On Apr 19, 2011, at 1:03 PM, John Maddock wrote:

I'm quite sure the answer to this is no.... but are there any new language features in C++2011 that would allow the implementation of any of the following traits within the language? Thanks in advance, John.

template <class T> struct is_trivial template <class T> struct is_trivially_copyable template <class T> struct is_standard_layout template <class T> struct is_literal_type template <class T, class... Args> struct is_constructible; template <class T> struct is_default_constructible; template <class T> struct is_copy_constructible; template <class T> struct is_move_constructible; template <class T, class U> struct is_assignable; template <class T> struct is_copy_assignable; template <class T> struct is_move_assignable; template <class T> struct is_destructible; template <class T, class... Args> struct is_trivially_constructible; template <class T> struct is_trivially_default_constructible; template <class T> struct is_trivially_copy_constructible; template <class T> struct is_trivially_move_constructible; template <class T, class U> struct is_trivially_assignable; template <class T> struct is_trivially_copy_assignable; template <class T> struct is_trivially_move_assignable; template <class T> struct is_trivially_destructible; template <class T, class... Args> struct is_nothrow_constructible; template <class T> struct is_nothrow_default_constructible; template <class T> struct is_nothrow_copy_constructible; template <class T> struct is_nothrow_move_constructible; template <class T, class U> struct is_nothrow_assignable; template <class T> struct is_nothrow_copy_assignable; template <class T> struct is_nothrow_move_assignable; template <class T> struct is_nothrow_destructible; template <class T> struct underlying_type;

I believe the answer is yes, but I don't have details because I don't yet have a fully conforming C++11 compiler to check against. A key change is CWG 1170: http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#1170 which changes SFINAE to take access checking into account. libc++ (http://libcxx.llvm.org/) has an attempt at is_constructible, from which many of the other traits are derived. That being said, I'm very much looking forward to dumping libc++'s implementation of is_constructible in favor of a compiler intrinsic. :-) Howard