(0) Obligation:
Q restricted rewrite system:
The TRS R consists of the following rules:
is_empty(nil) → true
is_empty(cons(x, l)) → false
hd(cons(x, l)) → x
tl(cons(x, l)) → l
append(l1, l2) → ifappend(l1, l2, l1)
ifappend(l1, l2, nil) → l2
ifappend(l1, l2, cons(x, l)) → cons(x, append(l, l2))
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:
APPEND(l1, l2) → IFAPPEND(l1, l2, l1)
IFAPPEND(l1, l2, cons(x, l)) → APPEND(l, l2)
The TRS R consists of the following rules:
is_empty(nil) → true
is_empty(cons(x, l)) → false
hd(cons(x, l)) → x
tl(cons(x, l)) → l
append(l1, l2) → ifappend(l1, l2, l1)
ifappend(l1, l2, nil) → l2
ifappend(l1, l2, cons(x, l)) → cons(x, append(l, l2))
Q is empty.
We have to consider all minimal (P,Q,R)-chains.
(3) QDPSizeChangeProof (EQUIVALENT transformation)
We used the following order and afs together with the size-change analysis [AAECC05] to show that there are no infinite chains for this DP problem.
Order:Homeomorphic Embedding Order
AFS:
cons(x1, x2) = cons(x2)
From the DPs we obtained the following set of size-change graphs:
- IFAPPEND(l1, l2, cons(x, l)) → APPEND(l, l2) (allowed arguments on rhs = {1, 2})
The graph contains the following edges 3 > 1, 2 >= 2
- APPEND(l1, l2) → IFAPPEND(l1, l2, l1) (allowed arguments on rhs = {1, 2, 3})
The graph contains the following edges 1 >= 1, 2 >= 2, 1 >= 3
We oriented the following set of usable rules [AAECC05,FROCOS05].
none
(4) TRUE