YES We show the termination of the TRS R: b(x,y) -> c(a(c(y),a(|0|(),x))) a(y,x) -> y a(y,c(b(a(|0|(),x),|0|()))) -> b(a(c(b(|0|(),y)),x),|0|()) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: b#(x,y) -> a#(c(y),a(|0|(),x)) p2: b#(x,y) -> a#(|0|(),x) p3: a#(y,c(b(a(|0|(),x),|0|()))) -> b#(a(c(b(|0|(),y)),x),|0|()) p4: a#(y,c(b(a(|0|(),x),|0|()))) -> a#(c(b(|0|(),y)),x) p5: a#(y,c(b(a(|0|(),x),|0|()))) -> b#(|0|(),y) and R consists of: r1: b(x,y) -> c(a(c(y),a(|0|(),x))) r2: a(y,x) -> y r3: a(y,c(b(a(|0|(),x),|0|()))) -> b(a(c(b(|0|(),y)),x),|0|()) The estimated dependency graph contains the following SCCs: {p1, p2, p3, p4, p5} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: b#(x,y) -> a#(c(y),a(|0|(),x)) p2: a#(y,c(b(a(|0|(),x),|0|()))) -> b#(|0|(),y) p3: b#(x,y) -> a#(|0|(),x) p4: a#(y,c(b(a(|0|(),x),|0|()))) -> a#(c(b(|0|(),y)),x) p5: a#(y,c(b(a(|0|(),x),|0|()))) -> b#(a(c(b(|0|(),y)),x),|0|()) and R consists of: r1: b(x,y) -> c(a(c(y),a(|0|(),x))) r2: a(y,x) -> y r3: a(y,c(b(a(|0|(),x),|0|()))) -> b(a(c(b(|0|(),y)),x),|0|()) The set of usable rules consists of r1, r2, r3 Take the reduction pair: lexicographic combination of reduction pairs: 1. weighted path order base order: max/plus interpretations on natural numbers: b#_A(x1,x2) = max{535, x1 + 138, x2 + 133} a#_A(x1,x2) = max{x1 + 134, x2 + 16} c_A(x1) = max{401, x1 - 78} a_A(x1,x2) = max{379, x1 + 5, x2 + 115} |0|_A = 132 b_A(x1,x2) = max{416, x1 + 228, x2 - 151} precedence: |0| > b# = a = b > a# = c partial status: pi(b#) = [1, 2] pi(a#) = [2] pi(c) = [] pi(a) = [1, 2] pi(|0|) = [] pi(b) = [] 2. weighted path order base order: max/plus interpretations on natural numbers: b#_A(x1,x2) = max{x1 + 168, x2} a#_A(x1,x2) = x2 + 125 c_A(x1) = 27 a_A(x1,x2) = x1 + 42 |0|_A = 0 b_A(x1,x2) = 42 precedence: a = b > c > b# = a# > |0| partial status: pi(b#) = [2] pi(a#) = [] pi(c) = [] pi(a) = [1] pi(|0|) = [] pi(b) = [] The next rules are strictly ordered: p2, p3, p4, p5 We remove them from the problem. -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: b#(x,y) -> a#(c(y),a(|0|(),x)) and R consists of: r1: b(x,y) -> c(a(c(y),a(|0|(),x))) r2: a(y,x) -> y r3: a(y,c(b(a(|0|(),x),|0|()))) -> b(a(c(b(|0|(),y)),x),|0|()) The estimated dependency graph contains the following SCCs: (no SCCs)