src/HOL/Hilbert_Choice.thy
author paulson
Fri Sep 26 10:34:57 2003 +0200 (2003-09-26)
changeset 14208 144f45277d5a
parent 14115 65ec3f73d00b
child 14399 dc677b35e54f
permissions -rw-r--r--
misc tidying
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(*  Title:      HOL/Hilbert_Choice.thy
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    ID:         $Id$
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    Author:     Lawrence C Paulson
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    Copyright   2001  University of Cambridge
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*)
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header {* Hilbert's epsilon-operator and everything to do with the Axiom of Choice *}
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theory Hilbert_Choice = NatArith
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files ("Hilbert_Choice_lemmas.ML") ("meson_lemmas.ML") ("Tools/meson.ML") ("Tools/specification_package.ML"):
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subsection {* Hilbert's epsilon *}
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consts
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  Eps           :: "('a => bool) => 'a"
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syntax (input)
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  "_Eps"        :: "[pttrn, bool] => 'a"    ("(3\<epsilon>_./ _)" [0, 10] 10)
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syntax (HOL)
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  "_Eps"        :: "[pttrn, bool] => 'a"    ("(3@ _./ _)" [0, 10] 10)
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syntax
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  "_Eps"        :: "[pttrn, bool] => 'a"    ("(3SOME _./ _)" [0, 10] 10)
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translations
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  "SOME x. P" == "Eps (%x. P)"
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print_translation {*
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(* to avoid eta-contraction of body *)
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[("Eps", fn [Abs abs] =>
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     let val (x,t) = atomic_abs_tr' abs
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     in Syntax.const "_Eps" $ x $ t end)]
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*}
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axioms
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  someI: "P (x::'a) ==> P (SOME x. P x)"
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constdefs
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  inv :: "('a => 'b) => ('b => 'a)"
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  "inv(f :: 'a => 'b) == %y. SOME x. f x = y"
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  Inv :: "'a set => ('a => 'b) => ('b => 'a)"
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  "Inv A f == %x. SOME y. y : A & f y = x"
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use "Hilbert_Choice_lemmas.ML"
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declare someI_ex [elim?];
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lemma Inv_mem: "[| f ` A = B;  x \<in> B |] ==> Inv A f x \<in> A"
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apply (unfold Inv_def)
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apply (fast intro: someI2)
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done
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lemma tfl_some: "\<forall>P x. P x --> P (Eps P)"
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  -- {* dynamically-scoped fact for TFL *}
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  by (blast intro: someI)
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subsection {* Least value operator *}
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constdefs
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  LeastM :: "['a => 'b::ord, 'a => bool] => 'a"
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  "LeastM m P == SOME x. P x & (ALL y. P y --> m x <= m y)"
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syntax
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  "_LeastM" :: "[pttrn, 'a => 'b::ord, bool] => 'a"    ("LEAST _ WRT _. _" [0, 4, 10] 10)
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translations
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  "LEAST x WRT m. P" == "LeastM m (%x. P)"
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lemma LeastMI2:
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  "P x ==> (!!y. P y ==> m x <= m y)
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    ==> (!!x. P x ==> \<forall>y. P y --> m x \<le> m y ==> Q x)
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    ==> Q (LeastM m P)"
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  apply (unfold LeastM_def)
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  apply (rule someI2_ex, blast, blast)
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  done
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lemma LeastM_equality:
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  "P k ==> (!!x. P x ==> m k <= m x)
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    ==> m (LEAST x WRT m. P x) = (m k::'a::order)"
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  apply (rule LeastMI2, assumption, blast)
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  apply (blast intro!: order_antisym)
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  done
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lemma wf_linord_ex_has_least:
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  "wf r ==> ALL x y. ((x,y):r^+) = ((y,x)~:r^*) ==> P k
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    ==> EX x. P x & (!y. P y --> (m x,m y):r^*)"
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  apply (drule wf_trancl [THEN wf_eq_minimal [THEN iffD1]])
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  apply (drule_tac x = "m`Collect P" in spec, force)
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  done
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lemma ex_has_least_nat:
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    "P k ==> EX x. P x & (ALL y. P y --> m x <= (m y::nat))"
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  apply (simp only: pred_nat_trancl_eq_le [symmetric])
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  apply (rule wf_pred_nat [THEN wf_linord_ex_has_least])
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   apply (simp add: less_eq not_le_iff_less pred_nat_trancl_eq_le, assumption)
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  done
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lemma LeastM_nat_lemma:
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    "P k ==> P (LeastM m P) & (ALL y. P y --> m (LeastM m P) <= (m y::nat))"
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  apply (unfold LeastM_def)
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  apply (rule someI_ex)
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  apply (erule ex_has_least_nat)
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  done
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lemmas LeastM_natI = LeastM_nat_lemma [THEN conjunct1, standard]
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lemma LeastM_nat_le: "P x ==> m (LeastM m P) <= (m x::nat)"
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by (rule LeastM_nat_lemma [THEN conjunct2, THEN spec, THEN mp], assumption, assumption)
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subsection {* Greatest value operator *}
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constdefs
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  GreatestM :: "['a => 'b::ord, 'a => bool] => 'a"
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  "GreatestM m P == SOME x. P x & (ALL y. P y --> m y <= m x)"
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  Greatest :: "('a::ord => bool) => 'a"    (binder "GREATEST " 10)
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  "Greatest == GreatestM (%x. x)"
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syntax
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  "_GreatestM" :: "[pttrn, 'a=>'b::ord, bool] => 'a"
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      ("GREATEST _ WRT _. _" [0, 4, 10] 10)
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translations
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  "GREATEST x WRT m. P" == "GreatestM m (%x. P)"
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lemma GreatestMI2:
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  "P x ==> (!!y. P y ==> m y <= m x)
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    ==> (!!x. P x ==> \<forall>y. P y --> m y \<le> m x ==> Q x)
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    ==> Q (GreatestM m P)"
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  apply (unfold GreatestM_def)
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  apply (rule someI2_ex, blast, blast)
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  done
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lemma GreatestM_equality:
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 "P k ==> (!!x. P x ==> m x <= m k)
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    ==> m (GREATEST x WRT m. P x) = (m k::'a::order)"
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  apply (rule_tac m = m in GreatestMI2, assumption, blast)
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  apply (blast intro!: order_antisym)
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  done
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lemma Greatest_equality:
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  "P (k::'a::order) ==> (!!x. P x ==> x <= k) ==> (GREATEST x. P x) = k"
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  apply (unfold Greatest_def)
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  apply (erule GreatestM_equality, blast)
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  done
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lemma ex_has_greatest_nat_lemma:
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  "P k ==> ALL x. P x --> (EX y. P y & ~ ((m y::nat) <= m x))
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    ==> EX y. P y & ~ (m y < m k + n)"
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  apply (induct_tac n, force)
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  apply (force simp add: le_Suc_eq)
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  done
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lemma ex_has_greatest_nat:
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  "P k ==> ALL y. P y --> m y < b
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    ==> EX x. P x & (ALL y. P y --> (m y::nat) <= m x)"
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  apply (rule ccontr)
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  apply (cut_tac P = P and n = "b - m k" in ex_has_greatest_nat_lemma)
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    apply (subgoal_tac [3] "m k <= b", auto)
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  done
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lemma GreatestM_nat_lemma:
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  "P k ==> ALL y. P y --> m y < b
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    ==> P (GreatestM m P) & (ALL y. P y --> (m y::nat) <= m (GreatestM m P))"
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  apply (unfold GreatestM_def)
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  apply (rule someI_ex)
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  apply (erule ex_has_greatest_nat, assumption)
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  done
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lemmas GreatestM_natI = GreatestM_nat_lemma [THEN conjunct1, standard]
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lemma GreatestM_nat_le:
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  "P x ==> ALL y. P y --> m y < b
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    ==> (m x::nat) <= m (GreatestM m P)"
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  apply (blast dest: GreatestM_nat_lemma [THEN conjunct2, THEN spec])
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  done
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text {* \medskip Specialization to @{text GREATEST}. *}
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lemma GreatestI: "P (k::nat) ==> ALL y. P y --> y < b ==> P (GREATEST x. P x)"
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  apply (unfold Greatest_def)
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  apply (rule GreatestM_natI, auto)
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  done
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lemma Greatest_le:
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    "P x ==> ALL y. P y --> y < b ==> (x::nat) <= (GREATEST x. P x)"
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  apply (unfold Greatest_def)
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  apply (rule GreatestM_nat_le, auto)
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  done
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subsection {* The Meson proof procedure *}
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subsubsection {* Negation Normal Form *}
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text {* de Morgan laws *}
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lemma meson_not_conjD: "~(P&Q) ==> ~P | ~Q"
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  and meson_not_disjD: "~(P|Q) ==> ~P & ~Q"
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  and meson_not_notD: "~~P ==> P"
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  and meson_not_allD: "!!P. ~(ALL x. P(x)) ==> EX x. ~P(x)"
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  and meson_not_exD: "!!P. ~(EX x. P(x)) ==> ALL x. ~P(x)"
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  by fast+
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text {* Removal of @{text "-->"} and @{text "<->"} (positive and
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negative occurrences) *}
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lemma meson_imp_to_disjD: "P-->Q ==> ~P | Q"
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  and meson_not_impD: "~(P-->Q) ==> P & ~Q"
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  and meson_iff_to_disjD: "P=Q ==> (~P | Q) & (~Q | P)"
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  and meson_not_iffD: "~(P=Q) ==> (P | Q) & (~P | ~Q)"
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    -- {* Much more efficient than @{prop "(P & ~Q) | (Q & ~P)"} for computing CNF *}
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  by fast+
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subsubsection {* Pulling out the existential quantifiers *}
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text {* Conjunction *}
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lemma meson_conj_exD1: "!!P Q. (EX x. P(x)) & Q ==> EX x. P(x) & Q"
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  and meson_conj_exD2: "!!P Q. P & (EX x. Q(x)) ==> EX x. P & Q(x)"
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  by fast+
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text {* Disjunction *}
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lemma meson_disj_exD: "!!P Q. (EX x. P(x)) | (EX x. Q(x)) ==> EX x. P(x) | Q(x)"
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  -- {* DO NOT USE with forall-Skolemization: makes fewer schematic variables!! *}
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  -- {* With ex-Skolemization, makes fewer Skolem constants *}
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  and meson_disj_exD1: "!!P Q. (EX x. P(x)) | Q ==> EX x. P(x) | Q"
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  and meson_disj_exD2: "!!P Q. P | (EX x. Q(x)) ==> EX x. P | Q(x)"
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  by fast+
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subsubsection {* Generating clauses for the Meson Proof Procedure *}
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text {* Disjunctions *}
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lemma meson_disj_assoc: "(P|Q)|R ==> P|(Q|R)"
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  and meson_disj_comm: "P|Q ==> Q|P"
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  and meson_disj_FalseD1: "False|P ==> P"
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  and meson_disj_FalseD2: "P|False ==> P"
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  by fast+
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use "meson_lemmas.ML"
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use "Tools/meson.ML"
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setup meson_setup
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use "Tools/specification_package.ML"
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end