c++中一个重要的特点就是代码的重用，为了代码重用，有两个非常重要的手段，一个是继承，一个是组合
组合 (Composition) 指在一个类中另一类的对象作为数据成员.
在平面上两点连成一条直线, 求直线的长度和直线中点的坐标.
要求:
Dot 类:
#ifndef PROJECT5_DOT_H
#define PROJECT5_DOT_H
#include <iostream>
using namespace std;
class Dot {
public:
double x, y;
Dot(double a, double b) : x(a), y(b) {};
void show() {
cout << "x: " << x << endl;
cout << "y: " << y << endl;
};
};
#endif //PROJECT5_DOT_H
Line 类:
#ifndef PROJECT5_LINE_H
#define PROJECT5_LINE_H
#include "Dot.h"
class Line : public Dot {
private:
Dot d1;
Dot d2;
public:
Line(const Dot &d1, const Dot &d2) : Dot(0, 0), d1(d1), d2(d2) {
x = (d1.x + d2.x) / 2;
y = (d1.y + d2.y) / 2;
}
void show(){
Dot::show();
cout << "dot1: (" << d1.x << ", " << d1.y << ")" << endl;
cout << "dot2: (" << d2.x << ", " << d2.y << ")" << endl;
}
};
#endif //PROJECT5_LINE_H
main:
#include <iostream>
#include "Dot.h"
#include "Line.h"
using namespace std;
int main() {
double a, b;
cout << "Input Dot1: \n";
cin >> a >> b;
Dot dot1(a,b);
cout << "Input Dot2: \n";
cin >> a >> b ;
Dot dot2(a,b);
Line l1(dot1, dot2);
l1.show();
return 0;
}
输出结果:
Input Dot1:
1 2
Input Dot2:
4, 6
x: 2.5
y: 1
dot1: (1, 2)
dot2: (4, 0)
