Re: Possible bug in Floor function?

*To*: mathgroup at smc.vnet.net*Subject*: [mg132349] Re: Possible bug in Floor function?*From*: Bill Rowe <readnews at sbcglobal.net>*Date*: Sat, 15 Feb 2014 23:14:57 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-outx@smc.vnet.net*Delivered-to*: mathgroup-newsendx@smc.vnet.net

On 2/15/14 at 4:02 AM, s.nesseris at gmail.com (psycho_dad) wrote: >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 >1 The problem isn't with Floor. The issue is simply the usage of machine precision arithmetic. That is In[11]:= RealDigits[Log[10, x] /. x -> 100 // N] Out[11]= {{1,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9},1} As you can see, the result is just slightly less than 2. So, the result Floor returns is correct