Re: inconsistency with Inequality testing and Floor
- To: mathgroup at smc.vnet.net
- Subject: [mg59942] Re: inconsistency with Inequality testing and Floor
- From: "Jens-Peer Kuska" <kuska at informatik.uni-leipzig.de>
- Date: Fri, 26 Aug 2005 04:53:31 -0400 (EDT)
- Organization: Uni Leipzig
- References: <dek8a1$aao$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Hi, $MachinePrecision is a machine floating point number and the result of x = 1.0 - 10^-($MachinePrecision) is a machine number. If you use x = 1 - 10^-(Round[$MachinePrecision]) x>=1 gives False Regards Jens "Brett Patterson" <muckle.moose at gmail.com> schrieb im Newsbeitrag news:dek8a1$aao$1 at smc.vnet.net... | | I have observed the following strange behaviour: | | ---------------------- | In[1]:= x = 1.0 - 10^-($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 |