#12198: is_squarefree() over multivariate rings does not work
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Reporter: MvanBeek | Owner: AlexGhitza
Type: defect | Status: new
Priority: critical | Milestone: sage-4.8
Component: basic arithmetic | Keywords: squarefree, singular
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
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Changes (by burcin):
* keywords: => squarefree, singular
* priority: major => critical
* component: algebraic geometry => basic arithmetic
Comment:
Integer coefficients are relatively new in Singular. Many fuctions do not
work with them. In this case, Singular raises an error using a callback
function (see `sage.libs.singular.singular.libsingular_error_callback`).
Unfortunately we do not check for it and return wrong results.
A workaround, suggested by Martin Lee, for this immediate problem is to
`change_ring(QQ)` and call `is_squarefree()` there.
If there isn't a ticket already about handling errors raised in
libsingular, we should open one. Note that the magical function interface
(the one you get through `sage.libs.singular.ff.*`) can handle Singular
errors. It's only direct C library calls that should check explicitly if
Singular raised an error. Perhaps we can solve it by wrapping the
declarations in `sage/libs/singular/singular-cdefs.pxi` in a preprocessor
macro which calls `PyErr_Occured()` after raising an exception in
`libsingular_error_callback()`.
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12198#comment:3>
Sage <http://www.sagemath.org>
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