C++中的增量(++)和减量(–)运算符重载

运算符重载是面向对象编程中的一项功能，它允许程序员重新定义内置运算符以使用用户定义的数据类型。
为什么运算符超载?
假设我们已经定义了一个Integer类来处理整数操作。我们可以使用add()，subtract()，multipli()和divide()函数来处理相应的操作。但是，为了使代码更直观并增强可读性，最好使用与给定操作(分别为+，-，*，/)相对应的运算符，即，我们可以替换以下代码
例子：

Replace
i5 = divide(add(i1, i2), subtract(i3, i4))

by a simpler code:
i5 = (i1 + i2) / (i3 - i4) 

重载增量运算符

前缀(++ i)和后缀(i ++)的运算符符都相同。因此，我们需要两个不同的函数定义来区分它们。这是通过在后缀版本中传递虚拟int参数来实现的。
这是演示相同代码的代码。
预增量超载

CPP

// C++ program to demonstrate
// prefix increment operator overloading
 
#include 
using namespace std;
 
class Integer {
private:
    int i;
 
public:
    // Parameterised constructor
    Integer(int i = 0)
    {
        this->i = i;
    }
 
    // Overloading the prefix operator
    Integer operator++()
    {
        Integer temp;
        temp.i = ++i;
        return temp;
    }
 
    // Function to display the value of i
    void display()
    {
        cout << "i = " << i << endl;
    }
};
 
// Driver function
int main()
{
    Integer i1(3);
 
    cout << "Before increment: ";
    i1.display();
 
    // Using the pre-increment operator
    Integer i2 = ++i1;
 
    cout << "After pre increment: ";
    i2.display();
}

输出：

Before increment: i = 3
After pre increment: i = 4

后增量超载

CPP

// C++ program to demonstrate
// postfix increment operator overloading
 
#include 
using namespace std;
 
class Integer {
private:
    int i;
 
public:
    // Parameterised constructor
    Integer(int i = 0)
    {
        this->i = i;
    }
 
    // Overloading the postfix operator
    Integer operator++(int)
    {
        Integer temp;
        temp.i = i++;
        return temp;
    }
 
    // Function to display the value of i
    void display()
    {
        cout << "i = " << i << endl;
    }
};
 
// Driver function
int main()
{
    Integer i1(3);
 
    cout << "Before increment: ";
    i1.display();
 
    // Using the post-increment operator
    Integer i2 = i1++;
 
    cout << "After post increment: ";
    i2.display();
}

输出：

Before increment: i = 3
After post increment: i = 3

重载减量运算符

同样，我们也可以按如下方式重载减量运算符
递减前超载

CPP

// C++ program to demonstrate
// prefix decrement operator overloading
 
#include 
using namespace std;
 
class Integer {
private:
    int i;
 
public:
    // Parameterised constructor
    Integer(int i = 0)
    {
        this->i = i;
    }
 
    // Overloading the prefix operator
    Integer operator--()
    {
        Integer temp;
        temp.i = --i;
        return temp;
    }
 
    // Function to display the value of i
    void display()
    {
        cout << "i = " << i << endl;
    }
};
 
// Driver function
int main()
{
    Integer i1(3);
 
    cout << "Before decrement: ";
    i1.display();
 
    // Using the pre-decrement operator
    Integer i2 = --i1;
 
    cout << "After pre decrement: ";
    i2.display();
}

输出：

Before decrement: i = 3
After pre decrement: i = 2

递减后重载

CPP

// C++ program to demonstrate
// postfix decrement operator overloading
 
#include 
using namespace std;
 
class Integer {
private:
    int i;
 
public:
    // Parameterised constructor
    Integer(int i = 0)
    {
        this->i = i;
    }
 
    // Overloading the postfix operator
    Integer operator--(int)
    {
        Integer temp;
        temp.i = i--;
        return temp;
    }
 
    // Function to display the value of i
    void display()
    {
        cout << "i = " << i << endl;
    }
};
 
// Driver function
int main()
{
    Integer i1(3);
 
    cout << "Before decrement: ";
    i1.display();
 
    // Using the post-decrement operator
    Integer i2 = i1--;
 
    cout << "After post decrement: ";
    i2.display();
}

输出：

Before decrement: i = 3
After post decrement: i = 3

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