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. matrix interpretations: carrier: N^2 order: lexicographic order interpretations: sel#_A(x1,x2) = x1 s_A(x1) = x1 + (0,1) cons_A(x1,x2) = ((0,0),(1,0)) x2 + (1,1) activate_A(x1) = ((1,0),(1,1)) x1 + (2,1) from_A(x1) = (2,3) n__from_A(x1) = (1,2) n__s_A(x1) = x1 + (0,1) take_A(x1,x2) = x1 + (2,3) |0|_A() = (1,1) nil_A() = (0,0) n__take_A(x1,x2) = x1 + (2,2) 2. lexicographic path order with precedence: precedence: activate > n__take > |0| > take > nil > s > n__s > from > n__from > sel# > cons argument filter: pi(sel#) = 1 pi(s) = [1] pi(cons) = [] pi(activate) = [1] pi(from) = [] pi(n__from) = [] pi(n__s) = [1] pi(take) = 1 pi(|0|) = [] pi(nil) = [] pi(n__take) = 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. matrix interpretations: carrier: N^2 order: lexicographic order interpretations: take#_A(x1,x2) = ((0,0),(1,0)) x1 + x2 + (3,1) s_A(x1) = x1 + (0,1) cons_A(x1,x2) = ((0,0),(1,0)) x1 + x2 activate#_A(x1) = x1 n__take_A(x1,x2) = ((1,0),(1,1)) x1 + ((1,0),(1,1)) x2 + (3,2) activate_A(x1) = ((1,0),(1,1)) x1 + (0,1) n__s_A(x1) = x1 + (0,1) n__from_A(x1) = ((1,0),(1,1)) x1 + (2,1) from_A(x1) = ((1,0),(1,1)) x1 + (2,2) take_A(x1,x2) = ((1,0),(1,1)) x1 + ((1,0),(1,1)) x2 + (3,3) |0|_A() = (0,0) nil_A() = (0,4) 2. lexicographic path order with precedence: precedence: |0| > s > activate > take > nil > from > activate# > n__from > n__s > cons > n__take > take# argument filter: pi(take#) = [] pi(s) = 1 pi(cons) = [] pi(activate#) = [] pi(n__take) = [] pi(activate) = [] pi(n__s) = 1 pi(n__from) = [] pi(from) = [] pi(take) = [] pi(|0|) = [] pi(nil) = [] The next rules are strictly ordered: p1, p2, p3, p4, p5, p6 We remove them from the problem. Then no dependency pair remains.