C++ std::function (C++11) 🎯

Welcome to our deep dive into C++'s std::function! This powerful tool is part of the C++11 standard library, making it easier to work with functions as first-class citizens. Let's explore what std::function is, why you might need it, and how to use it in practice.

What is `std::function`? 📝

std::function is a template class that can hold any callable object such as functions, functors, lambdas, and bind expressions. It acts as a polymorphic function object, allowing you to store and invoke functions at runtime.

Why use `std::function`? 💡

Function Polymorphism: std::function enables you to treat different functions as the same type, making it easier to write generic code.
Function Container: Store and invoke functions at runtime, simplifying callback implementations and event-driven programming.
Template Parameterized: Use std::function with any function signature, making it versatile and reusable in various contexts.

Basic Usage 💡

Let's create a simple example to demonstrate how to use std::function:

cpp

#include <iostream>
#include <functional>

void print(const std::string& message) {
    std::cout << message << std::endl;
}

int main() {
    // Create an std::function object holding the print function
    std::function<void(const std::string&)> myFunction = print;

    // Invoke the function through the std::function object
    myFunction("Hello, World!");

    return 0;
}

Advanced Examples 💡

Functor Example

Here's an example where we create a simple functor and use std::function to store and invoke it:

cpp

#include <iostream>
#include <functional>
#include <vector>

struct Square {
    int operator()(int number) {
        return number * number;
    }
};

int main() {
    std::vector<std::function<int(int)>> numbers;

    // Add our Square functor to the vector
    numbers.push_back(Square());

    // Invoke the functor through the std::function
    for (const auto& func : numbers) {
        std::cout << func(5) << std::endl;
    }

    return 0;
}

Variadic Template Function Example

This example demonstrates a variadic template function that takes a variable number of arguments and returns the sum using std::function:

cpp

#include <iostream>
#include <functional>
#include <cstdarg>

template<typename... Args>
auto sum(Args... args) {
    std::function<int()> sumFunction = [=]() {
        int total = 0;
        ((total += args), ...);
        return total;
    };
    return sumFunction();
}

int main() {
    std::cout << sum(1, 2, 3, 4, 5) << std::endl;

    return 0;
}

C++ std::function (C++11) 🎯

C++ std::function (C++11) 🎯

What is std::function? 📝

Why use std::function? 💡

Basic Usage 💡

Advanced Examples 💡

Functor Example

Variadic Template Function Example

Quiz 💡

What is `std::function`? 📝

Why use `std::function`? 💡