setw

为数据流中的下一个元素指定显示字符的宽度。

T6 setw( 
   streamsize _Wide 
);

参数

• _Wide
  显示字段的宽度。

返回值

当从数据流中提取或插入时控制器会返回一个对象 str, 调用 str.宽度(_宽), 然后返回 str.

备注

setw 仅设置数据流中的下一个元素，且必须是在你想指定的每个特定宽度的元素之前插入。

示例

// iomanip_setw.cpp 
// compile with: /EHsc
// Defines the entry point for the console application.
//
// Sample use of the following manipulators:
//   resetiosflags
//   setiosflags
//   setbase
//   setfill
//   setprecision
//   setw

#include <iostream>
#include <iomanip>

using namespace std;

const double   d1 = 1.23456789;
const double   d2 = 12.3456789;
const double   d3 = 123.456789;
const double   d4 = 1234.56789;
const double   d5 = 12345.6789;
const long      l1 = 16;
const long      l2 = 256;
const long      l3 = 1024;
const long      l4 = 4096;
const long      l5 = 65536;
int         base = 10;

void DisplayDefault( )
{
   cout << endl << "default display" << endl;
   cout << "d1 = " << d1 << endl;
   cout << "d2 = " << d2 << endl;
   cout << "d3 = " << d3 << endl;
   cout << "d4 = " << d4 << endl;
   cout << "d5 = " << d5 << endl;
}

void DisplayWidth( int n )
{
   cout << endl << "fixed width display set to " << n << ".\n";
   cout << "d1 = " << setw(n) << d1 << endl;
   cout << "d2 = " << setw(n) << d2 << endl;
   cout << "d3 = " << setw(n) << d3 << endl;
   cout << "d4 = " << setw(n) << d4 << endl;
   cout << "d5 = " << setw(n) << d5 << endl;
}

void DisplayLongs( )
{
   cout << setbase(10);
   cout << endl << "setbase(" << base << ")" << endl;
   cout << setbase(base);
   cout << "l1 = " << l1 << endl;
   cout << "l2 = " << l2 << endl;
   cout << "l3 = " << l3 << endl;
   cout << "l4 = " << l4 << endl;
   cout << "l5 = " << l5 << endl;
}

int main( int argc, char* argv[] )
{
   DisplayDefault( );

   cout << endl << "setprecision(" << 3 << ")" << setprecision(3);
   DisplayDefault( );

   cout << endl << "setprecision(" << 12 << ")" << setprecision(12);
   DisplayDefault( );

   cout << setiosflags(ios_base::scientific);
   cout << endl << "setiosflags(" << ios_base::scientific << ")";
   DisplayDefault( );

   cout << resetiosflags(ios_base::scientific);
   cout << endl << "resetiosflags(" << ios_base::scientific << ")";
   DisplayDefault( );

   cout << endl << "setfill('" << 'S' << "')" << setfill('S');
   DisplayWidth(15);
   DisplayDefault( );

   cout << endl << "setfill('" << ' ' << "')" << setfill(' ');
   DisplayWidth(15);
   DisplayDefault( );

   cout << endl << "setprecision(" << 8 << ")" << setprecision(8);
   DisplayWidth(10);
   DisplayDefault( );

   base = 16;
   DisplayLongs( );

   base = 8;
   DisplayLongs( );

   base = 10;
   DisplayLongs( );

   return   0;
}

要求

页眉: <iomanip>

命名空间: std

请参见

参考

iostream 编程

iostreams 约定