c++17 auto非类型模板参数

//用auto非类型模板参数
#include <iostream>
using namespace std;
template<auto c>
auto foot()
{
    cout << c << endl;
    return c;
}
int main4()
{
    foot<312>();
    int m = 12;
    switch (m)
    {
    case 0:
        cout << "switch0" << endl;
        [[fallthrough]];
    case 1:
        cout << "switch1" << endl;
        [[fallthrough]];
    case 2:
        cout << "switch2" << endl;
        [[fallthrough]];

    default:
        cout << "default" << endl;
        [[fallthrough]];
        break;
    }
    //if中嵌入表达式
    if (int m = 23; m > 24)
    {
        cout << "m<<" << m << endl;
    }
    //相比较c++ 11 constexptr 扩展作用范围
    if constexpr (constexpr int m = 23; m < 2433)
    {

    }

    return 0;
}