发布时间 : 星期二 文章C语言程序设计（郑莉）课后习题答案更新完毕开始阅读826a4a9476c66137ef061931
float itsLength; };
class Square : public Rectangle { public:
Square(float len); ~Square(){} };
Square::Square(float len): Rectangle(len，len) { }
void main() {
Shape * sp;
sp = new Circle(5);
cout << \<< endl; delete sp;
sp = new Rectangle(4，6);
cout << \<< endl; delete sp;
sp = new Square(5);
cout << \endl; delete sp; }
程序运行输出：
The area of the Circle is 78.5 The area of the Rectangle is 24 The area of the Square is 25
7-6 定义一个哺乳动物Mammal类，再由此派生出狗Dog类，定义一个Dog类的对象，观察基类与派生类的构造函数与析构函数的调用顺序。 解： 源程序：
#include
enum myColor{ BLACK， WHITE };
class Mammal { public:
// constructors Mammal(); ~Mammal();
//accessors
int GetAge() const { return itsAge; } void SetAge(int age) { itsAge = age; } int GetWeight() const { return itsWeight; } void SetWeight(int weight) { itsWeight = weight; }
//Other methods
void Speak() const { cout << \
protected: int itsAge; int itsWeight; };
class Dog : public Mammal { public: Dog(); ~Dog();
myColor GetColor() const { return itsColor; } void SetColor (myColor color) { itsColor = color; }
void WagTail() { cout << \
private:
myColor itsColor; };
Mammal::Mammal(): itsAge(1)， itsWeight(5) {
cout << \}
Mammal::~Mammal() {
cout << \}
33
Dog::Dog(): itsColor (WHITE) {
cout << \}
Dog::~Dog() {
cout << \}
int main() {
Dog Jack; Jack.Speak(); Jack.WagTail();
cout << \
return 0; }
程序运行输出： Mammal constructor... Dog constructor... Mammal sound! Tail wagging... Fido is 1 years old Dog destructor... Mammal destructor...
7-7 定义一个基类，构造其派生类，在构造函数中输出提示信息，观察构造函数的执行情况。 解：
#include
class BaseClass { public: BaseClass(); };
BaseClass::BaseClass() {
cout << \构造基类对象!\ }
class DerivedClass : public BaseClass { public:
DerivedClass(); };
DerivedClass::DerivedClass() {
cout << \构造派生类对象!\}
void main() {
DerivedClass d; }
程序运行输出： 构造基类对象! 构造派生类对象!
7-8 定义一个Document类，有name成员变量，从Document派生出Book类，增加PageCount变量。 解：
#include
class Document { public: Document(){};
Document( char *name ); char *Name; // Document name. void PrintNameOf(); // Print name. };
Document::Document( char *name ) {
Name = new char[ strlen( name ) + 1 ]; strcpy( Name, name ); };
void Document::PrintNameOf() {
cout << Name << endl;
34
}
class Book : public Document { public:
Book( char *name, long pagecount ); void PrintNameOf(); private: long PageCount; };
Book::Book( char *name, long pagecount ):Document(name) {
PageCount = pagecount; }
void Book::PrintNameOf() {
cout << \Document::PrintNameOf(); }
void main() {
Document a(\Book b(\b.PrintNameOf(); }
程序运行输出： Name of book: Book1
7-9 定义基类Base，有两个共有成员函数fn1()、fn2()，私有派生出Derived类，如果想在Derived类的对象中使用基类函数fn1()，应怎么办？ 解： class Base { public:
int fn1() const { return 1; } int fn2() const { return 2; } };
class Derived : private Base { public:
int fn1() { return Base::fn1();}; int fn2() { return Base::fn2();}; };
void main() {
Derived a; a.fn1(); }
7-10 定义object类，有weight属性及相应的操作函数，由此派生出box类，增加Height和width属性及相应的操作函数，声明一个box对象，观察构造函数与析构函数的调用顺序。 解：
#include
class object { private: int Weight; public: object() {
cout << \构造object对象\Weight = 0; }
int GetWeight(){ return Weight;} void SetWeight(int n){ Weight = n;}
~object() { cout << \析构object对象\};
class box : public object { private:
int Height,Width; public: box() {
cout << \构造box对象\Height = Width = 0; }
int GetHeight(){ return Height;} void SetHeight(int n){ Height = n;} int GetWidth(){ return Width;} void SetWidth(int n){ Width = n;}
35
~box() { cout << \析构box对象\};
void main() { box a; }
程序运行输出： 构造object对象 构造box对象 析构box对象 析构object对象
7-11 定义一个基类BaseClass，从它派生出类DerivedClass，BaseClass有成员函数fn1()、fn2()，DerivedClass也有成员函数fn1()、fn2()，在主程序中定义一个DerivedClass的对象，分别用DerivedClass的对象以及BaseClass和DerivedClass的指针来调用fn1()、fn2()，观察运行结果。 解：
#include
class BaseClass { public: void fn1(); void fn2(); };
void BaseClass::fn1() {
cout << \调用基类的函数fn1()\}
void BaseClass::fn2() {
cout << \调用基类的函数fn2()\}
class DerivedClass : public BaseClass { public: void fn1(); void fn2(); };
void DerivedClass::fn1() {
cout << \调用派生类的函数fn1()\}
void DerivedClass::fn2() {
cout << \调用派生类的函数fn2()\}
void main() {
DerivedClass aDerivedClass;
DerivedClass *pDerivedClass = &aDerivedClass; BaseClass *pBaseClass = &aDerivedClass;
aDerivedClass.fn1(); aDerivedClass.fn2(); pBaseClass->fn1(); pBaseClass->fn2(); pDerivedClass->fn1(); pDerivedClass->fn2(); }
程序运行输出： 调用派生类的函数fn1() 调用派生类的函数fn2() 调用基类的函数fn1() 调用基类的函数fn2() 调用派生类的函数fn1() 调用派生类的函数fn2()
7-12 为例9-1的吹泡泡程序加一版权（About）对话框。然后修改例9-1的程序，加入以下内容： 程 序：
1．在程序首部加上文件包含命令 #include “resource.h”
2．在框架窗口类之前加入从CDialog类派生的对话框类：// 对话框类
class CAboutDlg: public CDialog { public: CAboutDlg();
enum {IDD = IDD_DIALOG1}; }; inline
36