YES We show the termination of the TRS R: a__and(true(),X) -> mark(X) a__and(false(),Y) -> false() a__if(true(),X,Y) -> mark(X) a__if(false(),X,Y) -> mark(Y) a__add(|0|(),X) -> mark(X) a__add(s(X),Y) -> s(add(X,Y)) a__first(|0|(),X) -> nil() a__first(s(X),cons(Y,Z)) -> cons(Y,first(X,Z)) a__from(X) -> cons(X,from(s(X))) mark(and(X1,X2)) -> a__and(mark(X1),X2) mark(if(X1,X2,X3)) -> a__if(mark(X1),X2,X3) mark(add(X1,X2)) -> a__add(mark(X1),X2) mark(first(X1,X2)) -> a__first(mark(X1),mark(X2)) mark(from(X)) -> a__from(X) mark(true()) -> true() mark(false()) -> false() mark(|0|()) -> |0|() mark(s(X)) -> s(X) mark(nil()) -> nil() mark(cons(X1,X2)) -> cons(X1,X2) a__and(X1,X2) -> and(X1,X2) a__if(X1,X2,X3) -> if(X1,X2,X3) a__add(X1,X2) -> add(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__and#(true(),X) -> mark#(X) p2: a__if#(true(),X,Y) -> mark#(X) p3: a__if#(false(),X,Y) -> mark#(Y) p4: a__add#(|0|(),X) -> mark#(X) p5: mark#(and(X1,X2)) -> a__and#(mark(X1),X2) p6: mark#(and(X1,X2)) -> mark#(X1) p7: mark#(if(X1,X2,X3)) -> a__if#(mark(X1),X2,X3) p8: mark#(if(X1,X2,X3)) -> mark#(X1) p9: mark#(add(X1,X2)) -> a__add#(mark(X1),X2) p10: mark#(add(X1,X2)) -> mark#(X1) p11: mark#(first(X1,X2)) -> a__first#(mark(X1),mark(X2)) p12: mark#(first(X1,X2)) -> mark#(X1) p13: mark#(first(X1,X2)) -> mark#(X2) p14: mark#(from(X)) -> a__from#(X) and R consists of: r1: a__and(true(),X) -> mark(X) r2: a__and(false(),Y) -> false() r3: a__if(true(),X,Y) -> mark(X) r4: a__if(false(),X,Y) -> mark(Y) r5: a__add(|0|(),X) -> mark(X) r6: a__add(s(X),Y) -> s(add(X,Y)) r7: a__first(|0|(),X) -> nil() r8: a__first(s(X),cons(Y,Z)) -> cons(Y,first(X,Z)) r9: a__from(X) -> cons(X,from(s(X))) r10: mark(and(X1,X2)) -> a__and(mark(X1),X2) r11: mark(if(X1,X2,X3)) -> a__if(mark(X1),X2,X3) r12: mark(add(X1,X2)) -> a__add(mark(X1),X2) r13: mark(first(X1,X2)) -> a__first(mark(X1),mark(X2)) r14: mark(from(X)) -> a__from(X) r15: mark(true()) -> true() r16: mark(false()) -> false() r17: mark(|0|()) -> |0|() r18: mark(s(X)) -> s(X) r19: mark(nil()) -> nil() r20: mark(cons(X1,X2)) -> cons(X1,X2) r21: a__and(X1,X2) -> and(X1,X2) r22: a__if(X1,X2,X3) -> if(X1,X2,X3) r23: a__add(X1,X2) -> add(X1,X2) r24: a__first(X1,X2) -> first(X1,X2) r25: a__from(X) -> from(X) The estimated dependency graph contains the following SCCs: {p1, p2, p3, p4, p5, p6, p7, p8, p9, p10, p12, p13} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: a__and#(true(),X) -> mark#(X) p2: mark#(first(X1,X2)) -> mark#(X2) p3: mark#(first(X1,X2)) -> mark#(X1) p4: mark#(add(X1,X2)) -> mark#(X1) p5: mark#(add(X1,X2)) -> a__add#(mark(X1),X2) p6: a__add#(|0|(),X) -> mark#(X) p7: mark#(if(X1,X2,X3)) -> mark#(X1) p8: mark#(if(X1,X2,X3)) -> a__if#(mark(X1),X2,X3) p9: a__if#(false(),X,Y) -> mark#(Y) p10: mark#(and(X1,X2)) -> mark#(X1) p11: mark#(and(X1,X2)) -> a__and#(mark(X1),X2) p12: a__if#(true(),X,Y) -> mark#(X) and R consists of: r1: a__and(true(),X) -> mark(X) r2: a__and(false(),Y) -> false() r3: a__if(true(),X,Y) -> mark(X) r4: a__if(false(),X,Y) -> mark(Y) r5: a__add(|0|(),X) -> mark(X) r6: a__add(s(X),Y) -> s(add(X,Y)) r7: a__first(|0|(),X) -> nil() r8: a__first(s(X),cons(Y,Z)) -> cons(Y,first(X,Z)) r9: a__from(X) -> cons(X,from(s(X))) r10: mark(and(X1,X2)) -> a__and(mark(X1),X2) r11: mark(if(X1,X2,X3)) -> a__if(mark(X1),X2,X3) r12: mark(add(X1,X2)) -> a__add(mark(X1),X2) r13: mark(first(X1,X2)) -> a__first(mark(X1),mark(X2)) r14: mark(from(X)) -> a__from(X) r15: mark(true()) -> true() r16: mark(false()) -> false() r17: mark(|0|()) -> |0|() r18: mark(s(X)) -> s(X) r19: mark(nil()) -> nil() r20: mark(cons(X1,X2)) -> cons(X1,X2) r21: a__and(X1,X2) -> and(X1,X2) r22: a__if(X1,X2,X3) -> if(X1,X2,X3) r23: a__add(X1,X2) -> add(X1,X2) r24: a__first(X1,X2) -> first(X1,X2) r25: a__from(X) -> from(X) The set of usable rules consists of r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11, r12, r13, r14, r15, r16, r17, r18, r19, r20, r21, r22, r23, r24, r25 Take the reduction pair: lexicographic combination of reduction pairs: 1. weighted path order base order: max/plus interpretations on natural numbers: a__and#_A(x1,x2) = max{29, x1 + 15, x2 + 9} true_A = 13 mark#_A(x1) = x1 + 8 first_A(x1,x2) = max{33, x1 + 7, x2 + 20} add_A(x1,x2) = max{x1 + 3, x2 + 29} a__add#_A(x1,x2) = max{x1 + 3, x2 + 29} mark_A(x1) = max{12, x1} |0|_A = 13 if_A(x1,x2,x3) = max{x1 + 7, x2 + 20, x3 + 20} a__if#_A(x1,x2,x3) = max{x1 + 1, x2 + 28, x3 + 19} false_A = 13 and_A(x1,x2) = max{x1 + 15, x2 + 29} a__and_A(x1,x2) = max{x1 + 15, x2 + 29} a__if_A(x1,x2,x3) = max{x1 + 7, x2 + 20, x3 + 20} a__add_A(x1,x2) = max{x1 + 3, x2 + 29} s_A(x1) = max{28, x1 - 2} a__first_A(x1,x2) = max{33, x1 + 7, x2 + 20} nil_A = 1 cons_A(x1,x2) = x1 + 4 a__from_A(x1) = x1 + 4 from_A(x1) = x1 + 4 precedence: nil > mark = false = and = a__and = a__if = a__first = a__from = from > first > a__add = cons > a__and# = a__add# = s > true = mark# = add = |0| > a__if# > if partial status: pi(a__and#) = [1, 2] pi(true) = [] pi(mark#) = [1] pi(first) = [] pi(add) = [1, 2] pi(a__add#) = [2] pi(mark) = [1] pi(|0|) = [] pi(if) = [1] pi(a__if#) = [1, 2, 3] pi(false) = [] pi(and) = [1, 2] pi(a__and) = [1, 2] pi(a__if) = [1, 3] pi(a__add) = [] pi(s) = [] pi(a__first) = [] pi(nil) = [] pi(cons) = [1] pi(a__from) = [1] pi(from) = [] 2. weighted path order base order: max/plus interpretations on natural numbers: a__and#_A(x1,x2) = max{x1 - 7, x2} true_A = 31 mark#_A(x1) = max{23, x1} first_A(x1,x2) = 24 add_A(x1,x2) = max{x1 + 25, x2 + 25} a__add#_A(x1,x2) = x2 + 24 mark_A(x1) = 6 |0|_A = 7 if_A(x1,x2,x3) = x1 + 5 a__if#_A(x1,x2,x3) = max{x2 + 24, x3 + 25} false_A = 35 and_A(x1,x2) = max{24, x1 + 1, x2} a__and_A(x1,x2) = max{x1 + 28, x2 + 36} a__if_A(x1,x2,x3) = max{6, x1} a__add_A(x1,x2) = 50 s_A(x1) = 49 a__first_A(x1,x2) = 5 nil_A = 8 cons_A(x1,x2) = 6 a__from_A(x1) = 6 from_A(x1) = 17 precedence: true > and > a__and# > mark# = mark = |0| = a__if# = a__add = nil > first = add = a__add# = if = a__from = from > false = a__and = a__if = s = a__first = cons partial status: pi(a__and#) = [2] pi(true) = [] pi(mark#) = [1] pi(first) = [] pi(add) = [] pi(a__add#) = [2] pi(mark) = [] pi(|0|) = [] pi(if) = [] pi(a__if#) = [2, 3] pi(false) = [] pi(and) = [1, 2] pi(a__and) = [] pi(a__if) = [] pi(a__add) = [] pi(s) = [] pi(a__first) = [] pi(nil) = [] pi(cons) = [] pi(a__from) = [] pi(from) = [] The next rules are strictly ordered: p1, p2, p3, p4, p5, p6, p7, p8, p9, p10, p11, p12 We remove them from the problem. Then no dependency pair remains.