#15501: floor(), ceil(), trunc(), round() for AA
-------------------------------------+-------------------------------------
Reporter: ppurka | Owner:
Type: defect | Status: needs_review
Priority: major | Milestone: sage-6.1
Component: algebra | Resolution:
Keywords: | Merged in:
Authors: Marc Mezzarobba | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/mmezzarobba/ticket/15501-AA_floor_ceil|
a07f1e7ac809a6377476ff79c35225757eb7ee8d
Dependencies: | Stopgaps:
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Description changed by mmezzarobba:
Old description:
> From google spreadsheet which no one reads `X-(`
>
> It happens that an algebraic number minus itself `(b-b)` is not printed
> as 0, but something like `0.?e-18`. Usually it is not a big problem,
> because `b - b == 0` evaluates to `True`. But interestingly `floor(b-b)`
> is sometimes 0, sometimes a symbolic expression, so weird things can
> happen.
>
> {{{
> sage: a = QQbar((-1)^(1/4)).real()
> sage: floor(a-a) + a
> ---------------------------------------------------------------------------
> TypeError Traceback (most recent call last)
> <ipython-input-337-107a1ad8256f> in <module>()
> ----> 1 floor(a-a) + a
>
> /Applications/sage/local/lib/python2.7/site-
> packages/sage/structure/element.so in
> sage.structure.element.RingElement.__add__
> (sage/structure/element.c:13884)()
>
> /Applications/sage/local/lib/python2.7/site-
> packages/sage/structure/coerce.so in
> sage.structure.coerce.CoercionModel_cache_maps.bin_op
> (sage/structure/coerce.c:8169)()
>
> TypeError: unsupported operand parent(s) for '+': 'Symbolic Ring' and
> 'Algebraic Real Field'
> }}}
New description:
Add methods floor(), ceil(), trunc(), and round() to the implementation of
real algebraic numbers. Also implement trunc() for rational numbers, both
for consistency and to be able to use it in the code for algebraic
numbers.
ORIGINAL BUG DESCRIPTION:
From google spreadsheet which no one reads `X-(`
It happens that an algebraic number minus itself `(b-b)` is not printed as
0, but something like `0.?e-18`. Usually it is not a big problem, because
`b - b == 0` evaluates to `True`. But interestingly `floor(b-b)` is
sometimes 0, sometimes a symbolic expression, so weird things can happen.
{{{
sage: a = QQbar((-1)^(1/4)).real()
sage: floor(a-a) + a
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-337-107a1ad8256f> in <module>()
----> 1 floor(a-a) + a
/Applications/sage/local/lib/python2.7/site-
packages/sage/structure/element.so in
sage.structure.element.RingElement.__add__
(sage/structure/element.c:13884)()
/Applications/sage/local/lib/python2.7/site-
packages/sage/structure/coerce.so in
sage.structure.coerce.CoercionModel_cache_maps.bin_op
(sage/structure/coerce.c:8169)()
TypeError: unsupported operand parent(s) for '+': 'Symbolic Ring' and
'Algebraic Real Field'
}}}
--
--
Ticket URL: <http://trac.sagemath.org/ticket/15501#comment:6>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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