#include <iostream>
#include <cmath>
#include <sstream>
using namespace std;

int main()
{
    double pi;
    stringstream ss ;
    ss << "3.14";
    ss >> pi;
    cout << pi << endl;
    cout << "showpoint:" << showpoint << pi << endl;
    cout << ss.str() << endl;
    ss.clear(); //clearing
    ss << 3.15 << " " << "3.16";
    cout << ss.str() << endl;
    ss.str(""); //clearing.
    ss << 3.15 << " " << "3.16";
    cout << ss.str() << endl;

    ss.clear(); //clearing
    ss.str(""); //clearing.

    // from integer to charactor string
    ss << 123 << " NUMBER";
    cout << ss.str() << endl;

    for( int i=0; i<10; i++ ){
      ss.str(""); //clearing.
      ss << "sample" << i << ".dat";
      cout << ss.str() << endl;
    }
    double ccc;
    ss>>ccc;
    cout << "char=" << ccc << endl;
  return 0;
}

----------------------Œ‹‰Ê‚Í
$ ./a.exe
3.14
showpoint:3.14000
3.14
3.143.15 3.16
3.15 3.16
123 NUMBER
sample0.dat
sample1.dat
sample2.dat
sample3.dat
sample4.dat
sample5.dat
sample6.dat
sample7.dat
sample8.dat
sample9.dat
char=5.22202e-307