Question

#include <iostream>
#include <string>

using namespace std;

int main ()
{
    do
    {
    string name, answer;
    cout << "Welcome to the prime number checker! Please enter your name: ";
    getline (cin, name);
    int a;
    cout << "\nHello " << name;
    cout << "\nPlease enter an integer: ";
    cin >> a;
    cin.sync();
    if (a == 2)
    {
        cout << "\nThis is a prime number" << endl;
    }
    else
    {
        for (int b = 2; b < a; b++)
        {
            if (a % b == 0)
            {
                cout << "This number is not prime number" << endl;
                break;
            }
            else
            {
                cout << "This number is a prime number." << endl;
                break;
            }
        }
    }
    cout << "Do you want to do this again (Yes or No)?";
    getline (cin, answer);
    }
    while (answer == "yes" || answer == "YES" || answer == "Yes"); //Not declared in this scope
    return 0;
}

Answer 1

您在DOM块中声明了answer。但是，然后尝试在该范围块之外引用do。

在answer的顶部而不是answer块中声明main。

Answer 2

您需要在循环外移动answer的声明：

string answer;
do {
   string name;
   ...
} while (answer == "yes" || answer == "YES" || answer == "Yes");

如果在循环中声明它，则在评估while子句时它不再存在。

Answer 3

正如其他人所说，“回答”变量只存在于循环内部 - 它无法从外部访问。

另一个建议：不是检查每个可能的大写排列，而是将整个字符串强制转换为小写。（你实际上错过了几个 - 总共有6个因为每个职位可能有两个可能的值之一。例如，大概应该像“YeS”这样的东西仍然被接受为“是”）。

它是什么意思＆＃34;错误：未在此范围内声明？＆＃34;

3 个答案: