《C++ primerplus》第13章练习题
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1.对CD类的派生练习。基类CD类存储作者和作品号等信息，派生类Classic额外增加一格“主要作品”的信息。主函数使用拷贝构造函数、按引用传递参数的函数和指针来测试基类和派生类的功能。
注意继承类和基类的权限关系、初始化成员列表的使用。
class.h
#ifndef _CLASS_H_
#define _CLASS_H_
#include <iostream>
using std::cin;
using std::cout;
class CD
{
private:
char performers[20] = {}; //初始化为空，不然输出一堆烫char label[20] = {};
int selections;
double playtime;
public:
CD(constchar *s1, constchar*s2, int n, double x); //自定义构造函数
CD(const CD & d); //拷贝构造函数
CD(); //默认构造函数virtual ~CD();
virtualvoid Report()const;
virtual CD & operator = (const CD & d);
};
class Classic :public CD
{
private:
char collection[50] = {};
public:
Classic(constchar *c, constchar *s1, constchar*s2, int n, double x);
Classic();
~Classic();
void Report()const;
Classic & operator = (const Classic & d);
};
#endif
DefineClass.cpp
#include "class.h" CD::CD(constchar *s1, constchar*s2, int n, double x) { for (int i = 0; s1[i] != ‘\0‘; i++) { performers[i] = s1[i]; } for (int i = 0; s2[i] != ‘\0‘; i++) { label[i] = s2[i]; } selections = n; playtime = x; } CD::CD(const CD & d) { for (int i = 0; d.performers[i] != ‘\0‘; i++) { performers[i] = d.performers[i]; } for (int i = 0; d.label[i] != ‘\0‘; i++) { label[i] = d.label[i]; } selections = d.selections; playtime = d.playtime; } CD::CD() { } CD::~CD() { } void CD::Report()const { cout << "Performers: "; for (int i = 0; performers[i] != ‘\0‘; i++) { cout << performers[i]; } cout << "\n"; cout << "Label: "; for (int i = 0; label[i] != ‘\0‘; i++) { cout << label[i]; } cout << "\n"; cout << "Selections: " << selections << "\n"; cout << "Playtime: " << playtime << "\n"; } CD & CD::operator=(const CD & d) { for (int i = 0; d.performers[i] != ‘\0‘; i++) { performers[i] = d.performers[i]; } for (int i = 0; d.label[i] != ‘\0‘; i++) { label[i] = d.label[i]; } selections = d.selections; playtime = d.playtime; return *this; } //derived class Classic::Classic(constchar *c, constchar *s1, constchar*s2, int n, double x):CD(s1,s2,n,x) { for (int i = 0; c[i] != ‘\0‘; i++) { collection[i] = c[i]; } } Classic::Classic() { } Classic::~Classic() { } void Classic::Report()const { CD::Report(); cout << "Collection: "; for (int i = 0; collection[i] != ‘\0‘; i++) { cout << collection[i]; } cout << "\n\n"; } Classic & Classic::operator = (const Classic & d) { CD::operator=(d); for (int i = 0; d.collection[i] != ‘\0‘; i++) { collection[i] = d.collection[i]; } return *this; }
main.cpp
#include "class.h"void Bravo(const CD & disk); int main() { CD c1("Beatles", "Capitol", 14, 35.5); Classic c2 = Classic("Piano Sonata in B flat, Fantasia in C", "Alfred Brendel", "Philips", 2, 57.17); CD *pcd = &c1; cout << "Using Object directly:\n"; c1.Report(); c2.Report(); cout << "Using type cd * pointer to objects:\n"; pcd->Report(); pcd = &c2; pcd->Report(); cout << "Calling a function with a cd reference argument:\n"; Bravo(c1); Bravo(c2); cout << "Testing assignment:\n"; Classic copy; copy = c2; copy.Report(); //pause cin.get(); return0; } void Bravo(const CD & disk) { disk.Report(); }
2.以上题为基础。存储的字符数组用使用动态分配内存。
我初始化对象的时候把两个字符成员都设为了空指针，做题的过程中，了解到了空指针不能被赋值。其它需要注意的地方见注释。
ClassCD.h
#ifndef _CLASSCD_
#define _CLASSCD_
#include <iostream>
using std::cout;
using std::cin;
//Base Class Declareclass CD
{
private:
char *performers = nullptr;
char *label = nullptr;
int selections;
double playtime;
public:
CD(constchar *s1, constchar*s2, int n, double x); //自定义构造函数
CD(const CD & d); //拷贝构造函数
CD(); //默认构造函数virtual ~CD();
virtualvoid Report()const;
virtual CD & operator = (const CD & d);
};
//Base Class Define
CD::CD(constchar *s1, constchar*s2, int n, double x)
{
//根据s1和s2的长度分配内存
//strlen()计算的长度不包含终止符‘\0‘
//为了不影响report()的执行，分配的内存长度+1，使其包含‘\0‘
performers = newchar[strlen(s1)+1];
for (int i = 0; i < (strlen(s1)+1); i++)
{
performers[i] = s1[i];
}
label = newchar[strlen(s2)+1];
for (int i = 0; i < (strlen(s2)+1); i++)
{
label[i] = s2[i];
}
selections = n;
playtime = x;
}
CD::CD()
{
selections = 0;
playtime = 0;
}
CD::CD(const CD & d)
{
int count;
//对象分配内存的成员不是空指针才会赋值，防止内存访问混乱if (d.performers != nullptr)
{
//获取等号右边的类里面分配的长度for (count = 0; d.performers[count] != ‘\0‘; count++)
{
;
}
//根据它的长度来分配自身的长度，加上‘\0‘一位
performers = newchar[count + 1];
//给自身成员变量赋值，取到终止符后停止for (int i = 0; d.performers[i] != ‘\0‘; i++)
{
performers[i] = d.performers[i];
if (d.performers[i + 1] == ‘\0‘)
{
performers[i + 1] = ‘\0‘;
break;
}
}
}
//以下同理if (d.label != nullptr)
{
for (count = 0; d.label[count] != ‘\0‘; count++)
{
;
}
label = newchar[count + 1];
for (int i = 0; d.label[i] != ‘\0‘; i++)
{
label[i] = d.label[i];
if (d.label[i + 1] == ‘\0‘)
{
label[i + 1] = ‘\0‘;
break;
}
}
}
selections = d.selections;
playtime = d.playtime;
}
CD::~CD()
{
//是空指针，说明从未分配过内存，不需要释放
//不是空指针，说明分配了内存，需要释放if (performers != nullptr)
{
delete[] performers;
}
if (label != nullptr)
{
delete[] label;
}
}
void CD::Report()const
{
//对象分配内存的成员不是空指针才会打印，防止内存访问混乱
cout << "Performers: ";
if (performers != nullptr)
{
for (int i = 0; performers[i] != ‘\0‘; i++)
{
cout << performers[i];
}
}
cout << "\n";
cout << "Label: ";
if (label != nullptr)
{
for (int i = 0; label[i] != ‘\0‘; i++)
{
cout << label[i];
}
}
cout << "\n";
cout << "Selections: " << selections << "\n";
cout << "Playtime: " << playtime << "\n";
}
CD & CD::operator=(const CD & d)
{
int count;
//对象分配内存的成员不是空指针才会赋值，防止内存访问混乱if (d.performers != nullptr)
{
//获取等号右边的类里面分配的长度for (count = 0; d.performers[count] != ‘\0‘; count++)
{
;
}
//根据它的长度来分配自身的长度，加上‘\0‘一位
performers = newchar[count + 1];
//给自身成员变量赋值，取到终止符后停止for (int i = 0; d.performers[i] != ‘\0‘; i++)
{
performers[i] = d.performers[i];
if (d.performers[i + 1] == ‘\0‘)
{
performers[i + 1] = ‘\0‘;
break;
}
}
}
//以下同理if (d.label != nullptr)
{
for (count = 0; d.label[count] != ‘\0‘; count++)
{
;
}
label = newchar[count + 1];
for (int i = 0; d.label[i] != ‘\0‘; i++)
{
label[i] = d.label[i];
if (d.label[i + 1] == ‘\0‘)
{
label[i + 1] = ‘\0‘;
break;
}
}
}
selections = d.selections;
playtime = d.playtime;
return *this;
}
//Derived Class Declareclass Classic :public CD
{
private:
char *collection = nullptr;
public:
Classic(constchar *c, constchar *s1, constchar*s2, int n, double x);
Classic();
~Classic();
void Report()const;
Classic & operator = (const Classic & d);
};
//Derived Class Define
Classic::Classic(constchar *c, constchar *s1, constchar*s2, int n, double x) :CD(s1, s2, n, x)
{
collection = newchar[strlen(c) + 1];
for (int i = 0; i < (strlen(c) + 1); i++)
{
collection[i] = c[i];
}
}
Classic::Classic()
{
}
Classic::~Classic()
{
if (collection != nullptr)
{
delete[] collection;
}
}
void Classic::Report()const
{
CD::Report();
cout << "Collection: ";
if (collection != nullptr)
{
for (int i = 0; collection[i] != ‘\0‘; i++)
{
cout << collection[i];
}
}
cout << "\n\n";
}
Classic & Classic::operator = (const Classic & d)
{
CD::operator=(d);
int count;
if (d.collection != nullptr)
{
for (count = 0; d.collection[count] != ‘\0‘; count++)
{
;
}
collection = newchar[count + 1];
for (int i = 0; d.collection[i] != ‘\0‘; i++)
{
collection[i] = d.collection[i];
if (d.collection[i + 1] == ‘\0‘)
{
collection[i + 1] = ‘\0‘;
break;
}
}
}
return *this;
}
#endif
main.cpp
#include "ClassCD.h"void Bravo(const CD & disk); int main() { CD c1("Beatles", "Capitol", 14, 35.5); Classic c2 = Classic("Piano Sonata in B flat, Fantasia in C", "Alfred Brendel", "Philips", 2, 57.17); CD *pcd = &c1; cout << "Using Object directly:\n"; c1.Report(); c2.Report(); cout << "Using type cd * pointer to objects:\n"; pcd->Report(); pcd = &c2; pcd->Report(); cout << "Calling a function with a cd reference argument:\n"; Bravo(c1); Bravo(c2); cout << "Testing assignment:\n"; Classic copy; copy = c2; copy.Report(); //pause cin.get(); return0; } void Bravo(const CD & disk) { disk.Report(); }
3.不想使用原题所以没用，目的是练习抽象基类的继承。
所谓抽象基类，就是把定义的基类之中的虚成员函数声明为纯虚的（virtual修饰的函数后面加个 = 0），那么这个基类就只能用于继承，而不能实例化。一旦在代码里试图去实例化，编译之前就会提示“不允许使用抽象类型XXX的对象”。
抽象基类是抽象出一系列对象的共性的做法，方便派生出许多相似的对象。 需要注意，基类定义的纯虚函数不给出定义，而由所有派生类给出自己的定义。
下面是自己简单的练习。定义一个MovingObject的抽象基类，nowwhere()显示当前目标的位置，set_speed()设定目标的速度。从MovingObject派生出Car和Plane对象，各自的构造函数、析构函数、nowwhere()和set_speed()方法都不同。Car类会在坐标轴上按上下左右四个方向移动，Plane类指定一个目标地点，用动态数组的方式存储和打印该地点。
class.h
#ifndef _CLASS_H_
#define _CLASS_H_
#include <iostream>
#include <string>
using std::cout;
using std::cin;
using std::string;
/* Abstract Base Class */class MovingObject
{
protected:
double x;
double y;
double v;
string name;
public:
MovingObject();
virtual ~MovingObject();
virtualvoid nowwhere() = 0; //pure virtual functionvirtualvoid set_speed(unsigned int vv) = 0; //pure virtual function};
MovingObject::MovingObject()
{
}
MovingObject::~MovingObject()
{
}
/* Derived Class A */class Car :public MovingObject
{
public:
enum car_direction
{
UP = 0,
DOWN,
LEFT,
RIGHT,
RESET
}drive_to;
private:
public:
Car();
Car(constdouble xx, constdouble yy);
~Car();
void move(car_direction drive_to,double t);
void nowwhere();
void set_speed(unsigned int vv);
};
Car::Car()
{
name = "car";
x = 0;
y = 0;
v = 30;
cout << "A new car constructed.\n";
}
Car::Car(constdouble xx, constdouble yy)
{
name = "car";
x = xx;
y = yy;
v = 30;
cout << "A new car constructed.\n";
}
Car::~Car()
{
cout << "Car decontructed\n";
}
void Car::move(car_direction drive_to = RESET,double t = 0)
{
switch (drive_to)
{
case(UP):
{
cout << "The car‘s moving up, " << "with " << v << " m/s in " << t << " s.\n";
y = y + v * t;
break;
}
case(DOWN):
{
cout << "The car‘s moving down, " << "with " << v << " m/s in " << t << " s.\n";
y = y - v * t;
break;
}
case(LEFT):
{
cout << "The car‘s moving left, " << "with " << v << " m/s in " << t << " s.\n";
x = x - v * t;
break;
}
case(RIGHT):
{
cout << "The car‘s moving right, " << "with " << v << " m/s in " << t << " s.\n";
x = x + v * t;
break;
}
case(RESET):
{
cout << "The car‘s at (0,0).\n";
x = 0;
y = 0;
v = 1;
break;
}
default:
{
break;
}
}
}
void Car::nowwhere()
{
cout << name << " is at (" << x << "," << y << ").\n";
}
void Car::set_speed(unsigned int vv)
{
v = vv;
}
/* Derived Class B */class Plane:public MovingObject
{
private:
char *flywhere;
public:
Plane();
~Plane();
void nowwhere();
void set_speed(unsigned int vv);
};
Plane::Plane()
{
flywhere = newchar[20];
char wishplace[20] = {};
v = 180;
cout << "A plane just arrived.\n";
cout << "Assign one destination you wish: ";
cin >> wishplace;
for (int i = 0; i < (strlen(wishplace)+1); i++)
{
flywhere[i] = wishplace[i];
}
}
Plane::~Plane()
{
cout << "Plane deconstructed.\n";
delete[] flywhere;
}
void Plane::nowwhere()
{
cout << "The plane‘s flying at " << v << " m/s.\n";
cout << "Finally it arrived at ";
for (int i = 0; flywhere[i] != ‘\0‘; i++)
{
cout << flywhere[i];
}
cout << ".\n";
}
void Plane::set_speed(unsigned int vv)
{
cout << "Changing speed to (150~250): ";
if ((vv >= 150) && (vv <= 250))
{
v = vv;
}
else
{
cout << "Invalid speed! (Current: " << v << " m/s.)";
}
}
#endif
main.cpp
#include "Class.h"int main() { Car car1; car1.move(Car::UP,10); car1.nowwhere(); Plane plane1; plane1.set_speed(180); plane1.nowwhere(); //pause cin.get(); cin.get(); return0; }
输出结果：
4.派生练习。定义存储酒相关信息的类和派生类。
对原题问题的回答：
（a）见代码。
（b）Port有所有默认参数的构造函数和默认构造函数冲突了。
（c）运算符=重载的函数应用的对象算不同的类型，运算符<<重载的函数是友元函数，友元函数不归属于类，也不能被继承，所以不需要声明为虚。
（d）见代码。
Class.h
#ifndef _CLASS_H_
#define _CLASS_H_
#include <iostream>
using std::ostream;
using std::cout;
using std::cin;
//Base Classclass Port
{
private:
char * brand;
char style[20]; //tawny,ruby,vintage...int bottles;
public:
Port(constchar *br, constchar *st, int b); //重新定义，去掉默认参数，防止与默认构造函数重复
Port(); //创建的默认构造函数
Port(const Port & p);
virtual ~Port() { delete[]brand; }
Port & operator = (const Port & p);
Port & operator += (int b); //add bottles
Port & operator -= (int b);
int BottleCount()const { return bottles; }
virtualvoid show()const;
friend ostream & operator << (ostream & os, const Port & p);
};
Port::Port(constchar *br, constchar *st, int b = 0)
{
brand = newchar[strlen(br) + 1];
for (int i = 0; i < (strlen(br) + 1); i++)
{
brand[i] = br[i];
}
for (int i = 0; i < (strlen(st) + 1); i++)
{
style[i] = st[i];
}
bottles = b;
}
Port::Port()
{
brand = newchar[20];
brand[0] = ‘\0‘;
style[0] = ‘\0‘;
bottles = 0;
}
Port::Port(const Port & p)
{
for (int i = 0; i<strlen(p.brand)+1; i++)
{
brand[i] = p.brand[i];
}
for (int i = 0; p.style[i]!=‘\0‘; i++)
{
style[i] = p.style[i];
}
bottles = p.bottles;
}
Port & Port::operator = (const Port & p)
{
for (int i = 0; i<strlen(p.brand)+1; i++)
{
brand[i] = p.brand[i];
}
for (int i = 0; i < strlen(p.style) + 1; i++)
{
style[i] = p.style[i];
}
bottles = p.bottles;
return *this;
}
Port & Port::operator += (int b)
{
bottles += b;
return *this;
}
Port & Port::operator -= (int b)
{
bottles -= b;
return *this;
}
void Port::show()const
{
cout << "Brand:";
for (int i = 0; brand[i] != ‘\0‘; i++)
{
cout << brand[i];
}
cout << "\n";
cout << "Kind:";
for (int i = 0; style[i] != ‘\0‘; i++)
{
cout << style[i];
}
cout << "\n";
cout << "Bottles:" << bottles << "\n";
}
ostream & operator << (ostream & os, const Port & p)
{
os << "Brand:";
for (int i = 0; p.brand[i] != ‘\0‘; i++)
{
cout << p.brand[i];
}
os << "\n";
os << "Kind:";
for (int i = 0; p.style[i] != ‘\0‘; i++)
{
os << p.style[i];
}
os << "\n";
os << "Bottles:" << p.bottles << "\n";
return os;
}
//Derived Classclass VintagePort :public Port
{
private:
char *nickname;
int year;
public:
VintagePort();
VintagePort(constchar * br, int b, constchar *nn, int y);
VintagePort(VintagePort & vp);
~VintagePort() { delete[]nickname; }
VintagePort & operator = (const VintagePort & vp);
void show() const;
friend ostream & operator << (ostream & os, const VintagePort & vp);
};
VintagePort::VintagePort()
{
nickname = newchar[20];
nickname[0] = ‘\0‘;
year = 0;
}
VintagePort::VintagePort(constchar * br, int b, constchar *nn, int y):Port(br,"none",b)
{
nickname = newchar[strlen(nn) + 1];
for (int i = 0; i < strlen(nn) + 1; i++)
{
nickname[i] = nn[i];
}
year = y;
}
VintagePort::VintagePort(VintagePort & vp)
{
for (int i = 0; i < strlen(vp.nickname) + 1; i++)
{
nickname[i] = vp.nickname[i];
}
year = vp.year;
}
void VintagePort::show()const
{
Port::show();
cout << "Nickname:";
for (int i = 0; nickname[i] != ‘\0‘; i++)
{
cout << nickname[i];
}
cout << "\n";
cout << "Year:" << year;
cout << "\n";
}
VintagePort & VintagePort::operator = (const VintagePort & vp)
{
Port::operator=(vp);
for (int i = 0; i < strlen(vp.nickname) + 1; i++)
{
nickname[i] = vp.nickname[i];
}
year = vp.year;
return *this;
}
ostream & operator << (ostream & os, const VintagePort & vp)
{
cout << "Nickname:";
for (int i = 0; vp.nickname[i] != ‘\0‘; i++)
{
os << vp.nickname[i];
}
os << "\n";
os << "Year:" << vp.year;
os << "\n";
return os;
}
#endif
main.cpp
#include "Class.h"int main() { cout << "-- p1 using default constructor -- \n"; Port p1; p1.show(); cout << "-- p2 using custom constructor -- \n"; Port p2("Gallo", "vintage", 20); p2.show(); cout << "-- p2 add 20 bottles -- \n"; p2 += 20; p2.show(); cout << "-- copy p2 -> p1 -- \n"; p1 = p2; p1.show(); cout << "-- cout << p1 -- \n"; cout << p1; cout << "-- vp1 using default constructor -- \n"; VintagePort vp1; vp1.show(); cout << "-- vp2 using custom constructor -- \n"; VintagePort vp2("Ruby", 10, "pussy", 1998); vp2.show(); cout << "-- copy vp2 -> vp1 -- \n"; p1 = p2; vp1 = vp2; vp1.show(); cout << "-- copy p2 -> p1 -- \n"; p1 = p2; cout << vp2; cout << "-- cout << vp1 -- \n"; cout << vp1; //pause cin.get(); return0; }
原文：https://www.cnblogs.com/banmei-brandy/p/12005387.html
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