c++ - C++编程错误|未声明的标识符

Question

因此，我尝试编写一个简单的程序，并在控制台中不断收到'未声明的标识符错误'，其中包含我的姓名，作者，价格，isbn，数量，第一个结果和第二个结果。抱歉，如果有人问过这种问题，但我无法解决。

这是我的程序:

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

int main()

{
    string name, author,
        double isbn,
        float price,
        int quantity,
        float firstresult,
        float secondresult,
        const float tax (0.07);

    cout << "What is the name of the book?";
    cin >> name;
    cout << "What is the authors name?";
    cin >> author;
    cout << "What is the ISBN number?";
    cin >> isbn;
    cout << "What is the price?";
    cin >> price;
    cout << "How many books did you purchase?";
    cin >> quantity;

    firstresult = price*tax;
    secondresult = price + firstresult;

    if (quantity > 5) {
        secondresult += (quantity - 5) * 2.00;
    }

    cout << "------------------------" << endl;
    cout << "Invoice of Order:" << endl;
    cout << name << endl;
    cout << author << endl;
    cout << isbn << endl;
    cout << price << endl;
    cout << quantity << endl;
    cout << "Total Cost: " << secondresult << endl;
    cout << "------------------------" << endl;

    return 0;
}

Answer 1

您试图通过用逗号,分隔它们来声明多个不同类型的局部变量，这是错误的。使用单独的语句声明变量，并改用分号;。分号标志着语句的结束:

string name, author; // you are defining multiple variables of the same type which is fine
double isbn;
float price;
int quantity;
float firstresult;
float secondresult;
const float tax (0.07);

这些不是函数参数，在这种情况下，它们将用逗号分隔。话虽如此，当您从标准输入接受字符串时，应该使用std::getline:

std::getline(std::cin, author);