Re: [boost] [serialization] How are floating point values handled?

Subject: Re: [boost] [serialization] How are floating point values handled?
From: Paul A. Bristow (pbristow_at_[hidden])
Date: 2013-08-08 12:19:29

> -----Original Message-----
> From: Boost [mailto:boost-bounces_at_[hidden]] On Behalf Of Robert Ramey
> Sent: Thursday, August 08, 2013 5:26 PM
> To: boost_at_[hidden]
> Subject: Re: [boost] [serialization] How are floating point values handled?

> But maybe it is.  In anycase it looks like I should be using max_digits10 instead of digits10+2 in
anycase.

Yes - the trouble is that not all platforms provide max_digits10 - it took 5 years before the first
ones did, and then Microsoft got one of the constants values wrong, so another couple of years
passed before anyone could use it!

BOOST_NO_CXX11_NUMERIC_LIMITS tells if you std::numeric_limits<T>::max_digits10 is NOT supported.

But the Kahan formula 

William Kahan says http://www.cs.berkeley.edu/~wkahan/ieee754status/IEEE754.PDF

always works

2 + std::numeric_limits<Target>::digits * 3010/10000;

so you are always  safe to use that.

HTH

Paul

---
Paul A. Bristow,
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[phone]  07714330204
pbristow_at_[hidden]