详解C++编程中一元运算符的重载
可重载的一元运算符如下：
- !（逻辑“非”）
- &（取址）
- ~（二进制反码）
- *（取消指针引用）
- +（一元加）
- -（一元求反）
- ++（递增）
- --（递减）
- 转换运算符
后缀递增和递减运算符（++ 和 ––）在递增和递减中单独处理，下面会讲到。
以下规则适用于所有其他一元运算符。若要将一元运算符函数声明为非静态成员，则必须用以下形式声明它：
ret-type operator op ()
其中 ret-type 是返回类型，op 是上表中列出的运算符之一。
若要将一元运算符函数声明为全局函数，则必须用以下形式声明它：
ret-type operator op (arg )
其中 ret-type 和 op 如上所述用于成员运算符函数，arg 是要参与运算的类类型的参数。
注意
一元运算符的返回类型没有限制。例如，逻辑“非”(!) 返回整数值是合理的，但并非强制性的。
递增和递减运算符重载
由于递增和递减运算符各有两个变量，因此它们属于一个特殊类别：
- 前置递增和后置递增
- 前置递减和后置递减
编写重载的运算符函数时，为这些运算符的前缀和后缀版本实现单独的版本很有用。若要区分这两者，请遵循以下规则：运算符的前缀形式与声明任何其他一元运算符的方式完全相同；后缀形式接受 int 类型的其他参数。
注意
当为递增或递减运算符的前缀形式指定重载运算符时，其他参数的类型必须是 int；指定任何其他类型都将产生错误。
以下示例显示如何为 Point 类定义前缀和后缀递增和递减运算符：
// increment_and_decrement1.cpp
class Point
{
public:
// Declare prefix and postfix increment operators.
Point& operator++(); // Prefix increment operator.
Point operator++(int); // Postfix increment operator.
// Declare prefix and postfix decrement operators.
Point& operator--(); // Prefix decrement operator.
Point operator--(int); // Postfix decrement operator.
// Define default constructor.
Point() { _x = _y = 0; }
// Define accessor functions.
int x() { return _x; }
int y() { return _y; }
private:
int _x, _y;
};
// Define prefix increment operator.
Point& Point::operator++()
{
_x++;
_y++;
return *this;
}
// Define postfix increment operator.
Point Point::operator++(int)
{
Point temp = *this;
++*this;
return temp;
}
// Define prefix decrement operator.
Point& Point::operator--()
{
_x--;
_y--;
return *this;
}
// Define postfix decrement operator.
Point Point::operator--(int)
{
Point temp = *this;
--*this;
return temp;
}
int main()
{
}
可使用以下函数头在文件范围中（全局）定义同一运算符：
friend Point& operator++( Point& ) // Prefix increment friend Point& operator++( Point&, int ) // Postfix increment friend Point& operator--( Point& ) // Prefix decrement friend Point& operator--( Point&, int ) // Postfix decrement
表示递增或递减运算符的后缀形式的 int 类型的参数不常用于传递参数。它通常包含值 0。但是，可按以下方式使用它：
// increment_and_decrement2.cpp
class Int
{
public:
Int &operator++( int n );
private:
int _i;
};
Int& Int::operator++( int n )
{
if( n != 0 ) // Handle case where an argument is passed.
_i += n;
else
_i++; // Handle case where no argument is passed.
return *this;
}
int main()
{
Int i;
i.operator++( 25 ); // Increment by 25.
}
除显式调用之外，没有针对使用递增或递减运算符来传递这些值的语法，如前面的代码所示。实现此功能的更直接的方法是重载加法/赋值运算符 (+=)。
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
AI Hentai Generator
Generate AI Hentai for free.
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
How to implement the Strategy Design Pattern in C++?
Jun 06, 2024 pm 04:16 PM
The steps to implement the strategy pattern in C++ are as follows: define the strategy interface and declare the methods that need to be executed. Create specific strategy classes, implement the interface respectively and provide different algorithms. Use a context class to hold a reference to a concrete strategy class and perform operations through it.
Similarities and Differences between Golang and C++
Jun 05, 2024 pm 06:12 PM
Golang and C++ are garbage collected and manual memory management programming languages respectively, with different syntax and type systems. Golang implements concurrent programming through Goroutine, and C++ implements it through threads. Golang memory management is simple, and C++ has stronger performance. In practical cases, Golang code is simpler and C++ has obvious performance advantages.
How to implement nested exception handling in C++?
Jun 05, 2024 pm 09:15 PM
Nested exception handling is implemented in C++ through nested try-catch blocks, allowing new exceptions to be raised within the exception handler. The nested try-catch steps are as follows: 1. The outer try-catch block handles all exceptions, including those thrown by the inner exception handler. 2. The inner try-catch block handles specific types of exceptions, and if an out-of-scope exception occurs, control is given to the external exception handler.
How to iterate over a C++ STL container?
Jun 05, 2024 pm 06:29 PM
To iterate over an STL container, you can use the container's begin() and end() functions to get the iterator range: Vector: Use a for loop to iterate over the iterator range. Linked list: Use the next() member function to traverse the elements of the linked list. Mapping: Get the key-value iterator and use a for loop to traverse it.
How to use C++ template inheritance?
Jun 06, 2024 am 10:33 AM
C++ template inheritance allows template-derived classes to reuse the code and functionality of the base class template, which is suitable for creating classes with the same core logic but different specific behaviors. The template inheritance syntax is: templateclassDerived:publicBase{}. Example: templateclassBase{};templateclassDerived:publicBase{};. Practical case: Created the derived class Derived, inherited the counting function of the base class Base, and added the printCount method to print the current count.
What are the common applications of C++ templates in actual development?
Jun 05, 2024 pm 05:09 PM
C++ templates are widely used in actual development, including container class templates, algorithm templates, generic function templates and metaprogramming templates. For example, a generic sorting algorithm can sort arrays of different types of data.
How to handle cross-thread C++ exceptions?
Jun 06, 2024 am 10:44 AM
In multi-threaded C++, exception handling is implemented through the std::promise and std::future mechanisms: use the promise object to record the exception in the thread that throws the exception. Use a future object to check for exceptions in the thread that receives the exception. Practical cases show how to use promises and futures to catch and handle exceptions in different threads.
How to access elements in C++ STL container?
Jun 05, 2024 pm 06:04 PM
How to access elements in C++ STL container? There are several ways to do this: Traverse a container: Use an iterator Range-based for loop to access specific elements: Use an index (subscript operator []) Use a key (std::map or std::unordered_map)
