2007/1/16, Matthias Schabel <boost@schabel-family.org>:
Not impossible, just add another layer of indirection:
template<typename T1,typename T2> class quantity : public quantity_impl< typename mpl::if_< is_unit<T1>,T2,T1
::type, typename mpl::if_< is_unit<T1>,T1,T2 ::type {};
This is intriguing, but I'm not sure how one would enable a default template argument on just the value_type... Any ideas?
template<typename T1,typename T2=double> struct quantity : public ... { }; Using quantity, you would then get a compilation error if you tried using quantity<double>, because then both T1 and T2 would evaluate to double... Alternatively: template<typename T1,typename T2=double> struct quantity { //Implementation of quantity here, T1 is the value type, T2 is the unit type. }; template<typename T1> struct quantity<T1,double> : public quantity<double,T1> {}; Peder
Matthias
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