YES We show the termination of the TRS R: f(+(x,|0|())) -> f(x) +(x,+(y,z)) -> +(+(x,y),z) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: f#(+(x,|0|())) -> f#(x) p2: +#(x,+(y,z)) -> +#(+(x,y),z) p3: +#(x,+(y,z)) -> +#(x,y) and R consists of: r1: f(+(x,|0|())) -> f(x) r2: +(x,+(y,z)) -> +(+(x,y),z) 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: f#(+(x,|0|())) -> f#(x) and R consists of: r1: f(+(x,|0|())) -> f(x) r2: +(x,+(y,z)) -> +(+(x,y),z) The set of usable rules consists of (no rules) Take the reduction pair: lexicographic combination of reduction pairs: 1. matrix interpretations: carrier: N^1 order: standard order interpretations: f#_A(x1) = x1 +_A(x1,x2) = x1 + 1 |0|_A() = 1 2. matrix interpretations: carrier: N^1 order: standard order interpretations: f#_A(x1) = 0 +_A(x1,x2) = x1 + 1 |0|_A() = 1 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: +#(x,+(y,z)) -> +#(+(x,y),z) p2: +#(x,+(y,z)) -> +#(x,y) and R consists of: r1: f(+(x,|0|())) -> f(x) r2: +(x,+(y,z)) -> +(+(x,y),z) The set of usable rules consists of r2 Take the reduction pair: lexicographic combination of reduction pairs: 1. matrix interpretations: carrier: N^1 order: standard order interpretations: +#_A(x1,x2) = x2 +_A(x1,x2) = x1 + x2 + 1 2. matrix interpretations: carrier: N^1 order: standard order interpretations: +#_A(x1,x2) = x2 +_A(x1,x2) = x1 + x2 + 1 The next rules are strictly ordered: p1, p2 We remove them from the problem. Then no dependency pair remains.