YES We show the termination of the TRS R: from(X) -> cons(X,n__from(n__s(X))) head(cons(X,XS)) -> X |2nd|(cons(X,XS)) -> head(activate(XS)) take(|0|(),XS) -> nil() take(s(N),cons(X,XS)) -> cons(X,n__take(N,activate(XS))) sel(|0|(),cons(X,XS)) -> X sel(s(N),cons(X,XS)) -> sel(N,activate(XS)) from(X) -> n__from(X) s(X) -> n__s(X) take(X1,X2) -> n__take(X1,X2) activate(n__from(X)) -> from(activate(X)) activate(n__s(X)) -> s(activate(X)) activate(n__take(X1,X2)) -> take(activate(X1),activate(X2)) activate(X) -> X -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: |2nd|#(cons(X,XS)) -> head#(activate(XS)) p2: |2nd|#(cons(X,XS)) -> activate#(XS) p3: take#(s(N),cons(X,XS)) -> activate#(XS) p4: sel#(s(N),cons(X,XS)) -> sel#(N,activate(XS)) p5: sel#(s(N),cons(X,XS)) -> activate#(XS) p6: activate#(n__from(X)) -> from#(activate(X)) p7: activate#(n__from(X)) -> activate#(X) p8: activate#(n__s(X)) -> s#(activate(X)) p9: activate#(n__s(X)) -> activate#(X) p10: activate#(n__take(X1,X2)) -> take#(activate(X1),activate(X2)) p11: activate#(n__take(X1,X2)) -> activate#(X1) p12: activate#(n__take(X1,X2)) -> activate#(X2) and R consists of: r1: from(X) -> cons(X,n__from(n__s(X))) r2: head(cons(X,XS)) -> X r3: |2nd|(cons(X,XS)) -> head(activate(XS)) r4: take(|0|(),XS) -> nil() r5: take(s(N),cons(X,XS)) -> cons(X,n__take(N,activate(XS))) r6: sel(|0|(),cons(X,XS)) -> X r7: sel(s(N),cons(X,XS)) -> sel(N,activate(XS)) r8: from(X) -> n__from(X) r9: s(X) -> n__s(X) r10: take(X1,X2) -> n__take(X1,X2) r11: activate(n__from(X)) -> from(activate(X)) r12: activate(n__s(X)) -> s(activate(X)) r13: activate(n__take(X1,X2)) -> take(activate(X1),activate(X2)) r14: activate(X) -> X The estimated dependency graph contains the following SCCs: {p4} {p3, p7, p9, p10, p11, p12} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: sel#(s(N),cons(X,XS)) -> sel#(N,activate(XS)) and R consists of: r1: from(X) -> cons(X,n__from(n__s(X))) r2: head(cons(X,XS)) -> X r3: |2nd|(cons(X,XS)) -> head(activate(XS)) r4: take(|0|(),XS) -> nil() r5: take(s(N),cons(X,XS)) -> cons(X,n__take(N,activate(XS))) r6: sel(|0|(),cons(X,XS)) -> X r7: sel(s(N),cons(X,XS)) -> sel(N,activate(XS)) r8: from(X) -> n__from(X) r9: s(X) -> n__s(X) r10: take(X1,X2) -> n__take(X1,X2) r11: activate(n__from(X)) -> from(activate(X)) r12: activate(n__s(X)) -> s(activate(X)) r13: activate(n__take(X1,X2)) -> take(activate(X1),activate(X2)) r14: activate(X) -> X The set of usable rules consists of r1, r4, r5, r8, r9, r10, r11, r12, r13, r14 Take the reduction pair: lexicographic combination of reduction pairs: 1. max/plus interpretations on natural numbers: sel#_A(x1,x2) = x1 + 5 s_A(x1) = x1 + 3 cons_A(x1,x2) = max{x1 + 2, x2 - 4} activate_A(x1) = x1 from_A(x1) = x1 + 2 n__from_A(x1) = x1 + 2 n__s_A(x1) = x1 + 3 take_A(x1,x2) = max{x1 + 6, x2} |0|_A = 0 nil_A = 1 n__take_A(x1,x2) = max{x1 + 6, x2} 2. max/plus interpretations on natural numbers: sel#_A(x1,x2) = 0 s_A(x1) = x1 + 1 cons_A(x1,x2) = 0 activate_A(x1) = x1 + 1 from_A(x1) = max{2, x1 + 1} n__from_A(x1) = x1 + 1 n__s_A(x1) = x1 + 1 take_A(x1,x2) = 2 |0|_A = 0 nil_A = 0 n__take_A(x1,x2) = 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: take#(s(N),cons(X,XS)) -> activate#(XS) p2: activate#(n__take(X1,X2)) -> activate#(X2) p3: activate#(n__take(X1,X2)) -> activate#(X1) p4: activate#(n__take(X1,X2)) -> take#(activate(X1),activate(X2)) p5: activate#(n__s(X)) -> activate#(X) p6: activate#(n__from(X)) -> activate#(X) and R consists of: r1: from(X) -> cons(X,n__from(n__s(X))) r2: head(cons(X,XS)) -> X r3: |2nd|(cons(X,XS)) -> head(activate(XS)) r4: take(|0|(),XS) -> nil() r5: take(s(N),cons(X,XS)) -> cons(X,n__take(N,activate(XS))) r6: sel(|0|(),cons(X,XS)) -> X r7: sel(s(N),cons(X,XS)) -> sel(N,activate(XS)) r8: from(X) -> n__from(X) r9: s(X) -> n__s(X) r10: take(X1,X2) -> n__take(X1,X2) r11: activate(n__from(X)) -> from(activate(X)) r12: activate(n__s(X)) -> s(activate(X)) r13: activate(n__take(X1,X2)) -> take(activate(X1),activate(X2)) r14: activate(X) -> X The set of usable rules consists of r1, r4, r5, r8, r9, r10, r11, r12, r13, r14 Take the reduction pair: lexicographic combination of reduction pairs: 1. max/plus interpretations on natural numbers: take#_A(x1,x2) = max{x1 - 1, x2 + 3} s_A(x1) = x1 + 2 cons_A(x1,x2) = max{x1 + 5, x2 - 2} activate#_A(x1) = x1 n__take_A(x1,x2) = max{x1 + 5, x2 + 6} activate_A(x1) = x1 n__s_A(x1) = x1 + 2 n__from_A(x1) = x1 + 5 from_A(x1) = x1 + 5 take_A(x1,x2) = max{x1 + 5, x2 + 6} |0|_A = 0 nil_A = 2 2. max/plus interpretations on natural numbers: take#_A(x1,x2) = 1 s_A(x1) = max{2, x1 + 1} cons_A(x1,x2) = 0 activate#_A(x1) = max{0, x1 - 1} n__take_A(x1,x2) = 3 activate_A(x1) = x1 + 2 n__s_A(x1) = max{2, x1 + 1} n__from_A(x1) = max{3, x1 + 1} from_A(x1) = max{4, x1 + 1} take_A(x1,x2) = 4 |0|_A = 0 nil_A = 5 The next rules are strictly ordered: p1, p2, p3, p4, p5, p6 We remove them from the problem. Then no dependency pair remains.