Re: floor problems
- To: mathgroup at smc.vnet.net
- Subject: [mg8239] Re: [mg8113] floor problems
- From: sergio at scisun.sci.ccny.cuny.edu (Sergio Rojas)
- Date: Thu, 21 Aug 1997 21:16:56 -0400
- Organization: City College Of New York - Science
- Sender: owner-wri-mathgroup at wolfram.com
Hi, Using: In[7]:= $Version Out[7]= DEC OSF/1 Alpha 2.2 (September 9, 1994) In[8]:= Floor[(.7 67 10)] Out[8]= 469 In[9]:= Floor[(67 10 .7)] Out[9]= 469 In[10]:= (.7 67 10) - (67 10 .7) Out[10]= 0. Rojas E-mail: sergio at scisun.sci.ccny.cuny.edu Lou Talman (me at talmanl.mscd.edu) wrote: : Tom De Vries wrote: : > I had a very frustrating time trying to debug some work I was doing in : > Mathematica. I finally pared it down to a problem with the Floor : > function, and I have illustrated my concern below. I am using M 3.0 and : > a Mac computer. Does anyone have any advice or could you tell me if I : > am doing something wrong? : > : > Floor[(.7 67 10)] : > : > 469 : > : > Floor[(67 10 .7)] : > : > 468 : The problem is not with Floor, but with the fact that floating point : multiplication of real numbers of fixed length is not, in general, associative: : In[1]:= : (.7 67 10) - (67 10 .7) : Out[1]= : \!\(5.68434188608080148`*^-14\) : --Lou Talman