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MathGroup Archive 2007

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Re: strange rounding result

  • To: mathgroup at
  • Subject: [mg80960] Re: [mg80918] strange rounding result
  • From: Curtis Osterhoudt <cfo at>
  • Date: Thu, 6 Sep 2007 05:31:02 -0400 (EDT)
  • Organization: LANL
  • References: <>
  • Reply-to: cfo at

Strange to me (although consistent with the documentation for Round, which 
states that "At midpoints, Round rounds towards even integers"). This is 
consistent with the "round-to-even" method (which I just learned about on 
Wikipedia); the new "standard". 

   Perhaps my education, which stressed "bankers' rounding" needs to be 

On Wednesday 05 September 2007 00:59:41 Chris Chiasson wrote:
> Round[9995,10]
> Round[999.5,1]
> Round[99.95,1/10]
> Round[9.995,1/100]
> Round[.9995,1/1000]
> The results of these commands are decreasing powers of ten, except the
> second to last one, which gives 999/100 on my machine. I assume it has
> something to do with the storage of floating point numbers in binary
> rather than decimal form, but I don't know. Anyway, it just seemed
> strange to me and I wanted to point it out.
> Maybe it has something to do with the "round to even" behavior? Meh.

Curtis Osterhoudt
cfo at
PGP Key ID: 0x4DCA2A10
Please avoid sending me Word or PowerPoint attachments

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