::'a ⇒ 'b) < g ⟷ f ≤ g ∧ ¬ (g ≤ f)"

instance ..

end

instance "fun" :: (type, preorder) preorder proof
qed (auto simp add: le_fun_def less_fun_def
  intro: order_trans antisym)

instance "fun" :: (type, order) order proof
qed (auto simp add: le_fun_def intro: antisym)

instantiation "fun" :: (type, bot) bot
begin

definition
  "⊥ = (λx. ⊥)"

instance ..

end

instantiation "fun" :: (type, order_bot) order_bot
begin

lemma bot_apply [simp, code]:
  "⊥ x = ⊥"
  by (simp add: bot_fun_def)

instance proof
qed (simp add: le_fun_def)

end

instantiation "fun" :: (type, top) top
begin

definition
  [no_atp]: "⊤ = (λx. ⊤)"

instance ..

end

instantiation "fun" :: (type, order_top) order_top
begin

lemma top_apply [simp, code]:
  "⊤ x = ⊤"
  by (simp add: top_fun_def)

instance proof
qed (simp add: le_fun_def)

end

lemma le_funI: "(⋀x. f x ≤ g x) ⟹ f ≤ g"
  unfolding le_fun_def by simp

lemma le_funE: "f ≤ g ⟹ (f x ≤ g x ⟹ P) ⟹ P"
  unfolding le_fun_def by simp

lemma le_funD: "f ≤ g ⟹ f x ≤ g x"
  by (rule le_funE)

lemma mono_compose: "mono Q ⟹ mono (λi x. Q i (f x))"
  unfolding mono_def le_fun_def by auto


subsection ‹Order on unary and binary predicates›

lemma predicate1I:
  assumes PQ: "⋀x. P x ⟹ Q x"
  shows "P ≤ Q"
  apply (rule le_funI)
  apply (rule le_boolI)
  apply (rule PQ)
  apply assumption
  done

lemma predicate1D:
  "P ≤ Q ⟹ P x ⟹ Q x"
  apply (erule le_funE)
  apply (erule le_boolE)
  apply assumption+
  done

lemma rev_predicate1D:
  "P x ⟹ P ≤ Q ⟹ Q x"
  by (rule predicate1D)

lemma predicate2I:
  assumes PQ: "⋀x y. P x y ⟹ Q x y"
  shows "P ≤ Q"
  apply (rule le_funI)+
  apply (rule le_boolI)
  apply (rule PQ)
  apply assumption
  done

lemma predicate2D:
  "P ≤ Q ⟹ P x y ⟹ Q x y"
  apply (erule le_funE)+
  apply (erule le_boolE)
  apply assumption+
  done

lemma rev_predicate2D:
  "P x y ⟹ P ≤ Q ⟹ Q x y"
  by (rule predicate2D)

lemma bot1E [no_atp]: "⊥ x ⟹ P"
  by (simp add: bot_fun_def)

lemma bot2E: "⊥ x y ⟹ P"
  by (simp add: bot_fun_def)

lemma top1I: "⊤ x"
  by (simp add: top_fun_def)

lemma top2I: "⊤ x y"
  by (simp add: top_fun_def)


subsection ‹Name duplicates›

lemmas order_eq_refl = preorder_class.eq_refl
lemmas order_less_irrefl = preorder_class.less_irrefl
lemmas order_less_imp_le = preorder_class.less_imp_le
lemmas order_less_not_sym = preorder_class.less_not_sym
lemmas order_less_asym = preorder_class.less_asym
lemmas order_less_trans = preorder_class.less_trans
lemmas order_le_less_trans = preorder_class.le_less_trans
lemmas order_less_le_trans = preorder_class.less_le_trans
lemmas order_less_imp_not_less = preorder_class.less_imp_not_less
lemmas order_less_imp_triv = preorder_class.less_imp_triv
lemmas order_less_asym' = preorder_class.less_asym'

lemmas order_less_le = order_class.less_le
lemmas order_le_less = order_class.le_less
lemmas order_le_imp_less_or_eq = order_class.le_imp_less_or_eq
lemmas order_less_imp_not_eq = order_class.less_imp_not_eq
lemmas order_less_imp_not_eq2 = order_class.less_imp_not_eq2
lemmas order_neq_le_trans = order_class.neq_le_trans
lemmas order_le_neq_trans = order_class.le_neq_trans
lemmas order_antisym = order_class.antisym
lemmas order_eq_iff = order_class.eq_iff
lemmas order_antisym_conv = order_class.antisym_conv

lemmas linorder_linear = linorder_class.linear
lemmas linorder_less_linear = linorder_class.less_linear
lemmas linorder_le_less_linear = linorder_class.le_less_linear
lemmas linorder_le_cases = linorder_class.le_cases
lemmas linorder_not_less = linorder_class.not_less
lemmas linorder_not_le = linorder_class.not_le
lemmas linorder_neq_iff = linorder_class.neq_iff
lemmas linorder_neqE = linorder_class.neqE
lemmas linorder_antisym_conv1 = linorder_class.antisym_conv1
lemmas linorder_antisym_conv2 = linorder_class.antisym_conv2
lemmas linorder_antisym_conv3 = linorder_class.antisym_conv3

end