YES We show the termination of the TRS R: admit(x,nil()) -> nil() admit(x,.(u,.(v,.(w(),z)))) -> cond(=(sum(x,u,v),w()),.(u,.(v,.(w(),admit(carry(x,u,v),z))))) cond(true(),y) -> y -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: admit#(x,.(u,.(v,.(w(),z)))) -> cond#(=(sum(x,u,v),w()),.(u,.(v,.(w(),admit(carry(x,u,v),z))))) p2: admit#(x,.(u,.(v,.(w(),z)))) -> admit#(carry(x,u,v),z) and R consists of: r1: admit(x,nil()) -> nil() r2: admit(x,.(u,.(v,.(w(),z)))) -> cond(=(sum(x,u,v),w()),.(u,.(v,.(w(),admit(carry(x,u,v),z))))) r3: cond(true(),y) -> y The estimated dependency graph contains the following SCCs: {p2} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: admit#(x,.(u,.(v,.(w(),z)))) -> admit#(carry(x,u,v),z) and R consists of: r1: admit(x,nil()) -> nil() r2: admit(x,.(u,.(v,.(w(),z)))) -> cond(=(sum(x,u,v),w()),.(u,.(v,.(w(),admit(carry(x,u,v),z))))) r3: cond(true(),y) -> y 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: admit#_A(x1,x2) = max{0, x2 - 4} ._A(x1,x2) = max{6, x1 + 1, x2 + 2} w_A = 1 carry_A(x1,x2,x3) = max{x1 + 1, x2 + 1, x3 + 1} precedence: admit# > . = w = carry partial status: pi(admit#) = [] pi(.) = [2] pi(w) = [] pi(carry) = [1, 2, 3] 2. weighted path order base order: max/plus interpretations on natural numbers: admit#_A(x1,x2) = 0 ._A(x1,x2) = max{2, x2} w_A = 3 carry_A(x1,x2,x3) = max{x1 + 2, x2 - 1, x3 - 1} precedence: admit# = . = w = carry partial status: pi(admit#) = [] pi(.) = [2] pi(w) = [] pi(carry) = [] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.