YES We show the termination of the TRS R: half(|0|()) -> |0|() half(s(|0|())) -> |0|() half(s(s(x))) -> s(half(x)) inc(|0|()) -> |0|() inc(s(x)) -> s(inc(x)) zero(|0|()) -> true() zero(s(x)) -> false() p(|0|()) -> |0|() p(s(x)) -> x bits(x) -> bitIter(x,|0|()) bitIter(x,y) -> if(zero(x),x,inc(y)) if(true(),x,y) -> p(y) if(false(),x,y) -> bitIter(half(x),y) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: half#(s(s(x))) -> half#(x) p2: inc#(s(x)) -> inc#(x) p3: bits#(x) -> bitIter#(x,|0|()) p4: bitIter#(x,y) -> if#(zero(x),x,inc(y)) p5: bitIter#(x,y) -> zero#(x) p6: bitIter#(x,y) -> inc#(y) p7: if#(true(),x,y) -> p#(y) p8: if#(false(),x,y) -> bitIter#(half(x),y) p9: if#(false(),x,y) -> half#(x) and R consists of: r1: half(|0|()) -> |0|() r2: half(s(|0|())) -> |0|() r3: half(s(s(x))) -> s(half(x)) r4: inc(|0|()) -> |0|() r5: inc(s(x)) -> s(inc(x)) r6: zero(|0|()) -> true() r7: zero(s(x)) -> false() r8: p(|0|()) -> |0|() r9: p(s(x)) -> x r10: bits(x) -> bitIter(x,|0|()) r11: bitIter(x,y) -> if(zero(x),x,inc(y)) r12: if(true(),x,y) -> p(y) r13: if(false(),x,y) -> bitIter(half(x),y) The estimated dependency graph contains the following SCCs: {p4, p8} {p1} {p2} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: bitIter#(x,y) -> if#(zero(x),x,inc(y)) p2: if#(false(),x,y) -> bitIter#(half(x),y) and R consists of: r1: half(|0|()) -> |0|() r2: half(s(|0|())) -> |0|() r3: half(s(s(x))) -> s(half(x)) r4: inc(|0|()) -> |0|() r5: inc(s(x)) -> s(inc(x)) r6: zero(|0|()) -> true() r7: zero(s(x)) -> false() r8: p(|0|()) -> |0|() r9: p(s(x)) -> x r10: bits(x) -> bitIter(x,|0|()) r11: bitIter(x,y) -> if(zero(x),x,inc(y)) r12: if(true(),x,y) -> p(y) r13: if(false(),x,y) -> bitIter(half(x),y) The set of usable rules consists of r1, r2, r3, r4, r5, r6, r7 Take the reduction pair: max/plus interpretations on natural numbers: bitIter#_A(x1,x2) = x1 + 3 if#_A(x1,x2,x3) = max{x1 - 4, x2 + 2} zero_A(x1) = max{6, x1} inc_A(x1) = x1 + 7 false_A = 13 half_A(x1) = max{5, x1 - 2} |0|_A = 5 s_A(x1) = max{20, x1 + 13} true_A = 6 The next rules are strictly ordered: p1, p2 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: half#(s(s(x))) -> half#(x) and R consists of: r1: half(|0|()) -> |0|() r2: half(s(|0|())) -> |0|() r3: half(s(s(x))) -> s(half(x)) r4: inc(|0|()) -> |0|() r5: inc(s(x)) -> s(inc(x)) r6: zero(|0|()) -> true() r7: zero(s(x)) -> false() r8: p(|0|()) -> |0|() r9: p(s(x)) -> x r10: bits(x) -> bitIter(x,|0|()) r11: bitIter(x,y) -> if(zero(x),x,inc(y)) r12: if(true(),x,y) -> p(y) r13: if(false(),x,y) -> bitIter(half(x),y) The set of usable rules consists of (no rules) Take the monotone reduction pair: max/plus interpretations on natural numbers: half#_A(x1) = x1 s_A(x1) = x1 + 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: inc#(s(x)) -> inc#(x) and R consists of: r1: half(|0|()) -> |0|() r2: half(s(|0|())) -> |0|() r3: half(s(s(x))) -> s(half(x)) r4: inc(|0|()) -> |0|() r5: inc(s(x)) -> s(inc(x)) r6: zero(|0|()) -> true() r7: zero(s(x)) -> false() r8: p(|0|()) -> |0|() r9: p(s(x)) -> x r10: bits(x) -> bitIter(x,|0|()) r11: bitIter(x,y) -> if(zero(x),x,inc(y)) r12: if(true(),x,y) -> p(y) r13: if(false(),x,y) -> bitIter(half(x),y) The set of usable rules consists of (no rules) Take the monotone reduction pair: max/plus interpretations on natural numbers: inc#_A(x1) = x1 s_A(x1) = x1 + 1 The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.