Re: floor problems
- To: mathgroup at smc.vnet.net
- Subject: [mg8228] Re: floor problems
- From: bruck at pacificnet.net (Ronald Bruck)
- Date: Tue, 19 Aug 1997 21:12:09 -0400
- Organization: Univ of Southern Calif
- Sender: owner-wri-mathgroup at wolfram.com
In article <5sos4i$gsq at smc.vnet.net>, Tom <toad at planet.eon.net> wrote: :Hello Mathematica users. : :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 Yes. Floating-point multiplication is not associative. If you set x = .7 67 10 y = 67 10 .7 and evaluate x-469 and y-469 you'll see that x is exactly 469 and y isn't. Look at the bit patterns to see why. This is with binary floating-point arithmetic, of course. --Ron Bruck Now 100% ISDN from this address