| -----Original Message----- | From: boost-bounces@lists.boost.org | [mailto:boost-bounces@lists.boost.org] On Behalf Of Gennadiy Rozental | Sent: 16 March 2005 14:18 | To: boost@lists.boost.org | Subject: [boost] Re: Re: No tests on como? | | > | template<typename T> | > | struct print_log_value { | > | void operator()( std::ostream& ostr, T const& t ) | > | { | > | | set_log_precision<std::numeric_limits<T>::is_specialized && | > | std::numeric_limits<T>::radix == 2>::_( ostr ); | > | | > | ostr << t; | > | } | > | }; | > | | > | > And for a UDT it relies on a specialization being provided for | > numeric_limits. | | > For UDT you could provide your own specialization for print_log_value; | > For example, for NTL, a popular collection of very high | > precision types, no specialization is provided for numeric_limits. | | Well, then default one is going to be used. Indeed, I have encouraged the author Victor Shoup, to specialise numeric_limits for NTL. | | > And if radix is something funny like 10, this formula | > | > 2 + std::numeric_limits<T>::digits * 301/1000 | > | > is wrong. | | As you could see above I apply this formula only if radix ==2 Agreed. | > So I think you need a fall-back default precision. | > | > It could be the default 6, | | Are you saying that I need to set a precision to fixed value 6? Why? Only that if T isn't specialized or radix != 2, then the stream default precision will apply, 6 for floats, unless it is changed elsewhere, which might be helpful because it easily leads to apparently nonsensical reports like 1.23456 != 1.23456 (where the difference is smaller, perhaps only 1 least significant bit, when you would might precision 17 to avoid a similar problem). Perhaps a global MACRO value could allow users to chose? For some, the clutter of 17 decimal digits would be intolerable - they would rather put up with the "1.23456 != 1.23456" reports. For others, seeing all the digits is essential to understanding the log. Paul Paul A Bristow Prizet Farmhouse, Kendal, Cumbria UK LA8 8AB +44 1539 561830 +44 7714 330204 mailto: pbristow@hetp.u-net.com