On Fri, Oct 4, 2013 at 1:56 PM, Greg Laun <greg.l...@gmail.com> wrote: > Thanks Peter. I agree that infinity in RR is a big problem. For those > following the discussion, Peter updated Trac ticket #11506 to reflect this > concern and it is now marked as a critical bug.
I've added a long comment there (http://trac.sagemath.org/ticket/11506#comment:8). The issue we're discussing is a side-effect of the *bug* that RR(oo) == oo evaluates to True, but it should evaluate to False. Somebody (me?) just messed that up when implementing RR long ago. Somebody else (me?) got the same thing for CC right though. The implementation of RR and CC in Sage are a very direct wrapping of MPFR, which is the most well-thought out efficient implementation of floating point real numbers I've ever seen. It is worth visiting http://www.mpfr.org/mpfr-current/mpfr.html and searching for "infinity". -- William > > On Thursday, October 3, 2013 5:31:06 PM UTC-4, Peter Bruin wrote: >> >> Hello, >> >>> from the perspective of the Riemann sphere it's a bit odd since >>> CC(infinity,0), CC(0, infinity) and CC(infinity, infinity) are all distinct >>> in sage, giving us 3 different complex infinities. >> >> >> Here is another case of unexpected behaviour: >> >> sage: CC(I)+CC(Infinity)==CC(2*I)+CC(Infinity) >> False >> sage: CC(I+Infinity)==CC(2*I+Infinity) >> True >> >> See Trac tickets #14088, #11506 and #14857 for other reported problems >> with various infinities. >> >> Peter >> > -- > You received this message because you are subscribed to the Google Groups > "sage-devel" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sage-devel+unsubscr...@googlegroups.com. > To post to this group, send email to sage-devel@googlegroups.com. > Visit this group at http://groups.google.com/group/sage-devel. > For more options, visit https://groups.google.com/groups/opt_out. -- William Stein Professor of Mathematics University of Washington http://wstein.org -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at http://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/groups/opt_out.
