Stavros Macrakis wrote: > On Sat, Dec 6, 2008 at 4:32 PM, Wacek Kusnierczyk < > [EMAIL PROTECTED]> wrote: > > >> Stavros Macrakis wrote: >> >>> On Sat, Dec 6, 2008 at 5:02 AM, Wacek Kusnierczyk < >>> [EMAIL PROTECTED]> wrote: >>> >>>> yepp, though (2/3)*3 not evaluating to 2 is again not a must, is it. >>>> >>> Why is that less a must than .3-.2 == .1? On the contrary, the computing >>> convention (and for that matter the usual scientific and engineering >>> convention) is that a decimal point signals an approximate number. >>> >> not a must, since no floating point arithmetic has to be involved here. >> >> > > Floating-point is not the issue here. Fixed point is just as bad. The > problem is that it is a binary fraction, not a decimal fraction. It is > perfectly possible to do decimal arithmetic in computers, and it is useful > for commerical, but not scientific/engineering calculations. > > yes yes, the point was that (* (/ 2 3) 3) does not require non-integer arithmetic.
>> Yes, Scheme uses standard (correctly rounded) IEEE floating point, but of >> course other cases like 15.0/22.0*22.0 are not exact. >> > > (* (/ 2.0 3.0) 3.0) is not exact either, as aren't (* (/ 2.0 2.0) 2.0) > >> and 2.0; this was a teaser ;) >> >> > > Actually, they *are* all exact in any system using IEEE floats. > not per definitionem of exactness as of r6rs, as of my understanding. (exact? 2.0) is false there. vQ ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
