#18585: Comparison of sparse polynomials
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       Reporter:  bruno              |        Owner:
           Type:  defect             |       Status:  needs_review
       Priority:  major              |    Milestone:  sage-6.9
      Component:  commutative        |   Resolution:
  algebra                            |    Merged in:
       Keywords:  polynomials        |    Reviewers:  Vincent Delecroix
        Authors:  Bruno Grenet       |  Work issues:
Report Upstream:  N/A                |       Commit:
         Branch:                     |  3121374eed7b683bd135e9ec5086aac03c4c8eb5
  u/bruno/compare_sparse_polynomials |     Stopgaps:
   Dependencies:                     |
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Comment (by bruno):

 Replying to [comment:14 vdelecroix]:
 > In
 > {{{
 >             if c > 0:
 >                 c1 = cmp(d1[k1], 0)
 >                 if c1: return c1
 > }}}
 > Isn't `c1` automatically nonzero? Could there be some zero coefficients
 in the dictionary?

 {{{
 sage: R.<x> = PolynomialRing(ZZ, sparse=True)
 sage: p = R({0:1, 1:0, 2:1}, check=False)
 sage: p
 x^2 + 1
 sage: p.dict()
 {0: 1, 1: 0, 2: 1}
 }}}
 I doubt this happens often in practice, but since this is possible, I am
 quite reluctant to remove the test.

--
Ticket URL: <http://trac.sagemath.org/ticket/18585#comment:17>
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