> It would be helpful if you could give a more concrete example, e.g., a session
> where you have some elements, and finally want to do something with them.
That's good idea, William. Let me back up to and change my question
to a more fundamental one. How does one compute in QQbar with Sage?
For example, how about factoring a polynomial, computing a radical
ideal, or computing a variety (see below)? I get the same error for
all these: "no conversion of this ring to a Singular ring defined".
Alex
----------------------------------------------------------------------
| Sage Version 3.2, Release Date: 2008-11-20 |
| Type notebook() for the GUI, and license() for information. |
----------------------------------------------------------------------
sage: R.<w,z>= PolynomialRing(QQbar,2,order='lex')
sage: H= w^3*(w*z-1)^2*(w^2+z^2-1)
sage: H.factor()
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)
/Users/arai021/<ipython console> in <module>()
/Applications/sage/local/lib/python2.5/site-packages/sage/rings/
polynomial/multi_polynomial_element.pyc in factor(self)
1276 pass
1277
-> 1278 R._singular_().set_ring()
1279 S = self._singular_().factorize()
1280 factors = S[1]
/Applications/sage/local/lib/python2.5/site-packages/sage/rings/
polynomial/polynomial_singular_interface.pyc in _singular_(self,
singular, force)
158 return R
159 except (AttributeError, ValueError):
--> 160 return self._singular_init_(singular, force)
161
162 def _singular_init_(self, singular=singular_default,
force=False):
/Applications/sage/local/lib/python2.5/site-packages/sage/rings/
polynomial/polynomial_singular_interface.pyc in _singular_init_(self,
singular, force)
165 """
166 if not can_convert_to_singular(self) and not force:
--> 167 raise TypeError, "no conversion of this ring to a
Singular ring defined"
168
169 if self.ngens()==1:
TypeError: no conversion of this ring to a Singular ring defined
sage: I= R.ideal(H).radical()
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)
/Users/arai021/<ipython console> in <module>()
/Applications/sage/local/lib/python2.5/site-packages/sage/rings/
polynomial/multi_polynomial_ideal.pyc in wrapper(*args, **kwds)
315 """
316 with RedSBContext():
--> 317 return func(*args, **kwds)
318 wrapper.__doc__=func.__doc__
319 return wrapper
/Applications/sage/local/lib/python2.5/site-packages/sage/rings/
polynomial/multi_polynomial_ideal.pyc in radical(self)
1090 """
1091 S = self.ring()
-> 1092 I = self._singular_()
1093 I.parent().lib('primdec.lib')
1094 r = I.radical()
/Applications/sage/local/lib/python2.5/site-packages/sage/rings/
polynomial/multi_polynomial_ideal.pyc in _singular_(self, singular)
416 """
417 try:
--> 418 self.ring()._singular_(singular).set_ring
()
419 I = self.__singular
420 if not (I.parent() is singular):
/Applications/sage/local/lib/python2.5/site-packages/sage/rings/
polynomial/polynomial_singular_interface.pyc in _singular_(self,
singular, force)
158 return R
159 except (AttributeError, ValueError):
--> 160 return self._singular_init_(singular, force)
161
162 def _singular_init_(self, singular=singular_default,
force=False):
/Applications/sage/local/lib/python2.5/site-packages/sage/rings/
polynomial/polynomial_singular_interface.pyc in _singular_init_(self,
singular, force)
165 """
166 if not can_convert_to_singular(self) and not force:
--> 167 raise TypeError, "no conversion of this ring to a
Singular ring defined"
168
169 if self.ngens()==1:
TypeError: no conversion of this ring to a Singular ring defined
sage: R.ideal(H).variety()
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)
/Users/arai021/<ipython console> in <module>()
/Applications/sage/local/lib/python2.5/site-packages/sage/rings/
polynomial/multi_polynomial_ideal.pyc in variety(self, ring)
1528 P = self.ring()
1529 if ring is not None: P = P.change_ring(ring)
-> 1530 T = self.triangular_decomposition
('singular:triangLfak')
1531
1532 V = []
/Applications/sage/local/lib/python2.5/site-packages/sage/rings/
polynomial/multi_polynomial_ideal.pyc in triangular_decomposition
(self, algorithm, singular)
740 P = self.ring()
741
--> 742 is_groebner = self.basis_is_groebner()
743
744 # make sure to work w.r.t. 'lex'
/Applications/sage/local/lib/python2.5/site-packages/sage/rings/
polynomial/multi_polynomial_ideal.pyc in basis_is_groebner(self,
singular)
1235 a Groebner basis.
1236 """
-> 1237 self.ring()._singular_().set_ring()
1238
1239 F = singular( self.gens(), "module" )
/Applications/sage/local/lib/python2.5/site-packages/sage/rings/
polynomial/polynomial_singular_interface.pyc in _singular_(self,
singular, force)
158 return R
159 except (AttributeError, ValueError):
--> 160 return self._singular_init_(singular, force)
161
162 def _singular_init_(self, singular=singular_default,
force=False):
/Applications/sage/local/lib/python2.5/site-packages/sage/rings/
polynomial/polynomial_singular_interface.pyc in _singular_init_(self,
singular, force)
165 """
166 if not can_convert_to_singular(self) and not force:
--> 167 raise TypeError, "no conversion of this ring to a
Singular ring defined"
168
169 if self.ngens()==1:
TypeError: no conversion of this ring to a Singular ring defined
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