c++ - C++字符串流

Question

我只是在学习如何在C++中使用流，我有一个问题。
我以为每个流都具有true或false的状态。我想从下面的字符串和1中输入每个单词，直到出现一个单词，但出现错误:

cannot convert 'std::istringstream {aka std::__cxx11::basic_istringstream<char>}' to 'bool' in initialization
bool canReadMore = textIn;

应该是这样的:

antilope  1  ant  1  antagonist  1  antidepressant  1

What am I doing wrong?

int main() {
    
    std:: string text = "antilope ant antagonist antidepressant";
    std:: istringstream textIn(text);
    
    for(int i = 0; i < 5; i++ ){
        std:: string s;
        textIn >> s;
    
        bool canReadMore = textIn;
        std::cout << s << std:: endl;
        std::cout << canReadMore << std:: endl;
    
    }
    return 0;
    
}
``1

Answer 1

从C++ 11开始， std::istringstream operator bool is explicit。这意味着您必须自己明确地进行 Actor 表转换:

#include <iostream>
#include <sstream>
#include <string>

int main() {
  std::string        text = "antilope ant antagonist antidepressant";
  std::istringstream textIn(text);

  for (int i = 0; i < 5; i++) {
    std::string s;
    textIn >> s;

    bool canReadMore = bool(textIn);
    std::cout << s << std::endl;
    std::cout << canReadMore << std::endl;
  }
  return 0;
}

输出:

./a.out 
antilope
1
ant
1
antagonist
1
antidepressant
1

0

现在，如果在 bool(boolean) 上下文中使用 std::stringstream，转换将是自动的。这是惯用法:

#include <iostream>
#include <sstream>
#include <string>

int main() {
  std::string        text = "antilope ant antagonist antidepressant";
  std::istringstream textIn(text);

  std::string s;
  while (textIn >> s) {
    std::cout << s << "\n";
  }
}

输出:

antilope
ant
antagonist
antidepressant