On 06/13/2017 12:38 AM, Emil Dotchevski via Boost wrote:
I'll spell it out: Noexcept + optional<> ≈ Outcome
That approximation only holds for function-calling scenarios. As I pointed out in my review, there are other use cases for Outcome. Noexcept is a bad match for these use cases, because it transports errors "out-of-band" like errno. One use case is to pass a value-or-error between threads. We already have one outcome-like feature for this: promise-future. If we want to use a different mechanism to pass the value-or-error between threads, then Outcome offers a natural solution. Another use case is to pass a value-or-error via a queue. The queue may contain several outstanding errors. In the case of Outcome, we simply push the value-or-error directly to the queue.