YES We show the termination of the TRS R: app(app(plus(),|0|()),y) -> y app(app(plus(),app(s(),x)),y) -> app(s(),app(app(plus(),x),y)) app(inc(),xs) -> app(app(map(),app(plus(),app(s(),|0|()))),xs) 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)) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: app#(app(plus(),app(s(),x)),y) -> app#(s(),app(app(plus(),x),y)) p2: app#(app(plus(),app(s(),x)),y) -> app#(app(plus(),x),y) p3: app#(app(plus(),app(s(),x)),y) -> app#(plus(),x) p4: app#(inc(),xs) -> app#(app(map(),app(plus(),app(s(),|0|()))),xs) p5: app#(inc(),xs) -> app#(map(),app(plus(),app(s(),|0|()))) p6: app#(inc(),xs) -> app#(plus(),app(s(),|0|())) p7: app#(inc(),xs) -> app#(s(),|0|()) p8: app#(app(map(),f),app(app(cons(),x),xs)) -> app#(app(cons(),app(f,x)),app(app(map(),f),xs)) p9: app#(app(map(),f),app(app(cons(),x),xs)) -> app#(cons(),app(f,x)) p10: app#(app(map(),f),app(app(cons(),x),xs)) -> app#(f,x) p11: app#(app(map(),f),app(app(cons(),x),xs)) -> app#(app(map(),f),xs) and R consists of: r1: app(app(plus(),|0|()),y) -> y r2: app(app(plus(),app(s(),x)),y) -> app(s(),app(app(plus(),x),y)) r3: app(inc(),xs) -> app(app(map(),app(plus(),app(s(),|0|()))),xs) r4: app(app(map(),f),nil()) -> nil() r5: app(app(map(),f),app(app(cons(),x),xs)) -> app(app(cons(),app(f,x)),app(app(map(),f),xs)) The estimated dependency graph contains the following SCCs: {p4, p10, p11} {p2} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: app#(app(map(),f),app(app(cons(),x),xs)) -> app#(f,x) p2: app#(app(map(),f),app(app(cons(),x),xs)) -> app#(app(map(),f),xs) p3: app#(inc(),xs) -> app#(app(map(),app(plus(),app(s(),|0|()))),xs) and R consists of: r1: app(app(plus(),|0|()),y) -> y r2: app(app(plus(),app(s(),x)),y) -> app(s(),app(app(plus(),x),y)) r3: app(inc(),xs) -> app(app(map(),app(plus(),app(s(),|0|()))),xs) r4: app(app(map(),f),nil()) -> nil() r5: app(app(map(),f),app(app(cons(),x),xs)) -> app(app(cons(),app(f,x)),app(app(map(),f),xs)) The set of usable rules consists of (no rules) Take the reduction pair: lexicographic combination of reduction pairs: 1. max/plus interpretations on natural numbers: app#_A(x1,x2) = x2 + 12 app_A(x1,x2) = max{x1, x2 + 4} map_A = 2 cons_A = 0 inc_A = 1 plus_A = 0 s_A = 0 |0|_A = 0 2. max/plus interpretations on natural numbers: app#_A(x1,x2) = 0 app_A(x1,x2) = 0 map_A = 0 cons_A = 0 inc_A = 0 plus_A = 0 s_A = 0 |0|_A = 0 The next rules are strictly ordered: p1, p2 We remove them from the problem. -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: app#(inc(),xs) -> app#(app(map(),app(plus(),app(s(),|0|()))),xs) and R consists of: r1: app(app(plus(),|0|()),y) -> y r2: app(app(plus(),app(s(),x)),y) -> app(s(),app(app(plus(),x),y)) r3: app(inc(),xs) -> app(app(map(),app(plus(),app(s(),|0|()))),xs) r4: app(app(map(),f),nil()) -> nil() r5: app(app(map(),f),app(app(cons(),x),xs)) -> app(app(cons(),app(f,x)),app(app(map(),f),xs)) The estimated dependency graph contains the following SCCs: (no SCCs) -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: app#(app(plus(),app(s(),x)),y) -> app#(app(plus(),x),y) and R consists of: r1: app(app(plus(),|0|()),y) -> y r2: app(app(plus(),app(s(),x)),y) -> app(s(),app(app(plus(),x),y)) r3: app(inc(),xs) -> app(app(map(),app(plus(),app(s(),|0|()))),xs) r4: app(app(map(),f),nil()) -> nil() r5: app(app(map(),f),app(app(cons(),x),xs)) -> app(app(cons(),app(f,x)),app(app(map(),f),xs)) The set of usable rules consists of (no rules) Take the reduction pair: lexicographic combination of reduction pairs: 1. max/plus interpretations on natural numbers: app#_A(x1,x2) = max{0, x1 - 2} app_A(x1,x2) = max{x1, x2 + 2} plus_A = 0 s_A = 1 2. max/plus interpretations on natural numbers: app#_A(x1,x2) = 0 app_A(x1,x2) = 0 plus_A = 0 s_A = 0 The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.