random_element fails for power series over real field, has inaccurate docstring

[nilesjohnson]

The random_element method of univariate power series does not pass arguments to the underlying polynomial ring accurately, and the description of its second argument is inaccurate.

c.f. this thread from sage-devel

sage: SQ = PowerSeriesRing(QQ,'v')
sage: SR = PowerSeriesRing(RR,'v')

sage: SQ.random_element(5,100)  # docstring promises coefficients are uniformly distributed between -100 and 100
-7/3 + 5/8*v + 37/60*v^2 + 33/8*v^3 + 77/89*v^4 + O(v^5)

sage: SR.random_element(5)  # broken
Traceback (most recent call last):
...
TypeError: unsupported operand type(s) for -: 'int' and 'NoneType'

CC: @rishikesha

Component: commutative algebra

Keywords: power series, random element

Author: Niles Johnson, Jeroen Demeyer

Reviewer: Aly Deines

Merged: sage-4.6.2.alpha1

Issue created by migration from https://trac.sagemath.org/ticket/9481

[nilesjohnson]

emulated behavior of polynomial ring random_element, as suggested on sage-devel; commit message now references ticket number

[rishikesha]

comment:2

Attachment: trac_9481_ps_random_element.patch.gz

[nilesjohnson]

Changed author from niles to Niles Johnson

[adeines]

comment:4

Looks good.

[adeines]

Reviewer: Aly Deines

[jdemeyer]

Attachment: trac_9481_ps_random_element.2.patch.gz

Same patch, fixed commit message

[jdemeyer]

comment:6

Docstring needs reformatting to proper Sphinx markup.

[jdemeyer]

Apply on top of previous patch

[jdemeyer]

Changed author from Niles Johnson to Niles Johnson, Jeroen Demeyer

[jdemeyer]

comment:7

Attachment: 9481_docstring.patch.gz

[nilesjohnson]

comment:8

All documentation now builds without error or warning, so positive review for attachment: 9481_docstring.patch

[jdemeyer]

Merged: sage-4.6.2.alpha1