[Date Index] [Thread Index] [Author Index]
Re: Possible bug in Floor function?
It is sometimes better to simplify expressions prior to using numerical techniques. $Version "9.0 for Mac OS X x86 (64-bit) (January 24, 2013)" Off[Floor::meprec] (* Supressing error messages. This does not change the results. *) Floor[Log[10, x]] /. x -> 100 // FullSimplify // N 2. Floor[Log[10, x] /. x -> 100 // FullSimplify] // N 2. Oddly, using PowerExpand results in an integer result despite the use of N Floor[Log[10, x]] /. x -> 100 // PowerExpand // N 2 Floor[Log[10, x] /. x -> 100 // PowerExpand] // N 2 Bob Hanlon On Sat, Feb 15, 2014 at 4:02 AM, psycho_dad <s.nesseris at gmail.com> wrote: > Hi, > > I think I may have stumbled upon a possible bug in Floor. Evaluating the > following gives the correct result: > > Floor[Log[10, 100.]] > 2 > > Evaluating it with a replacement and //N gives a message and the wrong > result: > > Floor[Log[10, x]] /. x -> 100 // N > > Floor::meprec: Internal precision limit $MaxExtraPrecision = 50.` reached > while evaluating Floor[Log/Log]. >> > > 1 > > I'm on Math 9.0 + Win7, but Math 8 gives the same (wrong) result as well. > > Cheers > >