How can I call an integral types base on actual type in a cpp template? For example, when the actual type is int, call INT_MAX. And when the actual type is unsigned long, call ULONG_MAX;
Of course I can just write a if-else statement, but is there any other way to do that? Or what's the best way to write this part of code?
The best standard way is to rely on the <limits> header. A template already exists that does what you want. It's std::numeric_limits with its static max function. So what you want will look like this:
auto max_int = std::numeric_limits<int>::max();