Left Termination of the query pattern rotate_in_2(g, a) w.r.t. the given Prolog program could successfully be proven:



Prolog
  ↳ PrologToPiTRSProof

Clauses:

rotate(X, Y) :- ','(append(A, B, X), append(B, A, Y)).
append(.(X, Xs), Ys, .(X, Zs)) :- append(Xs, Ys, Zs).
append([], Ys, Ys).

Queries:

rotate(g,a).

We use the technique of [30]. With regard to the inferred argument filtering the predicates were used in the following modes:
rotate_in: (b,f)
append_in: (f,f,b) (b,b,f)
Transforming Prolog into the following Term Rewriting System:
Pi-finite rewrite system:
The TRS R consists of the following rules:

rotate_in_ga(X, Y) → U1_ga(X, Y, append_in_aag(A, B, X))
append_in_aag(.(X, Xs), Ys, .(X, Zs)) → U3_aag(X, Xs, Ys, Zs, append_in_aag(Xs, Ys, Zs))
append_in_aag([], Ys, Ys) → append_out_aag([], Ys, Ys)
U3_aag(X, Xs, Ys, Zs, append_out_aag(Xs, Ys, Zs)) → append_out_aag(.(X, Xs), Ys, .(X, Zs))
U1_ga(X, Y, append_out_aag(A, B, X)) → U2_ga(X, Y, append_in_gga(B, A, Y))
append_in_gga(.(X, Xs), Ys, .(X, Zs)) → U3_gga(X, Xs, Ys, Zs, append_in_gga(Xs, Ys, Zs))
append_in_gga([], Ys, Ys) → append_out_gga([], Ys, Ys)
U3_gga(X, Xs, Ys, Zs, append_out_gga(Xs, Ys, Zs)) → append_out_gga(.(X, Xs), Ys, .(X, Zs))
U2_ga(X, Y, append_out_gga(B, A, Y)) → rotate_out_ga(X, Y)

The argument filtering Pi contains the following mapping:
rotate_in_ga(x1, x2)  =  rotate_in_ga(x1)
U1_ga(x1, x2, x3)  =  U1_ga(x3)
append_in_aag(x1, x2, x3)  =  append_in_aag(x3)
.(x1, x2)  =  .(x1, x2)
U3_aag(x1, x2, x3, x4, x5)  =  U3_aag(x1, x5)
append_out_aag(x1, x2, x3)  =  append_out_aag(x1, x2)
U2_ga(x1, x2, x3)  =  U2_ga(x3)
append_in_gga(x1, x2, x3)  =  append_in_gga(x1, x2)
U3_gga(x1, x2, x3, x4, x5)  =  U3_gga(x1, x5)
[]  =  []
append_out_gga(x1, x2, x3)  =  append_out_gga(x3)
rotate_out_ga(x1, x2)  =  rotate_out_ga(x2)

Infinitary Constructor Rewriting Termination of PiTRS implies Termination of Prolog



↳ Prolog
  ↳ PrologToPiTRSProof
PiTRS
      ↳ DependencyPairsProof

Pi-finite rewrite system:
The TRS R consists of the following rules:

rotate_in_ga(X, Y) → U1_ga(X, Y, append_in_aag(A, B, X))
append_in_aag(.(X, Xs), Ys, .(X, Zs)) → U3_aag(X, Xs, Ys, Zs, append_in_aag(Xs, Ys, Zs))
append_in_aag([], Ys, Ys) → append_out_aag([], Ys, Ys)
U3_aag(X, Xs, Ys, Zs, append_out_aag(Xs, Ys, Zs)) → append_out_aag(.(X, Xs), Ys, .(X, Zs))
U1_ga(X, Y, append_out_aag(A, B, X)) → U2_ga(X, Y, append_in_gga(B, A, Y))
append_in_gga(.(X, Xs), Ys, .(X, Zs)) → U3_gga(X, Xs, Ys, Zs, append_in_gga(Xs, Ys, Zs))
append_in_gga([], Ys, Ys) → append_out_gga([], Ys, Ys)
U3_gga(X, Xs, Ys, Zs, append_out_gga(Xs, Ys, Zs)) → append_out_gga(.(X, Xs), Ys, .(X, Zs))
U2_ga(X, Y, append_out_gga(B, A, Y)) → rotate_out_ga(X, Y)

The argument filtering Pi contains the following mapping:
rotate_in_ga(x1, x2)  =  rotate_in_ga(x1)
U1_ga(x1, x2, x3)  =  U1_ga(x3)
append_in_aag(x1, x2, x3)  =  append_in_aag(x3)
.(x1, x2)  =  .(x1, x2)
U3_aag(x1, x2, x3, x4, x5)  =  U3_aag(x1, x5)
append_out_aag(x1, x2, x3)  =  append_out_aag(x1, x2)
U2_ga(x1, x2, x3)  =  U2_ga(x3)
append_in_gga(x1, x2, x3)  =  append_in_gga(x1, x2)
U3_gga(x1, x2, x3, x4, x5)  =  U3_gga(x1, x5)
[]  =  []
append_out_gga(x1, x2, x3)  =  append_out_gga(x3)
rotate_out_ga(x1, x2)  =  rotate_out_ga(x2)


Using Dependency Pairs [1,30] we result in the following initial DP problem:
Pi DP problem:
The TRS P consists of the following rules:

ROTATE_IN_GA(X, Y) → U1_GA(X, Y, append_in_aag(A, B, X))
ROTATE_IN_GA(X, Y) → APPEND_IN_AAG(A, B, X)
APPEND_IN_AAG(.(X, Xs), Ys, .(X, Zs)) → U3_AAG(X, Xs, Ys, Zs, append_in_aag(Xs, Ys, Zs))
APPEND_IN_AAG(.(X, Xs), Ys, .(X, Zs)) → APPEND_IN_AAG(Xs, Ys, Zs)
U1_GA(X, Y, append_out_aag(A, B, X)) → U2_GA(X, Y, append_in_gga(B, A, Y))
U1_GA(X, Y, append_out_aag(A, B, X)) → APPEND_IN_GGA(B, A, Y)
APPEND_IN_GGA(.(X, Xs), Ys, .(X, Zs)) → U3_GGA(X, Xs, Ys, Zs, append_in_gga(Xs, Ys, Zs))
APPEND_IN_GGA(.(X, Xs), Ys, .(X, Zs)) → APPEND_IN_GGA(Xs, Ys, Zs)

The TRS R consists of the following rules:

rotate_in_ga(X, Y) → U1_ga(X, Y, append_in_aag(A, B, X))
append_in_aag(.(X, Xs), Ys, .(X, Zs)) → U3_aag(X, Xs, Ys, Zs, append_in_aag(Xs, Ys, Zs))
append_in_aag([], Ys, Ys) → append_out_aag([], Ys, Ys)
U3_aag(X, Xs, Ys, Zs, append_out_aag(Xs, Ys, Zs)) → append_out_aag(.(X, Xs), Ys, .(X, Zs))
U1_ga(X, Y, append_out_aag(A, B, X)) → U2_ga(X, Y, append_in_gga(B, A, Y))
append_in_gga(.(X, Xs), Ys, .(X, Zs)) → U3_gga(X, Xs, Ys, Zs, append_in_gga(Xs, Ys, Zs))
append_in_gga([], Ys, Ys) → append_out_gga([], Ys, Ys)
U3_gga(X, Xs, Ys, Zs, append_out_gga(Xs, Ys, Zs)) → append_out_gga(.(X, Xs), Ys, .(X, Zs))
U2_ga(X, Y, append_out_gga(B, A, Y)) → rotate_out_ga(X, Y)

The argument filtering Pi contains the following mapping:
rotate_in_ga(x1, x2)  =  rotate_in_ga(x1)
U1_ga(x1, x2, x3)  =  U1_ga(x3)
append_in_aag(x1, x2, x3)  =  append_in_aag(x3)
.(x1, x2)  =  .(x1, x2)
U3_aag(x1, x2, x3, x4, x5)  =  U3_aag(x1, x5)
append_out_aag(x1, x2, x3)  =  append_out_aag(x1, x2)
U2_ga(x1, x2, x3)  =  U2_ga(x3)
append_in_gga(x1, x2, x3)  =  append_in_gga(x1, x2)
U3_gga(x1, x2, x3, x4, x5)  =  U3_gga(x1, x5)
[]  =  []
append_out_gga(x1, x2, x3)  =  append_out_gga(x3)
rotate_out_ga(x1, x2)  =  rotate_out_ga(x2)
U3_GGA(x1, x2, x3, x4, x5)  =  U3_GGA(x1, x5)
APPEND_IN_AAG(x1, x2, x3)  =  APPEND_IN_AAG(x3)
APPEND_IN_GGA(x1, x2, x3)  =  APPEND_IN_GGA(x1, x2)
ROTATE_IN_GA(x1, x2)  =  ROTATE_IN_GA(x1)
U2_GA(x1, x2, x3)  =  U2_GA(x3)
U1_GA(x1, x2, x3)  =  U1_GA(x3)
U3_AAG(x1, x2, x3, x4, x5)  =  U3_AAG(x1, x5)

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

↳ Prolog
  ↳ PrologToPiTRSProof
    ↳ PiTRS
      ↳ DependencyPairsProof
PiDP
          ↳ DependencyGraphProof

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

ROTATE_IN_GA(X, Y) → U1_GA(X, Y, append_in_aag(A, B, X))
ROTATE_IN_GA(X, Y) → APPEND_IN_AAG(A, B, X)
APPEND_IN_AAG(.(X, Xs), Ys, .(X, Zs)) → U3_AAG(X, Xs, Ys, Zs, append_in_aag(Xs, Ys, Zs))
APPEND_IN_AAG(.(X, Xs), Ys, .(X, Zs)) → APPEND_IN_AAG(Xs, Ys, Zs)
U1_GA(X, Y, append_out_aag(A, B, X)) → U2_GA(X, Y, append_in_gga(B, A, Y))
U1_GA(X, Y, append_out_aag(A, B, X)) → APPEND_IN_GGA(B, A, Y)
APPEND_IN_GGA(.(X, Xs), Ys, .(X, Zs)) → U3_GGA(X, Xs, Ys, Zs, append_in_gga(Xs, Ys, Zs))
APPEND_IN_GGA(.(X, Xs), Ys, .(X, Zs)) → APPEND_IN_GGA(Xs, Ys, Zs)

The TRS R consists of the following rules:

rotate_in_ga(X, Y) → U1_ga(X, Y, append_in_aag(A, B, X))
append_in_aag(.(X, Xs), Ys, .(X, Zs)) → U3_aag(X, Xs, Ys, Zs, append_in_aag(Xs, Ys, Zs))
append_in_aag([], Ys, Ys) → append_out_aag([], Ys, Ys)
U3_aag(X, Xs, Ys, Zs, append_out_aag(Xs, Ys, Zs)) → append_out_aag(.(X, Xs), Ys, .(X, Zs))
U1_ga(X, Y, append_out_aag(A, B, X)) → U2_ga(X, Y, append_in_gga(B, A, Y))
append_in_gga(.(X, Xs), Ys, .(X, Zs)) → U3_gga(X, Xs, Ys, Zs, append_in_gga(Xs, Ys, Zs))
append_in_gga([], Ys, Ys) → append_out_gga([], Ys, Ys)
U3_gga(X, Xs, Ys, Zs, append_out_gga(Xs, Ys, Zs)) → append_out_gga(.(X, Xs), Ys, .(X, Zs))
U2_ga(X, Y, append_out_gga(B, A, Y)) → rotate_out_ga(X, Y)

The argument filtering Pi contains the following mapping:
rotate_in_ga(x1, x2)  =  rotate_in_ga(x1)
U1_ga(x1, x2, x3)  =  U1_ga(x3)
append_in_aag(x1, x2, x3)  =  append_in_aag(x3)
.(x1, x2)  =  .(x1, x2)
U3_aag(x1, x2, x3, x4, x5)  =  U3_aag(x1, x5)
append_out_aag(x1, x2, x3)  =  append_out_aag(x1, x2)
U2_ga(x1, x2, x3)  =  U2_ga(x3)
append_in_gga(x1, x2, x3)  =  append_in_gga(x1, x2)
U3_gga(x1, x2, x3, x4, x5)  =  U3_gga(x1, x5)
[]  =  []
append_out_gga(x1, x2, x3)  =  append_out_gga(x3)
rotate_out_ga(x1, x2)  =  rotate_out_ga(x2)
U3_GGA(x1, x2, x3, x4, x5)  =  U3_GGA(x1, x5)
APPEND_IN_AAG(x1, x2, x3)  =  APPEND_IN_AAG(x3)
APPEND_IN_GGA(x1, x2, x3)  =  APPEND_IN_GGA(x1, x2)
ROTATE_IN_GA(x1, x2)  =  ROTATE_IN_GA(x1)
U2_GA(x1, x2, x3)  =  U2_GA(x3)
U1_GA(x1, x2, x3)  =  U1_GA(x3)
U3_AAG(x1, x2, x3, x4, x5)  =  U3_AAG(x1, x5)

We have to consider all (P,R,Pi)-chains
The approximation of the Dependency Graph [30] contains 2 SCCs with 6 less nodes.

↳ Prolog
  ↳ PrologToPiTRSProof
    ↳ PiTRS
      ↳ DependencyPairsProof
        ↳ PiDP
          ↳ DependencyGraphProof
            ↳ AND
PiDP
                ↳ UsableRulesProof
              ↳ PiDP

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

APPEND_IN_GGA(.(X, Xs), Ys, .(X, Zs)) → APPEND_IN_GGA(Xs, Ys, Zs)

The TRS R consists of the following rules:

rotate_in_ga(X, Y) → U1_ga(X, Y, append_in_aag(A, B, X))
append_in_aag(.(X, Xs), Ys, .(X, Zs)) → U3_aag(X, Xs, Ys, Zs, append_in_aag(Xs, Ys, Zs))
append_in_aag([], Ys, Ys) → append_out_aag([], Ys, Ys)
U3_aag(X, Xs, Ys, Zs, append_out_aag(Xs, Ys, Zs)) → append_out_aag(.(X, Xs), Ys, .(X, Zs))
U1_ga(X, Y, append_out_aag(A, B, X)) → U2_ga(X, Y, append_in_gga(B, A, Y))
append_in_gga(.(X, Xs), Ys, .(X, Zs)) → U3_gga(X, Xs, Ys, Zs, append_in_gga(Xs, Ys, Zs))
append_in_gga([], Ys, Ys) → append_out_gga([], Ys, Ys)
U3_gga(X, Xs, Ys, Zs, append_out_gga(Xs, Ys, Zs)) → append_out_gga(.(X, Xs), Ys, .(X, Zs))
U2_ga(X, Y, append_out_gga(B, A, Y)) → rotate_out_ga(X, Y)

The argument filtering Pi contains the following mapping:
rotate_in_ga(x1, x2)  =  rotate_in_ga(x1)
U1_ga(x1, x2, x3)  =  U1_ga(x3)
append_in_aag(x1, x2, x3)  =  append_in_aag(x3)
.(x1, x2)  =  .(x1, x2)
U3_aag(x1, x2, x3, x4, x5)  =  U3_aag(x1, x5)
append_out_aag(x1, x2, x3)  =  append_out_aag(x1, x2)
U2_ga(x1, x2, x3)  =  U2_ga(x3)
append_in_gga(x1, x2, x3)  =  append_in_gga(x1, x2)
U3_gga(x1, x2, x3, x4, x5)  =  U3_gga(x1, x5)
[]  =  []
append_out_gga(x1, x2, x3)  =  append_out_gga(x3)
rotate_out_ga(x1, x2)  =  rotate_out_ga(x2)
APPEND_IN_GGA(x1, x2, x3)  =  APPEND_IN_GGA(x1, x2)

We have to consider all (P,R,Pi)-chains
For (infinitary) constructor rewriting [30] we can delete all non-usable rules from R.

↳ Prolog
  ↳ PrologToPiTRSProof
    ↳ PiTRS
      ↳ DependencyPairsProof
        ↳ PiDP
          ↳ DependencyGraphProof
            ↳ AND
              ↳ PiDP
                ↳ UsableRulesProof
PiDP
                    ↳ PiDPToQDPProof
              ↳ PiDP

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

APPEND_IN_GGA(.(X, Xs), Ys, .(X, Zs)) → APPEND_IN_GGA(Xs, Ys, Zs)

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

We have to consider all (P,R,Pi)-chains
Transforming (infinitary) constructor rewriting Pi-DP problem [30] into ordinary QDP problem [15] by application of Pi.

↳ Prolog
  ↳ PrologToPiTRSProof
    ↳ PiTRS
      ↳ DependencyPairsProof
        ↳ PiDP
          ↳ DependencyGraphProof
            ↳ AND
              ↳ PiDP
                ↳ UsableRulesProof
                  ↳ PiDP
                    ↳ PiDPToQDPProof
QDP
                        ↳ QDPSizeChangeProof
              ↳ PiDP

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

APPEND_IN_GGA(.(X, Xs), Ys) → APPEND_IN_GGA(Xs, Ys)

R is empty.
Q is empty.
We have to consider all (P,Q,R)-chains.
By using the subterm criterion [20] together with the size-change analysis [32] 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:



↳ Prolog
  ↳ PrologToPiTRSProof
    ↳ PiTRS
      ↳ DependencyPairsProof
        ↳ PiDP
          ↳ DependencyGraphProof
            ↳ AND
              ↳ PiDP
PiDP
                ↳ UsableRulesProof

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

APPEND_IN_AAG(.(X, Xs), Ys, .(X, Zs)) → APPEND_IN_AAG(Xs, Ys, Zs)

The TRS R consists of the following rules:

rotate_in_ga(X, Y) → U1_ga(X, Y, append_in_aag(A, B, X))
append_in_aag(.(X, Xs), Ys, .(X, Zs)) → U3_aag(X, Xs, Ys, Zs, append_in_aag(Xs, Ys, Zs))
append_in_aag([], Ys, Ys) → append_out_aag([], Ys, Ys)
U3_aag(X, Xs, Ys, Zs, append_out_aag(Xs, Ys, Zs)) → append_out_aag(.(X, Xs), Ys, .(X, Zs))
U1_ga(X, Y, append_out_aag(A, B, X)) → U2_ga(X, Y, append_in_gga(B, A, Y))
append_in_gga(.(X, Xs), Ys, .(X, Zs)) → U3_gga(X, Xs, Ys, Zs, append_in_gga(Xs, Ys, Zs))
append_in_gga([], Ys, Ys) → append_out_gga([], Ys, Ys)
U3_gga(X, Xs, Ys, Zs, append_out_gga(Xs, Ys, Zs)) → append_out_gga(.(X, Xs), Ys, .(X, Zs))
U2_ga(X, Y, append_out_gga(B, A, Y)) → rotate_out_ga(X, Y)

The argument filtering Pi contains the following mapping:
rotate_in_ga(x1, x2)  =  rotate_in_ga(x1)
U1_ga(x1, x2, x3)  =  U1_ga(x3)
append_in_aag(x1, x2, x3)  =  append_in_aag(x3)
.(x1, x2)  =  .(x1, x2)
U3_aag(x1, x2, x3, x4, x5)  =  U3_aag(x1, x5)
append_out_aag(x1, x2, x3)  =  append_out_aag(x1, x2)
U2_ga(x1, x2, x3)  =  U2_ga(x3)
append_in_gga(x1, x2, x3)  =  append_in_gga(x1, x2)
U3_gga(x1, x2, x3, x4, x5)  =  U3_gga(x1, x5)
[]  =  []
append_out_gga(x1, x2, x3)  =  append_out_gga(x3)
rotate_out_ga(x1, x2)  =  rotate_out_ga(x2)
APPEND_IN_AAG(x1, x2, x3)  =  APPEND_IN_AAG(x3)

We have to consider all (P,R,Pi)-chains
For (infinitary) constructor rewriting [30] we can delete all non-usable rules from R.

↳ Prolog
  ↳ PrologToPiTRSProof
    ↳ PiTRS
      ↳ DependencyPairsProof
        ↳ PiDP
          ↳ DependencyGraphProof
            ↳ AND
              ↳ PiDP
              ↳ PiDP
                ↳ UsableRulesProof
PiDP
                    ↳ PiDPToQDPProof

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

APPEND_IN_AAG(.(X, Xs), Ys, .(X, Zs)) → APPEND_IN_AAG(Xs, Ys, Zs)

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

We have to consider all (P,R,Pi)-chains
Transforming (infinitary) constructor rewriting Pi-DP problem [30] into ordinary QDP problem [15] by application of Pi.

↳ Prolog
  ↳ PrologToPiTRSProof
    ↳ PiTRS
      ↳ DependencyPairsProof
        ↳ PiDP
          ↳ DependencyGraphProof
            ↳ AND
              ↳ PiDP
              ↳ PiDP
                ↳ UsableRulesProof
                  ↳ PiDP
                    ↳ PiDPToQDPProof
QDP
                        ↳ QDPSizeChangeProof

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

APPEND_IN_AAG(.(X, Zs)) → APPEND_IN_AAG(Zs)

R is empty.
Q is empty.
We have to consider all (P,Q,R)-chains.
By using the subterm criterion [20] together with the size-change analysis [32] 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: