YES We show the termination of the TRS R: from(X) -> cons(X,n__from(n__s(X))) sel(|0|(),cons(X,Y)) -> X sel(s(X),cons(Y,Z)) -> sel(X,activate(Z)) from(X) -> n__from(X) s(X) -> n__s(X) activate(n__from(X)) -> from(activate(X)) activate(n__s(X)) -> s(activate(X)) activate(X) -> X -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: sel#(s(X),cons(Y,Z)) -> sel#(X,activate(Z)) p2: sel#(s(X),cons(Y,Z)) -> activate#(Z) p3: activate#(n__from(X)) -> from#(activate(X)) p4: activate#(n__from(X)) -> activate#(X) p5: activate#(n__s(X)) -> s#(activate(X)) p6: activate#(n__s(X)) -> activate#(X) and R consists of: r1: from(X) -> cons(X,n__from(n__s(X))) r2: sel(|0|(),cons(X,Y)) -> X r3: sel(s(X),cons(Y,Z)) -> sel(X,activate(Z)) r4: from(X) -> n__from(X) r5: s(X) -> n__s(X) r6: activate(n__from(X)) -> from(activate(X)) r7: activate(n__s(X)) -> s(activate(X)) r8: activate(X) -> X The estimated dependency graph contains the following SCCs: {p1} {p4, p6} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: sel#(s(X),cons(Y,Z)) -> sel#(X,activate(Z)) and R consists of: r1: from(X) -> cons(X,n__from(n__s(X))) r2: sel(|0|(),cons(X,Y)) -> X r3: sel(s(X),cons(Y,Z)) -> sel(X,activate(Z)) r4: from(X) -> n__from(X) r5: s(X) -> n__s(X) r6: activate(n__from(X)) -> from(activate(X)) r7: activate(n__s(X)) -> s(activate(X)) r8: activate(X) -> X The set of usable rules consists of r1, r4, r5, r6, r7, r8 Take the reduction pair: lexicographic combination of reduction pairs: 1. lexicographic path order with precedence: precedence: activate > from > s > n__s > n__from > cons > sel# argument filter: pi(sel#) = [1] pi(s) = [1] pi(cons) = [] pi(activate) = [1] pi(from) = [1] pi(n__from) = [1] pi(n__s) = [1] 2. matrix interpretations: carrier: N^4 order: lexicographic order interpretations: sel#_A(x1,x2) = ((1,0,0,0),(0,0,0,0),(1,0,0,0),(0,1,0,0)) x1 s_A(x1) = (1,1,2,2) cons_A(x1,x2) = (1,1,1,3) activate_A(x1) = ((1,0,0,0),(1,1,0,0),(0,0,0,0),(0,0,1,0)) x1 + (2,1,4,2) from_A(x1) = ((0,0,0,0),(1,0,0,0),(0,1,0,0),(0,0,0,0)) x1 + (4,2,2,2) n__from_A(x1) = ((0,0,0,0),(1,0,0,0),(0,1,0,0),(0,0,0,0)) x1 + (3,1,1,1) n__s_A(x1) = ((1,0,0,0),(1,1,0,0),(1,1,1,0),(0,0,0,0)) x1 + (2,2,1,1) 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: activate#(n__s(X)) -> activate#(X) p2: activate#(n__from(X)) -> activate#(X) and R consists of: r1: from(X) -> cons(X,n__from(n__s(X))) r2: sel(|0|(),cons(X,Y)) -> X r3: sel(s(X),cons(Y,Z)) -> sel(X,activate(Z)) r4: from(X) -> n__from(X) r5: s(X) -> n__s(X) r6: activate(n__from(X)) -> from(activate(X)) r7: activate(n__s(X)) -> s(activate(X)) r8: activate(X) -> X 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: n__from > n__s > activate# argument filter: pi(activate#) = 1 pi(n__s) = 1 pi(n__from) = 1 2. matrix interpretations: carrier: N^4 order: lexicographic order interpretations: activate#_A(x1) = ((1,0,0,0),(1,1,0,0),(1,1,1,0),(1,1,1,1)) x1 n__s_A(x1) = ((1,0,0,0),(1,1,0,0),(1,1,1,0),(0,0,1,1)) x1 n__from_A(x1) = ((1,0,0,0),(1,1,0,0),(1,1,1,0),(1,1,1,1)) x1 + (1,1,1,1) The next rules are strictly ordered: p2 r1, r2, r3, r4, r5, r6, r7, r8 We remove them from the problem. -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: activate#(n__s(X)) -> activate#(X) and R consists of: (no rules) The estimated dependency graph contains the following SCCs: {p1} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: activate#(n__s(X)) -> activate#(X) and R consists of: (no rules) 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: n__s > activate# argument filter: pi(activate#) = 1 pi(n__s) = [1] 2. matrix interpretations: carrier: N^4 order: lexicographic order interpretations: activate#_A(x1) = ((1,0,0,0),(0,1,0,0),(0,0,1,0),(1,1,1,1)) x1 n__s_A(x1) = ((1,0,0,0),(1,1,0,0),(1,1,1,0),(1,0,1,1)) x1 + (1,1,1,1) The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.