请解释这段代码

ueaque 发布于 2019-03-09 c++ 最后更新 2019-03-09 14:32 3 浏览

所以我一直试图在C++中分割一个字符串并将内容转储到一个向量中。我发现问题的答案,所以我复制了解决方案,并开始玩弄它来了解它,但它似乎仍然很神秘。我有以下代码片段,它是我制作和复制材料的混合物。我已经评论了我理解其目的的每一行。有人可以填写剩下的评论(基本解释他们的工作)。我想完全理解这是如何解决的。

ifstream inputfile; //declare file
inputfile.open("inputfile.txt"); //open file for input
string m; //declare string
getline(inputfile, m); //take first line from file and insert into string
std::stringstream ss(m);
std::istream_iterator<std::string> begin(ss);
std::istream_iterator<std::string> end;
std::vector<std::string> vstrings(begin, end);
std::copy(vstrings.begin(), vstrings.end(), std::ostream_iterator<std::string>(std::cout, "\n"));
while(true) //delay the cmd applet from closing
{
}
已邀请:

prem

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免责声明:真正的代码永远不应该包含我即将使用的注释。 (它也不应该是如此划线的神秘。) 我添加了一个函数体和必要的标题。

#include <iostream>
#include <string>
#include <sstream>
#include <fstream>
int main()
{
   // Construct a file stream object
   ifstream inputfile;
// Open a file
   inputfile.open("inputfile.txt");
// Construct a string object
   string m;
// Read first line of file into the string
   getline(inputfile, m);
// Copy the string into a stringstream so that we can
   // make use of iostreams' formatting abilities
   std::stringstream ss(m);
// Construct an iterator pair. One is set to the start
   // of the stringstream; the other is "singular", i.e.
   // default-constructed, and isn't set anywhere. This
   // is sort of equivalent to the "null character" you
   // look for in C-style strings
   std::istream_iterator<std::string> begin(ss);
   std::istream_iterator<std::string> end;
// Construct a vector by iterating through the text
   // in the stringstream; by default, this extracts space-
   // delimited tokens one at a time. The result is a vector
   // of single words
   std::vector<std::string> vstrings(begin, end);
// Again using iterators (albeit un-named ones, obtained
   // with .begin() and .end()), stream the contents of the
   // vector to STDOUT. Equivalent to looping through `vstrings`
   // and doing `std::cout << *it << "\n"` for each one
   std::copy(
      vstrings.begin(),
      vstrings.end(),
      std::ostream_iterator<std::string>(std::cout, "\n")
   );
// Blocks the application until it is forcibly terminated.
   // Used because Windows, by default, under some circumstances,
   // will close your terminal after the process ends, before you 
   // can read its output. However: THIS IS NOT YOUR PROGRAM'S
   // JOB! Configure your terminal instead.
   while (true) {}
}
可以这么说,这不是打印到控制台,换行符分隔的最佳方式,每个令牌都可以在磁盘上的文本文件的第一行找到。请不要从互联网上逐字复制代码并期望红海分开。