YES Problem: i(0()) -> 0() +(0(),y) -> y +(x,0()) -> x i(i(x)) -> x +(i(x),x) -> 0() +(x,i(x)) -> 0() i(+(x,y)) -> +(i(x),i(y)) +(x,+(y,z)) -> +(+(x,y),z) +(+(x,i(y)),y) -> x +(+(x,y),i(y)) -> x Proof: Matrix Interpretation Processor: dim=1 interpretation: [+](x0, x1) = x0 + x1 + 3, [i](x0) = 3x0 + 4, [0] = 5 orientation: i(0()) = 19 >= 5 = 0() +(0(),y) = y + 8 >= y = y +(x,0()) = x + 8 >= x = x i(i(x)) = 9x + 16 >= x = x +(i(x),x) = 4x + 7 >= 5 = 0() +(x,i(x)) = 4x + 7 >= 5 = 0() i(+(x,y)) = 3x + 3y + 13 >= 3x + 3y + 11 = +(i(x),i(y)) +(x,+(y,z)) = x + y + z + 6 >= x + y + z + 6 = +(+(x,y),z) +(+(x,i(y)),y) = x + 4y + 10 >= x = x +(+(x,y),i(y)) = x + 4y + 10 >= x = x problem: +(x,+(y,z)) -> +(+(x,y),z) Matrix Interpretation Processor: dim=1 interpretation: [+](x0, x1) = x0 + 4x1 + 3 orientation: +(x,+(y,z)) = x + 4y + 16z + 15 >= x + 4y + 4z + 6 = +(+(x,y),z) problem: Qed