Thanks for this trick. 2014-10-28 16:36 GMT+01:00 William Stein <[email protected]>:
> On Tue, Oct 28, 2014 at 8:19 AM, Christophe Bal <[email protected]> > wrote: > > Hello. > > > > I'm writing a french book about SageMathCloud and I'm looking for known > > wrong results given by Sage due to floats calculations, or due to the > method > > used. Do you know such things ? My idea is to show to new user that a > CAS or > > a numerical tool is not Math God. > > > > For my part, I really like the following one. Try it, it is funny even > if I > > know what is is the reason of the unexpected result. > > > > -------------------------- > > u = 1.0/3 > > > > for i in range(100): > > u = 4*u - 1 > > > > print u > > -------------------------- > > This is a good motivation for RIF (real interval field), which tracks > errors, e.g., > > > u = RIF(1/3) > > for i in range(100): > u = 4*u - 1 > > print u > > > The output is 0.?e44, which means no digits are known to be right. > > See [1]. > > [1] > https://cloud.sagemath.com/projects/4a5f0542-5873-4eed-a85c-a18c706e8bcd/files/support/2014-10-28-083459-funny-and-wrong.sagews > > > > > -- > 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 unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/sage-support. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
