#8992: Coercion of univariate quotient polynomial rings
-------------------------+--------------------------------------------------
Reporter: SimonKing | Owner: robertwb
Type: defect | Status: needs_work
Priority: major | Milestone: sage-5.0
Component: coercion | Keywords: coercion quotient ring
Work_issues: rewrite | Upstream: N/A
Reviewer: PatchBot | Author: Simon King
Merged: | Dependencies:
-------------------------+--------------------------------------------------
Changes (by SimonKing):
* work_issues: rebase => rewrite
Comment:
Apparently, all but the last problem mentioned in the ticket description
have already been fixed in other tickets. Namely, with vanilla
sage-5.0.beta7, one has
{{{
sage: P.<x> = QQ[]
sage: Q1 = P.quo([(x^2+1)^2*(x^2-3)])
sage: Q2 = P.quo([(x^2+1)^2*(x^5+3)])
sage: from sage.categories.pushout import pushout
sage: Q = pushout(Q1,Q2); Q
Univariate Quotient Polynomial Ring in xbar over Rational Field with
modulus x^4 + 2*x^2 + 1
sage: Q.has_coerce_map_from(Q1)
True
sage: Q.has_coerce_map_from(Q2)
True
sage: Q(Q1.gen())
xbar
sage: Q(str(Q.gen()))
ERROR: An unexpected error occurred while tokenizing input
The following traceback may be corrupted or invalid
The error message is: ('EOF in multi-line statement', (2068, 0))
ERROR: An unexpected error occurred while tokenizing input
The following traceback may be corrupted or invalid
The error message is: ('EOF in multi-line statement', (2068, 0))
ERROR: An unexpected error occurred while tokenizing input
The following traceback may be corrupted or invalid
The error message is: ('EOF in multi-line statement', (2068, 0))
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)
...
TypeError: unable to convert xbar to a rational
}}}
Also, the `__call__` method of quotient rings has already been replaced by
an `_element_constructor_`, as it should.
So, I wouldn't say that the patch needs to be rebased: It has to be
rewritten, or better, it needs to be reduced to those parts that are
responsible for making a quotient ring understand the string
representation of its generators.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/8992#comment:7>
Sage <http://www.sagemath.org>
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