虽然循环没有终止？

Question

我想知道为什么这个while循环不允许我的程序终止？

据我所知(虽然我可能错了)条件while (cin >> line)检查我的输入流是否为String然后运行我的循环,直到在输入中找不到其他字符串.然而,在测试我的代码后,我得到了正确的输出,但我的循环永远不会终止任何想法为什么？

#include <cstdlib>
#include <iostream>
#include <cctype>

using namespace std;

int main() {

string roman_digits[] = {"", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"};
string roman_tens  [] = {"", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"};
string roman_hundreds [] = {"", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"};
string roman_thousands [] = {"", "M","MM", "MMM"};
string line;
char c;


cout << "Type in a Roman numeral: ";

// Loops through inputted Roman Numerals.    
while (cin >> line){
    int i = 0;

    // Loops through a Roman numeral and changes it to uppercase.
    while(line[i]){
        c = line[i];
        c = (toupper(c));
        line[i] = c;
        i++;
    }


// Loops through checking roman numeral with the thousands array and if there is a match prints out the equivalent arabic number.
    for (int i = 0; i < 10; i++){
       if (roman_thousands[i] == line){
           cout << "The Arabic equivalent of " 
                << line <<" is: " << i << 0 << 0 << 0 << endl;
        }
    }
 // Loops through checking roman numeral with the hundreds array and if there is a match prints out the equivalent arabic number.
    for (int i = 0; i < 10; i++){
        if (roman_hundreds[i] == line){
            cout << "The Arabic equivalent of " << line << " is: " << i << 0 << 0 << endl;
        }
    }
     // Loops through checking roman numeral with the tens array and if there is a match prints out the equivalent arabic number.
    for (int i = 0; i < 10; i++){
        if (roman_tens[i] == line){
            cout << "The Arabic equivalent of " << line << " is: " << i << 0 << endl;
        }
    }
     // Loops through checking roman numeral with the digits array and if there is a match prints out the equivalent arabic number.
    for (int i = 0; i < 10; i++){
        if (roman_digits[i] == line){
            cout << "The Arabic equivalent of " << line << " is: " << i << endl;
        }

    }
 }


  return 0;


}

Answer 1

程序总是等待您添加更多输入,因此它不会终止.有几种方法可以解决这个问题:

• 让程序查找特定的关键字,如"退出"或"退出",甚至只是一个空格,然后输入要终止的关键字.这很简单,但不是很优雅.
• 发送"流结束"指示符作为输入中的唯一内容.在linux和unix中,您只需键入Ctrl-D,这表示您已关闭标准输入.正如一些评论所说,Ctrl-Z是Windows的文件说明符的结尾,如果您正在使用它.