YES ---- CR(R) ---- R : left-linear, C : CR and CP-closing, and Cdup/R : SN 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)) CP(R): f(s(d(0()))) -> +(+(g(0()),g(0())),g(0())) critical-pair-closing system C: f(s(x)) -> +(+(s(x),s(x)),s(x)) g(x) -> s(d(x)) CR(C): see below. ---- CR(R) ---- R : left-linear, C : CR and CP-closing, and Cdup/R : SN R: f(s(x)) -> +(+(s(x),s(x)),s(x)) g(x) -> s(d(x)) CP(R): critical-pair-closing system C: CR(C): see below. ---- CR(R) ---- R is empty.