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(app(curry(),f),x),y) -> app(app(f,x),y) add() -> app(curry(),plus()) -- 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(app(curry(),f),x),y) -> app#(app(f,x),y) p5: app#(app(app(curry(),f),x),y) -> app#(f,x) p6: add#() -> app#(curry(),plus()) 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(app(curry(),f),x),y) -> app(app(f,x),y) r4: add() -> app(curry(),plus()) The estimated dependency graph contains the following SCCs: {p4, p5} {p2} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: app#(app(app(curry(),f),x),y) -> app#(f,x) p2: app#(app(app(curry(),f),x),y) -> app#(app(f,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(app(curry(),f),x),y) -> app(app(f,x),y) r4: add() -> app(curry(),plus()) The set of usable rules consists of r1, r2, r3 Take the reduction pair: weighted path order base order: max/plus interpretations on natural numbers: app#_A(x1,x2) = max{11, x1 + 7, x2 + 6} app_A(x1,x2) = max{x1 + 5, x2} curry_A = 0 plus_A = 2 |0|_A = 0 s_A = 1 precedence: app# = app > curry = plus = |0| = s partial status: pi(app#) = [] pi(app) = [] pi(curry) = [] pi(plus) = [] pi(|0|) = [] pi(s) = [] 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(app(curry(),f),x),y) -> app#(app(f,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(app(curry(),f),x),y) -> app(app(f,x),y) r4: add() -> app(curry(),plus()) 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(app(curry(),f),x),y) -> app#(app(f,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(app(curry(),f),x),y) -> app(app(f,x),y) r4: add() -> app(curry(),plus()) The set of usable rules consists of r1, r2, r3 Take the reduction pair: weighted path order base order: max/plus interpretations on natural numbers: app#_A(x1,x2) = max{x1, x2 + 2} app_A(x1,x2) = max{2, x1, x2} curry_A = 2 plus_A = 1 |0|_A = 0 s_A = 3 precedence: app# = app = curry = plus = |0| = s partial status: pi(app#) = [1] pi(app) = [1, 2] pi(curry) = [] pi(plus) = [] pi(|0|) = [] pi(s) = [] 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(app(curry(),f),x),y) -> app(app(f,x),y) r4: add() -> app(curry(),plus()) The set of usable rules consists of (no rules) Take the reduction pair: weighted path order base order: max/plus interpretations on natural numbers: app#_A(x1,x2) = max{0, x1 - 9} app_A(x1,x2) = max{x1 + 2, x2 + 4} plus_A = 2 s_A = 6 precedence: app# = app = plus = s partial status: pi(app#) = [] pi(app) = [1, 2] pi(plus) = [] pi(s) = [] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.