Does std::variant provide functionality similar to boost::variant<>::types?

Question

boost::variant exposes its list of variant types via boost::variant<>::types, which can be conveniently used with boost::mpl::for_each. std::variant is missing such a member.

I see std::variant_alternative is provided. Can this be used to produce a type list that boost::mpl::for_each can ingest? Or does it enable a different iteration strategy?

What's the actual question? What are you trying to do? – Barry Sep 20 '19 at 12:24 — Barry, Sep 20 '19 at 12:24

Quentin · Accepted Answer · 2019-09-20T11:06:32.057

4

I'm not 100% familiar with Boost.MPL, but this should do what you're looking for:

template <class Variant>
struct mpl_types_impl;

template <class... Ts>
struct mpl_types_impl<std::variant<Ts...>> {
    using type = boost::mpl::vector<Ts...>;
};

template <class Variant>
using mpl_types = typename mpl_types_impl<Variant>::type;

See it live on Wandbox

edited Sep 20 '19 at 11:06

answered Sep 20 '19 at 10:55

Quentin

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`std::tuple` -> `std::variant` to address the question? – R2RT Sep 20 '19 at 11:04
@R2RT yep, seems like a good idea innit. *Sigh* - Edit: done, now for caffeinating that struggling brain. – Quentin Sep 20 '19 at 11:05

Does std::variant provide functionality similar to boost::variant<>::types?

1 Answers1