Aprenda Returning Lambdas | Advanced Functional Patterns

When you return a lambda from a function, C++ can often deduce the return type automatically using auto. This is convenient and keeps your code concise. However, there are cases where you might want to specify an explicit return type, such as std::function, for greater flexibility.

Using std::function as the return type allows you to return any callable object matching the signature, not just a specific lambda. This can be helpful if you want to change the implementation later, or if you need to store different types of callables in a container or pass them around in your code. However, using std::function may introduce some overhead compared to using auto-deduced lambdas directly, so you should choose the approach that best fits your needs.

main.cpp


              12345678910111213141516171819202122
            
#include <iostream>
#include <functional>

// Function returning a lambda that multiplies by a captured factor
auto make_multiplier(int factor) {
    // The lambda captures 'factor' by value
    return [factor](int x) { return x * factor; };
}

int main() {
    // Create a multiplier that multiplies by 5
    auto times_five = make_multiplier(5);

    std::cout << "3 * 5 = " << times_five(3) << std::endl; // Output: 15

    // Using std::function as the return type
    std::function<int(int)> times_ten = make_multiplier(10);
    std::cout << "4 * 10 = " << times_ten(4) << std::endl; // Output: 40

    return 0;
}

Tudo estava claro?

Obrigado pelo seu feedback!

Seção 3. Capítulo 2

Pergunte à IA

Pergunte o que quiser ou experimente uma das perguntas sugeridas para iniciar nosso bate-papo

Suggested prompts:

Can you give an example of returning a lambda with auto and with std::function?

What are the performance implications of using std::function versus auto?

When should I prefer std::function over auto for returning callables?

Deslize para mostrar o menu

main.cpp


              12345678910111213141516171819202122
            
#include <iostream>
#include <functional>

// Function returning a lambda that multiplies by a captured factor
auto make_multiplier(int factor) {
    // The lambda captures 'factor' by value
    return [factor](int x) { return x * factor; };
}

int main() {
    // Create a multiplier that multiplies by 5
    auto times_five = make_multiplier(5);

    std::cout << "3 * 5 = " << times_five(3) << std::endl; // Output: 15

    // Using std::function as the return type
    std::function<int(int)> times_ten = make_multiplier(10);
    std::cout << "4 * 10 = " << times_ten(4) << std::endl; // Output: 40

    return 0;
}

Tudo estava claro?

Obrigado pelo seu feedback!

Seção 3. Capítulo 2