c++ cout 格式化输出浮点数、整数及格方法

C语言里可以用printf(),%f来实现浮点数的格式化输出，用cout呢。。。？ 下面的方法是在网上找到的，如果各位有别的办法谢谢留下...

iomanip.h是I/O流控制头文件,就像C里面的格式化输出一样.以下是一些常的:

dec 置基数为10 相当于"%d" hex 置基数为16 相当于"%X" oct 置基数为8 相当于"%o" setfill(c) 设填充字符为c setprecision(n) 设显示小数精度为n位 setw(n) 设域宽为n个字符 setioflags(ios::fixed) 固定的浮点显示 setioflags(ios::scientific) 指数表示 setiosflags(ios::left) 左对齐 setiosflags(ios::right) 右对齐 setiosflags(ios::skipws 忽略前导空白 setiosflags(ios::uppercase) 16进制数大写输出 setiosflags(ios::lowercase) 16进制小写输出 setiosflags(ios::showpoint) 强制显示小数点 setiosflags(ios::showpos) 强制显示符号

#include <iomanip>
use namespace std;
double d=11.23456;
cout<<d<<endl;                                                  //直接输出只能输出6位数，包括整数部分和小数部分
cout<<setprecision(3)<<d<<endl;               //精度为3，输出3位数
cout<<setiosflags(ios::fixed)<<d<<endl;//精度为3，定点输出，输出3位小数
cout<<setiosflags(ios::fixed)<<setprecision(7)<<d<<endl;//位数不够，末尾添0

输出结果：

11.2346 11.2 11.23456 11.2345600

C++格式化输出浮点数

#include <iostream>
using std::cout;
using std::endl;
using std::fixed;
using std::scientific;
int main()
{
   double x = 0.001234567;
   double y = 1.946e9;
   cout << "Displayed in default format:" << endl << x << 	 << y << endl;
   cout << "
Displayed in scientific format:" << endl << scientific << x << 	 << y << endl;
   cout << "
Displayed in fixed format:" << endl << fixed << x << 	 << y << endl;
   return 0;
}

Displayed in default format:

0.00123457 1.946e+009

Displayed in scientific format: 1.234567e-003 1.946000e+009

Displayed in fixed format: 0.001235 1946000000.000000

#include <iostream.h>
main(void)
{
  float a=100100.0, b=0.08;
  cout.setf(ios::right|ios::scientific|ios::showpoint);
  cout.width(20);  
  cout <<(-a*b);
  return 0;
}

-8.008000e+003

#include <iostream>
#include <iomanip>
#include <limits>
using std::cout;
using std::endl;
using std::setprecision;
using std::numeric_limits;
int main() {
  const double pi = 3.14;
  cout << endl;
  for(double radius = .2 ; radius <= 3.0 ; radius += .2)
    cout << "radius = "
    << setprecision(numeric_limits<double>::digits10 + 1)
    << std::scientific << radius<< "  area = "
         << std::setw(10) << setprecision(6)<< std::fixed << pi * radius * radi
us << endl;
  return 0;
}

radius = 2.0000000000000001e-001 area = 0.125600

radius = 4.0000000000000002e-001 area = 0.502400 radius = 6.0000000000000009e-001 area = 1.130400 radius = 8.0000000000000004e-001 area = 2.009600 radius = 1.0000000000000000e+000 area = 3.140000 radius = 1.2000000000000000e+000 area = 4.521600 radius = 1.3999999999999999e+000 area = 6.154400 radius = 1.5999999999999999e+000 area = 8.038400 radius = 1.7999999999999998e+000 area = 10.173600 radius = 1.9999999999999998e+000 area = 12.560000 radius = 2.1999999999999997e+000 area = 15.197600 radius = 2.3999999999999999e+000 area = 18.086400 radius = 2.6000000000000001e+000 area = 21.226400 radius = 2.8000000000000003e+000 area = 24.617600

#include <iostream>
#include <iomanip>
#include <string>
using namespace std;
int main( ) {
   ios_base::fmtflags flags = cout.flags( );
   double pi = 3.14285714;
   cout << "pi = " << setprecision(5) << pi << 
;
   cout.flags(flags);
}

pi = 3.1429