YES We show the termination of the TRS R: from(X) -> cons(X,n__from(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) take(X1,X2) -> n__take(X1,X2) activate(n__from(X)) -> from(X) activate(n__take(X1,X2)) -> take(X1,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#(X) p7: activate#(n__take(X1,X2)) -> take#(X1,X2) and R consists of: r1: from(X) -> cons(X,n__from(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: take(X1,X2) -> n__take(X1,X2) r10: activate(n__from(X)) -> from(X) r11: activate(n__take(X1,X2)) -> take(X1,X2) r12: activate(X) -> X The estimated dependency graph contains the following SCCs: {p4} {p3, p7} -- 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(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: take(X1,X2) -> n__take(X1,X2) r10: activate(n__from(X)) -> from(X) r11: activate(n__take(X1,X2)) -> take(X1,X2) r12: activate(X) -> X The set of usable rules consists of r1, r4, r5, r8, r9, r10, r11, r12 Take the reduction pair: lexicographic combination of reduction pairs: 1. matrix interpretations: carrier: N^3 order: lexicographic order interpretations: sel#_A(x1,x2) = ((1,0,0),(1,1,0),(0,0,1)) x1 + ((1,0,0),(1,1,0),(1,0,0)) x2 s_A(x1) = ((1,0,0),(1,1,0),(1,1,1)) x1 + (3,1,3) cons_A(x1,x2) = ((1,0,0),(0,0,0),(0,1,0)) x2 + (1,5,5) activate_A(x1) = ((1,0,0),(0,1,0),(1,1,1)) x1 + (3,1,0) from_A(x1) = (3,6,0) n__from_A(x1) = ((0,0,0),(1,0,0),(1,1,0)) x1 + (1,1,1) take_A(x1,x2) = x1 + ((0,0,0),(0,0,0),(1,0,0)) x2 + (3,3,4) |0|_A() = (1,1,1) nil_A() = (0,5,6) n__take_A(x1,x2) = ((1,0,0),(1,1,0),(1,1,1)) x1 + ((0,0,0),(1,0,0),(1,1,0)) x2 + (1,1,1) 2. lexicographic path order with precedence: precedence: s > nil > take > activate > from > n__from > cons > n__take > |0| > sel# argument filter: pi(sel#) = [1] pi(s) = 1 pi(cons) = [] pi(activate) = [] pi(from) = [] pi(n__from) = [] 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)) -> take#(X1,X2) and R consists of: r1: from(X) -> cons(X,n__from(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: take(X1,X2) -> n__take(X1,X2) r10: activate(n__from(X)) -> from(X) r11: activate(n__take(X1,X2)) -> take(X1,X2) r12: activate(X) -> X The set of usable rules consists of (no rules) Take the reduction pair: lexicographic combination of reduction pairs: 1. matrix interpretations: carrier: N^3 order: lexicographic order interpretations: take#_A(x1,x2) = ((0,0,0),(1,0,0),(0,1,0)) x1 + ((1,0,0),(0,0,0),(1,0,0)) x2 s_A(x1) = ((1,0,0),(1,1,0),(1,1,1)) x1 + (1,1,1) cons_A(x1,x2) = ((1,0,0),(0,1,0),(1,1,1)) x1 + ((1,0,0),(0,0,0),(1,1,0)) x2 + (1,1,1) activate#_A(x1) = ((1,0,0),(0,1,0),(1,1,1)) x1 + (0,2,3) n__take_A(x1,x2) = ((1,0,0),(1,1,0),(1,1,1)) x1 + ((1,0,0),(1,1,0),(1,1,1)) x2 + (1,1,1) 2. lexicographic path order with precedence: precedence: n__take > activate# > cons > s > take# argument filter: pi(take#) = [] pi(s) = [] pi(cons) = [] pi(activate#) = [1] pi(n__take) = [] The next rules are strictly ordered: p1, p2 We remove them from the problem. Then no dependency pair remains.