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Datei: Classical.thy Sprache: Isabelle

Original von: Isabelle^©

(*  Title:      HOL/ex/Classical.thy
    Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
    Copyright   1994  University of Cambridge
*)

section\<open>Classical Predicate Calculus Problems\<close>

theory Classical imports Main begin

subsection\<open>Traditional Classical Reasoner\<close>

text\<open>The machine "griffon" mentioned below is a 2.5GHz Power Mac G5.\<close>

text\<open>Taken from \<open>FOL/Classical.thy\<close>. When porting examples from
first-order logic, beware of the precedence of \<open>=\<close> versus \<open>\<leftrightarrow>\<close>.\<close>

lemma "(P \ Q \ R) \ (P\Q) \ (P\R)"
by blast

text\<open>If and only if\<close>

lemma "(P=Q) = (Q = (P::bool))"
by blast

lemma "\ (P = (\P))"
by blast

text\<open>Sample problems from
  F. J. Pelletier,
  Seventy-Five Problems for Testing Automatic Theorem Provers,
  J. Automated Reasoning 2 (1986), 191-216.
  Errata, JAR 4 (1988), 236-236.

The hardest problems -- judging by experience with several theorem provers,
including matrix ones -- are 34 and 43.
\<close>

subsubsection\<open>Pelletier's examples\<close>

text\<open>1\<close>
lemma "(P\Q) = (\Q \ \P)"
by blast

text\<open>2\<close>
lemma "(\ \ P) = P"
by blast

text\<open>3\<close>
lemma "\(P\Q) \ (Q\P)"
by blast

text\<open>4\<close>
lemma "(\P\Q) = (\Q \ P)"
by blast

text\<open>5\<close>
lemma "((P\Q)\(P\R)) \ (P\(Q\R))"
by blast

text\<open>6\<close>
lemma "P \ \ P"
by blast

text\<open>7\<close>
lemma "P \ \ \ \ P"
by blast

text\<open>8.  Peirce's law\<close>
lemma "((P\Q) \ P) \ P"
by blast

text\<open>9\<close>
lemma "((P\Q) \ (\P\Q) \ (P\ \Q)) \ \ (\P \ \Q)"
by blast

text\<open>10\<close>
lemma "(Q\R) \ (R\P\Q) \ (P\Q\R) \ (P=Q)"
by blast

text\<open>11.  Proved in each direction (incorrectly, says Pelletier!!)\<close>
lemma "P=(P::bool)"
by blast

text\<open>12.  "Dijkstra's law"\<close>
lemma "((P = Q) = R) = (P = (Q = R))"
by blast

text\<open>13.  Distributive law\<close>
lemma "(P \ (Q \ R)) = ((P \ Q) \ (P \ R))"
by blast

text\<open>14\<close>
lemma "(P = Q) = ((Q \ \P) \ (\Q\P))"
by blast

text\<open>15\<close>
lemma "(P \ Q) = (\P \ Q)"
by blast

text\<open>16\<close>
lemma "(P\Q) \ (Q\P)"
by blast

text\<open>17\<close>
lemma "((P \ (Q\R))\S) = ((\P \ Q \ S) \ (\P \ \R \ S))"
by blast

subsubsection\<open>Classical Logic: examples with quantifiers\<close>

lemma "(\x. P(x) \ Q(x)) = ((\x. P(x)) \ (\x. Q(x)))"
by blast

lemma "(\x. P\Q(x)) = (P \ (\x. Q(x)))"
by blast

lemma "(\x. P(x)\Q) = ((\x. P(x)) \ Q)"
by blast

lemma "((\x. P(x)) \ Q) = (\x. P(x) \ Q)"
by blast

text\<open>From Wishnu Prasetya\<close>
lemma "(\x. Q(x) \ R(x)) \ \R(a) \ (\x. \R(x) \ \Q(x) \ P(b) \ Q(b))
    \<longrightarrow> P(b) \<or> R(b)"
by blast

subsubsection\<open>Problems requiring quantifier duplication\<close>

text\<open>Theorem B of Peter Andrews, Theorem Proving via General Matings,
  JACM 28 (1981).\<close>
lemma "(\x. \y. P(x) = P(y)) \ ((\x. P(x)) = (\y. P(y)))"
by blast

text\<open>Needs multiple instantiation of the quantifier.\<close>
lemma "(\x. P(x)\P(f(x))) \ P(d)\P(f(f(f(d))))"
by blast

text\<open>Needs double instantiation of the quantifier\<close>
lemma "\x. P(x) \ P(a) \ P(b)"
by blast

lemma "\z. P(z) \ (\x. P(x))"
by blast

lemma "\x. (\y. P(y)) \ P(x)"
by blast

subsubsection\<open>Hard examples with quantifiers\<close>

text\<open>Problem 18\<close>
lemma "\y. \x. P(y)\P(x)"
by blast

text\<open>Problem 19\<close>
lemma "\x. \y z. (P(y)\Q(z)) \ (P(x)\Q(x))"
by blast

text\<open>Problem 20\<close>
lemma "(\x y. \z. \w. (P(x)\Q(y)\R(z)\S(w)))
    \<longrightarrow> (\<exists>x y. P(x) \<and> Q(y)) \<longrightarrow> (\<exists>z. R(z))"
by blast

text\<open>Problem 21\<close>
lemma "(\x. P\Q(x)) \ (\x. Q(x)\P) \ (\x. P=Q(x))"
by blast

text\<open>Problem 22\<close>
lemma "(\x. P = Q(x)) \ (P = (\x. Q(x)))"
by blast

text\<open>Problem 23\<close>
lemma "(\x. P \ Q(x)) = (P \ (\x. Q(x)))"
by blast

text\<open>Problem 24\<close>
lemma "\(\x. S(x)\Q(x)) \ (\x. P(x) \ Q(x)\R(x)) \
     (\<not>(\<exists>x. P(x)) \<longrightarrow> (\<exists>x. Q(x))) \<and> (\<forall>x. Q(x)\<or>R(x) \<longrightarrow> S(x))
    \<longrightarrow> (\<exists>x. P(x)\<and>R(x))"
by blast

text\<open>Problem 25\<close>
lemma "(\x. P(x)) \
        (\<forall>x. L(x) \<longrightarrow> \<not> (M(x) \<and> R(x))) \<and>
        (\<forall>x. P(x) \<longrightarrow> (M(x) \<and> L(x))) \<and>
        ((\<forall>x. P(x)\<longrightarrow>Q(x)) \<or> (\<exists>x. P(x)\<and>R(x)))
    \<longrightarrow> (\<exists>x. Q(x)\<and>P(x))"
by blast

text\<open>Problem 26\<close>
lemma "((\x. p(x)) = (\x. q(x))) \
      (\<forall>x. \<forall>y. p(x) \<and> q(y) \<longrightarrow> (r(x) = s(y)))
  \<longrightarrow> ((\<forall>x. p(x)\<longrightarrow>r(x)) = (\<forall>x. q(x)\<longrightarrow>s(x)))"
by blast

text\<open>Problem 27\<close>
lemma "(\x. P(x) \ \Q(x)) \
              (\<forall>x. P(x) \<longrightarrow> R(x)) \<and>
              (\<forall>x. M(x) \<and> L(x) \<longrightarrow> P(x)) \<and>
              ((\<exists>x. R(x) \<and> \<not> Q(x)) \<longrightarrow> (\<forall>x. L(x) \<longrightarrow> \<not> R(x)))
          \<longrightarrow> (\<forall>x. M(x) \<longrightarrow> \<not>L(x))"
by blast

text\<open>Problem 28.  AMENDED\<close>
lemma "(\x. P(x) \ (\x. Q(x))) \
        ((\<forall>x. Q(x)\<or>R(x)) \<longrightarrow> (\<exists>x. Q(x)\<and>S(x))) \<and>
        ((\<exists>x. S(x)) \<longrightarrow> (\<forall>x. L(x) \<longrightarrow> M(x)))
    \<longrightarrow> (\<forall>x. P(x) \<and> L(x) \<longrightarrow> M(x))"
by blast

text\<open>Problem 29.  Essentially the same as Principia Mathematica *11.71\<close>
lemma "(\x. F(x)) \ (\y. G(y))
    \<longrightarrow> ( ((\<forall>x. F(x)\<longrightarrow>H(x)) \<and> (\<forall>y. G(y)\<longrightarrow>J(y)))  =
          (\<forall>x y. F(x) \<and> G(y) \<longrightarrow> H(x) \<and> J(y)))"
by blast

text\<open>Problem 30\<close>
lemma "(\x. P(x) \ Q(x) \ \ R(x)) \
        (\<forall>x. (Q(x) \<longrightarrow> \<not> S(x)) \<longrightarrow> P(x) \<and> R(x))
    \<longrightarrow> (\<forall>x. S(x))"
by blast

text\<open>Problem 31\<close>
lemma "\(\x. P(x) \ (Q(x) \ R(x))) \
        (\<exists>x. L(x) \<and> P(x)) \<and>
        (\<forall>x. \<not> R(x) \<longrightarrow> M(x))
    \<longrightarrow> (\<exists>x. L(x) \<and> M(x))"
by blast

text\<open>Problem 32\<close>
lemma "(\x. P(x) \ (Q(x)\R(x))\S(x)) \
        (\<forall>x. S(x) \<and> R(x) \<longrightarrow> L(x)) \<and>
        (\<forall>x. M(x) \<longrightarrow> R(x))
    \<longrightarrow> (\<forall>x. P(x) \<and> M(x) \<longrightarrow> L(x))"
by blast

text\<open>Problem 33\<close>
lemma "(\x. P(a) \ (P(x)\P(b))\P(c)) =
     (\<forall>x. (\<not>P(a) \<or> P(x) \<or> P(c)) \<and> (\<not>P(a) \<or> \<not>P(b) \<or> P(c)))"
by blast

text\<open>Problem 34  AMENDED (TWICE!!)\<close>
text\<open>Andrews's challenge\<close>
lemma "((\x. \y. p(x) = p(y)) =
               ((\<exists>x. q(x)) = (\<forall>y. p(y))))   =
              ((\<exists>x. \<forall>y. q(x) = q(y))  =
               ((\<exists>x. p(x)) = (\<forall>y. q(y))))"
by blast

text\<open>Problem 35\<close>
lemma "\x y. P x y \ (\u v. P u v)"
by blast

text\<open>Problem 36\<close>
lemma "(\x. \y. J x y) \
        (\<forall>x. \<exists>y. G x y) \<and>
        (\<forall>x y. J x y \<or> G x y \<longrightarrow>
        (\<forall>z. J y z \<or> G y z \<longrightarrow> H x z))
    \<longrightarrow> (\<forall>x. \<exists>y. H x y)"
by blast

text\<open>Problem 37\<close>
lemma "(\z. \w. \x. \y.
           (P x z \<longrightarrow>P y w) \<and> P y z \<and> (P y w \<longrightarrow> (\<exists>u. Q u w))) \<and>
        (\<forall>x z. \<not>(P x z) \<longrightarrow> (\<exists>y. Q y z)) \<and>
        ((\<exists>x y. Q x y) \<longrightarrow> (\<forall>x. R x x))
    \<longrightarrow> (\<forall>x. \<exists>y. R x y)"
by blast

text\<open>Problem 38\<close>
lemma "(\x. p(a) \ (p(x) \ (\y. p(y) \ r x y)) \
           (\<exists>z. \<exists>w. p(z) \<and> r x w \<and> r w z))  =
     (\<forall>x. (\<not>p(a) \<or> p(x) \<or> (\<exists>z. \<exists>w. p(z) \<and> r x w \<and> r w z)) \<and>
           (\<not>p(a) \<or> \<not>(\<exists>y. p(y) \<and> r x y) \<or>
            (\<exists>z. \<exists>w. p(z) \<and> r x w \<and> r w z)))"
by blast (*beats fast!*)

text\<open>Problem 39\<close>
lemma "\ (\x. \y. F y x = (\ F y y))"
by blast

text\<open>Problem 40.  AMENDED\<close>
lemma "(\y. \x. F x y = F x x)
        \<longrightarrow>  \<not> (\<forall>x. \<exists>y. \<forall>z. F z y = (\<not> F z x))"
by blast

text\<open>Problem 41\<close>
lemma "(\z. \y. \x. f x y = (f x z \ \ f x x))
               \<longrightarrow> \<not> (\<exists>z. \<forall>x. f x z)"
by blast

text\<open>Problem 42\<close>
lemma "\ (\y. \x. p x y = (\ (\z. p x z \ p z x)))"
by blast

text\<open>Problem 43!!\<close>
lemma "(\x::'a. \y::'a. q x y = (\z. p z x \ (p z y)))
  \<longrightarrow> (\<forall>x. (\<forall>y. q x y \<longleftrightarrow> (q y x)))"
by blast

text\<open>Problem 44\<close>
lemma "(\x. f(x) \
              (\<exists>y. g(y) \<and> h x y \<and> (\<exists>y. g(y) \<and> \<not> h x y)))  \<and>
              (\<exists>x. j(x) \<and> (\<forall>y. g(y) \<longrightarrow> h x y))
              \<longrightarrow> (\<exists>x. j(x) \<and> \<not>f(x))"
by blast

text\<open>Problem 45\<close>
lemma "(\x. f(x) \ (\y. g(y) \ h x y \ j x y)
                      \<longrightarrow> (\<forall>y. g(y) \<and> h x y \<longrightarrow> k(y))) \<and>
     \<not> (\<exists>y. l(y) \<and> k(y)) \<and>
     (\<exists>x. f(x) \<and> (\<forall>y. h x y \<longrightarrow> l(y))
                \<and> (\<forall>y. g(y) \<and> h x y \<longrightarrow> j x y))
      \<longrightarrow> (\<exists>x. f(x) \<and> \<not> (\<exists>y. g(y) \<and> h x y))"
by blast

subsubsection\<open>Problems (mainly) involving equality or functions\<close>

text\<open>Problem 48\<close>
lemma "(a=b \ c=d) \ (a=c \ b=d) \ a=d \ b=c"
by blast

text\<open>Problem 49  NOT PROVED AUTOMATICALLY.
     Hard because it involves substitution for Vars
  the type constraint ensures that x,y,z have the same type as a,b,u.\<close>
lemma "(\x y::'a. \z. z=x \ z=y) \ P(a) \ P(b) \ (\a=b)
                \<longrightarrow> (\<forall>u::'a. P(u))"
by metis

text\<open>Problem 50.  (What has this to do with equality?)\<close>
lemma "(\x. P a x \ (\y. P x y)) \ (\x. \y. P x y)"
by blast

text\<open>Problem 51\<close>
lemma "(\z w. \x y. P x y = (x=z \ y=w)) \
     (\<exists>z. \<forall>x. \<exists>w. (\<forall>y. P x y = (y=w)) = (x=z))"
by blast

text\<open>Problem 52. Almost the same as 51.\<close>
lemma "(\z w. \x y. P x y = (x=z \ y=w)) \
     (\<exists>w. \<forall>y. \<exists>z. (\<forall>x. P x y = (x=z)) = (y=w))"
by blast

text\<open>Problem 55\<close>

text\<open>Non-equational version, from Manthey and Bry, CADE-9 (Springer, 1988).
  fast DISCOVERS who killed Agatha.\<close>
schematic_goal "lives(agatha) \ lives(butler) \ lives(charles) \
   (killed agatha agatha \<or> killed butler agatha \<or> killed charles agatha) \<and>
   (\<forall>x y. killed x y \<longrightarrow> hates x y \<and> \<not>richer x y) \<and>
   (\<forall>x. hates agatha x \<longrightarrow> \<not>hates charles x) \<and>
   (hates agatha agatha \<and> hates agatha charles) \<and>
   (\<forall>x. lives(x) \<and> \<not>richer x agatha \<longrightarrow> hates butler x) \<and>
   (\<forall>x. hates agatha x \<longrightarrow> hates butler x) \<and>
   (\<forall>x. \<not>hates x agatha \<or> \<not>hates x butler \<or> \<not>hates x charles) \<longrightarrow>
    killed ?who agatha"
by fast

text\<open>Problem 56\<close>
lemma "(\x. (\y. P(y) \ x=f(y)) \ P(x)) = (\x. P(x) \ P(f(x)))"
by blast

text\<open>Problem 57\<close>
lemma "P (f a b) (f b c) \ P (f b c) (f a c) \
     (\<forall>x y z. P x y \<and> P y z \<longrightarrow> P x z)    \<longrightarrow>   P (f a b) (f a c)"
by blast

text\<open>Problem 58  NOT PROVED AUTOMATICALLY\<close>
lemma "(\x y. f(x)=g(y)) \ (\x y. f(f(x))=f(g(y)))"
by (fast intro: arg_cong [of concl: f])

text\<open>Problem 59\<close>
lemma "(\x. P(x) = (\P(f(x)))) \ (\x. P(x) \ \P(f(x)))"
by blast

text\<open>Problem 60\<close>
lemma "\x. P x (f x) = (\y. (\z. P z y \ P z (f x)) \ P x y)"
by blast

text\<open>Problem 62 as corrected in JAR 18 (1997), page 135\<close>
lemma "(\x. p a \ (p x \ p(f x)) \ p(f(f x))) =
      (\<forall>x. (\<not> p a \<or> p x \<or> p(f(f x))) \<and>
              (\<not> p a \<or> \<not> p(f x) \<or> p(f(f x))))"
by blast

text\<open>From Davis, Obvious Logical Inferences, IJCAI-81, 530-531
  fast indeed copes!\<close>
lemma "(\x. F(x) \ \G(x) \ (\y. H(x,y) \ J(y))) \
       (\<exists>x. K(x) \<and> F(x) \<and> (\<forall>y. H(x,y) \<longrightarrow> K(y))) \<and>
       (\<forall>x. K(x) \<longrightarrow> \<not>G(x))  \<longrightarrow>  (\<exists>x. K(x) \<and> J(x))"
by fast

text\<open>From Rudnicki, Obvious Inferences, JAR 3 (1987), 383-393.
  It does seem obvious!\<close>
lemma "(\x. F(x) \ \G(x) \ (\y. H(x,y) \ J(y))) \
       (\<exists>x. K(x) \<and> F(x) \<and> (\<forall>y. H(x,y) \<longrightarrow> K(y)))  \<and>
       (\<forall>x. K(x) \<longrightarrow> \<not>G(x))   \<longrightarrow>   (\<exists>x. K(x) \<longrightarrow> \<not>G(x))"
by fast

text\<open>Attributed to Lewis Carroll by S. G. Pulman.  The first or last
assumption can be deleted.\<close>
lemma "(\x. honest(x) \ industrious(x) \ healthy(x)) \
      \<not> (\<exists>x. grocer(x) \<and> healthy(x)) \<and>
      (\<forall>x. industrious(x) \<and> grocer(x) \<longrightarrow> honest(x)) \<and>
      (\<forall>x. cyclist(x) \<longrightarrow> industrious(x)) \<and>
      (\<forall>x. \<not>healthy(x) \<and> cyclist(x) \<longrightarrow> \<not>honest(x))
      \<longrightarrow> (\<forall>x. grocer(x) \<longrightarrow> \<not>cyclist(x))"
by blast

lemma "(\x y. R(x,y) \ R(y,x)) \
       (\<forall>x y. S(x,y) \<and> S(y,x) \<longrightarrow> x=y) \<and>
       (\<forall>x y. R(x,y) \<longrightarrow> S(x,y))    \<longrightarrow>   (\<forall>x y. S(x,y) \<longrightarrow> R(x,y))"
by blast

subsection\<open>Model Elimination Prover\<close>

text\<open>Trying out meson with arguments\<close>
lemma "x < y \ y < z \ \ (z < (x::nat))"
by (meson order_less_irrefl order_less_trans)

text\<open>The "small example" from Bezem, Hendriks and de Nivelle,
Automatic Proof Construction in Type Theory Using Resolution,
JAR 29: 3-4 (2002), pages 253-275\<close>
lemma "(\x y z. R(x,y) \ R(y,z) \ R(x,z)) \
       (\<forall>x. \<exists>y. R(x,y)) \<longrightarrow>
       \<not> (\<forall>x. P x = (\<forall>y. R(x,y) \<longrightarrow> \<not> P y))"
by (tactic\<open>Meson.safe_best_meson_tac \<^context> 1\<close>)
    \<comment> \<open>In contrast, \<open>meson\<close> is SLOW: 7.6s on griffon\<close>

subsubsection\<open>Pelletier's examples\<close>
text\<open>1\<close>
lemma "(P \ Q) = (\Q \ \P)"
by blast

text\<open>2\<close>
lemma "(\ \ P) = P"
by blast

text\<open>3\<close>
lemma "\(P\Q) \ (Q\P)"
by blast

text\<open>4\<close>
lemma "(\P\Q) = (\Q \ P)"
by blast

text\<open>5\<close>
lemma "((P\Q)\(P\R)) \ (P\(Q\R))"
by blast

text\<open>6\<close>
lemma "P \ \ P"
by blast

text\<open>7\<close>
lemma "P \ \ \ \ P"
by blast

text\<open>8.  Peirce's law\<close>
lemma "((P\Q) \ P) \ P"
by blast

text\<open>9\<close>
lemma "((P\Q) \ (\P\Q) \ (P\ \Q)) \ \ (\P \ \Q)"
by blast

text\<open>10\<close>
lemma "(Q\R) \ (R\P\Q) \ (P\Q\R) \ (P=Q)"
by blast

text\<open>11.  Proved in each direction (incorrectly, says Pelletier!!)\<close>
lemma "P=(P::bool)"
by blast

text\<open>12.  "Dijkstra's law"\<close>
lemma "((P = Q) = R) = (P = (Q = R))"
by blast

text\<open>13.  Distributive law\<close>
lemma "(P \ (Q \ R)) = ((P \ Q) \ (P \ R))"
by blast

text\<open>14\<close>
lemma "(P = Q) = ((Q \ \P) \ (\Q\P))"
by blast

text\<open>15\<close>
lemma "(P \ Q) = (\P \ Q)"
by blast

text\<open>16\<close>
lemma "(P\Q) \ (Q\P)"
by blast

text\<open>17\<close>
lemma "((P \ (Q\R))\S) = ((\P \ Q \ S) \ (\P \ \R \ S))"
by blast

subsubsection\<open>Classical Logic: examples with quantifiers\<close>

lemma "(\x. P x \ Q x) = ((\x. P x) \ (\x. Q x))"
by blast

lemma "(\x. P \ Q x) = (P \ (\x. Q x))"
by blast

lemma "(\x. P x \ Q) = ((\x. P x) \ Q)"
by blast

lemma "((\x. P x) \ Q) = (\x. P x \ Q)"
by blast

lemma "(\x. P x \ P(f x)) \ P d \ P(f(f(f d)))"
by blast

text\<open>Needs double instantiation of EXISTS\<close>
lemma "\x. P x \ P a \ P b"
by blast

lemma "\z. P z \ (\x. P x)"
by blast

text\<open>From a paper by Claire Quigley\<close>
lemma "\y. ((P c \ Q y) \ (\z. \ Q z)) \ (\x. \ P x \ Q d)"
by fast

subsubsection\<open>Hard examples with quantifiers\<close>

text\<open>Problem 18\<close>
lemma "\y. \x. P y \ P x"
by blast

text\<open>Problem 19\<close>
lemma "\x. \y z. (P y \ Q z) \ (P x \ Q x)"
by blast

text\<open>Problem 20\<close>
lemma "(\x y. \z. \w. (P x \ Q y \ R z \ S w))
    \<longrightarrow> (\<exists>x y. P x \<and> Q y) \<longrightarrow> (\<exists>z. R z)"
by blast

text\<open>Problem 21\<close>
lemma "(\x. P \ Q x) \ (\x. Q x \ P) \ (\x. P=Q x)"
by blast

text\<open>Problem 22\<close>
lemma "(\x. P = Q x) \ (P = (\x. Q x))"
by blast

text\<open>Problem 23\<close>
lemma "(\x. P \ Q x) = (P \ (\x. Q x))"
by blast

text\<open>Problem 24\<close>  (*The first goal clause is useless*)
lemma "\(\x. S x \ Q x) \ (\x. P x \ Q x \ R x) \
      (\<not>(\<exists>x. P x) \<longrightarrow> (\<exists>x. Q x)) \<and> (\<forall>x. Q x \<or> R x \<longrightarrow> S x)
    \<longrightarrow> (\<exists>x. P x \<and> R x)"
by blast

text\<open>Problem 25\<close>
lemma "(\x. P x) \
      (\<forall>x. L x \<longrightarrow> \<not> (M x \<and> R x)) \<and>
      (\<forall>x. P x \<longrightarrow> (M x \<and> L x)) \<and>
      ((\<forall>x. P x \<longrightarrow> Q x) \<or> (\<exists>x. P x \<and> R x))
    \<longrightarrow> (\<exists>x. Q x \<and> P x)"
by blast

text\<open>Problem 26; has 24 Horn clauses\<close>
lemma "((\x. p x) = (\x. q x)) \
      (\<forall>x. \<forall>y. p x \<and> q y \<longrightarrow> (r x = s y))
  \<longrightarrow> ((\<forall>x. p x \<longrightarrow> r x) = (\<forall>x. q x \<longrightarrow> s x))"
by blast

text\<open>Problem 27; has 13 Horn clauses\<close>
lemma "(\x. P x \ \Q x) \
      (\<forall>x. P x \<longrightarrow> R x) \<and>
      (\<forall>x. M x \<and> L x \<longrightarrow> P x) \<and>
      ((\<exists>x. R x \<and> \<not> Q x) \<longrightarrow> (\<forall>x. L x \<longrightarrow> \<not> R x))
      \<longrightarrow> (\<forall>x. M x \<longrightarrow> \<not>L x)"
by blast

text\<open>Problem 28.  AMENDED; has 14 Horn clauses\<close>
lemma "(\x. P x \ (\x. Q x)) \
      ((\<forall>x. Q x \<or> R x) \<longrightarrow> (\<exists>x. Q x \<and> S x)) \<and>
      ((\<exists>x. S x) \<longrightarrow> (\<forall>x. L x \<longrightarrow> M x))
    \<longrightarrow> (\<forall>x. P x \<and> L x \<longrightarrow> M x)"
by blast

text\<open>Problem 29.  Essentially the same as Principia Mathematica *11.71.
      62 Horn clauses\<close>
lemma "(\x. F x) \ (\y. G y)
    \<longrightarrow> ( ((\<forall>x. F x \<longrightarrow> H x) \<and> (\<forall>y. G y \<longrightarrow> J y))  =
          (\<forall>x y. F x \<and> G y \<longrightarrow> H x \<and> J y))"
by blast

text\<open>Problem 30\<close>
lemma "(\x. P x \ Q x \ \ R x) \ (\x. (Q x \ \ S x) \ P x \ R x)
       \<longrightarrow> (\<forall>x. S x)"
by blast

text\<open>Problem 31; has 10 Horn clauses; first negative clauses is useless\<close>
lemma "\(\x. P x \ (Q x \ R x)) \
      (\<exists>x. L x \<and> P x) \<and>
      (\<forall>x. \<not> R x \<longrightarrow> M x)
    \<longrightarrow> (\<exists>x. L x \<and> M x)"
by blast

text\<open>Problem 32\<close>
lemma "(\x. P x \ (Q x \ R x)\S x) \
      (\<forall>x. S x \<and> R x \<longrightarrow> L x) \<and>
      (\<forall>x. M x \<longrightarrow> R x)
    \<longrightarrow> (\<forall>x. P x \<and> M x \<longrightarrow> L x)"
by blast

text\<open>Problem 33; has 55 Horn clauses\<close>
lemma "(\x. P a \ (P x \ P b)\P c) =
      (\<forall>x. (\<not>P a \<or> P x \<or> P c) \<and> (\<not>P a \<or> \<not>P b \<or> P c))"
by blast

text\<open>Problem 34: Andrews's challenge has 924 Horn clauses\<close>
lemma "((\x. \y. p x = p y) = ((\x. q x) = (\y. p y))) =
      ((\<exists>x. \<forall>y. q x = q y)  = ((\<exists>x. p x) = (\<forall>y. q y)))"
by blast

text\<open>Problem 35\<close>
lemma "\x y. P x y \ (\u v. P u v)"
by blast

text\<open>Problem 36; has 15 Horn clauses\<close>
lemma "(\x. \y. J x y) \ (\x. \y. G x y) \
       (\<forall>x y. J x y \<or> G x y \<longrightarrow> (\<forall>z. J y z \<or> G y z \<longrightarrow> H x z))
       \<longrightarrow> (\<forall>x. \<exists>y. H x y)"
by blast

text\<open>Problem 37; has 10 Horn clauses\<close>
lemma "(\z. \w. \x. \y.
           (P x z \<longrightarrow> P y w) \<and> P y z \<and> (P y w \<longrightarrow> (\<exists>u. Q u w))) \<and>
      (\<forall>x z. \<not>P x z \<longrightarrow> (\<exists>y. Q y z)) \<and>
      ((\<exists>x y. Q x y) \<longrightarrow> (\<forall>x. R x x))
    \<longrightarrow> (\<forall>x. \<exists>y. R x y)"
by blast \<comment> \<open>causes unification tracing messages\<close>

text\<open>Problem 38\<close>  text\<open>Quite hard: 422 Horn clauses!!\<close>
lemma "(\x. p a \ (p x \ (\y. p y \ r x y)) \
           (\<exists>z. \<exists>w. p z \<and> r x w \<and> r w z))  =
      (\<forall>x. (\<not>p a \<or> p x \<or> (\<exists>z. \<exists>w. p z \<and> r x w \<and> r w z)) \<and>
            (\<not>p a \<or> \<not>(\<exists>y. p y \<and> r x y) \<or>
             (\<exists>z. \<exists>w. p z \<and> r x w \<and> r w z)))"
by blast

text\<open>Problem 39\<close>
lemma "\ (\x. \y. F y x = (\F y y))"
by blast

text\<open>Problem 40.  AMENDED\<close>
lemma "(\y. \x. F x y = F x x)
      \<longrightarrow>  \<not> (\<forall>x. \<exists>y. \<forall>z. F z y = (\<not>F z x))"
by blast

text\<open>Problem 41\<close>
lemma "(\z. (\y. (\x. f x y = (f x z \ \ f x x))))
      \<longrightarrow> \<not> (\<exists>z. \<forall>x. f x z)"
by blast

text\<open>Problem 42\<close>
lemma "\ (\y. \x. p x y = (\ (\z. p x z \ p z x)))"
by blast

text\<open>Problem 43  NOW PROVED AUTOMATICALLY!!\<close>
lemma "(\x. \y. q x y = (\z. p z x = (p z y::bool)))
      \<longrightarrow> (\<forall>x. (\<forall>y. q x y = (q y x::bool)))"
by blast

text\<open>Problem 44: 13 Horn clauses; 7-step proof\<close>
lemma "(\x. f x \ (\y. g y \ h x y \ (\y. g y \ \ h x y))) \
       (\<exists>x. j x \<and> (\<forall>y. g y \<longrightarrow> h x y))
       \<longrightarrow> (\<exists>x. j x \<and> \<not>f x)"
by blast

text\<open>Problem 45; has 27 Horn clauses; 54-step proof\<close>
lemma "(\x. f x \ (\y. g y \ h x y \ j x y)
            \<longrightarrow> (\<forall>y. g y \<and> h x y \<longrightarrow> k y)) \<and>
      \<not> (\<exists>y. l y \<and> k y) \<and>
      (\<exists>x. f x \<and> (\<forall>y. h x y \<longrightarrow> l y)
                \<and> (\<forall>y. g y \<and> h x y \<longrightarrow> j x y))
      \<longrightarrow> (\<exists>x. f x \<and> \<not> (\<exists>y. g y \<and> h x y))"
by blast

text\<open>Problem 46; has 26 Horn clauses; 21-step proof\<close>
lemma "(\x. f x \ (\y. f y \ h y x \ g y) \ g x) \
       ((\<exists>x. f x \<and> \<not>g x) \<longrightarrow>
       (\<exists>x. f x \<and> \<not>g x \<and> (\<forall>y. f y \<and> \<not>g y \<longrightarrow> j x y))) \<and>
       (\<forall>x y. f x \<and> f y \<and> h x y \<longrightarrow> \<not>j y x)
       \<longrightarrow> (\<forall>x. f x \<longrightarrow> g x)"
by blast

text\<open>Problem 47.  Schubert's Steamroller.
      26 clauses; 63 Horn clauses.
      87094 inferences so far.  Searching to depth 36\<close>
lemma "(\x. wolf x \ animal x) \ (\x. wolf x) \
       (\<forall>x. fox x \<longrightarrow> animal x) \<and> (\<exists>x. fox x) \<and>
       (\<forall>x. bird x \<longrightarrow> animal x) \<and> (\<exists>x. bird x) \<and>
       (\<forall>x. caterpillar x \<longrightarrow> animal x) \<and> (\<exists>x. caterpillar x) \<and>
       (\<forall>x. snail x \<longrightarrow> animal x) \<and> (\<exists>x. snail x) \<and>
       (\<forall>x. grain x \<longrightarrow> plant x) \<and> (\<exists>x. grain x) \<and>
       (\<forall>x. animal x \<longrightarrow>
             ((\<forall>y. plant y \<longrightarrow> eats x y)  \<or>
              (\<forall>y. animal y \<and> smaller_than y x \<and>
                    (\<exists>z. plant z \<and> eats y z) \<longrightarrow> eats x y))) \<and>
       (\<forall>x y. bird y \<and> (snail x \<or> caterpillar x) \<longrightarrow> smaller_than x y) \<and>
       (\<forall>x y. bird x \<and> fox y \<longrightarrow> smaller_than x y) \<and>
       (\<forall>x y. fox x \<and> wolf y \<longrightarrow> smaller_than x y) \<and>
       (\<forall>x y. wolf x \<and> (fox y \<or> grain y) \<longrightarrow> \<not>eats x y) \<and>
       (\<forall>x y. bird x \<and> caterpillar y \<longrightarrow> eats x y) \<and>
       (\<forall>x y. bird x \<and> snail y \<longrightarrow> \<not>eats x y) \<and>
       (\<forall>x. (caterpillar x \<or> snail x) \<longrightarrow> (\<exists>y. plant y \<and> eats x y))
       \<longrightarrow> (\<exists>x y. animal x \<and> animal y \<and> (\<exists>z. grain z \<and> eats y z \<and> eats x y))"
by (tactic\<open>Meson.safe_best_meson_tac \<^context> 1\<close>)
    \<comment> \<open>Nearly twice as fast as \<open>meson\<close>,
        which performs iterative deepening rather than best-first search\<close>

text\<open>The Los problem. Circulated by John Harrison\<close>
lemma "(\x y z. P x y \ P y z \ P x z) \
       (\<forall>x y z. Q x y \<and> Q y z \<longrightarrow> Q x z) \<and>
       (\<forall>x y. P x y \<longrightarrow> P y x) \<and>
       (\<forall>x y. P x y \<or> Q x y)
       \<longrightarrow> (\<forall>x y. P x y) \<or> (\<forall>x y. Q x y)"
by meson

text\<open>A similar example, suggested by Johannes Schumann and
credited to Pelletier\<close>
lemma "(\x y z. P x y \ P y z \ P x z) \
       (\<forall>x y z. Q x y \<longrightarrow> Q y z \<longrightarrow> Q x z) \<longrightarrow>
       (\<forall>x y. Q x y \<longrightarrow> Q y x) \<longrightarrow>  (\<forall>x y. P x y \<or> Q x y) \<longrightarrow>
       (\<forall>x y. P x y) \<or> (\<forall>x y. Q x y)"
by meson

text\<open>Problem 50.  What has this to do with equality?\<close>
lemma "(\x. P a x \ (\y. P x y)) \ (\x. \y. P x y)"
by blast

text\<open>Problem 54: NOT PROVED\<close>
lemma "(\y::'a. \z. \x. F x z = (x=y)) \
      \<not> (\<exists>w. \<forall>x. F x w = (\<forall>u. F x u \<longrightarrow> (\<exists>y. F y u \<and> \<not> (\<exists>z. F z u \<and> F z y))))"
oops

text\<open>Problem 55\<close>

text\<open>Non-equational version, from Manthey and Bry, CADE-9 (Springer, 1988).
  \<open>meson\<close> cannot report who killed Agatha.\<close>
lemma "lives agatha \ lives butler \ lives charles \
       (killed agatha agatha \<or> killed butler agatha \<or> killed charles agatha) \<and>
       (\<forall>x y. killed x y \<longrightarrow> hates x y \<and> \<not>richer x y) \<and>
       (\<forall>x. hates agatha x \<longrightarrow> \<not>hates charles x) \<and>
       (hates agatha agatha \<and> hates agatha charles) \<and>
       (\<forall>x. lives x \<and> \<not>richer x agatha \<longrightarrow> hates butler x) \<and>
       (\<forall>x. hates agatha x \<longrightarrow> hates butler x) \<and>
       (\<forall>x. \<not>hates x agatha \<or> \<not>hates x butler \<or> \<not>hates x charles) \<longrightarrow>
       (\<exists>x. killed x agatha)"
by meson

text\<open>Problem 57\<close>
lemma "P (f a b) (f b c) \ P (f b c) (f a c) \
      (\<forall>x y z. P x y \<and> P y z \<longrightarrow> P x z)    \<longrightarrow>   P (f a b) (f a c)"
by blast

text\<open>Problem 58: Challenge found on info-hol\<close>
lemma "\P Q R x. \v w. \y z. P x \ Q y \ (P v \ R w) \ (R z \ Q v)"
by blast

text\<open>Problem 59\<close>
lemma "(\x. P x = (\P(f x))) \ (\x. P x \ \P(f x))"
by blast

text\<open>Problem 60\<close>
lemma "\x. P x (f x) = (\y. (\z. P z y \ P z (f x)) \ P x y)"
by blast

text\<open>Problem 62 as corrected in JAR 18 (1997), page 135\<close>
lemma "(\x. p a \ (p x \ p(f x)) \ p(f(f x))) =
       (\<forall>x. (\<not> p a \<or> p x \<or> p(f(f x))) \<and>
            (\<not> p a \<or> \<not> p(f x) \<or> p(f(f x))))"
by blast

text\<open>Charles Morgan's problems\<close>
context
  fixes T i n
  assumes a: "\x y. T(i x(i y x))"
    and b: "\x y z. T(i (i x (i y z)) (i (i x y) (i x z)))"
    and c: "\x y. T(i (i (n x) (n y)) (i y x))"
    and c': "\x y. T(i (i y x) (i (n x) (n y)))"
    and d: "\x y. T(i x y) \ T x \ T y"
begin

lemma "\x. T(i x x)"
  using a b d by blast

lemma "\x. T(i x (n(n x)))" \ \Problem 66\
  using a b c d by metis

lemma "\x. T(i (n(n x)) x)" \ \Problem 67\
  using a b c d by meson \<comment> \<open>4.9s on griffon. 51061 inferences, depth 21\<close>

lemma "\x. T(i x (n(n x)))" \ \Problem 68: not proved. Listed as satisfiable in TPTP (LCL078-1)\
  using a b c' d oops

end

text\<open>Problem 71, as found in TPTP (SYN007+1.005)\<close>
lemma "p1 = (p2 = (p3 = (p4 = (p5 = (p1 = (p2 = (p3 = (p4 = p5))))))))"
  by blast

end

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