YES # Compositional parallel rule labeling (Shintani and Hirokawa 2022). Consider the left-linear TRS R: s(p(x)) -> x p(s(x)) -> x +(x,0()) -> x +(x,s(y)) -> s(+(x,y)) +(x,p(y)) -> p(+(x,y)) -(0(),0()) -> 0() -(x,s(y)) -> p(-(x,y)) -(x,p(y)) -> s(-(x,y)) -(p(x),y) -> p(-(x,y)) -(s(x),y) -> s(-(x,y)) Let C be the following subset of R: s(p(x)) -> x p(s(x)) -> x +(x,0()) -> x +(x,s(y)) -> s(+(x,y)) +(x,p(y)) -> p(+(x,y)) -(0(),0()) -> 0() -(x,s(y)) -> p(-(x,y)) -(x,p(y)) -> s(-(x,y)) -(p(x),y) -> p(-(x,y)) -(s(x),y) -> s(-(x,y)) All parallel critical peaks (except C's) are decreasing wrt rule labeling: phi(s(p(x)) -> x) = 0 phi(p(s(x)) -> x) = 0 phi(+(x,0()) -> x) = 0 phi(+(x,s(y)) -> s(+(x,y))) = 0 phi(+(x,p(y)) -> p(+(x,y))) = 0 phi(-(0(),0()) -> 0()) = 0 phi(-(x,s(y)) -> p(-(x,y))) = 0 phi(-(x,p(y)) -> s(-(x,y))) = 0 phi(-(p(x),y) -> p(-(x,y))) = 0 phi(-(s(x),y) -> s(-(x,y))) = 0 psi(s(p(x)) -> x) = 0 psi(p(s(x)) -> x) = 0 psi(+(x,0()) -> x) = 0 psi(+(x,s(y)) -> s(+(x,y))) = 0 psi(+(x,p(y)) -> p(+(x,y))) = 0 psi(-(0(),0()) -> 0()) = 0 psi(-(x,s(y)) -> p(-(x,y))) = 0 psi(-(x,p(y)) -> s(-(x,y))) = 0 psi(-(p(x),y) -> p(-(x,y))) = 0 psi(-(s(x),y) -> s(-(x,y))) = 0 Therefore, the confluence of R follows from that of C. # Compositional parallel critical pair system (Shintani and Hirokawa 2022). Consider the left-linear TRS R: s(p(x)) -> x p(s(x)) -> x +(x,0()) -> x +(x,s(y)) -> s(+(x,y)) +(x,p(y)) -> p(+(x,y)) -(0(),0()) -> 0() -(x,s(y)) -> p(-(x,y)) -(x,p(y)) -> s(-(x,y)) -(p(x),y) -> p(-(x,y)) -(s(x),y) -> s(-(x,y)) Let C be the following subset of R: (empty) The parallel critical pair system PCPS(R,C) is: +(y1,s(p(x1_1))) -> +(y1,x1_1) +(y1,s(p(x1_1))) -> s(+(y1,p(x1_1))) +(y1,p(s(x1_1))) -> +(y1,x1_1) +(y1,p(s(x1_1))) -> p(+(y1,s(x1_1))) -(p(x0_1),s(y2)) -> p(-(x0_1,s(y2))) -(p(x0_1),s(y2)) -> p(-(p(x0_1),y2)) -(s(x0_1),s(y2)) -> s(-(x0_1,s(y2))) -(s(x0_1),s(y2)) -> p(-(s(x0_1),y2)) -(y1,s(p(x1_1))) -> -(y1,x1_1) -(y1,s(p(x1_1))) -> p(-(y1,p(x1_1))) -(p(x0_1),p(y2)) -> p(-(x0_1,p(y2))) -(p(x0_1),p(y2)) -> s(-(p(x0_1),y2)) -(s(x0_1),p(y2)) -> s(-(x0_1,p(y2))) -(s(x0_1),p(y2)) -> s(-(s(x0_1),y2)) -(y1,p(s(x1_1))) -> -(y1,x1_1) -(y1,p(s(x1_1))) -> s(-(y1,s(x1_1))) -(p(y1),s(x0_2)) -> p(-(p(y1),x0_2)) -(p(y1),s(x0_2)) -> p(-(y1,s(x0_2))) -(p(y1),p(x0_2)) -> s(-(p(y1),x0_2)) -(p(y1),p(x0_2)) -> p(-(y1,p(x0_2))) -(p(s(x1_1)),y2) -> -(x1_1,y2) -(p(s(x1_1)),y2) -> p(-(s(x1_1),y2)) -(s(y1),s(x0_2)) -> p(-(s(y1),x0_2)) -(s(y1),s(x0_2)) -> s(-(y1,s(x0_2))) -(s(y1),p(x0_2)) -> s(-(s(y1),x0_2)) -(s(y1),p(x0_2)) -> s(-(y1,p(x0_2))) -(s(p(x1_1)),y2) -> -(x1_1,y2) -(s(p(x1_1)),y2) -> s(-(p(x1_1),y2)) All pairs in PCP(R) are joinable and PCPS(R,C)/R is terminating. Therefore, the confluence of R follows from that of C. # emptiness The empty TRS is confluent.