#7654: Conversion bug in MPolynomialRing_libsingular
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Reporter: SimonKing | Owner: malb
Type: defect | Status: new
Priority: critical | Milestone: sage-4.7.1
Component: commutative algebra | Keywords: conversion libsingular
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
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Comment(by SimonKing):
Replying to [comment:2 malb]:
> Hi, sorry for taking so long to take a look. The reason for this
behaviour is that currently, conversion is simply defined by index:
I know.
> So, technically, it is not a bug.
I disagree: There is a bug.
Admittedly it is not a bug with my original example, because it contains
`z_1` (index 9 in `R.gens()`), whereas `S` only has 9 variables. So, the
attempt to find a generator of index 9 must fail (but please with a less
cryptic error message!!).
However, we also have
{{{
sage: S(y_1*z_2^2*z_4)
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', (1154, 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', (1154, 0))
...
}}}
even though we have
{{{
sage: R.gens().index(y_1)
3
sage: R.gens().index(z_2)
8
sage: R.gens().index(z_4)
6
sage: S.gens()[3]
y_1
sage: S.gens()[8]
z_1
sage: S.gens()[6]
z_3
}}}
So, using indices for conversion, one ''should'' have
{{{
sage: S(y_1*z_2^2*z_4)
y_1*z_1^2*z_3
}}}
but one gets a traceback.
That is clearly a bug. Is that fixed with your patch?
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/7654#comment:4>
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