Problem: -(x,x) -> 0() -(x,0()) -> x +(x,y) -> +(y,x) +(0(),x) -> x +(x,0()) -> x +(s(x),y) -> s(+(x,y)) +(x,s(y)) -> s(+(y,x)) +(p(x),y) -> p(+(x,y)) +(x,p(y)) -> p(+(y,x)) s(p(x)) -> x p(s(x)) -> x Proof: sorted: (order) 0:-(x,x) -> 0() -(x,0()) -> x 1:+(x,y) -> +(y,x) +(0(),x) -> x +(x,0()) -> x +(s(x),y) -> s(+(x,y)) +(x,s(y)) -> s(+(y,x)) +(p(x),y) -> p(+(x,y)) +(x,p(y)) -> p(+(y,x)) s(p(x)) -> x p(s(x)) -> x ----- sorts [0>1, 1>3, 2>3] sort attachment (non-strict) - : 1 x 1 -> 0 0 : 3 + : 2 x 2 -> 2 s : 2 -> 2 p : 2 -> 2 ----- 0:-(x,x) -> 0() -(x,0()) -> x Church Rosser Transformation Processor (kb): -(x,x) -> 0() -(x,0()) -> x critical peaks: joinable Matrix Interpretation Processor: dim=1 interpretation: [0] = 1, [-](x0, x1) = 4x0 + 2x1 + 1 orientation: -(x,x) = 6x + 1 >= 1 = 0() -(x,0()) = 4x + 3 >= x = x problem: -(x,x) -> 0() Matrix Interpretation Processor: dim=1 interpretation: [0] = 0, [-](x0, x1) = x0 + 4x1 + 1 orientation: -(x,x) = 5x + 1 >= 0 = 0() problem: Qed 1:+(x,y) -> +(y,x) +(0(),x) -> x +(x,0()) -> x +(s(x),y) -> s(+(x,y)) +(x,s(y)) -> s(+(y,x)) +(p(x),y) -> p(+(x,y)) +(x,p(y)) -> p(+(y,x)) s(p(x)) -> x p(s(x)) -> x AT confluence processor Complete TRS T' of input TRS: +(0(),x) -> x +(x,0()) -> x +(s(x),y) -> s(+(x,y)) +(x,s(y)) -> s(+(y,x)) +(p(x),y) -> p(+(x,y)) +(x,p(y)) -> p(+(y,x)) s(p(x)) -> x p(s(x)) -> x +(x,y) -> +(y,x) T' = (P union S) with TRS P:+(x,y) -> +(y,x) TRS S:+(0(),x) -> x +(x,0()) -> x +(s(x),y) -> s(+(x,y)) +(x,s(y)) -> s(+(y,x)) +(p(x),y) -> p(+(x,y)) +(x,p(y)) -> p(+(y,x)) s(p(x)) -> x p(s(x)) -> x S is left-linear and P is reversible. CP(S,S) = 0() = 0(), s(y) = s(+(y,0())), p(y) = p(+(y,0())), s(x) = s(+(x,0())), p(x) = p(+(x,0())), s(+(x512,0())) = s(x512), s(+(x514,s(y))) = s(+(y,s(x514))), s(+(x516,p(y))) = p(+(y,s(x516))), s(+(x519,0())) = s(x519), s(+(x521,s(x))) = s(+(x,s(x521))), s(+(x523,p(x))) = p(+(x,s(x523))), p(+(x524,0())) = p(x524), p(+(x526,s(y))) = s(+(y,p(x526))), p(+(x528,p(y))) = p(+(y,p(x528))), p(+(x531,0())) = p(x531), p(+(x533,s(x))) = s(+(x,p(x533))), p(+(x535,p(x))) = p(+(x,p(x535))), +(x536,y) = s(+(p(x536),y)), +(x,x537) = s(+(p(x537),x)), p(x538) = p(x538), +(x539,y) = p(+(s(x539),y)), +(x,x540) = p(+(s(x540),x)), s(x541) = s(x541) CP(S,P union P^-1) = y = +(y,0()), x = +(x,0()), x = +(0(),x), y = +(0(),y), s(+(x570,y)) = +(y,s(x570)), s(+(x572,x)) = +(x,s(x572)), s(+(x575,x)) = +(s(x575),x), s(+(x577,y)) = +(s(x577),y), p(+(x578,y)) = +(y,p(x578)), p(+(x580,x)) = +(x,p(x580)), p(+(x583,x)) = +(p(x583),x), p(+(x585,y)) = +(p(x585),y) PCP_in(P union P^-1,S) = We have to check termination of S: Matrix Interpretation Processor: dim=1 interpretation: [p](x0) = x0, [0] = 0, [s](x0) = x0 + 5, [+](x0, x1) = x0 + x1 + 5 orientation: +(0(),x) = x + 5 >= x = x +(x,0()) = x + 5 >= x = x +(s(x),y) = x + y + 10 >= x + y + 10 = s(+(x,y)) +(x,s(y)) = x + y + 10 >= x + y + 10 = s(+(y,x)) +(p(x),y) = x + y + 5 >= x + y + 5 = p(+(x,y)) +(x,p(y)) = x + y + 5 >= x + y + 5 = p(+(y,x)) s(p(x)) = x + 5 >= x = x p(s(x)) = x + 5 >= x = x problem: +(s(x),y) -> s(+(x,y)) +(x,s(y)) -> s(+(y,x)) +(p(x),y) -> p(+(x,y)) +(x,p(y)) -> p(+(y,x)) Matrix Interpretation Processor: dim=1 interpretation: [p](x0) = x0 + 4, [s](x0) = x0, [+](x0, x1) = 4x0 + 4x1 orientation: +(s(x),y) = 4x + 4y >= 4x + 4y = s(+(x,y)) +(x,s(y)) = 4x + 4y >= 4x + 4y = s(+(y,x)) +(p(x),y) = 4x + 4y + 16 >= 4x + 4y + 4 = p(+(x,y)) +(x,p(y)) = 4x + 4y + 16 >= 4x + 4y + 4 = p(+(y,x)) problem: +(s(x),y) -> s(+(x,y)) +(x,s(y)) -> s(+(y,x)) Matrix Interpretation Processor: dim=1 interpretation: [s](x0) = x0 + 1, [+](x0, x1) = 2x0 + 2x1 orientation: +(s(x),y) = 2x + 2y + 2 >= 2x + 2y + 1 = s(+(x,y)) +(x,s(y)) = 2x + 2y + 2 >= 2x + 2y + 1 = s(+(y,x)) problem: Qed