在EOF之后重用std :: cin [英] Reusing std::cin after EOF

问题描述

下面的代码用于在 std :: vector 中存储一组单词，并计算用户给定的特定单词在向量中出现的次数

The code below is for storing a group of words in a std::vector and to count how many times a particular word given by the user appears in the vector by comparing it to all the words stored in the vector.

控制台不会在第二个 std :: cin>>>提示输入;

The console does not prompt me for input at the second std::cin >> in the program below.

#include <iostream>
#include <ios>
#include <iomanip>
#include <vector>
#include <algorithm>
using namespace std;

int main(int argc, const char * argv[])
{
   cout<<"enter your words followed ny EOF"<<endl;
   vector<string> words;
   string x;
   typedef vector<string>::size_type vec_size;
   vec_size size;
   while (cin>>x) 
   {
     words.push_back(x);
   }
   size=words.size();
   cin.clear();

   //now compare
   cout<<"enter your word:"<<endl;
   string my_word;
   int count=0;

   cin>>my_word;              //didn't get any prompt in the console for this 'cin' 
   for (vec_size i=0; i<size; ++i) 
   {
      my_word==words[i]?(++count):(count=count);
   }
   cout<<"Your word appeared "<<count<<" times"<<endl;
   return 0;

}

我得到的最终输出是你的单词出现0次。
代码的问题是什么。任何帮助将是巨大的。

The final output I get is "Your word appeared 0 times". What is the problem with the code. Any help would be great.

推荐答案

程序读取单词列表直到文件结束。因此，在终端上，您可以键入EOF字符（在Linux上为 Ctrl-D ，在Windows上为 Ctrl-Z Return 那么？

The program reads the word list until end of file. So, at a terminal, you can type the EOF character (Ctrl-D on Linux, Ctrl-Z Return on Windows), but what then?

我认为在重置流之后，终端将继续读取。但是如果程序正在从磁盘文件，管道等输入，没有希望。文件结束是永远的。

I think after resetting the stream, a terminal will continue to read. But if the program is taking input from a disk file, pipe, etc., there is no hope. End-of-file is forever.

而是使用某种哨兵，或者用计数前缀。这样，第一个循环可以运行，直到列表的逻辑结束。然后它可以读取用于汇总逻辑的词。

Instead, use some sort of sentinel, or prefix it by a count. That way the first loop can run until the logical end of the list. And then it can read the word intended for the summary logic.

while (cin>>x  &&  x != '*')   // The word "*" ends the list of words
   {
     words.push_back(x);
   }
   size=words.size();

   //now compare
   cout<<"enter your word:"<<endl;

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