YES We show the termination of the TRS R: cond(true(),x,y) -> cond(and(gr(x,|0|()),gr(y,|0|())),p(x),p(y)) and(true(),true()) -> true() and(x,false()) -> false() and(false(),x) -> false() gr(|0|(),|0|()) -> false() 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: cond#(true(),x,y) -> cond#(and(gr(x,|0|()),gr(y,|0|())),p(x),p(y)) p2: cond#(true(),x,y) -> and#(gr(x,|0|()),gr(y,|0|())) p3: cond#(true(),x,y) -> gr#(x,|0|()) p4: cond#(true(),x,y) -> gr#(y,|0|()) p5: cond#(true(),x,y) -> p#(x) p6: cond#(true(),x,y) -> p#(y) p7: gr#(s(x),s(y)) -> gr#(x,y) and R consists of: r1: cond(true(),x,y) -> cond(and(gr(x,|0|()),gr(y,|0|())),p(x),p(y)) r2: and(true(),true()) -> true() r3: and(x,false()) -> false() r4: and(false(),x) -> false() r5: gr(|0|(),|0|()) -> false() r6: gr(|0|(),x) -> false() r7: gr(s(x),|0|()) -> true() r8: gr(s(x),s(y)) -> gr(x,y) r9: p(|0|()) -> |0|() r10: p(s(x)) -> x The estimated dependency graph contains the following SCCs: {p1} {p7} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: cond#(true(),x,y) -> cond#(and(gr(x,|0|()),gr(y,|0|())),p(x),p(y)) and R consists of: r1: cond(true(),x,y) -> cond(and(gr(x,|0|()),gr(y,|0|())),p(x),p(y)) r2: and(true(),true()) -> true() r3: and(x,false()) -> false() r4: and(false(),x) -> false() r5: gr(|0|(),|0|()) -> false() r6: gr(|0|(),x) -> false() r7: gr(s(x),|0|()) -> true() r8: gr(s(x),s(y)) -> gr(x,y) r9: p(|0|()) -> |0|() r10: p(s(x)) -> x The set of usable rules consists of r2, r3, r4, r5, r6, r7, r9, r10 Take the reduction pair: lexicographic combination of reduction pairs: 1. weighted path order base order: max/plus interpretations on natural numbers: cond#_A(x1,x2,x3) = max{x1, x2 + 8, x3 + 13} true_A = 18 and_A(x1,x2) = max{x1 + 1, x2 + 3} gr_A(x1,x2) = max{x1 + 6, x2 + 1} |0|_A = 0 p_A(x1) = max{4, x1 - 1} false_A = 0 s_A(x1) = x1 + 19 precedence: cond# = true = and = gr = p = s > |0| = false partial status: pi(cond#) = [1, 2, 3] pi(true) = [] pi(and) = [1, 2] pi(gr) = [1, 2] pi(|0|) = [] pi(p) = [] pi(false) = [] pi(s) = [1] 2. weighted path order base order: max/plus interpretations on natural numbers: cond#_A(x1,x2,x3) = max{x1 - 2, x2 + 2, x3 + 2} true_A = 4 and_A(x1,x2) = max{x1 + 7, x2 + 7} gr_A(x1,x2) = max{x1 + 6, x2 + 7} |0|_A = 1 p_A(x1) = 3 false_A = 6 s_A(x1) = x1 + 5 precedence: cond# = true = and = gr = |0| = p = false = s partial status: pi(cond#) = [3] pi(true) = [] pi(and) = [1, 2] pi(gr) = [1, 2] pi(|0|) = [] pi(p) = [] pi(false) = [] pi(s) = [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: gr#(s(x),s(y)) -> gr#(x,y) and R consists of: r1: cond(true(),x,y) -> cond(and(gr(x,|0|()),gr(y,|0|())),p(x),p(y)) r2: and(true(),true()) -> true() r3: and(x,false()) -> false() r4: and(false(),x) -> false() r5: gr(|0|(),|0|()) -> false() r6: gr(|0|(),x) -> false() r7: gr(s(x),|0|()) -> true() r8: gr(s(x),s(y)) -> gr(x,y) r9: p(|0|()) -> |0|() r10: p(s(x)) -> x The set of usable rules consists of (no rules) Take the reduction pair: lexicographic combination of reduction pairs: 1. weighted path order base order: max/plus interpretations on natural numbers: gr#_A(x1,x2) = max{2, x1 - 1, x2 + 1} s_A(x1) = max{1, x1} precedence: gr# = s partial status: pi(gr#) = [2] pi(s) = [1] 2. weighted path order base order: max/plus interpretations on natural numbers: gr#_A(x1,x2) = 0 s_A(x1) = max{2, x1} precedence: gr# = s partial status: pi(gr#) = [] pi(s) = [1] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.