Ideals in multivariate polynomial rings with no variables raise exception on comparison

[sagetrac-broune]

This code

ring = PolynomialRing(QQ, names=[])

id = ring.ideal(0)

print id == id

gives the following error message

---

<type 'exceptions.StopIteration'> Traceback (most recent call last)

/Users/bjarke/sync/ in ()

/Users/bjarke/sync/element.pyx in sage.structure.element.Element.richcmp (sage/structure/element.c:4558)()

/Users/bjarke/sync/element.pyx in sage.structure.element.Element._richcmp (sage/structure/element.c:4453)()

/Users/bjarke/sage-3.0/local/lib/python2.5/site-packages/sage/rings/polynomial/multi_polynomial_ideal.py in cmp(self, other)
347 True
348 """
--> 349 l = self.groebner_basis()
350 r = other.groebner_basis()
351 return cmp(r,l)

/Users/bjarke/sage-3.0/local/lib/python2.5/site-packages/sage/rings/polynomial/multi_polynomial_ideal.py in groebner_basis(self, algorithm, *args, **kwds)
1836 except TypeError: # conversion to Singular not supported
1837 # we might want to print a warning here
-> 1838 gb = toy_buchberger.buchberger_improved(self, *args, **kwds)
1839 elif algorithm.startswith('singular:'):
1840 gb = self._groebner_basis_using_singular(algorithm[9:])

/Users/bjarke/sage-3.0/local/lib/python2.5/site-packages/sage/rings/polynomial/toy_buchberger.py in buchberger_improved(F)
232 print "%d reductions to zero."%(reductions_to_zero)
233
--> 234 return Sequence(inter_reduction(G))
235
236 def update(G,B,h):

/Users/bjarke/sage-3.0/local/lib/python2.5/site-packages/sage/rings/polynomial/toy_buchberger.py in inter_reduction(Q)
324 Q -- a set of polynomials
325 """
--> 326 base_ring = iter(Q).next().base_ring()
327 Q = set(Q)
328 while True:

<type 'exceptions.StopIteration'>:

Component: commutative algebra

Keywords: multivariate polynomial ring, no variables

Issue created by migration from https://trac.sagemath.org/ticket/3028

[sagetrac-broune]

Attachment: idcomp.changeset.gz

[sagetrac-cwitty]

comment:3

Code looks good, doctests pass in sage/rings/polynomial. Positive review.

[sagetrac-mabshoff]

comment:4

Merged in Sage 3.0.2.alpha0