YES We show the termination of the TRS R: eq(|0|(),|0|()) -> true() eq(|0|(),s(X)) -> false() eq(s(X),|0|()) -> false() eq(s(X),s(Y)) -> eq(X,Y) rm(N,nil()) -> nil() rm(N,add(M,X)) -> ifrm(eq(N,M),N,add(M,X)) ifrm(true(),N,add(M,X)) -> rm(N,X) ifrm(false(),N,add(M,X)) -> add(M,rm(N,X)) purge(nil()) -> nil() purge(add(N,X)) -> add(N,purge(rm(N,X))) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: eq#(s(X),s(Y)) -> eq#(X,Y) p2: rm#(N,add(M,X)) -> ifrm#(eq(N,M),N,add(M,X)) p3: rm#(N,add(M,X)) -> eq#(N,M) p4: ifrm#(true(),N,add(M,X)) -> rm#(N,X) p5: ifrm#(false(),N,add(M,X)) -> rm#(N,X) p6: purge#(add(N,X)) -> purge#(rm(N,X)) p7: purge#(add(N,X)) -> rm#(N,X) and R consists of: r1: eq(|0|(),|0|()) -> true() r2: eq(|0|(),s(X)) -> false() r3: eq(s(X),|0|()) -> false() r4: eq(s(X),s(Y)) -> eq(X,Y) r5: rm(N,nil()) -> nil() r6: rm(N,add(M,X)) -> ifrm(eq(N,M),N,add(M,X)) r7: ifrm(true(),N,add(M,X)) -> rm(N,X) r8: ifrm(false(),N,add(M,X)) -> add(M,rm(N,X)) r9: purge(nil()) -> nil() r10: purge(add(N,X)) -> add(N,purge(rm(N,X))) The estimated dependency graph contains the following SCCs: {p6} {p2, p4, p5} {p1} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: purge#(add(N,X)) -> purge#(rm(N,X)) and R consists of: r1: eq(|0|(),|0|()) -> true() r2: eq(|0|(),s(X)) -> false() r3: eq(s(X),|0|()) -> false() r4: eq(s(X),s(Y)) -> eq(X,Y) r5: rm(N,nil()) -> nil() r6: rm(N,add(M,X)) -> ifrm(eq(N,M),N,add(M,X)) r7: ifrm(true(),N,add(M,X)) -> rm(N,X) r8: ifrm(false(),N,add(M,X)) -> add(M,rm(N,X)) r9: purge(nil()) -> nil() r10: purge(add(N,X)) -> add(N,purge(rm(N,X))) The set of usable rules consists of r1, r2, r3, r4, r5, r6, r7, r8 Take the reduction pair: lexicographic combination of reduction pairs: 1. weighted path order base order: max/plus interpretations on natural numbers: purge#_A(x1) = max{6, x1 + 4} add_A(x1,x2) = max{x1 + 18, x2 + 12} rm_A(x1,x2) = max{7, x2 + 2} eq_A(x1,x2) = max{x1 + 4, x2 + 4} |0|_A = 1 true_A = 0 s_A(x1) = max{1, x1} false_A = 2 ifrm_A(x1,x2,x3) = max{5, x3 + 2} nil_A = 14 precedence: s > purge# = eq = false = nil > |0| > true > rm = ifrm > add partial status: pi(purge#) = [1] pi(add) = [] pi(rm) = [2] pi(eq) = [1, 2] pi(|0|) = [] pi(true) = [] pi(s) = [1] pi(false) = [] pi(ifrm) = [] pi(nil) = [] 2. weighted path order base order: max/plus interpretations on natural numbers: purge#_A(x1) = max{1, x1} add_A(x1,x2) = 0 rm_A(x1,x2) = 2 eq_A(x1,x2) = max{x1 + 6, x2 - 9} |0|_A = 17 true_A = 18 s_A(x1) = x1 + 8 false_A = 7 ifrm_A(x1,x2,x3) = 2 nil_A = 3 precedence: purge# = add = rm = |0| = true = s = false = ifrm > eq = nil partial status: pi(purge#) = [1] pi(add) = [] pi(rm) = [] pi(eq) = [] pi(|0|) = [] pi(true) = [] pi(s) = [1] pi(false) = [] pi(ifrm) = [] pi(nil) = [] 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: ifrm#(false(),N,add(M,X)) -> rm#(N,X) p2: rm#(N,add(M,X)) -> ifrm#(eq(N,M),N,add(M,X)) p3: ifrm#(true(),N,add(M,X)) -> rm#(N,X) and R consists of: r1: eq(|0|(),|0|()) -> true() r2: eq(|0|(),s(X)) -> false() r3: eq(s(X),|0|()) -> false() r4: eq(s(X),s(Y)) -> eq(X,Y) r5: rm(N,nil()) -> nil() r6: rm(N,add(M,X)) -> ifrm(eq(N,M),N,add(M,X)) r7: ifrm(true(),N,add(M,X)) -> rm(N,X) r8: ifrm(false(),N,add(M,X)) -> add(M,rm(N,X)) r9: purge(nil()) -> nil() r10: purge(add(N,X)) -> add(N,purge(rm(N,X))) The set of usable rules consists of r1, r2, r3, r4 Take the reduction pair: lexicographic combination of reduction pairs: 1. weighted path order base order: max/plus interpretations on natural numbers: ifrm#_A(x1,x2,x3) = max{x1 + 2, x2 + 6, x3} false_A = 6 add_A(x1,x2) = max{x1, x2 + 8} rm#_A(x1,x2) = max{x1 + 6, x2 + 8} eq_A(x1,x2) = max{7, x1 + 4, x2 + 4} true_A = 8 |0|_A = 5 s_A(x1) = x1 + 7 precedence: false = eq = true > add > ifrm# = rm# = |0| = s partial status: pi(ifrm#) = [3] pi(false) = [] pi(add) = [1] pi(rm#) = [2] pi(eq) = [] pi(true) = [] pi(|0|) = [] pi(s) = [1] 2. weighted path order base order: max/plus interpretations on natural numbers: ifrm#_A(x1,x2,x3) = x3 false_A = 6 add_A(x1,x2) = max{4, x1 + 2} rm#_A(x1,x2) = max{1, x2} eq_A(x1,x2) = 5 true_A = 6 |0|_A = 0 s_A(x1) = x1 + 7 precedence: false = add = true = s > eq > ifrm# = rm# = |0| partial status: pi(ifrm#) = [] pi(false) = [] pi(add) = [1] pi(rm#) = [2] pi(eq) = [] pi(true) = [] pi(|0|) = [] pi(s) = [1] 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: rm#(N,add(M,X)) -> ifrm#(eq(N,M),N,add(M,X)) and R consists of: r1: eq(|0|(),|0|()) -> true() r2: eq(|0|(),s(X)) -> false() r3: eq(s(X),|0|()) -> false() r4: eq(s(X),s(Y)) -> eq(X,Y) r5: rm(N,nil()) -> nil() r6: rm(N,add(M,X)) -> ifrm(eq(N,M),N,add(M,X)) r7: ifrm(true(),N,add(M,X)) -> rm(N,X) r8: ifrm(false(),N,add(M,X)) -> add(M,rm(N,X)) r9: purge(nil()) -> nil() r10: purge(add(N,X)) -> add(N,purge(rm(N,X))) The estimated dependency graph contains the following SCCs: (no SCCs) -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: eq#(s(X),s(Y)) -> eq#(X,Y) and R consists of: r1: eq(|0|(),|0|()) -> true() r2: eq(|0|(),s(X)) -> false() r3: eq(s(X),|0|()) -> false() r4: eq(s(X),s(Y)) -> eq(X,Y) r5: rm(N,nil()) -> nil() r6: rm(N,add(M,X)) -> ifrm(eq(N,M),N,add(M,X)) r7: ifrm(true(),N,add(M,X)) -> rm(N,X) r8: ifrm(false(),N,add(M,X)) -> add(M,rm(N,X)) r9: purge(nil()) -> nil() r10: purge(add(N,X)) -> add(N,purge(rm(N,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: eq#_A(x1,x2) = max{2, x1 - 1, x2 + 1} s_A(x1) = max{1, x1} precedence: eq# = s partial status: pi(eq#) = [2] pi(s) = [1] 2. weighted path order base order: max/plus interpretations on natural numbers: eq#_A(x1,x2) = 0 s_A(x1) = max{2, x1} precedence: eq# = s partial status: pi(eq#) = [] pi(s) = [1] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.