YES We show the termination of the TRS R: 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(flatten(),app(app(node(),x),xs)) -> app(app(cons(),x),app(concat(),app(app(map(),flatten()),xs))) app(concat(),nil()) -> nil() app(concat(),app(app(cons(),x),xs)) -> app(app(append(),x),app(concat(),xs)) app(app(append(),nil()),xs) -> xs app(app(append(),app(app(cons(),x),xs)),ys) -> app(app(cons(),x),app(app(append(),xs),ys)) Instead we prove termination of the uncurried system: app(append_0(),y) -> append_1(y) app(append_1(x1),y) -> append_2(x1,y) app(concat_0(),y) -> concat_1(y) app(cons_0(),y) -> cons_1(y) app(cons_1(x1),y) -> cons_2(x1,y) app(flatten_0(),y) -> flatten_1(y) app(map_0(),y) -> map_1(y) app(map_1(x1),y) -> map_2(x1,y) app(node_0(),y) -> node_1(y) app(node_1(x1),y) -> node_2(x1,y) map_2(f,nil_0()) -> nil_0() map_2(f,cons_2(x,xs)) -> cons_2(app(f,x),map_2(f,xs)) flatten_1(node_2(x,xs)) -> cons_2(x,concat_1(map_2(flatten_0(),xs))) concat_1(nil_0()) -> nil_0() concat_1(cons_2(x,xs)) -> append_2(x,concat_1(xs)) append_2(nil_0(),xs) -> xs append_2(cons_2(x,xs),ys) -> cons_2(x,append_2(xs,ys)) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: app#(append_1(x1),y) -> append_2#(x1,y) p2: app#(concat_0(),y) -> concat_1#(y) p3: app#(flatten_0(),y) -> flatten_1#(y) p4: app#(map_1(x1),y) -> map_2#(x1,y) p5: map_2#(f,cons_2(x,xs)) -> app#(f,x) p6: map_2#(f,cons_2(x,xs)) -> map_2#(f,xs) p7: flatten_1#(node_2(x,xs)) -> concat_1#(map_2(flatten_0(),xs)) p8: flatten_1#(node_2(x,xs)) -> map_2#(flatten_0(),xs) p9: concat_1#(cons_2(x,xs)) -> append_2#(x,concat_1(xs)) p10: concat_1#(cons_2(x,xs)) -> concat_1#(xs) p11: append_2#(cons_2(x,xs),ys) -> append_2#(xs,ys) and R consists of: r1: app(append_0(),y) -> append_1(y) r2: app(append_1(x1),y) -> append_2(x1,y) r3: app(concat_0(),y) -> concat_1(y) r4: app(cons_0(),y) -> cons_1(y) r5: app(cons_1(x1),y) -> cons_2(x1,y) r6: app(flatten_0(),y) -> flatten_1(y) r7: app(map_0(),y) -> map_1(y) r8: app(map_1(x1),y) -> map_2(x1,y) r9: app(node_0(),y) -> node_1(y) r10: app(node_1(x1),y) -> node_2(x1,y) r11: map_2(f,nil_0()) -> nil_0() r12: map_2(f,cons_2(x,xs)) -> cons_2(app(f,x),map_2(f,xs)) r13: flatten_1(node_2(x,xs)) -> cons_2(x,concat_1(map_2(flatten_0(),xs))) r14: concat_1(nil_0()) -> nil_0() r15: concat_1(cons_2(x,xs)) -> append_2(x,concat_1(xs)) r16: append_2(nil_0(),xs) -> xs r17: append_2(cons_2(x,xs),ys) -> cons_2(x,append_2(xs,ys)) The estimated dependency graph contains the following SCCs: {p3, p4, p5, p6, p8} {p10} {p11} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: map_2#(f,cons_2(x,xs)) -> app#(f,x) p2: app#(map_1(x1),y) -> map_2#(x1,y) p3: map_2#(f,cons_2(x,xs)) -> map_2#(f,xs) p4: app#(flatten_0(),y) -> flatten_1#(y) p5: flatten_1#(node_2(x,xs)) -> map_2#(flatten_0(),xs) and R consists of: r1: app(append_0(),y) -> append_1(y) r2: app(append_1(x1),y) -> append_2(x1,y) r3: app(concat_0(),y) -> concat_1(y) r4: app(cons_0(),y) -> cons_1(y) r5: app(cons_1(x1),y) -> cons_2(x1,y) r6: app(flatten_0(),y) -> flatten_1(y) r7: app(map_0(),y) -> map_1(y) r8: app(map_1(x1),y) -> map_2(x1,y) r9: app(node_0(),y) -> node_1(y) r10: app(node_1(x1),y) -> node_2(x1,y) r11: map_2(f,nil_0()) -> nil_0() r12: map_2(f,cons_2(x,xs)) -> cons_2(app(f,x),map_2(f,xs)) r13: flatten_1(node_2(x,xs)) -> cons_2(x,concat_1(map_2(flatten_0(),xs))) r14: concat_1(nil_0()) -> nil_0() r15: concat_1(cons_2(x,xs)) -> append_2(x,concat_1(xs)) r16: append_2(nil_0(),xs) -> xs r17: append_2(cons_2(x,xs),ys) -> cons_2(x,append_2(xs,ys)) The set of usable rules consists of r1, r4, r5, r9 Take the reduction pair: generalized weighted path order (>=MG, >MG) base order 1: max/plus interpretation on natural numbers: map_2#_A(x1,x2) = max{5, x1 - 3} cons_2_A(x1,x2) = max{26, x1 - 73, x2 - 73} app#_A(x1,x2) = max{5, x1 - 3} map_1_A(x1) = x1 + 9 flatten_0_A = 2 flatten_1#_A(x1) = 5 node_2_A(x1,x2) = max{40, x1 + 1, x2 - 10} app_A(x1,x2) = max{63, x1 - 10, x2 - 61} append_0_A = 8 append_1_A(x1) = max{9, x1 - 139} cons_0_A = 8 cons_1_A(x1) = max{9, x1 - 62} node_0_A = 8 node_1_A(x1) = max{9, x1 - 62} base order 2: precedence: node_2 > map_1 > app > map_2# = cons_2 = app# = flatten_1# = node_1 > flatten_0 = append_1 = cons_1 = node_0 > append_0 = cons_0 partial status: pi(map_2#) = [] pi(cons_2) = [] pi(app#) = [] pi(map_1) = [1] pi(flatten_0) = [] pi(flatten_1#) = [] pi(node_2) = [1] pi(app) = [] pi(append_0) = [] pi(append_1) = [] pi(cons_0) = [] pi(cons_1) = [] pi(node_0) = [] pi(node_1) = [] The following rules are removed: p2 -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: map_2#(f,cons_2(x,xs)) -> app#(f,x) p2: map_2#(f,cons_2(x,xs)) -> map_2#(f,xs) p3: app#(flatten_0(),y) -> flatten_1#(y) p4: flatten_1#(node_2(x,xs)) -> map_2#(flatten_0(),xs) and R consists of: r1: app(append_0(),y) -> append_1(y) r2: app(append_1(x1),y) -> append_2(x1,y) r3: app(concat_0(),y) -> concat_1(y) r4: app(cons_0(),y) -> cons_1(y) r5: app(cons_1(x1),y) -> cons_2(x1,y) r6: app(flatten_0(),y) -> flatten_1(y) r7: app(map_0(),y) -> map_1(y) r8: app(map_1(x1),y) -> map_2(x1,y) r9: app(node_0(),y) -> node_1(y) r10: app(node_1(x1),y) -> node_2(x1,y) r11: map_2(f,nil_0()) -> nil_0() r12: map_2(f,cons_2(x,xs)) -> cons_2(app(f,x),map_2(f,xs)) r13: flatten_1(node_2(x,xs)) -> cons_2(x,concat_1(map_2(flatten_0(),xs))) r14: concat_1(nil_0()) -> nil_0() r15: concat_1(cons_2(x,xs)) -> append_2(x,concat_1(xs)) r16: append_2(nil_0(),xs) -> xs r17: append_2(cons_2(x,xs),ys) -> cons_2(x,append_2(xs,ys)) The estimated dependency graph contains the following SCCs: {p1, p2, p3, p4} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: map_2#(f,cons_2(x,xs)) -> app#(f,x) p2: app#(flatten_0(),y) -> flatten_1#(y) p3: flatten_1#(node_2(x,xs)) -> map_2#(flatten_0(),xs) p4: map_2#(f,cons_2(x,xs)) -> map_2#(f,xs) and R consists of: r1: app(append_0(),y) -> append_1(y) r2: app(append_1(x1),y) -> append_2(x1,y) r3: app(concat_0(),y) -> concat_1(y) r4: app(cons_0(),y) -> cons_1(y) r5: app(cons_1(x1),y) -> cons_2(x1,y) r6: app(flatten_0(),y) -> flatten_1(y) r7: app(map_0(),y) -> map_1(y) r8: app(map_1(x1),y) -> map_2(x1,y) r9: app(node_0(),y) -> node_1(y) r10: app(node_1(x1),y) -> node_2(x1,y) r11: map_2(f,nil_0()) -> nil_0() r12: map_2(f,cons_2(x,xs)) -> cons_2(app(f,x),map_2(f,xs)) r13: flatten_1(node_2(x,xs)) -> cons_2(x,concat_1(map_2(flatten_0(),xs))) r14: concat_1(nil_0()) -> nil_0() r15: concat_1(cons_2(x,xs)) -> append_2(x,concat_1(xs)) r16: append_2(nil_0(),xs) -> xs r17: append_2(cons_2(x,xs),ys) -> cons_2(x,append_2(xs,ys)) The set of usable rules consists of r1, r4, r7, r9 Take the reduction pair: generalized weighted path order (>=MG, >MG) base order 1: max/plus interpretation on natural numbers: map_2#_A(x1,x2) = max{3, x1 - 1, x2 - 8} cons_2_A(x1,x2) = max{38, x1 + 16, x2 + 18} app#_A(x1,x2) = max{x1 - 2, x2 + 7} flatten_0_A = 4 flatten_1#_A(x1) = x1 + 6 node_2_A(x1,x2) = max{38, x1 - 1, x2 - 7} app_A(x1,x2) = max{38, x1 - 35, x2 - 54} append_0_A = 34 append_1_A(x1) = max{16, x1 - 87} cons_0_A = 33 cons_1_A(x1) = max{34, x1 - 55} map_0_A = 33 map_1_A(x1) = max{34, x1 - 55} node_0_A = 33 node_1_A(x1) = max{34, x1 - 55} base order 2: precedence: node_2 > flatten_1# = app > app# = map_1 = node_1 > map_2# = cons_2 = flatten_0 = cons_0 = map_0 = node_0 > append_1 = cons_1 > append_0 partial status: pi(map_2#) = [] pi(cons_2) = [2] pi(app#) = [2] pi(flatten_0) = [] pi(flatten_1#) = [1] pi(node_2) = [] pi(app) = [] pi(append_0) = [] pi(append_1) = [] pi(cons_0) = [] pi(cons_1) = [] pi(map_0) = [] pi(map_1) = [] pi(node_0) = [] pi(node_1) = [] The following rules are removed: p1 -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: app#(flatten_0(),y) -> flatten_1#(y) p2: flatten_1#(node_2(x,xs)) -> map_2#(flatten_0(),xs) p3: map_2#(f,cons_2(x,xs)) -> map_2#(f,xs) and R consists of: r1: app(append_0(),y) -> append_1(y) r2: app(append_1(x1),y) -> append_2(x1,y) r3: app(concat_0(),y) -> concat_1(y) r4: app(cons_0(),y) -> cons_1(y) r5: app(cons_1(x1),y) -> cons_2(x1,y) r6: app(flatten_0(),y) -> flatten_1(y) r7: app(map_0(),y) -> map_1(y) r8: app(map_1(x1),y) -> map_2(x1,y) r9: app(node_0(),y) -> node_1(y) r10: app(node_1(x1),y) -> node_2(x1,y) r11: map_2(f,nil_0()) -> nil_0() r12: map_2(f,cons_2(x,xs)) -> cons_2(app(f,x),map_2(f,xs)) r13: flatten_1(node_2(x,xs)) -> cons_2(x,concat_1(map_2(flatten_0(),xs))) r14: concat_1(nil_0()) -> nil_0() r15: concat_1(cons_2(x,xs)) -> append_2(x,concat_1(xs)) r16: append_2(nil_0(),xs) -> xs r17: append_2(cons_2(x,xs),ys) -> cons_2(x,append_2(xs,ys)) The estimated dependency graph contains the following SCCs: {p3} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: map_2#(f,cons_2(x,xs)) -> map_2#(f,xs) and R consists of: r1: app(append_0(),y) -> append_1(y) r2: app(append_1(x1),y) -> append_2(x1,y) r3: app(concat_0(),y) -> concat_1(y) r4: app(cons_0(),y) -> cons_1(y) r5: app(cons_1(x1),y) -> cons_2(x1,y) r6: app(flatten_0(),y) -> flatten_1(y) r7: app(map_0(),y) -> map_1(y) r8: app(map_1(x1),y) -> map_2(x1,y) r9: app(node_0(),y) -> node_1(y) r10: app(node_1(x1),y) -> node_2(x1,y) r11: map_2(f,nil_0()) -> nil_0() r12: map_2(f,cons_2(x,xs)) -> cons_2(app(f,x),map_2(f,xs)) r13: flatten_1(node_2(x,xs)) -> cons_2(x,concat_1(map_2(flatten_0(),xs))) r14: concat_1(nil_0()) -> nil_0() r15: concat_1(cons_2(x,xs)) -> append_2(x,concat_1(xs)) r16: append_2(nil_0(),xs) -> xs r17: append_2(cons_2(x,xs),ys) -> cons_2(x,append_2(xs,ys)) The set of usable rules consists of r1, r4, r7, r9, r10 Take the reduction pair: generalized weighted path order (>=MG, >MG) base order 1: max/plus interpretation on natural numbers: map_2#_A(x1,x2) = max{19, x1 + 1, x2 + 10} cons_2_A(x1,x2) = max{x1 - 8, x2 + 9} app_A(x1,x2) = max{7, x1 - 8, x2 - 7} append_0_A = 1 append_1_A(x1) = max{2, x1 - 12} cons_0_A = 2 cons_1_A(x1) = max{3, x1 - 8} map_0_A = 10 map_1_A(x1) = max{1, x1 - 8} node_0_A = 6 node_1_A(x1) = max{7, x1 - 16} node_2_A(x1,x2) = max{7, x1 - 24, x2 - 24} base order 2: precedence: map_2# > cons_2 = app > cons_0 = node_2 > append_1 = cons_1 = node_1 > append_0 = node_0 > map_1 > map_0 partial status: pi(map_2#) = [2] pi(cons_2) = [2] pi(app) = [] pi(append_0) = [] pi(append_1) = [] pi(cons_0) = [] pi(cons_1) = [] pi(map_0) = [] pi(map_1) = [] pi(node_0) = [] pi(node_1) = [] pi(node_2) = [] 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: concat_1#(cons_2(x,xs)) -> concat_1#(xs) and R consists of: r1: app(append_0(),y) -> append_1(y) r2: app(append_1(x1),y) -> append_2(x1,y) r3: app(concat_0(),y) -> concat_1(y) r4: app(cons_0(),y) -> cons_1(y) r5: app(cons_1(x1),y) -> cons_2(x1,y) r6: app(flatten_0(),y) -> flatten_1(y) r7: app(map_0(),y) -> map_1(y) r8: app(map_1(x1),y) -> map_2(x1,y) r9: app(node_0(),y) -> node_1(y) r10: app(node_1(x1),y) -> node_2(x1,y) r11: map_2(f,nil_0()) -> nil_0() r12: map_2(f,cons_2(x,xs)) -> cons_2(app(f,x),map_2(f,xs)) r13: flatten_1(node_2(x,xs)) -> cons_2(x,concat_1(map_2(flatten_0(),xs))) r14: concat_1(nil_0()) -> nil_0() r15: concat_1(cons_2(x,xs)) -> append_2(x,concat_1(xs)) r16: append_2(nil_0(),xs) -> xs r17: append_2(cons_2(x,xs),ys) -> cons_2(x,append_2(xs,ys)) The set of usable rules consists of r1, r4, r7, r9, r10 Take the reduction pair: generalized weighted path order (>=MG, >MG) base order 1: max/plus interpretation on natural numbers: concat_1#_A(x1) = max{2, x1 - 7} cons_2_A(x1,x2) = max{10, x1 + 6, x2 + 6} app_A(x1,x2) = max{11, x1 - 7, x2 - 7} append_0_A = 6 append_1_A(x1) = max{0, x1 - 8} cons_0_A = 5 cons_1_A(x1) = max{6, x1 - 8} map_0_A = 3 map_1_A(x1) = max{4, x1 - 8} node_0_A = 5 node_1_A(x1) = max{6, x1 - 8} node_2_A(x1,x2) = max{9, x1 - 23, x2 - 23} base order 2: precedence: app > cons_2 = append_1 > concat_1# = append_0 = cons_1 = node_2 > cons_0 = node_1 > map_1 = node_0 > map_0 partial status: pi(concat_1#) = [] pi(cons_2) = [2] pi(app) = [] pi(append_0) = [] pi(append_1) = [] pi(cons_0) = [] pi(cons_1) = [] pi(map_0) = [] pi(map_1) = [] pi(node_0) = [] pi(node_1) = [] pi(node_2) = [] 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: append_2#(cons_2(x,xs),ys) -> append_2#(xs,ys) and R consists of: r1: app(append_0(),y) -> append_1(y) r2: app(append_1(x1),y) -> append_2(x1,y) r3: app(concat_0(),y) -> concat_1(y) r4: app(cons_0(),y) -> cons_1(y) r5: app(cons_1(x1),y) -> cons_2(x1,y) r6: app(flatten_0(),y) -> flatten_1(y) r7: app(map_0(),y) -> map_1(y) r8: app(map_1(x1),y) -> map_2(x1,y) r9: app(node_0(),y) -> node_1(y) r10: app(node_1(x1),y) -> node_2(x1,y) r11: map_2(f,nil_0()) -> nil_0() r12: map_2(f,cons_2(x,xs)) -> cons_2(app(f,x),map_2(f,xs)) r13: flatten_1(node_2(x,xs)) -> cons_2(x,concat_1(map_2(flatten_0(),xs))) r14: concat_1(nil_0()) -> nil_0() r15: concat_1(cons_2(x,xs)) -> append_2(x,concat_1(xs)) r16: append_2(nil_0(),xs) -> xs r17: append_2(cons_2(x,xs),ys) -> cons_2(x,append_2(xs,ys)) The set of usable rules consists of r1, r4, r7, r9, r10 Take the reduction pair: generalized weighted path order (>=MG, >MG) base order 1: max/plus interpretation on natural numbers: append_2#_A(x1,x2) = max{35, x1 + 31, x2 + 1} cons_2_A(x1,x2) = max{4, x1 - 30, x2} app_A(x1,x2) = max{22, x1 - 7, x2 - 1} append_0_A = 1 append_1_A(x1) = max{2, x1 - 2} cons_0_A = 2 cons_1_A(x1) = max{3, x1 - 31} map_0_A = 6 map_1_A(x1) = max{0, x1 - 2} node_0_A = 5 node_1_A(x1) = max{6, x1 - 2} node_2_A(x1,x2) = max{7, x1 - 11, x2 - 11} base order 2: precedence: append_2# > cons_2 = app > append_0 = cons_0 = node_2 > append_1 = cons_1 = node_1 > node_0 > map_1 > map_0 partial status: pi(append_2#) = [1] pi(cons_2) = [2] pi(app) = [] pi(append_0) = [] pi(append_1) = [] pi(cons_0) = [] pi(cons_1) = [] pi(map_0) = [] pi(map_1) = [] pi(node_0) = [] pi(node_1) = [] pi(node_2) = [] The following rules are removed: p1 Then no dependency pair remains.