C++知识点案例笔记-5

1.关系运算符重载

2.类型转换函数重载

3.转换构造函数

4.函数模板

5.显式实例化

6.类模板外定义模板函数

1.关系运算符重载

==关系运算符重载==

//直接（按分数）比较两个对象

#include<iostream>

using namespace std;

class Student

{

public:

    friend ostream& operator<< (ostream& os,const Student& st);

    friend istream& operator>> (istream& is, Student& st);

    friend bool operator == (const Student& st1,const Student& st2);

    friend bool operator != (const Student& st1,const Student& st2);

    friend bool operator >  (const Student& st1,const Student& st2);

    friend bool operator <  (const Student& st1,const Student& st2);

private:

    int id;

    double  score;

};

ostream& operator<< (ostream& os,const Student& st)

{

    os <<"id:"<<st.id<<"score"<<st.score;

    return os;

}

istream& operator>> (istream& is,Student& st)

{

    is >> st.id >> st.score;

    return is;

}

bool operator == (const Student& st1,const Student& st2)

{

    return st1.score == st2.score;

}

bool operator != (const Student& st1,const Student& st2)

{

    return !(st1.score == st2.score);

}

bool operator > (const Student& st1,const Student& st2)

{

    return (st1.score > st2.score);

}

bool operator < (const Student& st1,const Student& st2)

{

    return (st1.score < st1.score);

}

int main()

{

    Student st1,st2;

    cout<<"请输入两名学生的ID和score："<<endl;

    cin>>st1>>st2;

    if (st1 > st2)

    {

        cout<<"st1分数高于st2"<<endl;

    }

    else if(st1 < st2)

    {

        cout<<"st1分数低于st2"<<endl;

    }

    else

    {

        cout<<"两名学生分数相同"<<endl;

    }

    return 0;

}

2.类型转换函数重载

==类型转换函数重载==

#include<iostream>

using namespace std;

class bian

{

private:

    int m,n;

public:

    bian(int m1,int n1):m(m1),n(n1){}

    void show()

    {

        cout<<"bb:"<<endl;cout<<m<<","<<n<<endl;

    }

    operator char()

    {

        return static_cast<char>(m);

    }

};

int main()

{

    bian bb(69,96);

    bb.show();

    char ch = bb;

    cout<<ch<<endl;

    return 0;

}

3.转换构造函数

==转换构造函数==

#include<iostream>

using namespace std;

class jie

{

private:

    int m,n;

public:

    jie(int a, int b):m(a),n(b){}

    jie(double c)

    {

        cout<<"把m转换成字符型，并给n一个值"<<endl;

        m = static_cast<int>(c);

        n = 0;

    }

    void show()

    {

        cout<<m<<" "<<n<<endl;

    }

};

int main()

{

    jie s1(58,68);

    jie s2(2.333);

    cout<<"s1"<<endl;

    s1.show();

    cout<<"s2"<<endl;

    s2.show();

    return 0;

}

4.函数模板

==函数模板==

//目的 函数运行与类型无关

#include<iostream>

using namespace std;

template<typename T>

T add(T x,T y)

{

    return x+y;

}

int main()

{

    cout<<add(5,516)<<endl;

    cout<<add(3.1415,6.011)<<endl;

    return 0;

}

5.显式实例化

==显式实例化==

//指定参数类型，便于不同类型数据类型相加

#include<iostream>

using namespace std;

template<typename T>

T add(T x,T y)

{

    return x+y;

}

template int add<int>(int x,int y);

int main()

{

    cout<<add(5,516)<<endl;

    cout<<add<int>(3.1415,'a')<<endl;

    return 0;

}

6.类模板外定义模板函数

==类模板外定义模板函数==

#include<iostream>

using namespace std;

template<typename T>

class Fly

{

private:

    int size;

    T* str;

public:

    Fly(T fly[],int s);

    void show();

};

//类模板外定义成员函数

template<typename T>

Fly<T>::Fly(T fly[],int s)

{

    str = new T[s];

    size = s ;

    for(int i = 0;i < size; i++)

    {

        str[i] = fly[i];

    }

}

template<typename T>

void Fly<T>::show()

{

    for(int k = 0; k <size; k++)

    {

        cout<<*(str + k)<<endl;

    }

}

int main()

{

    char ffly[]={'a','d','f','e','t'};

    //创建类模板对象

    Fly<char> F1(ffly,5);

    F1.show();

    int jfly[]={5,2,1,1314};

    //创建类模板对象

    Fly<int> F2(jfly,4);

    F2.show();

    return 0;

}

巴特西

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