(0) Obligation:

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

active(zeros) → mark(cons(0, zeros))
active(U11(tt, L)) → mark(U12(tt, L))
active(U12(tt, L)) → mark(s(length(L)))
active(U21(tt, IL, M, N)) → mark(U22(tt, IL, M, N))
active(U22(tt, IL, M, N)) → mark(U23(tt, IL, M, N))
active(U23(tt, IL, M, N)) → mark(cons(N, take(M, IL)))
active(length(nil)) → mark(0)
active(length(cons(N, L))) → mark(U11(tt, L))
active(take(0, IL)) → mark(nil)
active(take(s(M), cons(N, IL))) → mark(U21(tt, IL, M, N))
active(cons(X1, X2)) → cons(active(X1), X2)
active(U11(X1, X2)) → U11(active(X1), X2)
active(U12(X1, X2)) → U12(active(X1), X2)
active(s(X)) → s(active(X))
active(length(X)) → length(active(X))
active(U21(X1, X2, X3, X4)) → U21(active(X1), X2, X3, X4)
active(U22(X1, X2, X3, X4)) → U22(active(X1), X2, X3, X4)
active(U23(X1, X2, X3, X4)) → U23(active(X1), X2, X3, X4)
active(take(X1, X2)) → take(active(X1), X2)
active(take(X1, X2)) → take(X1, active(X2))
cons(mark(X1), X2) → mark(cons(X1, X2))
U11(mark(X1), X2) → mark(U11(X1, X2))
U12(mark(X1), X2) → mark(U12(X1, X2))
s(mark(X)) → mark(s(X))
length(mark(X)) → mark(length(X))
U21(mark(X1), X2, X3, X4) → mark(U21(X1, X2, X3, X4))
U22(mark(X1), X2, X3, X4) → mark(U22(X1, X2, X3, X4))
U23(mark(X1), X2, X3, X4) → mark(U23(X1, X2, X3, X4))
take(mark(X1), X2) → mark(take(X1, X2))
take(X1, mark(X2)) → mark(take(X1, X2))
proper(zeros) → ok(zeros)
proper(cons(X1, X2)) → cons(proper(X1), proper(X2))
proper(0) → ok(0)
proper(U11(X1, X2)) → U11(proper(X1), proper(X2))
proper(tt) → ok(tt)
proper(U12(X1, X2)) → U12(proper(X1), proper(X2))
proper(s(X)) → s(proper(X))
proper(length(X)) → length(proper(X))
proper(U21(X1, X2, X3, X4)) → U21(proper(X1), proper(X2), proper(X3), proper(X4))
proper(U22(X1, X2, X3, X4)) → U22(proper(X1), proper(X2), proper(X3), proper(X4))
proper(U23(X1, X2, X3, X4)) → U23(proper(X1), proper(X2), proper(X3), proper(X4))
proper(take(X1, X2)) → take(proper(X1), proper(X2))
proper(nil) → ok(nil)
cons(ok(X1), ok(X2)) → ok(cons(X1, X2))
U11(ok(X1), ok(X2)) → ok(U11(X1, X2))
U12(ok(X1), ok(X2)) → ok(U12(X1, X2))
s(ok(X)) → ok(s(X))
length(ok(X)) → ok(length(X))
U21(ok(X1), ok(X2), ok(X3), ok(X4)) → ok(U21(X1, X2, X3, X4))
U22(ok(X1), ok(X2), ok(X3), ok(X4)) → ok(U22(X1, X2, X3, X4))
U23(ok(X1), ok(X2), ok(X3), ok(X4)) → ok(U23(X1, X2, X3, X4))
take(ok(X1), ok(X2)) → ok(take(X1, X2))
top(mark(X)) → top(proper(X))
top(ok(X)) → top(active(X))

Q is empty.

(1) QTRSToCSRProof (EQUIVALENT transformation)

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

active(zeros) → mark(cons(0, zeros))
active(U11(tt, L)) → mark(U12(tt, L))
active(U12(tt, L)) → mark(s(length(L)))
active(U21(tt, IL, M, N)) → mark(U22(tt, IL, M, N))
active(U22(tt, IL, M, N)) → mark(U23(tt, IL, M, N))
active(U23(tt, IL, M, N)) → mark(cons(N, take(M, IL)))
active(length(nil)) → mark(0)
active(length(cons(N, L))) → mark(U11(tt, L))
active(take(0, IL)) → mark(nil)
active(take(s(M), cons(N, IL))) → mark(U21(tt, IL, M, N))
active(cons(X1, X2)) → cons(active(X1), X2)
active(U11(X1, X2)) → U11(active(X1), X2)
active(U12(X1, X2)) → U12(active(X1), X2)
active(s(X)) → s(active(X))
active(length(X)) → length(active(X))
active(U21(X1, X2, X3, X4)) → U21(active(X1), X2, X3, X4)
active(U22(X1, X2, X3, X4)) → U22(active(X1), X2, X3, X4)
active(U23(X1, X2, X3, X4)) → U23(active(X1), X2, X3, X4)
active(take(X1, X2)) → take(active(X1), X2)
active(take(X1, X2)) → take(X1, active(X2))
cons(mark(X1), X2) → mark(cons(X1, X2))
U11(mark(X1), X2) → mark(U11(X1, X2))
U12(mark(X1), X2) → mark(U12(X1, X2))
s(mark(X)) → mark(s(X))
length(mark(X)) → mark(length(X))
U21(mark(X1), X2, X3, X4) → mark(U21(X1, X2, X3, X4))
U22(mark(X1), X2, X3, X4) → mark(U22(X1, X2, X3, X4))
U23(mark(X1), X2, X3, X4) → mark(U23(X1, X2, X3, X4))
take(mark(X1), X2) → mark(take(X1, X2))
take(X1, mark(X2)) → mark(take(X1, X2))
proper(zeros) → ok(zeros)
proper(cons(X1, X2)) → cons(proper(X1), proper(X2))
proper(0) → ok(0)
proper(U11(X1, X2)) → U11(proper(X1), proper(X2))
proper(tt) → ok(tt)
proper(U12(X1, X2)) → U12(proper(X1), proper(X2))
proper(s(X)) → s(proper(X))
proper(length(X)) → length(proper(X))
proper(U21(X1, X2, X3, X4)) → U21(proper(X1), proper(X2), proper(X3), proper(X4))
proper(U22(X1, X2, X3, X4)) → U22(proper(X1), proper(X2), proper(X3), proper(X4))
proper(U23(X1, X2, X3, X4)) → U23(proper(X1), proper(X2), proper(X3), proper(X4))
proper(take(X1, X2)) → take(proper(X1), proper(X2))
proper(nil) → ok(nil)
cons(ok(X1), ok(X2)) → ok(cons(X1, X2))
U11(ok(X1), ok(X2)) → ok(U11(X1, X2))
U12(ok(X1), ok(X2)) → ok(U12(X1, X2))
s(ok(X)) → ok(s(X))
length(ok(X)) → ok(length(X))
U21(ok(X1), ok(X2), ok(X3), ok(X4)) → ok(U21(X1, X2, X3, X4))
U22(ok(X1), ok(X2), ok(X3), ok(X4)) → ok(U22(X1, X2, X3, X4))
U23(ok(X1), ok(X2), ok(X3), ok(X4)) → ok(U23(X1, X2, X3, X4))
take(ok(X1), ok(X2)) → ok(take(X1, X2))
top(mark(X)) → top(proper(X))
top(ok(X)) → top(active(X))

Q is empty.
Special symbols used for the transformation (see [GM04]):
top: top, active: active, mark: mark, ok: ok, proper: proper
The replacement map contains the following entries:

zeros: empty set
cons: {1}
0: empty set
U11: {1}
tt: empty set
U12: {1}
s: {1}
length: {1}
U21: {1}
U22: {1}
U23: {1}
take: {1, 2}
nil: empty set
The QTRS contained all rules created by the complete Giesl-Middeldorp transformation. Therefore, the inverse transformation is complete (and sound).

(2) Obligation:

Context-sensitive rewrite system:
The TRS R consists of the following rules:

zeroscons(0, zeros)
U11(tt, L) → U12(tt, L)
U12(tt, L) → s(length(L))
U21(tt, IL, M, N) → U22(tt, IL, M, N)
U22(tt, IL, M, N) → U23(tt, IL, M, N)
U23(tt, IL, M, N) → cons(N, take(M, IL))
length(nil) → 0
length(cons(N, L)) → U11(tt, L)
take(0, IL) → nil
take(s(M), cons(N, IL)) → U21(tt, IL, M, N)

The replacement map contains the following entries:

zeros: empty set
cons: {1}
0: empty set
U11: {1}
tt: empty set
U12: {1}
s: {1}
length: {1}
U21: {1}
U22: {1}
U23: {1}
take: {1, 2}
nil: empty set

(3) CSRRRRProof (EQUIVALENT transformation)

The following CSR is given: Context-sensitive rewrite system:
The TRS R consists of the following rules:

zeroscons(0, zeros)
U11(tt, L) → U12(tt, L)
U12(tt, L) → s(length(L))
U21(tt, IL, M, N) → U22(tt, IL, M, N)
U22(tt, IL, M, N) → U23(tt, IL, M, N)
U23(tt, IL, M, N) → cons(N, take(M, IL))
length(nil) → 0
length(cons(N, L)) → U11(tt, L)
take(0, IL) → nil
take(s(M), cons(N, IL)) → U21(tt, IL, M, N)

The replacement map contains the following entries:

zeros: empty set
cons: {1}
0: empty set
U11: {1}
tt: empty set
U12: {1}
s: {1}
length: {1}
U21: {1}
U22: {1}
U23: {1}
take: {1, 2}
nil: empty set
Used ordering:
Polynomial interpretation [POLO]:


POL(0) = 0   
POL(U11(x1, x2)) = x1 + x2   
POL(U12(x1, x2)) = x1 + x2   
POL(U21(x1, x2, x3, x4)) = 1 + x1 + x2 + x3 + x4   
POL(U22(x1, x2, x3, x4)) = 1 + x1 + x2 + x3 + x4   
POL(U23(x1, x2, x3, x4)) = 1 + x1 + x2 + x3 + x4   
POL(cons(x1, x2)) = x1 + x2   
POL(length(x1)) = x1   
POL(nil) = 1   
POL(s(x1)) = x1   
POL(take(x1, x2)) = 1 + x1 + x2   
POL(tt) = 0   
POL(zeros) = 0   
With this ordering the following rules can be removed by the rule removal processor [LPAR04] because they are oriented strictly:

length(nil) → 0


(4) Obligation:

Context-sensitive rewrite system:
The TRS R consists of the following rules:

zeroscons(0, zeros)
U11(tt, L) → U12(tt, L)
U12(tt, L) → s(length(L))
U21(tt, IL, M, N) → U22(tt, IL, M, N)
U22(tt, IL, M, N) → U23(tt, IL, M, N)
U23(tt, IL, M, N) → cons(N, take(M, IL))
length(cons(N, L)) → U11(tt, L)
take(0, IL) → nil
take(s(M), cons(N, IL)) → U21(tt, IL, M, N)

The replacement map contains the following entries:

zeros: empty set
cons: {1}
0: empty set
U11: {1}
tt: empty set
U12: {1}
s: {1}
length: {1}
U21: {1}
U22: {1}
U23: {1}
take: {1, 2}
nil: empty set

(5) CSRRRRProof (EQUIVALENT transformation)

The following CSR is given: Context-sensitive rewrite system:
The TRS R consists of the following rules:

zeroscons(0, zeros)
U11(tt, L) → U12(tt, L)
U12(tt, L) → s(length(L))
U21(tt, IL, M, N) → U22(tt, IL, M, N)
U22(tt, IL, M, N) → U23(tt, IL, M, N)
U23(tt, IL, M, N) → cons(N, take(M, IL))
length(cons(N, L)) → U11(tt, L)
take(0, IL) → nil
take(s(M), cons(N, IL)) → U21(tt, IL, M, N)

The replacement map contains the following entries:

zeros: empty set
cons: {1}
0: empty set
U11: {1}
tt: empty set
U12: {1}
s: {1}
length: {1}
U21: {1}
U22: {1}
U23: {1}
take: {1, 2}
nil: empty set
Used ordering:
Polynomial interpretation [POLO]:


POL(0) = 0   
POL(U11(x1, x2)) = x1 + x2   
POL(U12(x1, x2)) = x1 + x2   
POL(U21(x1, x2, x3, x4)) = 1 + x1 + x2 + x3 + x4   
POL(U22(x1, x2, x3, x4)) = 1 + x1 + x2 + x3 + x4   
POL(U23(x1, x2, x3, x4)) = 1 + x1 + x2 + x3 + x4   
POL(cons(x1, x2)) = x1 + x2   
POL(length(x1)) = x1   
POL(nil) = 0   
POL(s(x1)) = x1   
POL(take(x1, x2)) = 1 + x1 + x2   
POL(tt) = 0   
POL(zeros) = 0   
With this ordering the following rules can be removed by the rule removal processor [LPAR04] because they are oriented strictly:

take(0, IL) → nil


(6) Obligation:

Context-sensitive rewrite system:
The TRS R consists of the following rules:

zeroscons(0, zeros)
U11(tt, L) → U12(tt, L)
U12(tt, L) → s(length(L))
U21(tt, IL, M, N) → U22(tt, IL, M, N)
U22(tt, IL, M, N) → U23(tt, IL, M, N)
U23(tt, IL, M, N) → cons(N, take(M, IL))
length(cons(N, L)) → U11(tt, L)
take(s(M), cons(N, IL)) → U21(tt, IL, M, N)

The replacement map contains the following entries:

zeros: empty set
cons: {1}
0: empty set
U11: {1}
tt: empty set
U12: {1}
s: {1}
length: {1}
U21: {1}
U22: {1}
U23: {1}
take: {1, 2}

(7) ContextSensitiveLoopProof (EQUIVALENT transformation)


zeroscons(0, zeros)
U11(tt, L) → U12(tt, L)
U12(tt, L) → s(length(L))
U21(tt, IL, M, N) → U22(tt, IL, M, N)
U22(tt, IL, M, N) → U23(tt, IL, M, N)
U23(tt, IL, M, N) → cons(N, take(M, IL))
length(cons(N, L)) → U11(tt, L)
take(s(M), cons(N, IL)) → U21(tt, IL, M, N)

---------- Loop: ----------

U12(tt, zeros) → s(length(zeros)) with rule U12(tt, L) → s(length(L)) at position [] and matcher [L / zeros]

s(length(zeros)) → s(length(cons(0, zeros))) with rule zeroscons(0, zeros) at position [0,0] and matcher [ ]

s(length(cons(0, zeros))) → s(U11(tt, zeros)) with rule length(cons(N, L)) → U11(tt, L) at position [0] and matcher [N / 0, L / zeros]

s(U11(tt, zeros)) → s(U12(tt, zeros)) with rule U11(tt, L) → U12(tt, L) at position [0] and matcher [L / zeros]

Now an instance of the first term with Matcher [ ] occurs in the last term at position [0].

Context: s([])

We used [[THIEMANN_LOOPS_UNDER_STRATEGIES], Theorem 1] to show that this loop is an context-sensitive loop.

(8) NO