Left Termination of the query pattern
append3(g,g,g,a)
w.r.t. the given Prolog program could successfully be proven:

(0) Obligation:

Clauses:

append([], L, L).
append(.(H, L1), L2, .(H, L3)) :- append(L1, L2, L3).
append3(A, B, C, D) :- ','(append(A, B, E), append(E, C, D)).

Query: append3(g,g,g,a)

(1) PrologToDTProblemTransformerProof (SOUND transformation)

Built DT problem from termination graph DT10.

digraph dp_graph {
node [outthreshold=100, inthreshold=100];
1 [label="C: append3(T1, T2, T3, T4)\n\nT1 is ground\nT2 is ground\nT3 is ground", fontsize=16, style=filled, fillcolor=lightyellow, color=red];
2 [label="2: append3(T1, T2, T3, T4), SCOPE: 1, CLAUSE: 2\n\nT1 is ground\nT2 is ground\nT3 is ground", fontsize=16, style=filled, fillcolor=lightyellow];
3 [label="3: ','(append(T9, T10, X9), append(X9, T11, T13))\n\nT9 is ground\nT10 is ground\nT11 is ground\nX9 is free", fontsize=16, style=filled, fillcolor=lightyellow];
4 [label="4: ','(append(T9, T10, X9), append(X9, T11, T13)), SCOPE: 2, CLAUSE: 0 | ','(append(T9, T10, X9), append(X9, T11, T13)), SCOPE: 2, CLAUSE: 1\n\nT9 is ground\nT10 is ground\nT11 is ground\nX9 is free", fontsize=16, style=filled, fillcolor=lightyellow];
5 [label="5: ','(append(T9, T10, X9), append(X9, T11, T13)), SCOPE: 2, CLAUSE: 0\n\nT9 is ground\nT10 is ground\nT11 is ground\nX9 is free", fontsize=16, style=filled, fillcolor=lightyellow];
6 [label="6: ','(append(T9, T10, X9), append(X9, T11, T13)), SCOPE: 2, CLAUSE: 1\n\nT9 is ground\nT10 is ground\nT11 is ground\nX9 is free", fontsize=16, style=filled, fillcolor=lightyellow];
7 [label="A: append(T18, T11, T13)\n\nT11 is ground\nT18 is ground", fontsize=16, style=filled, fillcolor=lightyellow];
8 [label="8: \n\n", fontsize=16, style=filled, fillcolor=lightyellow];
9 [label="9: append(T18, T11, T13), SCOPE: 3, CLAUSE: 0 | append(T18, T11, T13), SCOPE: 3, CLAUSE: 1\n\nT11 is ground\nT18 is ground", fontsize=16, style=filled, fillcolor=lightyellow];
10 [label="10: append(T18, T11, T13), SCOPE: 3, CLAUSE: 0\n\nT11 is ground\nT18 is ground", fontsize=16, style=filled, fillcolor=lightyellow];
11 [label="11: append(T18, T11, T13), SCOPE: 3, CLAUSE: 1\n\nT11 is ground\nT18 is ground", fontsize=16, style=filled, fillcolor=lightyellow];
12 [label="12: true\n\n", fontsize=16, style=filled, fillcolor=lightyellow];
13 [label="13: \n\n", fontsize=16, style=filled, fillcolor=lightyellow];
14 [label="14: \n\n", fontsize=16, style=filled, fillcolor=lightyellow];
15 [label="15: append(T35, T36, T38)\n\nT35 is ground\nT36 is ground", fontsize=16, style=filled, fillcolor=lightyellow];
16 [label="16: \n\n", fontsize=16, style=filled, fillcolor=lightyellow];
17 [label="17: ','(append(T48, T49, X50), append(.(T47, X50), T11, T13))\n\nT11 is ground\nT47 is ground\nT48 is ground\nT49 is ground\nX50 is free", fontsize=16, style=filled, fillcolor=lightyellow];
18 [label="18: \n\n", fontsize=16, style=filled, fillcolor=lightyellow];
19 [label="B: append(T48, T49, X50)\n\nT48 is ground\nT49 is ground\nX50 is free", fontsize=16, style=filled, fillcolor=lightyellow];
20 [label="20: append(.(T47, T52), T11, T13)\n\nT11 is ground\nT47 is ground\nT52 is ground", fontsize=16, style=filled, fillcolor=lightyellow];
21 [label="21: append(T48, T49, X50), SCOPE: 4, CLAUSE: 0 | append(T48, T49, X50), SCOPE: 4, CLAUSE: 1\n\nT48 is ground\nT49 is ground\nX50 is free", fontsize=16, style=filled, fillcolor=lightyellow];
22 [label="22: append(T48, T49, X50), SCOPE: 4, CLAUSE: 0\n\nT48 is ground\nT49 is ground\nX50 is free", fontsize=16, style=filled, fillcolor=lightyellow];
23 [label="23: append(T48, T49, X50), SCOPE: 4, CLAUSE: 1\n\nT48 is ground\nT49 is ground\nX50 is free", fontsize=16, style=filled, fillcolor=lightyellow];
24 [label="24: true\n\n", fontsize=16, style=filled, fillcolor=lightyellow];
25 [label="25: \n\n", fontsize=16, style=filled, fillcolor=lightyellow];
26 [label="26: \n\n", fontsize=16, style=filled, fillcolor=lightyellow];
27 [label="27: append(T67, T68, X74)\n\nT67 is ground\nT68 is ground\nX74 is free", fontsize=16, style=filled, fillcolor=lightyellow];
28 [label="28: \n\n", fontsize=16, style=filled, fillcolor=lightyellow];
29 [label="CASE", fontsize=14, style = filled, fillcolor = lightcyan];
1 -> 29 [arrowhead = none ];
29 -> 2;

30 [label="ONLY EVAL with clause\nappend3(X5, X6, X7, X8) :- ','(append(X5, X6, X9), append(X9, X7, X8)).\nand substitutionT1 -> T9,\nX5 -> T9,\nT2 -> T10,\nX6 -> T10,\nT3 -> T11,\nX7 -> T11,\nT4 -> T13,\nX8 -> T13,\nT12 -> T13", fontsize=14, style = filled, fillcolor = lightblue];
2 -> 30 [arrowhead = none ];
30 -> 3;

31 [label="CASE", fontsize=14, style = filled, fillcolor = lightcyan];
3 -> 31 [arrowhead = none ];
31 -> 4;

32 [label="PARALLEL", fontsize=14, style = filled, fillcolor = violet];
4 -> 32 [arrowhead = none ];
32 -> 5;

33 [label="PARALLEL", fontsize=14, style = filled, fillcolor = violet];
4 -> 33 [arrowhead = none ];
33 -> 6;

34 [label="EVAL with clause\nappend([], X14, X14).\nand substitutionT9 -> [],\nT10 -> T18,\nX14 -> T18,\nX9 -> T18", fontsize=14, style = filled, fillcolor = lightblue];
5 -> 34 [arrowhead = none ];
34 -> 7;

35 [label="EVAL-BACKTRACK", fontsize=14, style = filled, fillcolor = lightgreen];
5 -> 35 [arrowhead = none ];
35 -> 8;

36 [label="EVAL with clause\nappend(.(X46, X47), X48, .(X46, X49)) :- append(X47, X48, X49).\nand substitutionX46 -> T47,\nX47 -> T48,\nT9 -> .(T47, T48),\nT10 -> T49,\nX48 -> T49,\nX49 -> X50,\nX9 -> .(T47, X50)", fontsize=14, style = filled, fillcolor = lightblue];
6 -> 36 [arrowhead = none ];
36 -> 17;

37 [label="EVAL-BACKTRACK", fontsize=14, style = filled, fillcolor = lightgreen];
6 -> 37 [arrowhead = none ];
37 -> 18;

38 [label="CASE", fontsize=14, style = filled, fillcolor = lightcyan];
7 -> 38 [arrowhead = none ];
38 -> 9;

39 [label="PARALLEL", fontsize=14, style = filled, fillcolor = violet];
9 -> 39 [arrowhead = none ];
39 -> 10;

40 [label="PARALLEL", fontsize=14, style = filled, fillcolor = violet];
9 -> 40 [arrowhead = none ];
40 -> 11;

41 [label="EVAL with clause\nappend([], X21, X21).\nand substitutionT18 -> [],\nT11 -> T25,\nX21 -> T25,\nT13 -> T25", fontsize=14, style = filled, fillcolor = lightblue];
10 -> 41 [arrowhead = none ];
41 -> 12;

42 [label="EVAL-BACKTRACK", fontsize=14, style = filled, fillcolor = lightgreen];
10 -> 42 [arrowhead = none ];
42 -> 13;

43 [label="EVAL with clause\nappend(.(X30, X31), X32, .(X30, X33)) :- append(X31, X32, X33).\nand substitutionX30 -> T34,\nX31 -> T35,\nT18 -> .(T34, T35),\nT11 -> T36,\nX32 -> T36,\nX33 -> T38,\nT13 -> .(T34, T38),\nT37 -> T38", fontsize=14, style = filled, fillcolor = lightblue];
11 -> 43 [arrowhead = none ];
43 -> 15;

44 [label="EVAL-BACKTRACK", fontsize=14, style = filled, fillcolor = lightgreen];
11 -> 44 [arrowhead = none ];
44 -> 16;

45 [label="SUCCESS", fontsize=14, style = filled, fillcolor = lightgreen];
12 -> 45 [arrowhead = none ];
45 -> 14;

46 [label="INSTANCE with matching:\nT18 -> T35\nT11 -> T36\nT13 -> T38", fontsize=14, style = filled, fillcolor = lightgrey];
15 -> 46 [arrowhead = none , style=dashed];
46 -> 7[style=dashed];

47 [label="SPLIT 1", fontsize=14, style = filled, fillcolor = violet];
17 -> 47 [arrowhead = none ];
47 -> 19;

48 [label="SPLIT 2\nnew knowledge:\nT48 is ground\nT49 is ground\nT52 is ground\nreplacements:X50 -> T52", fontsize=14, style = filled, fillcolor = violet];
17 -> 48 [arrowhead = none ];
48 -> 20;

49 [label="CASE", fontsize=14, style = filled, fillcolor = lightcyan];
19 -> 49 [arrowhead = none ];
49 -> 21;

50 [label="INSTANCE with matching:\nT18 -> .(T47, T52)", fontsize=14, style = filled, fillcolor = lightgrey];
20 -> 50 [arrowhead = none , style=dashed];
50 -> 7[style=dashed];

51 [label="PARALLEL", fontsize=14, style = filled, fillcolor = violet];
21 -> 51 [arrowhead = none ];
51 -> 22;

52 [label="PARALLEL", fontsize=14, style = filled, fillcolor = violet];
21 -> 52 [arrowhead = none ];
52 -> 23;

53 [label="EVAL with clause\nappend([], X59, X59).\nand substitutionT48 -> [],\nT49 -> T59,\nX59 -> T59,\nX50 -> T59", fontsize=14, style = filled, fillcolor = lightblue];
22 -> 53 [arrowhead = none ];
53 -> 24;

54 [label="EVAL-BACKTRACK", fontsize=14, style = filled, fillcolor = lightgreen];
22 -> 54 [arrowhead = none ];
54 -> 25;

55 [label="EVAL with clause\nappend(.(X70, X71), X72, .(X70, X73)) :- append(X71, X72, X73).\nand substitutionX70 -> T66,\nX71 -> T67,\nT48 -> .(T66, T67),\nT49 -> T68,\nX72 -> T68,\nX73 -> X74,\nX50 -> .(T66, X74)", fontsize=14, style = filled, fillcolor = lightblue];
23 -> 55 [arrowhead = none ];
55 -> 27;

56 [label="EVAL-BACKTRACK", fontsize=14, style = filled, fillcolor = lightgreen];
23 -> 56 [arrowhead = none ];
56 -> 28;

57 [label="SUCCESS", fontsize=14, style = filled, fillcolor = lightgreen];
24 -> 57 [arrowhead = none ];
57 -> 26;

58 [label="INSTANCE with matching:\nT48 -> T67\nT49 -> T68\nX50 -> X74", fontsize=14, style = filled, fillcolor = lightgrey];
27 -> 58 [arrowhead = none , style=dashed];
58 -> 19[style=dashed];

}

(2) Obligation:

Triples:

appendA(.(X1, X2), X3, .(X1, X4)) :- appendA(X2, X3, X4).
appendB(.(X1, X2), X3, .(X1, X4)) :- appendB(X2, X3, X4).
append3C([], X1, X2, X3) :- appendA(X1, X2, X3).
append3C(.(X1, X2), X3, X4, X5) :- appendB(X2, X3, X6).
append3C(.(X1, X2), X3, X4, X5) :- ','(appendcB(X2, X3, X6), appendA(.(X1, X6), X4, X5)).

Clauses:

appendcA([], X1, X1).
appendcA(.(X1, X2), X3, .(X1, X4)) :- appendcA(X2, X3, X4).
appendcB([], X1, X1).
appendcB(.(X1, X2), X3, .(X1, X4)) :- appendcB(X2, X3, X4).

Afs:

append3C(x1, x2, x3, x4)  =  append3C(x1, x2, x3)

(3) TriplesToPiDPProof (SOUND transformation)

We use the technique of [DT09]. With regard to the inferred argument filtering the predicates were used in the following modes:
append3C_in: (b,b,b,f)
appendA_in: (b,b,f)
appendB_in: (b,b,f)
appendcB_in: (b,b,f)
Transforming TRIPLES into the following Term Rewriting System:
Pi DP problem:
The TRS P consists of the following rules:

APPEND3C_IN_GGGA([], X1, X2, X3) → U3_GGGA(X1, X2, X3, appendA_in_gga(X1, X2, X3))
APPEND3C_IN_GGGA([], X1, X2, X3) → APPENDA_IN_GGA(X1, X2, X3)
APPENDA_IN_GGA(.(X1, X2), X3, .(X1, X4)) → U1_GGA(X1, X2, X3, X4, appendA_in_gga(X2, X3, X4))
APPENDA_IN_GGA(.(X1, X2), X3, .(X1, X4)) → APPENDA_IN_GGA(X2, X3, X4)
APPEND3C_IN_GGGA(.(X1, X2), X3, X4, X5) → U4_GGGA(X1, X2, X3, X4, X5, appendB_in_gga(X2, X3, X6))
APPEND3C_IN_GGGA(.(X1, X2), X3, X4, X5) → APPENDB_IN_GGA(X2, X3, X6)
APPENDB_IN_GGA(.(X1, X2), X3, .(X1, X4)) → U2_GGA(X1, X2, X3, X4, appendB_in_gga(X2, X3, X4))
APPENDB_IN_GGA(.(X1, X2), X3, .(X1, X4)) → APPENDB_IN_GGA(X2, X3, X4)
APPEND3C_IN_GGGA(.(X1, X2), X3, X4, X5) → U5_GGGA(X1, X2, X3, X4, X5, appendcB_in_gga(X2, X3, X6))
U5_GGGA(X1, X2, X3, X4, X5, appendcB_out_gga(X2, X3, X6)) → U6_GGGA(X1, X2, X3, X4, X5, appendA_in_gga(.(X1, X6), X4, X5))
U5_GGGA(X1, X2, X3, X4, X5, appendcB_out_gga(X2, X3, X6)) → APPENDA_IN_GGA(.(X1, X6), X4, X5)

The TRS R consists of the following rules:

appendcB_in_gga([], X1, X1) → appendcB_out_gga([], X1, X1)
appendcB_in_gga(.(X1, X2), X3, .(X1, X4)) → U9_gga(X1, X2, X3, X4, appendcB_in_gga(X2, X3, X4))
U9_gga(X1, X2, X3, X4, appendcB_out_gga(X2, X3, X4)) → appendcB_out_gga(.(X1, X2), X3, .(X1, X4))

The argument filtering Pi contains the following mapping:
[]  =  []
appendA_in_gga(x1, x2, x3)  =  appendA_in_gga(x1, x2)
.(x1, x2)  =  .(x1, x2)
appendB_in_gga(x1, x2, x3)  =  appendB_in_gga(x1, x2)
appendcB_in_gga(x1, x2, x3)  =  appendcB_in_gga(x1, x2)
appendcB_out_gga(x1, x2, x3)  =  appendcB_out_gga(x1, x2, x3)
U9_gga(x1, x2, x3, x4, x5)  =  U9_gga(x1, x2, x3, x5)
APPEND3C_IN_GGGA(x1, x2, x3, x4)  =  APPEND3C_IN_GGGA(x1, x2, x3)
U3_GGGA(x1, x2, x3, x4)  =  U3_GGGA(x1, x2, x4)
APPENDA_IN_GGA(x1, x2, x3)  =  APPENDA_IN_GGA(x1, x2)
U1_GGA(x1, x2, x3, x4, x5)  =  U1_GGA(x1, x2, x3, x5)
U4_GGGA(x1, x2, x3, x4, x5, x6)  =  U4_GGGA(x1, x2, x3, x4, x6)
APPENDB_IN_GGA(x1, x2, x3)  =  APPENDB_IN_GGA(x1, x2)
U2_GGA(x1, x2, x3, x4, x5)  =  U2_GGA(x1, x2, x3, x5)
U5_GGGA(x1, x2, x3, x4, x5, x6)  =  U5_GGGA(x1, x2, x3, x4, x6)
U6_GGGA(x1, x2, x3, x4, x5, x6)  =  U6_GGGA(x1, x2, x3, x4, x6)

We have to consider all (P,R,Pi)-chains

Infinitary Constructor Rewriting Termination of PiDP implies Termination of TRIPLES

(4) Obligation:

Pi DP problem:
The TRS P consists of the following rules:

APPEND3C_IN_GGGA([], X1, X2, X3) → U3_GGGA(X1, X2, X3, appendA_in_gga(X1, X2, X3))
APPEND3C_IN_GGGA([], X1, X2, X3) → APPENDA_IN_GGA(X1, X2, X3)
APPENDA_IN_GGA(.(X1, X2), X3, .(X1, X4)) → U1_GGA(X1, X2, X3, X4, appendA_in_gga(X2, X3, X4))
APPENDA_IN_GGA(.(X1, X2), X3, .(X1, X4)) → APPENDA_IN_GGA(X2, X3, X4)
APPEND3C_IN_GGGA(.(X1, X2), X3, X4, X5) → U4_GGGA(X1, X2, X3, X4, X5, appendB_in_gga(X2, X3, X6))
APPEND3C_IN_GGGA(.(X1, X2), X3, X4, X5) → APPENDB_IN_GGA(X2, X3, X6)
APPENDB_IN_GGA(.(X1, X2), X3, .(X1, X4)) → U2_GGA(X1, X2, X3, X4, appendB_in_gga(X2, X3, X4))
APPENDB_IN_GGA(.(X1, X2), X3, .(X1, X4)) → APPENDB_IN_GGA(X2, X3, X4)
APPEND3C_IN_GGGA(.(X1, X2), X3, X4, X5) → U5_GGGA(X1, X2, X3, X4, X5, appendcB_in_gga(X2, X3, X6))
U5_GGGA(X1, X2, X3, X4, X5, appendcB_out_gga(X2, X3, X6)) → U6_GGGA(X1, X2, X3, X4, X5, appendA_in_gga(.(X1, X6), X4, X5))
U5_GGGA(X1, X2, X3, X4, X5, appendcB_out_gga(X2, X3, X6)) → APPENDA_IN_GGA(.(X1, X6), X4, X5)

The TRS R consists of the following rules:

appendcB_in_gga([], X1, X1) → appendcB_out_gga([], X1, X1)
appendcB_in_gga(.(X1, X2), X3, .(X1, X4)) → U9_gga(X1, X2, X3, X4, appendcB_in_gga(X2, X3, X4))
U9_gga(X1, X2, X3, X4, appendcB_out_gga(X2, X3, X4)) → appendcB_out_gga(.(X1, X2), X3, .(X1, X4))

The argument filtering Pi contains the following mapping:
[]  =  []
appendA_in_gga(x1, x2, x3)  =  appendA_in_gga(x1, x2)
.(x1, x2)  =  .(x1, x2)
appendB_in_gga(x1, x2, x3)  =  appendB_in_gga(x1, x2)
appendcB_in_gga(x1, x2, x3)  =  appendcB_in_gga(x1, x2)
appendcB_out_gga(x1, x2, x3)  =  appendcB_out_gga(x1, x2, x3)
U9_gga(x1, x2, x3, x4, x5)  =  U9_gga(x1, x2, x3, x5)
APPEND3C_IN_GGGA(x1, x2, x3, x4)  =  APPEND3C_IN_GGGA(x1, x2, x3)
U3_GGGA(x1, x2, x3, x4)  =  U3_GGGA(x1, x2, x4)
APPENDA_IN_GGA(x1, x2, x3)  =  APPENDA_IN_GGA(x1, x2)
U1_GGA(x1, x2, x3, x4, x5)  =  U1_GGA(x1, x2, x3, x5)
U4_GGGA(x1, x2, x3, x4, x5, x6)  =  U4_GGGA(x1, x2, x3, x4, x6)
APPENDB_IN_GGA(x1, x2, x3)  =  APPENDB_IN_GGA(x1, x2)
U2_GGA(x1, x2, x3, x4, x5)  =  U2_GGA(x1, x2, x3, x5)
U5_GGGA(x1, x2, x3, x4, x5, x6)  =  U5_GGGA(x1, x2, x3, x4, x6)
U6_GGGA(x1, x2, x3, x4, x5, x6)  =  U6_GGGA(x1, x2, x3, x4, x6)

We have to consider all (P,R,Pi)-chains

(5) DependencyGraphProof (EQUIVALENT transformation)

The approximation of the Dependency Graph [LOPSTR] contains 2 SCCs with 9 less nodes.

(6) Complex Obligation (AND)

(7) Obligation:

Pi DP problem:
The TRS P consists of the following rules:

APPENDB_IN_GGA(.(X1, X2), X3, .(X1, X4)) → APPENDB_IN_GGA(X2, X3, X4)

The TRS R consists of the following rules:

appendcB_in_gga([], X1, X1) → appendcB_out_gga([], X1, X1)
appendcB_in_gga(.(X1, X2), X3, .(X1, X4)) → U9_gga(X1, X2, X3, X4, appendcB_in_gga(X2, X3, X4))
U9_gga(X1, X2, X3, X4, appendcB_out_gga(X2, X3, X4)) → appendcB_out_gga(.(X1, X2), X3, .(X1, X4))

The argument filtering Pi contains the following mapping:
[]  =  []
.(x1, x2)  =  .(x1, x2)
appendcB_in_gga(x1, x2, x3)  =  appendcB_in_gga(x1, x2)
appendcB_out_gga(x1, x2, x3)  =  appendcB_out_gga(x1, x2, x3)
U9_gga(x1, x2, x3, x4, x5)  =  U9_gga(x1, x2, x3, x5)
APPENDB_IN_GGA(x1, x2, x3)  =  APPENDB_IN_GGA(x1, x2)

We have to consider all (P,R,Pi)-chains

(8) UsableRulesProof (EQUIVALENT transformation)

For (infinitary) constructor rewriting [LOPSTR] we can delete all non-usable rules from R.

(9) Obligation:

Pi DP problem:
The TRS P consists of the following rules:

APPENDB_IN_GGA(.(X1, X2), X3, .(X1, X4)) → APPENDB_IN_GGA(X2, X3, X4)

R is empty.
The argument filtering Pi contains the following mapping:
.(x1, x2)  =  .(x1, x2)
APPENDB_IN_GGA(x1, x2, x3)  =  APPENDB_IN_GGA(x1, x2)

We have to consider all (P,R,Pi)-chains

(10) PiDPToQDPProof (SOUND transformation)

Transforming (infinitary) constructor rewriting Pi-DP problem [LOPSTR] into ordinary QDP problem [LPAR04] by application of Pi.

(11) Obligation:

Q DP problem:
The TRS P consists of the following rules:

APPENDB_IN_GGA(.(X1, X2), X3) → APPENDB_IN_GGA(X2, X3)

R is empty.
Q is empty.
We have to consider all (P,Q,R)-chains.

(12) QDPSizeChangeProof (EQUIVALENT transformation)

By using the subterm criterion [SUBTERM_CRITERION] together with the size-change analysis [AAECC05] we have proven that there are no infinite chains for this DP problem.

From the DPs we obtained the following set of size-change graphs:

• APPENDB_IN_GGA(.(X1, X2), X3) → APPENDB_IN_GGA(X2, X3)
  The graph contains the following edges 1 > 1, 2 >= 2

(13) YES

(14) Obligation:

Pi DP problem:
The TRS P consists of the following rules:

APPENDA_IN_GGA(.(X1, X2), X3, .(X1, X4)) → APPENDA_IN_GGA(X2, X3, X4)

The TRS R consists of the following rules:

appendcB_in_gga([], X1, X1) → appendcB_out_gga([], X1, X1)
appendcB_in_gga(.(X1, X2), X3, .(X1, X4)) → U9_gga(X1, X2, X3, X4, appendcB_in_gga(X2, X3, X4))
U9_gga(X1, X2, X3, X4, appendcB_out_gga(X2, X3, X4)) → appendcB_out_gga(.(X1, X2), X3, .(X1, X4))

The argument filtering Pi contains the following mapping:
[]  =  []
.(x1, x2)  =  .(x1, x2)
appendcB_in_gga(x1, x2, x3)  =  appendcB_in_gga(x1, x2)
appendcB_out_gga(x1, x2, x3)  =  appendcB_out_gga(x1, x2, x3)
U9_gga(x1, x2, x3, x4, x5)  =  U9_gga(x1, x2, x3, x5)
APPENDA_IN_GGA(x1, x2, x3)  =  APPENDA_IN_GGA(x1, x2)

We have to consider all (P,R,Pi)-chains

(15) UsableRulesProof (EQUIVALENT transformation)

For (infinitary) constructor rewriting [LOPSTR] we can delete all non-usable rules from R.

(16) Obligation:

Pi DP problem:
The TRS P consists of the following rules:

APPENDA_IN_GGA(.(X1, X2), X3, .(X1, X4)) → APPENDA_IN_GGA(X2, X3, X4)

R is empty.
The argument filtering Pi contains the following mapping:
.(x1, x2)  =  .(x1, x2)
APPENDA_IN_GGA(x1, x2, x3)  =  APPENDA_IN_GGA(x1, x2)

We have to consider all (P,R,Pi)-chains

(17) PiDPToQDPProof (SOUND transformation)

Transforming (infinitary) constructor rewriting Pi-DP problem [LOPSTR] into ordinary QDP problem [LPAR04] by application of Pi.

(18) Obligation:

Q DP problem:
The TRS P consists of the following rules:

APPENDA_IN_GGA(.(X1, X2), X3) → APPENDA_IN_GGA(X2, X3)

R is empty.
Q is empty.
We have to consider all (P,Q,R)-chains.

(19) QDPSizeChangeProof (EQUIVALENT transformation)

By using the subterm criterion [SUBTERM_CRITERION] together with the size-change analysis [AAECC05] we have proven that there are no infinite chains for this DP problem.

From the DPs we obtained the following set of size-change graphs:

• APPENDA_IN_GGA(.(X1, X2), X3) → APPENDA_IN_GGA(X2, X3)
  The graph contains the following edges 1 > 1, 2 >= 2

(20) YES