YES We show the termination of the TRS R: lt(|0|(),s(x)) -> true() lt(x,|0|()) -> false() lt(s(x),s(y)) -> lt(x,y) logarithm(x) -> ifa(lt(|0|(),x),x) ifa(true(),x) -> help(x,|1|()) ifa(false(),x) -> logZeroError() help(x,y) -> ifb(lt(y,x),x,y) ifb(true(),x,y) -> help(half(x),s(y)) ifb(false(),x,y) -> y half(|0|()) -> |0|() half(s(|0|())) -> |0|() half(s(s(x))) -> s(half(x)) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: lt#(s(x),s(y)) -> lt#(x,y) p2: logarithm#(x) -> ifa#(lt(|0|(),x),x) p3: logarithm#(x) -> lt#(|0|(),x) p4: ifa#(true(),x) -> help#(x,|1|()) p5: help#(x,y) -> ifb#(lt(y,x),x,y) p6: help#(x,y) -> lt#(y,x) p7: ifb#(true(),x,y) -> help#(half(x),s(y)) p8: ifb#(true(),x,y) -> half#(x) p9: half#(s(s(x))) -> half#(x) and R consists of: r1: lt(|0|(),s(x)) -> true() r2: lt(x,|0|()) -> false() r3: lt(s(x),s(y)) -> lt(x,y) r4: logarithm(x) -> ifa(lt(|0|(),x),x) r5: ifa(true(),x) -> help(x,|1|()) r6: ifa(false(),x) -> logZeroError() r7: help(x,y) -> ifb(lt(y,x),x,y) r8: ifb(true(),x,y) -> help(half(x),s(y)) r9: ifb(false(),x,y) -> y r10: half(|0|()) -> |0|() r11: half(s(|0|())) -> |0|() r12: half(s(s(x))) -> s(half(x)) The estimated dependency graph contains the following SCCs: {p5, p7} {p1} {p9} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: ifb#(true(),x,y) -> help#(half(x),s(y)) p2: help#(x,y) -> ifb#(lt(y,x),x,y) and R consists of: r1: lt(|0|(),s(x)) -> true() r2: lt(x,|0|()) -> false() r3: lt(s(x),s(y)) -> lt(x,y) r4: logarithm(x) -> ifa(lt(|0|(),x),x) r5: ifa(true(),x) -> help(x,|1|()) r6: ifa(false(),x) -> logZeroError() r7: help(x,y) -> ifb(lt(y,x),x,y) r8: ifb(true(),x,y) -> help(half(x),s(y)) r9: ifb(false(),x,y) -> y r10: half(|0|()) -> |0|() r11: half(s(|0|())) -> |0|() r12: half(s(s(x))) -> s(half(x)) The set of usable rules consists of r1, r2, r3, r10, r11, r12 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!): matrix interpretation with standard point-wise order: carrier: N^1 order: standard order interpretations: ifb#_A(x1,x2,x3) = 0 true_A() = 1 help#_A(x1,x2) = 0 half_A(x1) = x1 + 1 s_A(x1) = x1 + 2 lt_A(x1,x2) = x1 + x2 + 1 |0|_A() = 1 false_A() = 2 ifb#!_A(x1,x2,x3) = 0 true!_A() = 2 help#!_A(x1,x2) = 0 half!_A(x1) = 5 s!_A(x1) = 4 lt!_A(x1,x2) = x1 + x2 + 1 |0|!_A() = 3 false!_A() = 2 2. marked-algebra reduction triple (>=A, >=A!, >A!): max/plus interpretation on natural numbers: ifb#_A(x1,x2,x3) = 1 true_A = 55 help#_A(x1,x2) = 1 half_A(x1) = max{17, x1 - 15} s_A(x1) = max{32, x1 + 23} lt_A(x1,x2) = x2 + 31 |0|_A = 17 false_A = 2 ifb#!_A(x1,x2,x3) = max{x1 - 1, x2 + 35} true!_A = 69 help#!_A(x1,x2) = x1 + 36 half!_A(x1) = max{32, x1} s!_A(x1) = x1 + 73 lt!_A(x1,x2) = max{72, x1 - 21, x2 + 36} |0|!_A = 91 false!_A = 72 partial status: pi(ifb#) = [] pi(true) = [] pi(help#) = [] pi(half) = [] pi(s) = [1] pi(lt) = [1, 2] pi(|0|) = [] pi(false) = [] The following rules are removed: p1, p2 Then no dependency pair remains. -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: lt#(s(x),s(y)) -> lt#(x,y) and R consists of: r1: lt(|0|(),s(x)) -> true() r2: lt(x,|0|()) -> false() r3: lt(s(x),s(y)) -> lt(x,y) r4: logarithm(x) -> ifa(lt(|0|(),x),x) r5: ifa(true(),x) -> help(x,|1|()) r6: ifa(false(),x) -> logZeroError() r7: help(x,y) -> ifb(lt(y,x),x,y) r8: ifb(true(),x,y) -> help(half(x),s(y)) r9: ifb(false(),x,y) -> y r10: half(|0|()) -> |0|() r11: half(s(|0|())) -> |0|() r12: half(s(s(x))) -> s(half(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!): matrix interpretation with standard point-wise order: carrier: N^1 order: standard order interpretations: lt#_A(x1,x2) = x1 + x2 s_A(x1) = x1 + 2 lt#!_A(x1,x2) = x1 + x2 s!_A(x1) = 5 2. marked-algebra reduction triple (>=A, >=A!, >A!): max/plus interpretation on natural numbers: lt#_A(x1,x2) = 0 s_A(x1) = max{4, x1 - 12} lt#!_A(x1,x2) = max{12, x2 - 5} s!_A(x1) = x1 + 11 partial status: pi(lt#) = [] 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: half#(s(s(x))) -> half#(x) and R consists of: r1: lt(|0|(),s(x)) -> true() r2: lt(x,|0|()) -> false() r3: lt(s(x),s(y)) -> lt(x,y) r4: logarithm(x) -> ifa(lt(|0|(),x),x) r5: ifa(true(),x) -> help(x,|1|()) r6: ifa(false(),x) -> logZeroError() r7: help(x,y) -> ifb(lt(y,x),x,y) r8: ifb(true(),x,y) -> help(half(x),s(y)) r9: ifb(false(),x,y) -> y r10: half(|0|()) -> |0|() r11: half(s(|0|())) -> |0|() r12: half(s(s(x))) -> s(half(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!): matrix interpretation with standard point-wise order: carrier: N^1 order: standard order interpretations: half#_A(x1) = 0 s_A(x1) = 2 half#!_A(x1) = 0 s!_A(x1) = x1 + 7 2. marked-algebra reduction triple (>=A, >=A!, >A!): max/plus interpretation on natural numbers: half#_A(x1) = 0 s_A(x1) = max{2, x1 - 12} half#!_A(x1) = max{1, x1 - 1} s!_A(x1) = 0 partial status: pi(half#) = [1] pi(s) = [1] The following rules are removed: p1 Then no dependency pair remains.