c++函数功能 引用 & 重载 & 默认参数 & 内联

/*c++新功能小程序引用 & 重载 & 默认参数 & 内联*/#include<iostream>inline double square(double x = 2);inline double square2(double &x);int fun(int a, int b);double fun(double a, double b);int main(){double a;std::cin >> a;std::cout << square(a) << std::endl;std::cout << square() << std::endl;double & b = a;b = square2(b);std::cout << b << std::endl;std::cout << a << std::endl;int aa = 2, bb = 2;std::cout << fun(aa, bb) << std::endl;double aaa = 2.2, bbb = 2.2;std::cout << fun(aaa, bbb) << std::endl;return 0;}inline double square(double x){return x * x;}inline double square2(double &x){return x * x;}int fun(int a, int b){return a + b;}double fun(double a, double b){return a * b;}