运算符重载：用二进制“-”减法没有找到采用_____类型的全局运算符（或没有可接受的转换）

Question

I'm trying to write a code that calculates the registration fee by reading from a file using eof(). However, when I try to compile I get one error, which is C2677, which means that binary "-" no global operator found. I've looked into how to fix it, but I'm not understanding. Here is my code:

#include <iostream>
#include <string>
#include <fstream>
using namespace std;

int main()
{
    ifstream inFile;
    ofstream outFile;

    string VIN, make, model, type, year;
    string truck = "TRUCK";
    double basefee, weight;
    double tax = 0.065;
    double highwayfund = 2.0;
    int age;
    double discount;

    inFile.open("VehicleInput.txt");
    outFile.open("VehicleOutput.txt");

    while (!inFile.eof())
    {
        inFile >> VIN >> make >> model >> type >> year;
        inFile >> weight;
        age = (2020 - year);
        weight = 12000;
        discount = (age * 0.1);

        if (age >= 7)
        {
            discount = 0.7;
        }

        if ((type == "CAR") || (type == "SUV"))
        {
            basefee = (100 - ((100.0 * tax) - (100 * discount)) + highwayfund);
        }
        if (type == "BUS")
        {
            basefee = (200 - ((200.0 * tax) - (200 * discount)) + highwayfund);
        }
        if (type == "TRUCK")
        {
            basefee = (500 - ((500.0 * (0.22 + tax)) - (500 * discount)) + highwayfund);
        }


        outFile << " " << VIN << " " << make << " " << model << " " << year;
        if (weight > 12000) outFile << weight;
        outFile << "$ " << basefee << endl;


    }
    return 0;
}

Answer 1

The problem is this line:

age = (2020 - year);

age is an int . 2020 is an int. year you declared as a string.

string VIN, make, model, type, year;
int age;

That's exactly what the error is telling you. There is no operator- which takes an int and string .