Why is `const T&` not sure to be const?

Question

template
void f(T a, const T& b)
{
    ++a; // ok
    ++b; // also ok!
}

template
void g(T n)
{
    f(n, n);
}

int         


        

Answer 1

I know that there is already an accepted answer which is correct but just to add to it a little bit, even outside the realm of templates and just in function declarations in general...

( const T& ) 

is not the same as

( const T )

In your example which matches the first, you have a const reference. If you truly want a const value that is not modifiable remove the reference as in the second example.