YES We show the termination of the TRS R: rev(nil()) -> nil() rev(cons(x,l)) -> cons(rev1(x,l),rev2(x,l)) rev1(|0|(),nil()) -> |0|() rev1(s(x),nil()) -> s(x) rev1(x,cons(y,l)) -> rev1(y,l) rev2(x,nil()) -> nil() rev2(x,cons(y,l)) -> rev(cons(x,rev2(y,l))) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: rev#(cons(x,l)) -> rev1#(x,l) p2: rev#(cons(x,l)) -> rev2#(x,l) p3: rev1#(x,cons(y,l)) -> rev1#(y,l) p4: rev2#(x,cons(y,l)) -> rev#(cons(x,rev2(y,l))) p5: rev2#(x,cons(y,l)) -> rev2#(y,l) and R consists of: r1: rev(nil()) -> nil() r2: rev(cons(x,l)) -> cons(rev1(x,l),rev2(x,l)) r3: rev1(|0|(),nil()) -> |0|() r4: rev1(s(x),nil()) -> s(x) r5: rev1(x,cons(y,l)) -> rev1(y,l) r6: rev2(x,nil()) -> nil() r7: rev2(x,cons(y,l)) -> rev(cons(x,rev2(y,l))) The estimated dependency graph contains the following SCCs: {p2, p4, p5} {p3} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: rev2#(x,cons(y,l)) -> rev#(cons(x,rev2(y,l))) p2: rev#(cons(x,l)) -> rev2#(x,l) p3: rev2#(x,cons(y,l)) -> rev2#(y,l) and R consists of: r1: rev(nil()) -> nil() r2: rev(cons(x,l)) -> cons(rev1(x,l),rev2(x,l)) r3: rev1(|0|(),nil()) -> |0|() r4: rev1(s(x),nil()) -> s(x) r5: rev1(x,cons(y,l)) -> rev1(y,l) r6: rev2(x,nil()) -> nil() r7: rev2(x,cons(y,l)) -> rev(cons(x,rev2(y,l))) The set of usable rules consists of r1, r2, r3, r4, r5, r6, r7 Take the reduction pair: generalized weighted path order (>=MG, >G) base order 1: max/plus interpretation on natural numbers: rev2#_A(x1,x2) = max{14, x2 + 7} cons_A(x1,x2) = max{13, x2 + 8} rev#_A(x1) = max{14, x1 + 5} rev2_A(x1,x2) = max{5, x2} rev_A(x1) = max{11, x1} nil_A = 10 rev1_A(x1,x2) = 12 |0|_A = 9 s_A(x1) = 9 base order 2: marked-algebra reduction triple (>=A, >=A!, >A!): max/plus interpretation on natural numbers: rev2#_A(x1,x2) = max{0, x1 - 15, x2 - 10} cons_A(x1,x2) = max{9, x1 - 5, x2} rev#_A(x1) = max{0, x1 - 10} rev2_A(x1,x2) = max{9, x1 - 15, x2 - 11} rev_A(x1) = max{9, x1 - 10} nil_A = 9 rev1_A(x1,x2) = max{3, x2 - 5} |0|_A = 4 s_A(x1) = 4 rev2#!_A(x1,x2) = max{15, x1 + 3, x2 + 6} cons!_A(x1,x2) = x1 + 3 rev#!_A(x1) = 16 rev2!_A(x1,x2) = max{16, x1 + 5, x2 + 10} rev!_A(x1) = x1 + 10 nil!_A = 3 rev1!_A(x1,x2) = max{11, x2 - 9} |0|!_A = 1 s!_A(x1) = max{1, x1 - 1} partial status: pi(rev2#) = [] pi(cons) = [] pi(rev#) = [] pi(rev2) = [] pi(rev) = [] pi(nil) = [] pi(rev1) = [] pi(|0|) = [] pi(s) = [] The following rules are removed: p1, p2, p3 Then no dependency pair remains. -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: rev1#(x,cons(y,l)) -> rev1#(y,l) and R consists of: r1: rev(nil()) -> nil() r2: rev(cons(x,l)) -> cons(rev1(x,l),rev2(x,l)) r3: rev1(|0|(),nil()) -> |0|() r4: rev1(s(x),nil()) -> s(x) r5: rev1(x,cons(y,l)) -> rev1(y,l) r6: rev2(x,nil()) -> nil() r7: rev2(x,cons(y,l)) -> rev(cons(x,rev2(y,l))) 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: rev1#_A(x1,x2) = max{x1 - 4, x2 + 6} cons_A(x1,x2) = max{x1 - 4, x2 + 7} base order 2: marked-algebra reduction triple (>=A, >=A!, >A!): max/plus interpretation on natural numbers: rev1#_A(x1,x2) = 0 cons_A(x1,x2) = max{5, x1 - 10, x2 - 4} rev1#!_A(x1,x2) = max{1, x1 - 13, x2 - 9} cons!_A(x1,x2) = max{3, x1 - 12, x2 - 8} partial status: pi(rev1#) = [2] pi(cons) = [] The following rules are removed: p1 Then no dependency pair remains.