On 6/2/17 9:22 AM, Richard Hodges via Boost wrote:
Forgive me chiming in late, but what is the semantic difference between:
enum class no_difference { _ }
expected<std::path, no_difference, std::error_code, std::exception_ptr>
and this:
using path_difference = std::variant<std::path, no_difference>; using error = std::variant<std::error_code, std::exception_ptr>;
expected<path_difference, error> return_first_diff(...);
Doesn't the latter form satisfy all concerns in that: 1. It conforms to a desirable 2-state 'value or error' KISS paradigm. 2. it contains all the information we'll ever need. 3. success code paths are now co-located, as are failure code paths. There is no need for N code-paths to cater for N states. Isn't this more maintainable?
Right. By leaving the second parameter E as a template parameter, it can contain as much state or as little state as one wants. Your formulation might be considered more heavy weight - but hey, that's up to the user - not us. Robert Ramey