YES We show the termination of the TRS R: +(x,|0|()) -> x +(x,s(y)) -> s(+(x,y)) +(|0|(),s(y)) -> s(y) s(+(|0|(),y)) -> s(y) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: +#(x,s(y)) -> s#(+(x,y)) p2: +#(x,s(y)) -> +#(x,y) p3: s#(+(|0|(),y)) -> s#(y) and R consists of: r1: +(x,|0|()) -> x r2: +(x,s(y)) -> s(+(x,y)) r3: +(|0|(),s(y)) -> s(y) r4: s(+(|0|(),y)) -> s(y) The estimated dependency graph contains the following SCCs: {p2} {p3} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: +#(x,s(y)) -> +#(x,y) and R consists of: r1: +(x,|0|()) -> x r2: +(x,s(y)) -> s(+(x,y)) r3: +(|0|(),s(y)) -> s(y) r4: s(+(|0|(),y)) -> s(y) The set of usable rules consists of (no rules) Take the reduction pair: weighted path order base order: matrix interpretations: carrier: N^2 order: standard order interpretations: +#_A(x1,x2) = x1 + ((0,1),(0,0)) x2 + (2,2) s_A(x1) = ((0,0),(0,1)) x1 + (1,1) precedence: +# = s partial status: pi(+#) = [] 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: s#(+(|0|(),y)) -> s#(y) and R consists of: r1: +(x,|0|()) -> x r2: +(x,s(y)) -> s(+(x,y)) r3: +(|0|(),s(y)) -> s(y) r4: s(+(|0|(),y)) -> s(y) The set of usable rules consists of (no rules) Take the reduction pair: weighted path order base order: matrix interpretations: carrier: N^2 order: standard order interpretations: s#_A(x1) = ((0,1),(0,0)) x1 + (1,2) +_A(x1,x2) = ((0,1),(1,1)) x2 + (2,2) |0|_A() = (2,1) precedence: + > s# > |0| partial status: pi(s#) = [] pi(+) = [] pi(|0|) = [] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.