YES Problem: +(+(x,y),z) -> +(x,+(y,z)) +(f(x),f(y)) -> f(+(x,y)) +(f(x),+(f(y),z)) -> +(f(+(x,y)),z) Proof: Matrix Interpretation Processor: dim=1 interpretation: [f](x0) = 4x0 + 7, [+](x0, x1) = x0 + x1 + 2 orientation: +(+(x,y),z) = x + y + z + 4 >= x + y + z + 4 = +(x,+(y,z)) +(f(x),f(y)) = 4x + 4y + 16 >= 4x + 4y + 15 = f(+(x,y)) +(f(x),+(f(y),z)) = 4x + 4y + z + 18 >= 4x + 4y + z + 17 = +(f(+(x,y)),z) problem: +(+(x,y),z) -> +(x,+(y,z)) Matrix Interpretation Processor: dim=1 interpretation: [+](x0, x1) = 2x0 + x1 + 1 orientation: +(+(x,y),z) = 4x + 2y + z + 3 >= 2x + 2y + z + 2 = +(x,+(y,z)) problem: Qed