格式化输出流，ios :: left和ios :: right [英] Formatting the output stream, ios::left and ios::right

问题描述

我有这个代码：

  cout< std :: setiosflags（std :: ios :: right）; 
 cout<< setw（3）<< 1<< setw（3）<< 2<< '\\\
'; //输出两个值
 
 cout<< std :: setiosflags（std :: ios :: left）; 
 cout<< setw（3）<< 1<< setw（3）<< 2<< '\\\
'; //输出两个值
  

但输出不像我预期的。而不是：

  1 2 
 1 2 
  

这会出来：

  1 2 
 1 2 
  

问题是什么？我设置'std :: ios :: left'但是没有区别？

解决方案

  #include< iostream> 
 #include< iomanip> 
 int main（）{
 std :: cout<< std :: resetiosflags（std :: ios :: adjustfield）; 
 std :: cout<< std :: setiosflags（std :: ios :: right）; 
 std :: cout<< std :: setw（3）<< 1<< std :: setw（3）<< 2<< '\\\
'; 
 
 std :: cout<< std :: resetiosflags（std :: ios :: adjustfield）; 
 std :: cout<< std :: setiosflags（std :: ios :: left）; 
 std :: cout<< std :: setw（3）<< 1<< std :: setw（3）<< 2<< '\\\
'; 
} 
  

I have this code:

cout << std::setiosflags(std::ios::right);
cout << setw(3) << 1 << setw(3) << 2 << '\n'; // Output two values

cout << std::setiosflags(std::ios::left);
cout << setw(3) << 1 << setw(3) << 2 << '\n'; // Output two values

but the output doesnt come like i expected. instead of:

  1  2
1  2  

this comes out:

  1  2
  1  2

What is the problem? I set 'std::ios::left' but it makes no difference?

解决方案

You have to clear the previous value in adjustfield before you can set a new one.

Try this:

#include <iostream>
#include <iomanip>
int main () {
  std::cout << std::resetiosflags(std::ios::adjustfield);
  std::cout << std::setiosflags(std::ios::right);
  std::cout << std::setw(3) << 1 << std::setw(3) << 2 << '\n';

  std::cout << std::resetiosflags(std::ios::adjustfield);
  std::cout << std::setiosflags(std::ios::left);
  std::cout << std::setw(3) << 1 << std::setw(3) << 2 << '\n';
}

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