Re: inconsistency with Inequality testing and Floor
- To: mathgroup at smc.vnet.net
- Subject: [mg59940] Re: inconsistency with Inequality testing and Floor
- From: snoofly <snoofly at snoofly.com>
- Date: Fri, 26 Aug 2005 04:53:29 -0400 (EDT)
- References: <dek8a1$aao$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Brett Patterson wrote: > I have observed the following strange behaviour: > > ---------------------- > In[1]:= x = 1.0 - 10^-($MachinePrecision) > > Out[1]= 1. > > In[2]:= x >= 1 > > Out[2]= True > > In[3]:= Floor[x] > > Out[3]= 0 > ---------------------- > > It seems that the inequality test and Floor use different numerical > methods. > I think this behaviour is inconsistent. > If the test "x >= 1" evaluates to True, then Floor[x] should evaluate > to 1. > > Can anyone shed any light on this? > > Regards, > Brett Patterson > > School of Physics, University of Western Australia; and > Institute of Photonics, University of Strathclyde, Scotland > Interesting. On my computer: $MachinePrecision 15.9546 1 - 10^-13.84908041702 >= 1 False 1 - 10^-13.84908041703 >= 1 True I wonder what the significance of this number is..