On Thu, Apr 11, 2013 at 10:41 PM, Vicente J. Botet Escriba < vicente.botet@wanadoo.fr> wrote:
Le 12/04/13 06:07, Jeffrey Lee Hellrung, Jr. a écrit :
On Tue, Apr 9, 2013 at 11:02 PM, Vicente J. Botet Escriba < vicente.botet@wanadoo.fr> wrote:
Hi,
I would like to implement C++11 INVOKE on C++98 compilers.
I have a C++11 implementation on boost/thread/detail/invoke.hpp based on the one of libc++.
Could this be done or there is something that can not be done inherently?
Can you briefly describe what INVOKE does (or...should do)?
Hi,
from the standard http://www.open-std.org/JTC1/** SC22/WG21/docs/papers/2012/**n3485.pdfhttp://www.open-std.org/JTC1/SC22/WG21/docs/papers/2012/n3485.pdf
20.8.2 Requirements [func.require] 1 Define INVOKE(f, t1, t2, ..., tN) as follows: — (t1.*f)(t2, ..., tN) when f is a pointer to a member function of a class T and t1 is an object of type T or a reference to an object of type T or a reference to an object of a type derived from T;
— ((*t1).*f)(t2, ..., tN) when f is a pointer to a member function of a class T and t1 is not one of the types described in the previous item;
— t1.*f when N == 1 and f is a pointer to member data of a class T and t1 is an object of type T or a reference to an object of type T or a reference to an object of a type derived from T;
— (*t1).*f when N == 1 and f is a pointer to member data of a class T and t1 is not one of the types described in the previous item;
— f(t1, t2, ..., tN) in all other cases. 2 Define INVOKE(f, t1, t2, ..., tN, R) as INVOKE(f, t1, t2, ..., tN) implicitly converted to R
Got it.
The libc++ implementation is
// __invoke
// bullets 1 and 2
template
inline _LIBCPP_INLINE_VISIBILITY auto __invoke(_Fp&& __f, _A0&& __a0, _Args&& ...__args) -> decltype((_VSTD::forward<_A0>(**__a0).*__f)(_VSTD::forward<_** Args>(__args)...)) { return (_VSTD::forward<_A0>(__a0).*__**f)(_VSTD::forward<_Args>(__** args)...); }
[...] I glanced at your implementation in thread/detail, and noticed you had replaced the &&'s with BOOST_THREAD_RV_REF's, which I don't think is right in C++03... In C++03, you might be able to get away with defining an INVOKE (variadic) macro that does what you want...? Hmmm...thinking about it a bit, the difference between the pointer-to-member-function case and function object/pointer case makes that tricky. Maybe the best you can do in C++03 is imperfect forwarding with multiple overloads for each arity + invokable-type combination :( - Jeff