NO Prover = TRS(tech=GUIDED_UNF_TRIPLES, nb_unfoldings=unlimited, unfold_variables=false, max_nb_coefficients=12, max_nb_unfolded_rules=-1, strategy=LEFTMOST_NE) ** BEGIN proof argument ** The following rule was generated while unfolding the analyzed TRS: [iteration = 3] f(_0,h(h(_1))) -> f(h(h(f(f(h(a),a),f(h(a),_1)))),_0) Let l be the left-hand side and r be the right-hand side of this rule. Let p = epsilon, theta1 = {_0->h(h(_2))} and theta2 = {_1->_2, _2->f(f(h(a),a),f(h(a),_1))}. We have r|p = f(h(h(f(f(h(a),a),f(h(a),_1)))),_0) and theta2(theta1(l)) = theta1(r|p). Hence, the term theta1(l) = f(h(h(_2)),h(h(_1))) loops w.r.t. the analyzed TRS. ** END proof argument ** ** BEGIN proof description ** ## Searching for a generalized rewrite rule (a rule whose right-hand side contains a variable that does not occur in the left-hand side)... No generalized rewrite rule found! ## Applying the DP framework... ## Round 1: ## DP problem: Dependency pairs = [f^#(_0,h(_1)) -> f^#(f(h(a),_1),_0), f^#(_0,h(_1)) -> f^#(h(a),_1)] TRS = {f(_0,h(_1)) -> h(f(f(h(a),_1),_0))} ## Trying with homeomorphic embeddings... Failed! ## Trying with polynomial interpretations... Failed! ## Trying with lexicographic path orders... Failed! ## Trying to prove nontermination by unfolding the dependency pairs with the rules of the TRS # max_depth=20, unfold_variables=false: # Iteration 0: nontermination not detected, 2 unfolded rules generated. # Iteration 1: nontermination not detected, 5 unfolded rules generated. # Iteration 2: nontermination not detected, 8 unfolded rules generated. # Iteration 3: nontermination detected, 5 unfolded rules generated. Here is the successful unfolding. Let IR be the TRS under analysis. L0 = f^#(_0,h(_1)) -> f^#(f(h(a),_1),_0) [trans] is in U_IR^0. We build a unit triple from L0. ==> L1 = f^#(_0,h(_1)) -> f^#(f(h(a),_1),_0) [unit] is in U_IR^1. Let p1 = [0]. We unfold the rule of L1 forwards at position p1 with the rule f(_0,h(_1)) -> h(f(f(h(a),_1),_0)). ==> L2 = f^#(_0,h(h(_1))) -> f^#(h(f(f(h(a),_1),h(a))),_0) [unit] is in U_IR^2. Let p2 = [0, 0]. We unfold the rule of L2 forwards at position p2 with the rule f(_0,h(_1)) -> h(f(f(h(a),_1),_0)). ==> L3 = f^#(_0,h(h(_1))) -> f^#(h(h(f(f(h(a),a),f(h(a),_1)))),_0) [unit] is in U_IR^3. This DP problem is infinite. ** END proof description ** Proof stopped at iteration 3 Number of unfolded rules generated by this proof = 20 Number of unfolded rules generated by all the parallel proofs = 169