Termination w.r.t. Q of the following Term Rewriting System could be proven:

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

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(append, xs), nil) -> xs
app2(app2(append, nil), ys) -> ys
app2(app2(append, app2(app2(cons, x), xs)), ys) -> app2(app2(cons, x), app2(app2(append, xs), ys))
app2(app2(zip, nil), yss) -> yss
app2(app2(zip, xss), nil) -> xss
app2(app2(zip, app2(app2(cons, xs), xss)), app2(app2(cons, ys), yss)) -> app2(app2(cons, app2(app2(append, xs), ys)), app2(app2(zip, xss), yss))
app2(app2(combine, xs), nil) -> xs
app2(app2(combine, xs), app2(app2(cons, ys), yss)) -> app2(app2(combine, app2(app2(zip, xs), ys)), yss)
app2(levels, app2(app2(node, x), xs)) -> app2(app2(cons, app2(app2(cons, x), nil)), app2(app2(combine, nil), app2(app2(map, levels), xs)))

Q is empty.


↳ QTRS
  ↳ DependencyPairsProof

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

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(append, xs), nil) -> xs
app2(app2(append, nil), ys) -> ys
app2(app2(append, app2(app2(cons, x), xs)), ys) -> app2(app2(cons, x), app2(app2(append, xs), ys))
app2(app2(zip, nil), yss) -> yss
app2(app2(zip, xss), nil) -> xss
app2(app2(zip, app2(app2(cons, xs), xss)), app2(app2(cons, ys), yss)) -> app2(app2(cons, app2(app2(append, xs), ys)), app2(app2(zip, xss), yss))
app2(app2(combine, xs), nil) -> xs
app2(app2(combine, xs), app2(app2(cons, ys), yss)) -> app2(app2(combine, app2(app2(zip, xs), ys)), yss)
app2(levels, app2(app2(node, x), xs)) -> app2(app2(cons, app2(app2(cons, x), nil)), app2(app2(combine, nil), app2(app2(map, levels), 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(levels, app2(app2(node, x), xs)) -> APP2(combine, nil)
APP2(app2(map, f), app2(app2(cons, x), xs)) -> APP2(app2(cons, app2(f, x)), app2(app2(map, f), xs))
APP2(levels, app2(app2(node, x), xs)) -> APP2(map, levels)
APP2(levels, app2(app2(node, x), xs)) -> APP2(app2(cons, x), nil)
APP2(app2(zip, app2(app2(cons, xs), xss)), app2(app2(cons, ys), yss)) -> APP2(app2(cons, app2(app2(append, xs), ys)), app2(app2(zip, xss), yss))
APP2(levels, app2(app2(node, x), xs)) -> APP2(cons, x)
APP2(app2(zip, app2(app2(cons, xs), xss)), app2(app2(cons, ys), yss)) -> APP2(app2(append, xs), ys)
APP2(app2(combine, xs), app2(app2(cons, ys), yss)) -> APP2(app2(zip, xs), ys)
APP2(app2(map, f), app2(app2(cons, x), xs)) -> APP2(f, x)
APP2(app2(zip, app2(app2(cons, xs), xss)), app2(app2(cons, ys), yss)) -> APP2(zip, xss)
APP2(app2(combine, xs), app2(app2(cons, ys), yss)) -> APP2(zip, xs)
APP2(levels, app2(app2(node, x), xs)) -> APP2(app2(cons, app2(app2(cons, x), nil)), app2(app2(combine, nil), app2(app2(map, levels), xs)))
APP2(app2(zip, app2(app2(cons, xs), xss)), app2(app2(cons, ys), yss)) -> APP2(append, xs)
APP2(app2(append, app2(app2(cons, x), xs)), ys) -> APP2(append, xs)
APP2(levels, app2(app2(node, x), xs)) -> APP2(cons, app2(app2(cons, x), nil))
APP2(app2(zip, app2(app2(cons, xs), xss)), app2(app2(cons, ys), yss)) -> APP2(cons, app2(app2(append, xs), ys))
APP2(app2(zip, app2(app2(cons, xs), xss)), app2(app2(cons, ys), yss)) -> APP2(app2(zip, xss), yss)
APP2(app2(map, f), app2(app2(cons, x), xs)) -> APP2(app2(map, f), xs)
APP2(app2(combine, xs), app2(app2(cons, ys), yss)) -> APP2(app2(combine, app2(app2(zip, xs), ys)), yss)
APP2(app2(append, app2(app2(cons, x), xs)), ys) -> APP2(app2(append, xs), ys)
APP2(app2(combine, xs), app2(app2(cons, ys), yss)) -> APP2(combine, app2(app2(zip, xs), ys))
APP2(levels, app2(app2(node, x), xs)) -> APP2(app2(combine, nil), app2(app2(map, levels), xs))
APP2(app2(append, app2(app2(cons, x), xs)), ys) -> APP2(app2(cons, x), app2(app2(append, xs), ys))
APP2(levels, app2(app2(node, x), xs)) -> APP2(app2(map, levels), xs)
APP2(app2(map, f), app2(app2(cons, x), xs)) -> APP2(cons, app2(f, x))

The TRS R consists of the following rules:

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(append, xs), nil) -> xs
app2(app2(append, nil), ys) -> ys
app2(app2(append, app2(app2(cons, x), xs)), ys) -> app2(app2(cons, x), app2(app2(append, xs), ys))
app2(app2(zip, nil), yss) -> yss
app2(app2(zip, xss), nil) -> xss
app2(app2(zip, app2(app2(cons, xs), xss)), app2(app2(cons, ys), yss)) -> app2(app2(cons, app2(app2(append, xs), ys)), app2(app2(zip, xss), yss))
app2(app2(combine, xs), nil) -> xs
app2(app2(combine, xs), app2(app2(cons, ys), yss)) -> app2(app2(combine, app2(app2(zip, xs), ys)), yss)
app2(levels, app2(app2(node, x), xs)) -> app2(app2(cons, app2(app2(cons, x), nil)), app2(app2(combine, nil), app2(app2(map, levels), 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(levels, app2(app2(node, x), xs)) -> APP2(combine, nil)
APP2(app2(map, f), app2(app2(cons, x), xs)) -> APP2(app2(cons, app2(f, x)), app2(app2(map, f), xs))
APP2(levels, app2(app2(node, x), xs)) -> APP2(map, levels)
APP2(levels, app2(app2(node, x), xs)) -> APP2(app2(cons, x), nil)
APP2(app2(zip, app2(app2(cons, xs), xss)), app2(app2(cons, ys), yss)) -> APP2(app2(cons, app2(app2(append, xs), ys)), app2(app2(zip, xss), yss))
APP2(levels, app2(app2(node, x), xs)) -> APP2(cons, x)
APP2(app2(zip, app2(app2(cons, xs), xss)), app2(app2(cons, ys), yss)) -> APP2(app2(append, xs), ys)
APP2(app2(combine, xs), app2(app2(cons, ys), yss)) -> APP2(app2(zip, xs), ys)
APP2(app2(map, f), app2(app2(cons, x), xs)) -> APP2(f, x)
APP2(app2(zip, app2(app2(cons, xs), xss)), app2(app2(cons, ys), yss)) -> APP2(zip, xss)
APP2(app2(combine, xs), app2(app2(cons, ys), yss)) -> APP2(zip, xs)
APP2(levels, app2(app2(node, x), xs)) -> APP2(app2(cons, app2(app2(cons, x), nil)), app2(app2(combine, nil), app2(app2(map, levels), xs)))
APP2(app2(zip, app2(app2(cons, xs), xss)), app2(app2(cons, ys), yss)) -> APP2(append, xs)
APP2(app2(append, app2(app2(cons, x), xs)), ys) -> APP2(append, xs)
APP2(levels, app2(app2(node, x), xs)) -> APP2(cons, app2(app2(cons, x), nil))
APP2(app2(zip, app2(app2(cons, xs), xss)), app2(app2(cons, ys), yss)) -> APP2(cons, app2(app2(append, xs), ys))
APP2(app2(zip, app2(app2(cons, xs), xss)), app2(app2(cons, ys), yss)) -> APP2(app2(zip, xss), yss)
APP2(app2(map, f), app2(app2(cons, x), xs)) -> APP2(app2(map, f), xs)
APP2(app2(combine, xs), app2(app2(cons, ys), yss)) -> APP2(app2(combine, app2(app2(zip, xs), ys)), yss)
APP2(app2(append, app2(app2(cons, x), xs)), ys) -> APP2(app2(append, xs), ys)
APP2(app2(combine, xs), app2(app2(cons, ys), yss)) -> APP2(combine, app2(app2(zip, xs), ys))
APP2(levels, app2(app2(node, x), xs)) -> APP2(app2(combine, nil), app2(app2(map, levels), xs))
APP2(app2(append, app2(app2(cons, x), xs)), ys) -> APP2(app2(cons, x), app2(app2(append, xs), ys))
APP2(levels, app2(app2(node, x), xs)) -> APP2(app2(map, levels), xs)
APP2(app2(map, f), app2(app2(cons, x), xs)) -> APP2(cons, app2(f, x))

The TRS R consists of the following rules:

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(append, xs), nil) -> xs
app2(app2(append, nil), ys) -> ys
app2(app2(append, app2(app2(cons, x), xs)), ys) -> app2(app2(cons, x), app2(app2(append, xs), ys))
app2(app2(zip, nil), yss) -> yss
app2(app2(zip, xss), nil) -> xss
app2(app2(zip, app2(app2(cons, xs), xss)), app2(app2(cons, ys), yss)) -> app2(app2(cons, app2(app2(append, xs), ys)), app2(app2(zip, xss), yss))
app2(app2(combine, xs), nil) -> xs
app2(app2(combine, xs), app2(app2(cons, ys), yss)) -> app2(app2(combine, app2(app2(zip, xs), ys)), yss)
app2(levels, app2(app2(node, x), xs)) -> app2(app2(cons, app2(app2(cons, x), nil)), app2(app2(combine, nil), app2(app2(map, levels), 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 19 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(append, app2(app2(cons, x), xs)), ys) -> APP2(app2(append, xs), ys)

The TRS R consists of the following rules:

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(append, xs), nil) -> xs
app2(app2(append, nil), ys) -> ys
app2(app2(append, app2(app2(cons, x), xs)), ys) -> app2(app2(cons, x), app2(app2(append, xs), ys))
app2(app2(zip, nil), yss) -> yss
app2(app2(zip, xss), nil) -> xss
app2(app2(zip, app2(app2(cons, xs), xss)), app2(app2(cons, ys), yss)) -> app2(app2(cons, app2(app2(append, xs), ys)), app2(app2(zip, xss), yss))
app2(app2(combine, xs), nil) -> xs
app2(app2(combine, xs), app2(app2(cons, ys), yss)) -> app2(app2(combine, app2(app2(zip, xs), ys)), yss)
app2(levels, app2(app2(node, x), xs)) -> app2(app2(cons, app2(app2(cons, x), nil)), app2(app2(combine, nil), app2(app2(map, levels), 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(append, app2(app2(cons, x), xs)), ys) -> APP2(app2(append, xs), ys)
The remaining pairs can at least be oriented weakly.
none
Used ordering: Polynomial interpretation [21]:

POL(APP2(x1, x2)) = 2·x1   
POL(app2(x1, x2)) = 1 + 2·x2   
POL(append) = 0   
POL(cons) = 2   

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(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(append, xs), nil) -> xs
app2(app2(append, nil), ys) -> ys
app2(app2(append, app2(app2(cons, x), xs)), ys) -> app2(app2(cons, x), app2(app2(append, xs), ys))
app2(app2(zip, nil), yss) -> yss
app2(app2(zip, xss), nil) -> xss
app2(app2(zip, app2(app2(cons, xs), xss)), app2(app2(cons, ys), yss)) -> app2(app2(cons, app2(app2(append, xs), ys)), app2(app2(zip, xss), yss))
app2(app2(combine, xs), nil) -> xs
app2(app2(combine, xs), app2(app2(cons, ys), yss)) -> app2(app2(combine, app2(app2(zip, xs), ys)), yss)
app2(levels, app2(app2(node, x), xs)) -> app2(app2(cons, app2(app2(cons, x), nil)), app2(app2(combine, nil), app2(app2(map, levels), 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(zip, app2(app2(cons, xs), xss)), app2(app2(cons, ys), yss)) -> APP2(app2(zip, xss), yss)

The TRS R consists of the following rules:

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(append, xs), nil) -> xs
app2(app2(append, nil), ys) -> ys
app2(app2(append, app2(app2(cons, x), xs)), ys) -> app2(app2(cons, x), app2(app2(append, xs), ys))
app2(app2(zip, nil), yss) -> yss
app2(app2(zip, xss), nil) -> xss
app2(app2(zip, app2(app2(cons, xs), xss)), app2(app2(cons, ys), yss)) -> app2(app2(cons, app2(app2(append, xs), ys)), app2(app2(zip, xss), yss))
app2(app2(combine, xs), nil) -> xs
app2(app2(combine, xs), app2(app2(cons, ys), yss)) -> app2(app2(combine, app2(app2(zip, xs), ys)), yss)
app2(levels, app2(app2(node, x), xs)) -> app2(app2(cons, app2(app2(cons, x), nil)), app2(app2(combine, nil), app2(app2(map, levels), 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(zip, app2(app2(cons, xs), xss)), app2(app2(cons, ys), yss)) -> APP2(app2(zip, xss), yss)
The remaining pairs can at least be oriented weakly.
none
Used ordering: Polynomial interpretation [21]:

POL(APP2(x1, x2)) = 2·x1 + x2   
POL(app2(x1, x2)) = 2 + 2·x2   
POL(cons) = 0   
POL(zip) = 0   

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(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(append, xs), nil) -> xs
app2(app2(append, nil), ys) -> ys
app2(app2(append, app2(app2(cons, x), xs)), ys) -> app2(app2(cons, x), app2(app2(append, xs), ys))
app2(app2(zip, nil), yss) -> yss
app2(app2(zip, xss), nil) -> xss
app2(app2(zip, app2(app2(cons, xs), xss)), app2(app2(cons, ys), yss)) -> app2(app2(cons, app2(app2(append, xs), ys)), app2(app2(zip, xss), yss))
app2(app2(combine, xs), nil) -> xs
app2(app2(combine, xs), app2(app2(cons, ys), yss)) -> app2(app2(combine, app2(app2(zip, xs), ys)), yss)
app2(levels, app2(app2(node, x), xs)) -> app2(app2(cons, app2(app2(cons, x), nil)), app2(app2(combine, nil), app2(app2(map, levels), 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
            ↳ QDPOrderProof
          ↳ QDP

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

APP2(app2(combine, xs), app2(app2(cons, ys), yss)) -> APP2(app2(combine, app2(app2(zip, xs), ys)), yss)

The TRS R consists of the following rules:

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(append, xs), nil) -> xs
app2(app2(append, nil), ys) -> ys
app2(app2(append, app2(app2(cons, x), xs)), ys) -> app2(app2(cons, x), app2(app2(append, xs), ys))
app2(app2(zip, nil), yss) -> yss
app2(app2(zip, xss), nil) -> xss
app2(app2(zip, app2(app2(cons, xs), xss)), app2(app2(cons, ys), yss)) -> app2(app2(cons, app2(app2(append, xs), ys)), app2(app2(zip, xss), yss))
app2(app2(combine, xs), nil) -> xs
app2(app2(combine, xs), app2(app2(cons, ys), yss)) -> app2(app2(combine, app2(app2(zip, xs), ys)), yss)
app2(levels, app2(app2(node, x), xs)) -> app2(app2(cons, app2(app2(cons, x), nil)), app2(app2(combine, nil), app2(app2(map, levels), 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(combine, xs), app2(app2(cons, ys), yss)) -> APP2(app2(combine, app2(app2(zip, xs), ys)), yss)
The remaining pairs can at least be oriented weakly.
none
Used ordering: Polynomial interpretation [21]:

POL(APP2(x1, x2)) = x2   
POL(app2(x1, x2)) = 2·x1 + 2·x2   
POL(append) = 0   
POL(combine) = 0   
POL(cons) = 2   
POL(nil) = 0   
POL(zip) = 2   

The following usable rules [14] were oriented: none



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

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

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(append, xs), nil) -> xs
app2(app2(append, nil), ys) -> ys
app2(app2(append, app2(app2(cons, x), xs)), ys) -> app2(app2(cons, x), app2(app2(append, xs), ys))
app2(app2(zip, nil), yss) -> yss
app2(app2(zip, xss), nil) -> xss
app2(app2(zip, app2(app2(cons, xs), xss)), app2(app2(cons, ys), yss)) -> app2(app2(cons, app2(app2(append, xs), ys)), app2(app2(zip, xss), yss))
app2(app2(combine, xs), nil) -> xs
app2(app2(combine, xs), app2(app2(cons, ys), yss)) -> app2(app2(combine, app2(app2(zip, xs), ys)), yss)
app2(levels, app2(app2(node, x), xs)) -> app2(app2(cons, app2(app2(cons, x), nil)), app2(app2(combine, nil), app2(app2(map, levels), 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
            ↳ QDPOrderProof

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

APP2(app2(map, f), app2(app2(cons, x), xs)) -> APP2(f, x)
APP2(levels, app2(app2(node, x), xs)) -> APP2(app2(map, levels), xs)
APP2(app2(map, f), app2(app2(cons, x), xs)) -> APP2(app2(map, f), xs)

The TRS R consists of the following rules:

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(append, xs), nil) -> xs
app2(app2(append, nil), ys) -> ys
app2(app2(append, app2(app2(cons, x), xs)), ys) -> app2(app2(cons, x), app2(app2(append, xs), ys))
app2(app2(zip, nil), yss) -> yss
app2(app2(zip, xss), nil) -> xss
app2(app2(zip, app2(app2(cons, xs), xss)), app2(app2(cons, ys), yss)) -> app2(app2(cons, app2(app2(append, xs), ys)), app2(app2(zip, xss), yss))
app2(app2(combine, xs), nil) -> xs
app2(app2(combine, xs), app2(app2(cons, ys), yss)) -> app2(app2(combine, app2(app2(zip, xs), ys)), yss)
app2(levels, app2(app2(node, x), xs)) -> app2(app2(cons, app2(app2(cons, x), nil)), app2(app2(combine, nil), app2(app2(map, levels), 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(levels, app2(app2(node, x), xs)) -> APP2(app2(map, levels), xs)
APP2(app2(map, f), app2(app2(cons, x), xs)) -> APP2(app2(map, f), xs)
The remaining pairs can at least be oriented weakly.
none
Used ordering: Polynomial interpretation [21]:

POL(APP2(x1, x2)) = x1 + 2·x2   
POL(app2(x1, x2)) = 1 + 2·x1 + x2   
POL(cons) = 2   
POL(levels) = 1   
POL(map) = 0   
POL(node) = 0   

The following usable rules [14] were oriented: none



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

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

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(append, xs), nil) -> xs
app2(app2(append, nil), ys) -> ys
app2(app2(append, app2(app2(cons, x), xs)), ys) -> app2(app2(cons, x), app2(app2(append, xs), ys))
app2(app2(zip, nil), yss) -> yss
app2(app2(zip, xss), nil) -> xss
app2(app2(zip, app2(app2(cons, xs), xss)), app2(app2(cons, ys), yss)) -> app2(app2(cons, app2(app2(append, xs), ys)), app2(app2(zip, xss), yss))
app2(app2(combine, xs), nil) -> xs
app2(app2(combine, xs), app2(app2(cons, ys), yss)) -> app2(app2(combine, app2(app2(zip, xs), ys)), yss)
app2(levels, app2(app2(node, x), xs)) -> app2(app2(cons, app2(app2(cons, x), nil)), app2(app2(combine, nil), app2(app2(map, levels), 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.