YES We show the termination of the TRS R: le(|0|(),y) -> true() le(s(x),|0|()) -> false() le(s(x),s(y)) -> le(x,y) minus(x,|0|()) -> x minus(s(x),s(y)) -> minus(x,y) mod(|0|(),y) -> |0|() mod(s(x),|0|()) -> |0|() mod(s(x),s(y)) -> if_mod(le(y,x),s(x),s(y)) if_mod(true(),s(x),s(y)) -> mod(minus(x,y),s(y)) if_mod(false(),s(x),s(y)) -> s(x) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: le#(s(x),s(y)) -> le#(x,y) p2: minus#(s(x),s(y)) -> minus#(x,y) p3: mod#(s(x),s(y)) -> if_mod#(le(y,x),s(x),s(y)) p4: mod#(s(x),s(y)) -> le#(y,x) p5: if_mod#(true(),s(x),s(y)) -> mod#(minus(x,y),s(y)) p6: if_mod#(true(),s(x),s(y)) -> minus#(x,y) and R consists of: r1: le(|0|(),y) -> true() r2: le(s(x),|0|()) -> false() r3: le(s(x),s(y)) -> le(x,y) r4: minus(x,|0|()) -> x r5: minus(s(x),s(y)) -> minus(x,y) r6: mod(|0|(),y) -> |0|() r7: mod(s(x),|0|()) -> |0|() r8: mod(s(x),s(y)) -> if_mod(le(y,x),s(x),s(y)) r9: if_mod(true(),s(x),s(y)) -> mod(minus(x,y),s(y)) r10: if_mod(false(),s(x),s(y)) -> s(x) The estimated dependency graph contains the following SCCs: {p3, p5} {p1} {p2} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: if_mod#(true(),s(x),s(y)) -> mod#(minus(x,y),s(y)) p2: mod#(s(x),s(y)) -> if_mod#(le(y,x),s(x),s(y)) and R consists of: r1: le(|0|(),y) -> true() r2: le(s(x),|0|()) -> false() r3: le(s(x),s(y)) -> le(x,y) r4: minus(x,|0|()) -> x r5: minus(s(x),s(y)) -> minus(x,y) r6: mod(|0|(),y) -> |0|() r7: mod(s(x),|0|()) -> |0|() r8: mod(s(x),s(y)) -> if_mod(le(y,x),s(x),s(y)) r9: if_mod(true(),s(x),s(y)) -> mod(minus(x,y),s(y)) r10: if_mod(false(),s(x),s(y)) -> s(x) The set of usable rules consists of r1, r2, r3, r4, r5 Take the reduction pair: matrix interpretations: carrier: N^4 order: lexicographic order interpretations: if_mod#_A(x1,x2,x3) = ((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),(1,0,0,0),(0,0,0,0)) x2 + ((1,0,0,0),(1,0,0,0),(0,1,0,0),(0,0,1,0)) x3 true_A() = (1,1,0,1) s_A(x1) = ((1,0,0,0),(1,0,0,0),(1,1,0,0),(1,1,1,0)) x1 + (3,1,1,0) mod#_A(x1,x2) = ((0,0,0,0),(0,0,0,0),(1,0,0,0),(1,0,0,0)) x1 + ((1,0,0,0),(1,0,0,0),(0,1,0,0),(0,1,1,0)) x2 + (0,0,1,0) minus_A(x1,x2) = ((1,0,0,0),(0,1,0,0),(0,1,1,0),(0,1,1,1)) x1 + (1,1,1,1) le_A(x1,x2) = ((0,0,0,0),(0,0,0,0),(1,0,0,0),(0,0,0,0)) x1 + ((1,0,0,0),(0,0,0,0),(0,0,0,0),(0,1,0,0)) x2 + (2,0,1,2) |0|_A() = (1,1,0,1) false_A() = (0,1,5,4) The next rules are strictly ordered: p1, p2 We remove them from the problem. Then no dependency pair remains. -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: le#(s(x),s(y)) -> le#(x,y) and R consists of: r1: le(|0|(),y) -> true() r2: le(s(x),|0|()) -> false() r3: le(s(x),s(y)) -> le(x,y) r4: minus(x,|0|()) -> x r5: minus(s(x),s(y)) -> minus(x,y) r6: mod(|0|(),y) -> |0|() r7: mod(s(x),|0|()) -> |0|() r8: mod(s(x),s(y)) -> if_mod(le(y,x),s(x),s(y)) r9: if_mod(true(),s(x),s(y)) -> mod(minus(x,y),s(y)) r10: if_mod(false(),s(x),s(y)) -> s(x) The set of usable rules consists of (no rules) Take the monotone reduction pair: matrix interpretations: carrier: N^4 order: lexicographic order interpretations: le#_A(x1,x2) = ((1,0,0,0),(0,1,0,0),(0,0,1,0),(1,1,0,1)) x1 + ((1,0,0,0),(1,1,0,0),(1,1,1,0),(1,0,1,1)) x2 s_A(x1) = ((1,0,0,0),(1,1,0,0),(1,0,1,0),(1,1,1,1)) x1 + (1,1,1,1) The next rules are strictly ordered: p1 r1, r2, r3, r4, r5, r6, r7, r8, r9, r10 We remove them from the problem. Then no dependency pair remains. -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: minus#(s(x),s(y)) -> minus#(x,y) and R consists of: r1: le(|0|(),y) -> true() r2: le(s(x),|0|()) -> false() r3: le(s(x),s(y)) -> le(x,y) r4: minus(x,|0|()) -> x r5: minus(s(x),s(y)) -> minus(x,y) r6: mod(|0|(),y) -> |0|() r7: mod(s(x),|0|()) -> |0|() r8: mod(s(x),s(y)) -> if_mod(le(y,x),s(x),s(y)) r9: if_mod(true(),s(x),s(y)) -> mod(minus(x,y),s(y)) r10: if_mod(false(),s(x),s(y)) -> s(x) The set of usable rules consists of (no rules) Take the monotone reduction pair: matrix interpretations: carrier: N^4 order: lexicographic order interpretations: minus#_A(x1,x2) = ((1,0,0,0),(1,1,0,0),(0,0,1,0),(1,1,0,1)) x1 + ((1,0,0,0),(0,1,0,0),(1,1,1,0),(1,0,1,1)) x2 s_A(x1) = ((1,0,0,0),(1,1,0,0),(1,1,1,0),(1,1,1,1)) x1 + (1,1,1,1) The next rules are strictly ordered: p1 r1, r2, r3, r4, r5, r6, r7, r8, r9, r10 We remove them from the problem. Then no dependency pair remains.