YES (VAR X) (RULES f(g(X)) -> g(f(f(X))) f(h(X)) -> h(g(X)) ) The TRS is an overlay system and all critical pairs are trivial, thus termination of innermost rewriting is equivalent to termination of rewriting. Proving termination of innermost rewriting for nestrec: -> Dependency pairs: nF_f(g(X)) -> nF_f(f(X)) nF_f(g(X)) -> nF_f(X) -> Proof of termination for nestrec_1: -> -> Dependency pairs in cycle: nF_f(g(X)) -> nF_f(f(X)) nF_f(g(X)) -> nF_f(X) UsableRules: f(g(X)) -> g(f(f(X))) f(h(X)) -> h(g(X)) Polynomial Interpretation: [f](X) = X [g](X) = X + 1 [h](X) = 0 [nF_f](X) = X TIME: 4.5158e-2 -> -> Dependency pairs in cycle: nF_f(g(X)) -> nF_f(f(X)) UsableRules: f(g(X)) -> g(f(f(X))) f(h(X)) -> h(g(X)) Polynomial Interpretation: [f](X) = X [g](X) = X + 1 [h](X) = 0 [nF_f](X) = X TIME: 4.0816e-2 SETTINGS: Base ordering: Polynomial ordering Proof mode: SCCs in DG + base ordering Upper bound for coeffs: 1 Rationals below 1 for all non-replacing args: No Polynomial interpretation: Linear Coeffs in polynomials: No rationals Delta: automatic Termination was proved succesfully.