Perfect Forwarding and std::forward
Perfect forwarding is a technique in template programming that preserves the value category (lvalue or rvalue) of function arguments. std::forward is used to achieve this, enabling efficient and correct resource transfers.
main.cpp
1234567891011121314151617181920212223#include <iostream> #include <utility> #include <string> void process(const std::string& s) { std::cout << "Lvalue processed: " << s << '\n'; } void process(std::string&& s) { std::cout << "Rvalue processed: " << s << '\n'; } template<typename T> void wrapper(T&& arg) { process(std::forward<T>(arg)); } int main() { std::string hello = "Hello"; wrapper(hello); // Passes lvalue wrapper(std::string("Hi")); // Passes rvalue }
In the code above, std::forward ensures that lvalues are passed as lvalues and rvalues as rvalues, allowing move semantics to work correctly in generic code.
Perfect forwarding is essential when writing wrapper or factory functions that pass arguments to other functions or constructors without losing their value category.
std::move always casts to rvalue, which can lead to unintended moves of lvalues. std::forward preserves the original value category.
Дякуємо за ваш відгук!
Запитати АІ
Запитати АІ
Запитайте про що завгодно або спробуйте одне із запропонованих запитань, щоб почати наш чат
Can you give an example of perfect forwarding in C++?
Why is preserving the value category important in template programming?
How does std::forward differ from std::move?
Чудово!
Completion показник покращився до 10Perfect Forwarding and std::forward
Свайпніть щоб показати меню
Perfect forwarding is a technique in template programming that preserves the value category (lvalue or rvalue) of function arguments. std::forward is used to achieve this, enabling efficient and correct resource transfers.
main.cpp
1234567891011121314151617181920212223#include <iostream> #include <utility> #include <string> void process(const std::string& s) { std::cout << "Lvalue processed: " << s << '\n'; } void process(std::string&& s) { std::cout << "Rvalue processed: " << s << '\n'; } template<typename T> void wrapper(T&& arg) { process(std::forward<T>(arg)); } int main() { std::string hello = "Hello"; wrapper(hello); // Passes lvalue wrapper(std::string("Hi")); // Passes rvalue }
In the code above, std::forward ensures that lvalues are passed as lvalues and rvalues as rvalues, allowing move semantics to work correctly in generic code.
Perfect forwarding is essential when writing wrapper or factory functions that pass arguments to other functions or constructors without losing their value category.
std::move always casts to rvalue, which can lead to unintended moves of lvalues. std::forward preserves the original value category.
Дякуємо за ваш відгук!
