Problem: -(+(x,y)) -> +(-(x),-(y)) -(-(x)) -> x +(+(x,y),z) -> +(x,+(y,z)) +(x,y) -> +(y,x) Proof: AT confluence processor Complete TRS T' of input TRS: -(+(x,y)) -> +(-(x),-(y)) -(-(x)) -> x +(+(x,y),z) -> +(x,+(y,z)) +(x,y) -> +(y,x) T' = (P union S) with TRS P:+(+(x,y),z) -> +(x,+(y,z)) +(x,y) -> +(y,x) TRS S:-(+(x,y)) -> +(-(x),-(y)) -(-(x)) -> x S is linear and P is reversible. CP(S,S) = -(+(-(x98),-(x99))) = +(x98,x99), -(x100) = -(x100) CP(S,P union P^-1) = CP(P union P^-1,S) = -(+(x159,+(x160,y))) = +(-(+(x159,x160)),-(y)), -(+(y,x)) = +(-(x),-(y)), -(+(+(x,x165),x166)) = +(-(x),-(+(x165,x166))) We have to check termination of S: Matrix Interpretation Processor: dim=1 interpretation: [-](x0) = 2x0 + 1, [+](x0, x1) = x0 + x1 + 1 orientation: -(+(x,y)) = 2x + 2y + 3 >= 2x + 2y + 3 = +(-(x),-(y)) -(-(x)) = 4x + 3 >= x = x problem: -(+(x,y)) -> +(-(x),-(y)) Matrix Interpretation Processor: dim=1 interpretation: [-](x0) = 4x0, [+](x0, x1) = 2x0 + x1 + 4 orientation: -(+(x,y)) = 8x + 4y + 16 >= 8x + 4y + 4 = +(-(x),-(y)) problem: Qed