我正在做一个关于运算符重载的教程，在编写本书中的代码时，我在下一节中遇到了错误：
std::ostream &operator<<(std::ostream &outst, const AC_current &c)
{
outst << std::setiosflags(std::ios::fixed)<<std::setprecision(2);
outst << "(" << std::setw(6) << c.mag; //----->'mag' is a private member of 'AC_current'
outst << ", " << std::setw(6) << c.phase<<(char)248<< ") A"; //--->'phase' is a private member of 'AC_current'
return outst;
}
我将它定义为朋友功能，但它不起作用。我做错了什么？
P.S.这是完整的代码。
#include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;
const double Deg2Rad = 2*M_PI/360;
const double Rad2Deg = 360/(2*M_PI);
class AC_current
{
private:
double mag, phase;
double real, imag;
void setRect();
void setPolar();
public:
AC_current(double m=0, double p=0)
{
mag = m; phase = p; setRect();
}
AC_current operator-(const AC_current & c) const;
AC_current operator+(const AC_current & c) const;
AC_current operator*(double) const;
int getCoord();
friend std::istream &operator >> (std::istream &inst, AC_current &c);
friend std::ostream &operator << (std::ostream &outst, AC_current &c);
};
int AC_current::getCoord()
{
int selection;
do
{
std::cout << "\n Select: \n\t1) AC current in polar coordinates ";
std::cout << "\n\t2) AC current in rectangular coordinates ";
std::cout << "\n\t Enter selection: ";
std::cin >> selection;
} while ((selection!=1)&&(selection!=2));
return selection;
}
void AC_current::setRect()
{
real= mag*cos(phase*Deg2Rad);
imag=mag*sin(phase*Deg2Rad);
}
void AC_current::setPolar()
{
mag=sqrt(real*real+imag*imag);
if (!((real==0)&&(imag==0)))
{
phase=atan(imag/real)*Rad2Deg;
}
else
phase=0;
}
AC_current AC_current::operator-(const AC_current &c) const
{
AC_current temp;
double treal, timag;
treal = mag*cos(phase*Deg2Rad)-c.mag*cos(c.phase*Deg2Rad);
timag = mag*sin(phase*Deg2Rad)-c.mag*sin(c.phase*Deg2Rad);
temp.mag = sqrt(treal*treal+timag*timag);
if (!((treal==0)&&(timag==0)))
{
temp.phase = atan(timag/treal)*Rad2Deg;
}else temp.phase=0;
return temp;
}
AC_current AC_current::operator+(const AC_current &c) const
{
AC_current temp;
double treal, timag;
treal = mag*cos(phase*Deg2Rad)+c.mag*cos(c.phase*Deg2Rad);
timag = mag*sin(phase*Deg2Rad)+c.mag*sin(c.phase*Deg2Rad);
temp.mag = sqrt(treal*treal+timag*timag);
if (!((treal==0)&&(timag==0)))
{
temp.phase = atan(timag/treal)*Rad2Deg;
}else temp.phase=0;
return temp;
}
AC_current AC_current::operator*(double r) const
{
AC_current temp;
temp.mag = mag*r;
temp.phase = phase;
temp.setRect();
return temp;
}
std::istream &operator>>(std::istream &inst, AC_current &c)
{
int choice=c.getCoord();
if (choice==1)
{
std::cout << "\nEnter magnitude: ";
inst >> c.mag;
std::cout << "\nEnter phase shift: ";
inst >> c.phase;
c.setRect();
}
else if(choice == 2)
{
std::cout << "\nEnter real part: ";
inst >> c.real;
std::cout << "\nEnter imaginary part: ";
inst >> c.imag;
c.setPolar();
}
return inst;
}
std::ostream &operator<<(std::ostream &outst, const AC_current &c)
{
outst << std::setiosflags(std::ios::fixed)<<std::setprecision(2);
outst << "(" << std::setw(6) << c.mag;
outst << ", " << std::setw(6) << c.phase<<(char)248<< ") A";
return outst;
}
int menu()
{
int selection;
do
{
std::cout << "\n\n\tSelect operation:" << std::endl;
std::cout << "\n\n 1)Add currents" << std::endl;
std::cout << "\n\n 2)Substract currents" << std::endl;
std::cout << "\n\n 3)Multiply current by resistance" << std::endl;
std::cout << "\n\n 4)Exit" << std::endl;
std::cout << "\n\n Enter selection (1-4) => ";
std::cin >> selection ;
} while (selection<1||selection>4);
return selection;
}
int main ()
{
AC_current c1,c2;
int operation;
std::cin >> c1 >> c2;
while (operation !=4) {
operation = menu();
switch (operation) {
case 1:
std::cout << "\n\tc1+c2 = " << (c1+c2);
break;
case 2:
std::cout << "\n\tc1-c2 = " << (c1-c2);
break;
case 3:
double r;
std::cout <<"\nEnter resistance : ";
std::cin >> r;
std::cout << "\n\tc1*R = " << (c1*r);
break;
case 4:
break;
}
}
return 0;
}