0.00/0.12 % Problem : theBenchmark.p : TPTP v0.0.0. Released v0.0.0. 0.12/0.12 % Command : twee %s --tstp --casc --quiet --explain-encoding --conditional-encoding if --smaller --drop-non-horn 0.12/0.33 % Computer : n004.cluster.edu 0.12/0.33 % Model : x86_64 x86_64 0.12/0.33 % CPU : Intel(R) Xeon(R) CPU E5-2620 v4 @ 2.10GHz 0.12/0.33 % Memory : 8042.1875MB 0.12/0.33 % OS : Linux 3.10.0-693.el7.x86_64 0.12/0.33 % CPULimit : 180 0.12/0.33 % DateTime : Thu Aug 29 11:26:08 EDT 2019 0.12/0.34 % CPUTime : 0.55/0.73 % SZS status Unsatisfiable 0.55/0.73 0.55/0.73 % SZS output start Proof 0.55/0.73 Take the following subset of the input axioms: 0.55/0.73 fof(b_definition, axiom, ![X, Y, Z]: apply(apply(apply(b, X), Y), Z)=apply(X, apply(Y, Z))). 0.55/0.73 fof(prove_strong_fixed_point, negated_conjecture, apply(strong_fixed_point, fixed_pt)!=apply(fixed_pt, apply(strong_fixed_point, fixed_pt))). 0.55/0.73 fof(strong_fixed_point, axiom, strong_fixed_point=apply(apply(b, apply(apply(b, apply(w, w)), apply(apply(b, apply(b, w)), b))), b)). 0.55/0.73 fof(w_definition, axiom, ![X, Y]: apply(apply(X, Y), Y)=apply(apply(w, X), Y)). 0.55/0.73 0.55/0.73 Now clausify the problem and encode Horn clauses using encoding 3 of 0.55/0.73 http://www.cse.chalmers.se/~nicsma/papers/horn.pdf. 0.55/0.73 We repeatedly replace C & s=t => u=v by the two clauses: 0.55/0.73 fresh(y, y, x1...xn) = u 0.55/0.73 C => fresh(s, t, x1...xn) = v 0.55/0.73 where fresh is a fresh function symbol and x1..xn are the free 0.55/0.73 variables of u and v. 0.55/0.73 A predicate p(X) is encoded as p(X)=true (this is sound, because the 0.55/0.73 input problem has no model of domain size 1). 0.55/0.73 0.55/0.73 The encoding turns the above axioms into the following unit equations and goals: 0.55/0.73 0.55/0.73 Axiom 1 (w_definition): apply(apply(X, Y), Y) = apply(apply(w, X), Y). 0.55/0.73 Axiom 2 (strong_fixed_point): strong_fixed_point = apply(apply(b, apply(apply(b, apply(w, w)), apply(apply(b, apply(b, w)), b))), b). 0.55/0.73 Axiom 3 (b_definition): apply(apply(apply(b, X), Y), Z) = apply(X, apply(Y, Z)). 0.55/0.73 0.55/0.73 Lemma 4: apply(apply(w, w), apply(apply(b, w), apply(b, apply(b, X)))) = apply(strong_fixed_point, X). 0.55/0.73 Proof: 0.55/0.73 apply(apply(w, w), apply(apply(b, w), apply(b, apply(b, X)))) 0.55/0.73 = { by axiom 3 (b_definition) } 0.55/0.73 apply(apply(w, w), apply(apply(apply(b, apply(b, w)), b), apply(b, X))) 0.55/0.73 = { by axiom 3 (b_definition) } 0.55/0.73 apply(apply(apply(b, apply(w, w)), apply(apply(b, apply(b, w)), b)), apply(b, X)) 0.55/0.73 = { by axiom 3 (b_definition) } 0.55/0.73 apply(apply(apply(b, apply(apply(b, apply(w, w)), apply(apply(b, apply(b, w)), b))), b), X) 0.55/0.73 = { by axiom 2 (strong_fixed_point) } 0.55/0.73 apply(strong_fixed_point, X) 0.55/0.73 0.55/0.73 Goal 1 (prove_strong_fixed_point): apply(strong_fixed_point, fixed_pt) = apply(fixed_pt, apply(strong_fixed_point, fixed_pt)). 0.55/0.73 Proof: 0.55/0.73 apply(strong_fixed_point, fixed_pt) 0.55/0.73 = { by lemma 4 } 0.55/0.73 apply(apply(w, w), apply(apply(b, w), apply(b, apply(b, fixed_pt)))) 0.55/0.73 = { by axiom 1 (w_definition) } 0.55/0.73 apply(apply(w, apply(apply(b, w), apply(b, apply(b, fixed_pt)))), apply(apply(b, w), apply(b, apply(b, fixed_pt)))) 0.55/0.73 = { by axiom 1 (w_definition) } 0.55/0.73 apply(apply(apply(apply(b, w), apply(b, apply(b, fixed_pt))), apply(apply(b, w), apply(b, apply(b, fixed_pt)))), apply(apply(b, w), apply(b, apply(b, fixed_pt)))) 0.55/0.73 = { by axiom 3 (b_definition) } 0.55/0.73 apply(apply(w, apply(apply(b, apply(b, fixed_pt)), apply(apply(b, w), apply(b, apply(b, fixed_pt))))), apply(apply(b, w), apply(b, apply(b, fixed_pt)))) 0.55/0.73 = { by axiom 1 (w_definition) } 0.55/0.73 apply(apply(apply(apply(b, apply(b, fixed_pt)), apply(apply(b, w), apply(b, apply(b, fixed_pt)))), apply(apply(b, w), apply(b, apply(b, fixed_pt)))), apply(apply(b, w), apply(b, apply(b, fixed_pt)))) 0.55/0.73 = { by axiom 3 (b_definition) } 0.55/0.73 apply(apply(apply(b, fixed_pt), apply(apply(apply(b, w), apply(b, apply(b, fixed_pt))), apply(apply(b, w), apply(b, apply(b, fixed_pt))))), apply(apply(b, w), apply(b, apply(b, fixed_pt)))) 0.55/0.73 = { by axiom 3 (b_definition) } 0.55/0.73 apply(fixed_pt, apply(apply(apply(apply(b, w), apply(b, apply(b, fixed_pt))), apply(apply(b, w), apply(b, apply(b, fixed_pt)))), apply(apply(b, w), apply(b, apply(b, fixed_pt))))) 0.55/0.73 = { by axiom 1 (w_definition) } 0.55/0.73 apply(fixed_pt, apply(apply(w, apply(apply(b, w), apply(b, apply(b, fixed_pt)))), apply(apply(b, w), apply(b, apply(b, fixed_pt))))) 0.55/0.73 = { by axiom 1 (w_definition) } 0.55/0.73 apply(fixed_pt, apply(apply(w, w), apply(apply(b, w), apply(b, apply(b, fixed_pt))))) 0.55/0.73 = { by lemma 4 } 0.55/0.73 apply(fixed_pt, apply(strong_fixed_point, fixed_pt)) 0.55/0.73 % SZS output end Proof 0.55/0.73 0.55/0.73 RESULT: Unsatisfiable (the axioms are contradictory). 0.55/0.73 EOF