Initializer lists adds language-level support for the same problem assign::list_of solves. The statement: std::vector<int> vec = boost::assign::list_of(1)(2)(3); Will have the functional equivalent in C++0x: std::vector<int> vec = { 1, 2, 3}; There are some other differences, but the technical report is at http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2672.htm . Wikipedia also has some good examples in their C++0x article. On Thu, Jun 2, 2011 at 11:04 PM, asif saeed <asif.lse2@gmail.com> wrote:

Hi, Boost::assign::list_of is absolutely wonderful. I used it in my last project. I was not aware of C++0x initializer lists. Is this something something similar to Assign::List of? Could you please give me a link to it? Thanks,Asif

On Fri, Jun 3, 2011 at 9:48 AM, Travis Gockel <travis@gockelhut.com>wrote:

...

I'm moving a fairly large project over to C++0x, since it is about to be published (crosses fingers) and we need to stay up with the times. In this project, we use the wonderful boost::assign::list_of to assign collections (since initializer lists don't exist yet). We are using g++ 4.5.1 and Boost 1.46.1.

When switching to C++0x, bits of code like this break:

std::vector<int> vec; vec = boost::assign::list_of(1)(2)(3);

with the following error:

break_list_of.cpp:7:41: error: ambiguous overload for ‘operator=’ in ‘vec = ((boost::assign_detail::generic_list<int>*)boost::assign::list_of(const T&) [with T = int]().boost::assign_detail::generic_list<T>::operator() [with T = int, boost::assign_detail::generic_list<T> = boost::assign_detail::generic_list<int>, boost::assign_detail::generic_list<T>::Ty = int](((const boost::assign_detail::generic_list<int>::Ty&)((const boost::assign_detail::generic_list<int>::Ty*)(&2)))))->boost::assign_detail::generic_list<T>::operator() [with T = int, boost::assign_detail::generic_list<T> = boost::assign_detail::generic_list<int>, boost::assign_detail::generic_list<T>::Ty = int](((const boost::assign_detail::generic_list<int>::Ty&)((const boost::assign_detail::generic_list<int>::Ty*)(&3))))’ /usr/include/c++/4.5/bits/vector.tcc:156:5: note: candidates are: std::vector<_Tp, _Alloc>& std::vector<_Tp, _Alloc>::operator=(const std::vector<_Tp, _Alloc>&) [with _Tp = int, _Alloc = std::allocator<int>] /usr/include/c++/4.5/bits/stl_vector.h:336:7: note: std::vector<_Tp, _Alloc>& std::vector<_Tp, _Alloc>::operator=(std::vector<_Tp, _Alloc>&&) [with _Tp = int, _Alloc = std::allocator<int>, std::vector<_Tp, _Alloc> = std::vector<int>] /usr/include/c++/4.5/bits/stl_vector.h:357:7: note: std::vector<_Tp, _Alloc>& std::vector<_Tp, _Alloc>::operator=(std::initializer_list<_CharT>) [with _Tp = int, _Alloc = std::allocator<int>, std::vector<_Tp, _Alloc> = std::vector<int>]

The problem is that there are now multiple ways to assign to vectors (and all the other collection types). Ideally, I would replace all usage of boost::assign::list_of with C++0x initializer lists, but, alas, I am lazy. Furthermore, I think I know how to fix this (see example below) and think the Boost community would benefit from having boost::assign::list_of work in C++0x and C++.

template <typename T> struct is_initializer_list : boost::false_type { };

template <typename T> struct is_initializer_list<std::initializer_list<T> > : boost::true_type { };

template <typename T> struct wrapped_type { wrapped_type(const T& val) : _val(val) { }

template <typename TOut, // use new support for default template arguments in functions typename TPhony = typename boost::disable_if<is_initializer_list<TOut> >::type > operator TOut() const { return _val; }

private: T _val; };

I was wondering if anybody has solved this problem (or a similar one) already. I would patch it myself, but I only have g++ and clang to test it on. Also, there is a high probability that my solution is flawed in some way.

Thanks for the help! And, as always, thanks for the wonderful library.

-- - Travis Gockel

_______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

_______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

-- - Travis Gockel

On Fri, Jun 3, 2011 at 4:35 AM, Thorsten Ottosen < thorsten.ottosen@dezide.com> wrote:

We think we have a way to fix it, similar to yours.

I'm a little busy right now ... but a fix should be there soon.

-Thorsten

Any ETA on that? I'm guess it isn't going to get into 1.47, given that the freeze is on Monday. Either way, I'm glad you guys have already got me covered :-) -- - Travis Gockel