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From: Paul A. Bristow (boost_at_[hidden])
Date: 2003-12-19 12:29:11

| -----Original Message-----
| From: boost-bounces_at_[hidden]
| [mailto:boost-bounces_at_[hidden]]On Behalf Of Fernando Cacciola
| Sent: Friday, December 19, 2003 2:38 PM
| To: boost_at_[hidden]
| Subject: [boost] Re: Nuemric Conversion review
|| > > > The section "Exact, Correctly Rounded and Out-Of-Range Representations"
| > > > mentions 1 ulp, but that has not been defined anywhere.
| ulp = unit in the last place
| It's the number formed by a single 1 in the mantissa.
| This definiton is independent of the exponent, so the actual
| "magnitude" of 1 ulp depends on the exponent. Its a relative quantity.

PC term for mantissa seems to "significand".

I am correct is equating this to 'lesat significant (binary) digit".

It might be helpful to give as examples what it for two doubles as example, and
what the relative quantity (ratio).

Also to note that usually significand is binary and so ulp a binary 1.

And that the soon to be standard (I think) function nextafter will produce a
value which is 1 ulp more or less.


Paul A Bristow, Prizet Farmhouse, Kendal, Cumbria, LA8 8AB UK
+44 1539 561830 Mobile +44 7714 33 02 04

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