Question

Is the below function definition is legal or not?

T& GetMax(const T& t1, const T& t2)
{
    if (t1 > t2)
    {
        return t2;
    }
    // else 
    return t2;
}

It is written that :
“At the return statements, compiler would complain that t1 or t2 cannot be converted to non-const.”
I read it in this site : http://www.codeproject.com/Articles/257589/An-Idiots-Guide-to-Cplusplus-Templates-Part-1

Does it mean that it is illegal ,if not what else? Could you provide example of use of it?
Could you provide some clear explanation to me ?
Thanks in advance

Answer 1

Why should it be illegal? Your function can use some global state to return, while it is forbidden to return its arguments.

int& foo(const int& a, const int& b)
{
    static int c = a + b;
    return c;
}

ADDED

You cannot return one of your argument, because it will violate const constrains. You can

• return from function by value
• use non-const argument types

if returning non-const in your case would be possible, one could write

foo(5, 4) = 3;

which has no sense.

You can not also return reference to some temporary automatic variable, created inside function, as it will be destroyed, when function finished.