YES We show the termination of the TRS R: if(true(),x,y) -> x if(false(),x,y) -> y eq(|0|(),|0|()) -> true() eq(|0|(),s(x)) -> false() eq(s(x),|0|()) -> false() eq(s(x),s(y)) -> eq(x,y) app(nil(),l) -> l app(cons(x,l1),l2) -> cons(x,app(l1,l2)) app(app(l1,l2),l3) -> app(l1,app(l2,l3)) mem(x,nil()) -> false() mem(x,cons(y,l)) -> ifmem(eq(x,y),x,l) ifmem(true(),x,l) -> true() ifmem(false(),x,l) -> mem(x,l) inter(x,nil()) -> nil() inter(nil(),x) -> nil() inter(app(l1,l2),l3) -> app(inter(l1,l3),inter(l2,l3)) inter(l1,app(l2,l3)) -> app(inter(l1,l2),inter(l1,l3)) inter(cons(x,l1),l2) -> ifinter(mem(x,l2),x,l1,l2) inter(l1,cons(x,l2)) -> ifinter(mem(x,l1),x,l2,l1) ifinter(true(),x,l1,l2) -> cons(x,inter(l1,l2)) ifinter(false(),x,l1,l2) -> inter(l1,l2) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: eq#(s(x),s(y)) -> eq#(x,y) p2: app#(cons(x,l1),l2) -> app#(l1,l2) p3: app#(app(l1,l2),l3) -> app#(l1,app(l2,l3)) p4: app#(app(l1,l2),l3) -> app#(l2,l3) p5: mem#(x,cons(y,l)) -> ifmem#(eq(x,y),x,l) p6: mem#(x,cons(y,l)) -> eq#(x,y) p7: ifmem#(false(),x,l) -> mem#(x,l) p8: inter#(app(l1,l2),l3) -> app#(inter(l1,l3),inter(l2,l3)) p9: inter#(app(l1,l2),l3) -> inter#(l1,l3) p10: inter#(app(l1,l2),l3) -> inter#(l2,l3) p11: inter#(l1,app(l2,l3)) -> app#(inter(l1,l2),inter(l1,l3)) p12: inter#(l1,app(l2,l3)) -> inter#(l1,l2) p13: inter#(l1,app(l2,l3)) -> inter#(l1,l3) p14: inter#(cons(x,l1),l2) -> ifinter#(mem(x,l2),x,l1,l2) p15: inter#(cons(x,l1),l2) -> mem#(x,l2) p16: inter#(l1,cons(x,l2)) -> ifinter#(mem(x,l1),x,l2,l1) p17: inter#(l1,cons(x,l2)) -> mem#(x,l1) p18: ifinter#(true(),x,l1,l2) -> inter#(l1,l2) p19: ifinter#(false(),x,l1,l2) -> inter#(l1,l2) and R consists of: r1: if(true(),x,y) -> x r2: if(false(),x,y) -> y r3: eq(|0|(),|0|()) -> true() r4: eq(|0|(),s(x)) -> false() r5: eq(s(x),|0|()) -> false() r6: eq(s(x),s(y)) -> eq(x,y) r7: app(nil(),l) -> l r8: app(cons(x,l1),l2) -> cons(x,app(l1,l2)) r9: app(app(l1,l2),l3) -> app(l1,app(l2,l3)) r10: mem(x,nil()) -> false() r11: mem(x,cons(y,l)) -> ifmem(eq(x,y),x,l) r12: ifmem(true(),x,l) -> true() r13: ifmem(false(),x,l) -> mem(x,l) r14: inter(x,nil()) -> nil() r15: inter(nil(),x) -> nil() r16: inter(app(l1,l2),l3) -> app(inter(l1,l3),inter(l2,l3)) r17: inter(l1,app(l2,l3)) -> app(inter(l1,l2),inter(l1,l3)) r18: inter(cons(x,l1),l2) -> ifinter(mem(x,l2),x,l1,l2) r19: inter(l1,cons(x,l2)) -> ifinter(mem(x,l1),x,l2,l1) r20: ifinter(true(),x,l1,l2) -> cons(x,inter(l1,l2)) r21: ifinter(false(),x,l1,l2) -> inter(l1,l2) The estimated dependency graph contains the following SCCs: {p9, p10, p12, p13, p14, p16, p18, p19} {p5, p7} {p1} {p2, p3, p4} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: ifinter#(false(),x,l1,l2) -> inter#(l1,l2) p2: inter#(l1,cons(x,l2)) -> ifinter#(mem(x,l1),x,l2,l1) p3: ifinter#(true(),x,l1,l2) -> inter#(l1,l2) p4: inter#(cons(x,l1),l2) -> ifinter#(mem(x,l2),x,l1,l2) p5: inter#(l1,app(l2,l3)) -> inter#(l1,l3) p6: inter#(l1,app(l2,l3)) -> inter#(l1,l2) p7: inter#(app(l1,l2),l3) -> inter#(l2,l3) p8: inter#(app(l1,l2),l3) -> inter#(l1,l3) and R consists of: r1: if(true(),x,y) -> x r2: if(false(),x,y) -> y r3: eq(|0|(),|0|()) -> true() r4: eq(|0|(),s(x)) -> false() r5: eq(s(x),|0|()) -> false() r6: eq(s(x),s(y)) -> eq(x,y) r7: app(nil(),l) -> l r8: app(cons(x,l1),l2) -> cons(x,app(l1,l2)) r9: app(app(l1,l2),l3) -> app(l1,app(l2,l3)) r10: mem(x,nil()) -> false() r11: mem(x,cons(y,l)) -> ifmem(eq(x,y),x,l) r12: ifmem(true(),x,l) -> true() r13: ifmem(false(),x,l) -> mem(x,l) r14: inter(x,nil()) -> nil() r15: inter(nil(),x) -> nil() r16: inter(app(l1,l2),l3) -> app(inter(l1,l3),inter(l2,l3)) r17: inter(l1,app(l2,l3)) -> app(inter(l1,l2),inter(l1,l3)) r18: inter(cons(x,l1),l2) -> ifinter(mem(x,l2),x,l1,l2) r19: inter(l1,cons(x,l2)) -> ifinter(mem(x,l1),x,l2,l1) r20: ifinter(true(),x,l1,l2) -> cons(x,inter(l1,l2)) r21: ifinter(false(),x,l1,l2) -> inter(l1,l2) The set of usable rules consists of r1, r2, r3, r4, r5, r6, r10, r12 Take the reduction pair: generalized weighted path order (>=MG, >G) base order 1: trivial reduction triple (T x T, T x T, Φ) base order 2: lexicographic combination of reduction triples: 1. marked-algebra reduction triple (>=A, >=A!, >A!): max/plus interpretation on natural numbers: ifinter#_A(x1,x2,x3,x4) = 1 false_A = 3 inter#_A(x1,x2) = 1 cons_A(x1,x2) = max{3, x1 - 26, x2 + 2} mem_A(x1,x2) = max{42, x1 + 12} true_A = 42 app_A(x1,x2) = max{27, x1 + 9, x2 - 8} if_A(x1,x2,x3) = max{x1, x2, x3} eq_A(x1,x2) = max{41, x1 + 1, x2 + 2} |0|_A = 40 s_A(x1) = x1 nil_A = 10 ifmem_A(x1,x2,x3) = max{42, x1 - 43, x2 + 12} ifinter#!_A(x1,x2,x3,x4) = 0 false!_A = 0 inter#!_A(x1,x2) = 0 cons!_A(x1,x2) = x1 + 8 mem!_A(x1,x2) = x1 + 5 true!_A = 5 app!_A(x1,x2) = max{x1 + 25, x2 + 9} if!_A(x1,x2,x3) = max{x1, x2, x3} eq!_A(x1,x2) = max{1, x2 - 2} |0|!_A = 4 s!_A(x1) = max{0, x1 - 1} nil!_A = 1 ifmem!_A(x1,x2,x3) = max{4, x2} 2. marked-algebra reduction triple (>=A, >=A!, >A!): matrix interpretation with standard point-wise order: carrier: N^1 order: standard order interpretations: ifinter#_A(x1,x2,x3,x4) = x3 + x4 false_A() = 1 inter#_A(x1,x2) = x1 + x2 cons_A(x1,x2) = x1 + x2 + 2 mem_A(x1,x2) = 1 true_A() = 1 app_A(x1,x2) = x1 + x2 if_A(x1,x2,x3) = x2 + x3 eq_A(x1,x2) = 1 |0|_A() = 0 s_A(x1) = x1 nil_A() = 1 ifmem_A(x1,x2,x3) = 1 ifinter#!_A(x1,x2,x3,x4) = x3 + x4 + 5 false!_A() = 0 inter#!_A(x1,x2) = x1 + x2 + 4 cons!_A(x1,x2) = 6 mem!_A(x1,x2) = 1 true!_A() = 7 app!_A(x1,x2) = 3 if!_A(x1,x2,x3) = x1 + x2 + x3 eq!_A(x1,x2) = x1 + x2 + 8 |0|!_A() = 8 s!_A(x1) = 9 nil!_A() = 3 ifmem!_A(x1,x2,x3) = 0 partial status: pi(ifinter#) = [] pi(false) = [] pi(inter#) = [] pi(cons) = [2] pi(mem) = [] pi(true) = [] pi(app) = [2] pi(if) = [2, 3] pi(eq) = [] pi(|0|) = [] pi(s) = [1] pi(nil) = [] pi(ifmem) = [1] The following rules are removed: p1, p2, p3, p4 -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: inter#(l1,app(l2,l3)) -> inter#(l1,l3) p2: inter#(l1,app(l2,l3)) -> inter#(l1,l2) p3: inter#(app(l1,l2),l3) -> inter#(l2,l3) p4: inter#(app(l1,l2),l3) -> inter#(l1,l3) and R consists of: r1: if(true(),x,y) -> x r2: if(false(),x,y) -> y r3: eq(|0|(),|0|()) -> true() r4: eq(|0|(),s(x)) -> false() r5: eq(s(x),|0|()) -> false() r6: eq(s(x),s(y)) -> eq(x,y) r7: app(nil(),l) -> l r8: app(cons(x,l1),l2) -> cons(x,app(l1,l2)) r9: app(app(l1,l2),l3) -> app(l1,app(l2,l3)) r10: mem(x,nil()) -> false() r11: mem(x,cons(y,l)) -> ifmem(eq(x,y),x,l) r12: ifmem(true(),x,l) -> true() r13: ifmem(false(),x,l) -> mem(x,l) r14: inter(x,nil()) -> nil() r15: inter(nil(),x) -> nil() r16: inter(app(l1,l2),l3) -> app(inter(l1,l3),inter(l2,l3)) r17: inter(l1,app(l2,l3)) -> app(inter(l1,l2),inter(l1,l3)) r18: inter(cons(x,l1),l2) -> ifinter(mem(x,l2),x,l1,l2) r19: inter(l1,cons(x,l2)) -> ifinter(mem(x,l1),x,l2,l1) r20: ifinter(true(),x,l1,l2) -> cons(x,inter(l1,l2)) r21: ifinter(false(),x,l1,l2) -> inter(l1,l2) 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: inter#(l1,app(l2,l3)) -> inter#(l1,l3) p2: inter#(app(l1,l2),l3) -> inter#(l1,l3) p3: inter#(app(l1,l2),l3) -> inter#(l2,l3) p4: inter#(l1,app(l2,l3)) -> inter#(l1,l2) and R consists of: r1: if(true(),x,y) -> x r2: if(false(),x,y) -> y r3: eq(|0|(),|0|()) -> true() r4: eq(|0|(),s(x)) -> false() r5: eq(s(x),|0|()) -> false() r6: eq(s(x),s(y)) -> eq(x,y) r7: app(nil(),l) -> l r8: app(cons(x,l1),l2) -> cons(x,app(l1,l2)) r9: app(app(l1,l2),l3) -> app(l1,app(l2,l3)) r10: mem(x,nil()) -> false() r11: mem(x,cons(y,l)) -> ifmem(eq(x,y),x,l) r12: ifmem(true(),x,l) -> true() r13: ifmem(false(),x,l) -> mem(x,l) r14: inter(x,nil()) -> nil() r15: inter(nil(),x) -> nil() r16: inter(app(l1,l2),l3) -> app(inter(l1,l3),inter(l2,l3)) r17: inter(l1,app(l2,l3)) -> app(inter(l1,l2),inter(l1,l3)) r18: inter(cons(x,l1),l2) -> ifinter(mem(x,l2),x,l1,l2) r19: inter(l1,cons(x,l2)) -> ifinter(mem(x,l1),x,l2,l1) r20: ifinter(true(),x,l1,l2) -> cons(x,inter(l1,l2)) r21: ifinter(false(),x,l1,l2) -> inter(l1,l2) The set of usable rules consists of r1, r2 Take the reduction pair: generalized weighted path order (>=MG, >G) base order 1: trivial reduction triple (T x T, T x T, Φ) base order 2: lexicographic combination of reduction triples: 1. marked-algebra reduction triple (>=A, >=A!, >A!): max/plus interpretation on natural numbers: inter#_A(x1,x2) = max{x1, x2} app_A(x1,x2) = max{13, x1 + 1, x2 + 2} if_A(x1,x2,x3) = max{x1, x2, x3} true_A = 1 false_A = 2 inter#!_A(x1,x2) = x1 + 14 app!_A(x1,x2) = max{29, x1 + 15, x2 + 28} if!_A(x1,x2,x3) = max{x1, x2, x3} true!_A = 1 false!_A = 32 2. marked-algebra reduction triple (>=A, >=A!, >A!): matrix interpretation with standard point-wise order: carrier: N^1 order: standard order interpretations: inter#_A(x1,x2) = x1 + x2 app_A(x1,x2) = x1 + x2 + 1 if_A(x1,x2,x3) = x2 + x3 true_A() = 4 false_A() = 4 inter#!_A(x1,x2) = x1 + x2 app!_A(x1,x2) = 1 if!_A(x1,x2,x3) = x1 + x2 + x3 true!_A() = 1 false!_A() = 6 partial status: pi(inter#) = [] pi(app) = [] pi(if) = [2, 3] pi(true) = [] pi(false) = [] The following rules are removed: p1, p2, p3, p4 Then no dependency pair remains. -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: ifmem#(false(),x,l) -> mem#(x,l) p2: mem#(x,cons(y,l)) -> ifmem#(eq(x,y),x,l) and R consists of: r1: if(true(),x,y) -> x r2: if(false(),x,y) -> y r3: eq(|0|(),|0|()) -> true() r4: eq(|0|(),s(x)) -> false() r5: eq(s(x),|0|()) -> false() r6: eq(s(x),s(y)) -> eq(x,y) r7: app(nil(),l) -> l r8: app(cons(x,l1),l2) -> cons(x,app(l1,l2)) r9: app(app(l1,l2),l3) -> app(l1,app(l2,l3)) r10: mem(x,nil()) -> false() r11: mem(x,cons(y,l)) -> ifmem(eq(x,y),x,l) r12: ifmem(true(),x,l) -> true() r13: ifmem(false(),x,l) -> mem(x,l) r14: inter(x,nil()) -> nil() r15: inter(nil(),x) -> nil() r16: inter(app(l1,l2),l3) -> app(inter(l1,l3),inter(l2,l3)) r17: inter(l1,app(l2,l3)) -> app(inter(l1,l2),inter(l1,l3)) r18: inter(cons(x,l1),l2) -> ifinter(mem(x,l2),x,l1,l2) r19: inter(l1,cons(x,l2)) -> ifinter(mem(x,l1),x,l2,l1) r20: ifinter(true(),x,l1,l2) -> cons(x,inter(l1,l2)) r21: ifinter(false(),x,l1,l2) -> inter(l1,l2) The set of usable rules consists of r1, r2, r3, r4, r5, r6 Take the reduction pair: generalized weighted path order (>=MG, >G) base order 1: trivial reduction triple (T x T, T x T, Φ) base order 2: lexicographic combination of reduction triples: 1. marked-algebra reduction triple (>=A, >=A!, >A!): max/plus interpretation on natural numbers: ifmem#_A(x1,x2,x3) = max{0, x1 - 16, x2 - 2, x3 - 8} false_A = 2 mem#_A(x1,x2) = max{0, x1 - 2, x2 - 8} cons_A(x1,x2) = max{x1 + 6, x2} eq_A(x1,x2) = 15 if_A(x1,x2,x3) = max{x1, x2, x3} true_A = 2 |0|_A = 0 s_A(x1) = 0 ifmem#!_A(x1,x2,x3) = max{2, x1 - 3, x3 - 1} false!_A = 0 mem#!_A(x1,x2) = max{1, x2 - 2} cons!_A(x1,x2) = max{67, x1 + 3, x2 + 1} eq!_A(x1,x2) = 0 if!_A(x1,x2,x3) = max{x1, x2, x3} true!_A = 0 |0|!_A = 1 s!_A(x1) = max{0, x1 - 1} 2. marked-algebra reduction triple (>=A, >=A!, >A!): matrix interpretation with standard point-wise order: carrier: N^1 order: standard order interpretations: ifmem#_A(x1,x2,x3) = x1 + x3 + 4 false_A() = 3 mem#_A(x1,x2) = x2 cons_A(x1,x2) = x1 + x2 + 5 eq_A(x1,x2) = x2 + 1 if_A(x1,x2,x3) = x2 + x3 true_A() = 1 |0|_A() = 2 s_A(x1) = x1 + 2 ifmem#!_A(x1,x2,x3) = x1 + x2 + x3 + 1 false!_A() = 0 mem#!_A(x1,x2) = 3 cons!_A(x1,x2) = 1 eq!_A(x1,x2) = x1 + x2 + 4 if!_A(x1,x2,x3) = x1 + x2 + x3 true!_A() = 0 |0|!_A() = 1 s!_A(x1) = 1 partial status: pi(ifmem#) = [3] pi(false) = [] pi(mem#) = [2] pi(cons) = [1, 2] pi(eq) = [] pi(if) = [2, 3] pi(true) = [] pi(|0|) = [] pi(s) = [] The following rules are removed: p1, p2 Then no dependency pair remains. -- 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: if(true(),x,y) -> x r2: if(false(),x,y) -> y r3: eq(|0|(),|0|()) -> true() r4: eq(|0|(),s(x)) -> false() r5: eq(s(x),|0|()) -> false() r6: eq(s(x),s(y)) -> eq(x,y) r7: app(nil(),l) -> l r8: app(cons(x,l1),l2) -> cons(x,app(l1,l2)) r9: app(app(l1,l2),l3) -> app(l1,app(l2,l3)) r10: mem(x,nil()) -> false() r11: mem(x,cons(y,l)) -> ifmem(eq(x,y),x,l) r12: ifmem(true(),x,l) -> true() r13: ifmem(false(),x,l) -> mem(x,l) r14: inter(x,nil()) -> nil() r15: inter(nil(),x) -> nil() r16: inter(app(l1,l2),l3) -> app(inter(l1,l3),inter(l2,l3)) r17: inter(l1,app(l2,l3)) -> app(inter(l1,l2),inter(l1,l3)) r18: inter(cons(x,l1),l2) -> ifinter(mem(x,l2),x,l1,l2) r19: inter(l1,cons(x,l2)) -> ifinter(mem(x,l1),x,l2,l1) r20: ifinter(true(),x,l1,l2) -> cons(x,inter(l1,l2)) r21: ifinter(false(),x,l1,l2) -> inter(l1,l2) The set of usable rules consists of r1, r2, r14, r15 Take the reduction pair: generalized weighted path order (>=MG, >G) base order 1: trivial reduction triple (T x T, T x T, Φ) base order 2: lexicographic combination of reduction triples: 1. marked-algebra reduction triple (>=A, >=A!, >A!): max/plus interpretation on natural numbers: eq#_A(x1,x2) = max{x1, x2} s_A(x1) = max{1, x1} if_A(x1,x2,x3) = max{x1, x2, x3} true_A = 1 false_A = 2 inter_A(x1,x2) = max{8, x1 - 9, x2 - 9} nil_A = 1 eq#!_A(x1,x2) = max{3, x1 - 2, x2 - 2} s!_A(x1) = 2 if!_A(x1,x2,x3) = max{x1, x2, x3} true!_A = 13 false!_A = 1 inter!_A(x1,x2) = max{0, x1 - 3} nil!_A = 0 2. marked-algebra reduction triple (>=A, >=A!, >A!): matrix interpretation with standard point-wise order: carrier: N^1 order: standard order interpretations: eq#_A(x1,x2) = x1 + x2 s_A(x1) = x1 + 1 if_A(x1,x2,x3) = x2 + x3 true_A() = 4 false_A() = 4 inter_A(x1,x2) = x1 + x2 + 1 nil_A() = 5 eq#!_A(x1,x2) = x1 + x2 s!_A(x1) = 7 if!_A(x1,x2,x3) = x1 + x2 + x3 true!_A() = 2 false!_A() = 6 inter!_A(x1,x2) = x1 + x2 + 3 nil!_A() = 7 partial status: pi(eq#) = [] pi(s) = [1] pi(if) = [2, 3] pi(true) = [] pi(false) = [] pi(inter) = [1, 2] pi(nil) = [] The following rules are removed: p1 Then no dependency pair remains. -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: app#(cons(x,l1),l2) -> app#(l1,l2) p2: app#(app(l1,l2),l3) -> app#(l2,l3) p3: app#(app(l1,l2),l3) -> app#(l1,app(l2,l3)) and R consists of: r1: if(true(),x,y) -> x r2: if(false(),x,y) -> y r3: eq(|0|(),|0|()) -> true() r4: eq(|0|(),s(x)) -> false() r5: eq(s(x),|0|()) -> false() r6: eq(s(x),s(y)) -> eq(x,y) r7: app(nil(),l) -> l r8: app(cons(x,l1),l2) -> cons(x,app(l1,l2)) r9: app(app(l1,l2),l3) -> app(l1,app(l2,l3)) r10: mem(x,nil()) -> false() r11: mem(x,cons(y,l)) -> ifmem(eq(x,y),x,l) r12: ifmem(true(),x,l) -> true() r13: ifmem(false(),x,l) -> mem(x,l) r14: inter(x,nil()) -> nil() r15: inter(nil(),x) -> nil() r16: inter(app(l1,l2),l3) -> app(inter(l1,l3),inter(l2,l3)) r17: inter(l1,app(l2,l3)) -> app(inter(l1,l2),inter(l1,l3)) r18: inter(cons(x,l1),l2) -> ifinter(mem(x,l2),x,l1,l2) r19: inter(l1,cons(x,l2)) -> ifinter(mem(x,l1),x,l2,l1) r20: ifinter(true(),x,l1,l2) -> cons(x,inter(l1,l2)) r21: ifinter(false(),x,l1,l2) -> inter(l1,l2) The set of usable rules consists of r1, r2, r7, r8, r9 Take the reduction pair: generalized weighted path order (>=MG, >G) base order 1: trivial reduction triple (T x T, T x T, Φ) base order 2: lexicographic combination of reduction triples: 1. marked-algebra reduction triple (>=A, >=A!, >A!): max/plus interpretation on natural numbers: app#_A(x1,x2) = max{0, x1 - 21, x2 - 23} cons_A(x1,x2) = max{9, x1 - 10, x2} app_A(x1,x2) = max{20, x1 + 2, x2} if_A(x1,x2,x3) = max{x1, x2, x3} true_A = 2 false_A = 3 nil_A = 20 app#!_A(x1,x2) = max{x1 + 9, x2 - 3} cons!_A(x1,x2) = max{7, x1 - 7, x2 - 21} app!_A(x1,x2) = max{x1 + 16, x2 + 14} if!_A(x1,x2,x3) = max{x1, x2, x3} true!_A = 3 false!_A = 1 nil!_A = 3 2. marked-algebra reduction triple (>=A, >=A!, >A!): matrix interpretation with standard point-wise order: carrier: N^1 order: standard order interpretations: app#_A(x1,x2) = x1 + x2 cons_A(x1,x2) = x1 + x2 + 1 app_A(x1,x2) = x1 + x2 + 1 if_A(x1,x2,x3) = x2 + x3 true_A() = 4 false_A() = 4 nil_A() = 1 app#!_A(x1,x2) = x1 + 4 cons!_A(x1,x2) = x2 + 2 app!_A(x1,x2) = x1 + 3 if!_A(x1,x2,x3) = x1 + x2 + x3 true!_A() = 0 false!_A() = 0 nil!_A() = 1 partial status: pi(app#) = [] pi(cons) = [] pi(app) = [1, 2] pi(if) = [2, 3] pi(true) = [] pi(false) = [] pi(nil) = [] The following rules are removed: p1, p2, p3 Then no dependency pair remains.