From: Paul A Bristow (pbristow_at_[hidden])
Date: 2006-08-18 04:36:58
| -----Original Message-----
| From: boost-bounces_at_[hidden]
| [mailto:boost-bounces_at_[hidden]] On Behalf Of Deane Yang
| Sent: 17 August 2006 17:12
| To: boost_at_[hidden]
| Subject: Re: [boost] The meaning of -nan (was
| [serialization] facets for non-finite numbers)
| Paul A Bristow wrote:
| > | Paul Bristow wrote
| > | > That is indeed the *intention* - but entirely USER-DEFINED
| > | and with NO MATH
| > | > MEANING.
| > | >
| > | > NaNs are never > < or == anyway?
| > |
| > | But it tells you where how you got there doesnt it?
| > Maybe - but this is getting OT - the topic was Octonionic
| Not-A-Numbers ;-)
| Is this really off-topic? I've seen everyone assert that -nan has no
| mathematical meaning. Does this mean that there is no pfficial
| specification (whether it is "mathematically meaningful" or
| not) of how a -nan can arise as a result of an arithmetic operation?
Well the 'official' position seems entirely unclear to me with IEEE754,
IEEE754R - still unreleased, and a high degree of
non-compliance/disagreement among manufacturers and vendors.
But a NaN is a NaN, whatever the sign, only the exponent field determines
Apart from sign there are also lots of significand bits whose meaning is
I suspect that -NaN can only arise from the use of copysign on an existing
But I am confident that this whole business is 'User-Defined'.
But the ability to stream out a signed NaN and stream back in a signed NaN
is potentially VERY useful.
--- Paul A Bristow Prizet Farmhouse, Kendal, Cumbria UK LA8 8AB +44 1539561830 & SMS, Mobile +44 7714 330204 & SMS pbristow_at_[hidden]
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