c++第九章-（运算符重载）

浏览数：23 / 时间：2015年06月08日

一些规则

1.c++不允许用户自己定义新的运算符，只能对已有的c++运算符进行重载。

2.除了五个运算符不允许重载外，其他运算符允许重载：

.成员访问运算符
*成员指针访问运算符
::与运算符
sizeof尺寸运算符
?:条件运算符

3.重载运算符必须和用户定义的自定义类型的对象一起使用。（也就是说，参数不能全部都是c++的标准类型，这样约定是为了防止用户修改用于标准类型结构的运算符性质）

4.为什么运算符重载函数有两个参数，只需有一个参数？

其实是有一个参数是隐含着的，运算符函数是用this指针隐式地访问类对象的成员。

class Complex
{
public:
    Complex();
    Complex(double r,double i);
    Complex operator+(Complex &d);
    void print();
private:
    double real;
    double imag;
};

Complex::Complex()
{
    real = 0;
    imag = 0;
}
Complex::Complex(double r,double i)
{
    real = r;
    imag = i;
}
Complex Complex::operator+(Complex &d)
{
    Complex c;
    
    c.real = real + d.real;
    c.imag = imag + d.imag;
    
    return c;
}

void Complex::print()
{
    std::cout << "(" << real << "," << imag << "i)\n";
}
int main(int argc, const char * argv[])
{
    Complex c1(3,4),c2(5,-10),c3;
    c3 = c1 + c2;
    
    std::cout << "c1 = ";
    c1.print();
    std::cout << "c2 = ";
    c2.print();
    std::cout << "c1 + c2 = ";
    c3.print();
    
    return 0;
}

有理数运算demo

#include <stdlib.h>

class Rational
{
public:
    Rational(int num,int denom);//num用于分子，denom用于分母
    
    Rational operator+(Rational rhs);
    Rational operator-(Rational rhs);
    Rational operator*(Rational rhs);
    Rational operator/(Rational rhs);
    
    void print();
private:
    void normalize();//负责对分数简化
    int numerator;
    int denominator;
};

Rational::Rational(int num,int denom)
{
    this->numerator = num;
    this->denominator = denom;
    
    normalize();
}

Rational Rational::operator+(Rational rhs)
{
    int a = numerator;
    int b = denominator;
    int c = rhs.numerator;
    int d = rhs.denominator;
    
    int e = a * b + c * d;
    int f = b * d;
    
    return Rational(e,f);
}
Rational Rational::operator-(Rational rhs)
{
    rhs.numerator = -rhs.numerator;

    return operator+(rhs);
}
Rational Rational::operator*(Rational rhs)
{
    int a = numerator;
    int b = denominator;
    int c = rhs.numerator;
    int d = rhs.denominator;
    
    int e = a * c;
    int f = b * d;
    
    return Rational(e,f);
}
Rational Rational::operator/(Rational rhs)
{
    int t = rhs.numerator;
    rhs.numerator = rhs.denominator;
    rhs.denominator = t;
    
    return operator*(rhs);
}
void Rational::print()
{
    if (numerator % denominator == 0)
    {
        std::cout << numerator / denominator;
    }
    else
    {
        std::cout << numerator << "/" << denominator;
    }
}

void Rational::normalize()
{
    if (denominator < 0)//确保分母为正
    {
        numerator = -numerator;
        denominator = -denominator;
    }
    //欧几里德算法
    int a = abs(numerator);//求绝对值
    int b = abs(denominator);
    
    //求最大公约数
    while (b > 0)
    {
        int t = a % b;
        a = b;
        b = t;
    }
    
    //分子、分母分别除于最大公约数得到最简化分数
    numerator /= a;
    denominator /= a;
}

int main(int argc, const char * argv[])
{
    Rational f1(2,16);
    Rational f2(7,8);
    
    Rational res = f1 + f2;
    f1.print();
    std::cout << " + ";
    f2.print();
    std::cout << " = ";
    res.print();
    std::cout << "\n";
    
    res = f1 - f2;
    f1.print();
    std::cout << " - ";
    f2.print();
    std::cout << " = ";
    res.print();
    std::cout << "\n";
    
    res = f1 * f2;
    f1.print();
    std::cout << " * ";
    f2.print();
    std::cout << " = ";
    res.print();
    std::cout << "\n";
    
    res = f1 / f2;
    f1.print();
    std::cout << " / ";
    f2.print();
    std::cout << " = ";
    res.print();
    std::cout << "\n";
    return 0;
}