C++ function with reference argument that works for lvalues and rvalues

I would like to have a C++ function which takes an argument, that's a reference, and works for both lvalues and rvalues with the same syntax.

Take this example:

#include <iostream>
using namespace std;

void triple_lvalue(int &n)
n *= 3;
cout << "Inside function: " << n << endl;


void triple_rvalue(int &&n)
n *= 3;
cout << "Inside function: " << n << endl;


int main()
int n = 3;
triple_lvalue(n);
cout << "Outside function: " << n << endl;
triple_rvalue(5);



Output:

Inside function: 9
Outside function: 9
Inside function: 15


This code works. But I need two different functions for my cases, the first where I pass n (an lvalue) and 3 (an rvalue). I would like syntax for my function that handles both just fine, without needing to repeat any code.

n

3

Thank you!

1 Answer
1

This is what forwarding reference supposed to do. It could be used with both lvalues and rvalues, and preserves the value category of the function argument.

Forwarding references are a special kind of references that preserve
the value category of a function argument, making it possible to
forward it by means of std::forward.

std::forward

e.g.

template <typename T>
void triple_value(T &&n)
n *= 3;
cout << "Inside function: " << n << endl;



std::forward

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