RE: [boost] Re: Math constants - nearest values

From: Paul A Bristow (boost_at_[hidden])
Date: 2003-06-22 09:38:00

|  -----Original Message-----
|  From: boost-bounces_at_[hidden]
|  [mailto:boost-bounces_at_[hidden]] On Behalf Of 
|  Guillaume Melquiond
|  Sent: 21 June 2003 23:51
|  To: Boost mailing list
|  Subject: Re: [boost] Re: Advanced match constants scheme

|  Consequently, more than one constant out of 10000 may suffer
|  from this problem. So it is rare, but it is not impossible. 
|  It's why I was suggesting that a library should provide a 
|  mean to know if a number representing a constant is the 
|  nearest or not.

One constant out of 10000 seems a rather small risk.

Can't we just check that all the constants we offer are in fact the
nearest?

Since very few contain many zeros, I think I am prepared to wager a few
beers on this one!

So does this mean that the presentation function will use the 'exactly
representable' decimal digits appropriate for the floating point format
(choice of 5) and for the FP type float, double, long double to give to
the compiler to use?

Paul

PS How do we check? Does it depend on the FP format?