修改文件: _posts/2015-10-31-friend-function.md

Author: lanyuanxiaoyao

_posts/2015-10-31-friend-function.md

@@ -0,0 +1,95 @@
+---
+layout: post
+title: C++ 成员函数与友元函数
+date: 2015-10-31 11:25
+categories: C++
+tags: [C++]
+---
+**在[C++ 运算符重载]一文的基础上，增加两个判断复数是否相等的函数，一个为成员函数，一个为友元函数**
+```cpp
+#include<iostream>
+using namespace std;
+class Complex { //复数类
+    private:    //定义私有成员变量
+        double real;    //定义实数部
+        double image;   //定义虚数部
+    public:
+        Complex(void):real(0),image(0) {}   //定义参数为空的构造函数
+        Complex(double rp):real(rp),image(0) {} //定义只有实数部的构造函数
+        Complex(double rp,double ip):real(rp),image(ip) {}  //定义参数同时制定实数和虚数的构造函数
+        ~Complex() {}  //定义析构函数（无特定操作可不写）
+
+        Complex operator+(const Complex &x) const;  //声明重载运算符+
+        Complex operator-(const Complex &x) const;  //声明重载运算符-
+        Complex operator*(const Complex &x) const;  //声明重载运算符*
+        Complex operator/(const Complex &x) const;  //声明重载运算符/
+        bool operator==(const Complex &x) const;    //声明重载运算符==
+        Complex& operator+=(const Complex &x);      //声明重载运算符+=
+
+        Complex& operator-=(const Complex &x);      //声明重载运算符-=
+        Complex& operator*=(const Complex &x);      //声明重载运算符*=
+
+        bool Charge_member(Complex &x); //声明判断复数相等的成员函数
+        friend bool Charge_friend(Complex &x, Complex &y);  //声明类外的一个判断相等的函数为友元函数（这个函数不是类的成员函数，是将类外的某个函数定义为自己的友元函数,只有定义为友元函数之后才能访问类的私有变量）
+
+        void Print(void) const; //定义类成员输出函数
+};
+inline Complex Complex::operator+(const Complex &x) const { //重载运算符的实际函数体
+    return Complex(real + x.real, image + x.image);
+}
+inline Complex Complex::operator-(const Complex &x) const {
+    return Complex(real - x.real, image - x.image);
+}
+inline Complex Complex::operator*(const Complex &x) const {
+    return Complex(real * x.real - image * x.image, real * x.image + image * x.real);
+}
+Complex Complex::operator/(const Complex &x) const {
+    double m;
+    m = x.real * x.real + x.image * x.image;
+    return Complex((real * x.real + image * x.image) / m, (image * x.real - real * x.image) / m);
+}
+inline bool Complex::operator==(const Complex &x) const {   //运算符==判断是否相等，应返回bool类型的值
+    return bool(real == x.real && image == x.image);
+}
+Complex& Complex::operator+=(const Complex &x) {    //因为+=的结果是将被加数加在自己的成员函数上，所以返回自身的指针
+    real += x.real;
+    image += x.image;
+    return *this;
+}
+Complex& Complex::operator-=(const Complex &x) {
+    real -= x.real;
+    image -= x.image;
+    return *this;
+}
+Complex& Complex::operator*=(const Complex &x) {
+    real = real * x.real - image * x.image;
+    image = real * x.image + image * x.real;
+    return *this;
+}
+
+inline bool Complex::Charge_member(Complex &x) {    //直接判断
+    return bool(real == x.real && image == x.image);
+}
+
+bool Charge_friend(Complex &x, Complex &y) {    //需声明两个复数类的参数
+    return bool(y.real == x.real && y.image == x.image);
+}
+
+void Complex::Print(void) const {   //输出函数
+    cout<<"("<<real<<","<<image<<"i)"<<endl;
+}
+
+int main(void) {    //测试函数
+    Complex a(3, 5), b(2, 3), c;
+    c = a + b * a / b - b;
+    c.Print();
+
+    if(a.Charge_member(b)) cout<<"这两个复数是相等的(成员函数)"<<endl;
+    else  cout<<"这两个复数是不相等的(成员函数)"<<endl;
+
+    if(Charge_friend(a,b))  cout<<"这两个复数是相等的(友元函数)"<<endl;
+    else  cout<<"这两个复数是不相等的(友元函数)"<<endl;
+
+    return 0;
+}
+```