Vicente J. Botet Escriba wrote:
What about the non-member function, so that we don't have code as x.template subset<E2...>() and we have subset<E2...>(x) instead?
You're right about the need for .template here, but I'm not sure that the need to call this function would be frequent enough to justify putting it into the outer namespace (potentially std). Leaving it as a member seems an acceptable compromise to me.
Do you have any comments about my proposed expected<T, E...>? Overall impression? Good idea? Bad, no reason to waste time with it? It is an excellent idea to implement first a never-empty variant and
Le 03/06/2017 à 18:27, Peter Dimov via Boost a écrit : then implement expected on top of it. expected<T, E...> was in the list of open points of my proposal. You have implemented it (even if still partially) :). I'll add a link to it. You have taken some deviations from the proposal that could merit discussion * missing sizeof...(E) >0 assertion * unexpected_ type is not an explicit and different type * inheritance of bad_expected_access<T> from from bad_expected_access<> :) * Additional throw_on_unexpected https://github.com/pdimov/variant2/blob/master/include/boost/variant2/expect... I suspect that this is is_move_constructible * https://github.com/pdimov/variant2/blob/master/include/boost/variant2/expect... https://github.com/pdimov/variant2/blob/master/include/boost/variant2/expect... has_error/error should be defined only if sizeof... (E) is 1 * unexpected()/error() should have a narrow contract (but this needs to be discussed in Toronto) * I know that you don't want to return by reference but unexpected can return by reference when sizeof...(E) is 1 * remap_errors seems close to what I've called adapt * https://github.com/pdimov/variant2/blob/master/include/boost/variant2/expect... return mp_with_index<mp_size<expected>>( v_.index(), [&]( auto I ) { return this->_remap_error<R>( I, f, get<I>(v_) ); }); I don't see how get<I> can work here. The same for https://github.com/pdimov/variant2/blob/master/include/boost/variant2/expect... Could explain me how the function parameter I is know at compile time? * ::then seems to be the monad::bind, could you confirm? The monadic functions were requested to be removed from the Expected proposal and managed in a general case. * Missing catch_error from the previous version of the Expected proposal. * Wondering from constructors from convertibles expected<T,E...> from expected<U, G...>. * Factories are missing * I don't know if expected<void, E...> has been implemented Thanks for working on it. Vicente P.S. While we differ on some points about narrow contracts, returning by reference I will live with the committee decision.