06C++运算符重载

C++运算符重载

什么是运算符重载

赋予运算符具有操作自定义类型数据功能

运算符重载的实质是什么?

	运算符重载的实质本身就是函数调用
运算符重载函数的写法
	函数返回值   函数名(函数参数)
函数返回值 :运算完成后的值决定的				Complex
函数名  ： operator 加上重载运算符组成函数名  operator+ 
参数     ：看运算符的操作数,具体参数个数是要看你重载函数形式是什么
函数体    : 写运算符具体想要的操作

友元函数重载运算符

类成员函数重载运算符

<< 运算符重载就是在 成员函数或者友元函数 中实现 你想在外面对 类对象实现的操作。

#include <iostream>
using namespace std;
class overload
{
public:
	// 构造函数
	overload(int a = 0, int b = 0) :a(a), b(b) {}
	void print()
	{
		cout << a <<" " << b << endl;
	}
	friend overload  operator+ (overload one, overload two);
	  //类成员函数重载，参数个数等于操作减一
	bool operator> (overload  object)
	{
		if (this->a > object.a)
		{
			return true;
		}
		else if (this->a == object.a && this->b > object.b)
		{
			return true;
		}
		else
		{
			return false;
		}
	}
protected:
	int a;
	int b;
};
//友元重载： 参数个数就是操作数据
overload  operator+ (overload one, overload two)
{  
	//  在函数中实现    对象的成员相加
	return overload(one.a + two.a, one.b + two.b);
}

int main()
{
	overload one(3, 3);
	overload two(2, 7);
	overload three;
	three = one + two;    //overload  重载函数的隐式调用
	three.print();   //  3+2     3+7
	//显式调用
	overload result;
	result = operator+(one+one, two+one);//  3+3  3+3, 3+2     3+7
	result.print();               // 6+5,4+10
	if (one > two)	//one > two  是bool
	{
		cout << "one 比较大" << endl;
	}
	//对象可以表示一个数据，所以参数应该少一个
	if (one.operator>(two))
	{
		cout << "one比较大" << endl;
	}
	return 0;
}

特殊运算符重载

• 流运算符重载
  • cin类型 ： istream类的对象
  • cout类型:ostream类的对象
  • 流运算符 >> <<

必须采用友元函数形式重载

• 他运算符
• = () -> [] 只能采用类的成员函数形式重载
• 流重载采用友元方式
  +. .* ?: :: 不能重载

#include <iostream>
#include <string>
using namespace std;
class Boy
{
public:
	// constraction fun
	Boy(string name = "", int age = 18) :name(name), age(age) {}
	friend istream& operator>>(istream& in, Boy& mm);
	friend ostream& operator<<(ostream& out, Boy& mm);
protected:
	string name;
	int age;
};

istream& operator>>(istream& in, Boy& mm)
{
	in >> mm.name >> mm.age;
	return in;
}
ostream& operator<<(ostream& out, Boy& mm)
{
	out << mm.name << "\t" << mm.age << endl;
	return out;
}

int main()
{
	string str;
	cout << "inter a string:";
	cin >> str;
	cout << str << endl;
	Boy bb;  //  创建对象
	// 对对象直接输入 输出
	cout << "inter a person name and age:";
	cin >> bb;   	//void  operator>>(istream& in,Boy& bb)
	cout <<bb;		//void  operator<<(ostream& out,Boy& bb)
	cout << "inter a string and a name age:";
	cin >> str >> bb;
	cout << str << endl << bb;
	return 0;
}

+ ++ --运算符重载

• 问题: 前置和后置怎么区分？
• 解决办法：
  ++ 增加无用参数 int去表示当前运算符重载是后置操作

#include <iostream>
#include <string>
using namespace std;
class Frend
{
public:
	Frend(string name, int age) :name(name), age(age) {}
	friend ostream& operator<<(ostream& out, Frend& object)
	{
		out << object.name << "\t" << object.age << endl;
		return out;
	}
	Frend operator++(int)	//需要一个无用参数 充当标记
	{
		int num = age;
		age++;
		return Frend(name, num);
		//上面三行等效下面一行
		//return MM(name,age++);
	}
	Frend operator++()
	{
		return Frend(name, ++age);
	}
	//类的对象的隐式转换  operator
	operator int()
	{
		return age;
	}
protected:
	string name;
	int age;
};
int main()
{
	Frend fr("威少", 19);
	cout << fr << endl;
	int num = 1;
	int result = num++;   //result=1  num=2
	cout << result << "\t" << num << endl;
	result = ++num;       //result=3  num=3
	cout << result << "\t" << num << endl;
	//   object 由 fr 来初始化
	Frend  object = fr++;
	cout << "Frend  object = fr++;" << object << fr;   //age=18  fr: 19
	object = ++fr;        //age:20   fr: 20
	cout <<"object = ++fr;"<< object << fr;
	//this_thread::sleep_for(3s);
	cout << "3s结束" << endl;
	Frend  boy("weishao", 20);
	int boyAge = boy;	//类的对象的隐式转换  operator
	cout << boyAge << endl;

	return 0;
}

• 文本重载 （新标准中的，稍微落后一点开发工具不适用）

#include <iostream>
#include <string>
#include <chrono>
#include <thread>
using namespace std;
//文本重载
unsigned long long  operator"" _h(unsigned long long num)
{
	return 60 * 60 * num;
}
unsigned long long  operator"" _min(unsigned long long num)
{
	return 60 * num;
}
int main()
{
	//this_thread::sleep_for(7s);
	cout << "7s结束" << endl;

	int second = 1_h;
	cout << "小时数：1";
	cout << second << "s" << endl;
	cout << "1_h + 18_min + 30=";
	int sum = 1_h + 18_min + 30;
	cout << sum << "s" << endl;
	return 0;
}

重载实战： 封装一个Array类，实现定长数组的操作

#include <iostream>
using namespace std;
class Array
{
public:
	Array() {}
	Array(int arraySize) 
	{
		this->arraySize = arraySize;
		memory = new int[arraySize];
	}
	int& operator[](int index) 
	{
		return memory[index];
	}
	int size() 
	{
		return arraySize;
	}
	friend ostream& operator<<(ostream& out, Array& object) 
	{
		for (int i = 0; i < object.size(); i++) 
		{
			out << object.memory[i] << " ";
		}
		out << endl;
		return out;
	}
	friend istream& operator>>(istream& in, Array& object) 
	{
		for (int i = 0; i < object.size(); i++)
		{
			in >> object.memory[i];
		}
		return  in;
	}
	Array& operator+(Array& object) 
	{
		Array* temp=new Array(this->size() + object.size());
		int count = 0;
		for (int i = 0; i < this->size(); i++) 
		{
			temp->memory[count++] = this->memory[i];
		}
		for (int i = 0; i < object.size(); i++) 
		{
			temp->memory[count++] = object.memory[i];
		}
		return *temp;
	}

	Array(Array& object) 
	{
		this->arraySize = object.arraySize;
		this->memory = new int[this->arraySize];
		for (int i = 0; i < object.size(); i++) 
		{
			this->memory[i] = object.memory[i];
		}
	}
	void operator=(Array& object) 
	{
		this->arraySize = object.arraySize;
		this->memory = new int[this->arraySize];
		for (int i = 0; i < object.size(); i++)
		{
			this->memory[i] = object.memory[i];
		}
	}
	~Array()
	{
		delete[] memory;
	}
protected:
	int arraySize;
	int* memory; //memory[i]
};

int main() 
{
	//以下测试代码要能够成功运行
	Array array(4);
	for (int i = 0; i < array.size(); i++)
	{
		cin >> array[i];   //array[i] 最终返回一个memory[i]
	}
	for (int i = 0; i < array.size(); i++)
	{
		cout << array[i];	////array[i] 最终返回一个memory[i]
	}
	cout << endl;
	//实现数组的连接
	Array one(3);   //输入1 2 3 
	cin >> one;
	Array two(4);   //输入2 3 4 5
	cin >> two;
	Array sum = one+two;
	cout << sum ;  //打印1 2 3 2 3 4
	Array num;
	num = sum;
	cout << num ;
	return 0;
}