Quite a bit of feedback from here, from SG14 and from Reddit expressed disappointment that Outcome doesn't implement the LEWG expected<T, E>. basic_monad makes implementing a fully compliant expected<T, E> just a few hours of work, so I went ahead and added one today and you can see its reference docs at https://ned14.github.io/boost.outcome/group__expected.html. These are the known deviations from the LEWG proposal: * P0323R1 doesn't yet specify what will be done if you try accessing an expected which is valueless due to exception. We throw a bad_expected_access<void> in this situation as that seemed sensible. If the LEWG proposal decides on something different, this implementation will change to track the LEWG proposal. * unexpected_type<E> is implemented as an expected<void, E> and it lets the basic_monad machinery do the implicit conversion to some expected<T, E>. * Types T and E cannot be constructible into one another. * expected<T, E> defaults E to error_code_extended. If you don't like this, predefine the BOOST_OUTCOME_EXPECTED_DEFAULT_ERROR_TYPE macro. * The ordering operators are not implemented due to https://akrzemi1.wordpress.com/2014/12/02/a-gotcha-with-optional/ So now you get in Outcome expected<T, E>; option<T>, result<T> and outcome<T>. And the Expected implementation ought to be drop in compatible with any future C++ 20 standard. How would people prefer the Outcome tutorial to now go? Should it mention expected<T, E> at all? Or should it get its own tutorial page (which will look very similar to the tutorial for result<T>). Which order should they be in? Is expected<T, E> easier than outcomes or the other way round? Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/