Re: [Boost-users] boost::assign::list_of and C++0x

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 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 : boost::true_type { };

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

template ::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