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C++17 in Detail: A Deep Dive

Overload

In this part we'll take a look at overloading and C++ 17 overload uses.

We'll cover the following...

With this utility you can write all lambdas for all matching types in one place:

C++
std::variant<int, float, std::string> myVariant; 
std::visit
(
  overload (
    [](const int& i) { std::cout << "int: " << i; },
    [](const std::string& s) { std::cout << "string: " << s; }, 
    [](const float& f) { std::cout << "float: " << f; }
  ),
  myVariant;
);

Currently, this helper is not a part of the Standard Library (it might be added into with C++20). Let’s see how you can implement it with the code given below.

Implementation

C++
template<class... Ts> struct overload : Ts... { using Ts::operator()...; };
template<class... Ts> overload(Ts...) -> overload<Ts...>;

The code creates a struct that ...