#include <string>
#include <iostream>
 
int main()
{
  std::string s = "Zahlenfolge: ";
  
  for (int i = 0; i < 10; ++i) s += std::to_string(i) + ' '; 

  std::cout << s << '\n';

  double d = 1e-9; 
  std::cout << d << "==" << std::to_string(d) << "?\n";  // 1e-09==0.000000?
}