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

我正在尝试编写一个代码，通过使用 eof() 从文件中读取来计算注册费。 但是，当我尝试编译时，我得到一个错误，即 C2677，这意味着二进制“-”没有找到全局运算符。 我已经研究过如何解决它，但我不明白。 这是我的代码：

#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

问题是这一行：

age = (2020 - year);

age是一个int 。 2020是一个整数。 您声明为字符串的year 。

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

这正是错误告诉你的。 没有operator-接受int和string 。