Hi, Related to this message: John Maddock wrote:
Even if the library doesn't provides an approach that works to define all the concepts, it has a lot of useful things. I also suggested to Terje at least to add the mpl and type traits extensions of the library.
Agreed - in fact I don't see why we can't just add the new traits direct to the type_traits library?
Certainly if someone would like to package these up as direct additions to type_traits (so I don't have to do much!) then I'd certainly look favorably on adding them.
and especially related to the function_traits of the type_traits library. Is there any interest in class member function introspection? According to the current documentation, "function_traits is intended to introspect only C++ functions of the form R (), R( A1 ), R ( A1, ... etc. ) and not function pointers or class member functions.". We have, in our work on Boost.Geometry, the need to have the function_traits also working on class member functions. We first had defined a specific meta-function, only for the purpose of concept-checking. Bruno suggested that using function_traits we can avoid that. So we need it to work on member functions. I did some experiments and it is possible to let function_traits checking member functions as well, and it is easy to incorporate into function_traits. It can then be called, for a member function called "apply" of a (template)class called Strategy, like this: typedef typename boost::function_traits<typename BOOST_TYPEOF(&Strategy::apply)>::arg1_type ptype1; for the first argument (in our case a point type, which is then used in the concept-checking using BCCL, to check if it fulfills the point concept and to feed into this same apply method). Adding member function support only needs two relatively simple additions: 1) a specialization for member functions, like this (here only for a const function with 2 parameters) template <typename Class, typename R, typename T1, typename T2> struct function_traits_helper<R (Class::*) (T1, T2) const> { BOOST_STATIC_CONSTANT(unsigned, arity = 2); typedef R result_type; typedef T1 arg1_type; typedef T2 arg2_type; }; 2) the boost::add_pointer call in function_traits should be avoided for member functions, this can be solved by using a meta-function there: template<typename Function> struct function_traits : public detail::function_traits_helper < typename mpl::if_ < boost::is_member_function_pointer<Function>, Function, typename boost::add_pointer<Function>::type >::type > {}; Experiments are here: http://codepad.org/Qw4Uf1aG So I have a prototype, it seems to work fine and can easily be extended and incorporated. Is there more interest in it, and do the type_traits maintainers find this a good idea? Of is it already somewhere else within Boost (or planned)? Regards, Barend