"Tobias Schwinger" <tschwinger@neoscientists.org> wrote in message news:ckbu5h$acq$1@sea.gmane.org...
Alexander Nasonov wrote:
I have one addition to '[type_traits] "member_function_pointer_traits" ?' thread started long time ago (29 Jul 2004) by Tobias Schwinger. Is it makes sense to modify as_sequence to convert function type into a sequence? Eg: as_sequence<R (T0,T1)> ---> vector<R,T0,T1> as_sequence<R(*)(T0,T1)> ---> vector<R,T0,T1> as_sequence<R(&)(T0,T1)> ---> vector<R,T0,T1>
as_sequence<R(C::*)(T0,T1)> ---> vector<R,C,T0,T1>
as_sequence<R(T0,T1)> reads great, but this would add a lot to the complexity of 'as_sequence':
First we have to idenitify if T is some sort of function (ptr/ref) type. Although there are ways to detect (not decompose, that is) functions and even member function pointers without using an unrolled cascades of specializations for different function arities, it requires a very standard compliant compiler. As we need to decompose the type and wrap its components into a vector in case it turns out to be a function anyway, we will instantiate one of these (more than 100) specializations.
I don't understand why this would be hard. Here's how I would do it: template<typename F> struct as_sequence_non_member { typedef typename mpl::push_front< typename function_arguments< F >::type, typename function_result< F >::type >::type type; }; template<typename F> struct as_sequence_member { typedef typename mpl::push_front< typename function_arguments< F >::type, typename function_class< F >::type >::type result; typedef typename mpl::push_front< result, typename function_result< F >::type >::type result; }; template<typename F> struct as_sequence : mpl::if_< is_member_function_pointer<F>, as_sequence_member<F> as_sequence_non_member >::type { }; Last night I realized I needed the ability to manipulate function types as sequences, so I wrote a small library to do it. I just finished documenting it: http://home.comcast.net/~jturkanis/function_traits/ It differs from your library as follows: - it splits up the metafunction signature into several metafunctions - it allows function types to be constructed from sequences - it doesn't handle volatility. It's not really meant to compete with your proposal -- I wrote it for a project I am currently working on. However, I'd like to know your opinion about it. Best Regards, Jonathan