YES We show the termination of the TRS R: app(rev(),nil()) -> nil() app(rev(),app(app(cons(),x),l)) -> app(app(cons(),app(app(rev1(),x),l)),app(app(rev2(),x),l)) app(app(rev1(),|0|()),nil()) -> |0|() app(app(rev1(),app(s(),x)),nil()) -> app(s(),x) app(app(rev1(),x),app(app(cons(),y),l)) -> app(app(rev1(),y),l) app(app(rev2(),x),nil()) -> nil() app(app(rev2(),x),app(app(cons(),y),l)) -> app(rev(),app(app(cons(),x),app(app(rev2(),y),l))) app(app(map(),f),nil()) -> nil() app(app(map(),f),app(app(cons(),x),xs)) -> app(app(cons(),app(f,x)),app(app(map(),f),xs)) app(app(filter(),f),nil()) -> nil() app(app(filter(),f),app(app(cons(),x),xs)) -> app(app(app(app(filter2(),app(f,x)),f),x),xs) app(app(app(app(filter2(),true()),f),x),xs) -> app(app(cons(),x),app(app(filter(),f),xs)) app(app(app(app(filter2(),false()),f),x),xs) -> app(app(filter(),f),xs) Instead we prove termination of the uncurried system: app(cons_0(),y) -> cons_1(y) app(cons_1(x1),y) -> cons_2(x1,y) app(filter_0(),y) -> filter_1(y) app(filter_1(x1),y) -> filter_2(x1,y) app(filter2_0(),y) -> filter2_1(y) app(filter2_1(x1),y) -> filter2_2(x1,y) app(filter2_2(x1,x2),y) -> filter2_3(x1,x2,y) app(filter2_3(x1,x2,x3),y) -> filter2_4(x1,x2,x3,y) app(map_0(),y) -> map_1(y) app(map_1(x1),y) -> map_2(x1,y) app(rev_0(),y) -> rev_1(y) app(rev1_0(),y) -> rev1_1(y) app(rev1_1(x1),y) -> rev1_2(x1,y) app(rev2_0(),y) -> rev2_1(y) app(rev2_1(x1),y) -> rev2_2(x1,y) app(s_0(),y) -> s_1(y) rev_1(nil_0()) -> nil_0() rev_1(cons_2(x,l)) -> cons_2(rev1_2(x,l),rev2_2(x,l)) rev1_2(|0|_0(),nil_0()) -> |0|_0() rev1_2(s_1(x),nil_0()) -> s_1(x) rev1_2(x,cons_2(y,l)) -> rev1_2(y,l) rev2_2(x,nil_0()) -> nil_0() rev2_2(x,cons_2(y,l)) -> rev_1(cons_2(x,rev2_2(y,l))) map_2(f,nil_0()) -> nil_0() map_2(f,cons_2(x,xs)) -> cons_2(app(f,x),map_2(f,xs)) filter_2(f,nil_0()) -> nil_0() filter_2(f,cons_2(x,xs)) -> filter2_4(app(f,x),f,x,xs) filter2_4(true_0(),f,x,xs) -> cons_2(x,filter_2(f,xs)) filter2_4(false_0(),f,x,xs) -> filter_2(f,xs) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: app#(filter_1(x1),y) -> filter_2#(x1,y) p2: app#(filter2_3(x1,x2,x3),y) -> filter2_4#(x1,x2,x3,y) p3: app#(map_1(x1),y) -> map_2#(x1,y) p4: app#(rev_0(),y) -> rev_1#(y) p5: app#(rev1_1(x1),y) -> rev1_2#(x1,y) p6: app#(rev2_1(x1),y) -> rev2_2#(x1,y) p7: rev_1#(cons_2(x,l)) -> rev1_2#(x,l) p8: rev_1#(cons_2(x,l)) -> rev2_2#(x,l) p9: rev1_2#(x,cons_2(y,l)) -> rev1_2#(y,l) p10: rev2_2#(x,cons_2(y,l)) -> rev_1#(cons_2(x,rev2_2(y,l))) p11: rev2_2#(x,cons_2(y,l)) -> rev2_2#(y,l) p12: map_2#(f,cons_2(x,xs)) -> app#(f,x) p13: map_2#(f,cons_2(x,xs)) -> map_2#(f,xs) p14: filter_2#(f,cons_2(x,xs)) -> filter2_4#(app(f,x),f,x,xs) p15: filter_2#(f,cons_2(x,xs)) -> app#(f,x) p16: filter2_4#(true_0(),f,x,xs) -> filter_2#(f,xs) p17: filter2_4#(false_0(),f,x,xs) -> filter_2#(f,xs) and R consists of: r1: app(cons_0(),y) -> cons_1(y) r2: app(cons_1(x1),y) -> cons_2(x1,y) r3: app(filter_0(),y) -> filter_1(y) r4: app(filter_1(x1),y) -> filter_2(x1,y) r5: app(filter2_0(),y) -> filter2_1(y) r6: app(filter2_1(x1),y) -> filter2_2(x1,y) r7: app(filter2_2(x1,x2),y) -> filter2_3(x1,x2,y) r8: app(filter2_3(x1,x2,x3),y) -> filter2_4(x1,x2,x3,y) r9: app(map_0(),y) -> map_1(y) r10: app(map_1(x1),y) -> map_2(x1,y) r11: app(rev_0(),y) -> rev_1(y) r12: app(rev1_0(),y) -> rev1_1(y) r13: app(rev1_1(x1),y) -> rev1_2(x1,y) r14: app(rev2_0(),y) -> rev2_1(y) r15: app(rev2_1(x1),y) -> rev2_2(x1,y) r16: app(s_0(),y) -> s_1(y) r17: rev_1(nil_0()) -> nil_0() r18: rev_1(cons_2(x,l)) -> cons_2(rev1_2(x,l),rev2_2(x,l)) r19: rev1_2(|0|_0(),nil_0()) -> |0|_0() r20: rev1_2(s_1(x),nil_0()) -> s_1(x) r21: rev1_2(x,cons_2(y,l)) -> rev1_2(y,l) r22: rev2_2(x,nil_0()) -> nil_0() r23: rev2_2(x,cons_2(y,l)) -> rev_1(cons_2(x,rev2_2(y,l))) r24: map_2(f,nil_0()) -> nil_0() r25: map_2(f,cons_2(x,xs)) -> cons_2(app(f,x),map_2(f,xs)) r26: filter_2(f,nil_0()) -> nil_0() r27: filter_2(f,cons_2(x,xs)) -> filter2_4(app(f,x),f,x,xs) r28: filter2_4(true_0(),f,x,xs) -> cons_2(x,filter_2(f,xs)) r29: filter2_4(false_0(),f,x,xs) -> filter_2(f,xs) The estimated dependency graph contains the following SCCs: {p1, p2, p3, p12, p13, p14, p15, p16, p17} {p8, p10, p11} {p9} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: app#(filter_1(x1),y) -> filter_2#(x1,y) p2: filter_2#(f,cons_2(x,xs)) -> app#(f,x) p3: app#(map_1(x1),y) -> map_2#(x1,y) p4: map_2#(f,cons_2(x,xs)) -> map_2#(f,xs) p5: map_2#(f,cons_2(x,xs)) -> app#(f,x) p6: app#(filter2_3(x1,x2,x3),y) -> filter2_4#(x1,x2,x3,y) p7: filter2_4#(false_0(),f,x,xs) -> filter_2#(f,xs) p8: filter_2#(f,cons_2(x,xs)) -> filter2_4#(app(f,x),f,x,xs) p9: filter2_4#(true_0(),f,x,xs) -> filter_2#(f,xs) and R consists of: r1: app(cons_0(),y) -> cons_1(y) r2: app(cons_1(x1),y) -> cons_2(x1,y) r3: app(filter_0(),y) -> filter_1(y) r4: app(filter_1(x1),y) -> filter_2(x1,y) r5: app(filter2_0(),y) -> filter2_1(y) r6: app(filter2_1(x1),y) -> filter2_2(x1,y) r7: app(filter2_2(x1,x2),y) -> filter2_3(x1,x2,y) r8: app(filter2_3(x1,x2,x3),y) -> filter2_4(x1,x2,x3,y) r9: app(map_0(),y) -> map_1(y) r10: app(map_1(x1),y) -> map_2(x1,y) r11: app(rev_0(),y) -> rev_1(y) r12: app(rev1_0(),y) -> rev1_1(y) r13: app(rev1_1(x1),y) -> rev1_2(x1,y) r14: app(rev2_0(),y) -> rev2_1(y) r15: app(rev2_1(x1),y) -> rev2_2(x1,y) r16: app(s_0(),y) -> s_1(y) r17: rev_1(nil_0()) -> nil_0() r18: rev_1(cons_2(x,l)) -> cons_2(rev1_2(x,l),rev2_2(x,l)) r19: rev1_2(|0|_0(),nil_0()) -> |0|_0() r20: rev1_2(s_1(x),nil_0()) -> s_1(x) r21: rev1_2(x,cons_2(y,l)) -> rev1_2(y,l) r22: rev2_2(x,nil_0()) -> nil_0() r23: rev2_2(x,cons_2(y,l)) -> rev_1(cons_2(x,rev2_2(y,l))) r24: map_2(f,nil_0()) -> nil_0() r25: map_2(f,cons_2(x,xs)) -> cons_2(app(f,x),map_2(f,xs)) r26: filter_2(f,nil_0()) -> nil_0() r27: filter_2(f,cons_2(x,xs)) -> filter2_4(app(f,x),f,x,xs) r28: filter2_4(true_0(),f,x,xs) -> cons_2(x,filter_2(f,xs)) r29: filter2_4(false_0(),f,x,xs) -> filter_2(f,xs) The set of usable rules consists of (no rules) Take the reduction pair: generalized weighted path order (>=MG, >G) base order 1: trivial reduction triple (T x T, T x T, Φ) base order 2: lexicographic combination of reduction triples: 1. marked-algebra reduction triple (>=A, >=A!, >A!): max/plus interpretation on natural numbers: app#_A(x1,x2) = 1 filter_1_A(x1) = max{14, x1 + 13} filter_2#_A(x1,x2) = 1 cons_2_A(x1,x2) = max{54, x1 + 40, x2 + 40} map_1_A(x1) = max{14, x1 + 13} map_2#_A(x1,x2) = 1 filter2_3_A(x1,x2,x3) = max{14, x2 + 13, x3 + 13} filter2_4#_A(x1,x2,x3,x4) = 1 false_0_A = 1 app_A(x1,x2) = max{1, x1 - 13} true_0_A = 0 app#!_A(x1,x2) = max{11, x2 + 9} filter_1!_A(x1) = 1 filter_2#!_A(x1,x2) = max{2, x2 - 16} cons_2!_A(x1,x2) = max{7, x1 - 11, x2 - 15} map_1!_A(x1) = max{7, x1 + 1} map_2#!_A(x1,x2) = max{8, x2 - 30} filter2_3!_A(x1,x2,x3) = max{4, x1 - 10, x2 - 1, x3 - 1} filter2_4#!_A(x1,x2,x3,x4) = max{7, x4 - 15} false_0!_A = 1 app!_A(x1,x2) = max{5, x1 - 3} true_0!_A = 3 2. marked-algebra reduction triple (>=A, >=A!, >A!): matrix interpretation with standard point-wise order: carrier: N^1 order: standard order interpretations: app#_A(x1,x2) = 0 filter_1_A(x1) = x1 + 2 filter_2#_A(x1,x2) = 0 cons_2_A(x1,x2) = 4 map_1_A(x1) = 2 map_2#_A(x1,x2) = 0 filter2_3_A(x1,x2,x3) = 2 filter2_4#_A(x1,x2,x3,x4) = 0 false_0_A() = 1 app_A(x1,x2) = 1 true_0_A() = 1 app#!_A(x1,x2) = x1 + 3 filter_1!_A(x1) = 5 filter_2#!_A(x1,x2) = x1 + 4 cons_2!_A(x1,x2) = 6 map_1!_A(x1) = x1 + 8 map_2#!_A(x1,x2) = x1 + 7 filter2_3!_A(x1,x2,x3) = 6 filter2_4#!_A(x1,x2,x3,x4) = 3 false_0!_A() = 0 app!_A(x1,x2) = x2 + 3 true_0!_A() = 0 partial status: pi(app#) = [] pi(filter_1) = [] pi(filter_2#) = [] pi(cons_2) = [] pi(map_1) = [1] pi(map_2#) = [] pi(filter2_3) = [] pi(filter2_4#) = [] pi(false_0) = [] pi(app) = [] pi(true_0) = [] The following rules are removed: p1, p2, p3, p4, p5, p6, p7, p8, p9 Then no dependency pair remains. -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: rev2_2#(x,cons_2(y,l)) -> rev_1#(cons_2(x,rev2_2(y,l))) p2: rev_1#(cons_2(x,l)) -> rev2_2#(x,l) p3: rev2_2#(x,cons_2(y,l)) -> rev2_2#(y,l) and R consists of: r1: app(cons_0(),y) -> cons_1(y) r2: app(cons_1(x1),y) -> cons_2(x1,y) r3: app(filter_0(),y) -> filter_1(y) r4: app(filter_1(x1),y) -> filter_2(x1,y) r5: app(filter2_0(),y) -> filter2_1(y) r6: app(filter2_1(x1),y) -> filter2_2(x1,y) r7: app(filter2_2(x1,x2),y) -> filter2_3(x1,x2,y) r8: app(filter2_3(x1,x2,x3),y) -> filter2_4(x1,x2,x3,y) r9: app(map_0(),y) -> map_1(y) r10: app(map_1(x1),y) -> map_2(x1,y) r11: app(rev_0(),y) -> rev_1(y) r12: app(rev1_0(),y) -> rev1_1(y) r13: app(rev1_1(x1),y) -> rev1_2(x1,y) r14: app(rev2_0(),y) -> rev2_1(y) r15: app(rev2_1(x1),y) -> rev2_2(x1,y) r16: app(s_0(),y) -> s_1(y) r17: rev_1(nil_0()) -> nil_0() r18: rev_1(cons_2(x,l)) -> cons_2(rev1_2(x,l),rev2_2(x,l)) r19: rev1_2(|0|_0(),nil_0()) -> |0|_0() r20: rev1_2(s_1(x),nil_0()) -> s_1(x) r21: rev1_2(x,cons_2(y,l)) -> rev1_2(y,l) r22: rev2_2(x,nil_0()) -> nil_0() r23: rev2_2(x,cons_2(y,l)) -> rev_1(cons_2(x,rev2_2(y,l))) r24: map_2(f,nil_0()) -> nil_0() r25: map_2(f,cons_2(x,xs)) -> cons_2(app(f,x),map_2(f,xs)) r26: filter_2(f,nil_0()) -> nil_0() r27: filter_2(f,cons_2(x,xs)) -> filter2_4(app(f,x),f,x,xs) r28: filter2_4(true_0(),f,x,xs) -> cons_2(x,filter_2(f,xs)) r29: filter2_4(false_0(),f,x,xs) -> filter_2(f,xs) The set of usable rules consists of r17, r18, r19, r20, r21, r22, r23 Take the reduction pair: generalized weighted path order (>=MG, >G) base order 1: trivial reduction triple (T x T, T x T, Φ) base order 2: lexicographic combination of reduction triples: 1. marked-algebra reduction triple (>=A, >=A!, >A!): max/plus interpretation on natural numbers: rev2_2#_A(x1,x2) = max{11, x1 + 1, x2 - 12} cons_2_A(x1,x2) = max{22, x1 + 13, x2} rev_1#_A(x1) = max{11, x1 - 12} rev2_2_A(x1,x2) = max{x1 + 13, x2} rev_1_A(x1) = max{14, x1} nil_0_A = 19 rev1_2_A(x1,x2) = 7 |0|_0_A = 1 s_1_A(x1) = 7 rev2_2#!_A(x1,x2) = 1 cons_2!_A(x1,x2) = max{3, x2 - 14} rev_1#!_A(x1) = 1 rev2_2!_A(x1,x2) = max{x1 + 36, x2 + 14} rev_1!_A(x1) = max{35, x1 + 4} nil_0!_A = 34 rev1_2!_A(x1,x2) = 3 |0|_0!_A = 1 s_1!_A(x1) = 3 2. marked-algebra reduction triple (>=A, >=A!, >A!): matrix interpretation with standard point-wise order: carrier: N^1 order: standard order interpretations: rev2_2#_A(x1,x2) = 0 cons_2_A(x1,x2) = x2 + 3 rev_1#_A(x1) = 0 rev2_2_A(x1,x2) = x2 rev_1_A(x1) = x1 nil_0_A() = 0 rev1_2_A(x1,x2) = 4 |0|_0_A() = 1 s_1_A(x1) = 4 rev2_2#!_A(x1,x2) = x2 + 2 cons_2!_A(x1,x2) = x2 + 3 rev_1#!_A(x1) = x1 + 1 rev2_2!_A(x1,x2) = 6 rev_1!_A(x1) = 4 nil_0!_A() = 1 rev1_2!_A(x1,x2) = 3 |0|_0!_A() = 0 s_1!_A(x1) = 0 partial status: pi(rev2_2#) = [] pi(cons_2) = [] pi(rev_1#) = [] pi(rev2_2) = [] pi(rev_1) = [1] pi(nil_0) = [] pi(rev1_2) = [] pi(|0|_0) = [] pi(s_1) = [] 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_2#(x,cons_2(y,l)) -> rev1_2#(y,l) and R consists of: r1: app(cons_0(),y) -> cons_1(y) r2: app(cons_1(x1),y) -> cons_2(x1,y) r3: app(filter_0(),y) -> filter_1(y) r4: app(filter_1(x1),y) -> filter_2(x1,y) r5: app(filter2_0(),y) -> filter2_1(y) r6: app(filter2_1(x1),y) -> filter2_2(x1,y) r7: app(filter2_2(x1,x2),y) -> filter2_3(x1,x2,y) r8: app(filter2_3(x1,x2,x3),y) -> filter2_4(x1,x2,x3,y) r9: app(map_0(),y) -> map_1(y) r10: app(map_1(x1),y) -> map_2(x1,y) r11: app(rev_0(),y) -> rev_1(y) r12: app(rev1_0(),y) -> rev1_1(y) r13: app(rev1_1(x1),y) -> rev1_2(x1,y) r14: app(rev2_0(),y) -> rev2_1(y) r15: app(rev2_1(x1),y) -> rev2_2(x1,y) r16: app(s_0(),y) -> s_1(y) r17: rev_1(nil_0()) -> nil_0() r18: rev_1(cons_2(x,l)) -> cons_2(rev1_2(x,l),rev2_2(x,l)) r19: rev1_2(|0|_0(),nil_0()) -> |0|_0() r20: rev1_2(s_1(x),nil_0()) -> s_1(x) r21: rev1_2(x,cons_2(y,l)) -> rev1_2(y,l) r22: rev2_2(x,nil_0()) -> nil_0() r23: rev2_2(x,cons_2(y,l)) -> rev_1(cons_2(x,rev2_2(y,l))) r24: map_2(f,nil_0()) -> nil_0() r25: map_2(f,cons_2(x,xs)) -> cons_2(app(f,x),map_2(f,xs)) r26: filter_2(f,nil_0()) -> nil_0() r27: filter_2(f,cons_2(x,xs)) -> filter2_4(app(f,x),f,x,xs) r28: filter2_4(true_0(),f,x,xs) -> cons_2(x,filter_2(f,xs)) r29: filter2_4(false_0(),f,x,xs) -> filter_2(f,xs) The set of usable rules consists of r17 Take the reduction pair: generalized weighted path order (>=MG, >G) base order 1: trivial reduction triple (T x T, T x T, Φ) base order 2: lexicographic combination of reduction triples: 1. marked-algebra reduction triple (>=A, >=A!, >A!): max/plus interpretation on natural numbers: rev1_2#_A(x1,x2) = 0 cons_2_A(x1,x2) = max{3, x1 - 22, x2 - 22} rev_1_A(x1) = max{22, x1 - 7} nil_0_A = 6 rev1_2#!_A(x1,x2) = x1 + 1 cons_2!_A(x1,x2) = max{40, x1 + 36, x2 + 20} rev_1!_A(x1) = max{39, x1 + 31} nil_0!_A = 0 2. marked-algebra reduction triple (>=A, >=A!, >A!): matrix interpretation with standard point-wise order: carrier: N^1 order: standard order interpretations: rev1_2#_A(x1,x2) = x2 cons_2_A(x1,x2) = x1 + x2 + 5 rev_1_A(x1) = x1 + 3 nil_0_A() = 8 rev1_2#!_A(x1,x2) = 0 cons_2!_A(x1,x2) = 13 rev_1!_A(x1) = x1 + 2 nil_0!_A() = 1 partial status: pi(rev1_2#) = [2] pi(cons_2) = [2] pi(rev_1) = [1] pi(nil_0) = [] The following rules are removed: p1 Then no dependency pair remains.