unpack.md

Unpack

Once you finish updating your TypePack you can utilize it using a Builder.

Builder

A builder is a metaprogramming function that uses the unpacked TypePack building or calling whatever you want:

// Builder that builds a tuple.
struct TupleBuilder
{
    template<typename ... Args>
    struct Build
    {
        using type = std::tuple<Args...>;
    };
};

// Builder that builds gtest testing::Types.
struct GTESTBuilder
{
    template<typename ... Args>
    struct Build
    {
        using type = ::testing::Types<Args...>;
    };
};

Unpack

Given an existing TypePack call unpack_t with a Builder to unpack it:

using base = meta::TypePack<int, long>;

using my_tuple = base::unpack_t<TupleBuilder>;
using my_parametrized_test_types = base::unpack_t<GTESTBuilder>;