没有输入任何内容时结束循环 [英] Ending a loop when nothing is entered

问题描述

通常，我编写一个控制循环，如下所示:输入的循环将int写入向量nVec中，直到输入"done"为止.

Usually I write a control loop as follows: Loop that enters writes ints into vector nVec until "done" is entered.

while (cin >> sString){
    if (sString="done")
    { 
        break;
    }
    nVec.push_back(sString);

}

这可以很好地工作，但是如果我希望在用户没有输入任何内容(仅按Enter键)时结束循环，我该怎么做?

this works fine, but how would I go about doing this if I wanted the loop to end once the user entered nothing (just pressed enter)?

推荐答案

您不能不输入任何内容"进行令牌提取.停止循环的唯一方法是让用户发送文件结尾(在Linux上为Ctrl-D).我个人会说这是正确的行为，但是如果您想以空输入结尾，则需要阅读以下行:

You can't "not enter anything" into your token-wise extraction. The only way for your loop to stop is for the user to send end-of-file (Ctrl-D on Linux). I would personally say that this is the correct behaviour, but if you want to end on empty input, you need to read lines:

Sales_item total;

for (std::string line; std::getline(std::cin, line); )
{
     if (line.empty()) { exit_program(); /* or "break" */ }

     std::istringstream iss(line);
     for (Sales_item book; iss >> book; )
     {
          total += book;
          std::cout << "The current total is " << total << std::endl;
     }
}

这样，您可以将每一行标记成可能的多本书.如果您只想每行一本书，请跳过内循环，然后说 std :: istringstream(line)>>书； .

This way, you tokenize each line into possibly multiple books. If you just want one book per line, rip out the inner loop and just say std::istringstream(line) >> book;.

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