Termination w.r.t. Q of the following Term Rewriting System could not be shown:

Q restricted rewrite system:
The TRS R consists of the following rules:

app2(p, app2(s, x)) -> x
app2(fact, 0) -> app2(s, 0)
app2(fact, app2(s, x)) -> app2(app2(*, app2(s, x)), app2(fact, app2(p, app2(s, x))))
app2(app2(*, 0), y) -> 0
app2(app2(*, app2(s, x)), y) -> app2(app2(+, app2(app2(*, x), y)), y)
app2(app2(+, x), 0) -> x
app2(app2(+, x), app2(s, y)) -> app2(s, app2(app2(+, x), y))
app2(app2(map, f), nil) -> nil
app2(app2(map, f), app2(app2(cons, x), xs)) -> app2(app2(cons, app2(f, x)), app2(app2(map, f), xs))
app2(app2(filter, f), nil) -> nil
app2(app2(filter, f), app2(app2(cons, x), xs)) -> app2(app2(app2(app2(filter2, app2(f, x)), f), x), xs)
app2(app2(app2(app2(filter2, true), f), x), xs) -> app2(app2(cons, x), app2(app2(filter, f), xs))
app2(app2(app2(app2(filter2, false), f), x), xs) -> app2(app2(filter, f), xs)

Q is empty.


↳ QTRS
  ↳ DependencyPairsProof

Q restricted rewrite system:
The TRS R consists of the following rules:

app2(p, app2(s, x)) -> x
app2(fact, 0) -> app2(s, 0)
app2(fact, app2(s, x)) -> app2(app2(*, app2(s, x)), app2(fact, app2(p, app2(s, x))))
app2(app2(*, 0), y) -> 0
app2(app2(*, app2(s, x)), y) -> app2(app2(+, app2(app2(*, x), y)), y)
app2(app2(+, x), 0) -> x
app2(app2(+, x), app2(s, y)) -> app2(s, app2(app2(+, x), y))
app2(app2(map, f), nil) -> nil
app2(app2(map, f), app2(app2(cons, x), xs)) -> app2(app2(cons, app2(f, x)), app2(app2(map, f), xs))
app2(app2(filter, f), nil) -> nil
app2(app2(filter, f), app2(app2(cons, x), xs)) -> app2(app2(app2(app2(filter2, app2(f, x)), f), x), xs)
app2(app2(app2(app2(filter2, true), f), x), xs) -> app2(app2(cons, x), app2(app2(filter, f), xs))
app2(app2(app2(app2(filter2, false), f), x), xs) -> app2(app2(filter, f), xs)

Q is empty.

Using Dependency Pairs [1,13] we result in the following initial DP problem:
Q DP problem:
The TRS P consists of the following rules:

APP2(app2(map, f), app2(app2(cons, x), xs)) -> APP2(app2(cons, app2(f, x)), app2(app2(map, f), xs))
APP2(fact, 0) -> APP2(s, 0)
APP2(app2(filter, f), app2(app2(cons, x), xs)) -> APP2(app2(app2(filter2, app2(f, x)), f), x)
APP2(app2(filter, f), app2(app2(cons, x), xs)) -> APP2(app2(app2(app2(filter2, app2(f, x)), f), x), xs)
APP2(app2(app2(app2(filter2, true), f), x), xs) -> APP2(app2(cons, x), app2(app2(filter, f), xs))
APP2(app2(*, app2(s, x)), y) -> APP2(app2(*, x), y)
APP2(app2(*, app2(s, x)), y) -> APP2(app2(+, app2(app2(*, x), y)), y)
APP2(app2(map, f), app2(app2(cons, x), xs)) -> APP2(f, x)
APP2(app2(filter, f), app2(app2(cons, x), xs)) -> APP2(filter2, app2(f, x))
APP2(fact, app2(s, x)) -> APP2(p, app2(s, x))
APP2(app2(app2(app2(filter2, true), f), x), xs) -> APP2(app2(filter, f), xs)
APP2(app2(*, app2(s, x)), y) -> APP2(+, app2(app2(*, x), y))
APP2(app2(+, x), app2(s, y)) -> APP2(app2(+, x), y)
APP2(fact, app2(s, x)) -> APP2(*, app2(s, x))
APP2(app2(filter, f), app2(app2(cons, x), xs)) -> APP2(app2(filter2, app2(f, x)), f)
APP2(app2(app2(app2(filter2, false), f), x), xs) -> APP2(filter, f)
APP2(fact, app2(s, x)) -> APP2(fact, app2(p, app2(s, x)))
APP2(app2(map, f), app2(app2(cons, x), xs)) -> APP2(app2(map, f), xs)
APP2(app2(filter, f), app2(app2(cons, x), xs)) -> APP2(f, x)
APP2(app2(*, app2(s, x)), y) -> APP2(*, x)
APP2(app2(app2(app2(filter2, true), f), x), xs) -> APP2(filter, f)
APP2(fact, app2(s, x)) -> APP2(app2(*, app2(s, x)), app2(fact, app2(p, app2(s, x))))
APP2(app2(app2(app2(filter2, true), f), x), xs) -> APP2(cons, x)
APP2(app2(app2(app2(filter2, false), f), x), xs) -> APP2(app2(filter, f), xs)
APP2(app2(map, f), app2(app2(cons, x), xs)) -> APP2(cons, app2(f, x))
APP2(app2(+, x), app2(s, y)) -> APP2(s, app2(app2(+, x), y))

The TRS R consists of the following rules:

app2(p, app2(s, x)) -> x
app2(fact, 0) -> app2(s, 0)
app2(fact, app2(s, x)) -> app2(app2(*, app2(s, x)), app2(fact, app2(p, app2(s, x))))
app2(app2(*, 0), y) -> 0
app2(app2(*, app2(s, x)), y) -> app2(app2(+, app2(app2(*, x), y)), y)
app2(app2(+, x), 0) -> x
app2(app2(+, x), app2(s, y)) -> app2(s, app2(app2(+, x), y))
app2(app2(map, f), nil) -> nil
app2(app2(map, f), app2(app2(cons, x), xs)) -> app2(app2(cons, app2(f, x)), app2(app2(map, f), xs))
app2(app2(filter, f), nil) -> nil
app2(app2(filter, f), app2(app2(cons, x), xs)) -> app2(app2(app2(app2(filter2, app2(f, x)), f), x), xs)
app2(app2(app2(app2(filter2, true), f), x), xs) -> app2(app2(cons, x), app2(app2(filter, f), xs))
app2(app2(app2(app2(filter2, false), f), x), xs) -> app2(app2(filter, f), xs)

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

↳ QTRS
  ↳ DependencyPairsProof
    ↳ QDP
      ↳ DependencyGraphProof

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

APP2(app2(map, f), app2(app2(cons, x), xs)) -> APP2(app2(cons, app2(f, x)), app2(app2(map, f), xs))
APP2(fact, 0) -> APP2(s, 0)
APP2(app2(filter, f), app2(app2(cons, x), xs)) -> APP2(app2(app2(filter2, app2(f, x)), f), x)
APP2(app2(filter, f), app2(app2(cons, x), xs)) -> APP2(app2(app2(app2(filter2, app2(f, x)), f), x), xs)
APP2(app2(app2(app2(filter2, true), f), x), xs) -> APP2(app2(cons, x), app2(app2(filter, f), xs))
APP2(app2(*, app2(s, x)), y) -> APP2(app2(*, x), y)
APP2(app2(*, app2(s, x)), y) -> APP2(app2(+, app2(app2(*, x), y)), y)
APP2(app2(map, f), app2(app2(cons, x), xs)) -> APP2(f, x)
APP2(app2(filter, f), app2(app2(cons, x), xs)) -> APP2(filter2, app2(f, x))
APP2(fact, app2(s, x)) -> APP2(p, app2(s, x))
APP2(app2(app2(app2(filter2, true), f), x), xs) -> APP2(app2(filter, f), xs)
APP2(app2(*, app2(s, x)), y) -> APP2(+, app2(app2(*, x), y))
APP2(app2(+, x), app2(s, y)) -> APP2(app2(+, x), y)
APP2(fact, app2(s, x)) -> APP2(*, app2(s, x))
APP2(app2(filter, f), app2(app2(cons, x), xs)) -> APP2(app2(filter2, app2(f, x)), f)
APP2(app2(app2(app2(filter2, false), f), x), xs) -> APP2(filter, f)
APP2(fact, app2(s, x)) -> APP2(fact, app2(p, app2(s, x)))
APP2(app2(map, f), app2(app2(cons, x), xs)) -> APP2(app2(map, f), xs)
APP2(app2(filter, f), app2(app2(cons, x), xs)) -> APP2(f, x)
APP2(app2(*, app2(s, x)), y) -> APP2(*, x)
APP2(app2(app2(app2(filter2, true), f), x), xs) -> APP2(filter, f)
APP2(fact, app2(s, x)) -> APP2(app2(*, app2(s, x)), app2(fact, app2(p, app2(s, x))))
APP2(app2(app2(app2(filter2, true), f), x), xs) -> APP2(cons, x)
APP2(app2(app2(app2(filter2, false), f), x), xs) -> APP2(app2(filter, f), xs)
APP2(app2(map, f), app2(app2(cons, x), xs)) -> APP2(cons, app2(f, x))
APP2(app2(+, x), app2(s, y)) -> APP2(s, app2(app2(+, x), y))

The TRS R consists of the following rules:

app2(p, app2(s, x)) -> x
app2(fact, 0) -> app2(s, 0)
app2(fact, app2(s, x)) -> app2(app2(*, app2(s, x)), app2(fact, app2(p, app2(s, x))))
app2(app2(*, 0), y) -> 0
app2(app2(*, app2(s, x)), y) -> app2(app2(+, app2(app2(*, x), y)), y)
app2(app2(+, x), 0) -> x
app2(app2(+, x), app2(s, y)) -> app2(s, app2(app2(+, x), y))
app2(app2(map, f), nil) -> nil
app2(app2(map, f), app2(app2(cons, x), xs)) -> app2(app2(cons, app2(f, x)), app2(app2(map, f), xs))
app2(app2(filter, f), nil) -> nil
app2(app2(filter, f), app2(app2(cons, x), xs)) -> app2(app2(app2(app2(filter2, app2(f, x)), f), x), xs)
app2(app2(app2(app2(filter2, true), f), x), xs) -> app2(app2(cons, x), app2(app2(filter, f), xs))
app2(app2(app2(app2(filter2, false), f), x), xs) -> app2(app2(filter, f), xs)

Q is empty.
We have to consider all minimal (P,Q,R)-chains.
The approximation of the Dependency Graph [13,14,18] contains 4 SCCs with 17 less nodes.

↳ QTRS
  ↳ DependencyPairsProof
    ↳ QDP
      ↳ DependencyGraphProof
        ↳ AND
          ↳ QDP
            ↳ QDPOrderProof
          ↳ QDP
          ↳ QDP
          ↳ QDP

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

APP2(app2(+, x), app2(s, y)) -> APP2(app2(+, x), y)

The TRS R consists of the following rules:

app2(p, app2(s, x)) -> x
app2(fact, 0) -> app2(s, 0)
app2(fact, app2(s, x)) -> app2(app2(*, app2(s, x)), app2(fact, app2(p, app2(s, x))))
app2(app2(*, 0), y) -> 0
app2(app2(*, app2(s, x)), y) -> app2(app2(+, app2(app2(*, x), y)), y)
app2(app2(+, x), 0) -> x
app2(app2(+, x), app2(s, y)) -> app2(s, app2(app2(+, x), y))
app2(app2(map, f), nil) -> nil
app2(app2(map, f), app2(app2(cons, x), xs)) -> app2(app2(cons, app2(f, x)), app2(app2(map, f), xs))
app2(app2(filter, f), nil) -> nil
app2(app2(filter, f), app2(app2(cons, x), xs)) -> app2(app2(app2(app2(filter2, app2(f, x)), f), x), xs)
app2(app2(app2(app2(filter2, true), f), x), xs) -> app2(app2(cons, x), app2(app2(filter, f), xs))
app2(app2(app2(app2(filter2, false), f), x), xs) -> app2(app2(filter, f), xs)

Q is empty.
We have to consider all minimal (P,Q,R)-chains.
We use the reduction pair processor [13].


The following pairs can be oriented strictly and are deleted.


APP2(app2(+, x), app2(s, y)) -> APP2(app2(+, x), y)
The remaining pairs can at least be oriented weakly.
none
Used ordering: Polynomial Order [17,21] with Interpretation:

POL( + ) = max{0, -1}


POL( s ) = max{0, -1}


POL( APP2(x1, x2) ) = x1 + x2 + 1


POL( app2(x1, x2) ) = x2 + 1



The following usable rules [14] were oriented: none



↳ QTRS
  ↳ DependencyPairsProof
    ↳ QDP
      ↳ DependencyGraphProof
        ↳ AND
          ↳ QDP
            ↳ QDPOrderProof
              ↳ QDP
                ↳ PisEmptyProof
          ↳ QDP
          ↳ QDP
          ↳ QDP

Q DP problem:
P is empty.
The TRS R consists of the following rules:

app2(p, app2(s, x)) -> x
app2(fact, 0) -> app2(s, 0)
app2(fact, app2(s, x)) -> app2(app2(*, app2(s, x)), app2(fact, app2(p, app2(s, x))))
app2(app2(*, 0), y) -> 0
app2(app2(*, app2(s, x)), y) -> app2(app2(+, app2(app2(*, x), y)), y)
app2(app2(+, x), 0) -> x
app2(app2(+, x), app2(s, y)) -> app2(s, app2(app2(+, x), y))
app2(app2(map, f), nil) -> nil
app2(app2(map, f), app2(app2(cons, x), xs)) -> app2(app2(cons, app2(f, x)), app2(app2(map, f), xs))
app2(app2(filter, f), nil) -> nil
app2(app2(filter, f), app2(app2(cons, x), xs)) -> app2(app2(app2(app2(filter2, app2(f, x)), f), x), xs)
app2(app2(app2(app2(filter2, true), f), x), xs) -> app2(app2(cons, x), app2(app2(filter, f), xs))
app2(app2(app2(app2(filter2, false), f), x), xs) -> app2(app2(filter, f), xs)

Q is empty.
We have to consider all minimal (P,Q,R)-chains.
The TRS P is empty. Hence, there is no (P,Q,R) chain.

↳ QTRS
  ↳ DependencyPairsProof
    ↳ QDP
      ↳ DependencyGraphProof
        ↳ AND
          ↳ QDP
          ↳ QDP
            ↳ QDPOrderProof
          ↳ QDP
          ↳ QDP

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

APP2(app2(*, app2(s, x)), y) -> APP2(app2(*, x), y)

The TRS R consists of the following rules:

app2(p, app2(s, x)) -> x
app2(fact, 0) -> app2(s, 0)
app2(fact, app2(s, x)) -> app2(app2(*, app2(s, x)), app2(fact, app2(p, app2(s, x))))
app2(app2(*, 0), y) -> 0
app2(app2(*, app2(s, x)), y) -> app2(app2(+, app2(app2(*, x), y)), y)
app2(app2(+, x), 0) -> x
app2(app2(+, x), app2(s, y)) -> app2(s, app2(app2(+, x), y))
app2(app2(map, f), nil) -> nil
app2(app2(map, f), app2(app2(cons, x), xs)) -> app2(app2(cons, app2(f, x)), app2(app2(map, f), xs))
app2(app2(filter, f), nil) -> nil
app2(app2(filter, f), app2(app2(cons, x), xs)) -> app2(app2(app2(app2(filter2, app2(f, x)), f), x), xs)
app2(app2(app2(app2(filter2, true), f), x), xs) -> app2(app2(cons, x), app2(app2(filter, f), xs))
app2(app2(app2(app2(filter2, false), f), x), xs) -> app2(app2(filter, f), xs)

Q is empty.
We have to consider all minimal (P,Q,R)-chains.
We use the reduction pair processor [13].


The following pairs can be oriented strictly and are deleted.


APP2(app2(*, app2(s, x)), y) -> APP2(app2(*, x), y)
The remaining pairs can at least be oriented weakly.
none
Used ordering: Polynomial Order [17,21] with Interpretation:

POL( s ) = 1


POL( APP2(x1, x2) ) = x1


POL( * ) = 1


POL( app2(x1, x2) ) = x1 + x2 + 1



The following usable rules [14] were oriented: none



↳ QTRS
  ↳ DependencyPairsProof
    ↳ QDP
      ↳ DependencyGraphProof
        ↳ AND
          ↳ QDP
          ↳ QDP
            ↳ QDPOrderProof
              ↳ QDP
                ↳ PisEmptyProof
          ↳ QDP
          ↳ QDP

Q DP problem:
P is empty.
The TRS R consists of the following rules:

app2(p, app2(s, x)) -> x
app2(fact, 0) -> app2(s, 0)
app2(fact, app2(s, x)) -> app2(app2(*, app2(s, x)), app2(fact, app2(p, app2(s, x))))
app2(app2(*, 0), y) -> 0
app2(app2(*, app2(s, x)), y) -> app2(app2(+, app2(app2(*, x), y)), y)
app2(app2(+, x), 0) -> x
app2(app2(+, x), app2(s, y)) -> app2(s, app2(app2(+, x), y))
app2(app2(map, f), nil) -> nil
app2(app2(map, f), app2(app2(cons, x), xs)) -> app2(app2(cons, app2(f, x)), app2(app2(map, f), xs))
app2(app2(filter, f), nil) -> nil
app2(app2(filter, f), app2(app2(cons, x), xs)) -> app2(app2(app2(app2(filter2, app2(f, x)), f), x), xs)
app2(app2(app2(app2(filter2, true), f), x), xs) -> app2(app2(cons, x), app2(app2(filter, f), xs))
app2(app2(app2(app2(filter2, false), f), x), xs) -> app2(app2(filter, f), xs)

Q is empty.
We have to consider all minimal (P,Q,R)-chains.
The TRS P is empty. Hence, there is no (P,Q,R) chain.

↳ QTRS
  ↳ DependencyPairsProof
    ↳ QDP
      ↳ DependencyGraphProof
        ↳ AND
          ↳ QDP
          ↳ QDP
          ↳ QDP
          ↳ QDP

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

APP2(fact, app2(s, x)) -> APP2(fact, app2(p, app2(s, x)))

The TRS R consists of the following rules:

app2(p, app2(s, x)) -> x
app2(fact, 0) -> app2(s, 0)
app2(fact, app2(s, x)) -> app2(app2(*, app2(s, x)), app2(fact, app2(p, app2(s, x))))
app2(app2(*, 0), y) -> 0
app2(app2(*, app2(s, x)), y) -> app2(app2(+, app2(app2(*, x), y)), y)
app2(app2(+, x), 0) -> x
app2(app2(+, x), app2(s, y)) -> app2(s, app2(app2(+, x), y))
app2(app2(map, f), nil) -> nil
app2(app2(map, f), app2(app2(cons, x), xs)) -> app2(app2(cons, app2(f, x)), app2(app2(map, f), xs))
app2(app2(filter, f), nil) -> nil
app2(app2(filter, f), app2(app2(cons, x), xs)) -> app2(app2(app2(app2(filter2, app2(f, x)), f), x), xs)
app2(app2(app2(app2(filter2, true), f), x), xs) -> app2(app2(cons, x), app2(app2(filter, f), xs))
app2(app2(app2(app2(filter2, false), f), x), xs) -> app2(app2(filter, f), xs)

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

↳ QTRS
  ↳ DependencyPairsProof
    ↳ QDP
      ↳ DependencyGraphProof
        ↳ AND
          ↳ QDP
          ↳ QDP
          ↳ QDP
          ↳ QDP
            ↳ QDPOrderProof

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

APP2(app2(app2(app2(filter2, true), f), x), xs) -> APP2(app2(filter, f), xs)
APP2(app2(map, f), app2(app2(cons, x), xs)) -> APP2(f, x)
APP2(app2(filter, f), app2(app2(cons, x), xs)) -> APP2(app2(app2(app2(filter2, app2(f, x)), f), x), xs)
APP2(app2(app2(app2(filter2, false), f), x), xs) -> APP2(app2(filter, f), xs)
APP2(app2(filter, f), app2(app2(cons, x), xs)) -> APP2(f, x)
APP2(app2(map, f), app2(app2(cons, x), xs)) -> APP2(app2(map, f), xs)

The TRS R consists of the following rules:

app2(p, app2(s, x)) -> x
app2(fact, 0) -> app2(s, 0)
app2(fact, app2(s, x)) -> app2(app2(*, app2(s, x)), app2(fact, app2(p, app2(s, x))))
app2(app2(*, 0), y) -> 0
app2(app2(*, app2(s, x)), y) -> app2(app2(+, app2(app2(*, x), y)), y)
app2(app2(+, x), 0) -> x
app2(app2(+, x), app2(s, y)) -> app2(s, app2(app2(+, x), y))
app2(app2(map, f), nil) -> nil
app2(app2(map, f), app2(app2(cons, x), xs)) -> app2(app2(cons, app2(f, x)), app2(app2(map, f), xs))
app2(app2(filter, f), nil) -> nil
app2(app2(filter, f), app2(app2(cons, x), xs)) -> app2(app2(app2(app2(filter2, app2(f, x)), f), x), xs)
app2(app2(app2(app2(filter2, true), f), x), xs) -> app2(app2(cons, x), app2(app2(filter, f), xs))
app2(app2(app2(app2(filter2, false), f), x), xs) -> app2(app2(filter, f), xs)

Q is empty.
We have to consider all minimal (P,Q,R)-chains.
We use the reduction pair processor [13].


The following pairs can be oriented strictly and are deleted.


APP2(app2(map, f), app2(app2(cons, x), xs)) -> APP2(f, x)
APP2(app2(filter, f), app2(app2(cons, x), xs)) -> APP2(app2(app2(app2(filter2, app2(f, x)), f), x), xs)
APP2(app2(filter, f), app2(app2(cons, x), xs)) -> APP2(f, x)
APP2(app2(map, f), app2(app2(cons, x), xs)) -> APP2(app2(map, f), xs)
The remaining pairs can at least be oriented weakly.

APP2(app2(app2(app2(filter2, true), f), x), xs) -> APP2(app2(filter, f), xs)
APP2(app2(app2(app2(filter2, false), f), x), xs) -> APP2(app2(filter, f), xs)
Used ordering: Polynomial Order [17,21] with Interpretation:

POL( map ) = 0


POL( fact ) = 1


POL( 0 ) = 1


POL( APP2(x1, x2) ) = x2


POL( s ) = 0


POL( p ) = 1


POL( nil ) = max{0, -1}


POL( * ) = 1


POL( cons ) = 1


POL( filter ) = max{0, -1}


POL( true ) = max{0, -1}


POL( false ) = 1


POL( app2(x1, x2) ) = x1 + x2


POL( + ) = 0


POL( filter2 ) = 1



The following usable rules [14] were oriented: none



↳ QTRS
  ↳ DependencyPairsProof
    ↳ QDP
      ↳ DependencyGraphProof
        ↳ AND
          ↳ QDP
          ↳ QDP
          ↳ QDP
          ↳ QDP
            ↳ QDPOrderProof
              ↳ QDP
                ↳ DependencyGraphProof

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

APP2(app2(app2(app2(filter2, true), f), x), xs) -> APP2(app2(filter, f), xs)
APP2(app2(app2(app2(filter2, false), f), x), xs) -> APP2(app2(filter, f), xs)

The TRS R consists of the following rules:

app2(p, app2(s, x)) -> x
app2(fact, 0) -> app2(s, 0)
app2(fact, app2(s, x)) -> app2(app2(*, app2(s, x)), app2(fact, app2(p, app2(s, x))))
app2(app2(*, 0), y) -> 0
app2(app2(*, app2(s, x)), y) -> app2(app2(+, app2(app2(*, x), y)), y)
app2(app2(+, x), 0) -> x
app2(app2(+, x), app2(s, y)) -> app2(s, app2(app2(+, x), y))
app2(app2(map, f), nil) -> nil
app2(app2(map, f), app2(app2(cons, x), xs)) -> app2(app2(cons, app2(f, x)), app2(app2(map, f), xs))
app2(app2(filter, f), nil) -> nil
app2(app2(filter, f), app2(app2(cons, x), xs)) -> app2(app2(app2(app2(filter2, app2(f, x)), f), x), xs)
app2(app2(app2(app2(filter2, true), f), x), xs) -> app2(app2(cons, x), app2(app2(filter, f), xs))
app2(app2(app2(app2(filter2, false), f), x), xs) -> app2(app2(filter, f), xs)

Q is empty.
We have to consider all minimal (P,Q,R)-chains.
The approximation of the Dependency Graph [13,14,18] contains 0 SCCs with 2 less nodes.