实验四 继承
任务1
期中练习1
#include<iostream> #include<map> #include<string> int main() { using namespace std; map<int,char> letter{{0,'a'},{1,'b'},{2,'c'},{3,'d'},{4,'e'},{5,'f'},{6,'g'},{7,'h'},{8,'i'},{9,'j'}}; string stunum; while(cin>>stunum) { int i; for(i=0;i<stunum.size();i++) { cout<<letter[stunum[i]-'0']; } cout<<endl; } return 0; }
期中练习2
#include<iostream> #include<string> #include<map> using namespace std; void d2n(int num,int n=2) { map<int,char> letter{{10,'A'},{11,'B'},{12,'C'},{13,'D'},{14,'E'},{15,'F'}}; if(n==2) { string ans; int i=0; while(num!=0) { ans[i]=(num%2)+'0'; num=num/2; i++; } cout<<"Default:"; for(int j=i-1;j>=0;j--) { cout<<ans[j]; } cout<<endl; cout<<"Dec:\t"; for(int j=i-1;j>=0;j--) { cout<<ans[j]; } cout<<endl; } if(n==8) { string ans; int i=0; while(num!=0) { ans[i]=(num%8)+'0'; num=num/8; i++; } cout<<"Oct:\t"; for(int j=i-1;j>=0;j--) { cout<<ans[j]; } cout<<endl; } if(n==16) { string ans; int i=0; while(num!=0) { if((num%16)>9) { ans[i]=letter[num%16]; } else { ans[i]=(num%16)+'0'; } num=num/16; i++; } cout<<"Hex:\t"; for(int j=i-1;j>=0;j--) { cout<<ans[j]; } cout<<endl; } } int main() { int num; while(cin>>num) { d2n(num); d2n(num,8); d2n(num,16); } }
任务2
没有添加virtual
#include <iostream> #include <typeinfo> // definitation of Graph class Graph { public: void draw() { std::cout << "Graph::draw() : just as an interface\n"; } }; // definition of Rectangle, derived from Graph class Rectangle : public Graph { public: void draw() { std::cout << "Rectangle::draw(): programs of draw a rectangle\n"; } }; // definition of Circle, derived from Graph class Circle : public Graph { public: void draw() { std::cout << "Circle::draw(): programs of draw a circle\n"; } }; // definitaion of fun(): as a call interface void fun(Graph *ptr) { std::cout << "pointer type: " << typeid(ptr).name() << "\n"; std::cout << "RTTI type: " << typeid(*ptr).name() << "\n"; ptr -> draw(); } // test int main() { Graph g1; Rectangle r1; Circle c1; // call by object name g1.draw(); r1.draw(); c1.draw(); std::cout << "\n"; // call by object name, and using the scope resolution operator:: r1.Graph::draw(); c1.Graph::draw(); std::cout << "\n"; // call by pointer to Base class fun(&g1); fun(&r1); fun(&c1); }
添加virtual：
#include <iostream> #include <typeinfo> // definitation of Graph class Graph { public: virtual void draw() { std::cout << "Graph::draw() : just as an interface\n"; } }; // definition of Rectangle, derived from Graph class Rectangle : public Graph { public: void draw() { std::cout << "Rectangle::draw(): programs of draw a rectangle\n"; } }; // definition of Circle, derived from Graph class Circle : public Graph { public: void draw() { std::cout << "Circle::draw(): programs of draw a circle\n"; } }; // definitaion of fun(): as a call interface void fun(Graph *ptr) { std::cout << "pointer type: " << typeid(ptr).name() << "\n"; std::cout << "RTTI type: " << typeid(*ptr).name() << "\n"; ptr -> draw(); } // test int main() { Graph g1; Rectangle r1; Circle c1; // call by object name g1.draw(); r1.draw(); c1.draw(); std::cout << "\n"; // call by object name, and using the scope resolution operator:: r1.Graph::draw(); c1.Graph::draw(); std::cout << "\n"; // call by pointer to Base class fun(&g1); fun(&r1); fun(&c1); }
归纳总结：
同名覆盖原则：
派生类与基类中有相同成员时，若未强行指名，则通过派生类对象使用的是派生类的同名成员。
二元作用域分辨符：
当派生类与基类中有相同成员时，如果要通过派生类对象访问基类中被隐藏的同名成员，可以用基类名和作用域分辨符来限定。
类型兼容原则：
在需要基类对象的任何地方,都可以使用公有派生类的对象来替代；
派生类的对象可以隐含转换为基类对象；
派生类的对象可以初始化基类的引用；
派生类的指针可以隐含转换为基类的指针；
在替代之后，派生类的对象就可以作为基类的对象使用，但只能使用从基类继承的成员。
battery.hpp
#ifndef BATTERY_HPP #define BATTERY_HPP #include<iostream> using namespace std; class Battery { public: Battery(int a=70) : capacity{a} {} int get_capacity() { return capacity; } private: int capacity; }; #endif
car.hpp
#ifndef CAR_HPP #define CAR_HPP #include<iostream> #include<string> using namespace std; class Car { public: Car(string a, string b, int c, int d=0) : maker{a}, model{b}, year{c}, odometers{d} {} void info() { cout<<"maker:\t\t"<<maker<<endl <<"moedl:\t\t"<<model<<endl <<"year:\t\t"<<year<<endl <<"odometers:\t"<<odometers<<endl; } void update_odometers(int e) { if(e<odometers) { cout<<"Wrong!Please update again!"<<endl; } else { odometers=e; } } private: string maker; string model; int year; int odometers; }; #endif
electriccar.hpp
#ifndef ELECTRICCAR_HPP #define ELECTRICCAR_HPP #include<iostream> #include"car.hpp" #include"battery.hpp" using namespace std; class ElectricCar:public Car { public: ElectricCar(string a, string b, int c, int d=0, int e=70) : Car(a, b, c, d), battery{e} {} void info() { Car::info(); cout<<"battery:\t"<<battery.get_capacity()<<"-KWh"<<endl; } private: Battery battery; }; #endif
task3.cpp
#include <iostream> #include "electricCar.hpp" int main() { using namespace std; // test class of Car Car oldcar("Audo", "a1", 2021); cout << "--------oldcar's info--------" << endl; oldcar.update_odometers(35000); oldcar.info(); cout << endl; // test class of ElectricCar ElectricCar newcar("Tesll", "model s", 2021); newcar.update_odometers(3500); cout << "\n--------newcar's info--------\n"; newcar.info(); }
pets.hpp
#ifndef PETS_HPP #define PETS_HPP #include<iostream> #include<string> using namespace std; class MachinePets { public: MachinePets(const string s) : nickname{s} {} string get_nickname() const { return nickname; } virtual string talk() {} private: string nickname; }; class PetCats : public MachinePets { public: PetCats(const string s) : MachinePets {s} {} string talk() { return "miao wu~"; } }; class PetDogs : public MachinePets { public: PetDogs(const string s) : MachinePets {s} {} string talk() { return "wang wang~"; } }; #endif
task4.cpp
#include <iostream> #include "pets.hpp" void play(MachinePets *ptr) { std::cout << ptr->get_nickname() << " says " << ptr->talk() << std::endl; } int main() { PetCats cat("miku"); PetDogs dog("da huang"); play(&cat); play(&dog); }
