Displaying numbers in scientific notation : cout float « Development « C++ Tutorial

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2. Development
3. cout float

#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