src/HOL/Orderings.thy

cleaned up

(*  Title:      HOL/Orderings.thy
    ID:         $Id$
    Author:     Tobias Nipkow, Markus Wenzel, and Larry Paulson
*)

header {* Abstract orderings *}

theory Orderings
imports Code_Generator Lattice_Locales
begin

section {* Abstract orderings *}

subsection {* Order signatures *}

class ord = eq +
  constrains eq :: "'a \<Rightarrow> 'a \<Rightarrow> bool" (*FIXME: class_package should do the job*)
  fixes less_eq :: "'a \<Rightarrow> 'a \<Rightarrow> bool"
  fixes less    :: "'a \<Rightarrow> 'a \<Rightarrow> bool"

const_syntax
  less  ("op <")
  less  ("(_/ < _)"  [50, 51] 50)
  less_eq  ("op <=")
  less_eq  ("(_/ <= _)" [50, 51] 50)

const_syntax (xsymbols)
  less_eq  ("op \<le>")
  less_eq  ("(_/ \<le> _)"  [50, 51] 50)

const_syntax (HTML output)
  less_eq  ("op \<le>")
  less_eq  ("(_/ \<le> _)"  [50, 51] 50)


abbreviation (in ord)
  "less_eq_syn \<equiv> less_eq"
  "less_syn \<equiv> less"

const_syntax (in ord) 
  less_eq_syn  ("op \<^loc><=")
  less_eq_syn  ("(_/ \<^loc><= _)" [50, 51] 50)
  less_syn  ("op \<^loc><")
  less_syn  ("(_/ \<^loc>< _)"  [50, 51] 50)
  
const_syntax (in ord) (xsymbols)
  less_eq_syn  ("op \<^loc>\<le>")
  less_eq_syn  ("(_/ \<^loc>\<le> _)"  [50, 51] 50)

const_syntax (in ord) (HTML output)
  less_eq_syn  ("op \<^loc>\<le>")
  less_eq_syn  ("(_/ \<^loc>\<le> _)"  [50, 51] 50)


abbreviation (input)
  greater  (infixl ">" 50)
  "x > y \<equiv> y < x"
  greater_eq  (infixl ">=" 50)
  "x >= y \<equiv> y <= x"
  
const_syntax (xsymbols)
  greater_eq  (infixl "\<ge>" 50)

abbreviation (in ord) (input)
  greater  (infix "\<^loc>>" 50)
  "x \<^loc>> y \<equiv> y \<^loc>< x"
  greater_eq  (infix "\<^loc>>=" 50)
  "x \<^loc>>= y \<equiv> y \<^loc><= x"

const_syntax (in ord) (xsymbols)
  greater_eq  (infixl "\<^loc>\<ge>" 50)


subsection {* Partial orderings *}

axclass order < ord
  order_refl [iff]: "x <= x"
  order_trans: "x <= y ==> y <= z ==> x <= z"
  order_antisym: "x <= y ==> y <= x ==> x = y"
  order_less_le: "(x < y) = (x <= y & x ~= y)"

text {* Connection to locale: *}

interpretation order:
  partial_order["op \<le> :: 'a::order \<Rightarrow> 'a \<Rightarrow> bool"]
apply(rule partial_order.intro)
apply(rule order_refl, erule (1) order_trans, erule (1) order_antisym)
done

text {* Reflexivity. *}

lemma order_eq_refl: "!!x::'a::order. x = y ==> x <= y"
    -- {* This form is useful with the classical reasoner. *}
  apply (erule ssubst)
  apply (rule order_refl)
  done

lemma order_less_irrefl [iff]: "~ x < (x::'a::order)"
  by (simp add: order_less_le)

lemma order_le_less: "((x::'a::order) <= y) = (x < y | x = y)"
    -- {* NOT suitable for iff, since it can cause PROOF FAILED. *}
  apply (simp add: order_less_le, blast)
  done

lemmas order_le_imp_less_or_eq = order_le_less [THEN iffD1, standard]

lemma order_less_imp_le: "!!x::'a::order. x < y ==> x <= y"
  by (simp add: order_less_le)

text {* Asymmetry. *}

lemma order_less_not_sym: "(x::'a::order) < y ==> ~ (y < x)"
  by (simp add: order_less_le order_antisym)

lemma order_less_asym: "x < (y::'a::order) ==> (~P ==> y < x) ==> P"
  apply (drule order_less_not_sym)
  apply (erule contrapos_np, simp)
  done

lemma order_eq_iff: "!!x::'a::order. (x = y) = (x \<le> y & y \<le> x)"
by (blast intro: order_antisym)

lemma order_antisym_conv: "(y::'a::order) <= x ==> (x <= y) = (x = y)"
by(blast intro:order_antisym)

lemma less_imp_neq: "[| (x::'a::order) < y |] ==> x ~= y"
  by (erule contrapos_pn, erule subst, rule order_less_irrefl)

text {* Transitivity. *}

lemma order_less_trans: "!!x::'a::order. [| x < y; y < z |] ==> x < z"
  apply (simp add: order_less_le)
  apply (blast intro: order_trans order_antisym)
  done

lemma order_le_less_trans: "!!x::'a::order. [| x <= y; y < z |] ==> x < z"
  apply (simp add: order_less_le)
  apply (blast intro: order_trans order_antisym)
  done

lemma order_less_le_trans: "!!x::'a::order. [| x < y; y <= z |] ==> x < z"
  apply (simp add: order_less_le)
  apply (blast intro: order_trans order_antisym)
  done

lemma eq_neq_eq_imp_neq: "[| x = a ; a ~= b; b = y |] ==> x ~= y"
  by (erule subst, erule ssubst, assumption)

text {* Useful for simplification, but too risky to include by default. *}

lemma order_less_imp_not_less: "(x::'a::order) < y ==>  (~ y < x) = True"
  by (blast elim: order_less_asym)

lemma order_less_imp_triv: "(x::'a::order) < y ==>  (y < x --> P) = True"
  by (blast elim: order_less_asym)

lemma order_less_imp_not_eq: "(x::'a::order) < y ==>  (x = y) = False"
  by auto

lemma order_less_imp_not_eq2: "(x::'a::order) < y ==>  (y = x) = False"
  by auto

text {* Transitivity rules for calculational reasoning *}

lemma order_neq_le_trans: "a ~= b ==> (a::'a::order) <= b ==> a < b"
  by (simp add: order_less_le)

lemma order_le_neq_trans: "(a::'a::order) <= b ==> a ~= b ==> a < b"
  by (simp add: order_less_le)

lemma order_less_asym': "(a::'a::order) < b ==> b < a ==> P"
  by (rule order_less_asym)


subsection {* Total orderings *}

axclass linorder < order
  linorder_linear: "x <= y | y <= x"

lemma linorder_less_linear: "!!x::'a::linorder. x<y | x=y | y<x"
  apply (simp add: order_less_le)
  apply (insert linorder_linear, blast)
  done

lemma linorder_le_less_linear: "!!x::'a::linorder. x\<le>y | y<x"
  by (simp add: order_le_less linorder_less_linear)

lemma linorder_le_cases [case_names le ge]:
    "((x::'a::linorder) \<le> y ==> P) ==> (y \<le> x ==> P) ==> P"
  by (insert linorder_linear, blast)

lemma linorder_cases [case_names less equal greater]:
    "((x::'a::linorder) < y ==> P) ==> (x = y ==> P) ==> (y < x ==> P) ==> P"
  by (insert linorder_less_linear, blast)

lemma linorder_not_less: "!!x::'a::linorder. (~ x < y) = (y <= x)"
  apply (simp add: order_less_le)
  apply (insert linorder_linear)
  apply (blast intro: order_antisym)
  done

lemma linorder_not_le: "!!x::'a::linorder. (~ x <= y) = (y < x)"
  apply (simp add: order_less_le)
  apply (insert linorder_linear)
  apply (blast intro: order_antisym)
  done

lemma linorder_neq_iff: "!!x::'a::linorder. (x ~= y) = (x<y | y<x)"
by (cut_tac x = x and y = y in linorder_less_linear, auto)

lemma linorder_neqE: "x ~= (y::'a::linorder) ==> (x < y ==> R) ==> (y < x ==> R) ==> R"
by (simp add: linorder_neq_iff, blast)

lemma linorder_antisym_conv1: "~ (x::'a::linorder) < y ==> (x <= y) = (x = y)"
by(blast intro:order_antisym dest:linorder_not_less[THEN iffD1])

lemma linorder_antisym_conv2: "(x::'a::linorder) <= y ==> (~ x < y) = (x = y)"
by(blast intro:order_antisym dest:linorder_not_less[THEN iffD1])

lemma linorder_antisym_conv3: "~ (y::'a::linorder) < x ==> (~ x < y) = (x = y)"
by(blast intro:order_antisym dest:linorder_not_less[THEN iffD1])

text{*Replacing the old Nat.leI*}
lemma leI: "~ x < y ==> y <= (x::'a::linorder)"
  by (simp only: linorder_not_less)

lemma leD: "y <= (x::'a::linorder) ==> ~ x < y"
  by (simp only: linorder_not_less)

(*FIXME inappropriate name (or delete altogether)*)
lemma not_leE: "~ y <= (x::'a::linorder) ==> x < y"
  by (simp only: linorder_not_le)


subsection {* Reasoning tools setup *}

setup {*
let

val order_antisym_conv = thm "order_antisym_conv"
val linorder_antisym_conv1 = thm "linorder_antisym_conv1"
val linorder_antisym_conv2 = thm "linorder_antisym_conv2"
val linorder_antisym_conv3 = thm "linorder_antisym_conv3"

fun prp t thm = (#prop (rep_thm thm) = t);

fun prove_antisym_le sg ss ((le as Const(_,T)) $ r $ s) =
  let val prems = prems_of_ss ss;
      val less = Const("Orderings.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 linorder_antisym_conv1))
         end
     | SOME thm => SOME(mk_meta_eq(thm RS order_antisym_conv))
  end
  handle THM _ => NONE;

fun prove_antisym_less sg ss (NotC $ ((less as Const(_,T)) $ r $ s)) =
  let val prems = prems_of_ss ss;
      val le = Const("Orderings.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 linorder_antisym_conv3))
         end
     | SOME thm => SOME(mk_meta_eq(thm RS linorder_antisym_conv2))
  end
  handle THM _ => NONE;

val antisym_le = Simplifier.simproc (the_context())
  "antisym le" ["(x::'a::order) <= y"] prove_antisym_le;
val antisym_less = Simplifier.simproc (the_context())
  "antisym less" ["~ (x::'a::linorder) < y"] prove_antisym_less;

in

 (fn thy => (Simplifier.change_simpset_of thy
  (fn ss => ss addsimprocs [antisym_le, antisym_less]); thy))

end
*}

ML_setup {*

(* The setting up of Quasi_Tac serves as a demo.  Since there is no
   class for quasi orders, the tactics Quasi_Tac.trans_tac and
   Quasi_Tac.quasi_tac are not of much use. *)

fun decomp_gen sort thy (Trueprop $ t) =
  let fun of_sort t = let val T = type_of t in
        (* exclude numeric types: linear arithmetic subsumes transitivity *)
        T <> HOLogic.natT andalso T <> HOLogic.intT andalso
        T <> HOLogic.realT andalso Sign.of_sort thy (T, sort) end
  fun dec (Const ("Not", _) $ t) = (
	  case dec t of
	    NONE => NONE
	  | SOME (t1, rel, t2) => SOME (t1, "~" ^ rel, t2))
	| dec (Const ("op =",  _) $ t1 $ t2) =
	    if of_sort t1
	    then SOME (t1, "=", t2)
	    else NONE
	| dec (Const ("Orderings.less_eq",  _) $ t1 $ t2) =
	    if of_sort t1
	    then SOME (t1, "<=", t2)
	    else NONE
	| dec (Const ("Orderings.less",  _) $ t1 $ t2) =
	    if of_sort t1
	    then SOME (t1, "<", t2)
	    else NONE
	| dec _ = NONE
  in dec t end;

structure Quasi_Tac = Quasi_Tac_Fun (
  struct
    val le_trans = thm "order_trans";
    val le_refl = thm "order_refl";
    val eqD1 = thm "order_eq_refl";
    val eqD2 = thm "sym" RS thm "order_eq_refl";
    val less_reflE = thm "order_less_irrefl" RS thm "notE";
    val less_imp_le = thm "order_less_imp_le";
    val le_neq_trans = thm "order_le_neq_trans";
    val neq_le_trans = thm "order_neq_le_trans";
    val less_imp_neq = thm "less_imp_neq";
    val decomp_trans = decomp_gen ["Orderings.order"];
    val decomp_quasi = decomp_gen ["Orderings.order"];

  end);  (* struct *)

structure Order_Tac = Order_Tac_Fun (
  struct
    val less_reflE = thm "order_less_irrefl" RS thm "notE";
    val le_refl = thm "order_refl";
    val less_imp_le = thm "order_less_imp_le";
    val not_lessI = thm "linorder_not_less" RS thm "iffD2";
    val not_leI = thm "linorder_not_le" RS thm "iffD2";
    val not_lessD = thm "linorder_not_less" RS thm "iffD1";
    val not_leD = thm "linorder_not_le" RS thm "iffD1";
    val eqI = thm "order_antisym";
    val eqD1 = thm "order_eq_refl";
    val eqD2 = thm "sym" RS thm "order_eq_refl";
    val less_trans = thm "order_less_trans";
    val less_le_trans = thm "order_less_le_trans";
    val le_less_trans = thm "order_le_less_trans";
    val le_trans = thm "order_trans";
    val le_neq_trans = thm "order_le_neq_trans";
    val neq_le_trans = thm "order_neq_le_trans";
    val less_imp_neq = thm "less_imp_neq";
    val eq_neq_eq_imp_neq = thm "eq_neq_eq_imp_neq";
    val not_sym = thm "not_sym";
    val decomp_part = decomp_gen ["Orderings.order"];
    val decomp_lin = decomp_gen ["Orderings.linorder"];

  end);  (* struct *)

change_simpset (fn ss => ss
    addSolver (mk_solver "Trans_linear" (fn _ => Order_Tac.linear_tac))
    addSolver (mk_solver "Trans_partial" (fn _ => Order_Tac.partial_tac)));
  (* 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). *)
*}

(* Optional setup of methods *)

(*
method_setup trans_partial =
  {* Method.no_args (Method.SIMPLE_METHOD' HEADGOAL (Order_Tac.partial_tac)) *}
  {* transitivity reasoner for partial orders *}	
method_setup trans_linear =
  {* Method.no_args (Method.SIMPLE_METHOD' HEADGOAL (Order_Tac.linear_tac)) *}
  {* transitivity reasoner for linear orders *}
*)

(*
declare order.order_refl [simp del] order_less_irrefl [simp del]

can currently not be removed, abel_cancel relies on it.
*)


subsection {* Bounded quantifiers *}

syntax
  "_lessAll" :: "[idt, 'a, bool] => bool"   ("(3ALL _<_./ _)"  [0, 0, 10] 10)
  "_lessEx"  :: "[idt, 'a, bool] => bool"   ("(3EX _<_./ _)"  [0, 0, 10] 10)
  "_leAll"   :: "[idt, 'a, bool] => bool"   ("(3ALL _<=_./ _)" [0, 0, 10] 10)
  "_leEx"    :: "[idt, 'a, bool] => bool"   ("(3EX _<=_./ _)" [0, 0, 10] 10)

  "_gtAll" :: "[idt, 'a, bool] => bool"   ("(3ALL _>_./ _)"  [0, 0, 10] 10)
  "_gtEx"  :: "[idt, 'a, bool] => bool"   ("(3EX _>_./ _)"  [0, 0, 10] 10)
  "_geAll"   :: "[idt, 'a, bool] => bool"   ("(3ALL _>=_./ _)" [0, 0, 10] 10)
  "_geEx"    :: "[idt, 'a, bool] => bool"   ("(3EX _>=_./ _)" [0, 0, 10] 10)

syntax (xsymbols)
  "_lessAll" :: "[idt, 'a, bool] => bool"   ("(3\<forall>_<_./ _)"  [0, 0, 10] 10)
  "_lessEx"  :: "[idt, 'a, bool] => bool"   ("(3\<exists>_<_./ _)"  [0, 0, 10] 10)
  "_leAll"   :: "[idt, 'a, bool] => bool"   ("(3\<forall>_\<le>_./ _)" [0, 0, 10] 10)
  "_leEx"    :: "[idt, 'a, bool] => bool"   ("(3\<exists>_\<le>_./ _)" [0, 0, 10] 10)

  "_gtAll" :: "[idt, 'a, bool] => bool"   ("(3\<forall>_>_./ _)"  [0, 0, 10] 10)
  "_gtEx"  :: "[idt, 'a, bool] => bool"   ("(3\<exists>_>_./ _)"  [0, 0, 10] 10)
  "_geAll"   :: "[idt, 'a, bool] => bool"   ("(3\<forall>_\<ge>_./ _)" [0, 0, 10] 10)
  "_geEx"    :: "[idt, 'a, bool] => bool"   ("(3\<exists>_\<ge>_./ _)" [0, 0, 10] 10)

syntax (HOL)
  "_lessAll" :: "[idt, 'a, bool] => bool"   ("(3! _<_./ _)"  [0, 0, 10] 10)
  "_lessEx"  :: "[idt, 'a, bool] => bool"   ("(3? _<_./ _)"  [0, 0, 10] 10)
  "_leAll"   :: "[idt, 'a, bool] => bool"   ("(3! _<=_./ _)" [0, 0, 10] 10)
  "_leEx"    :: "[idt, 'a, bool] => bool"   ("(3? _<=_./ _)" [0, 0, 10] 10)

syntax (HTML output)
  "_lessAll" :: "[idt, 'a, bool] => bool"   ("(3\<forall>_<_./ _)"  [0, 0, 10] 10)
  "_lessEx"  :: "[idt, 'a, bool] => bool"   ("(3\<exists>_<_./ _)"  [0, 0, 10] 10)
  "_leAll"   :: "[idt, 'a, bool] => bool"   ("(3\<forall>_\<le>_./ _)" [0, 0, 10] 10)
  "_leEx"    :: "[idt, 'a, bool] => bool"   ("(3\<exists>_\<le>_./ _)" [0, 0, 10] 10)

  "_gtAll" :: "[idt, 'a, bool] => bool"   ("(3\<forall>_>_./ _)"  [0, 0, 10] 10)
  "_gtEx"  :: "[idt, 'a, bool] => bool"   ("(3\<exists>_>_./ _)"  [0, 0, 10] 10)
  "_geAll"   :: "[idt, 'a, bool] => bool"   ("(3\<forall>_\<ge>_./ _)" [0, 0, 10] 10)
  "_geEx"    :: "[idt, 'a, bool] => bool"   ("(3\<exists>_\<ge>_./ _)" [0, 0, 10] 10)

translations
  "ALL x<y. P"   =>  "ALL x. x < y \<longrightarrow> P"
  "EX x<y. P"    =>  "EX x. x < y \<and> P"
  "ALL x<=y. P"  =>  "ALL x. x <= y \<longrightarrow> P"
  "EX x<=y. P"   =>  "EX x. x <= y \<and> P"
  "ALL x>y. P"   =>  "ALL x. x > y \<longrightarrow> P"
  "EX x>y. P"    =>  "EX x. x > y \<and> P"
  "ALL x>=y. P"  =>  "ALL x. x >= y \<longrightarrow> P"
  "EX x>=y. P"   =>  "EX x. x >= y \<and> P"

print_translation {*
let
  fun mk v v' c n P =
    if v = v' andalso not (member (op =) (map fst (Term.add_frees n [])) v)
    then Syntax.const c $ Syntax.mark_bound v' $ n $ P else raise Match;
  fun mk_all "\\<^const>Scratch.less" f =
        f ("_lessAll", "_gtAll")
    | mk_all "\\<^const>Scratch.less_eq" f =
        f ("_leAll", "_geAll")
  fun mk_ex "\\<^const>Scratch.less" f =
        f ("_lessEx", "_gtEx")
    | mk_ex "\\<^const>Scratch.less_eq" f =
        f ("_leEx", "_geEx");
  fun tr_all' [Const ("_bound", _) $ Free (v, _), Const("op -->", _)
          $ (Const (c, _) $ (Const ("_bound", _) $ Free (v', _)) $ n) $ P] =
        mk v v' (mk_all c fst) n P
    | tr_all' [Const ("_bound", _) $ Free (v, _), Const("op -->", _)
          $ (Const (c, _) $ n $ (Const ("_bound", _) $ Free (v', _))) $ P] =
        mk v v' (mk_all c snd) n P;
  fun tr_ex' [Const ("_bound", _) $ Free (v, _), Const("op &", _)
          $ (Const (c, _) $ (Const ("_bound", _) $ Free (v', _)) $ n) $ P] =
        mk v v' (mk_ex c fst) n P
    | tr_ex' [Const ("_bound", _) $ Free (v, _), Const("op &", _)
          $ (Const (c, _) $ n $ (Const ("_bound", _) $ Free (v', _))) $ P] =
        mk v v' (mk_ex c snd) n P;
in
  [("ALL ", tr_all'), ("EX ", tr_ex')]
end
*}


subsection {* Transitivity reasoning on decreasing inequalities *}

text {* These support proving chains of decreasing inequalities
    a >= b >= c ... in Isar proofs. *}

lemma xt1:
  "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:
  "(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: "(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: "(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: "(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: "(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: "(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: "(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: "(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 {* Least value operator, monotonicity and min/max *}
 
(*FIXME: derive more of the min/max laws generically via semilattices*)

constdefs
  Least :: "('a::ord => bool) => 'a"               (binder "LEAST " 10)
  "Least P == THE x. P x & (ALL y. P y --> x <= y)"
    -- {* We can no longer use LeastM because the latter requires Hilbert-AC. *}

lemma LeastI2_order:
  "[| P (x::'a::order);
      !!y. P y ==> x <= y;
      !!x. [| P x; ALL y. P y --> x \<le> y |] ==> Q x |]
   ==> Q (Least P)"
  apply (unfold Least_def)
  apply (rule theI2)
    apply (blast intro: order_antisym)+
  done

lemma Least_equality:
    "[| P (k::'a::order); !!x. P x ==> k <= x |] ==> (LEAST x. P x) = k"
  apply (simp add: Least_def)
  apply (rule the_equality)
  apply (auto intro!: order_antisym)
  done

locale mono =
  fixes f
  assumes mono: "A <= B ==> f A <= f B"

lemmas monoI [intro?] = mono.intro
  and monoD [dest?] = mono.mono

constdefs
  min :: "['a::ord, 'a] => 'a"
  "min a b == (if a <= b then a else b)"
  max :: "['a::ord, 'a] => 'a"
  "max a b == (if a <= b then b else a)"

lemma min_leastR: "(\<And>x\<Colon>'a\<Colon>order. least \<le> x) \<Longrightarrow> min x least = least"
  apply (simp add: min_def)
  apply (blast intro: order_antisym)
  done

lemma max_leastR: "(\<And>x\<Colon>'a\<Colon>order. least \<le> x) \<Longrightarrow> max x least = x"
  apply (simp add: max_def)
  apply (blast intro: order_antisym)
  done

lemma min_leastL: "(!!x. least <= x) ==> min least x = least"
  by (simp add: min_def)

lemma max_leastL: "(!!x. least <= x) ==> max least x = x"
  by (simp add: max_def)

lemma min_of_mono:
    "(!!x y. (f x <= f y) = (x <= y)) ==> min (f m) (f n) = f (min m n)"
  by (simp add: min_def)

lemma max_of_mono:
    "(!!x y. (f x <= f y) = (x <= y)) ==> max (f m) (f n) = f (max m n)"
  by (simp add: max_def)

text{* Instantiate locales: *}

interpretation min_max:
  lower_semilattice["op \<le>" "min :: 'a::linorder \<Rightarrow> 'a \<Rightarrow> 'a"]
apply unfold_locales
apply(simp add:min_def linorder_not_le order_less_imp_le)
apply(simp add:min_def linorder_not_le order_less_imp_le)
apply(simp add:min_def linorder_not_le order_less_imp_le)
done

interpretation min_max:
  upper_semilattice["op \<le>" "max :: 'a::linorder \<Rightarrow> 'a \<Rightarrow> 'a"]
apply unfold_locales
apply(simp add: max_def linorder_not_le order_less_imp_le)
apply(simp add: max_def linorder_not_le order_less_imp_le)
apply(simp add: max_def linorder_not_le order_less_imp_le)
done

interpretation min_max:
  lattice["op \<le>" "min :: 'a::linorder \<Rightarrow> 'a \<Rightarrow> 'a" "max"]
  by unfold_locales

interpretation min_max:
  distrib_lattice["op \<le>" "min :: 'a::linorder \<Rightarrow> 'a \<Rightarrow> 'a" "max"]
apply unfold_locales
apply(rule_tac x=x and y=y in linorder_le_cases)
apply(rule_tac x=x and y=z in linorder_le_cases)
apply(rule_tac x=y and y=z in linorder_le_cases)
apply(simp add:min_def max_def)
apply(simp add:min_def max_def)
apply(rule_tac x=y and y=z in linorder_le_cases)
apply(simp add:min_def max_def)
apply(simp add:min_def max_def)
apply(rule_tac x=x and y=z in linorder_le_cases)
apply(rule_tac x=y and y=z in linorder_le_cases)
apply(simp add:min_def max_def)
apply(simp add:min_def max_def)
apply(rule_tac x=y and y=z in linorder_le_cases)
apply(simp add:min_def max_def)
apply(simp add:min_def max_def)
done

lemma le_max_iff_disj: "!!z::'a::linorder. (z <= max x y) = (z <= x | z <= y)"
  apply(simp add:max_def)
  apply (insert linorder_linear)
  apply (blast intro: order_trans)
  done

lemmas le_maxI1 = min_max.sup_ge1
lemmas le_maxI2 = min_max.sup_ge2

lemma less_max_iff_disj: "!!z::'a::linorder. (z < max x y) = (z < x | z < y)"
  apply (simp add: max_def order_le_less)
  apply (insert linorder_less_linear)
  apply (blast intro: order_less_trans)
  done

lemma max_less_iff_conj [simp]:
    "!!z::'a::linorder. (max x y < z) = (x < z & y < z)"
  apply (simp add: order_le_less max_def)
  apply (insert linorder_less_linear)
  apply (blast intro: order_less_trans)
  done

lemma min_less_iff_conj [simp]:
    "!!z::'a::linorder. (z < min x y) = (z < x & z < y)"
  apply (simp add: order_le_less min_def)
  apply (insert linorder_less_linear)
  apply (blast intro: order_less_trans)
  done

lemma min_le_iff_disj: "!!z::'a::linorder. (min x y <= z) = (x <= z | y <= z)"
  apply (simp add: min_def)
  apply (insert linorder_linear)
  apply (blast intro: order_trans)
  done

lemma min_less_iff_disj: "!!z::'a::linorder. (min x y < z) = (x < z | y < z)"
  apply (simp add: min_def order_le_less)
  apply (insert linorder_less_linear)
  apply (blast intro: order_less_trans)
  done

lemmas max_ac = min_max.sup_assoc min_max.sup_commute
               mk_left_commute[of max,OF min_max.sup_assoc min_max.sup_commute]

lemmas min_ac = min_max.inf_assoc min_max.inf_commute
               mk_left_commute[of min,OF min_max.inf_assoc min_max.inf_commute]

lemma split_min:
    "P (min (i::'a::linorder) j) = ((i <= j --> P(i)) & (~ i <= j --> P(j)))"
  by (simp add: min_def)

lemma split_max:
    "P (max (i::'a::linorder) j) = ((i <= j --> P(j)) & (~ i <= j --> P(i)))"
  by (simp add: max_def)

end