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inconsistency with Inequality testing and Floor

• To: mathgroup at smc.vnet.net
• Subject: [mg59927] inconsistency with Inequality testing and Floor
• From: "Brett Patterson" <muckle.moose at gmail.com>
• Date: Thu, 25 Aug 2005 06:34:44 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

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

• Follow-Ups:
  • Re: inconsistency with Inequality testing and Floor
    • From: Sseziwa Mukasa <mukasa@jeol.com>
  • Re: inconsistency with Inequality testing and Floor
    • From: Andrzej Kozlowski <akoz@mimuw.edu.pl>