Termination w.r.t. Q of the given QTRS could be proven:

0 QTRS
↳1 DependencyPairsProof (⇔)
↳2 QDP
↳3 DependencyGraphProof (⇔)
↳4 AND
  ↳5 QDP
    ↳6 UsableRulesProof (⇔)
    ↳7 QDP
    ↳8 QDPSizeChangeProof (⇔)
    ↳9 TRUE
  ↳10 QDP
    ↳11 UsableRulesReductionPairsProof (⇔)
    ↳12 QDP
    ↳13 QDPOrderProof (⇔)
    ↳14 QDP
    ↳15 DependencyGraphProof (⇔)
    ↳16 QDP
    ↳17 QDPOrderProof (⇔)
    ↳18 QDP
    ↳19 PisEmptyProof (⇔)
    ↳20 TRUE

(0) Obligation:

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

f(s(x)) → f(id_inc(c(x, x)))
f(c(s(x), y)) → g(c(x, y))
g(c(s(x), y)) → g(c(y, x))
g(c(x, s(y))) → g(c(y, x))
g(c(x, x)) → f(x)
id_inc(c(x, y)) → c(id_inc(x), id_inc(y))
id_inc(s(x)) → s(id_inc(x))
id_inc(0) → 0
id_inc(0) → s(0)

Q is empty.

(1) DependencyPairsProof (EQUIVALENT transformation)

Using Dependency Pairs [AG00,LPAR04] we result in the following initial DP problem.

(2) Obligation:

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

F(s(x)) → F(id_inc(c(x, x)))
F(s(x)) → ID_INC(c(x, x))
F(c(s(x), y)) → G(c(x, y))
G(c(s(x), y)) → G(c(y, x))
G(c(x, s(y))) → G(c(y, x))
G(c(x, x)) → F(x)
ID_INC(c(x, y)) → ID_INC(x)
ID_INC(c(x, y)) → ID_INC(y)
ID_INC(s(x)) → ID_INC(x)

The TRS R consists of the following rules:

f(s(x)) → f(id_inc(c(x, x)))
f(c(s(x), y)) → g(c(x, y))
g(c(s(x), y)) → g(c(y, x))
g(c(x, s(y))) → g(c(y, x))
g(c(x, x)) → f(x)
id_inc(c(x, y)) → c(id_inc(x), id_inc(y))
id_inc(s(x)) → s(id_inc(x))
id_inc(0) → 0
id_inc(0) → s(0)

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

(3) DependencyGraphProof (EQUIVALENT transformation)

The approximation of the Dependency Graph [LPAR04,FROCOS05,EDGSTAR] contains 2 SCCs with 1 less node.

(4) Complex Obligation (AND)

(5) Obligation:

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

ID_INC(c(x, y)) → ID_INC(y)
ID_INC(c(x, y)) → ID_INC(x)
ID_INC(s(x)) → ID_INC(x)

The TRS R consists of the following rules:

f(s(x)) → f(id_inc(c(x, x)))
f(c(s(x), y)) → g(c(x, y))
g(c(s(x), y)) → g(c(y, x))
g(c(x, s(y))) → g(c(y, x))
g(c(x, x)) → f(x)
id_inc(c(x, y)) → c(id_inc(x), id_inc(y))
id_inc(s(x)) → s(id_inc(x))
id_inc(0) → 0
id_inc(0) → s(0)

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

(6) UsableRulesProof (EQUIVALENT transformation)

We can use the usable rules and reduction pair processor [LPAR04] with the Ce-compatible extension of the polynomial order that maps every function symbol to the sum of its arguments. Then, we can delete all non-usable rules [FROCOS05] from R.

(7) Obligation:

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

ID_INC(c(x, y)) → ID_INC(y)
ID_INC(c(x, y)) → ID_INC(x)
ID_INC(s(x)) → ID_INC(x)

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

(8) 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:

  • ID_INC(c(x, y)) → ID_INC(y)
    The graph contains the following edges 1 > 1

  • ID_INC(c(x, y)) → ID_INC(x)
    The graph contains the following edges 1 > 1

  • ID_INC(s(x)) → ID_INC(x)
    The graph contains the following edges 1 > 1

(9) TRUE

(10) Obligation:

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

F(c(s(x), y)) → G(c(x, y))
G(c(s(x), y)) → G(c(y, x))
G(c(x, s(y))) → G(c(y, x))
G(c(x, x)) → F(x)
F(s(x)) → F(id_inc(c(x, x)))

The TRS R consists of the following rules:

f(s(x)) → f(id_inc(c(x, x)))
f(c(s(x), y)) → g(c(x, y))
g(c(s(x), y)) → g(c(y, x))
g(c(x, s(y))) → g(c(y, x))
g(c(x, x)) → f(x)
id_inc(c(x, y)) → c(id_inc(x), id_inc(y))
id_inc(s(x)) → s(id_inc(x))
id_inc(0) → 0
id_inc(0) → s(0)

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

(11) UsableRulesReductionPairsProof (EQUIVALENT transformation)

By using the usable rules with reduction pair processor [LPAR04] with a polynomial ordering [POLO], all dependency pairs and the corresponding usable rules [FROCOS05] can be oriented non-strictly. All non-usable rules are removed, and those dependency pairs and usable rules that have been oriented strictly or contain non-usable symbols in their left-hand side are removed as well.

No dependency pairs are removed.

No rules are removed from R.

Used ordering: POLO with Polynomial interpretation [POLO]:

POL(0) = 0   
POL(F(x1)) = 1 + 2·x1   
POL(G(x1)) = 1 + 2·x1   
POL(c(x1, x2)) = x1 + x2   
POL(id_inc(x1)) = x1   
POL(s(x1)) = 2·x1   

(12) Obligation:

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

F(c(s(x), y)) → G(c(x, y))
G(c(s(x), y)) → G(c(y, x))
G(c(x, s(y))) → G(c(y, x))
G(c(x, x)) → F(x)
F(s(x)) → F(id_inc(c(x, x)))

The TRS R consists of the following rules:

id_inc(c(x, y)) → c(id_inc(x), id_inc(y))
id_inc(s(x)) → s(id_inc(x))
id_inc(0) → 0
id_inc(0) → s(0)

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

(13) QDPOrderProof (EQUIVALENT transformation)

We use the reduction pair processor [LPAR04].


The following pairs can be oriented strictly and are deleted.


F(c(s(x), y)) → G(c(x, y))
G(c(s(x), y)) → G(c(y, x))
G(c(x, s(y))) → G(c(y, x))
The remaining pairs can at least be oriented weakly.
Used ordering: Polynomial interpretation [POLO,RATPOLO]:

POL(F(x1)) = 1/2 + (1/2)x1   
POL(c(x1, x2)) = (1/2)x1 + (1/2)x2   
POL(s(x1)) = 1/4 + (9/4)x1   
POL(G(x1)) = 1/2 + (1/2)x1   
POL(id_inc(x1)) = 1/4 + (9/4)x1   
POL(0) = 1/4   
The value of delta used in the strict ordering is 1/16.
The following usable rules [FROCOS05] were oriented:

id_inc(c(x, y)) → c(id_inc(x), id_inc(y))
id_inc(s(x)) → s(id_inc(x))
id_inc(0) → 0
id_inc(0) → s(0)

(14) Obligation:

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

G(c(x, x)) → F(x)
F(s(x)) → F(id_inc(c(x, x)))

The TRS R consists of the following rules:

id_inc(c(x, y)) → c(id_inc(x), id_inc(y))
id_inc(s(x)) → s(id_inc(x))
id_inc(0) → 0
id_inc(0) → s(0)

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

(15) DependencyGraphProof (EQUIVALENT transformation)

The approximation of the Dependency Graph [LPAR04,FROCOS05,EDGSTAR] contains 1 SCC with 1 less node.

(16) Obligation:

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

F(s(x)) → F(id_inc(c(x, x)))

The TRS R consists of the following rules:

id_inc(c(x, y)) → c(id_inc(x), id_inc(y))
id_inc(s(x)) → s(id_inc(x))
id_inc(0) → 0
id_inc(0) → s(0)

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

(17) QDPOrderProof (EQUIVALENT transformation)

We use the reduction pair processor [LPAR04].


The following pairs can be oriented strictly and are deleted.


F(s(x)) → F(id_inc(c(x, x)))
The remaining pairs can at least be oriented weakly.
Used ordering: Polynomial interpretation [POLO]:

POL(0) = 0   
POL(F(x1)) = x1   
POL(c(x1, x2)) = 0   
POL(id_inc(x1)) = x1   
POL(s(x1)) = 1   

The following usable rules [FROCOS05] were oriented:

id_inc(c(x, y)) → c(id_inc(x), id_inc(y))
id_inc(s(x)) → s(id_inc(x))

(18) Obligation:

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

id_inc(c(x, y)) → c(id_inc(x), id_inc(y))
id_inc(s(x)) → s(id_inc(x))
id_inc(0) → 0
id_inc(0) → s(0)

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

(19) PisEmptyProof (EQUIVALENT transformation)

The TRS P is empty. Hence, there is no (P,Q,R) chain.

(20) TRUE