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: lexicographic combination of reduction pairs: 1. weighted path order base order: matrix interpretations: carrier: N^2 order: lexicographic order interpretations: app#_A(x1,x2) = x1 + (2,8) app_A(x1,x2) = ((1,0),(1,1)) x1 + x2 + (2,1) curry_A() = (1,5) plus_A() = (1,1) |0|_A() = (1,0) s_A() = (6,4) precedence: app# = app = curry = plus = |0| = s partial status: pi(app#) = [] pi(app) = [] pi(curry) = [] pi(plus) = [] pi(|0|) = [] pi(s) = [] 2. weighted path order base order: matrix interpretations: carrier: N^2 order: lexicographic order interpretations: app#_A(x1,x2) = (0,0) app_A(x1,x2) = ((0,0),(1,0)) x2 + (2,3) curry_A() = (1,1) plus_A() = (1,1) |0|_A() = (1,0) s_A() = (1,2) precedence: |0| > app = s > curry = plus > app# partial status: pi(app#) = [] pi(app) = [] pi(curry) = [] pi(plus) = [] pi(|0|) = [] pi(s) = [] The next rules are strictly ordered: p1, p2 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: lexicographic combination of reduction pairs: 1. weighted path order base order: matrix interpretations: carrier: N^2 order: lexicographic order interpretations: app#_A(x1,x2) = ((0,0),(1,0)) x1 + x2 + (4,1) app_A(x1,x2) = x2 + (3,8) plus_A() = (1,2) s_A() = (2,3) precedence: app# = app = plus = s partial status: pi(app#) = [] pi(app) = [] pi(plus) = [] pi(s) = [] 2. weighted path order base order: matrix interpretations: carrier: N^2 order: lexicographic order interpretations: app#_A(x1,x2) = x2 + (2,2) app_A(x1,x2) = (1,1) plus_A() = (0,0) s_A() = (0,0) precedence: app > app# = plus = s partial status: pi(app#) = [2] pi(app) = [] pi(plus) = [] pi(s) = [] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.