c++之运算符重载二

重载++和--

设  A  Aobject ；

运算符 ++和 - - 有两种方式：

前置方式：   ++Aobject  --Aobject

一元  成员函数  重载  A :: A operator++ () ;  

  解释为：  Aobject . operator ++( ) ;

          友元函数  重载  friend A operator++ (A &) ;

  解释为：   operator ++( Aobject ) ;  

后置方式：  Aobject ++  Aobject

二元  成员函数  重载  A :: A  operator++ (int) ;

  解释为：   Aobject . operator ++( 0 ) ;

          友元函数  重载：  friend A operator++ (A &, int) ;  

  解释为：   operator++(Aobject, 0) 

#include <iostream>
using namespace std;

//使用成员函数重载++运算符
class Increase
{
public:
    Increase()
    {
        value =0;
    }
    void display();
    Increase operator ++();
    Increase operator ++(int);
private:
    int value;
};
//前置
Increase Increase::operator++()
{
    value++;
    return *this;
}
//后置
Increase Increase::operator++(int)
{
    Increase temp;
    temp.value= value ++;
    return temp;
}
void Increase::display()
{
    cout << value <<endl;
}
void main()
{
    Increase a,b,c;
    int i;
    for(i=0;i<10;i++)
    {
        //用c调用前置++运算符
        a = c++;
    }
    cout << "c=" ;
    c.display();
    cout << "a=";
    a.display();

    for(i=0;i<10;i++)
    {
        //用c调用后置++运算符
        b = ++c;
    }
    cout << "c=" ;
    c.display();
    cout << "b=";
    b.display();
}

使用友元函数通过重载++运算符，实现和上面同样的效果

#include <iostream>
using namespace std;

//使用友元函数重载++运算符
class Increase
{
public:
    Increase()
    {
        value =0;
    }
    void display()
    {
        cout << value << endl;
    }
    friend Increase operator++(Increase &i);
    friend Increase operator++(Increase &i,int);
private:
    int value;
};

Increase operator ++(Increase &i)
{
    i.value ++;
    return i;
}
Increase operator ++(Increase &i,int)
{
    Increase temp;
    temp.value = i.value ++;
    return temp;
}
void main()
{
    Increase a,b,c;
    for(int i=0;i<10;i++)
    {
        a = c++;
    }
    cout << "a=";
    a.display();
    cout << "c=";
    c.display();

    for(int i=0;i<10;i++)
    {
        b = ++c;
    }
    cout << "b=";
    b.display();
    cout << "c=";
    c.display();
}

“=”赋值运算符重载用于对象数据的复制

 operator= 必须重载为成员函数

重载函数原型为：

  类名  &  类名  :: operator= ( 类名 ) ;

#include <iostream>
#include <cstring>
using namespace std;

class Name
{
public:
    Name(char* name);
    Name(Name& name);
    Name operator =(Name& name);
    ~Name();
private:
    int size;
    char* name;
};

//重载=运算符
Name Name::operator=(Name& name)
{
    cout << "重载=运算符	"<< name.name << endl;
    //删除当前name的值
    delete this->name;
    //为当前的name初始化指定的大小
    this->name = new char[strlen(name.name)+1];
    //如果参数name的内容不为空的话，将他的值赋值给当前name
    if(this->name!=0)
    {
        strcpy(this->name,name.name);
    } 
    //计算字符的大小
    size = strlen(name.name);
    //调用复制构造函数返回当前的this指针
    return *this;
}

//构造函数
Name::Name(char* name)
{
    cout << "constructing	" << name << endl;
    this->name = new char[strlen(name)+1];
    if(this->name!=0)
    {
        strcpy(this->name,name);
    }
    size = strlen(name);
}
//复制构造函数
Name::Name(Name& name)
{
    cout << "copying	 " << name.name << endl;
    this->name = new char[strlen(name.name)+1];
    if(this->name != 0)
    {
        strcpy(this->name,name.name);
    }
    size = strlen(name.name);
}
//析构函数
Name::~Name()
{
    cout << "distructing	" << this->name<<endl;;
    delete []name;
    size = 0;
}
void main()
{
    Name n1("zhangsan");
    Name n2 = n1;
    Name n3 = ("lisi");
    n3 = n2 = n1;
}

 3.重载流插入和流提取运算符

#include <cstdlib>
#include <iostream>
using namespace std;
class Vector
{
public:
    Vector(int size=1);
    ~Vector();
    int& operator[](int i);
    friend ostream& operator << (ostream& output,Vector& vector);
    friend istream& operator >> (istream& input,Vector& vector);
private:
    int* v;
    int length;
};
Vector::Vector(int size)
{
    if(size<=0||size>100)
    {
        cout << "The size of" << size << "is null!" << endl;
    }else
    {
        v = new int[size];
        length = size;
    }
}
Vector::~Vector()
{
    cout << "析构
";
    delete []v;
    length = 0;
}
int& Vector::operator[](int i)
{
    if(i>=0&&i<length)
    {
        return v[i];
    }else
    {
        cout << "The subscript" << i << "is outside!" << endl;
        exit(0);
    }
}
ostream& operator <<(ostream& output,Vector& vector)
{
    for(int i = 0;i < vector.length; i ++)
    {
        output << vector[i] << " ";
    }
    output << endl;
    return output;
}
istream& operator >>(istream& input,Vector& vector)
{
    for(int i=0;i<vector.length;i++)
    {
        input >> vector[i];
    }
    return input;
}
void main()
{
    int k;
    cout << "Input the length of Vector a:" << endl;
    cin >> k;
    Vector a(k);
    cout <<"Input the elements of Vector a:" << endl;
    //调用重载版本
    cin >> a;
    cout << "Output the elements of Vector a:" << endl;
    //调用重载版本
    cout << a;
}