作业3.23

#include <iostream>using namespace std;class cylinder{private:double r;double h;public:cylinder(double x,double y){     cout<<"construting..."<<endl; r=x; h=y;}~cylinder(){cout<<"destructing..."<<endl;}double vol(){const double z=3.14;return z*r*r*h;}};int main(){cylinder c1(1,2);c1.vol();cout<<"圆柱1的体积="<<c1.vol()<<endl;return 0;}

#include <iostream>  //在类外定义构造函数using namespace std;class cylinder{private:double r;double h;public:cylinder(double x,double y);~cylinder();double vol();};cylinder::cylinder(double x,double y){     cout<<"construting..."<<endl; r=x; h=y;}cylinder::~cylinder(){cout<<"destructing..."<<endl;}inline double cylinder::vol(){const double z=3.14;return z*r*r*h;}int main(){cylinder c1(1,2);c1.vol();cout<<"圆柱1的体积="<<c1.vol()<<endl;return 0;}