YES We show the termination of the TRS R: minus(x,|0|()) -> x minus(s(x),s(y)) -> minus(x,y) double(|0|()) -> |0|() double(s(x)) -> s(s(double(x))) plus(|0|(),y) -> y plus(s(x),y) -> s(plus(x,y)) plus(s(x),y) -> plus(x,s(y)) plus(s(x),y) -> s(plus(minus(x,y),double(y))) plus(s(plus(x,y)),z) -> s(plus(plus(x,y),z)) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: minus#(s(x),s(y)) -> minus#(x,y) p2: double#(s(x)) -> double#(x) p3: plus#(s(x),y) -> plus#(x,y) p4: plus#(s(x),y) -> plus#(x,s(y)) p5: plus#(s(x),y) -> plus#(minus(x,y),double(y)) p6: plus#(s(x),y) -> minus#(x,y) p7: plus#(s(x),y) -> double#(y) p8: plus#(s(plus(x,y)),z) -> plus#(plus(x,y),z) and R consists of: r1: minus(x,|0|()) -> x r2: minus(s(x),s(y)) -> minus(x,y) r3: double(|0|()) -> |0|() r4: double(s(x)) -> s(s(double(x))) r5: plus(|0|(),y) -> y r6: plus(s(x),y) -> s(plus(x,y)) r7: plus(s(x),y) -> plus(x,s(y)) r8: plus(s(x),y) -> s(plus(minus(x,y),double(y))) r9: plus(s(plus(x,y)),z) -> s(plus(plus(x,y),z)) The estimated dependency graph contains the following SCCs: {p3, p4, p5, p8} {p1} {p2} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: plus#(s(plus(x,y)),z) -> plus#(plus(x,y),z) p2: plus#(s(x),y) -> plus#(minus(x,y),double(y)) p3: plus#(s(x),y) -> plus#(x,s(y)) p4: plus#(s(x),y) -> plus#(x,y) and R consists of: r1: minus(x,|0|()) -> x r2: minus(s(x),s(y)) -> minus(x,y) r3: double(|0|()) -> |0|() r4: double(s(x)) -> s(s(double(x))) r5: plus(|0|(),y) -> y r6: plus(s(x),y) -> s(plus(x,y)) r7: plus(s(x),y) -> plus(x,s(y)) r8: plus(s(x),y) -> s(plus(minus(x,y),double(y))) r9: plus(s(plus(x,y)),z) -> s(plus(plus(x,y),z)) The set of usable rules consists of r1, r2, r3, r4, r5, r6, r7, r8, r9 Take the reduction pair: lexicographic combination of reduction pairs: 1. lexicographic path order with precedence: precedence: |0| > s > double > minus > plus > plus# argument filter: pi(plus#) = [1, 2] pi(s) = 1 pi(plus) = [1, 2] pi(minus) = 1 pi(double) = 1 pi(|0|) = [] 2. lexicographic path order with precedence: precedence: |0| > double > minus > plus > s > plus# argument filter: pi(plus#) = 1 pi(s) = [1] pi(plus) = [1] pi(minus) = 1 pi(double) = [1] 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: double(|0|()) -> |0|() r4: double(s(x)) -> s(s(double(x))) r5: plus(|0|(),y) -> y r6: plus(s(x),y) -> s(plus(x,y)) r7: plus(s(x),y) -> plus(x,s(y)) r8: plus(s(x),y) -> s(plus(minus(x,y),double(y))) r9: plus(s(plus(x,y)),z) -> s(plus(plus(x,y),z)) The set of usable rules consists of (no rules) Take the reduction pair: lexicographic combination of reduction pairs: 1. lexicographic path order with precedence: precedence: s > minus# argument filter: pi(minus#) = [2] pi(s) = [1] 2. lexicographic path order with precedence: precedence: s > minus# argument filter: pi(minus#) = [2] pi(s) = [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: double#(s(x)) -> double#(x) and R consists of: r1: minus(x,|0|()) -> x r2: minus(s(x),s(y)) -> minus(x,y) r3: double(|0|()) -> |0|() r4: double(s(x)) -> s(s(double(x))) r5: plus(|0|(),y) -> y r6: plus(s(x),y) -> s(plus(x,y)) r7: plus(s(x),y) -> plus(x,s(y)) r8: plus(s(x),y) -> s(plus(minus(x,y),double(y))) r9: plus(s(plus(x,y)),z) -> s(plus(plus(x,y),z)) The set of usable rules consists of (no rules) Take the monotone reduction pair: lexicographic combination of reduction pairs: 1. lexicographic path order with precedence: precedence: s > double# argument filter: pi(double#) = [1] pi(s) = 1 2. lexicographic path order with precedence: precedence: s > double# argument filter: pi(double#) = [1] pi(s) = [1] The next rules are strictly ordered: p1 r1, r2, r3, r4, r5, r6, r7, r8, r9 We remove them from the problem. Then no dependency pair remains.