Re: [boost] [variant2] Review of Variant2 started today : April 1 - April 10

On 4/2/19 6:43 AM, Peter Dimov via Boost wrote:

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Andrey Semashev wrote:

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Also, IMHO, it's better to have libraries more focused and fine grained. > Why not have `expected` as a separate library?

expected is basically a variant, with a slightly different interface.

To expand on that a bit... to implement expected you need an underlying variant. You can either implement your own ad-hoc one, which is a duplication of work; or you could use an existing variant, but then you inherit its properties and have to reflect those in the specification of `expected`. For instance, if the variant can be valueless, you need to figure out what to do in `expected` when it gets into that state.

For those reasons, it makes most sense to develop `variant` and `expected` in parallel, as parts of the same library.

I'm thinking more of variant. Then expected, etc become "use cases" rather than first class library types. Robert Ramey

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