YES We show the termination of the TRS R: cond(true(),x) -> cond(odd(x),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(x)) p2: cond#(true(),x) -> odd#(x) p3: cond#(true(),x) -> p#(x) p4: odd#(s(s(x))) -> odd#(x) and R consists of: r1: cond(true(),x) -> cond(odd(x),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} {p4} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: cond#(true(),x) -> cond#(odd(x),p(x)) and R consists of: r1: cond(true(),x) -> cond(odd(x),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 r1, r2, r3, r4, r5, r6 Take the reduction pair: generalized weighted path order (>=MG, >MG) base order 1: max/plus interpretation on natural numbers: cond#_A(x1,x2) = max{x1 - 3, x2 + 3} true_A = 13 odd_A(x1) = x1 + 2 p_A(x1) = max{6, x1 - 4} cond_A(x1,x2) = 0 |0|_A = 5 false_A = 4 s_A(x1) = max{14, x1 + 7} base order 2: precedence: cond# > p = s > true > odd = |0| > cond = false partial status: pi(cond#) = [] pi(true) = [] pi(odd) = [1] pi(p) = [] pi(cond) = [] pi(|0|) = [] pi(false) = [] pi(s) = [1] The following rules are removed: p1 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(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, r6 Take the reduction pair: generalized weighted path order (>=MG, >MG) base order 1: max/plus interpretation on natural numbers: odd#_A(x1) = max{7, x1 + 6} s_A(x1) = max{7, x1 + 6} odd_A(x1) = max{3, x1 - 8} |0|_A = 1 false_A = 0 true_A = 2 p_A(x1) = max{3, x1 - 5} base order 2: precedence: s > odd = p > odd# = true > |0| > false partial status: pi(odd#) = [1] pi(s) = [1] pi(odd) = [] pi(|0|) = [] pi(false) = [] pi(true) = [] pi(p) = [] The following rules are removed: p1 Then no dependency pair remains.