"No viable overloaded '=' " why? - c++

Question

I'm making a project for one of my classes and I'm pretty sure I'm almost done with the project. Basically I have to input 2 people's tickets and I have to find the maximum and minimum price. I need to overload the * and / operators to fix that issue for the project. Also, the friend declaration is a necessity for this project via teacher's instructions.
Now, for the issue. I'm trying to store the proper ticket variable (either t1 or t2) into t3 so I can return that to the main. When I use "=" to set either t1 to t3, it says "no viable overloaded '='". The following is my code:
#include <iostream>
using namespace std;
class ticket
{
public:
ticket();
double input();
double output();
friend ticket operator *(const ticket &t1, const ticket &t2);
friend ticket operator /(const ticket &t1, const ticket &t2);
private:
void cost();
string name;
double miles, price;
int transfers;
};
int main()
{
ticket customer1, customer2, customer3;
//------------------------------------------------
cout << "*** Customer 1 ***" << endl;
customer1.input();
cout << "--- Entered, thank you ---" << endl;
cout << "*** Customer 2 ***" << endl;
customer2.input();
cout << "--- Enter, thank you ---" << endl;
//------------------------------------------------
//------------------------------------------------
cout << "Testing of the * operator: " << endl;
customer3 = customer1 * customer2;
cout << "*** Database printout: ***" << endl;
customer3.output();
cout << endl;
cout << "--- End of Database ---" << endl;
//------------------------------------------------
//------------------------------------------------
cout << "Testing of the / operator:" << endl;
customer3 = customer1 / customer2;
cout << "*** Database printout: ***" << endl;
customer3.output();
cout << endl;
cout << "--- End of Database ---" << endl;
//------------------------------------------------
return 0;
}
ticket operator *(const ticket &t1, const ticket &t2)
{
ticket t3;
if (t1.price > t2.price)
t3 = t1.price;
else
t3 = t2.price;
return t3;
}
ticket operator /(const ticket &t1, const ticket &t2)
{
ticket t3;
if (t1.price < t2.price)
t3 = t1.price;
else
t3 = t2.price;
return t3;
}
ticket::ticket()
{
}
double ticket::input()
{
cout << "Miles? ";
cin >> miles;
cout << endl << "Transers? ";
cin >> transfers;
cout << endl << "Name? ";
cin >> name;
cost();
cout << endl << "Price is: " << price << endl;
return miles;
}
double ticket::output()
{
cout << name << '\t' << miles << "mi \t " << transfers << " transfers \t" << price;
return miles;
}
void ticket::cost()
{
price = (.5 * miles) - (50 * transfers);
}

Answer 1

You don't define an operator= for ticket that takes a double as its argument. As a consequence you can't assign doubles to ticket objects.

Answer 2

This is how I get the same compile error. I have mark one of my getter function as const while I still want to modify class member variable. See the following simple example:
class CPath {
private:
std::string m_extension;
public:
std::string GetExtension() const {
if (m_extension.length()==0) {
m_extension = "txt";
}
return m_extension;
}
}
In this case, we have two solutions:
1) drop const modifier in the function definition;
2) mark the property m_extension as mutable.

Answer 3

you might want to have member function
set_price(const& double price)
so you can change the error code like this,which would be better
if (t1.price > t2.price)
t3.set_price(t1.price);
else
t3.set_price(t2.price);