pattern matching

#include <string>
#include <variant>

// Functor composed of a variable number of other functors
// Each inherited functor represents a different type pattern
template<typename ...Types>
struct match : Types... {
    match(Types... types) : Types{ types }... {}
    using Types::operator()...;
};

// Type deduction hint
template<typename ...Types>
match(Types...)->match<Types...>;

void foo() {
    // Variable whose type is one of { int, std::string }
    auto v = std::variant<int, std::string>{ 5 };
    std::visit(match(
            [](int a) {},
            [](const std::string &b) {}
    ), v);
}