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(|0|(),y) -> |0|() minus(s(x),y) -> if_minus(le(s(x),y),s(x),y) if_minus(true(),s(x),y) -> |0|() if_minus(false(),s(x),y) -> s(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),y) -> if_minus#(le(s(x),y),s(x),y) p3: minus#(s(x),y) -> le#(s(x),y) p4: if_minus#(false(),s(x),y) -> minus#(x,y) p5: mod#(s(x),s(y)) -> if_mod#(le(y,x),s(x),s(y)) p6: mod#(s(x),s(y)) -> le#(y,x) p7: if_mod#(true(),s(x),s(y)) -> mod#(minus(x,y),s(y)) p8: 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(|0|(),y) -> |0|() r5: minus(s(x),y) -> if_minus(le(s(x),y),s(x),y) r6: if_minus(true(),s(x),y) -> |0|() r7: if_minus(false(),s(x),y) -> s(minus(x,y)) r8: mod(|0|(),y) -> |0|() r9: mod(s(x),|0|()) -> |0|() r10: mod(s(x),s(y)) -> if_mod(le(y,x),s(x),s(y)) r11: if_mod(true(),s(x),s(y)) -> mod(minus(x,y),s(y)) r12: if_mod(false(),s(x),s(y)) -> s(x) The estimated dependency graph contains the following SCCs: {p5, p7} {p2, p4} {p1} -- 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(|0|(),y) -> |0|() r5: minus(s(x),y) -> if_minus(le(s(x),y),s(x),y) r6: if_minus(true(),s(x),y) -> |0|() r7: if_minus(false(),s(x),y) -> s(minus(x,y)) r8: mod(|0|(),y) -> |0|() r9: mod(s(x),|0|()) -> |0|() r10: mod(s(x),s(y)) -> if_mod(le(y,x),s(x),s(y)) r11: if_mod(true(),s(x),s(y)) -> mod(minus(x,y),s(y)) r12: if_mod(false(),s(x),s(y)) -> s(x) The set of usable rules consists of r1, r2, r3, r4, r5, r6, r7 Take the reduction pair: lexicographic combination of reduction pairs: 1. weighted path order base order: max/plus interpretations on natural numbers: if_mod#_A(x1,x2,x3) = max{x1 + 20, x2 + 1} true_A = 17 s_A(x1) = x1 + 63 mod#_A(x1,x2) = max{64, x1 + 5} minus_A(x1,x2) = x1 + 59 le_A(x1,x2) = x2 + 38 if_minus_A(x1,x2,x3) = x2 + 59 |0|_A = 0 false_A = 37 precedence: if_mod# > true = mod# = minus = le > if_minus > s = |0| = false partial status: pi(if_mod#) = [1, 2] pi(true) = [] pi(s) = [1] pi(mod#) = [1] pi(minus) = [1] pi(le) = [] pi(if_minus) = [2] pi(|0|) = [] pi(false) = [] 2. weighted path order base order: max/plus interpretations on natural numbers: if_mod#_A(x1,x2,x3) = max{1, x1 - 6, x2 - 5} true_A = 16 s_A(x1) = max{14, x1 + 10} mod#_A(x1,x2) = x1 minus_A(x1,x2) = max{2, x1} le_A(x1,x2) = 15 if_minus_A(x1,x2,x3) = max{15, x2 + 5} |0|_A = 3 false_A = 9 precedence: if_mod# = true = s = mod# = minus = le = if_minus = |0| = false partial status: pi(if_mod#) = [] pi(true) = [] pi(s) = [1] pi(mod#) = [1] pi(minus) = [1] pi(le) = [] pi(if_minus) = [] pi(|0|) = [] pi(false) = [] 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: if_minus#(false(),s(x),y) -> minus#(x,y) p2: minus#(s(x),y) -> if_minus#(le(s(x),y),s(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(|0|(),y) -> |0|() r5: minus(s(x),y) -> if_minus(le(s(x),y),s(x),y) r6: if_minus(true(),s(x),y) -> |0|() r7: if_minus(false(),s(x),y) -> s(minus(x,y)) r8: mod(|0|(),y) -> |0|() r9: mod(s(x),|0|()) -> |0|() r10: mod(s(x),s(y)) -> if_mod(le(y,x),s(x),s(y)) r11: if_mod(true(),s(x),s(y)) -> mod(minus(x,y),s(y)) r12: if_mod(false(),s(x),s(y)) -> s(x) The set of usable rules consists of r1, r2, r3 Take the reduction pair: lexicographic combination of reduction pairs: 1. weighted path order base order: max/plus interpretations on natural numbers: if_minus#_A(x1,x2,x3) = max{x1 + 2, x2 + 1, x3 + 4} false_A = 4 s_A(x1) = x1 + 5 minus#_A(x1,x2) = max{x1 + 6, x2 + 4} le_A(x1,x2) = max{x1 + 3, x2 - 6} |0|_A = 11 true_A = 12 precedence: if_minus# = s = minus# = le = |0| > false = true partial status: pi(if_minus#) = [2] pi(false) = [] pi(s) = [1] pi(minus#) = [1] pi(le) = [] pi(|0|) = [] pi(true) = [] 2. weighted path order base order: max/plus interpretations on natural numbers: if_minus#_A(x1,x2,x3) = max{1, x2} false_A = 7 s_A(x1) = x1 + 8 minus#_A(x1,x2) = x1 le_A(x1,x2) = 1 |0|_A = 0 true_A = 2 precedence: true > if_minus# = false = s = minus# = le = |0| partial status: pi(if_minus#) = [] pi(false) = [] pi(s) = [1] pi(minus#) = [1] pi(le) = [] pi(|0|) = [] pi(true) = [] 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(|0|(),y) -> |0|() r5: minus(s(x),y) -> if_minus(le(s(x),y),s(x),y) r6: if_minus(true(),s(x),y) -> |0|() r7: if_minus(false(),s(x),y) -> s(minus(x,y)) r8: mod(|0|(),y) -> |0|() r9: mod(s(x),|0|()) -> |0|() r10: mod(s(x),s(y)) -> if_mod(le(y,x),s(x),s(y)) r11: if_mod(true(),s(x),s(y)) -> mod(minus(x,y),s(y)) r12: if_mod(false(),s(x),s(y)) -> s(x) The set of usable rules consists of (no rules) Take the reduction pair: lexicographic combination of reduction pairs: 1. weighted path order base order: max/plus interpretations on natural numbers: le#_A(x1,x2) = max{2, x1 - 1, x2 + 1} s_A(x1) = max{1, x1} precedence: le# = s partial status: pi(le#) = [2] pi(s) = [1] 2. weighted path order base order: max/plus interpretations on natural numbers: le#_A(x1,x2) = 0 s_A(x1) = max{2, x1} precedence: le# = s partial status: pi(le#) = [] pi(s) = [1] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.