YES We show the termination of the TRS R: double(|0|()) -> |0|() double(s(x)) -> s(s(double(x))) +(x,|0|()) -> x +(x,s(y)) -> s(+(x,y)) +(s(x),y) -> s(+(x,y)) double(x) -> +(x,x) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: double#(s(x)) -> double#(x) p2: +#(x,s(y)) -> +#(x,y) p3: +#(s(x),y) -> +#(x,y) p4: double#(x) -> +#(x,x) and R consists of: r1: double(|0|()) -> |0|() r2: double(s(x)) -> s(s(double(x))) r3: +(x,|0|()) -> x r4: +(x,s(y)) -> s(+(x,y)) r5: +(s(x),y) -> s(+(x,y)) r6: double(x) -> +(x,x) The estimated dependency graph contains the following SCCs: {p1} {p2, p3} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: double#(s(x)) -> double#(x) and R consists of: r1: double(|0|()) -> |0|() r2: double(s(x)) -> s(s(double(x))) r3: +(x,|0|()) -> x r4: +(x,s(y)) -> s(+(x,y)) r5: +(s(x),y) -> s(+(x,y)) r6: double(x) -> +(x,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: double#_A(x1) = max{4, x1 + 3} s_A(x1) = max{3, x1 + 2} precedence: double# = s partial status: pi(double#) = [1] pi(s) = [1] 2. weighted path order base order: max/plus interpretations on natural numbers: double#_A(x1) = max{1, x1 - 1} s_A(x1) = x1 precedence: double# = s partial status: pi(double#) = [] 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: +#(x,s(y)) -> +#(x,y) p2: +#(s(x),y) -> +#(x,y) and R consists of: r1: double(|0|()) -> |0|() r2: double(s(x)) -> s(s(double(x))) r3: +(x,|0|()) -> x r4: +(x,s(y)) -> s(+(x,y)) r5: +(s(x),y) -> s(+(x,y)) r6: double(x) -> +(x,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: +#_A(x1,x2) = max{3, x1 + 1, x2 + 1} s_A(x1) = max{2, x1 + 1} precedence: +# = s partial status: pi(+#) = [1, 2] pi(s) = [] 2. weighted path order base order: max/plus interpretations on natural numbers: +#_A(x1,x2) = x1 + 1 s_A(x1) = 0 precedence: +# = s partial status: pi(+#) = [] pi(s) = [] The next rules are strictly ordered: p2 We remove them from the problem. -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: +#(x,s(y)) -> +#(x,y) and R consists of: r1: double(|0|()) -> |0|() r2: double(s(x)) -> s(s(double(x))) r3: +(x,|0|()) -> x r4: +(x,s(y)) -> s(+(x,y)) r5: +(s(x),y) -> s(+(x,y)) r6: double(x) -> +(x,x) The estimated dependency graph contains the following SCCs: {p1} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: +#(x,s(y)) -> +#(x,y) and R consists of: r1: double(|0|()) -> |0|() r2: double(s(x)) -> s(s(double(x))) r3: +(x,|0|()) -> x r4: +(x,s(y)) -> s(+(x,y)) r5: +(s(x),y) -> s(+(x,y)) r6: double(x) -> +(x,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: +#_A(x1,x2) = max{2, x1, x2 + 1} s_A(x1) = max{1, x1} precedence: +# = s partial status: pi(+#) = [1, 2] pi(s) = [1] 2. weighted path order base order: max/plus interpretations on natural numbers: +#_A(x1,x2) = max{x1, x2 - 1} s_A(x1) = x1 precedence: +# = s partial status: pi(+#) = [1] pi(s) = [1] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.