src/HOL/Meson.thy
author blanchet
Mon Oct 04 21:49:07 2010 +0200 (2010-10-04)
changeset 39941 02fcd9cd1eac
child 39944 03ac1fbc76d3
permissions -rw-r--r--
move Meson to Plain
     1 (*  Title:      HOL/Meson.thy
     2     Author:     Lawrence C Paulson, Tobias Nipkow
     3     Copyright   2001  University of Cambridge
     4 *)
     5 
     6 header {* MESON Proof Procedure (Model Elimination) *}
     7 
     8 theory Meson
     9 imports Nat
    10 uses ("Tools/Meson/meson.ML")
    11      ("Tools/Meson/meson_clausify.ML")
    12 begin
    13 
    14 section {* Negation Normal Form *}
    15 
    16 text {* de Morgan laws *}
    17 
    18 lemma meson_not_conjD: "~(P&Q) ==> ~P | ~Q"
    19   and meson_not_disjD: "~(P|Q) ==> ~P & ~Q"
    20   and meson_not_notD: "~~P ==> P"
    21   and meson_not_allD: "!!P. ~(\<forall>x. P(x)) ==> \<exists>x. ~P(x)"
    22   and meson_not_exD: "!!P. ~(\<exists>x. P(x)) ==> \<forall>x. ~P(x)"
    23   by fast+
    24 
    25 text {* Removal of @{text "-->"} and @{text "<->"} (positive and
    26 negative occurrences) *}
    27 
    28 lemma meson_imp_to_disjD: "P-->Q ==> ~P | Q"
    29   and meson_not_impD: "~(P-->Q) ==> P & ~Q"
    30   and meson_iff_to_disjD: "P=Q ==> (~P | Q) & (~Q | P)"
    31   and meson_not_iffD: "~(P=Q) ==> (P | Q) & (~P | ~Q)"
    32     -- {* Much more efficient than @{prop "(P & ~Q) | (Q & ~P)"} for computing CNF *}
    33   and meson_not_refl_disj_D: "x ~= x | P ==> P"
    34   by fast+
    35 
    36 
    37 section {* Pulling out the existential quantifiers *}
    38 
    39 text {* Conjunction *}
    40 
    41 lemma meson_conj_exD1: "!!P Q. (\<exists>x. P(x)) & Q ==> \<exists>x. P(x) & Q"
    42   and meson_conj_exD2: "!!P Q. P & (\<exists>x. Q(x)) ==> \<exists>x. P & Q(x)"
    43   by fast+
    44 
    45 
    46 text {* Disjunction *}
    47 
    48 lemma meson_disj_exD: "!!P Q. (\<exists>x. P(x)) | (\<exists>x. Q(x)) ==> \<exists>x. P(x) | Q(x)"
    49   -- {* DO NOT USE with forall-Skolemization: makes fewer schematic variables!! *}
    50   -- {* With ex-Skolemization, makes fewer Skolem constants *}
    51   and meson_disj_exD1: "!!P Q. (\<exists>x. P(x)) | Q ==> \<exists>x. P(x) | Q"
    52   and meson_disj_exD2: "!!P Q. P | (\<exists>x. Q(x)) ==> \<exists>x. P | Q(x)"
    53   by fast+
    54 
    55 lemma meson_disj_assoc: "(P|Q)|R ==> P|(Q|R)"
    56   and meson_disj_comm: "P|Q ==> Q|P"
    57   and meson_disj_FalseD1: "False|P ==> P"
    58   and meson_disj_FalseD2: "P|False ==> P"
    59   by fast+
    60 
    61 
    62 text{* Generation of contrapositives *}
    63 
    64 text{*Inserts negated disjunct after removing the negation; P is a literal.
    65   Model elimination requires assuming the negation of every attempted subgoal,
    66   hence the negated disjuncts.*}
    67 lemma make_neg_rule: "~P|Q ==> ((~P==>P) ==> Q)"
    68 by blast
    69 
    70 text{*Version for Plaisted's "Postive refinement" of the Meson procedure*}
    71 lemma make_refined_neg_rule: "~P|Q ==> (P ==> Q)"
    72 by blast
    73 
    74 text{*@{term P} should be a literal*}
    75 lemma make_pos_rule: "P|Q ==> ((P==>~P) ==> Q)"
    76 by blast
    77 
    78 text{*Versions of @{text make_neg_rule} and @{text make_pos_rule} that don't
    79 insert new assumptions, for ordinary resolution.*}
    80 
    81 lemmas make_neg_rule' = make_refined_neg_rule
    82 
    83 lemma make_pos_rule': "[|P|Q; ~P|] ==> Q"
    84 by blast
    85 
    86 text{* Generation of a goal clause -- put away the final literal *}
    87 
    88 lemma make_neg_goal: "~P ==> ((~P==>P) ==> False)"
    89 by blast
    90 
    91 lemma make_pos_goal: "P ==> ((P==>~P) ==> False)"
    92 by blast
    93 
    94 
    95 section {* Lemmas for Forward Proof *}
    96 
    97 text{*There is a similarity to congruence rules*}
    98 
    99 (*NOTE: could handle conjunctions (faster?) by
   100     nf(th RS conjunct2) RS (nf(th RS conjunct1) RS conjI) *)
   101 lemma conj_forward: "[| P'&Q';  P' ==> P;  Q' ==> Q |] ==> P&Q"
   102 by blast
   103 
   104 lemma disj_forward: "[| P'|Q';  P' ==> P;  Q' ==> Q |] ==> P|Q"
   105 by blast
   106 
   107 (*Version of @{text disj_forward} for removal of duplicate literals*)
   108 lemma disj_forward2:
   109     "[| P'|Q';  P' ==> P;  [| Q'; P==>False |] ==> Q |] ==> P|Q"
   110 apply blast 
   111 done
   112 
   113 lemma all_forward: "[| \<forall>x. P'(x);  !!x. P'(x) ==> P(x) |] ==> \<forall>x. P(x)"
   114 by blast
   115 
   116 lemma ex_forward: "[| \<exists>x. P'(x);  !!x. P'(x) ==> P(x) |] ==> \<exists>x. P(x)"
   117 by blast
   118 
   119 
   120 section {* Clausification helper *}
   121 
   122 lemma TruepropI: "P \<equiv> Q \<Longrightarrow> Trueprop P \<equiv> Trueprop Q"
   123 by simp
   124 
   125 
   126 text{* Combinator translation helpers *}
   127 
   128 definition COMBI :: "'a \<Rightarrow> 'a" where
   129 [no_atp]: "COMBI P = P"
   130 
   131 definition COMBK :: "'a \<Rightarrow> 'b \<Rightarrow> 'a" where
   132 [no_atp]: "COMBK P Q = P"
   133 
   134 definition COMBB :: "('b => 'c) \<Rightarrow> ('a => 'b) \<Rightarrow> 'a \<Rightarrow> 'c" where [no_atp]:
   135 "COMBB P Q R = P (Q R)"
   136 
   137 definition COMBC :: "('a \<Rightarrow> 'b \<Rightarrow> 'c) \<Rightarrow> 'b \<Rightarrow> 'a \<Rightarrow> 'c" where
   138 [no_atp]: "COMBC P Q R = P R Q"
   139 
   140 definition COMBS :: "('a \<Rightarrow> 'b \<Rightarrow> 'c) \<Rightarrow> ('a \<Rightarrow> 'b) \<Rightarrow> 'a \<Rightarrow> 'c" where
   141 [no_atp]: "COMBS P Q R = P R (Q R)"
   142 
   143 lemma abs_S [no_atp]: "\<lambda>x. (f x) (g x) \<equiv> COMBS f g"
   144 apply (rule eq_reflection)
   145 apply (rule ext) 
   146 apply (simp add: COMBS_def) 
   147 done
   148 
   149 lemma abs_I [no_atp]: "\<lambda>x. x \<equiv> COMBI"
   150 apply (rule eq_reflection)
   151 apply (rule ext) 
   152 apply (simp add: COMBI_def) 
   153 done
   154 
   155 lemma abs_K [no_atp]: "\<lambda>x. y \<equiv> COMBK y"
   156 apply (rule eq_reflection)
   157 apply (rule ext) 
   158 apply (simp add: COMBK_def) 
   159 done
   160 
   161 lemma abs_B [no_atp]: "\<lambda>x. a (g x) \<equiv> COMBB a g"
   162 apply (rule eq_reflection)
   163 apply (rule ext) 
   164 apply (simp add: COMBB_def) 
   165 done
   166 
   167 lemma abs_C [no_atp]: "\<lambda>x. (f x) b \<equiv> COMBC f b"
   168 apply (rule eq_reflection)
   169 apply (rule ext) 
   170 apply (simp add: COMBC_def) 
   171 done
   172 
   173 
   174 section {* Skolemization helpers *}
   175 
   176 definition skolem :: "'a \<Rightarrow> 'a" where
   177 [no_atp]: "skolem = (\<lambda>x. x)"
   178 
   179 lemma skolem_COMBK_iff: "P \<longleftrightarrow> skolem (COMBK P (i\<Colon>nat))"
   180 unfolding skolem_def COMBK_def by (rule refl)
   181 
   182 lemmas skolem_COMBK_I = iffD1 [OF skolem_COMBK_iff]
   183 lemmas skolem_COMBK_D = iffD2 [OF skolem_COMBK_iff]
   184 
   185 
   186 section {* Meson package *}
   187 
   188 ML {*
   189 structure Meson_Choices = Named_Thms
   190 (
   191   val name = "meson_choice"
   192   val description = "choice axioms for MESON's (and Metis's) skolemizer"
   193 )
   194 *}
   195 
   196 use "Tools/Meson/meson.ML"
   197 use "Tools/Meson/meson_clausify.ML"
   198 
   199 setup {*
   200   Meson_Choices.setup
   201   #> Meson.setup
   202   #> Meson_Clausify.setup
   203 *}
   204 
   205 end