C++语言基础 例程 重载流插入运算符和流提取运算符

贺老师的教学链接  本课讲解

重载流插入运算符“<<”

#include <iostream>
using namespace std;
class Complex
{
public:
    Complex( )
    {
        real=0;
        imag=0;
    }
    Complex(double r,double i)
    {
        real=r;
        imag=i;
    }
    Complex operator + (Complex &c2);                    //运算符“+”重载为成员函数
    friend ostream& operator << (ostream&, const Complex&);     //运算符“<<”重载为友元函数
private:
    double real;
    double imag;
};

Complex Complex::operator + (Complex &c2)               //定义运算符“+”重载函数
{
    return Complex(real+c2.real,imag+c2.imag);
}

ostream& operator << (ostream& output,const Complex& c)       //定义运算符“<<”重载函数
{
    output<<"("<<c.real<<"+"<<c.imag<<"i)";
    return output;
}

int main( )
{
    Complex c1(2,4),c2(6,10),c3;
    c3=c1+c2;
    cout<<c1<<'+'<<c2<<'='<<c3<<endl;
    return 0;
}
/* 去掉operator << 中的const后，将不能支持cout<<c1+c2<<endl;式的输出  */
 

重载流提取运算符“>>”

#include <iostream>
using namespace std;
class Complex
{
public:
    friend ostream& operator << (ostream&,const Complex&);    //声明重载运算符“<<”
    friend istream& operator >> (istream&,Complex&);    //声明重载运算符“>>”
private:
    double real;
    double imag;
};
ostream& operator << (ostream& output,const Complex& c)       //定义重载运算符“<<”
{
    output<<"("<<c.real<<"+"<<c.imag<<"i)";
    return output;
}
istream& operator >> (istream& input,Complex& c)     //定义重载运算符“>>”
{
    cout<<"input real part and imaginary part: ";
    input>>c.real>>c.imag;
    return input;
}
int main( )
{
    Complex c1,c2;
    cin>>c1>>c2;
    cout<<"c1="<<c1<<endl;
    cout<<"c2="<<c2<<endl;
    return 0;
}

对复数输入输出的完善

#include <iostream>
using namespace std;
class Complex
{
public:
    Complex( )
    {
        real=0;
        imag=0;
    }
    Complex(double r,double i)
    {
        real=r;
        imag=i;
    }
    Complex operator + (Complex &c2);                   //运算符“+”重载为成员函数
    friend ostream& operator << (ostream&,const Complex&);    //声明重载运算符“<<”
    friend istream& operator >> (istream&,Complex&);    //声明重载运算符“>>”
private:
    double real;
    double imag;
};

Complex Complex::operator + (Complex &c2)               //定义运算符“+”重载函数
{
    return Complex(real+c2.real,imag+c2.imag);
}

ostream& operator << (ostream& output, const Complex& c)       //定义重载运算符“<<”
{
    output<<"("<<c.real;
    if(c.imag>=0) output<<"+";                  //虚部为正数时，在虚部前加“+”号
    output<<c.imag<<"i)";                 //虚部为负数时，在虚部前不加“+”号
    return output;
}
istream& operator >> (istream& input,Complex& c)     //定义重载运算符“>>”
{
    int a,b;
    char sign,i;
    do
    {
        cout<<"input a complex number(a+bi或a-bi):";
        input>>a>>sign>>b>>i;
    }
    while(!((sign=='+'||sign=='-')&&i=='i'))
    c.real=a;
    c.imag=(sign=='+')?b:-b;
    return input;
}

int main( )
{
    Complex c1,c2(6,10),c3;
    cin>>c1
    cout<<"c1="<<c1<<endl;
    cout<<"c2="<<c2<<endl
    c3=c1+c2;
    cout<<"c1+c2="<<c3<<endl;
    return 0;
}