YES We show the termination of the TRS R: minus(x,|0|()) -> x minus(s(x),s(y)) -> minus(x,y) f(|0|()) -> s(|0|()) f(s(x)) -> minus(s(x),g(f(x))) g(|0|()) -> |0|() g(s(x)) -> minus(s(x),f(g(x))) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: minus#(s(x),s(y)) -> minus#(x,y) p2: f#(s(x)) -> minus#(s(x),g(f(x))) p3: f#(s(x)) -> g#(f(x)) p4: f#(s(x)) -> f#(x) p5: g#(s(x)) -> minus#(s(x),f(g(x))) p6: g#(s(x)) -> f#(g(x)) p7: g#(s(x)) -> g#(x) and R consists of: r1: minus(x,|0|()) -> x r2: minus(s(x),s(y)) -> minus(x,y) r3: f(|0|()) -> s(|0|()) r4: f(s(x)) -> minus(s(x),g(f(x))) r5: g(|0|()) -> |0|() r6: g(s(x)) -> minus(s(x),f(g(x))) The estimated dependency graph contains the following SCCs: {p3, p4, p6, p7} {p1} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: g#(s(x)) -> g#(x) p2: g#(s(x)) -> f#(g(x)) p3: f#(s(x)) -> f#(x) p4: f#(s(x)) -> g#(f(x)) and R consists of: r1: minus(x,|0|()) -> x r2: minus(s(x),s(y)) -> minus(x,y) r3: f(|0|()) -> s(|0|()) r4: f(s(x)) -> minus(s(x),g(f(x))) r5: g(|0|()) -> |0|() r6: g(s(x)) -> minus(s(x),f(g(x))) The set of usable rules consists of r1, r2, r3, r4, r5, r6 Take the reduction pair: lexicographic combination of reduction pairs: 1. weighted path order base order: max/plus interpretations on natural numbers: g#_A(x1) = max{24, x1 + 17} s_A(x1) = max{24, x1 + 17} f#_A(x1) = max{19, x1 + 18} g_A(x1) = max{14, x1 + 5} f_A(x1) = max{24, x1 + 11} minus_A(x1,x2) = max{23, x1 + 5, x2 + 2} |0|_A = 7 precedence: g# = f# = g = f > s = minus = |0| partial status: pi(g#) = [1] pi(s) = [1] pi(f#) = [1] pi(g) = [1] pi(f) = [1] pi(minus) = [1, 2] pi(|0|) = [] 2. weighted path order base order: max/plus interpretations on natural numbers: g#_A(x1) = max{6, x1 - 4} s_A(x1) = max{13, x1 + 11} f#_A(x1) = max{5, x1 + 4} g_A(x1) = x1 + 1 f_A(x1) = x1 + 19 minus_A(x1,x2) = max{45, x1 + 20, x2 + 32} |0|_A = 12 precedence: g# = s = f# = g = f = minus = |0| partial status: pi(g#) = [] pi(s) = [1] pi(f#) = [1] pi(g) = [1] pi(f) = [] pi(minus) = [] pi(|0|) = [] The next rules are strictly ordered: p1, p2, p3, p4 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: minus(x,|0|()) -> x r2: minus(s(x),s(y)) -> minus(x,y) r3: f(|0|()) -> s(|0|()) r4: f(s(x)) -> minus(s(x),g(f(x))) r5: g(|0|()) -> |0|() r6: g(s(x)) -> minus(s(x),f(g(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: minus#_A(x1,x2) = max{2, x1 - 1, x2 + 1} s_A(x1) = max{1, x1} precedence: minus# = s partial status: pi(minus#) = [2] pi(s) = [1] 2. weighted path order base order: max/plus interpretations on natural numbers: minus#_A(x1,x2) = 0 s_A(x1) = max{2, x1} precedence: minus# = s partial status: pi(minus#) = [] pi(s) = [1] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.