| 1. Purpose of the experiment: 1. Understand the characteristics and ideas of object-oriented programming, understand the encapsulation and information hiding of classes. 2. Master the definition and function of classes and objects, and use them proficiently. 3. Master the definition of member functions of classes, and be proficient in defining and applying member functions of classes. 4. Master the references of object members, and skillfully apply the references of object members. 5. To master the constructor and destructor, skillful application is required. |
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| 2. Experimental content
code: #include <iostream.h> #include <string.h> class MyClal { char *str; public: MyClal(char *s); MyClal() { cout<<"Destructor:Destroying=>"<<str<<"\n"; delete str; } void print(){cout<<"------printed by=>"<<str<<endl;}}; MyClal::MyClal(char *s) { cout<<"Constructor:Initializing=>"<<s<<"\n"; str=new char[strlen(s)+1]; strcpy(str,s);} MyClal IO("Global IO"); void main() { IO.print(); MyClal I1("function_Local I1"); int cond=2; I1.print(); while(cond) { cout<<"In block.\n"; MyClal I2("Block_Local I2"); I2.print(); static MyClal I3("Static I3"); cond--; } cout<<"Exited block.\n";} 程序测试及运行结果：
程序代码： #include<iostream.h> char name[10]; //分别定义个char型的 name 和prof数组用储存姓名和职务 } strcpy(name,n); return leader;//返回领导者姓名 } printf("%10s %10s%",name,prof); }}; Person p[]={Person("王华","室主任"),Person("李明","职工"), }; p[i].disp(); //循环 输出姓名和职务 //循环输出领导姓名 }} 程序测试及运行结果：
程序代码： #include<iostream> using namespace std; template <class T>class myTmplt { T x,y,z; public: myTmplt(T x0,T y0,T z0){x=x0;y=y0;z=z0;} //构造函数 T max() //求三个数据中份成员的最大者 { int d; if(x>y) d=(x>y)?x:y; else d=(y>z)?y:z;//排序语句 return d; }; bool order() //三个数据成员从小到大是否有序 { return(x<y && x<y && x<y)? true:false; }; void print() //屏幕显示 输出 { cout<<x<<" "<<y<<" "<<z<<endl;}; }; int main() { myTmplt<int>s1(1,2,5); s1.print(); cout<<"s1.max="<<s1.max()<<endl; if(s1.order()) cout<<"s1.order()=>OK!"<<endl; myTmplt<char>s2('A','t','f'); s2.print(); cout<<"s2.max="<<s2.max()<<endl; if(s2.order()) cout<<"s2.order()=>OK!"<<endl; } 程序测试及运行结果：
程序代码： #include<iostream>//头文件 #include<cstring> #include<iomanip> using namespace std;//命名空间 class student//定义student类 { char name[10];//定义存储姓名的数组 int deg; char level[7];//储存成绩的数组 public: student(char na[],int d) { strcpy(name,na);//字符串复制 deg=d;//私有数据 } char *getname(){ return name;} friend void trans(student &s)//定义友元函数 {//等级判断 if(s.deg>=90) strcpy(s.level,"优"); else if(s.deg>=80) strcpy(s.level,"良"); else if(s.deg>=70) strcpy(s.level,"中"); else if(s.deg>=60) strcpy(s.level,"及格"); else strcpy(s.level,"不及格"); } int disp( ) { cout<<setw(10)<<name<<setw(6)<<deg<<setw(8)<<level<<endl; }}; int main( ) { student st[]={student("王华",78),student("李明",92),student("张伟",62),student("孙强",88)}; cout<<"输出结果:"<<endl; cout<<setw(10)<<"姓名"<<setw(6)<<"成绩"<<setw(8)<<"等级"<<endl; for (int i=1;i<4;i++)//循环输出 { trans(st[i]); st[i].disp(); } return 0;} 程序测试及运行结果：
程序代码： #include<iostream>//头文件 using namespace std;//命名空间 class Complex//定义复数complex类 {public://数据成员为公有 Complex(){real=0;imag=0;} Complex(double r,double i){real=r;imag=i;} Complex operator+(Complex &c2);//定义四则运算的重载运算符 Complex operator-(Complex &c2); Complex operator*(Complex &c2); Complex operator/(Complex &c2); void display(); private://数据成员为私有 double real;//实部 double imag;//虚部 }; Complex Complex::operator +(Complex &c2)//重载运算符为"+" {Complex c; c.real=real+c2.real; c.imag=imag+c2.imag; return c; } Complex Complex::operator -(Complex &c2)//重载运算符为"-" {Complex c; c.real=real-c2.real; c.imag=imag-c2.imag; return c; } Complex Complex::operator *(Complex &c2)//重载运算符为"*" {Complex c; c.real=real*c2.real; c.imag=imag*c2.imag; return c; } Complex Complex::operator /(Complex &c2)//重载运算符为"/" {Complex c; c.real=(real*c2.real+imag*c2.imag)/(c2.real*c2.real+c2.imag*c2.imag); c.imag=(imag*c2.real-real*c2.imag)/(c2.real*c2.real+c2.imag*c2.imag); return c; } void Complex::display() {cout<<"("<<real<<","<<imag<<"i)"<<endl; } int main()//主函数 {Complex c1(3,4),c2(5,-10),c3; c3=c1+c2; cout<<"c1+c2="; c3.display(); c3=c1-c2; cout<<"c1-c2="; c3.display(); c3=c1*c2; cout<<"c1*c2="; c3.display(); c3=c1/c2; cout<<"c1/c2="; c3.display(); return 0;} 程序测试及运行结果：
程序代码： #include<iostream> #include<cstring> using namespace std; class String {public: String()//定义默认构造函数 { p=NULL;} String(const char *str);//声明构造函数 void display();//声明输出p所指向的字符串函数 friend bool operator>(String &string1,String &string2);//声明运算符重载函数为友元函数 friend bool operator<(String &string1,String &string2);//声明运算符重载函数为友元函数 friend bool operator==(String &string1,String &string2);//声明运算符重载函数为友元函数 private: const char *p;//字符型指针，用于指向字符串 }; String::String(const char *str)//定义构造函数 {p=str;//使p指向形参字符串 } void String::display()//定义输出p所指向的字符串函数 { cout<<p;} bool operator>(String &string1,String &string2)//对运算符">"重载 {if(strcmp(string1.p,string2.p)>0) return true; else return false;} bool operator<(String &string1,String &string2)//对运算符"<"重载 {if(strcmp(string1.p,string2.p)<0) return true; else return false;} bool operator==(String &string1,String &string2)//对运算符"=="重载 {if(strcmp(string1.p,string2.p)==0) return true; else return false;} void compare(String &string1,String &string2) {if(operator>(string1,string2)==1) {string1.display(); cout<<">"; string2.display(); cout<<endl;} else if(operator<(string1,string2)==1) {string1.display(); cout<<"<"; string2.display(); cout<<endl;} else if(operator==(string1,string2)==1) {string1.display(); cout<<"=="; string2.display(); cout<<endl;}} int main() {String string1("Hello"),string2("Book"),string3("Computer"),string4("Hello");//定义对象 compare(string1,string2); compare(string2,string3); compare(string1,string4); return 0; } 程序测试及运行结果：
程序代码： #include<iostream>//头文件 using namespace std;//命名空间 class Matrix {friend ostream& operator<<(ostream& out, Matrix& M); //重载<<运算符 friend istream& operator>>(istream& in,Matrix& M); //重载>>运算符 public: Matrix(int r,int c); Matrix operator+(Matrix &M) ; Matrix operator-(Matrix &M); Matrix operator*(Matrix &M); int GetCounts() {return rows*cols;} private: int rows, cols; //定义矩阵的行数rows，列数cols double *m; //矩阵中实际(物理)按行存放的元素}; Matrix::Matrix(int r,int c) {rows=r,cols=c; m=new double[rows*cols];} istream& operator>>(istream& in,Matrix& M) //输入流重载 {int i; for(i=0;i<M.rows*M.cols;i++) {in>>*(M.m+i);} return in;} ostream& operator<<(ostream& out,Matrix& M) //输出流重载 {int i,j=0; for(i=0; i<M.rows*M.cols; i++) {if(j==M.cols) j=0,out<<endl; out<<" "<<*(M.m+i); j++; }return out; }Matrix Matrix::operator+(Matrix &M) {int i; Matrix tempM(rows,cols); for(i=0;i<rows*cols;i++) *(tempM.m+i)=*(m+i)+*(M.m+i); return tempM;} Matrix Matrix::operator-(Matrix &M) {int i; Matrix tempM(rows,cols); for(i=0;i<rows*cols;i++) *(tempM.m+i)=*(m+i)-*(M.m+i); return tempM; }Matrix Matrix::operator*(Matrix &M) {int i,j,t,k=0; Matrix tempM(rows,cols); for(i=0; i<rows*cols; i+=cols) for(j=0;j<cols;j++) for(t=0,*(tempM.m+k)=0;t<cols;t++) *(tempM.m+k)=*(tempM. m+k)+*(m+i+t)**(M.m+j+t*rows); }int main() {Matrix A(3,3); Matrix B(3,3); Matrix C(3,3); cout<< "输入第一个矩阵的"<<A.GetCounts()<<"个数:"<<endl;cin>>A; cout<<"输入第二个矩阵的"<<B.GetCounts()<<"个数:"<<endl;cin>>B; C=A+B; cout<<endl<<"矩阵之和:"<<endl; cout<<C<<endl; cout<<endl<<"矩阵之差:"<<endl; C=A-B; cout<<C<<endl; C=A*B; cout<<endl<<"矩阵之积:"<<endl; cout<<C<<endl<<endl;} 程序测试及运行结果：
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| 分析与讨论：
答：赋值是必须先定义一个对象,然后用一个已有值的对象去给这个对象赋值,而对象的复制是从无到有的建立一个对象并赋值。
答：复制构造函数中，可以对数据成员进行其他处理，表示我引用了构造函数，在复制构造函数中，进一步操作，此时构造函数不变。
答：友元的关系是不能传递的，所以类A不是类C的友元。 4、使用静态数据成员有什么特点和优势？ 答：静态成员的特点：不管类创建多少个对象，其静态成员在内存中只保留一份副本，这个副本为该类的所有对象所共享。
答：利用友元函数重载流操作符或者定义在类外部，使用类的成员函数暴露对类成员的访问。 6、哪些运算符是不允许重载的？ 答：1、.(成员访问运算符)2、.*(成员指针访问运算符)3、::(域运算符)4、sizeof(长度运算符)5、?:(条件运算符） 7、为什么算术运算符“+”“－”“*”“/”应该重载为友元函数? 答：重载为成员函数不能满足使用要求，重载为普通函数又不能访问类的私有成员，所以需要将运算符重载为友元。 |
The design and experiment of basic operations and operator overloading such as C language/C++ (3/5)
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