#5685: enhanced nth_root in ZZ and QQ and related utilities
------------------------------+---------------------------------------------
Reporter: cremona | Owner: somebody
Type: enhancement | Status: new
Priority: major | Milestone: sage-3.4.1
Component: basic arithmetic | Keywords: nth root rational integer
------------------------------+---------------------------------------------
As discussed here: http://groups.google.co.uk/group/sage-
nt/browse_thread/thread/4c6e60b6a20cabae#
I do not like this inconsistency between ZZ and QQ:
{{{
sage: a=ZZ(8)
sage: a.nth_root(3)
2
sage: b=QQ(8)
sage: b.nth_root(3)
2
sage: a.nth_root(2)
2
sage: b.nth_root(2)
---------------------------------------------------------------------------
ValueError Traceback (most recent call
last)
/home/masgaj/.sage/temp/host_56_150/13463/_home_masgaj_sage_egros_sage_5.py
in <module>()
/local/jec/sage-3.4/local/lib/python2.5/site-
packages/sage/rings/rational.so
in sage.rings.rational.Rational.nth_root
(sage/rings/rational.c:8888)()
ValueError: not a perfect nth power
}}}
I cannot think of a reason why we have an nth_root function on
integers which silently truncates a real root for positive argument
and gives a ValueError for negative ones.
The attached ticket deals with this, and at the same time adds a couple of
extra utilities which I needed for rational numbers.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/5685>
Sage <http://sagemath.org/>
Sage - Open Source Mathematical Software: Building the Car Instead of
Reinventing the Wheel
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