On Fri, 07 Feb 2003 12:48:13 +0100, John Maddock wrote:
>>Why can't I see them?? Look at: > > OK the implementation is: > > BOOST_STATIC_CONSTANT(bool, value = > (::boost::type_traits::ice_and< > ::boost::type_traits::ice_not< ::boost::is_union<T>::value > >::value, ::boost::type_traits::ice_not< > ::boost::is_scalar<T>::value >>::value, > ::boost::type_traits::ice_not< ::boost::is_array<T>::value > >::value, ::boost::type_traits::ice_not< > ::boost::is_reference<T>::value>::value, > ::boost::type_traits::ice_not< ::boost::is_void<T>::value > >::value, ::boost::type_traits::ice_not< > ::boost::is_function<T>::value >>::value > >::value)); > > Note the is_scalar: this takes care of int's floats, pointers and member > pointers. After thinking about it longer, I still think that there is a problem. The code seems "twisted" to me. Let me try to explain it, I start by some observations (all for the case of BOOST_TT_HAS_CONFORMING_IS_CLASS_IMPLEMENTATION not being set): is_scalar is based on 3.9/10, which says that enums are scalars. Currently, is_scalar doesn't detect enums. is_class needs is_scalar is_enum needs is_class or it will detect classes which are convertible to int as enums. I think we should still consider that we try to provide a conforming is_class implementation for as much compilers as possible. We should also consider to fix is_scalar. There are some further problems, e.g. is_class< int( int ) >::value fails to compile instead of giving me 'false'. I have to find a solution, but it surely exists. A last general question: It seems to me that the boost type-traits are a mixture of two very different concepts: One concept is that of a classic "utility library". This means, that it provides things I can use when I like, but they don't affect my code in general. The other concept is that of a "framework". In order to use is_union, has_* and some other functions, I have to flag my classes, that means I have to write my code in a "boost-friendly" way in order to make it work. I think that it might be worth to make a very clear distinction between these two parts. Comments? Regards, Daniel _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
