#13516: prime_powers doesn't work with start very well
---------------------------------+------------------------------------------
Reporter: kcrisman | Owner: was
Type: defect | Status: needs_review
Priority: major | Milestone: sage-5.4
Component: number theory | Resolution:
Keywords: beginner | Work issues:
Report Upstream: N/A | Reviewers:
Authors: | Merged in:
Dependencies: | Stopgaps:
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Changes (by khalasz):
* status: new => needs_review
Old description:
> See [https://groups.google.com/forum/?fromgroups=#!topic/sage-
> support/lW_a7ZE3Zf8 this sage-support thread].
>
> {{{
>
> In Sage 5.3, the function prime_powers behaves a little strange:
>
> sage: prime_powers(4,10)
> [4, 5, 7, 8, 9]
> # As expected
>
> sage: prime_powers(5,10)
> [7, 8, 9]
> # 5 isn't a prime power anymore???
>
> # And now things become even worse:
> sage: prime_powers(7,10)
> ---------------------------------------------------------------------------
> IndexError Traceback (most recent call
> last)
>
> /home/mueller/<ipython console> in <module>()
>
> /home/mueller/local/sage-5.3/local/lib/python2.7/site-
> packages/sage/rings/arith.pyc in prime_powers(start, stop)
> 743 i = bisect(v, start)
> 744 if start > 2:
> --> 745 if v[i] == start:
> 746 i -= 1
> 747 w = list(v[i:])
>
> IndexError: list index out of range
> }}}
>
> Yeah, this seems problematic. The code in question is ''old'', too, so
> perhaps there is a more efficient way to do it in the meantime...
New description:
See [https://groups.google.com/forum/?fromgroups=#!topic/sage-
support/lW_a7ZE3Zf8 this sage-support thread].
{{{
In Sage 5.3, the function prime_powers behaves a little strange:
sage: prime_powers(4,10)
[4, 5, 7, 8, 9]
# As expected
sage: prime_powers(5,10)
[7, 8, 9]
# 5 isn't a prime power anymore???
# And now things become even worse:
sage: prime_powers(7,10)
---------------------------------------------------------------------------
IndexError Traceback (most recent call
last)
/home/mueller/<ipython console> in <module>()
/home/mueller/local/sage-5.3/local/lib/python2.7/site-
packages/sage/rings/arith.pyc in prime_powers(start, stop)
743 i = bisect(v, start)
744 if start > 2:
--> 745 if v[i] == start:
746 i -= 1
747 w = list(v[i:])
IndexError: list index out of range
}}}
Yeah, this seems problematic. The code in question is ''old'', too, so
perhaps there is a more efficient way to do it in the meantime...
'''Apply'''
1. [attachment: 13516_primepowers.patch]
--
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13516#comment:3>
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