0.11/0.11 % Problem : theBenchmark.p : TPTP v0.0.0. Released v0.0.0. 0.11/0.12 % Command : twee %s --tstp --casc --quiet --explain-encoding --conditional-encoding if --smaller --drop-non-horn 0.11/0.33 % Computer : n018.cluster.edu 0.11/0.33 % Model : x86_64 x86_64 0.11/0.33 % CPU : Intel(R) Xeon(R) CPU E5-2620 v4 @ 2.10GHz 0.11/0.33 % Memory : 8042.1875MB 0.11/0.33 % OS : Linux 3.10.0-693.el7.x86_64 0.11/0.33 % CPULimit : 180 0.11/0.33 % DateTime : Thu Aug 29 13:17:36 EDT 2019 0.11/0.33 % CPUTime : 3.06/3.25 % SZS status Unsatisfiable 3.06/3.25 3.06/3.25 % SZS output start Proof 3.06/3.25 Take the following subset of the input axioms: 3.06/3.25 fof(k_definition, axiom, ![Y, X]: apply(apply(k, X), Y)=X). 3.06/3.25 fof(prove_fixed_point, negated_conjecture, ![Y]: apply(Y, f(Y))!=apply(f(Y), apply(Y, f(Y)))). 3.06/3.25 fof(s_definition, axiom, ![Y, X, Z]: apply(apply(X, Z), apply(Y, Z))=apply(apply(apply(s, X), Y), Z)). 3.06/3.25 3.06/3.25 Now clausify the problem and encode Horn clauses using encoding 3 of 3.06/3.25 http://www.cse.chalmers.se/~nicsma/papers/horn.pdf. 3.06/3.25 We repeatedly replace C & s=t => u=v by the two clauses: 3.06/3.25 fresh(y, y, x1...xn) = u 3.06/3.25 C => fresh(s, t, x1...xn) = v 3.06/3.25 where fresh is a fresh function symbol and x1..xn are the free 3.06/3.25 variables of u and v. 3.06/3.25 A predicate p(X) is encoded as p(X)=true (this is sound, because the 3.06/3.25 input problem has no model of domain size 1). 3.06/3.25 3.06/3.25 The encoding turns the above axioms into the following unit equations and goals: 3.06/3.25 3.06/3.25 Axiom 1 (s_definition): apply(apply(X, Y), apply(Z, Y)) = apply(apply(apply(s, X), Z), Y). 3.06/3.25 Axiom 2 (k_definition): apply(apply(k, X), Y) = X. 3.06/3.25 3.06/3.25 Lemma 3: apply(apply(apply(s, k), Y), X) = X. 3.06/3.25 Proof: 3.06/3.25 apply(apply(apply(s, k), Y), X) 3.06/3.25 = { by axiom 1 (s_definition) } 3.06/3.25 apply(apply(k, X), apply(Y, X)) 3.06/3.25 = { by axiom 2 (k_definition) } 3.06/3.25 X 3.06/3.25 3.06/3.25 Lemma 4: apply(apply(X, Z), Z) = apply(apply(apply(s, X), apply(apply(s, k), ?)), Z). 3.06/3.25 Proof: 3.06/3.25 apply(apply(X, Z), Z) 3.06/3.25 = { by lemma 3 } 3.06/3.25 apply(apply(X, Z), apply(apply(apply(s, k), ?), Z)) 3.06/3.25 = { by axiom 1 (s_definition) } 3.06/3.25 apply(apply(apply(s, X), apply(apply(s, k), ?)), Z) 3.06/3.25 3.06/3.25 Lemma 5: apply(apply(apply(s, apply(s, k)), X), Y) = apply(X, Y). 3.06/3.25 Proof: 3.06/3.25 apply(apply(apply(s, apply(s, k)), X), Y) 3.06/3.25 = { by axiom 1 (s_definition) } 3.06/3.25 apply(apply(apply(s, k), Y), apply(X, Y)) 3.06/3.25 = { by lemma 3 } 3.06/3.25 apply(X, Y) 3.06/3.25 3.06/3.25 Goal 1 (prove_fixed_point): apply(X, f(X)) = apply(f(X), apply(X, f(X))). 3.06/3.25 The goal is true when: 3.06/3.25 X = apply(apply(s, apply(s, k)), apply(apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))), apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))))) 3.06/3.25 3.06/3.25 Proof: 3.06/3.25 apply(apply(apply(s, apply(s, k)), apply(apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))), apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))))), f(apply(apply(s, apply(s, k)), apply(apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))), apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))))))) 3.06/3.25 = { by lemma 5 } 3.06/3.25 apply(apply(apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))), apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k))))))), f(apply(apply(s, apply(s, k)), apply(apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))), apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))))))) 3.06/3.25 = { by axiom 1 (s_definition) } 3.06/3.25 apply(apply(apply(apply(s, apply(s, apply(k, apply(s, apply(s, apply(s, k)))))), apply(apply(s, k), apply(s, apply(k, apply(s, apply(s, apply(s, k))))))), apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k))))))), f(apply(apply(s, apply(s, k)), apply(apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))), apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))))))) 3.06/3.25 = { by axiom 1 (s_definition) } 3.06/3.25 apply(apply(apply(apply(s, apply(k, apply(s, apply(s, apply(s, k))))), apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k))))))), apply(apply(apply(s, k), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))), apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))))), f(apply(apply(s, apply(s, k)), apply(apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))), apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))))))) 3.06/3.25 = { by lemma 3 } 3.06/3.25 apply(apply(apply(apply(s, apply(k, apply(s, apply(s, apply(s, k))))), apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k))))))), apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k))))))), f(apply(apply(s, apply(s, k)), apply(apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))), apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))))))) 3.06/3.25 = { by axiom 1 (s_definition) } 3.06/3.25 apply(apply(apply(apply(k, apply(s, apply(s, apply(s, k)))), apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k))))))), apply(apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))), apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))))), f(apply(apply(s, apply(s, k)), apply(apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))), apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))))))) 3.06/3.25 = { by axiom 2 (k_definition) } 3.06/3.25 apply(apply(apply(s, apply(s, apply(s, k))), apply(apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))), apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))))), f(apply(apply(s, apply(s, k)), apply(apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))), apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))))))) 3.06/3.25 = { by axiom 1 (s_definition) } 3.06/3.25 apply(apply(apply(s, apply(s, k)), f(apply(apply(s, apply(s, k)), apply(apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))), apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))))))), apply(apply(apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))), apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k))))))), f(apply(apply(s, apply(s, k)), apply(apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))), apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k))))))))))) 3.06/3.25 = { by lemma 5 } 3.06/3.25 apply(f(apply(apply(s, apply(s, k)), apply(apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))), apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k))))))))), apply(apply(apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))), apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k))))))), f(apply(apply(s, apply(s, k)), apply(apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))), apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k))))))))))) 3.06/3.25 = { by lemma 5 } 3.06/3.25 apply(f(apply(apply(s, apply(s, k)), apply(apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))), apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k))))))))), apply(apply(apply(s, apply(s, k)), apply(apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))), apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))))), f(apply(apply(s, apply(s, k)), apply(apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k)))))), apply(apply(apply(s, s), apply(s, k)), apply(s, apply(k, apply(s, apply(s, apply(s, k))))))))))) 3.06/3.25 % SZS output end Proof 3.06/3.25 3.06/3.25 RESULT: Unsatisfiable (the axioms are contradictory). 3.06/3.25 EOF