RE: [boost] Re: Maths Constants

From: Paul A. Bristow (pbristow_at_[hidden])
Date: 2001-03-26 17:39:29

k.hagan_at_[hidden]

wrote

> (The main reason why the x86 provides these "load constant"
> instructions is to support rounding modes correctly. The most
> accurate representation differs if the rounding mode is towards
> +/- infinity. In one case we want the closest value below the
> constant, and in the other case we want the closest value above it.
> No compile-time constant can reproduce this behaviour, and working
> it out at run-time is not terribly fast, at least for the "long
> double" case! We probably don't care about this. Jens might, in the
> context of his boost interval library, where he needs a pi for
> argument reduction, if I remember correctly.)

Do we want to try to produce constants which show the intervals?
(Am I right in presuming this means nearest value + the smallest binary
digit,
and minus it?)

Can't one handle this adding or substracting std::limits<double>epsilon()?

Or is it more complicated, as even?

Paul
Dr Paul A Bristow, hetp Chromatography
Prizet Farmhouse
Kendal, Cumbria
LA8 8AB      UK
[phone]
mailto:pbristow_at_[hidden]