YES We show the termination of the relative TRS R/S: R: rev(nil()) -> nil() rev(cons(x,l)) -> cons(rev1(x,l),rev2(x,l)) rev1(|0|(),nil()) -> |0|() rev1(s(x),nil()) -> s(x) rev1(x,cons(y,l)) -> rev1(y,l) rev2(x,nil()) -> nil() rev2(x,cons(y,l)) -> rev(cons(x,rev2(y,l))) S: rand(x) -> x rand(x) -> rand(s(x)) -- SCC decomposition. Consider the non-minimal dependency pair problem (P, R), where P consists of p1: rev#(cons(x,l)) -> rev1#(x,l) p2: rev#(cons(x,l)) -> rev2#(x,l) p3: rev1#(x,cons(y,l)) -> rev1#(y,l) p4: rev2#(x,cons(y,l)) -> rev#(cons(x,rev2(y,l))) p5: rev2#(x,cons(y,l)) -> rev2#(y,l) and R consists of: r1: rev(nil()) -> nil() r2: rev(cons(x,l)) -> cons(rev1(x,l),rev2(x,l)) r3: rev1(|0|(),nil()) -> |0|() r4: rev1(s(x),nil()) -> s(x) r5: rev1(x,cons(y,l)) -> rev1(y,l) r6: rev2(x,nil()) -> nil() r7: rev2(x,cons(y,l)) -> rev(cons(x,rev2(y,l))) r8: rand(x) -> x r9: rand(x) -> rand(s(x)) The estimated dependency graph contains the following SCCs: {p2, p4, p5} {p3} -- Reduction pair. Consider the non-minimal dependency pair problem (P, R), where P consists of p1: rev2#(x,cons(y,l)) -> rev#(cons(x,rev2(y,l))) p2: rev#(cons(x,l)) -> rev2#(x,l) p3: rev2#(x,cons(y,l)) -> rev2#(y,l) and R consists of: r1: rev(nil()) -> nil() r2: rev(cons(x,l)) -> cons(rev1(x,l),rev2(x,l)) r3: rev1(|0|(),nil()) -> |0|() r4: rev1(s(x),nil()) -> s(x) r5: rev1(x,cons(y,l)) -> rev1(y,l) r6: rev2(x,nil()) -> nil() r7: rev2(x,cons(y,l)) -> rev(cons(x,rev2(y,l))) r8: rand(x) -> x r9: rand(x) -> rand(s(x)) The set of usable rules consists of r1, r2, r3, r4, r5, r6, r7, r8, r9 Take the reduction pair: weighted path order base order: matrix interpretations: carrier: N^1 order: lexicographic order interpretations: rev2#_A(x1,x2) = x2 + 1 cons_A(x1,x2) = x2 + 3 rev#_A(x1) = x1 rev2_A(x1,x2) = x2 rev_A(x1) = x1 nil_A() = 2 rev1_A(x1,x2) = 2 |0|_A() = 1 s_A(x1) = 0 rand_A(x1) = x1 + 1 precedence: s > rev1 = |0| = rand > rev2 = rev > rev2# = cons = rev# = nil partial status: pi(rev2#) = [] pi(cons) = [] pi(rev#) = [] pi(rev2) = [2] pi(rev) = [1] pi(nil) = [] pi(rev1) = [] pi(|0|) = [] pi(s) = [] pi(rand) = [] The next rules are strictly ordered: p1 We remove them from the problem. -- SCC decomposition. Consider the non-minimal dependency pair problem (P, R), where P consists of p1: rev#(cons(x,l)) -> rev2#(x,l) p2: rev2#(x,cons(y,l)) -> rev2#(y,l) and R consists of: r1: rev(nil()) -> nil() r2: rev(cons(x,l)) -> cons(rev1(x,l),rev2(x,l)) r3: rev1(|0|(),nil()) -> |0|() r4: rev1(s(x),nil()) -> s(x) r5: rev1(x,cons(y,l)) -> rev1(y,l) r6: rev2(x,nil()) -> nil() r7: rev2(x,cons(y,l)) -> rev(cons(x,rev2(y,l))) r8: rand(x) -> x r9: rand(x) -> rand(s(x)) The estimated dependency graph contains the following SCCs: {p2} -- Reduction pair. Consider the non-minimal dependency pair problem (P, R), where P consists of p1: rev2#(x,cons(y,l)) -> rev2#(y,l) and R consists of: r1: rev(nil()) -> nil() r2: rev(cons(x,l)) -> cons(rev1(x,l),rev2(x,l)) r3: rev1(|0|(),nil()) -> |0|() r4: rev1(s(x),nil()) -> s(x) r5: rev1(x,cons(y,l)) -> rev1(y,l) r6: rev2(x,nil()) -> nil() r7: rev2(x,cons(y,l)) -> rev(cons(x,rev2(y,l))) r8: rand(x) -> x r9: rand(x) -> rand(s(x)) The set of usable rules consists of r1, r2, r3, r4, r5, r6, r7, r8, r9 Take the reduction pair: weighted path order base order: matrix interpretations: carrier: N^1 order: lexicographic order interpretations: rev2#_A(x1,x2) = x2 cons_A(x1,x2) = x2 + 1 rev_A(x1) = x1 nil_A() = 2 rev1_A(x1,x2) = 2 rev2_A(x1,x2) = x2 |0|_A() = 1 s_A(x1) = 0 rand_A(x1) = x1 + 1 precedence: rand > rev1 = s > rev2 > rev > cons = nil = |0| > rev2# partial status: pi(rev2#) = [] pi(cons) = [2] pi(rev) = [] pi(nil) = [] pi(rev1) = [] pi(rev2) = [] pi(|0|) = [] pi(s) = [] pi(rand) = [] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains. -- Reduction pair. Consider the non-minimal dependency pair problem (P, R), where P consists of p1: rev1#(x,cons(y,l)) -> rev1#(y,l) and R consists of: r1: rev(nil()) -> nil() r2: rev(cons(x,l)) -> cons(rev1(x,l),rev2(x,l)) r3: rev1(|0|(),nil()) -> |0|() r4: rev1(s(x),nil()) -> s(x) r5: rev1(x,cons(y,l)) -> rev1(y,l) r6: rev2(x,nil()) -> nil() r7: rev2(x,cons(y,l)) -> rev(cons(x,rev2(y,l))) r8: rand(x) -> x r9: rand(x) -> rand(s(x)) The set of usable rules consists of r1, r2, r3, r4, r5, r6, r7, r8, r9 Take the reduction pair: weighted path order base order: matrix interpretations: carrier: N^1 order: lexicographic order interpretations: rev1#_A(x1,x2) = x2 cons_A(x1,x2) = x2 + 1 rev_A(x1) = x1 nil_A() = 2 rev1_A(x1,x2) = 2 rev2_A(x1,x2) = x2 |0|_A() = 1 s_A(x1) = 0 rand_A(x1) = x1 + 1 precedence: rand > rev1 = s > rev2 > rev > cons = nil = |0| > rev1# partial status: pi(rev1#) = [] pi(cons) = [2] pi(rev) = [] pi(nil) = [] pi(rev1) = [] pi(rev2) = [] pi(|0|) = [] pi(s) = [] pi(rand) = [] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.