C++學習:運算符重載

簡介:

類是使用者自定義的資料類型,使用重載運算符好可以實作一下的邏輯

1:對象3 = 對象1+對象2+...如描述複數的類,描述字元串的類等等
2:提高程式的可讀性.

重載指派運算符

如果一個類沒有指派運算符,系統會預設提供一個

如果一個類已經提供了一個拷貝構造函數(非預設),那麼也需要提供一個重載的指派運算符

如:

Student & Student ::operate=(const Student &stu){
    if(this == &stu){
        return *this;
    }        
    delete[] m_data;
    int length = strlen(other.m_data);
    m_data = new char[length+1];
    strcpy(m_data,other.m_data);
    return *this;
}

提示:

本文部落客:章飛_906285288

部落格位址:http://blog.csdn.net/qq_29924041

運算符重載

運算符重載特點及注意事項:

C++語言規定:

1:重載的運算符要保持原來運算符的意義
    2:隻能對已有的運算符,而不能對新的運算符
    3:重載運算符不會改變原先的優先級和結合性

運算符重載的形式:

1:成員函數形式
2:友元函數的形式

運算符重載的限制:

通過一張圖的形式展示下:

C++學習:運算符重載

從上面的圖中可以看到,以上的一些運算符号都是可以進行重載的.

而不能重載的運算符有以下一些:

C++學習:運算符重載

以上兩張圖都是取自百度圖檔

簡單歸納一下一些常用的可重載運算符:

+           -            *
        =           >           <
        <=         >=         <<
        >>         []           ()
        ->          new       new[]
        delete    delete[]

執行個體代碼部分:

友元函數重載

/*
 * ===========================================================================
 *
 *       Filename:  studentTest.cpp
 *    Description:  
 *        Version:  1.0
 *        Created:  2017年06月13日 23時01分07秒
 *       Revision:  none
 *       Compiler:  gcc
 *         Author:   (), 
 *        Company:  
 *
 * ===========================================================================
 */

#include<iostream>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
using namespace::std;

class Student{
  public:
     Student(const char* name = "NULL",int stu_math_score = ):math_score(stu_math_score){
        m_name = (char *)malloc(strlen(name)*sizeof(char));
        strncpy(m_name,name,strlen(name)*sizeof(char));
        cout<<"Student constructor"<<endl;
     }

     ~Student(){
       free(m_name);
       cout<<"Student desctructor"<<endl;
     }

    Student(const Student &stu){
      //深拷貝
        m_name = (char *)malloc(strlen(stu.m_name)*sizeof(char));
        strncpy(m_name,stu.m_name,strlen(stu.m_name)*sizeof(char));
        math_score = stu.math_score;
    }

    void print_stu_info(){
      cout<<"================="<<endl;
      cout<<"student name:"<<m_name<<endl;
      cout<<"student math_score:"<<math_score<<endl;
      cout<<"================="<<endl;
    }
     friend int operator+(Student &,Student&);//輸出兩個學生的成績和
     friend int operator-(Student &,Student&);//輸出兩個學生的成績差
     friend bool operator>(Student &,Student &);//判斷第一個學生的數學成績是否大于第二個學生的數學成績
     friend Student operator<(Student &,Student &);//将數學成績少的學生成績輸出
  private:
     char *m_name;
     int math_score;

};

int operator+(Student &stu1,Student &stu2){
  int ret = stu1.math_score + stu2.math_score;
  return ret;
}

int operator-(Student &stu1,Student &stu2){
  int ret = stu1.math_score - stu2.math_score;
  return ret;
}

bool operator>(Student &stu1,Student &stu2){
  return stu1.math_score > stu2.math_score;
}

Student operator<(Student &stu1,Student &stu2){
  Student stu = stu1.math_score < stu2.math_score ? stu1 :stu2;
  return stu;
}


int main(int agrc,char *argv[]){
  Student stu_zhangsan("zhangsan",);
  stu_zhangsan.print_stu_info();
  Student stu_lisi("lisi",);
  stu_lisi.print_stu_info();

  int result = stu_zhangsan +stu_lisi;
  cout<<"add:"<<result <<endl;

  result = stu_zhangsan - stu_lisi;
  cout<<"sub:"<<result <<endl;

  Student stu = stu_zhangsan < stu_lisi;
  stu.print_stu_info();

  bool is_greater_than = stu_zhangsan > stu_lisi;

  cout<<is_greater_than<<endl;

  return ;
}

輸出的結果為:

Student constructor

=================

student name:zhangsan

student math_score:85

=================

Student constructor

=================

student name:lisi

student math_score:83

=================

add:168

sub:2

=================

student name:lisi

student math_score:83

=================

Student desctructor

從上面的測試代碼中可以很直覺的看到,stu_zhansan 和stu_lisi兩個對象,他們之間可以去直接進行運算符之間的加減.很直覺.也是使用友元函數來進行的操作的(友元函數是不依賴于類的,注意友元函數在定義的時候的寫法)

成員運算符重載

二進制成員運算符重載的時候,參數隻要傳一個就行了,另外一個由this指針進行傳入

/*
 * ===========================================================================
 *
 *       Filename:  studentTest.cpp
 *    Description:  
 *        Version:  1.0
 *        Created:  2017年06月13日 23時01分07秒
 *       Revision:  none
 *       Compiler:  gcc
 *         Author:   (), 
 *        Company:  
 *
 * ===========================================================================
 */

#include<iostream>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
using namespace::std;

class Student{
  public:
     int english_score;
     int math_score;
     Student(const char* name = "NULL",int stu_math_score = ,int english_score = ):math_score(stu_math_score),english_score(english_score){
        m_name = (char *)malloc(strlen(name)*sizeof(char));
        strncpy(m_name,name,strlen(name)*sizeof(char));
        cout<<"Student constructor"<<endl;
     }

     ~Student(){
       free(m_name);
       cout<<"Student desctructor"<<endl;
     }

    Student(const Student &stu){
      //深拷貝
        m_name = (char *)malloc(strlen(stu.m_name)*sizeof(char));
        strncpy(m_name,stu.m_name,strlen(stu.m_name)*sizeof(char));
        math_score = stu.math_score;
        english_score = stu.english_score;
    }

    void print_stu_info(){
      cout<<"================="<<endl;
      cout<<"student name:"<<m_name<<endl;
      cout<<"student math_score:"<<math_score<<endl;
      cout<<"student english_score:"<<english_score<<endl;
      cout<<"================="<<endl;
    }

    //二進制運算符重載的時候隻需要傳一個參數,另一個參數由this指針進行傳入
    int operator+(int english);//輸出學生的成績和
    int operator-(int english);//輸出學生的成績差
    bool operator>(int english);//判斷學生的數學成績是否大于學生的英語成績
    friend Student operator<(Student &,Student &);//将數學成績少的學生成績輸出

    int operator()(int english);//對象可以使用(),來進行運算符重載,利用重載()來建構可變參數清單
    int operator()(int a,int b,int c,int d);
  private:
     char *m_name;
};

int Student::operator+(int english){
  int ret = this->math_score + english;
  return ret;
}

int Student::operator-(int english){
  int ret = this->math_score - english;
  return ret;
}

bool Student::operator>(int english){
  return this->math_score > english;
}

Student operator<(Student &stu1,Student &stu2){
  Student stu = stu1.math_score < stu2.math_score ? stu1 :stu2;
  return stu;
}

int Student::operator()(int b) {
  return this->math_score+b;
}

int Student::operator()(int a,int b,int c,int d){
  return a+b+c+d;
}

int main(int agrc,char *argv[]){
  Student stu_zhangsan("zhangsan",,);
  stu_zhangsan.print_stu_info();
  int ret = stu_zhangsan.math_score - stu_zhangsan.english_score;
  cout<<"sub:"<<ret<<endl;
  ret =  stu_zhangsan.math_score +stu_zhangsan.english_score;
  cout<<"add:"<<ret<<endl;

  bool  result= stu_zhangsan.math_score > stu_zhangsan.english_score;
  cout<<"bool:"<<result<<endl;

  //直接通過()進行運算
  ret  = stu_zhangsan();
  cout<<"ret:"<<ret<<endl;

  ret = stu_zhangsan(,,,);
  cout<<"ret2:"<<ret<<endl;
  return ;
}

輸出的結果為:

Student constructor
 =================
student name:zhangsan
student math_score:85
student english_score:90
=================
sub:-5
add:175
bool:0
ret:175
ret2:100
Student desctructor

C++學習:運算符重載

運算符重載

友元函數重載

成員運算符重載

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