On Thu, 9 Dec 2004, Thomas Lumley wrote: > On Thu, 9 Dec 2004 [EMAIL PROTECTED] wrote: > > > This is nothing to do with integers: 1e18 and 11 are doubles here. > > > > It is a result of rounding error: 1e18/11 is not representable accurately, > > and this should have been a warning to you that your calculations were > > unreasonable. > > It was -- the poster originally asked about large integer representations > and said he was planning to use other software for large integers.
Ah, but that's not in this bug report. > At the time I said that the fact %% didn't give some sort of error or > warning was a bug, and was planning to return either a warning or NA or > NaN if > abs(x1)>1/.Machine$double.eps > > -thomas I've done that (a warning) but it needed caching .Machine at C level to make it reasonably efficient. I've also done a second pass to ensure the result is within range (even if possible nonsense). > > > The C code is > > > > double myfmod(double x1, double x2) > > { > > double q = x1 / x2; > > return x1 - floor(q) * x2; > > } > > > > We can improve the answer, but what you are doing is fundamentally flawed > > and it is hard to detect whether rounding error has affected this. A > > warning rather than an error seems appropriate. > > > > If you really want to do things like this, try the gmp package (which > > seems to give the wrong answer here) or a more appropriate calculator. > > > > > > On Thu, 9 Dec 2004 [EMAIL PROTECTED] wrote: > > > >> R Developers, > >> > >> 1000000000000000000 %% 11 > >> [1] -32 > >> > >> I now understand that integers cannot be larger than > >> .Machine$integer.max, but because the above produces a result than is > >> patently wrong instead of an error, I'm reporting this as a bug. > > > > -- > > Brian D. Ripley, [EMAIL PROTECTED] > > Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ > > University of Oxford, Tel: +44 1865 272861 (self) > > 1 South Parks Road, +44 1865 272866 (PA) > > Oxford OX1 3TG, UK Fax: +44 1865 272595 > > > > ______________________________________________ > > [EMAIL PROTECTED] mailing list > > https://stat.ethz.ch/mailman/listinfo/r-devel > > > > -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel