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)) -(0(),x) -> 0() -(x,0()) -> x -(s(x),s(y)) -> -(x,y) CP(R): 0() -> 0() 0() -> 0() critical-pair-closing system C: CR(C): see below. ---- CR(R) ---- R is empty.