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(app(treemap(),f),app(app(node(),x),xs)) -> app(app(node(),app(f,x)),app(app(map(),app(treemap(),f)),xs)) -- 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(cons(),app(f,x)),app(app(map(),f),xs)) p2: app#(app(map(),f),app(app(cons(),x),xs)) -> app#(cons(),app(f,x)) p3: app#(app(map(),f),app(app(cons(),x),xs)) -> app#(f,x) p4: app#(app(map(),f),app(app(cons(),x),xs)) -> app#(app(map(),f),xs) p5: app#(app(treemap(),f),app(app(node(),x),xs)) -> app#(app(node(),app(f,x)),app(app(map(),app(treemap(),f)),xs)) p6: app#(app(treemap(),f),app(app(node(),x),xs)) -> app#(node(),app(f,x)) p7: app#(app(treemap(),f),app(app(node(),x),xs)) -> app#(f,x) p8: app#(app(treemap(),f),app(app(node(),x),xs)) -> app#(app(map(),app(treemap(),f)),xs) p9: app#(app(treemap(),f),app(app(node(),x),xs)) -> app#(map(),app(treemap(),f)) and R consists of: r1: app(app(map(),f),nil()) -> nil() r2: app(app(map(),f),app(app(cons(),x),xs)) -> app(app(cons(),app(f,x)),app(app(map(),f),xs)) r3: app(app(treemap(),f),app(app(node(),x),xs)) -> app(app(node(),app(f,x)),app(app(map(),app(treemap(),f)),xs)) The estimated dependency graph contains the following SCCs: {p3, p4, p7, p8} -- 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(treemap(),f),app(app(node(),x),xs)) -> app#(app(map(),app(treemap(),f)),xs) p3: app#(app(map(),f),app(app(cons(),x),xs)) -> app#(app(map(),f),xs) p4: app#(app(treemap(),f),app(app(node(),x),xs)) -> app#(f,x) and R consists of: r1: app(app(map(),f),nil()) -> nil() r2: app(app(map(),f),app(app(cons(),x),xs)) -> app(app(cons(),app(f,x)),app(app(map(),f),xs)) r3: app(app(treemap(),f),app(app(node(),x),xs)) -> app(app(node(),app(f,x)),app(app(map(),app(treemap(),f)),xs)) The set of usable rules consists of (no rules) Take the reduction pair: lexicographic path order with precedence: precedence: app > map > treemap > app# > node > cons argument filter: pi(app#) = 2 pi(app) = [1, 2] pi(map) = [] pi(cons) = [] pi(treemap) = [] pi(node) = [] The next rules are strictly ordered: p1, p2, p3, p4 We remove them from the problem. Then no dependency pair remains.