On Friday, September 21, 2012 11:34:50 AM UTC-4, William wrote: > > On Fri, Sep 21, 2012 at 7:53 AM, kcrisman <kcri...@gmail.com <javascript:>> > 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 <javascript:>> > > 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. > > >
Yeah, that's what I had figured for "research uses", but I'm surprised that no "pedagogical use" case had come up before. Does that mean you'll be the one fixing it? ;-) -- 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.
