YES We show the termination of the TRS R: cond1(true(),x) -> cond2(even(x),x) cond2(true(),x) -> cond1(neq(x,|0|()),div2(x)) cond2(false(),x) -> cond1(neq(x,|0|()),p(x)) neq(|0|(),|0|()) -> false() neq(|0|(),s(x)) -> true() neq(s(x),|0|()) -> true() neq(s(x),s(y())) -> neq(x,y()) even(|0|()) -> true() even(s(|0|())) -> false() even(s(s(x))) -> even(x) div2(|0|()) -> |0|() div2(s(|0|())) -> |0|() div2(s(s(x))) -> s(div2(x)) p(|0|()) -> |0|() p(s(x)) -> x -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: cond1#(true(),x) -> cond2#(even(x),x) p2: cond1#(true(),x) -> even#(x) p3: cond2#(true(),x) -> cond1#(neq(x,|0|()),div2(x)) p4: cond2#(true(),x) -> neq#(x,|0|()) p5: cond2#(true(),x) -> div2#(x) p6: cond2#(false(),x) -> cond1#(neq(x,|0|()),p(x)) p7: cond2#(false(),x) -> neq#(x,|0|()) p8: cond2#(false(),x) -> p#(x) p9: neq#(s(x),s(y())) -> neq#(x,y()) p10: even#(s(s(x))) -> even#(x) p11: div2#(s(s(x))) -> div2#(x) and R consists of: r1: cond1(true(),x) -> cond2(even(x),x) r2: cond2(true(),x) -> cond1(neq(x,|0|()),div2(x)) r3: cond2(false(),x) -> cond1(neq(x,|0|()),p(x)) r4: neq(|0|(),|0|()) -> false() r5: neq(|0|(),s(x)) -> true() r6: neq(s(x),|0|()) -> true() r7: neq(s(x),s(y())) -> neq(x,y()) r8: even(|0|()) -> true() r9: even(s(|0|())) -> false() r10: even(s(s(x))) -> even(x) r11: div2(|0|()) -> |0|() r12: div2(s(|0|())) -> |0|() r13: div2(s(s(x))) -> s(div2(x)) r14: p(|0|()) -> |0|() r15: p(s(x)) -> x The estimated dependency graph contains the following SCCs: {p1, p3, p6} {p10} {p11} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: cond1#(true(),x) -> cond2#(even(x),x) p2: cond2#(false(),x) -> cond1#(neq(x,|0|()),p(x)) p3: cond2#(true(),x) -> cond1#(neq(x,|0|()),div2(x)) and R consists of: r1: cond1(true(),x) -> cond2(even(x),x) r2: cond2(true(),x) -> cond1(neq(x,|0|()),div2(x)) r3: cond2(false(),x) -> cond1(neq(x,|0|()),p(x)) r4: neq(|0|(),|0|()) -> false() r5: neq(|0|(),s(x)) -> true() r6: neq(s(x),|0|()) -> true() r7: neq(s(x),s(y())) -> neq(x,y()) r8: even(|0|()) -> true() r9: even(s(|0|())) -> false() r10: even(s(s(x))) -> even(x) r11: div2(|0|()) -> |0|() r12: div2(s(|0|())) -> |0|() r13: div2(s(s(x))) -> s(div2(x)) r14: p(|0|()) -> |0|() r15: p(s(x)) -> x The set of usable rules consists of r4, r5, r6, r7, r11, r12, r13, r14, r15 Take the reduction pair: generalized weighted path order (>=MG, >G) base order 1: max/plus interpretation on natural numbers: cond1#_A(x1,x2) = max{x1 + 55, x2 + 30} true_A = 11 cond2#_A(x1,x2) = max{64, x2 + 10} even_A(x1) = max{7, x1 - 132} false_A = 8 neq_A(x1,x2) = max{9, x1 - 45, x2 - 23} |0|_A = 30 p_A(x1) = max{31, x1 - 31} div2_A(x1) = max{34, x1 - 31} s_A(x1) = x1 + 66 y_A = 22 base order 2: marked-algebra reduction triple (>=A, >=A!, >A!): matrix interpretation with standard point-wise order: carrier: N^1 order: standard order interpretations: cond1#_A(x1,x2) = x2 true_A() = 8 cond2#_A(x1,x2) = x2 even_A(x1) = x1 + 1 false_A() = 8 neq_A(x1,x2) = 8 |0|_A() = 1 p_A(x1) = x1 div2_A(x1) = x1 s_A(x1) = x1 + 5 y_A() = 1 cond1#!_A(x1,x2) = 6 true!_A() = 7 cond2#!_A(x1,x2) = x2 + 6 even!_A(x1) = x1 + 5 false!_A() = 2 neq!_A(x1,x2) = x1 + 3 |0|!_A() = 4 p!_A(x1) = 1 div2!_A(x1) = x1 + 5 s!_A(x1) = x1 + 4 y!_A() = 0 partial status: pi(cond1#) = [] pi(true) = [] pi(cond2#) = [2] pi(even) = [] pi(false) = [] pi(neq) = [] pi(|0|) = [] pi(p) = [] pi(div2) = [] pi(s) = [1] pi(y) = [] The following rules are removed: p1, p3 -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: cond2#(false(),x) -> cond1#(neq(x,|0|()),p(x)) and R consists of: r1: cond1(true(),x) -> cond2(even(x),x) r2: cond2(true(),x) -> cond1(neq(x,|0|()),div2(x)) r3: cond2(false(),x) -> cond1(neq(x,|0|()),p(x)) r4: neq(|0|(),|0|()) -> false() r5: neq(|0|(),s(x)) -> true() r6: neq(s(x),|0|()) -> true() r7: neq(s(x),s(y())) -> neq(x,y()) r8: even(|0|()) -> true() r9: even(s(|0|())) -> false() r10: even(s(s(x))) -> even(x) r11: div2(|0|()) -> |0|() r12: div2(s(|0|())) -> |0|() r13: div2(s(s(x))) -> s(div2(x)) r14: p(|0|()) -> |0|() r15: p(s(x)) -> x The estimated dependency graph contains the following SCCs: (no SCCs) -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: even#(s(s(x))) -> even#(x) and R consists of: r1: cond1(true(),x) -> cond2(even(x),x) r2: cond2(true(),x) -> cond1(neq(x,|0|()),div2(x)) r3: cond2(false(),x) -> cond1(neq(x,|0|()),p(x)) r4: neq(|0|(),|0|()) -> false() r5: neq(|0|(),s(x)) -> true() r6: neq(s(x),|0|()) -> true() r7: neq(s(x),s(y())) -> neq(x,y()) r8: even(|0|()) -> true() r9: even(s(|0|())) -> false() r10: even(s(s(x))) -> even(x) r11: div2(|0|()) -> |0|() r12: div2(s(|0|())) -> |0|() r13: div2(s(s(x))) -> s(div2(x)) r14: p(|0|()) -> |0|() r15: p(s(x)) -> x The set of usable rules consists of (no rules) Take the reduction pair: generalized weighted path order (>=MG, >G) base order 1: max/plus interpretation on natural numbers: even#_A(x1) = max{7, x1 + 5} s_A(x1) = x1 + 6 base order 2: marked-algebra reduction triple (>=A, >=A!, >A!): matrix interpretation with standard point-wise order: carrier: N^1 order: standard order interpretations: even#_A(x1) = 0 s_A(x1) = 1 even#!_A(x1) = 4 s!_A(x1) = 3 partial status: pi(even#) = [1] pi(s) = [] 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: div2#(s(s(x))) -> div2#(x) and R consists of: r1: cond1(true(),x) -> cond2(even(x),x) r2: cond2(true(),x) -> cond1(neq(x,|0|()),div2(x)) r3: cond2(false(),x) -> cond1(neq(x,|0|()),p(x)) r4: neq(|0|(),|0|()) -> false() r5: neq(|0|(),s(x)) -> true() r6: neq(s(x),|0|()) -> true() r7: neq(s(x),s(y())) -> neq(x,y()) r8: even(|0|()) -> true() r9: even(s(|0|())) -> false() r10: even(s(s(x))) -> even(x) r11: div2(|0|()) -> |0|() r12: div2(s(|0|())) -> |0|() r13: div2(s(s(x))) -> s(div2(x)) r14: p(|0|()) -> |0|() r15: p(s(x)) -> x The set of usable rules consists of (no rules) Take the reduction pair: generalized weighted path order (>=MG, >G) base order 1: max/plus interpretation on natural numbers: div2#_A(x1) = max{7, x1 + 5} s_A(x1) = x1 + 6 base order 2: marked-algebra reduction triple (>=A, >=A!, >A!): matrix interpretation with standard point-wise order: carrier: N^1 order: standard order interpretations: div2#_A(x1) = 0 s_A(x1) = 1 div2#!_A(x1) = 4 s!_A(x1) = 3 partial status: pi(div2#) = [1] pi(s) = [] The following rules are removed: p1 Then no dependency pair remains.