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我编写了以下代码来测试constexpr析因与正常方式评估所用的时间

#include<iostream>
#include<chrono>

constexpr long int factorialC(long int x){  return x*(x <2?1 : factorialC(x-1));}
using ns = std::chrono::nanoseconds;
using get_time = std::chrono::steady_clock;
void factorial(long int x){
    long int suma=1;
    for(long int i=1; i<=x;i++)
    {
        suma=suma*i;

    }
    std::cout<<suma<<std::endl;
}

int main(){
    long int x = 13;

    std::cout<<"Now calling the constexpr"<<std::endl;
    auto start1 = get_time::now();
    std::cout<<factorialC(x)<<std::endl;
    auto end1 = get_time::now();

    std::cout<<"Now calling the normal"<<std::endl;
    auto start2 = get_time::now();
    factorial(x);
    auto end2 = get_time::now();
    std::cout<<"Elapsed time for constexpr is "<<std::chrono::duration_cast<ns>(end1-start1).count()
    <<" Elapsed time …