Problem: +(x,0()) -> x +(x,s(y)) -> s(+(x,y)) +(0(),y) -> y +(s(x),y) -> s(+(x,y)) inc(x) -> s(x) +(x,y) -> +(y,x) inc(+(x,y)) -> +(inc(x),y) Proof: AT confluence processor Complete TRS T' of input TRS: +(x,0()) -> x +(x,s(y)) -> s(+(x,y)) +(0(),y) -> y +(s(x),y) -> s(+(x,y)) inc(x) -> s(x) inc(+(x,y)) -> +(inc(x),y) +(x,y) -> +(y,x) T' = (P union S) with TRS P:+(x,y) -> +(y,x) TRS S:+(x,0()) -> x +(x,s(y)) -> s(+(x,y)) +(0(),y) -> y +(s(x),y) -> s(+(x,y)) inc(x) -> s(x) inc(+(x,y)) -> +(inc(x),y) S is linear and P is reversible. CP(S,S) = 0() = 0(), s(x) = s(+(x,0())), inc(x) = +(inc(x),0()), s(+(0(),x319)) = s(x319), s(+(s(x),x321)) = s(+(x,s(x321))), inc(s(+(x,x323))) = +(inc(x),s(x323)), s(y) = s(+(0(),y)), inc(y) = +(inc(0()),y), s(+(x327,0())) = s(x327), s(+(x329,s(y))) = s(+(s(x329),y)), inc(s(+(x331,y))) = +(inc(s(x331)),y), s(+(x,y)) = +(inc(x),y), +(inc(x334),x335) = s(+(x334,x335)) CP(S,P union P^-1) = x = +(0(),x), y = +(0(),y), s(+(x,x357)) = +(s(x357),x), s(+(y,x359)) = +(s(x359),y), y = +(y,0()), x = +(x,0()), s(+(x362,y)) = +(y,s(x362)), s(+(x364,x)) = +(x,s(x364)) CP(P union P^-1,S) = +(0(),x) = x, +(s(y),x) = s(+(x,y)), +(y,0()) = y, +(y,s(x)) = s(+(x,y)), inc(+(y,x)) = +(inc(x),y) We have to check termination of S: Matrix Interpretation Processor: dim=1 interpretation: [+](x0, x1) = x0 + x1 + 2, [inc](x0) = x0, [0] = 1, [s](x0) = x0 orientation: +(x,0()) = x + 3 >= x = x +(x,s(y)) = x + y + 2 >= x + y + 2 = s(+(x,y)) +(0(),y) = y + 3 >= y = y +(s(x),y) = x + y + 2 >= x + y + 2 = s(+(x,y)) inc(x) = x >= x = s(x) inc(+(x,y)) = x + y + 2 >= x + y + 2 = +(inc(x),y) problem: +(x,s(y)) -> s(+(x,y)) +(s(x),y) -> s(+(x,y)) inc(x) -> s(x) inc(+(x,y)) -> +(inc(x),y) Matrix Interpretation Processor: dim=1 interpretation: [+](x0, x1) = 4x0 + 4x1 + 4, [inc](x0) = 4x0 + 4, [s](x0) = x0 orientation: +(x,s(y)) = 4x + 4y + 4 >= 4x + 4y + 4 = s(+(x,y)) +(s(x),y) = 4x + 4y + 4 >= 4x + 4y + 4 = s(+(x,y)) inc(x) = 4x + 4 >= x = s(x) inc(+(x,y)) = 16x + 16y + 20 >= 16x + 4y + 20 = +(inc(x),y) problem: +(x,s(y)) -> s(+(x,y)) +(s(x),y) -> s(+(x,y)) inc(+(x,y)) -> +(inc(x),y) Matrix Interpretation Processor: dim=1 interpretation: [+](x0, x1) = 2x0 + 7x1 + 2, [inc](x0) = 3x0 + 1, [s](x0) = x0 orientation: +(x,s(y)) = 2x + 7y + 2 >= 2x + 7y + 2 = s(+(x,y)) +(s(x),y) = 2x + 7y + 2 >= 2x + 7y + 2 = s(+(x,y)) inc(+(x,y)) = 6x + 21y + 7 >= 6x + 7y + 4 = +(inc(x),y) problem: +(x,s(y)) -> s(+(x,y)) +(s(x),y) -> s(+(x,y)) Matrix Interpretation Processor: dim=1 interpretation: [+](x0, x1) = 2x0 + x1 + 1, [s](x0) = x0 + 1 orientation: +(x,s(y)) = 2x + y + 2 >= 2x + y + 2 = s(+(x,y)) +(s(x),y) = 2x + y + 3 >= 2x + y + 2 = s(+(x,y)) problem: +(x,s(y)) -> s(+(x,y)) Matrix Interpretation Processor: dim=1 interpretation: [+](x0, x1) = x0 + 4x1, [s](x0) = x0 + 5 orientation: +(x,s(y)) = x + 4y + 20 >= x + 4y + 5 = s(+(x,y)) problem: Qed