YES We show the termination of the TRS R: cond(true(),x) -> cond(odd(x),p(p(p(x)))) odd(|0|()) -> false() odd(s(|0|())) -> true() odd(s(s(x))) -> odd(x) p(|0|()) -> |0|() p(s(x)) -> x -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: cond#(true(),x) -> cond#(odd(x),p(p(p(x)))) p2: cond#(true(),x) -> odd#(x) p3: cond#(true(),x) -> p#(p(p(x))) p4: cond#(true(),x) -> p#(p(x)) p5: cond#(true(),x) -> p#(x) p6: odd#(s(s(x))) -> odd#(x) and R consists of: r1: cond(true(),x) -> cond(odd(x),p(p(p(x)))) r2: odd(|0|()) -> false() r3: odd(s(|0|())) -> true() r4: odd(s(s(x))) -> odd(x) r5: p(|0|()) -> |0|() r6: p(s(x)) -> x The estimated dependency graph contains the following SCCs: {p1} {p6} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: cond#(true(),x) -> cond#(odd(x),p(p(p(x)))) and R consists of: r1: cond(true(),x) -> cond(odd(x),p(p(p(x)))) r2: odd(|0|()) -> false() r3: odd(s(|0|())) -> true() r4: odd(s(s(x))) -> odd(x) r5: p(|0|()) -> |0|() r6: p(s(x)) -> x The set of usable rules consists of r2, r3, r4, r5, r6 Take the reduction pair: weighted path order base order: max/plus interpretations on natural numbers: cond#_A(x1,x2) = max{x1 + 3, x2 + 19} true_A = 21 odd_A(x1) = x1 + 15 p_A(x1) = max{4, x1 - 6} |0|_A = 3 false_A = 2 s_A(x1) = max{22, x1 + 7} precedence: cond# = true = odd = p = |0| = false = s partial status: pi(cond#) = [1] pi(true) = [] pi(odd) = [1] pi(p) = [] pi(|0|) = [] pi(false) = [] pi(s) = [1] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains. -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: odd#(s(s(x))) -> odd#(x) and R consists of: r1: cond(true(),x) -> cond(odd(x),p(p(p(x)))) r2: odd(|0|()) -> false() r3: odd(s(|0|())) -> true() r4: odd(s(s(x))) -> odd(x) r5: p(|0|()) -> |0|() r6: p(s(x)) -> x The set of usable rules consists of (no rules) Take the monotone reduction pair: weighted path order base order: max/plus interpretations on natural numbers: odd#_A(x1) = x1 + 5 s_A(x1) = x1 + 2 precedence: odd# = s partial status: pi(odd#) = [1] pi(s) = [1] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.