YES We show the termination of the TRS R: app(app(app(consif(),true()),x),ys) -> app(app(cons(),x),ys) app(app(app(consif(),false()),x),ys) -> ys app(app(filter(),f),nil()) -> nil() app(app(filter(),f),app(app(cons(),x),xs)) -> app(app(app(consif(),app(f,x)),x),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(consif_0(),y) -> consif_1(y) app(consif_1(x1),y) -> consif_2(x1,y) app(consif_2(x1,x2),y) -> consif_3(x1,x2,y) app(filter_0(),y) -> filter_1(y) app(filter_1(x1),y) -> filter_2(x1,y) consif_3(true_0(),x,ys) -> cons_2(x,ys) consif_3(false_0(),x,ys) -> ys filter_2(f,nil_0()) -> nil_0() filter_2(f,cons_2(x,xs)) -> consif_3(app(f,x),x,filter_2(f,xs)) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: app#(consif_2(x1,x2),y) -> consif_3#(x1,x2,y) p2: app#(filter_1(x1),y) -> filter_2#(x1,y) p3: filter_2#(f,cons_2(x,xs)) -> consif_3#(app(f,x),x,filter_2(f,xs)) p4: filter_2#(f,cons_2(x,xs)) -> app#(f,x) p5: filter_2#(f,cons_2(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(consif_0(),y) -> consif_1(y) r4: app(consif_1(x1),y) -> consif_2(x1,y) r5: app(consif_2(x1,x2),y) -> consif_3(x1,x2,y) r6: app(filter_0(),y) -> filter_1(y) r7: app(filter_1(x1),y) -> filter_2(x1,y) r8: consif_3(true_0(),x,ys) -> cons_2(x,ys) r9: consif_3(false_0(),x,ys) -> ys r10: filter_2(f,nil_0()) -> nil_0() r11: filter_2(f,cons_2(x,xs)) -> consif_3(app(f,x),x,filter_2(f,xs)) The estimated dependency graph contains the following SCCs: {p2, p4, p5} -- 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)) -> filter_2#(f,xs) p3: filter_2#(f,cons_2(x,xs)) -> app#(f,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(consif_0(),y) -> consif_1(y) r4: app(consif_1(x1),y) -> consif_2(x1,y) r5: app(consif_2(x1,x2),y) -> consif_3(x1,x2,y) r6: app(filter_0(),y) -> filter_1(y) r7: app(filter_1(x1),y) -> filter_2(x1,y) r8: consif_3(true_0(),x,ys) -> cons_2(x,ys) r9: consif_3(false_0(),x,ys) -> ys r10: filter_2(f,nil_0()) -> nil_0() r11: filter_2(f,cons_2(x,xs)) -> consif_3(app(f,x),x,filter_2(f,xs)) The set of usable rules consists of r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11 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: model-based reduction triple (=A, >=A!, >A!): finite algebra: carrier: {0,1} interpretations: app#_A(0,0) = 0 app#_A(0,1) = 0 app#_A(1,0) = 0 app#_A(1,1) = 0 filter_1_A(0) = 0 filter_1_A(1) = 1 filter_2#_A(0,0) = 0 filter_2#_A(0,1) = 0 filter_2#_A(1,0) = 0 filter_2#_A(1,1) = 0 cons_2_A(0,0) = 0 cons_2_A(0,1) = 1 cons_2_A(1,0) = 0 cons_2_A(1,1) = 1 app_A(0,0) = 0 app_A(0,1) = 1 app_A(1,0) = 0 app_A(1,1) = 1 cons_0_A = 1 cons_1_A(0) = 0 cons_1_A(1) = 1 consif_0_A = 0 consif_1_A(0) = 0 consif_1_A(1) = 1 consif_2_A(0,0) = 0 consif_2_A(0,1) = 1 consif_2_A(1,0) = 0 consif_2_A(1,1) = 1 consif_3_A(0,0,0) = 0 consif_3_A(0,0,1) = 1 consif_3_A(0,1,0) = 0 consif_3_A(0,1,1) = 1 consif_3_A(1,0,0) = 0 consif_3_A(1,0,1) = 1 consif_3_A(1,1,0) = 0 consif_3_A(1,1,1) = 1 filter_0_A = 0 filter_2_A(0,0) = 0 filter_2_A(0,1) = 1 filter_2_A(1,0) = 0 filter_2_A(1,1) = 1 true_0_A = 0 false_0_A = 0 nil_0_A = 0 app#!_A(0,0) = 0 app#!_A(0,1) = 0 app#!_A(1,0) = 0 app#!_A(1,1) = 0 filter_1!_A(0) = 0 filter_1!_A(1) = 0 filter_2#!_A(0,0) = 0 filter_2#!_A(0,1) = 0 filter_2#!_A(1,0) = 0 filter_2#!_A(1,1) = 0 cons_2!_A(0,0) = 0 cons_2!_A(0,1) = 0 cons_2!_A(1,0) = 0 cons_2!_A(1,1) = 0 app!_A(0,0) = 1 app!_A(0,1) = 1 app!_A(1,0) = 1 app!_A(1,1) = 1 cons_0!_A = 1 cons_1!_A(0) = 0 cons_1!_A(1) = 0 consif_0!_A = 0 consif_1!_A(0) = 0 consif_1!_A(1) = 0 consif_2!_A(0,0) = 0 consif_2!_A(0,1) = 1 consif_2!_A(1,0) = 0 consif_2!_A(1,1) = 0 consif_3!_A(0,0,0) = 0 consif_3!_A(0,0,1) = 0 consif_3!_A(0,1,0) = 0 consif_3!_A(0,1,1) = 1 consif_3!_A(1,0,0) = 0 consif_3!_A(1,0,1) = 0 consif_3!_A(1,1,0) = 0 consif_3!_A(1,1,1) = 0 filter_0!_A = 0 filter_2!_A(0,0) = 1 filter_2!_A(0,1) = 1 filter_2!_A(1,0) = 1 filter_2!_A(1,1) = 1 true_0!_A = 0 false_0!_A = 1 nil_0!_A = 1 partial status: pi(app#) = [2] pi(filter_1) = [1] pi(filter_2#) = [2] pi(cons_2) = [1, 2] pi(app) = [1, 2] pi(cons_0) = [] pi(cons_1) = [1] pi(consif_0) = [] pi(consif_1) = [1] pi(consif_2) = [1, 2] pi(consif_3) = [2, 3] pi(filter_0) = [] pi(filter_2) = [1, 2] pi(true_0) = [] pi(false_0) = [] pi(nil_0) = [] The following rules are removed: p3 -- SCC decomposition. 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)) -> 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(consif_0(),y) -> consif_1(y) r4: app(consif_1(x1),y) -> consif_2(x1,y) r5: app(consif_2(x1,x2),y) -> consif_3(x1,x2,y) r6: app(filter_0(),y) -> filter_1(y) r7: app(filter_1(x1),y) -> filter_2(x1,y) r8: consif_3(true_0(),x,ys) -> cons_2(x,ys) r9: consif_3(false_0(),x,ys) -> ys r10: filter_2(f,nil_0()) -> nil_0() r11: filter_2(f,cons_2(x,xs)) -> consif_3(app(f,x),x,filter_2(f,xs)) The estimated dependency graph contains the following SCCs: {p2} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: filter_2#(f,cons_2(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(consif_0(),y) -> consif_1(y) r4: app(consif_1(x1),y) -> consif_2(x1,y) r5: app(consif_2(x1,x2),y) -> consif_3(x1,x2,y) r6: app(filter_0(),y) -> filter_1(y) r7: app(filter_1(x1),y) -> filter_2(x1,y) r8: consif_3(true_0(),x,ys) -> cons_2(x,ys) r9: consif_3(false_0(),x,ys) -> ys r10: filter_2(f,nil_0()) -> nil_0() r11: filter_2(f,cons_2(x,xs)) -> consif_3(app(f,x),x,filter_2(f,xs)) The set of usable rules consists of r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11 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: model-based reduction triple (=A, >=A!, >A!): finite algebra: carrier: {0,1} interpretations: filter_2#_A(0,0) = 1 filter_2#_A(0,1) = 0 filter_2#_A(1,0) = 0 filter_2#_A(1,1) = 0 cons_2_A(0,0) = 0 cons_2_A(0,1) = 1 cons_2_A(1,0) = 0 cons_2_A(1,1) = 1 app_A(0,0) = 1 app_A(0,1) = 1 app_A(1,0) = 0 app_A(1,1) = 1 cons_0_A = 0 cons_1_A(0) = 1 cons_1_A(1) = 1 consif_0_A = 1 consif_1_A(0) = 0 consif_1_A(1) = 1 consif_2_A(0,0) = 1 consif_2_A(0,1) = 1 consif_2_A(1,0) = 0 consif_2_A(1,1) = 1 consif_3_A(0,0,0) = 0 consif_3_A(0,0,1) = 1 consif_3_A(0,1,0) = 0 consif_3_A(0,1,1) = 1 consif_3_A(1,0,0) = 1 consif_3_A(1,0,1) = 1 consif_3_A(1,1,0) = 0 consif_3_A(1,1,1) = 1 filter_0_A = 1 filter_1_A(0) = 0 filter_1_A(1) = 1 filter_2_A(0,0) = 1 filter_2_A(0,1) = 1 filter_2_A(1,0) = 0 filter_2_A(1,1) = 1 true_0_A = 0 false_0_A = 0 nil_0_A = 1 filter_2#!_A(0,0) = 1 filter_2#!_A(0,1) = 0 filter_2#!_A(1,0) = 1 filter_2#!_A(1,1) = 0 cons_2!_A(0,0) = 1 cons_2!_A(0,1) = 1 cons_2!_A(1,0) = 1 cons_2!_A(1,1) = 1 app!_A(0,0) = 1 app!_A(0,1) = 0 app!_A(1,0) = 1 app!_A(1,1) = 1 cons_0!_A = 1 cons_1!_A(0) = 0 cons_1!_A(1) = 0 consif_0!_A = 0 consif_1!_A(0) = 1 consif_1!_A(1) = 1 consif_2!_A(0,0) = 0 consif_2!_A(0,1) = 0 consif_2!_A(1,0) = 0 consif_2!_A(1,1) = 0 consif_3!_A(0,0,0) = 1 consif_3!_A(0,0,1) = 1 consif_3!_A(0,1,0) = 1 consif_3!_A(0,1,1) = 1 consif_3!_A(1,0,0) = 1 consif_3!_A(1,0,1) = 0 consif_3!_A(1,1,0) = 1 consif_3!_A(1,1,1) = 0 filter_0!_A = 1 filter_1!_A(0) = 1 filter_1!_A(1) = 1 filter_2!_A(0,0) = 1 filter_2!_A(0,1) = 0 filter_2!_A(1,0) = 1 filter_2!_A(1,1) = 1 true_0!_A = 1 false_0!_A = 1 nil_0!_A = 0 partial status: pi(filter_2#) = [2] pi(cons_2) = [2] pi(app) = [2] pi(cons_0) = [] pi(cons_1) = [] pi(consif_0) = [] pi(consif_1) = [1] pi(consif_2) = [] pi(consif_3) = [3] pi(filter_0) = [] pi(filter_1) = [] pi(filter_2) = [2] pi(true_0) = [] pi(false_0) = [] pi(nil_0) = [] The following rules are removed: p1 Then no dependency pair remains.