std_invoke.md

std::invoke

std::invoke is a generic way to activate any callable. std::invoke takes something callable, and arguments to call it with, and does the call. std::invoke( f, args... ) is a slight generalization of typing f(args...) that also handles a few additional cases.

The advantage of using std::invoke over directly invoking a callable object is that it provides a uniform syntax that works for all callable objects. This means that you can use the same syntax to invoke a function pointer, member function, function object, or lambda, without needing to know the specific type or signature of the callable object.

void foo(int x) {
    std::cout << "foo(" << x << ")" << std::endl;
}

struct bar {
    void operator()(int x) const {
        std::cout << "bar(" << x << ")" << std::endl;
    }
};

now you can invoke them as followings:

1. Invoke a function pointer:

int x = 42;
std::invoke(foo, x);

2. Invoke a member function:

bar b;
std::invoke(&bar::operator(), b, x);

3. Invoke a function object:

std::invoke(std::function<void(int)>([](int x) { std::cout << "lambda(" << x << ")" << std::endl; }), x);