c++之类包含

类的包含（称为has A）是程序设计中一种软件重用技术。即定义一个新的类时，通过编译器把另一个类 “抄”进来。

当一个类中含有已经定义的类类型成员，带参数的构造函数对数据成员初始化，须使用初始化语法形式。

构造函数 ( 变元表 ) : 对象成员1( 变元表 ) , … , 对象成员n ( 变元表 ) ；

#include <iostream>
#include <cmath>
using namespace std;
#include <string>

//用类包含计算两点之间的距离
class Point{
public:
    Point(double x,double y){
        this->x = x;
        this->y = y;
    }
    Point(Point& p){
        cout <<"	copy_constract" <<endl;
    }
    double getX(){
        return x;
    }
    double getY(){
        return y;
    }
private:
    double x,y;
};
class Distance{
public:
    Distance(Point dp1,Point dp2):p1(dp1),p2(dp2){
        double x = dp1.getX()-dp2.getX();
        double y = dp1.getY()-dp2.getY();
        dist = sqrt(x*x + y*y);
    }
    double getDist(){
        return dist;
    }
private:
    Point p1,p2;
    double dist;
};

void main(){
    Distance d(Point(3.1,5.7),Point(4.7,6.8));
    cout << d.getDist() << endl;
}

#include <iostream>
#include <cmath>
using namespace std;
#include <string>

//用类包含计算两点之间的距离
class Point{
public:
    Point(double x,double y){
        this->x = x;
        this->y = y;
    }
    Point(Point& p){
        cout <<"	copy_constract" <<endl;
    }
    double getX(){
        return x;
    }
    double getY(){
        return y;
    }
private:
    double x,y;
};
class Distance{
public:
    Distance(Point dp1,Point dp2):p1(dp1),p2(dp2){
        double x = dp1.getX()-dp2.getX();
        double y = dp1.getY()-dp2.getY();
        dist = sqrt(x*x + y*y);
    }
    double getDist(){
        return dist;
    }
private:
    Point p1,p2;
    double dist;
};

void main(){
    Distance d(Point(3.1,5.7),Point(4.7,6.8));
    cout << d.getDist() << endl;
}