0.06/0.11 % Problem : theBenchmark.p : TPTP v0.0.0. Released v0.0.0. 0.06/0.12 % Command : twee %s --tstp --casc --quiet --explain-encoding --conditional-encoding if --smaller --drop-non-horn 0.11/0.33 % Computer : n013.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 10:26:16 EDT 2019 0.11/0.33 % CPUTime : 0.36/0.56 % SZS status Unsatisfiable 0.36/0.56 0.36/0.56 % SZS output start Proof 0.36/0.56 Take the following subset of the input axioms: 0.36/0.56 fof(b_definition, axiom, ![X, Y, Z]: apply(apply(apply(b, X), Y), Z)=apply(X, apply(Y, Z))). 0.36/0.56 fof(prove_strong_fixed_point, negated_conjecture, apply(fixed_pt, apply(strong_fixed_point, fixed_pt))!=apply(strong_fixed_point, fixed_pt)). 0.36/0.56 fof(strong_fixed_point, axiom, strong_fixed_point=apply(apply(b, apply(w, w)), apply(apply(b, w), apply(apply(b, b), b)))). 0.36/0.56 fof(w_definition, axiom, ![X, Y]: apply(apply(X, Y), Y)=apply(apply(w, X), Y)). 0.36/0.56 0.36/0.56 Now clausify the problem and encode Horn clauses using encoding 3 of 0.36/0.56 http://www.cse.chalmers.se/~nicsma/papers/horn.pdf. 0.36/0.56 We repeatedly replace C & s=t => u=v by the two clauses: 0.36/0.56 fresh(y, y, x1...xn) = u 0.36/0.56 C => fresh(s, t, x1...xn) = v 0.36/0.56 where fresh is a fresh function symbol and x1..xn are the free 0.36/0.56 variables of u and v. 0.36/0.56 A predicate p(X) is encoded as p(X)=true (this is sound, because the 0.36/0.56 input problem has no model of domain size 1). 0.36/0.56 0.36/0.56 The encoding turns the above axioms into the following unit equations and goals: 0.36/0.56 0.36/0.56 Axiom 1 (strong_fixed_point): strong_fixed_point = apply(apply(b, apply(w, w)), apply(apply(b, w), apply(apply(b, b), b))). 0.36/0.56 Axiom 2 (w_definition): apply(apply(X, Y), Y) = apply(apply(w, X), Y). 0.36/0.56 Axiom 3 (b_definition): apply(apply(apply(b, X), Y), Z) = apply(X, apply(Y, Z)). 0.36/0.56 0.36/0.56 Lemma 4: apply(apply(w, w), apply(w, apply(b, apply(b, X)))) = apply(strong_fixed_point, X). 0.36/0.56 Proof: 0.36/0.56 apply(apply(w, w), apply(w, apply(b, apply(b, X)))) 0.36/0.56 = { by axiom 3 (b_definition) } 0.36/0.56 apply(apply(w, w), apply(w, apply(apply(apply(b, b), b), X))) 0.36/0.56 = { by axiom 3 (b_definition) } 0.36/0.56 apply(apply(w, w), apply(apply(apply(b, w), apply(apply(b, b), b)), X)) 0.36/0.56 = { by axiom 3 (b_definition) } 0.36/0.56 apply(apply(apply(b, apply(w, w)), apply(apply(b, w), apply(apply(b, b), b))), X) 0.36/0.56 = { by axiom 1 (strong_fixed_point) } 0.36/0.56 apply(strong_fixed_point, X) 0.36/0.56 0.36/0.56 Goal 1 (prove_strong_fixed_point): apply(fixed_pt, apply(strong_fixed_point, fixed_pt)) = apply(strong_fixed_point, fixed_pt). 0.36/0.56 Proof: 0.36/0.56 apply(fixed_pt, apply(strong_fixed_point, fixed_pt)) 0.36/0.56 = { by lemma 4 } 0.36/0.56 apply(fixed_pt, apply(apply(w, w), apply(w, apply(b, apply(b, fixed_pt))))) 0.36/0.56 = { by axiom 2 (w_definition) } 0.36/0.56 apply(fixed_pt, apply(apply(w, apply(w, apply(b, apply(b, fixed_pt)))), apply(w, apply(b, apply(b, fixed_pt))))) 0.36/0.56 = { by axiom 2 (w_definition) } 0.36/0.56 apply(fixed_pt, apply(apply(apply(w, apply(b, apply(b, fixed_pt))), apply(w, apply(b, apply(b, fixed_pt)))), apply(w, apply(b, apply(b, fixed_pt))))) 0.36/0.56 = { by axiom 3 (b_definition) } 0.36/0.56 apply(apply(apply(b, fixed_pt), apply(apply(w, apply(b, apply(b, fixed_pt))), apply(w, apply(b, apply(b, fixed_pt))))), apply(w, apply(b, apply(b, fixed_pt)))) 0.36/0.56 = { by axiom 3 (b_definition) } 0.36/0.56 apply(apply(apply(apply(b, apply(b, fixed_pt)), apply(w, apply(b, apply(b, fixed_pt)))), apply(w, apply(b, apply(b, fixed_pt)))), apply(w, apply(b, apply(b, fixed_pt)))) 0.36/0.56 = { by axiom 2 (w_definition) } 0.36/0.56 apply(apply(apply(w, apply(b, apply(b, fixed_pt))), apply(w, apply(b, apply(b, fixed_pt)))), apply(w, apply(b, apply(b, fixed_pt)))) 0.36/0.56 = { by axiom 2 (w_definition) } 0.36/0.56 apply(apply(w, apply(w, apply(b, apply(b, fixed_pt)))), apply(w, apply(b, apply(b, fixed_pt)))) 0.36/0.56 = { by axiom 2 (w_definition) } 0.36/0.56 apply(apply(w, w), apply(w, apply(b, apply(b, fixed_pt)))) 0.36/0.56 = { by lemma 4 } 0.36/0.56 apply(strong_fixed_point, fixed_pt) 0.36/0.56 % SZS output end Proof 0.36/0.56 0.36/0.56 RESULT: Unsatisfiable (the axioms are contradictory). 0.36/0.56 EOF