14. map::insert

• Use insert( ) to put in a new item only if it isn't there:

  
  #include <cassert>
  #include <string>
  #include <map>
  
  using namespace std;
  typedef map<string, int> MapT;
  typedef MapT::const_iterator MapIterT;
  
  int main()
  {
      MapT amap;
      pair< MapIterT, bool> result =
          amap.insert( make_pair( "Fred", 45 ) );
  
      assert( result.second == true );
      assert( result.first->second == 45 );
  
      result = amap.insert( make_pair( "Fred", 54 ) );
  
      // Fred was already in the map, and result.first
      // simply points there now:
      assert( result.second == false );
      assert( result.first->second == 45 );
  }