[Boost-users] [Range] Select forward or reverse traversal at compile time?

Given a bidirectional range R, is it possible to select at compile time whether we want to iterate forwards or backwards? Below is a test app. At the commented line, I would like to transparently construct a forward or reverse range, ie either [begin(range), end(range)] or [rbegin(range), rend(range)] respectively, depending on the definition of the Reversed template parameter. Just to be clear, the desired output is: forward: abc reversed: abc I can make this work by using a functor class with partial specialisation to construct the iterator_range, using begin/end or rbegin/rend respectively. But it's a bit ugly and it would seem like something that boost range would provide anyway? (Note that boost::reverse() is NOT what I am after.) #include #include #include #include <vector> #include <iostream> template std::string Print(const Range& range) { typedef boost::iterator_range< typename boost::mpl::eval_if< Reversed, boost::range_reverse_iterator<const Range>, boost::range_iterator<const Range> >::type> IterRange; // want to convert it to a forward range here IterRange forwardRange(range); std::string result; boost::copy(forwardRange, std::back_inserter(result)); return result; } int main(int argc, char* argv[]) { using boost::assign::list_of; std::vector<char> a = list_of('a')('b')('c'); std::vector<char> b = list_of('c')('b')('a'); std::cout << "forward: " << Printboost::mpl::false_(a) << std::endl << "reversed: " << Printboost::mpl::true_(b) << std::endl; return 0; }