YES We show the termination of the TRS R: c(c(c(a(x,y)))) -> b(c(c(c(c(y)))),x) c(c(b(c(y),|0|()))) -> a(|0|(),c(c(a(y,|0|())))) c(c(a(a(y,|0|()),x))) -> c(y) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: c#(c(c(a(x,y)))) -> c#(c(c(c(y)))) p2: c#(c(c(a(x,y)))) -> c#(c(c(y))) p3: c#(c(c(a(x,y)))) -> c#(c(y)) p4: c#(c(c(a(x,y)))) -> c#(y) p5: c#(c(b(c(y),|0|()))) -> c#(c(a(y,|0|()))) p6: c#(c(b(c(y),|0|()))) -> c#(a(y,|0|())) p7: c#(c(a(a(y,|0|()),x))) -> c#(y) and R consists of: r1: c(c(c(a(x,y)))) -> b(c(c(c(c(y)))),x) r2: c(c(b(c(y),|0|()))) -> a(|0|(),c(c(a(y,|0|())))) r3: c(c(a(a(y,|0|()),x))) -> c(y) The estimated dependency graph contains the following SCCs: {p1, p2, p3, p4, p5, p7} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: c#(c(c(a(x,y)))) -> c#(c(c(c(y)))) p2: c#(c(a(a(y,|0|()),x))) -> c#(y) p3: c#(c(b(c(y),|0|()))) -> c#(c(a(y,|0|()))) p4: c#(c(c(a(x,y)))) -> c#(y) p5: c#(c(c(a(x,y)))) -> c#(c(y)) p6: c#(c(c(a(x,y)))) -> c#(c(c(y))) and R consists of: r1: c(c(c(a(x,y)))) -> b(c(c(c(c(y)))),x) r2: c(c(b(c(y),|0|()))) -> a(|0|(),c(c(a(y,|0|())))) r3: c(c(a(a(y,|0|()),x))) -> c(y) 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: matrix interpretations: carrier: N^2 order: standard order interpretations: c#_A(x1) = ((0,1),(1,0)) x1 c_A(x1) = ((1,1),(1,1)) x1 + (2,13) a_A(x1,x2) = ((1,1),(0,0)) x1 + ((1,1),(1,1)) x2 + (108,2) |0|_A() = (1,9) b_A(x1,x2) = ((1,0),(1,0)) x1 + ((1,1),(1,1)) x2 + (380,276) precedence: c# = c = a = |0| = b partial status: pi(c#) = [] pi(c) = [1] pi(a) = [] pi(|0|) = [] pi(b) = [] 2. weighted path order base order: matrix interpretations: carrier: N^2 order: standard order interpretations: c#_A(x1) = (2,0) c_A(x1) = (3,0) a_A(x1,x2) = (0,0) |0|_A() = (1,0) b_A(x1,x2) = (0,0) precedence: c# = c = |0| > a = b partial status: pi(c#) = [] pi(c) = [] pi(a) = [] pi(|0|) = [] pi(b) = [] The next rules are strictly ordered: p5 We remove them from the problem. -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: c#(c(c(a(x,y)))) -> c#(c(c(c(y)))) p2: c#(c(a(a(y,|0|()),x))) -> c#(y) p3: c#(c(b(c(y),|0|()))) -> c#(c(a(y,|0|()))) p4: c#(c(c(a(x,y)))) -> c#(y) p5: c#(c(c(a(x,y)))) -> c#(c(c(y))) and R consists of: r1: c(c(c(a(x,y)))) -> b(c(c(c(c(y)))),x) r2: c(c(b(c(y),|0|()))) -> a(|0|(),c(c(a(y,|0|())))) r3: c(c(a(a(y,|0|()),x))) -> c(y) 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: c#(c(c(a(x,y)))) -> c#(c(c(c(y)))) p2: c#(c(c(a(x,y)))) -> c#(c(c(y))) p3: c#(c(c(a(x,y)))) -> c#(y) p4: c#(c(b(c(y),|0|()))) -> c#(c(a(y,|0|()))) p5: c#(c(a(a(y,|0|()),x))) -> c#(y) and R consists of: r1: c(c(c(a(x,y)))) -> b(c(c(c(c(y)))),x) r2: c(c(b(c(y),|0|()))) -> a(|0|(),c(c(a(y,|0|())))) r3: c(c(a(a(y,|0|()),x))) -> c(y) 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: matrix interpretations: carrier: N^2 order: standard order interpretations: c#_A(x1) = ((1,0),(1,1)) x1 + (39,0) c_A(x1) = ((1,1),(1,0)) x1 + (16,1) a_A(x1,x2) = x1 + ((1,1),(1,0)) x2 + (12,49) b_A(x1,x2) = x1 + ((1,1),(1,1)) x2 + (84,40) |0|_A() = (1,2) precedence: c > b = |0| > c# = a partial status: pi(c#) = [1] pi(c) = [] pi(a) = [1] pi(b) = [1] pi(|0|) = [] 2. weighted path order base order: matrix interpretations: carrier: N^2 order: standard order interpretations: c#_A(x1) = (0,0) c_A(x1) = (1,0) a_A(x1,x2) = ((1,0),(1,1)) x1 b_A(x1,x2) = ((0,0),(1,0)) x1 |0|_A() = (0,2) precedence: c# = c > |0| > a = b partial status: pi(c#) = [] pi(c) = [] pi(a) = [] pi(b) = [] pi(|0|) = [] The next rules are strictly ordered: p3 We remove them from the problem. -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: c#(c(c(a(x,y)))) -> c#(c(c(c(y)))) p2: c#(c(c(a(x,y)))) -> c#(c(c(y))) p3: c#(c(b(c(y),|0|()))) -> c#(c(a(y,|0|()))) p4: c#(c(a(a(y,|0|()),x))) -> c#(y) and R consists of: r1: c(c(c(a(x,y)))) -> b(c(c(c(c(y)))),x) r2: c(c(b(c(y),|0|()))) -> a(|0|(),c(c(a(y,|0|())))) r3: c(c(a(a(y,|0|()),x))) -> c(y) The estimated dependency graph contains the following SCCs: {p1, p2, p3, p4} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: c#(c(c(a(x,y)))) -> c#(c(c(c(y)))) p2: c#(c(a(a(y,|0|()),x))) -> c#(y) p3: c#(c(b(c(y),|0|()))) -> c#(c(a(y,|0|()))) p4: c#(c(c(a(x,y)))) -> c#(c(c(y))) and R consists of: r1: c(c(c(a(x,y)))) -> b(c(c(c(c(y)))),x) r2: c(c(b(c(y),|0|()))) -> a(|0|(),c(c(a(y,|0|())))) r3: c(c(a(a(y,|0|()),x))) -> c(y) 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: matrix interpretations: carrier: N^2 order: standard order interpretations: c#_A(x1) = ((1,0),(0,0)) x1 c_A(x1) = ((1,0),(1,0)) x1 a_A(x1,x2) = ((1,0),(1,0)) x1 + x2 |0|_A() = (0,1) b_A(x1,x2) = ((1,0),(0,0)) x1 + ((1,0),(0,0)) x2 precedence: c# = c = a = |0| = b partial status: pi(c#) = [] pi(c) = [] pi(a) = [] pi(|0|) = [] pi(b) = [] 2. weighted path order base order: matrix interpretations: carrier: N^2 order: standard order interpretations: c#_A(x1) = x1 + (0,7) c_A(x1) = ((1,1),(1,1)) x1 a_A(x1,x2) = x1 + ((1,1),(1,1)) x2 + (3,4) |0|_A() = (1,1) b_A(x1,x2) = ((0,1),(1,0)) x1 + (20,28) precedence: a > c > |0| = b > c# partial status: pi(c#) = [1] pi(c) = [1] pi(a) = [2] pi(|0|) = [] pi(b) = [] The next rules are strictly ordered: p1, p3 We remove them from the problem. -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: c#(c(a(a(y,|0|()),x))) -> c#(y) p2: c#(c(c(a(x,y)))) -> c#(c(c(y))) and R consists of: r1: c(c(c(a(x,y)))) -> b(c(c(c(c(y)))),x) r2: c(c(b(c(y),|0|()))) -> a(|0|(),c(c(a(y,|0|())))) r3: c(c(a(a(y,|0|()),x))) -> c(y) The estimated dependency graph contains the following SCCs: {p1, p2} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: c#(c(a(a(y,|0|()),x))) -> c#(y) p2: c#(c(c(a(x,y)))) -> c#(c(c(y))) and R consists of: r1: c(c(c(a(x,y)))) -> b(c(c(c(c(y)))),x) r2: c(c(b(c(y),|0|()))) -> a(|0|(),c(c(a(y,|0|())))) r3: c(c(a(a(y,|0|()),x))) -> c(y) 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: matrix interpretations: carrier: N^2 order: standard order interpretations: c#_A(x1) = ((1,0),(0,0)) x1 c_A(x1) = ((1,0),(1,0)) x1 + (2,0) a_A(x1,x2) = ((1,0),(0,0)) x1 + ((1,0),(0,0)) x2 + (0,1) |0|_A() = (0,3) b_A(x1,x2) = ((0,1),(0,0)) x1 + (0,3) precedence: c# = c = a = |0| = b partial status: pi(c#) = [] pi(c) = [] pi(a) = [] pi(|0|) = [] pi(b) = [] 2. weighted path order base order: matrix interpretations: carrier: N^2 order: standard order interpretations: c#_A(x1) = x1 c_A(x1) = ((0,1),(1,0)) x1 + (2,3) a_A(x1,x2) = ((1,0),(1,1)) x2 + (1,1) |0|_A() = (0,1) b_A(x1,x2) = (8,9) precedence: c > a = b > c# > |0| partial status: pi(c#) = [1] pi(c) = [] pi(a) = [] pi(|0|) = [] pi(b) = [] The next rules are strictly ordered: p1 We remove them from the problem. -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: c#(c(c(a(x,y)))) -> c#(c(c(y))) and R consists of: r1: c(c(c(a(x,y)))) -> b(c(c(c(c(y)))),x) r2: c(c(b(c(y),|0|()))) -> a(|0|(),c(c(a(y,|0|())))) r3: c(c(a(a(y,|0|()),x))) -> c(y) The estimated dependency graph contains the following SCCs: {p1} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: c#(c(c(a(x,y)))) -> c#(c(c(y))) and R consists of: r1: c(c(c(a(x,y)))) -> b(c(c(c(c(y)))),x) r2: c(c(b(c(y),|0|()))) -> a(|0|(),c(c(a(y,|0|())))) r3: c(c(a(a(y,|0|()),x))) -> c(y) 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: matrix interpretations: carrier: N^2 order: standard order interpretations: c#_A(x1) = x1 + (1,12) c_A(x1) = ((1,1),(1,1)) x1 a_A(x1,x2) = ((0,0),(1,1)) x1 + ((1,1),(1,1)) x2 + (0,12) b_A(x1,x2) = x1 + ((1,0),(1,1)) x2 + (23,13) |0|_A() = (1,1) precedence: c = a > c# = |0| > b partial status: pi(c#) = [1] pi(c) = [] pi(a) = [] pi(b) = [2] pi(|0|) = [] 2. weighted path order base order: matrix interpretations: carrier: N^2 order: standard order interpretations: c#_A(x1) = ((1,0),(0,0)) x1 + (1,4) c_A(x1) = (3,3) a_A(x1,x2) = (0,1) b_A(x1,x2) = (2,2) |0|_A() = (1,0) precedence: c > a = b = |0| > c# partial status: pi(c#) = [] pi(c) = [] pi(a) = [] pi(b) = [] pi(|0|) = [] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.