你如何写这个模板的定义？

Question

How do you write the definition of this template?

fun<10>();// output is 10  
fun<20>();// output is 20

Answer 1

template <int32_t N>
void fun() {
    std::cout << N << std::endl;
}

It is called a non-type template parameter.

And the parameter here ( int32_t N for instance in the above example) can be one of the following types (until C++20):

1. std::nullptr_t (since C++11);

2. an integral type;

3. a pointer type (to object or to function);

4. a pointer to member type (to member object or to member function);

5. an enumeration type.

Reference: template parameter