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)) 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(map_0(),y) -> map_1(y) app(map_1(x1),y) -> map_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)) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: app#(map_1(x1),y) -> map_2#(x1,y) p2: map_2#(f,cons_2(x,xs)) -> app#(f,x) p3: map_2#(f,cons_2(x,xs)) -> map_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(map_0(),y) -> map_1(y) r4: app(map_1(x1),y) -> map_2(x1,y) r5: map_2(f,nil_0()) -> nil_0() r6: map_2(f,cons_2(x,xs)) -> cons_2(app(f,x),map_2(f,xs)) The estimated dependency graph contains the following SCCs: {p1, p2, p3} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: app#(map_1(x1),y) -> map_2#(x1,y) p2: map_2#(f,cons_2(x,xs)) -> map_2#(f,xs) p3: map_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(map_0(),y) -> map_1(y) r4: app(map_1(x1),y) -> map_2(x1,y) r5: map_2(f,nil_0()) -> nil_0() r6: map_2(f,cons_2(x,xs)) -> cons_2(app(f,x),map_2(f,xs)) The set of usable rules consists of (no rules) 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: lexicographic combination of reduction triples: 1. marked-algebra reduction triple (>=A, >=A!, >A!): matrix interpretation with standard point-wise order: carrier: N^1 order: standard order interpretations: app#_A(x1,x2) = x2 map_1_A(x1) = x1 + 3 map_2#_A(x1,x2) = x2 cons_2_A(x1,x2) = x1 + x2 + 5 app#!_A(x1,x2) = x2 + 6 map_1!_A(x1) = x1 + 3 map_2#!_A(x1,x2) = x2 + 2 cons_2!_A(x1,x2) = 5 2. marked-algebra reduction triple (>=A, >=A!, >A!): max/plus interpretation on natural numbers: app#_A(x1,x2) = max{0, x1 - 9, x2 - 5} map_1_A(x1) = x1 + 8 map_2#_A(x1,x2) = max{0, x1 - 9, x2 - 5} cons_2_A(x1,x2) = max{4, x1, x2 + 1} app#!_A(x1,x2) = max{5, x1 - 9, x2 - 1} map_1!_A(x1) = x1 + 1 map_2#!_A(x1,x2) = 0 cons_2!_A(x1,x2) = 4 partial status: pi(app#) = [] pi(map_1) = [] pi(map_2#) = [] pi(cons_2) = [] The following rules are removed: p1, p2, p3 Then no dependency pair remains.