Hi Michel, Akira, I think simpler solution would be to add range support for boost::optional in additional header (e.g. <boost/range/range/optional.hpp>). i.e. boost::optional will become random access range. // OK #include <boost/range/range/optional.hpp> for (T x : r | optional_front()) { std::cout << x << std::endl } // also OK if (optional<T> x = r | optional_front()) { std::cout << x.get() << std::endl; } // another example: #include <boost/range/range/optional.hpp> optional<int> x = 100; assert(boost::size(x) == 1); optional<int> y = boost::none; assert(boost::size(y) == 0); Thanks. 2013/6/6 Akira Takahashi <faithandbrave@gmail.com>:
Hi Michel,
2013/6/6 Michel Morin <mimomorin@gmail.com>
Akira Takahashi wrote:
My Boost.Range Extension has `front` accessor.
"Range Access" adaptors in your extensions are interesting. For the consistency of range adaptors, shouldn't `front` adaptor return `single` range?
I see. `optional_front` usage is following:
if (optional<T> x = r | optional_front()) { std::cout << x.get() << std::endl; }
If `front` return signle range, the usage is following:
for (T x : x | front) { std::cout << x << std::endl; }
If `front` is error, the return value is empty range. I think single range approach is better. However, I think now `front` and `optional_front` is useful.
I would like to add `optional_front` and `front_range`.
Thanks! Akira
-- ' Yusuke Ichinohe ' yusuke.ichinohe@gmail.com