YES ---- CR(R) ---- Rule Labeling [van Oostrom, RTA 2008]. R: +(x,0()) -> x +(x,s(y)) -> s(+(x,y)) +(0(),y) -> y +(s(x),y) -> s(+(x,y)) inc(x) -> s(x) +(x,y) -> +(y,x) inc(+(x,y)) -> +(inc(x),y) Label: [+(x,0()) -> x] = 4 [+(x,s(y)) -> s(+(x,y))] = 4 [+(0(),y) -> y] = 4 [+(s(x),y) -> s(+(x,y))] = 4 [inc(x) -> s(x)] = 0 [+(x,y) -> +(y,x)] = 8 [inc(+(x,y)) -> +(inc(x),y)] = 7