On Fri, Sep 21, 2012 at 7:53 AM, kcrisman <kcris...@gmail.com> wrote: > > > On Friday, September 21, 2012 9:14:54 AM UTC-4, Peter Mueller wrote: >> >> 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 >> > > Apparently this hasn't been changed for a long time. "hg blame" leads me to > > 7046: start, stop = 1, integer.Integer(start) > 10906: v = fast_arith.prime_range(stop) > 7046: w.insert(0, integer.Integer(1)) > > where 7046 is http://trac.sagemath.org/sage_trac/ticket/922 which doesn't > cover this, and 10906 is from a generic cleanup ticket in 2008. > > Everything else from this changeset long long ago: > > 2329103:changeset: 5265:d6107e5bc8b1 > 2329134-user: William Stein <wst...@gmail.com> > 2329180-date: Mon Jul 02 03:21:30 2007 -0700 > 2329224-summary: Add prime_powers function. > > So I'm amazed that you are the first person to come across this!
A guess why: I (and most people) never used this function except in the form prime_powers(B), to compute all prime powers up to B. That's probably why this wasn't noticed before. In applications, it is much more common to want all prime powers up to a bound, instead of the prime powers in an interval. > >> >> PS: I submitted that yesterday via the `Report a Problem' link. Not sure >> if that arrived. > > > That spreadsheet is unfortunately not canvassed as often as we'd like, so > it's great that you reported this here. > > -- > You received this message because you are subscribed to the Google Groups > "sage-support" group. > To post to this group, send email to sage-support@googlegroups.com. > To unsubscribe from this group, send email to > sage-support+unsubscr...@googlegroups.com. > Visit this group at http://groups.google.com/group/sage-support?hl=en. > > -- William Stein Professor of Mathematics University of Washington http://wstein.org -- You received this message because you are subscribed to the Google Groups "sage-support" group. To post to this group, send email to sage-support@googlegroups.com. To unsubscribe from this group, send email to sage-support+unsubscr...@googlegroups.com. Visit this group at http://groups.google.com/group/sage-support?hl=en.
