YES We show the termination of the TRS R: |:|(x,x) -> e() |:|(x,e()) -> x i(|:|(x,y)) -> |:|(y,x) |:|(|:|(x,y),z) -> |:|(x,|:|(z,i(y))) |:|(e(),x) -> i(x) i(i(x)) -> x i(e()) -> e() |:|(x,|:|(y,i(x))) -> i(y) |:|(x,|:|(y,|:|(i(x),z))) -> |:|(i(z),y) |:|(i(x),|:|(y,x)) -> i(y) |:|(i(x),|:|(y,|:|(x,z))) -> |:|(i(z),y) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: i#(|:|(x,y)) -> |:|#(y,x) p2: |:|#(|:|(x,y),z) -> |:|#(x,|:|(z,i(y))) p3: |:|#(|:|(x,y),z) -> |:|#(z,i(y)) p4: |:|#(|:|(x,y),z) -> i#(y) p5: |:|#(e(),x) -> i#(x) p6: |:|#(x,|:|(y,i(x))) -> i#(y) p7: |:|#(x,|:|(y,|:|(i(x),z))) -> |:|#(i(z),y) p8: |:|#(x,|:|(y,|:|(i(x),z))) -> i#(z) p9: |:|#(i(x),|:|(y,x)) -> i#(y) p10: |:|#(i(x),|:|(y,|:|(x,z))) -> |:|#(i(z),y) p11: |:|#(i(x),|:|(y,|:|(x,z))) -> i#(z) and R consists of: r1: |:|(x,x) -> e() r2: |:|(x,e()) -> x r3: i(|:|(x,y)) -> |:|(y,x) r4: |:|(|:|(x,y),z) -> |:|(x,|:|(z,i(y))) r5: |:|(e(),x) -> i(x) r6: i(i(x)) -> x r7: i(e()) -> e() r8: |:|(x,|:|(y,i(x))) -> i(y) r9: |:|(x,|:|(y,|:|(i(x),z))) -> |:|(i(z),y) r10: |:|(i(x),|:|(y,x)) -> i(y) r11: |:|(i(x),|:|(y,|:|(x,z))) -> |:|(i(z),y) The estimated dependency graph contains the following SCCs: {p1, p2, p3, p4, p5, p6, p7, p8, p9, p10, p11} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: i#(|:|(x,y)) -> |:|#(y,x) p2: |:|#(i(x),|:|(y,|:|(x,z))) -> i#(z) p3: |:|#(i(x),|:|(y,|:|(x,z))) -> |:|#(i(z),y) p4: |:|#(i(x),|:|(y,x)) -> i#(y) p5: |:|#(x,|:|(y,|:|(i(x),z))) -> i#(z) p6: |:|#(x,|:|(y,|:|(i(x),z))) -> |:|#(i(z),y) p7: |:|#(x,|:|(y,i(x))) -> i#(y) p8: |:|#(e(),x) -> i#(x) p9: |:|#(|:|(x,y),z) -> i#(y) p10: |:|#(|:|(x,y),z) -> |:|#(z,i(y)) p11: |:|#(|:|(x,y),z) -> |:|#(x,|:|(z,i(y))) and R consists of: r1: |:|(x,x) -> e() r2: |:|(x,e()) -> x r3: i(|:|(x,y)) -> |:|(y,x) r4: |:|(|:|(x,y),z) -> |:|(x,|:|(z,i(y))) r5: |:|(e(),x) -> i(x) r6: i(i(x)) -> x r7: i(e()) -> e() r8: |:|(x,|:|(y,i(x))) -> i(y) r9: |:|(x,|:|(y,|:|(i(x),z))) -> |:|(i(z),y) r10: |:|(i(x),|:|(y,x)) -> i(y) r11: |:|(i(x),|:|(y,|:|(x,z))) -> |:|(i(z),y) The set of usable rules consists of r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11 Take the reduction pair: matrix interpretations: carrier: N^4 order: lexicographic order interpretations: i#_A(x1) = ((0,0,0,0),(0,0,0,0),(0,0,0,0),(1,0,0,0)) x1 + (0,0,0,1) |:|_A(x1,x2) = ((1,0,0,0),(1,0,0,0),(0,1,0,0),(0,1,0,0)) x1 + x2 + (2,2,1,1) |:|#_A(x1,x2) = ((0,0,0,0),(0,0,0,0),(0,0,0,0),(1,0,0,0)) x1 + ((0,0,0,0),(0,0,0,0),(0,0,0,0),(1,0,0,0)) x2 i_A(x1) = ((1,0,0,0),(1,1,0,0),(0,0,0,0),(0,0,0,0)) x1 + (0,4,3,3) e_A() = (1,1,4,4) The next rules are strictly ordered: p1, p2, p3, p4, p5, p6, p7, p9, p10 We remove them from the problem. -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: |:|#(e(),x) -> i#(x) p2: |:|#(|:|(x,y),z) -> |:|#(x,|:|(z,i(y))) and R consists of: r1: |:|(x,x) -> e() r2: |:|(x,e()) -> x r3: i(|:|(x,y)) -> |:|(y,x) r4: |:|(|:|(x,y),z) -> |:|(x,|:|(z,i(y))) r5: |:|(e(),x) -> i(x) r6: i(i(x)) -> x r7: i(e()) -> e() r8: |:|(x,|:|(y,i(x))) -> i(y) r9: |:|(x,|:|(y,|:|(i(x),z))) -> |:|(i(z),y) r10: |:|(i(x),|:|(y,x)) -> i(y) r11: |:|(i(x),|:|(y,|:|(x,z))) -> |:|(i(z),y) The estimated dependency graph contains the following SCCs: {p2} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: |:|#(|:|(x,y),z) -> |:|#(x,|:|(z,i(y))) and R consists of: r1: |:|(x,x) -> e() r2: |:|(x,e()) -> x r3: i(|:|(x,y)) -> |:|(y,x) r4: |:|(|:|(x,y),z) -> |:|(x,|:|(z,i(y))) r5: |:|(e(),x) -> i(x) r6: i(i(x)) -> x r7: i(e()) -> e() r8: |:|(x,|:|(y,i(x))) -> i(y) r9: |:|(x,|:|(y,|:|(i(x),z))) -> |:|(i(z),y) r10: |:|(i(x),|:|(y,x)) -> i(y) r11: |:|(i(x),|:|(y,|:|(x,z))) -> |:|(i(z),y) The set of usable rules consists of r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11 Take the reduction pair: matrix interpretations: carrier: N^4 order: lexicographic order interpretations: |:|#_A(x1,x2) = ((0,0,0,0),(1,0,0,0),(0,0,0,0),(1,1,0,0)) x1 |:|_A(x1,x2) = ((1,0,0,0),(1,0,0,0),(0,1,0,0),(0,1,0,0)) x1 + ((1,0,0,0),(0,0,0,0),(0,1,0,0),(0,1,0,0)) x2 + (2,2,1,4) i_A(x1) = ((1,0,0,0),(1,1,0,0),(0,0,1,0),(0,1,0,0)) x1 + (0,1,7,1) e_A() = (1,5,2,5) The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.