Re: [boost] variant2 - really dumb way off topic question here

sob., 23 lut 2019 o 01:12 Robert Ramey via Boost napisał(a):

On 2/22/19 9:48 AM, Peter Dimov via Boost wrote:

...

I'd like to request a formal Boost review for the Variant2 library, https://github.com/pdimov/variant2. Variant2 contains an implementation of a variant type that is an almost conforming std::variant, except it doesn't require C++17 and supports C++11 and above.

It's also never valueless and has a few other extensions.

I see optional, expected, outcome and .. (monad?) as just special cases of variant. for example

template<typename T> using optional = variant;

Why is it necessary to have all these type implemented? Can't there be some sort of "base" type which can be used to implement all these others?

I think it is about the interfaces and guarantees. optional provides .value_or(), .map() functions, and operators, like ->. Also, because it does not have to consider the assignment of mixed types its implementation is more lightweight and therefore compiles faster and introduces fewer symbols. Regards, &rzej;