c++ operator重载的例子

c++ operator重载的例子

#include <iostream>

using namespace std;

class A

{

public:

    A(double _data = 0.0):data(_data){}

    A& operator = (const A& rhs)

    {

        data = rhs.data;

        return *this;

    }

      

    friend A operator + (const A& lhs,const A& rhs);

    friend A operator - (const A& lhs,const A& rhs);

    friend A operator * (const A& lhs,const A& rhs);

    friend A operator + (const A& lhs,double rhs);

    friend A operator + (double lhs,const A& rhs);

    friend A operator * (const A& lhs,double rhs);

    friend A operator * (double lhs,const A& rhs);

    friend A operator - (const A& lhs,double rhs);

    friend A operator - (double lhs,const A& rhs);

      

      

    friend ostream& operator << (ostream& fout,A& a);

//  A& operator += (const A& rhs);

//  A& operator -= (const A& rhs);

//  A& operator *= (const A& rhs);  

private:

    double data;

};

  

A operator + (const A& lhs,const A& rhs)

{

    A res(0);

    res.data = lhs.data + rhs.data;

    return res;

}

A operator - (const A& lhs,const A& rhs)

{

    A res(0);

    res.data = lhs.data - rhs.data;

    return res;

}

A operator * (const A& lhs,const A& rhs)

{

    A res(0);

    res.data = lhs.data * rhs.data;

    return res;

}

 A operator + (const A& lhs,double rhs)

 {

    A res(0);

    res.data = lhs.data + rhs;

    return res;

}

  

A operator + (double lhs,const A& rhs)

{

    A res(0);

    res.data = lhs + rhs.data;

    return res;

}

A operator * (const A& lhs,double rhs)

{

    A res(0);

    res.data = lhs.data * rhs;

    return res;

}

A operator * (double lhs,const A& rhs)

{

    A res(0);

    res.data = lhs * rhs.data;

    return res;

}

A operator - (const A& lhs,double rhs)

{

    A res(0);

    res.data = lhs.data - rhs;

    return res; 

}

A operator - (double lhs,const A& rhs)

{

    A res(0);

    res.data = lhs - rhs.data;

    return res; 

}

      

ostream& operator << (ostream& fout,A& a)

{

    fout << a.data ;

    return fout;

}

int main(int argc, char* argv[])

{

    A a(2.3);

    A b(1.2);

    A d(3.4);

    A c;

    c = a + b + d;

    c=a+b;

    c=a+1.0;

    c=a-b;

    c=a-1.0;

    c=a*b;

    c=a*1.0;

    cout << c << endl;

      

    c=1.0+2.0*a*a-3.0*a*b;

    cout << c << endl;

    return 0;

}