YES We show the termination of the TRS R: app(f(),app(g(),x)) -> app(g(),app(g(),app(f(),x))) app(f(),app(g(),x)) -> app(g(),app(g(),app(g(),x))) app(app(map(),|fun|),nil()) -> nil() app(app(map(),|fun|),app(app(cons(),x),xs)) -> app(app(cons(),app(|fun|,x)),app(app(map(),|fun|),xs)) app(app(filter(),|fun|),nil()) -> nil() app(app(filter(),|fun|),app(app(cons(),x),xs)) -> app(app(app(app(filter2(),app(|fun|,x)),|fun|),x),xs) app(app(app(app(filter2(),true()),|fun|),x),xs) -> app(app(cons(),x),app(app(filter(),|fun|),xs)) app(app(app(app(filter2(),false()),|fun|),x),xs) -> app(app(filter(),|fun|),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(f_0(),y) -> f_1(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(g_0(),y) -> g_1(y) app(map_0(),y) -> map_1(y) app(map_1(x1),y) -> map_2(x1,y) f_1(g_1(x)) -> g_1(g_1(f_1(x))) f_1(g_1(x)) -> g_1(g_1(g_1(x))) map_2(|fun|,nil_0()) -> nil_0() map_2(|fun|,cons_2(x,xs)) -> cons_2(app(|fun|,x),map_2(|fun|,xs)) filter_2(|fun|,nil_0()) -> nil_0() filter_2(|fun|,cons_2(x,xs)) -> filter2_4(app(|fun|,x),|fun|,x,xs) filter2_4(true_0(),|fun|,x,xs) -> cons_2(x,filter_2(|fun|,xs)) filter2_4(false_0(),|fun|,x,xs) -> filter_2(|fun|,xs) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: app#(f_0(),y) -> f_1#(y) p2: app#(filter_1(x1),y) -> filter_2#(x1,y) p3: app#(filter2_3(x1,x2,x3),y) -> filter2_4#(x1,x2,x3,y) p4: app#(map_1(x1),y) -> map_2#(x1,y) p5: f_1#(g_1(x)) -> f_1#(x) p6: map_2#(|fun|,cons_2(x,xs)) -> app#(|fun|,x) p7: map_2#(|fun|,cons_2(x,xs)) -> map_2#(|fun|,xs) p8: filter_2#(|fun|,cons_2(x,xs)) -> filter2_4#(app(|fun|,x),|fun|,x,xs) p9: filter_2#(|fun|,cons_2(x,xs)) -> app#(|fun|,x) p10: filter2_4#(true_0(),|fun|,x,xs) -> filter_2#(|fun|,xs) p11: filter2_4#(false_0(),|fun|,x,xs) -> filter_2#(|fun|,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(f_0(),y) -> f_1(y) r4: app(filter_0(),y) -> filter_1(y) r5: app(filter_1(x1),y) -> filter_2(x1,y) r6: app(filter2_0(),y) -> filter2_1(y) r7: app(filter2_1(x1),y) -> filter2_2(x1,y) r8: app(filter2_2(x1,x2),y) -> filter2_3(x1,x2,y) r9: app(filter2_3(x1,x2,x3),y) -> filter2_4(x1,x2,x3,y) r10: app(g_0(),y) -> g_1(y) r11: app(map_0(),y) -> map_1(y) r12: app(map_1(x1),y) -> map_2(x1,y) r13: f_1(g_1(x)) -> g_1(g_1(f_1(x))) r14: f_1(g_1(x)) -> g_1(g_1(g_1(x))) r15: map_2(|fun|,nil_0()) -> nil_0() r16: map_2(|fun|,cons_2(x,xs)) -> cons_2(app(|fun|,x),map_2(|fun|,xs)) r17: filter_2(|fun|,nil_0()) -> nil_0() r18: filter_2(|fun|,cons_2(x,xs)) -> filter2_4(app(|fun|,x),|fun|,x,xs) r19: filter2_4(true_0(),|fun|,x,xs) -> cons_2(x,filter_2(|fun|,xs)) r20: filter2_4(false_0(),|fun|,x,xs) -> filter_2(|fun|,xs) The estimated dependency graph contains the following SCCs: {p2, p3, p4, p6, p7, p8, p9, p10, p11} {p5} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: map_2#(|fun|,cons_2(x,xs)) -> app#(|fun|,x) p2: app#(map_1(x1),y) -> map_2#(x1,y) p3: map_2#(|fun|,cons_2(x,xs)) -> map_2#(|fun|,xs) p4: app#(filter2_3(x1,x2,x3),y) -> filter2_4#(x1,x2,x3,y) p5: filter2_4#(false_0(),|fun|,x,xs) -> filter_2#(|fun|,xs) p6: filter_2#(|fun|,cons_2(x,xs)) -> app#(|fun|,x) p7: app#(filter_1(x1),y) -> filter_2#(x1,y) p8: filter_2#(|fun|,cons_2(x,xs)) -> filter2_4#(app(|fun|,x),|fun|,x,xs) p9: filter2_4#(true_0(),|fun|,x,xs) -> filter_2#(|fun|,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(f_0(),y) -> f_1(y) r4: app(filter_0(),y) -> filter_1(y) r5: app(filter_1(x1),y) -> filter_2(x1,y) r6: app(filter2_0(),y) -> filter2_1(y) r7: app(filter2_1(x1),y) -> filter2_2(x1,y) r8: app(filter2_2(x1,x2),y) -> filter2_3(x1,x2,y) r9: app(filter2_3(x1,x2,x3),y) -> filter2_4(x1,x2,x3,y) r10: app(g_0(),y) -> g_1(y) r11: app(map_0(),y) -> map_1(y) r12: app(map_1(x1),y) -> map_2(x1,y) r13: f_1(g_1(x)) -> g_1(g_1(f_1(x))) r14: f_1(g_1(x)) -> g_1(g_1(g_1(x))) r15: map_2(|fun|,nil_0()) -> nil_0() r16: map_2(|fun|,cons_2(x,xs)) -> cons_2(app(|fun|,x),map_2(|fun|,xs)) r17: filter_2(|fun|,nil_0()) -> nil_0() r18: filter_2(|fun|,cons_2(x,xs)) -> filter2_4(app(|fun|,x),|fun|,x,xs) r19: filter2_4(true_0(),|fun|,x,xs) -> cons_2(x,filter_2(|fun|,xs)) r20: filter2_4(false_0(),|fun|,x,xs) -> filter_2(|fun|,xs) The set of usable rules consists of r17 Take the reduction pair: generalized weighted path order (>=MG, >G) base order 1: matrix interpretation with standard point-wise order: carrier: N^1 order: standard order interpretations: map_2#_A(x1,x2) = x1 + x2 + 10 cons_2_A(x1,x2) = x1 + x2 + 9 app#_A(x1,x2) = x1 + x2 + 8 map_1_A(x1) = x1 + 3 filter2_3_A(x1,x2,x3) = x1 + x2 + x3 + 16 filter2_4#_A(x1,x2,x3,x4) = x2 + x4 + 17 false_0_A() = 1 filter_2#_A(x1,x2) = x1 + x2 + 9 filter_1_A(x1) = x1 + 2 app_A(x1,x2) = x1 + x2 + 13 true_0_A() = 1 filter_2_A(x1,x2) = x1 + x2 + 3 nil_0_A() = 1 base order 2: marked-algebra reduction triple (>=A, >=A!, >A!): matrix interpretation with standard point-wise order: carrier: N^1 order: standard order interpretations: map_2#_A(x1,x2) = x1 + x2 cons_2_A(x1,x2) = x1 + x2 + 5 app#_A(x1,x2) = x1 + x2 map_1_A(x1) = x1 + 3 filter2_3_A(x1,x2,x3) = x1 + x2 + x3 + 7 filter2_4#_A(x1,x2,x3,x4) = x2 + x4 + 3 false_0_A() = 1 filter_2#_A(x1,x2) = x1 + x2 + 3 filter_1_A(x1) = x1 + 3 app_A(x1,x2) = x1 + x2 + 1 true_0_A() = 1 filter_2_A(x1,x2) = x1 + x2 + 10 nil_0_A() = 8 map_2#!_A(x1,x2) = x1 + 3 cons_2!_A(x1,x2) = x1 + x2 + 7 app#!_A(x1,x2) = x1 + 3 map_1!_A(x1) = 8 filter2_3!_A(x1,x2,x3) = 1 filter2_4#!_A(x1,x2,x3,x4) = 8 false_0!_A() = 1 filter_2#!_A(x1,x2) = x2 + 7 filter_1!_A(x1) = 1 app!_A(x1,x2) = 8 true_0!_A() = 0 filter_2!_A(x1,x2) = x2 + 2 nil_0!_A() = 0 partial status: pi(map_2#) = [1] pi(cons_2) = [] pi(app#) = [1] pi(map_1) = [] pi(filter2_3) = [3] pi(filter2_4#) = [] pi(false_0) = [] pi(filter_2#) = [] pi(filter_1) = [1] pi(app) = [2] pi(true_0) = [] pi(filter_2) = [] pi(nil_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: f_1#(g_1(x)) -> f_1#(x) and R consists of: r1: app(cons_0(),y) -> cons_1(y) r2: app(cons_1(x1),y) -> cons_2(x1,y) r3: app(f_0(),y) -> f_1(y) r4: app(filter_0(),y) -> filter_1(y) r5: app(filter_1(x1),y) -> filter_2(x1,y) r6: app(filter2_0(),y) -> filter2_1(y) r7: app(filter2_1(x1),y) -> filter2_2(x1,y) r8: app(filter2_2(x1,x2),y) -> filter2_3(x1,x2,y) r9: app(filter2_3(x1,x2,x3),y) -> filter2_4(x1,x2,x3,y) r10: app(g_0(),y) -> g_1(y) r11: app(map_0(),y) -> map_1(y) r12: app(map_1(x1),y) -> map_2(x1,y) r13: f_1(g_1(x)) -> g_1(g_1(f_1(x))) r14: f_1(g_1(x)) -> g_1(g_1(g_1(x))) r15: map_2(|fun|,nil_0()) -> nil_0() r16: map_2(|fun|,cons_2(x,xs)) -> cons_2(app(|fun|,x),map_2(|fun|,xs)) r17: filter_2(|fun|,nil_0()) -> nil_0() r18: filter_2(|fun|,cons_2(x,xs)) -> filter2_4(app(|fun|,x),|fun|,x,xs) r19: filter2_4(true_0(),|fun|,x,xs) -> cons_2(x,filter_2(|fun|,xs)) r20: filter2_4(false_0(),|fun|,x,xs) -> filter_2(|fun|,xs) The set of usable rules consists of r17 Take the reduction pair: generalized weighted path order (>=MG, >G) base order 1: matrix interpretation with standard point-wise order: carrier: N^1 order: standard order interpretations: f_1#_A(x1) = x1 g_1_A(x1) = x1 + 2 filter_2_A(x1,x2) = x1 + x2 + 3 nil_0_A() = 1 base order 2: marked-algebra reduction triple (>=A, >=A!, >A!): matrix interpretation with standard point-wise order: carrier: N^1 order: standard order interpretations: f_1#_A(x1) = x1 g_1_A(x1) = x1 + 4 filter_2_A(x1,x2) = x2 + 20 nil_0_A() = 16 f_1#!_A(x1) = x1 + 3 g_1!_A(x1) = 2 filter_2!_A(x1,x2) = x2 + 6 nil_0!_A() = 21 partial status: pi(f_1#) = [] pi(g_1) = [] pi(filter_2) = [2] pi(nil_0) = [] The following rules are removed: p1 Then no dependency pair remains.