#19939: Fix EuclideanRings.ParentMethods._test_quo_rem to use `not r.is_zero()`
rather than `r!=0`
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Reporter: nthiery | Owner:
Type: defect | Status: needs_review
Priority: major | Milestone: sage-7.1
Component: categories | Resolution:
Keywords: | Merged in:
Authors: Nicolas M. Thiéry | Reviewers: Samuel Lelièvre
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/nthiery/fix_euclideanrings_parentmethods__test_quo_rem_to_use__not_r_is_zero____rather_than__r__0_|
2d11e11975a16a496f16c8f56151a3932b45ed71
Dependencies: #19937 | Stopgaps:
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Comment (by nthiery):
I indered pondered about this. I went for using `r.is_zero()` for
style consistency with the nearby zero tests. But I don't have a
strong opinion, and I am fine switching to `if r`. In that case, maybe
the nearby zero tests should be changed accordingly for
consistency. What do you think?
By the way: I looked at the current tests failure. They are due to the
default implementation of `quo_rem` for `Fields` which return a plain
`0` for the remainder instead of the zero of the field:
sage: K.<a> = NumberField(x^3 - 2); K
Number Field in a with defining polynomial x^3 - 2
sage: y = K.an_element()
sage: y.parent()
Number Field in a with defining polynomial x^3 - 2
sage: q,r = y.quo_rem(y-1)
sage: q,r
sage: parent(q) # OK
Number Field in a with defining polynomial x^3 - 2
sage: type(r) # GASP!!!
<type 'int'>
I am going to handle this right now by:
1. Updating `EuclideanRings.ParentMethods._test_quo_rem` to test for this
2. Fixing the default implementation of quo_rem
--
Ticket URL: <http://trac.sagemath.org/ticket/19939#comment:5>
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