CODEWITHSUNDEEP
lambdac++17tag-dispatching
Andreas Loanjoe
Andreas Loanjoe

Reputation: 2399

Shortest syntax for type tag lambda dispatch in C++ 17

I am restrained to use C++17 and I want to pass a type to a lambda by passing in a type tag, which I can in the following way in C++ 20 and C++17.

template<typename T>
struct Type
{
    using type = T;
};

auto lambda20 = []<typename T>(Type<T>){
    static_assert(std::is_same_v<T, int>);
};
auto lambda17 = [](auto tag){
    static_assert(std::is_same_v<typename decltype(tag)::type, int>);
};

void test()
{
    lambda20(Type<int>{});
    lambda17(Type<int>{});
}

Is there a shorter syntax than the typename decltype(tag)::type I can use to extract the type from the type tag in C++ 17?

Upvotes: 2

Views: 158

Answers (0)

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