运算符重载类型转换：直角坐标到C ++

Question

I need to typecast the cartesian coordinates to polar one. The error which i am getting while typecasting to polar is "Expected type specifier before Polar" . Please help me out. I read the other posts and found out that I need to specify the class type. I tried it specifying as "Cartesian". How and what i should specify?? Thanx in advance. I am getting the error in the section which is commented out

#include<iostream>
#include<cstdio>
#include<cmath>
using namespace std;
class Cartesian
{
    double x,y;
public:
    Cartesian()
    {
        x=0.0;y=0.0;
    }
    Cartesian(int x,int y)
    {
        this->x=x;
        this->y=y;
    }
    Cartesian(const Cartesian& p)
    {
        x=p.x;
        y=p.y;
    }
    int getX()
    {
        return x;
    }
    int getY()
    {
        return y;
    }
    double operator-(Cartesian b)
    {
        double dist;
        dist=sqrt((x-b.x)*(x-b.x)+(y-b.y)*(y-b.y));
        return dist;
    }
    /*operator Polar()
    {
        Polar temp;
        temp.r=sqrt((x*x)+(y*y));
        temp.theta=atan(y/x);
        return temp;
    }*/




};


class Polar
{
    double r,theta;
public:
    Polar()
    {
        r=0.0;theta=0.0;
    }
    Polar(int r,int theta)
    {
            this->r=r;
            this->theta=theta;
    }
    Polar(const Polar& p)
    {
        r=p.r;
        theta=p.theta;

    }
     int getR()
    {
        return r;
    }
    int getTheta()
    {
        return theta;
    }
    double operator-(Polar b)
    {
        double dist;
        dist=sqrt(r*r+(b.r)*(b.r)+2*(r)*(b.r)*cos(theta-b.theta));
        return dist;

    }

};

int operator==(Cartesian a,Cartesian b)
{
    int t1,t2;
    t1=a.getX();
    t2=b.getX();
    if(t1==t2)
    {
        t1=a.getY();
        t2=b.getY();
        if(t1==t2)
            return 1;
    }
    return 0;
}

int operator==(Polar a,Polar b)
{
    int t1,t2;
    t1=a.getR();
    t2=b.getR();
    if(t1==t2)
    {
        t1=a.getTheta();
        t2=b.getTheta();
        if(t1==t2)
            return 1;
    }
    return 0;
}

int operator==(Cartesian a,Polar b)
{

    int t1,t2,t3,t4;
    t1=a.getX();
    t2=a.getY();
    t3=b.getR();
    t4=b.getTheta();
    if((sqrt(t1*t1+t2*t2)==t3)&&(atan(t2/t1)==t4))
        return 1;
    else
        return 0;
}






int main()
{
    double temp1,temp2,temp3,temp4,distance;
    cout<<"Enter the x and y coordinates of the first point\n";
    cin>>temp1>>temp2;
    Cartesian a1(temp1,temp2);
    cout<<"Enter the x and y coordinates of the second point\n";
    cin>>temp3>>temp4;
    Cartesian b1(temp3,temp4);
    distance=a1-b1;
    cout<<distance<<"\n";
    cout<<"Enter the r and theta coordinates of the first point\n";
    cin>>temp1>>temp2;
    Polar a2(temp1,temp2);
    cout<<"Enter the r and theta coordinates of the second point\n";
    cin>>temp3>>temp4;
    Polar b2(temp3,temp4);
    distance=a2-b2;
    cout<<distance<<"\n";
    if(a1==a2)
        cout<<"True";





    return 0;
}

Answer 1

Class Polar is not defined at the point where you define operator Polar , so you need to forward declare it and implement it after the definition of Polar. Also, you are accessing Polar's private members, so you need to declare Cartesian as a friend of Polar:

class Polar; // forward declaration

class Cartesian {
    //...

    operator Polar(); // only the declaration
};

class Polar {
    friend class Cartesian; // so that Cartesian sees private members

    //...
};

// implementation of operator Polar()
Cartesian::operator Polar() {
    Polar temp;
    temp.r=sqrt((x*x)+(y*y));
    temp.theta=atan(y/x);
    return temp;
}