[boost] Re: Re: Nuemric Conversion review

From: Fernando Cacciola (fernando_cacciola_at_[hidden])
Date: 2003-12-20 20:13:41

"Paul A. Bristow" <boost_at_[hidden]> escribió en el mensaje
news:AHEJIHEOOOBMJPAGPLIPCEIHENAA.boost_at_hetp.u-net.com...
>
>
> | -----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".
>
Right

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

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

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

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

Fernando Cacciola
SciSoft