YES Problem: s(p(x)) -> x p(s(x)) -> x +(x,s(y)) -> s(+(x,y)) +(x,p(y)) -> p(+(x,y)) -(x,s(y)) -> p(-(x,y)) -(x,p(y)) -> s(-(x,y)) Proof: Church Rosser Transformation Processor (critical pair closing system, Thm 2.11): +(x129,p(x128)) -> p(+(x129,x128)) s(p(x132)) -> x132 -(x134,p(x133)) -> s(-(x134,x133)) p(s(x137)) -> x137 +(x139,s(x138)) -> s(+(x139,x138)) -(x144,s(x143)) -> p(-(x144,x143)) critical peaks: joinable Matrix Interpretation Processor: dim=1 interpretation: [s](x0) = x0 + 2, [-](x0, x1) = 4x0 + 2x1 + 2, [p](x0) = x0 + 1, [+](x0, x1) = x0 + x1 + 3 orientation: +(x129,p(x128)) = x128 + x129 + 4 >= x128 + x129 + 4 = p(+(x129,x128)) s(p(x132)) = x132 + 3 >= x132 = x132 -(x134,p(x133)) = 2x133 + 4x134 + 4 >= 2x133 + 4x134 + 4 = s(-(x134,x133)) p(s(x137)) = x137 + 3 >= x137 = x137 +(x139,s(x138)) = x138 + x139 + 5 >= x138 + x139 + 5 = s(+(x139,x138)) -(x144,s(x143)) = 2x143 + 4x144 + 6 >= 2x143 + 4x144 + 3 = p(-(x144,x143)) problem: +(x129,p(x128)) -> p(+(x129,x128)) -(x134,p(x133)) -> s(-(x134,x133)) +(x139,s(x138)) -> s(+(x139,x138)) Matrix Interpretation Processor: dim=1 interpretation: [s](x0) = x0, [-](x0, x1) = 2x0 + x1 + 2, [p](x0) = x0 + 4, [+](x0, x1) = x0 + 4x1 + 4 orientation: +(x129,p(x128)) = 4x128 + x129 + 20 >= 4x128 + x129 + 8 = p(+(x129,x128)) -(x134,p(x133)) = x133 + 2x134 + 6 >= x133 + 2x134 + 2 = s(-(x134,x133)) +(x139,s(x138)) = 4x138 + x139 + 4 >= 4x138 + x139 + 4 = s(+(x139,x138)) problem: +(x139,s(x138)) -> s(+(x139,x138)) Matrix Interpretation Processor: dim=1 interpretation: [s](x0) = x0 + 1, [+](x0, x1) = x0 + 4x1 + 7 orientation: +(x139,s(x138)) = 4x138 + x139 + 11 >= 4x138 + x139 + 8 = s(+(x139,x138)) problem: Qed