Left Termination of the query pattern p_in_3(a, a, a) w.r.t. the given Prolog program could not be shown:

(0) Obligation:

Clauses:

p(X, Y, Z) :- ','(append(X, Y, Z), !).
append([], Y, Y).
append(.(H, Xs), Ys, .(H, Zs)) :- append(Xs, Ys, Zs).

Queries:

p(a,a,a).

(1) PrologToDTProblemTransformerProof (SOUND transformation)

Built DT problem from termination graph.

(2) Obligation:

Triples:

p3(.(T24, T28), T29, .(T24, T30)) :- p3(T28, T29, T30).
p1(T10, T11, T12) :- p3(T10, T11, T12).

Clauses:

qc3([], T15, T15).
qc3(.(T24, T28), T29, .(T24, T30)) :- qc3(T28, T29, T30).

Afs:

p1(x1, x2, x3)  =  p1

(3) TriplesToPiDPProof (SOUND transformation)

We use the technique of [LOPSTR]. With regard to the inferred argument filtering the predicates were used in the following modes:
p1_in: (f,f,f)
p3_in: (f,f,f)
Transforming TRIPLES into the following Term Rewriting System:
Pi DP problem:
The TRS P consists of the following rules:

P1_IN_AAA(T10, T11, T12) → U2_AAA(T10, T11, T12, p3_in_aaa(T10, T11, T12))
P1_IN_AAA(T10, T11, T12) → P3_IN_AAA(T10, T11, T12)
P3_IN_AAA(.(T24, T28), T29, .(T24, T30)) → U1_AAA(T24, T28, T29, T30, p3_in_aaa(T28, T29, T30))
P3_IN_AAA(.(T24, T28), T29, .(T24, T30)) → P3_IN_AAA(T28, T29, T30)

R is empty.
The argument filtering Pi contains the following mapping:
p3_in_aaa(x1, x2, x3)  =  p3_in_aaa
.(x1, x2)  =  .(x2)
P1_IN_AAA(x1, x2, x3)  =  P1_IN_AAA
U2_AAA(x1, x2, x3, x4)  =  U2_AAA(x4)
P3_IN_AAA(x1, x2, x3)  =  P3_IN_AAA
U1_AAA(x1, x2, x3, x4, x5)  =  U1_AAA(x5)

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:

P1_IN_AAA(T10, T11, T12) → U2_AAA(T10, T11, T12, p3_in_aaa(T10, T11, T12))
P1_IN_AAA(T10, T11, T12) → P3_IN_AAA(T10, T11, T12)
P3_IN_AAA(.(T24, T28), T29, .(T24, T30)) → U1_AAA(T24, T28, T29, T30, p3_in_aaa(T28, T29, T30))
P3_IN_AAA(.(T24, T28), T29, .(T24, T30)) → P3_IN_AAA(T28, T29, T30)

R is empty.
The argument filtering Pi contains the following mapping:
p3_in_aaa(x1, x2, x3)  =  p3_in_aaa
.(x1, x2)  =  .(x2)
P1_IN_AAA(x1, x2, x3)  =  P1_IN_AAA
U2_AAA(x1, x2, x3, x4)  =  U2_AAA(x4)
P3_IN_AAA(x1, x2, x3)  =  P3_IN_AAA
U1_AAA(x1, x2, x3, x4, x5)  =  U1_AAA(x5)

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

(5) DependencyGraphProof (EQUIVALENT transformation)

The approximation of the Dependency Graph [LOPSTR] contains 1 SCC with 3 less nodes.

(6) Obligation:

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

P3_IN_AAA(.(T24, T28), T29, .(T24, T30)) → P3_IN_AAA(T28, T29, T30)

R is empty.
The argument filtering Pi contains the following mapping:
.(x1, x2)  =  .(x2)
P3_IN_AAA(x1, x2, x3)  =  P3_IN_AAA

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

(7) PiDPToQDPProof (SOUND transformation)

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

(8) Obligation:

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

P3_IN_AAA → P3_IN_AAA

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

(9) NonTerminationProof (EQUIVALENT transformation)

We used the non-termination processor [FROCOS05] to show that the DP problem is infinite.
Found a loop by semiunifying a rule from P directly.

s = P3_IN_AAA evaluates to t =P3_IN_AAA

Thus s starts an infinite chain as s semiunifies with t with the following substitutions:

• Semiunifier: [ ]
• Matcher: [ ]

---

Rewriting sequence

The DP semiunifies directly so there is only one rewrite step from P3_IN_AAA to P3_IN_AAA.

(10) NO