c++ cout 格式化输出浮点数、整数及格方法

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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 << '\t' << y << endl;   cout << "\nDisplayed in scientific format:" << endl << scientific << x << '\t' << y << endl;   cout << "\nDisplayed in fixed format:" << endl << fixed << x << '\t' << 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 * radius << 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 << '\n';   cout.flags(flags);}

pi = 3.1429

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