src/HOL/HOL.thy

added lemma

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

header {* The basis of Higher-Order Logic *}

theory HOL
imports CPure
uses
  "~~/src/Tools/integer.ML"
  ("hologic.ML")
  "~~/src/Tools/IsaPlanner/zipper.ML"
  "~~/src/Tools/IsaPlanner/isand.ML"
  "~~/src/Tools/IsaPlanner/rw_tools.ML"
  "~~/src/Tools/IsaPlanner/rw_inst.ML"
  "~~/src/Provers/project_rule.ML"
  "~~/src/Provers/induct_method.ML"
  "~~/src/Provers/hypsubst.ML"
  "~~/src/Provers/splitter.ML"
  "~~/src/Provers/classical.ML"
  "~~/src/Provers/blast.ML"
  "~~/src/Provers/clasimp.ML"
  "~~/src/Provers/eqsubst.ML"
  "~~/src/Provers/quantifier1.ML"
  ("simpdata.ML")
  "~~/src/Tools/code/code_name.ML"
  "~~/src/Tools/code/code_funcgr.ML"
  "~~/src/Tools/code/code_thingol.ML"
  "~~/src/Tools/code/code_target.ML"
  "~~/src/Tools/code/code_package.ML"
  "~~/src/Tools/nbe.ML"
begin

subsection {* Primitive logic *}

subsubsection {* Core syntax *}

classes type
defaultsort type

global

typedecl bool

arities
  bool :: type
  "fun" :: (type, type) type

judgment
  Trueprop      :: "bool => prop"                   ("(_)" 5)

consts
  Not           :: "bool => bool"                   ("~ _" [40] 40)
  True          :: bool
  False         :: bool
  arbitrary     :: 'a

  The           :: "('a => bool) => 'a"
  All           :: "('a => bool) => bool"           (binder "ALL " 10)
  Ex            :: "('a => bool) => bool"           (binder "EX " 10)
  Ex1           :: "('a => bool) => bool"           (binder "EX! " 10)
  Let           :: "['a, 'a => 'b] => 'b"

  "op ="        :: "['a, 'a] => bool"               (infixl "=" 50)
  "op &"        :: "[bool, bool] => bool"           (infixr "&" 35)
  "op |"        :: "[bool, bool] => bool"           (infixr "|" 30)
  "op -->"      :: "[bool, bool] => bool"           (infixr "-->" 25)

local

consts
  If            :: "[bool, 'a, 'a] => 'a"           ("(if (_)/ then (_)/ else (_))" 10)


subsubsection {* Additional concrete syntax *}

notation (output)
  "op ="  (infix "=" 50)

abbreviation
  not_equal :: "['a, 'a] => bool"  (infixl "~=" 50) where
  "x ~= y == ~ (x = y)"

notation (output)
  not_equal  (infix "~=" 50)

notation (xsymbols)
  Not  ("\<not> _" [40] 40) and
  "op &"  (infixr "\<and>" 35) and
  "op |"  (infixr "\<or>" 30) and
  "op -->"  (infixr "\<longrightarrow>" 25) and
  not_equal  (infix "\<noteq>" 50)

notation (HTML output)
  Not  ("\<not> _" [40] 40) and
  "op &"  (infixr "\<and>" 35) and
  "op |"  (infixr "\<or>" 30) and
  not_equal  (infix "\<noteq>" 50)

abbreviation (iff)
  iff :: "[bool, bool] => bool"  (infixr "<->" 25) where
  "A <-> B == A = B"

notation (xsymbols)
  iff  (infixr "\<longleftrightarrow>" 25)


nonterminals
  letbinds  letbind
  case_syn  cases_syn

syntax
  "_The"        :: "[pttrn, bool] => 'a"                 ("(3THE _./ _)" [0, 10] 10)

  "_bind"       :: "[pttrn, 'a] => letbind"              ("(2_ =/ _)" 10)
  ""            :: "letbind => letbinds"                 ("_")
  "_binds"      :: "[letbind, letbinds] => letbinds"     ("_;/ _")
  "_Let"        :: "[letbinds, 'a] => 'a"                ("(let (_)/ in (_))" 10)

  "_case_syntax":: "['a, cases_syn] => 'b"               ("(case _ of/ _)" 10)
  "_case1"      :: "['a, 'b] => case_syn"                ("(2_ =>/ _)" 10)
  ""            :: "case_syn => cases_syn"               ("_")
  "_case2"      :: "[case_syn, cases_syn] => cases_syn"  ("_/ | _")

translations
  "THE x. P"              == "The (%x. P)"
  "_Let (_binds b bs) e"  == "_Let b (_Let bs e)"
  "let x = a in e"        == "Let a (%x. e)"

print_translation {*
(* To avoid eta-contraction of body: *)
[("The", fn [Abs abs] =>
     let val (x,t) = atomic_abs_tr' abs
     in Syntax.const "_The" $ x $ t end)]
*}

syntax (xsymbols)
  "_case1"      :: "['a, 'b] => case_syn"                ("(2_ \<Rightarrow>/ _)" 10)

notation (xsymbols)
  All  (binder "\<forall>" 10) and
  Ex  (binder "\<exists>" 10) and
  Ex1  (binder "\<exists>!" 10)

notation (HTML output)
  All  (binder "\<forall>" 10) and
  Ex  (binder "\<exists>" 10) and
  Ex1  (binder "\<exists>!" 10)

notation (HOL)
  All  (binder "! " 10) and
  Ex  (binder "? " 10) and
  Ex1  (binder "?! " 10)


subsubsection {* Axioms and basic definitions *}

axioms
  eq_reflection:  "(x=y) ==> (x==y)"

  refl:           "t = (t::'a)"

  ext:            "(!!x::'a. (f x ::'b) = g x) ==> (%x. f x) = (%x. g x)"
    -- {*Extensionality is built into the meta-logic, and this rule expresses
         a related property.  It is an eta-expanded version of the traditional
         rule, and similar to the ABS rule of HOL*}

  the_eq_trivial: "(THE x. x = a) = (a::'a)"

  impI:           "(P ==> Q) ==> P-->Q"
  mp:             "[| P-->Q;  P |] ==> Q"


defs
  True_def:     "True      == ((%x::bool. x) = (%x. x))"
  All_def:      "All(P)    == (P = (%x. True))"
  Ex_def:       "Ex(P)     == !Q. (!x. P x --> Q) --> Q"
  False_def:    "False     == (!P. P)"
  not_def:      "~ P       == P-->False"
  and_def:      "P & Q     == !R. (P-->Q-->R) --> R"
  or_def:       "P | Q     == !R. (P-->R) --> (Q-->R) --> R"
  Ex1_def:      "Ex1(P)    == ? x. P(x) & (! y. P(y) --> y=x)"

axioms
  iff:          "(P-->Q) --> (Q-->P) --> (P=Q)"
  True_or_False:  "(P=True) | (P=False)"

defs
  Let_def:      "Let s f == f(s)"
  if_def:       "If P x y == THE z::'a. (P=True --> z=x) & (P=False --> z=y)"

finalconsts
  "op ="
  "op -->"
  The
  arbitrary

axiomatization
  undefined :: 'a

axiomatization where
  undefined_fun: "undefined x = undefined"


subsubsection {* Generic classes and algebraic operations *}

class default = type +
  fixes default :: "'a"

class zero = type + 
  fixes zero :: "'a"  ("\<^loc>0")

class one = type +
  fixes one  :: "'a"  ("\<^loc>1")

hide (open) const zero one

class plus = type +
  fixes plus :: "'a \<Rightarrow> 'a \<Rightarrow> 'a"  (infixl "\<^loc>+" 65)

class minus = type +
  fixes uminus :: "'a \<Rightarrow> 'a" 
    and minus :: "'a \<Rightarrow> 'a \<Rightarrow> 'a"  (infixl "\<^loc>-" 65)

class times = type +
  fixes times :: "'a \<Rightarrow> 'a \<Rightarrow> 'a"  (infixl "\<^loc>*" 70)

class inverse = type +
  fixes inverse :: "'a \<Rightarrow> 'a"
    and divide :: "'a \<Rightarrow> 'a \<Rightarrow> 'a"  (infixl "\<^loc>'/" 70)

class abs = type +
  fixes abs :: "'a \<Rightarrow> 'a"

class sgn = type +
  fixes sgn :: "'a \<Rightarrow> 'a"

notation
  uminus  ("- _" [81] 80)

notation (xsymbols)
  abs  ("\<bar>_\<bar>")
notation (HTML output)
  abs  ("\<bar>_\<bar>")

class ord = type +
  fixes less_eq :: "'a \<Rightarrow> 'a \<Rightarrow> bool"  (infix "\<sqsubseteq>" 50)
    and less :: "'a \<Rightarrow> 'a \<Rightarrow> bool"  (infix "\<sqsubset>" 50)
begin

notation
  less_eq  ("op \<^loc><=") and
  less_eq  ("(_/ \<^loc><= _)" [51, 51] 50) and
  less  ("op \<^loc><") and
  less  ("(_/ \<^loc>< _)"  [51, 51] 50)
  
notation (xsymbols)
  less_eq  ("op \<^loc>\<le>") and
  less_eq  ("(_/ \<^loc>\<le> _)"  [51, 51] 50)

notation (HTML output)
  less_eq  ("op \<^loc>\<le>") and
  less_eq  ("(_/ \<^loc>\<le> _)"  [51, 51] 50)

abbreviation (input)
  greater  (infix "\<^loc>>" 50) where
  "x \<^loc>> y \<equiv> y \<^loc>< x"

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

notation (input)
  greater_eq  (infix "\<^loc>\<ge>" 50)

definition
  Least :: "('a \<Rightarrow> bool) \<Rightarrow> 'a" (binder "\<^loc>LEAST " 10)
where
  "Least P == (THE x. P x \<and> (\<forall>y. P y \<longrightarrow> x \<^loc>\<le> y))"

end

notation
  less_eq  ("op <=") and
  less_eq  ("(_/ <= _)" [51, 51] 50) and
  less  ("op <") and
  less  ("(_/ < _)"  [51, 51] 50)
  
notation (xsymbols)
  less_eq  ("op \<le>") and
  less_eq  ("(_/ \<le> _)"  [51, 51] 50)

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

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

abbreviation (input)
  greater_eq  (infix ">=" 50) where
  "x >= y \<equiv> y <= x"

notation (input)
  greater_eq  (infix "\<ge>" 50)

syntax
  "_index1"  :: index    ("\<^sub>1")
translations
  (index) "\<^sub>1" => (index) "\<^bsub>\<struct>\<^esub>"

typed_print_translation {*
let
  fun tr' c = (c, fn show_sorts => fn T => fn ts =>
    if T = dummyT orelse not (! show_types) andalso can Term.dest_Type T then raise Match
    else Syntax.const Syntax.constrainC $ Syntax.const c $ Syntax.term_of_typ show_sorts T);
in map tr' [@{const_syntax HOL.one}, @{const_syntax HOL.zero}] end;
*} -- {* show types that are presumably too general *}


subsection {* Fundamental rules *}

subsubsection {* Equality *}

text {* Thanks to Stephan Merz *}
lemma subst:
  assumes eq: "s = t" and p: "P s"
  shows "P t"
proof -
  from eq have meta: "s \<equiv> t"
    by (rule eq_reflection)
  from p show ?thesis
    by (unfold meta)
qed

lemma sym: "s = t ==> t = s"
  by (erule subst) (rule refl)

lemma ssubst: "t = s ==> P s ==> P t"
  by (drule sym) (erule subst)

lemma trans: "[| r=s; s=t |] ==> r=t"
  by (erule subst)

lemma meta_eq_to_obj_eq: 
  assumes meq: "A == B"
  shows "A = B"
  by (unfold meq) (rule refl)

text {* Useful with @{text erule} for proving equalities from known equalities. *}
     (* a = b
        |   |
        c = d   *)
lemma box_equals: "[| a=b;  a=c;  b=d |] ==> c=d"
apply (rule trans)
apply (rule trans)
apply (rule sym)
apply assumption+
done

text {* For calculational reasoning: *}

lemma forw_subst: "a = b ==> P b ==> P a"
  by (rule ssubst)

lemma back_subst: "P a ==> a = b ==> P b"
  by (rule subst)


subsubsection {*Congruence rules for application*}

(*similar to AP_THM in Gordon's HOL*)
lemma fun_cong: "(f::'a=>'b) = g ==> f(x)=g(x)"
apply (erule subst)
apply (rule refl)
done

(*similar to AP_TERM in Gordon's HOL and FOL's subst_context*)
lemma arg_cong: "x=y ==> f(x)=f(y)"
apply (erule subst)
apply (rule refl)
done

lemma arg_cong2: "\<lbrakk> a = b; c = d \<rbrakk> \<Longrightarrow> f a c = f b d"
apply (erule ssubst)+
apply (rule refl)
done

lemma cong: "[| f = g; (x::'a) = y |] ==> f(x) = g(y)"
apply (erule subst)+
apply (rule refl)
done


subsubsection {*Equality of booleans -- iff*}

lemma iffI: assumes "P ==> Q" and "Q ==> P" shows "P=Q"
  by (iprover intro: iff [THEN mp, THEN mp] impI assms)

lemma iffD2: "[| P=Q; Q |] ==> P"
  by (erule ssubst)

lemma rev_iffD2: "[| Q; P=Q |] ==> P"
  by (erule iffD2)

lemma iffD1: "Q = P \<Longrightarrow> Q \<Longrightarrow> P"
  by (drule sym) (rule iffD2)

lemma rev_iffD1: "Q \<Longrightarrow> Q = P \<Longrightarrow> P"
  by (drule sym) (rule rev_iffD2)

lemma iffE:
  assumes major: "P=Q"
    and minor: "[| P --> Q; Q --> P |] ==> R"
  shows R
  by (iprover intro: minor impI major [THEN iffD2] major [THEN iffD1])


subsubsection {*True*}

lemma TrueI: "True"
  unfolding True_def by (rule refl)

lemma eqTrueI: "P ==> P = True"
  by (iprover intro: iffI TrueI)

lemma eqTrueE: "P = True ==> P"
  by (erule iffD2) (rule TrueI)


subsubsection {*Universal quantifier*}

lemma allI: assumes "!!x::'a. P(x)" shows "ALL x. P(x)"
  unfolding All_def by (iprover intro: ext eqTrueI assms)

lemma spec: "ALL x::'a. P(x) ==> P(x)"
apply (unfold All_def)
apply (rule eqTrueE)
apply (erule fun_cong)
done

lemma allE:
  assumes major: "ALL x. P(x)"
    and minor: "P(x) ==> R"
  shows R
  by (iprover intro: minor major [THEN spec])

lemma all_dupE:
  assumes major: "ALL x. P(x)"
    and minor: "[| P(x); ALL x. P(x) |] ==> R"
  shows R
  by (iprover intro: minor major major [THEN spec])


subsubsection {* False *}

text {*
  Depends upon @{text spec}; it is impossible to do propositional
  logic before quantifiers!
*}

lemma FalseE: "False ==> P"
  apply (unfold False_def)
  apply (erule spec)
  done

lemma False_neq_True: "False = True ==> P"
  by (erule eqTrueE [THEN FalseE])


subsubsection {* Negation *}

lemma notI:
  assumes "P ==> False"
  shows "~P"
  apply (unfold not_def)
  apply (iprover intro: impI assms)
  done

lemma False_not_True: "False ~= True"
  apply (rule notI)
  apply (erule False_neq_True)
  done

lemma True_not_False: "True ~= False"
  apply (rule notI)
  apply (drule sym)
  apply (erule False_neq_True)
  done

lemma notE: "[| ~P;  P |] ==> R"
  apply (unfold not_def)
  apply (erule mp [THEN FalseE])
  apply assumption
  done

lemma notI2: "(P \<Longrightarrow> \<not> Pa) \<Longrightarrow> (P \<Longrightarrow> Pa) \<Longrightarrow> \<not> P"
  by (erule notE [THEN notI]) (erule meta_mp)


subsubsection {*Implication*}

lemma impE:
  assumes "P-->Q" "P" "Q ==> R"
  shows "R"
by (iprover intro: assms mp)

(* Reduces Q to P-->Q, allowing substitution in P. *)
lemma rev_mp: "[| P;  P --> Q |] ==> Q"
by (iprover intro: mp)

lemma contrapos_nn:
  assumes major: "~Q"
      and minor: "P==>Q"
  shows "~P"
by (iprover intro: notI minor major [THEN notE])

(*not used at all, but we already have the other 3 combinations *)
lemma contrapos_pn:
  assumes major: "Q"
      and minor: "P ==> ~Q"
  shows "~P"
by (iprover intro: notI minor major notE)

lemma not_sym: "t ~= s ==> s ~= t"
  by (erule contrapos_nn) (erule sym)

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

(*still used in HOLCF*)
lemma rev_contrapos:
  assumes pq: "P ==> Q"
      and nq: "~Q"
  shows "~P"
apply (rule nq [THEN contrapos_nn])
apply (erule pq)
done

subsubsection {*Existential quantifier*}

lemma exI: "P x ==> EX x::'a. P x"
apply (unfold Ex_def)
apply (iprover intro: allI allE impI mp)
done

lemma exE:
  assumes major: "EX x::'a. P(x)"
      and minor: "!!x. P(x) ==> Q"
  shows "Q"
apply (rule major [unfolded Ex_def, THEN spec, THEN mp])
apply (iprover intro: impI [THEN allI] minor)
done


subsubsection {*Conjunction*}

lemma conjI: "[| P; Q |] ==> P&Q"
apply (unfold and_def)
apply (iprover intro: impI [THEN allI] mp)
done

lemma conjunct1: "[| P & Q |] ==> P"
apply (unfold and_def)
apply (iprover intro: impI dest: spec mp)
done

lemma conjunct2: "[| P & Q |] ==> Q"
apply (unfold and_def)
apply (iprover intro: impI dest: spec mp)
done

lemma conjE:
  assumes major: "P&Q"
      and minor: "[| P; Q |] ==> R"
  shows "R"
apply (rule minor)
apply (rule major [THEN conjunct1])
apply (rule major [THEN conjunct2])
done

lemma context_conjI:
  assumes "P" "P ==> Q" shows "P & Q"
by (iprover intro: conjI assms)


subsubsection {*Disjunction*}

lemma disjI1: "P ==> P|Q"
apply (unfold or_def)
apply (iprover intro: allI impI mp)
done

lemma disjI2: "Q ==> P|Q"
apply (unfold or_def)
apply (iprover intro: allI impI mp)
done

lemma disjE:
  assumes major: "P|Q"
      and minorP: "P ==> R"
      and minorQ: "Q ==> R"
  shows "R"
by (iprover intro: minorP minorQ impI
                 major [unfolded or_def, THEN spec, THEN mp, THEN mp])


subsubsection {*Classical logic*}

lemma classical:
  assumes prem: "~P ==> P"
  shows "P"
apply (rule True_or_False [THEN disjE, THEN eqTrueE])
apply assumption
apply (rule notI [THEN prem, THEN eqTrueI])
apply (erule subst)
apply assumption
done

lemmas ccontr = FalseE [THEN classical, standard]

(*notE with premises exchanged; it discharges ~R so that it can be used to
  make elimination rules*)
lemma rev_notE:
  assumes premp: "P"
      and premnot: "~R ==> ~P"
  shows "R"
apply (rule ccontr)
apply (erule notE [OF premnot premp])
done

(*Double negation law*)
lemma notnotD: "~~P ==> P"
apply (rule classical)
apply (erule notE)
apply assumption
done

lemma contrapos_pp:
  assumes p1: "Q"
      and p2: "~P ==> ~Q"
  shows "P"
by (iprover intro: classical p1 p2 notE)


subsubsection {*Unique existence*}

lemma ex1I:
  assumes "P a" "!!x. P(x) ==> x=a"
  shows "EX! x. P(x)"
by (unfold Ex1_def, iprover intro: assms exI conjI allI impI)

text{*Sometimes easier to use: the premises have no shared variables.  Safe!*}
lemma ex_ex1I:
  assumes ex_prem: "EX x. P(x)"
      and eq: "!!x y. [| P(x); P(y) |] ==> x=y"
  shows "EX! x. P(x)"
by (iprover intro: ex_prem [THEN exE] ex1I eq)

lemma ex1E:
  assumes major: "EX! x. P(x)"
      and minor: "!!x. [| P(x);  ALL y. P(y) --> y=x |] ==> R"
  shows "R"
apply (rule major [unfolded Ex1_def, THEN exE])
apply (erule conjE)
apply (iprover intro: minor)
done

lemma ex1_implies_ex: "EX! x. P x ==> EX x. P x"
apply (erule ex1E)
apply (rule exI)
apply assumption
done


subsubsection {*THE: definite description operator*}

lemma the_equality:
  assumes prema: "P a"
      and premx: "!!x. P x ==> x=a"