Input Validation for Generic Types Using a Template Function

#include <iostream>
#include <typeinfo> //for error message in inVal(T)
using namespace std;

/*==========================
sum is a template function that can accept generic types and return
the same type.
===========================*/
template <class T>
T sum(T a, T b) { return a+b; }

/*==========================
inVal accepts generic types by reference and performs input
validation. I often write a function like this in my programs,
so I thought, why not make a template out of it? It works for
doubles and ints.
It doesn't really work for a char. It will run,
but it won't work as intended since anything from keyboard counts
as a char. You could enter "DDDDDDDDDDD" and the program would
just write the first D to the char and leave the other D's in the
input stream.
===========================*/
template <class T>
void inVal(T &input)
{
    cin >> input;
    while(!input)
    {
        cout << "Valid input requires " << typeid(input).name() << endl;
        cin.clear();
        cin.ignore(10,'\n');
        cin >> input;
    }
    return;
}
/*==========================
Main is just for testing the functions I wrote.
Nothing special.
===========================*/
int main()
{
    int a=1,b=3;
    double a1 = 5, b1 = 6;
    char ch;
    cout << sum(a,b);
    cout << endl << sum(a1,b1);
    inVal(a);
    inVal(a1);
    inVal(ch);
    cout << endl << a;
    return 0;
}