Hi, On Sun, Feb 22, 2009 at 2:23 PM, Fabian Seoane <fabian.seo...@gmail.com> wrote: > > > On Sun, Feb 22, 2009 at 12:30 PM, Freddie Witherden <fred...@witherden.org> > wrote: >> >> Hi all, >> >> I am interested if there are currently any plans to add some form of >> precision tracking for variables, be it through sympy or mpmath. The current >> implementation will more than happily compute sin(0.50) to 100+ decimal >> places if asked, even though the argument is only accurate to two decimal >> places. > > hi Freddie. Currently you can set the precission (not globaly) with > evalf(precission). For example: > >>>> sin(1).evalf(100) > 0.8414709848078965066525023216302989996225630607983710656727517099919104043912 > 396689486397435430526959
Yes, but what Freddie means is that: In [2]: sin(S(0.50).evalf(2)).evalf(100) Out[2]: 0.4794255386042030002732879352155713880818033679406006751886166131255350002878 148322096312746843482691 Should not return 100 places, if 0.50 is only know to 2 decimal places. > > Hope it helps > >> >> In Mathematica this feature is implemented as follows: >> In: N[Sin[SetPrecision[0.50, 2]], 100] >> Out: 0.48 >> >> Notice how even though the sine of 0.5 was requested to 100 places of >> accuracy it was only given to two as that is the maximum allowed by the >> input. Naturally combing of numbers of various precisions is also handled >> automatically. >> >> Something like this would be very useful for Sympy and would make >> scientific calculations a lot easier. Thanks for reporting it. I think this is should be implemented, either in mpmath or sympy. Fredrik, what do you think about it? Ondrej --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "sympy" group. To post to this group, send email to sympy@googlegroups.com To unsubscribe from this group, send email to sympy+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sympy?hl=en -~----------~----~----~----~------~----~------~--~---
