YES We show the termination of the TRS R: cond1(true(),x,y) -> cond2(gr(y,|0|()),x,y) cond2(true(),x,y) -> cond2(gr(y,|0|()),x,p(y)) cond2(false(),x,y) -> cond1(gr(x,|0|()),p(x),y) gr(|0|(),x) -> false() gr(s(x),|0|()) -> true() gr(s(x),s(y)) -> gr(x,y) p(|0|()) -> |0|() p(s(x)) -> x -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: cond1#(true(),x,y) -> cond2#(gr(y,|0|()),x,y) p2: cond1#(true(),x,y) -> gr#(y,|0|()) p3: cond2#(true(),x,y) -> cond2#(gr(y,|0|()),x,p(y)) p4: cond2#(true(),x,y) -> gr#(y,|0|()) p5: cond2#(true(),x,y) -> p#(y) p6: cond2#(false(),x,y) -> cond1#(gr(x,|0|()),p(x),y) p7: cond2#(false(),x,y) -> gr#(x,|0|()) p8: cond2#(false(),x,y) -> p#(x) p9: gr#(s(x),s(y)) -> gr#(x,y) and R consists of: r1: cond1(true(),x,y) -> cond2(gr(y,|0|()),x,y) r2: cond2(true(),x,y) -> cond2(gr(y,|0|()),x,p(y)) r3: cond2(false(),x,y) -> cond1(gr(x,|0|()),p(x),y) r4: gr(|0|(),x) -> false() r5: gr(s(x),|0|()) -> true() r6: gr(s(x),s(y)) -> gr(x,y) r7: p(|0|()) -> |0|() r8: p(s(x)) -> x The estimated dependency graph contains the following SCCs: {p1, p3, p6} {p9} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: cond1#(true(),x,y) -> cond2#(gr(y,|0|()),x,y) p2: cond2#(false(),x,y) -> cond1#(gr(x,|0|()),p(x),y) p3: cond2#(true(),x,y) -> cond2#(gr(y,|0|()),x,p(y)) and R consists of: r1: cond1(true(),x,y) -> cond2(gr(y,|0|()),x,y) r2: cond2(true(),x,y) -> cond2(gr(y,|0|()),x,p(y)) r3: cond2(false(),x,y) -> cond1(gr(x,|0|()),p(x),y) r4: gr(|0|(),x) -> false() r5: gr(s(x),|0|()) -> true() r6: gr(s(x),s(y)) -> gr(x,y) r7: p(|0|()) -> |0|() r8: p(s(x)) -> x The set of usable rules consists of r4, r5, r7, r8 Take the reduction pair: generalized weighted path order (>=MG, >G) base order 1: trivial reduction triple (T x T, T x T, Φ) base order 2: lexicographic combination of reduction triples: 1. marked-algebra reduction triple (>=A, >=A!, >A!): max/plus interpretation on natural numbers: cond1#_A(x1,x2,x3) = max{17, x2, x3 - 20} true_A = 5 cond2#_A(x1,x2,x3) = max{17, x1 - 8, x2 - 22, x3 - 20} gr_A(x1,x2) = max{0, x1 - 16} |0|_A = 17 false_A = 1 p_A(x1) = max{17, x1 - 22} s_A(x1) = x1 + 57 cond1#!_A(x1,x2,x3) = max{x1 + 35, x2 + 21} true!_A = 40 cond2#!_A(x1,x2,x3) = max{39, x2 + 20} gr!_A(x1,x2) = max{2, x1 - 16} |0|!_A = 4 false!_A = 3 p!_A(x1) = 5 s!_A(x1) = max{0, x1 - 15} 2. marked-algebra reduction triple (>=A, >=A!, >A!): max/plus interpretation on natural numbers: cond1#_A(x1,x2,x3) = max{0, x1 - 13, x2 - 21, x3 - 1} true_A = 0 cond2#_A(x1,x2,x3) = max{0, x1 - 2, x2 - 22, x3 - 1} gr_A(x1,x2) = max{0, x1 - 9, x2 - 18} |0|_A = 0 false_A = 0 p_A(x1) = max{0, x1 - 6} s_A(x1) = x1 + 6 cond1#!_A(x1,x2,x3) = max{x1 + 8, x2 - 1} true!_A = 5 cond2#!_A(x1,x2,x3) = max{x1 + 8, x2 + 15, x3 + 7} gr!_A(x1,x2) = max{15, x2 + 9} |0|!_A = 17 false!_A = 15 p!_A(x1) = max{18, x1 + 16} s!_A(x1) = x1 + 4 partial status: pi(cond1#) = [] pi(true) = [] pi(cond2#) = [] pi(gr) = [1, 2] pi(|0|) = [] pi(false) = [] pi(p) = [1] pi(s) = [1] The following rules are removed: p1, p2 -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: cond2#(true(),x,y) -> cond2#(gr(y,|0|()),x,p(y)) and R consists of: r1: cond1(true(),x,y) -> cond2(gr(y,|0|()),x,y) r2: cond2(true(),x,y) -> cond2(gr(y,|0|()),x,p(y)) r3: cond2(false(),x,y) -> cond1(gr(x,|0|()),p(x),y) r4: gr(|0|(),x) -> false() r5: gr(s(x),|0|()) -> true() r6: gr(s(x),s(y)) -> gr(x,y) r7: p(|0|()) -> |0|() r8: p(s(x)) -> x The estimated dependency graph contains the following SCCs: {p1} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: cond2#(true(),x,y) -> cond2#(gr(y,|0|()),x,p(y)) and R consists of: r1: cond1(true(),x,y) -> cond2(gr(y,|0|()),x,y) r2: cond2(true(),x,y) -> cond2(gr(y,|0|()),x,p(y)) r3: cond2(false(),x,y) -> cond1(gr(x,|0|()),p(x),y) r4: gr(|0|(),x) -> false() r5: gr(s(x),|0|()) -> true() r6: gr(s(x),s(y)) -> gr(x,y) r7: p(|0|()) -> |0|() r8: p(s(x)) -> x The set of usable rules consists of r4, r5, r7, r8 Take the reduction pair: generalized weighted path order (>=MG, >G) base order 1: trivial reduction triple (T x T, T x T, Φ) base order 2: lexicographic combination of reduction triples: 1. marked-algebra reduction triple (>=A, >=A!, >A!): max/plus interpretation on natural numbers: cond2#_A(x1,x2,x3) = max{x1 - 3, x2 - 1, x3 + 2} true_A = 1 gr_A(x1,x2) = 4 |0|_A = 0 p_A(x1) = x1 false_A = 2 s_A(x1) = x1 cond2#!_A(x1,x2,x3) = x2 + 2 true!_A = 4 gr!_A(x1,x2) = max{x1 + 12, x2 + 5} |0|!_A = 8 p!_A(x1) = max{9, x1 - 6} false!_A = 7 s!_A(x1) = max{5, x1 - 1} 2. marked-algebra reduction triple (>=A, >=A!, >A!): max/plus interpretation on natural numbers: cond2#_A(x1,x2,x3) = max{0, x2 - 20, x3 - 33} true_A = 22 gr_A(x1,x2) = max{5, x1 - 10} |0|_A = 14 p_A(x1) = max{14, x1 - 11} false_A = 5 s_A(x1) = max{35, x1 + 11} cond2#!_A(x1,x2,x3) = max{x1 + 1, x3 + 8} true!_A = 28 gr!_A(x1,x2) = max{26, x1 - 8, x2 + 15} |0|!_A = 31 p!_A(x1) = max{25, x1 + 9} false!_A = 30 s!_A(x1) = x1 + 29 partial status: pi(cond2#) = [] pi(true) = [] pi(gr) = [1, 2] pi(|0|) = [] pi(p) = [1] pi(false) = [] pi(s) = [1] The following rules are removed: p1 Then no dependency pair remains. -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: gr#(s(x),s(y)) -> gr#(x,y) and R consists of: r1: cond1(true(),x,y) -> cond2(gr(y,|0|()),x,y) r2: cond2(true(),x,y) -> cond2(gr(y,|0|()),x,p(y)) r3: cond2(false(),x,y) -> cond1(gr(x,|0|()),p(x),y) r4: gr(|0|(),x) -> false() r5: gr(s(x),|0|()) -> true() r6: gr(s(x),s(y)) -> gr(x,y) r7: p(|0|()) -> |0|() r8: p(s(x)) -> x The set of usable rules consists of (no rules) Take the reduction pair: generalized weighted path order (>=MG, >G) base order 1: trivial reduction triple (T x T, T x T, Φ) base order 2: lexicographic combination of reduction triples: 1. marked-algebra reduction triple (>=A, >=A!, >A!): max/plus interpretation on natural numbers: gr#_A(x1,x2) = 0 s_A(x1) = max{0, x1 - 2} gr#!_A(x1,x2) = max{0, x1 - 17} s!_A(x1) = max{2, x1 - 16} 2. marked-algebra reduction triple (>=A, >=A!, >A!): max/plus interpretation on natural numbers: gr#_A(x1,x2) = max{x1, x2} s_A(x1) = x1 gr#!_A(x1,x2) = max{3, x1 - 1, x2 - 1} s!_A(x1) = max{2, x1 - 26} partial status: pi(gr#) = [1] pi(s) = [1] The following rules are removed: p1 Then no dependency pair remains.