Hello,

I'm trying to build a "tower" of field extensions but an error occurs.
This is the code:

p = 0xb640000000008c6352000000288d94aa50000534d459922940402af3364b031b
R = GF(p)
_.<X> = PolynomialRing(R)
R2.<X> = R.extension(X^2+1, 'X')
_.<Y> = PolynomialRing(R2)
xi = -X + 1
R6.<Y> = R2.extension(Y^3-xi, 'Y')
_.<Z> = PolynomialRing(R6)
R12.<Z> = R6.extension(Z^2-(Y), 'Z')

An "NotImplementedError" is raised on the "_.<Z> = PolynomialRing(R6)"
line. Is there any other way to accomplish this, or it's just a Sage
limitation? From the traceback, I see it tries to factor the modulus
of R6 but it fails.

Traceback:


/home/conrado/.sage/temp/matamune/8922/
_home_conrado_workspace_sage_bn_sage_14.py in bn_create(p)
     80     xi = -X + _sage_const_1
     81     R6 = R2.extension(Y**_sage_const_3 -xi, 'Y', names=
('Y',)); (Y,) = R6._first_ngens(1)
---> 82     _ = PolynomialRing(R6, names=('Z',)); (Z,) = _._first_ngens
(1)
     83     R12 = R6.extension(Z**_sage_const_2 -(Y), 'Z', names=
('Z',)); (Z,) = R12._first_ngens(1)
     84     return R, R2, R6, R12, X, Y, Z

/home/conrado/sage-3.4.1-linux-Ubuntu_8.10-sse2-i686-Linux/local/lib/
python2.5/site-packages/sage/rings/polynomial/
polynomial_ring_constructor.pyc in PolynomialRing(base_ring, arg1,
arg2, sparse, order, names, name, implementation)
    281                 raise TypeError, "if second arguments is a
string with no commas, then there must be no other non-optional
arguments"
    282             name = arg1
--> 283             R = _single_variate(base_ring, name, sparse,
implementation)
    284         else:
    285             # 2-4. PolynomialRing(base_ring, names,
order='degrevlex'):

/home/conrado/sage-3.4.1-linux-Ubuntu_8.10-sse2-i686-Linux/local/lib/
python2.5/site-packages/sage/rings/polynomial/
polynomial_ring_constructor.pyc in _single_variate(base_ring, name,
sparse, implementation)
    368             R = m.PolynomialRing_dense_padic_ring_fixed_mod
(base_ring, name)
    369
--> 370         elif base_ring.is_field():
    371             R = m.PolynomialRing_field(base_ring, name,
sparse)
    372

/home/conrado/sage-3.4.1-linux-Ubuntu_8.10-sse2-i686-Linux/local/lib/
python2.5/site-packages/sage/rings/polynomial/
polynomial_quotient_ring.pyc in is_field(self)
    454             True
    455         """
--> 456         return self.base_ring().is_field() and self.modulus
().is_irreducible()
    457
    458     def krull_dimension(self):

/home/conrado/sage-3.4.1-linux-Ubuntu_8.10-sse2-i686-Linux/local/lib/
python2.5/site-packages/sage/rings/polynomial/polynomial_element.so in
sage.rings.polynomial.polynomial_element.Polynomial.is_irreducible
(sage/rings/polynomial/polynomial_element.c:37402)()

/home/conrado/sage-3.4.1-linux-Ubuntu_8.10-sse2-i686-Linux/local/lib/
python2.5/site-packages/sage/rings/polynomial/polynomial_element.so in
sage.rings.polynomial.polynomial_element.Polynomial.factor (sage/rings/
polynomial/polynomial_element.c:25443)()

NotImplementedError:

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