4. About comparisons
Outcome doesn't implement comparisons between Outcomes. He pretend that we don't need them.
I don't pretend we don't need them. I say that people who store Expected in an associative map need their head examined. And if they really, really want to, they can supply a custom comparison function to the map. We don't need default ordering operators if it means losing implicit conversion and creating yet more needless boilerplate for end users.
5. About the exception to throw
std::experimental::expected throw bad_expected_access<E>. I adopted the design of optional and bad_optional_access
We could have as well a bad_expected_access_base class as Outcome has.
My question is why don't throw directly E?
Throwing types without a vtable is punished badly in optimisation by some compilers e.g. GCC. Before you ask, no I don't know why. Throwing types not derived from std::exception I think that ship sailed from C++ a long time ago. I think WG21 would vote against it. Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/