Ok, I see. This is a bit more complex. ;) Can you influence a type passed to numeric_limits? If yes you can do this: template<class T> struct use_decimal_limits{}; namespace std { template<class T> class numeric_limits< use_decimal_limits<T> > : boost::enable_if<boost::decimal::is_decimal_type<T>

::type {

... }; } In the scenario upon the enable_if is not required, but is a compile time check. But on the other hand if is_decimal_type<T> deals with double and float anyway you can specialize numeric_limits for those types without any enable_if derivation. Probably you need to specialize the template all const, volatile, long double etc.: template<class T> struct my_numeric_limits_impl { static T min() { return boost::decimal::decimal_limits<T>::min(); } }; namespace std { template<> class numeric_limits<float> : public my_numeric_limits_impl<float> {}; template<> class numeric_limits<double> : public my_numeric_limits_impl<double> {}; } Maybe someone will suggest some better ways -----Original Message----- From: james.jones@firstinvestors.com [mailto:james.jones@firstinvestors.com] Sent: Mittwoch, 7. März 2007 18:10 To: boost-users@lists.boost.org Subject: Re: [Boost-users] [enable_if] using enable_if to extendstd::numeric_limits? From: "Ovanes Markarian" <om_boost@keywallet.com>

Sorry,

I ment enable_if< is_decimal_type<T> >::type. The ::type will be expanded to either void or a derivable type.

Maybe I'm misunderstanding, but how can I derive std::numeric_limits from enable_if, since std::numeric_limits is already defined? I can't do this: namespace std { template <typename T> class numeric_limits : private boost::enable_if<boost::decimal::is_decimal_type<T> >::type { public: static T min() { return boost::decimal::decimal_limits<T>::min(); } }; } and I can't do this: namespace std { template <typename T> class numeric_limits<T> : private boost::enable_if<boost::decimal::is_decimal_type<T> >::type { public: static T min() { return boost::decimal::decimal_limits<T>::min(); } }; } because this is not a specialization. - James Jones Administrative Data Mgmt. Webmaster 375 Raritan Center Pkwy, Suite A Data Architect Edison, NJ 08837 _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users