YES We show the termination of the TRS R: a__first(|0|(),X) -> nil() a__first(s(X),cons(Y,Z)) -> cons(mark(Y),first(X,Z)) a__from(X) -> cons(mark(X),from(s(X))) mark(first(X1,X2)) -> a__first(mark(X1),mark(X2)) mark(from(X)) -> a__from(mark(X)) mark(|0|()) -> |0|() mark(nil()) -> nil() mark(s(X)) -> s(mark(X)) mark(cons(X1,X2)) -> cons(mark(X1),X2) a__first(X1,X2) -> first(X1,X2) a__from(X) -> from(X) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: a__first#(s(X),cons(Y,Z)) -> mark#(Y) p2: a__from#(X) -> mark#(X) p3: mark#(first(X1,X2)) -> a__first#(mark(X1),mark(X2)) p4: mark#(first(X1,X2)) -> mark#(X1) p5: mark#(first(X1,X2)) -> mark#(X2) p6: mark#(from(X)) -> a__from#(mark(X)) p7: mark#(from(X)) -> mark#(X) p8: mark#(s(X)) -> mark#(X) p9: mark#(cons(X1,X2)) -> mark#(X1) and R consists of: r1: a__first(|0|(),X) -> nil() r2: a__first(s(X),cons(Y,Z)) -> cons(mark(Y),first(X,Z)) r3: a__from(X) -> cons(mark(X),from(s(X))) r4: mark(first(X1,X2)) -> a__first(mark(X1),mark(X2)) r5: mark(from(X)) -> a__from(mark(X)) r6: mark(|0|()) -> |0|() r7: mark(nil()) -> nil() r8: mark(s(X)) -> s(mark(X)) r9: mark(cons(X1,X2)) -> cons(mark(X1),X2) r10: a__first(X1,X2) -> first(X1,X2) r11: a__from(X) -> from(X) The estimated dependency graph contains the following SCCs: {p1, p2, p3, p4, p5, p6, p7, p8, p9} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: a__first#(s(X),cons(Y,Z)) -> mark#(Y) p2: mark#(cons(X1,X2)) -> mark#(X1) p3: mark#(s(X)) -> mark#(X) p4: mark#(from(X)) -> mark#(X) p5: mark#(from(X)) -> a__from#(mark(X)) p6: a__from#(X) -> mark#(X) p7: mark#(first(X1,X2)) -> mark#(X2) p8: mark#(first(X1,X2)) -> mark#(X1) p9: mark#(first(X1,X2)) -> a__first#(mark(X1),mark(X2)) and R consists of: r1: a__first(|0|(),X) -> nil() r2: a__first(s(X),cons(Y,Z)) -> cons(mark(Y),first(X,Z)) r3: a__from(X) -> cons(mark(X),from(s(X))) r4: mark(first(X1,X2)) -> a__first(mark(X1),mark(X2)) r5: mark(from(X)) -> a__from(mark(X)) r6: mark(|0|()) -> |0|() r7: mark(nil()) -> nil() r8: mark(s(X)) -> s(mark(X)) r9: mark(cons(X1,X2)) -> cons(mark(X1),X2) r10: a__first(X1,X2) -> first(X1,X2) r11: a__from(X) -> from(X) The set of usable rules consists of r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11 Take the reduction pair: lexicographic combination of reduction pairs: 1. matrix interpretations: carrier: N^3 order: lexicographic order interpretations: a__first#_A(x1,x2) = ((1,0,0),(0,0,0),(1,1,0)) x1 + ((1,0,0),(0,1,0),(0,1,1)) x2 s_A(x1) = x1 + (1,1,1) cons_A(x1,x2) = x1 + ((0,0,0),(0,0,0),(1,0,0)) x2 + (1,5,1) mark#_A(x1) = x1 + (1,2,7) from_A(x1) = ((1,0,0),(1,0,0),(1,0,0)) x1 + (2,4,0) a__from#_A(x1) = ((1,0,0),(1,0,0),(1,1,0)) x1 + (2,3,8) mark_A(x1) = ((1,0,0),(1,1,0),(1,0,0)) x1 + (0,1,4) first_A(x1,x2) = x1 + x2 + (0,1,1) a__first_A(x1,x2) = x1 + x2 + (0,1,2) |0|_A() = (2,1,0) nil_A() = (1,0,0) a__from_A(x1) = ((1,0,0),(1,0,0),(1,0,0)) x1 + (2,6,5) 2. lexicographic path order with precedence: precedence: mark > a__from > a__from# > s > a__first# > a__first > cons > mark# > |0| > first > nil > from argument filter: pi(a__first#) = [] pi(s) = [] pi(cons) = [] pi(mark#) = [] pi(from) = [] pi(a__from#) = [] pi(mark) = [] pi(first) = [] pi(a__first) = [] pi(|0|) = [] pi(nil) = [] pi(a__from) = [] The next rules are strictly ordered: p1, p2, p3, p4, p5, p6, p9 We remove them from the problem. -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: mark#(first(X1,X2)) -> mark#(X2) p2: mark#(first(X1,X2)) -> mark#(X1) and R consists of: r1: a__first(|0|(),X) -> nil() r2: a__first(s(X),cons(Y,Z)) -> cons(mark(Y),first(X,Z)) r3: a__from(X) -> cons(mark(X),from(s(X))) r4: mark(first(X1,X2)) -> a__first(mark(X1),mark(X2)) r5: mark(from(X)) -> a__from(mark(X)) r6: mark(|0|()) -> |0|() r7: mark(nil()) -> nil() r8: mark(s(X)) -> s(mark(X)) r9: mark(cons(X1,X2)) -> cons(mark(X1),X2) r10: a__first(X1,X2) -> first(X1,X2) r11: a__from(X) -> from(X) The estimated dependency graph contains the following SCCs: {p1, p2} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: mark#(first(X1,X2)) -> mark#(X2) p2: mark#(first(X1,X2)) -> mark#(X1) and R consists of: r1: a__first(|0|(),X) -> nil() r2: a__first(s(X),cons(Y,Z)) -> cons(mark(Y),first(X,Z)) r3: a__from(X) -> cons(mark(X),from(s(X))) r4: mark(first(X1,X2)) -> a__first(mark(X1),mark(X2)) r5: mark(from(X)) -> a__from(mark(X)) r6: mark(|0|()) -> |0|() r7: mark(nil()) -> nil() r8: mark(s(X)) -> s(mark(X)) r9: mark(cons(X1,X2)) -> cons(mark(X1),X2) r10: a__first(X1,X2) -> first(X1,X2) r11: a__from(X) -> from(X) The set of usable rules consists of (no rules) Take the monotone reduction pair: lexicographic combination of reduction pairs: 1. matrix interpretations: carrier: N^3 order: lexicographic order interpretations: mark#_A(x1) = ((1,0,0),(1,1,0),(1,1,1)) x1 first_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: first > mark# argument filter: pi(mark#) = [1] pi(first) = [1, 2] The next rules are strictly ordered: p1, p2 r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11 We remove them from the problem. Then no dependency pair remains.