Re: [boost] [outcome] To variant, or not to variant?

Niall Douglas wrote:

3. User wants to write functional programming logic using the basic vocabulary of Maybe, Either and i/o monads and basic operators of bind, fmap, do etc and probably some subset or refinement of Hana for the collections monads, though my GSoC student may be making the Ranges TS a choice here as well later this summer.

All-narrow observers make sense for this use case as the monadic operators ensure your function will never be called with the wrong state.

There's no need for narrow (value) observers when using the monadic interface; it's all wide and since you get the value directly, you don't need to observe it.