在一个while循环中多次询问用户输入

Question

我目前正在编写一个程序，将普通文本翻译成鲸语（如果你想知道鲸语是什么，它是用 u's 和 e's 加倍的辅音撕裂的语句）

我成功编写了程序。但我希望它再次重复并经历相同的过程，直到我们手动退出它。

为此，我使用了一个 while 循环并将 exit 作为变量。但它没有像第二次那样按预期工作，它没有要求输入，而是显示提示文本并跳到退出/不退出行。 你能告诉我我的程序有什么问题吗？这是我的代码（你可以尝试自己编译执行）：

#include <iostream>
#include <string>
#include <vector>

int main(){
  bool exit = false;
//Open
std::cout<<"==========\n";
std::cout<<"WHALE TALK\n";
std::cout<<"==========\n";
std::cout<<"\n";
//main loop

while (!exit){

//Variables
std::vector<char> whaletalk;
//input
std::string input;
std::cout<<"Type the text you want to translate to whale language: ";
getline(std::cin,input);
std::cout<<"\n\nWhale talk: ";

//vowels
std::vector <char> vowels = {'a','e','i','o','u'};

//sorter
//iterating through string
for (int i = 0; i < input.size(); i++){
  //iterating through vowels
  for (int j = 0; j < vowels.size(); j++){
      //case of vowels
      if(input[i] == vowels[j]){
          //case of u and e
          if ((input[i] == 'u') or (input[i] == 'e')){
              whaletalk.push_back(input[i]);
              whaletalk.push_back(input[i]);
          }
          //case of vowels other than u and e
          else {whaletalk.push_back(input[i]);}
      }
  }
}
//Output
for (int k = 0; k < whaletalk.size(); k++ ){

  std::cout<<whaletalk[k];
}
std::cout<<"\n";
// exit/no exit
std::string response;
std::cout<<'\n';
std::cout<<"Do you have more to translate?(yes/no)\n\nYour response: ";
std::cin>>response;
if (response == "NO" or response == "no" or response == "No"){
  exit = true;
}




}
}

Here is an image of the bug

Answer 1

当您使用>> 运算符读取字符串时，它只会读取下一个单词（最多一个空格字符），并将其他所有内容留在输入流中，但std::cin 仍会阻塞直到换行（输入被按下）。

std::string response;
std::cout << '\n';
std::cout << "Do you have more to translate?(yes/no)\n\nYour response: ";
std::cin >> response;
if (response == "NO" or response == "no" or response == "No") {
    exit = true;

如果您只输入一个单词，这将只在缓冲区中留下换行符（如果您确实说“ab”，那么它将留下“b\n”，response 将是“a”，而不是“ab”），所以下一个std::getline 会给你剩下的，在这种情况下是一个空行。

int main()
{
    std::string str;
    std::cout << "Enter word: ";
    std::cin >> str;
    std::cout << "Entered '" << str << "'" << std::endl;

    std::cout << "Enter line: ";
    std::getline(std::cin, str);
    std::cout << "Entered '" << str << "'" << std::endl;
}

输入单词：a
输入'a'
输入行：输入''

或者如果你有一个空格字符：

输入单词：aa bb
输入'aa'
输入行：输入'bb'

您可以在仅读取字符串响应时始终使用std::getline，以避免意外遗漏任何内容（例如“bb”）。

 std::string response;
 std::cout << '\n';
 std::cout << "Do you have more to translate?(yes/no)\n\nYour response: ";
 std::getline(std::cin, response);
 if (response == "NO" or response == "no" or response == "No") {
     exit = true;

或在任何其他>> 操作之后获取“剩余”内容并继续下一行。

另一种可能性是使用std::istream.ignore() 忽略剩余输入，直到最大长度和分隔符：

 std::string response;
 std::cout << '\n';
 std::cout << "Do you have more to translate?(yes/no)\n\nYour response: ";
 std::cin >> response;
 std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
 if (response == "NO" or response == "no" or response == "No") {
     exit = true;

在这种情况下，std::numeric_limits<std::streamsize>::max() 表示任意数量，直到下一行 \n。如果用户输入说“no abc”，那么“abc”就会丢失。

Answer 2

1. 您应该使用这些函数来清除输入并忽略除换行符之外的所有字符：

std::cin.clear();
std::cin.ignore(32767, '\n');

在这个函数下面：

std::cin >> ...;

1. 这是响应的循环检查：

      while (true) {
            if (response == "NO" or response == "no" or response == "No") {
                exit = true;
                break;
            }
            else if (response == "YES" or response == "yes" or response == "Yes")
            {
                break;
            }
            else
            {
                std::cout << "\nPlease only input yes or no: ";
                std::cin >> response;
                // Clear input
                std::cin.clear();
                std::cin.ignore(32767, '\n');
            }
        }

1. 完整代码：

#include <iostream>
#include <string>
#include <vector>

int main() {
    bool exit = false;
    //Open
    std::cout << "==========\n";
    std::cout << "WHALE TALK\n";
    std::cout << "==========\n";
    std::cout << "\n";
    //main loop

    while (!exit) {

        //Variables
        std::vector<char> whaletalk;
        std::cout << "Type the text you want to translate to whale language: ";
        //input
        std::string input;
        std::getline(std::cin, input);
        std::cout << "\n\nWhale talk: ";

        //vowels
        std::vector <char> vowels = { 'a','e','i','o','u' };

        //sorter
        //iterating through string
        for (int i = 0; i < input.size(); i++) {
            //iterating through vowels
            for (int j = 0; j < vowels.size(); j++) {
                //case of vowels
                if (input[i] == vowels[j]) {
                    //case of u and e
                    if ((input[i] == 'u') or (input[i] == 'e')) {
                        whaletalk.push_back(input[i]);
                        whaletalk.push_back(input[i]);
                    }
                    //case of vowels other than u and e
                    else { whaletalk.push_back(input[i]); }
                }
            }
        }
        //Output
        for (int k = 0; k < whaletalk.size(); k++) {

            std::cout << whaletalk[k];
        }
        std::cout << "\n";
        // exit/no exit
        std::string response;
        std::cout << '\n';
        std::cout << "Do you have more to translate?(yes/no)\n\nYour response: ";
        std::cin >> response;
        // Clear input
        std::cin.clear();
        std::cin.ignore(32767, '\n');

        while (true) {
            if (response == "NO" or response == "no" or response == "No") {
                exit = true;
                break;
            }
            else if (response == "YES" or response == "yes" or response == "Yes")
            {
                break;
            }
            else
            {
                std::cout << "\nPlease only input yes or no: ";
                std::cin >> response;
                // Clear input
                std::cin.clear();
                std::cin.ignore(32767, '\n');
            }
        }
    }
    return 0;
}