const references in c++ templates

Question

In a C++ template with the generic type T, I can use

const T &

to get a reference to a constant T. However, if now T itself is a reference

Answer 1

I have encountered the very same problem. It seems that the '&' type conversion operator binds stronger than the 'const' qualifier. So when we have this code:

template
void fun(const t i)
{
}

fun();

the function ends up with type void(int&), not the expected void(const int&).

To solve this problem, I have defined this template:

template struct constify { typedef t type; };
template struct constify { typedef const t& type; };

Now define your function as:

template
void fun(typename constify::type i)
{
}

fun();

The instantiated function will have the type void(const int&), as needed.