模板函数如何"知道"作为模板参数给出的数组的大小？

#include<iostream>
#include<array>

template<typename T, std::size_t N>
void print_array(const std::array<T, N>& arr) {
    std::cout << "Array size: " << N << std::endl;
    for (std::size_t i = 0; i < N; ++i) {
        std::cout<< arr[i] << ' ';
    }
    std::cout<< std::endl;
}

int main() {
    std::array<int, 5> arr = {1, 2, 3, 4, 5};
    print_array(arr);
    return 0;
}

#include<iostream>
#include<array>
#include <type_traits>

template<typename T, std::size_t N>
void print_array(const std::array<T, N>& arr) {
    std::cout << "Array size: "<< std::extent<std::array<T, N>>::value<< std::endl;
    for (std::size_t i = 0; i < N; ++i) {
        std::cout<< arr[i] << ' ';
    }
    std::cout<< std::endl;
}

int main() {
    std::array<int, 5> arr = {1, 2, 3, 4, 5};
    print_array(arr);
    return 0;
}