Question

I know this is because the return type of the template function is same as that of the first argument (T).
How can I modify this template so that, it behaves correctly in all cases?

#include <iostream>
using namespace std;
template <typename T, typename U>
T max(T x, U y)
{
    return x>y ? x : y;
}

int main()
{
    cout<<max(17.9,17)<<"\n";
    cout<<max(17,17.9)<<"\n";
}

Output:

17.9  
17

Answer 1

The output is correct. You never specified a type, so complaining that it didn’t use the type you wanted it to use is not reasonable. If you want a specific type, you have to ensure both parameters are that type.

You could cast the first parameter to a double. Or you could specifically invoke
max<double, double>. You could also specialize max<int, double> and similar combinations if you really, really wanted to.