El 14/01/2015 a las 20:58, John Maddock escribió:
I'm going to throw this out there to see what folks think:
In a branch called "Version2", see https://github.com/boostorg/type_traits/tree/Version2 is a partially rewritten type_traits lib: it doesn't yet contain all the traits of the old one, but there's a pretty good selection to test.
Very nice.
The main pros for this version are:
1) Zero dependencies other than Boost.Config.
We still have Boost.PP.
4) Substantially reduced #includes - the aim is that all files should include only what they need and no more - with what's needed determined by the actual implementation variant when appropriate. There were also a lot of spurious #includes left over from old workarounds no longer used.
For "is_function", you might test (I could help once things are stabilized) another approach that could avoid the use of Boost.PP: //For a function to pointer an lvalue of function type T //can be implicitly converted to a prvalue //pointer to that function. This does not apply to //non-static member functions because lvalues //that refer to non-static member functions do not exist. template <class T> struct is_reference_convertible_to_pointer { struct twochar { char dummy[2]; }; template <class U> static char test(U*); template <class U> static twochar test(...); static T& source(); static const bool value = sizeof(char) == sizeof(test<T>(source())); }; //Filter out: // - class types that might have implicit conversions // - void (to avoid forming a reference to void later) // - references (e.g.: filtering reference to functions) // - nullptr_t (convertible to pointer) template < class T , bool Filter = is_class_or_union<T>::value || is_void<T>::value || is_reference<T>::value || is_nullptr_t<T>::value > struct is_function_impl { static const bool value = is_reference_convertible_to_pointer<T>::value; }; template <class T> struct is_function_impl<T, true> { static const bool value = false; }; template <class T> struct is_function : is_function_impl<T> {}; This could allow us to avoid the preprocessor also in "is_member_function_pointer": template <class T> struct is_member_function_pointer_cv { static const bool value = false; }; template <class T, class C> struct is_member_function_pointer_cv<T C::*> : is_function<T> {}; template <class T> struct is_member_function_pointer : is_member_function_pointer_cv<typename remove_cv<T>::type> {}; Best, Ion