//文件名:CHAPTER9-11.cpp
#include <set>
#include <iostream>
#if _MSC_VER > 1020   // if VC++ version is > 4.2
   using namespace std;  // std c++ libs implemented in std
#endif
int main( )
{
   set <int> s1, s2;
   s1.insert ( 1 );
   if ( s1.empty( ) )
      cout << "The set s1 is empty." << endl;
   else
      cout << "The set s1 is not empty." << endl;
   if ( s2.empty( ) )
      cout << "The set s2 is empty." << endl;
   else
      cout << "The set s2 is not empty." << endl;
}