YES ---- CR(R cup S) ---- [Klein and Hirokawa, 2012] R: +(x,0()) -> x +(x,s(y)) -> s(+(x,y)) d(0()) -> 0() d(s(x)) -> s(s(d(x))) f(0()) -> 0() f(s(x)) -> +(+(s(x),s(x)),s(x)) f(g(0())) -> +(+(g(0()),g(0())),g(0())) g(x) -> s(d(x)) S: CP_S(R): f(s(d(0()))) -> +(+(g(0()),g(0())),g(0())) CR(S): see below. ---- CR(R) ---- [Hirokawa and Middeldorp, 2011] R: CPS'(R): CP(R):