YES We show the termination of the TRS R: minus(minus(x)) -> x minus(+(x,y)) -> *(minus(minus(minus(x))),minus(minus(minus(y)))) minus(*(x,y)) -> +(minus(minus(minus(x))),minus(minus(minus(y)))) f(minus(x)) -> minus(minus(minus(f(x)))) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: minus#(+(x,y)) -> minus#(minus(minus(x))) p2: minus#(+(x,y)) -> minus#(minus(x)) p3: minus#(+(x,y)) -> minus#(x) p4: minus#(+(x,y)) -> minus#(minus(minus(y))) p5: minus#(+(x,y)) -> minus#(minus(y)) p6: minus#(+(x,y)) -> minus#(y) p7: minus#(*(x,y)) -> minus#(minus(minus(x))) p8: minus#(*(x,y)) -> minus#(minus(x)) p9: minus#(*(x,y)) -> minus#(x) p10: minus#(*(x,y)) -> minus#(minus(minus(y))) p11: minus#(*(x,y)) -> minus#(minus(y)) p12: minus#(*(x,y)) -> minus#(y) p13: f#(minus(x)) -> minus#(minus(minus(f(x)))) p14: f#(minus(x)) -> minus#(minus(f(x))) p15: f#(minus(x)) -> minus#(f(x)) p16: f#(minus(x)) -> f#(x) and R consists of: r1: minus(minus(x)) -> x r2: minus(+(x,y)) -> *(minus(minus(minus(x))),minus(minus(minus(y)))) r3: minus(*(x,y)) -> +(minus(minus(minus(x))),minus(minus(minus(y)))) r4: f(minus(x)) -> minus(minus(minus(f(x)))) The estimated dependency graph contains the following SCCs: {p16} {p1, p2, p3, p4, p5, p6, p7, p8, p9, p10, p11, p12} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: f#(minus(x)) -> f#(x) and R consists of: r1: minus(minus(x)) -> x r2: minus(+(x,y)) -> *(minus(minus(minus(x))),minus(minus(minus(y)))) r3: minus(*(x,y)) -> +(minus(minus(minus(x))),minus(minus(minus(y)))) r4: f(minus(x)) -> minus(minus(minus(f(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: f#_A(x1) = max{4, x1 + 3} minus_A(x1) = max{3, x1 + 2} precedence: f# = minus partial status: pi(f#) = [1] pi(minus) = [1] 2. weighted path order base order: max/plus interpretations on natural numbers: f#_A(x1) = max{1, x1 - 1} minus_A(x1) = x1 precedence: f# = minus partial status: pi(f#) = [] pi(minus) = [1] The next rules are strictly ordered: p1 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#(+(x,y)) -> minus#(minus(minus(x))) p2: minus#(*(x,y)) -> minus#(y) p3: minus#(*(x,y)) -> minus#(minus(y)) p4: minus#(*(x,y)) -> minus#(minus(minus(y))) p5: minus#(*(x,y)) -> minus#(x) p6: minus#(*(x,y)) -> minus#(minus(x)) p7: minus#(*(x,y)) -> minus#(minus(minus(x))) p8: minus#(+(x,y)) -> minus#(y) p9: minus#(+(x,y)) -> minus#(minus(y)) p10: minus#(+(x,y)) -> minus#(minus(minus(y))) p11: minus#(+(x,y)) -> minus#(x) p12: minus#(+(x,y)) -> minus#(minus(x)) and R consists of: r1: minus(minus(x)) -> x r2: minus(+(x,y)) -> *(minus(minus(minus(x))),minus(minus(minus(y)))) r3: minus(*(x,y)) -> +(minus(minus(minus(x))),minus(minus(minus(y)))) r4: f(minus(x)) -> minus(minus(minus(f(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: minus#_A(x1) = x1 + 4 +_A(x1,x2) = max{x1 + 2, x2 + 2} minus_A(x1) = x1 *_A(x1,x2) = max{x1 + 2, x2 + 2} precedence: minus# = + = minus = * partial status: pi(minus#) = [1] pi(+) = [1, 2] pi(minus) = [1] pi(*) = [1, 2] 2. weighted path order base order: max/plus interpretations on natural numbers: minus#_A(x1) = x1 + 18 +_A(x1,x2) = max{20, x1 + 17, x2 + 17} minus_A(x1) = x1 + 6 *_A(x1,x2) = max{x1 + 13, x2 + 13} precedence: minus# = + = minus = * partial status: pi(minus#) = [1] pi(+) = [] pi(minus) = [] pi(*) = [2] The next rules are strictly ordered: p1, p2, p3, p4, p5, p6, p7, p8, p9, p10, p11, p12 We remove them from the problem. Then no dependency pair remains.