MaximYanchenko wrote:
This simple example doesn't compile with GCC 4.4 + Boost 1.46.1:
#include <boost/assign/list_of.hpp> #include <boost/foreach.hpp> #include <iostream>
int main() { BOOST_FOREACH( int i, boost::assign::list_of(3)(1)(4)(1)(5) ) std::cout << i << ' '; }
error: operands to ?: have different types 'const boost::foreach_detail_::rvalue_probe<boost::assign_detail::generic_list<int> >' and 'boost::assign_detail::generic_list<int>'
I believe both Foreach and Assign library are to ease sequence creation/iteration on the fly, so they should work together smoothly.
The problem is that `generic_list<T>` (a return value of `assign::list_of()`) has very generic conversion operator: template<class Container> operator Container() const; This generic conversion operator leads to the compiler error; Containers used with `BOOST_FOREACH` should not be convertible to `rvalue_probe`. In the above case, `generic_list<T>` is convertible to `rvalue_probe< generic_list<T> >` and the compiler error happens. If SFINAE could be used with conversion operators, we could selectively disable problematic conversions. Unfortunately, we cannot apply SFINAE to conversion operators in C++03. Regards, Michel