std::forward

 std::forward is a C++ utility function primarily used for "perfect forwarding," a technique that allows a function template to forward arguments to another function while preserving their value category (lvalue or rvalue). This is achieved by conditionally casting the argument to an rvalue only if it's originally an rvalue. 

Here's a breakdown of how std::forward is used and why it's important:

1. Perfect Forwarding:

     Forwarding references:

• std::forward is used in conjunction with forwarding references (denoted by T&&) in function templates. A forwarding reference can bind to both lvalue and rvalue arguments. 
• Preserving value category:
• When an argument is passed to a function with a forwarding reference, std::forward ensures that if the argument is originally an lvalue, it remains an lvalue when forwarded. If it's originally an rvalue, it becomes an rvalue when forwarded
• Avoiding unnecessary copies or moves:
• By preserving the original value category, std::forward allows for efficient handling of both lvalue and rvalue arguments, potentially avoiding unnecessary copies or moves. 
• 
  

Please use this below link to debug further.

#include <iostream>

#include <utility>

void print(int& l) {

std::cout << "Lvalue: " << l << std::endl;

}

void print(int&& r) {

std::cout << "Rvalue: " << r << std::endl;

}

template <typename T>

void wrapper(T&& arg) {

print(std::forward<T>(arg)); // Perfect forwarding

}

int main() {

int x = 5;

wrapper(x); // Passes lvalue 'x' as lvalue

wrapper(5); // Passes rvalue '5' as rvalue

wrapper(std::move(x)); // Passes rvalue version of 'x' as rvalue

return 0;

}

Program returned: 0
Lvalue: 5
Rvalue: 5
Rvalue: 5