Boost logo

Boost :

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

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

always works

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

so you are always safe to use that.



Paul A. Bristow,
Prizet Farmhouse, Kendal LA8 8AB  UK
+44 1539 561830  07714330204

Boost list run by bdawes at, gregod at, cpdaniel at, john at