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(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)) inc() -> app(map(),app(plus(),app(s(),|0|()))) -- 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#(app(map(),f),app(app(cons(),x),xs)) -> app#(app(cons(),app(f,x)),app(app(map(),f),xs)) p5: app#(app(map(),f),app(app(cons(),x),xs)) -> app#(cons(),app(f,x)) p6: app#(app(map(),f),app(app(cons(),x),xs)) -> app#(f,x) p7: app#(app(map(),f),app(app(cons(),x),xs)) -> app#(app(map(),f),xs) p8: inc#() -> app#(map(),app(plus(),app(s(),|0|()))) p9: inc#() -> app#(plus(),app(s(),|0|())) p10: inc#() -> app#(s(),|0|()) 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(app(map(),f),nil()) -> nil() r4: app(app(map(),f),app(app(cons(),x),xs)) -> app(app(cons(),app(f,x)),app(app(map(),f),xs)) r5: inc() -> app(map(),app(plus(),app(s(),|0|()))) The estimated dependency graph contains the following SCCs: {p6, p7} {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) 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(app(map(),f),nil()) -> nil() r4: app(app(map(),f),app(app(cons(),x),xs)) -> app(app(cons(),app(f,x)),app(app(map(),f),xs)) r5: inc() -> app(map(),app(plus(),app(s(),|0|()))) The set of usable rules consists of (no rules) Take the reduction pair: weighted path order base order: matrix interpretations: carrier: N^2 order: standard order interpretations: app#_A(x1,x2) = ((1,0),(1,1)) x1 + (3,3) app_A(x1,x2) = x2 + (2,2) map_A() = (0,0) cons_A() = (1,1) precedence: app# = app = cons > map partial status: pi(app#) = [] pi(app) = [2] pi(map) = [] pi(cons) = [] The next rules are strictly ordered: p1 We remove them from the problem. -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: 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(app(map(),f),nil()) -> nil() r4: app(app(map(),f),app(app(cons(),x),xs)) -> app(app(cons(),app(f,x)),app(app(map(),f),xs)) r5: inc() -> app(map(),app(plus(),app(s(),|0|()))) The estimated dependency graph contains the following SCCs: {p1} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: 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(app(map(),f),nil()) -> nil() r4: app(app(map(),f),app(app(cons(),x),xs)) -> app(app(cons(),app(f,x)),app(app(map(),f),xs)) r5: inc() -> app(map(),app(plus(),app(s(),|0|()))) The set of usable rules consists of (no rules) Take the reduction pair: weighted path order base order: matrix interpretations: carrier: N^2 order: standard order interpretations: app#_A(x1,x2) = ((1,0),(1,0)) x2 + (4,3) app_A(x1,x2) = ((1,0),(0,0)) x2 + (2,2) map_A() = (1,1) cons_A() = (3,2) precedence: app# = app = map = cons partial status: pi(app#) = [] pi(app) = [] pi(map) = [] pi(cons) = [] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains. -- 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(app(map(),f),nil()) -> nil() r4: app(app(map(),f),app(app(cons(),x),xs)) -> app(app(cons(),app(f,x)),app(app(map(),f),xs)) r5: inc() -> app(map(),app(plus(),app(s(),|0|()))) The set of usable rules consists of (no rules) Take the reduction pair: weighted path order base order: matrix interpretations: carrier: N^2 order: standard order interpretations: app#_A(x1,x2) = ((1,0),(0,0)) x1 + x2 + (0,6) app_A(x1,x2) = x2 + (1,2) plus_A() = (3,5) s_A() = (4,1) precedence: app# = app > plus > s partial status: pi(app#) = [] pi(app) = [] pi(plus) = [] pi(s) = [] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.