#include <map>
  bool empty() const;

The empty() function returns true if the map has no elements, false otherwise.

For example, the following code uses empty() as the stopping condition on a while loop to clear a map and display its contents in order:

  struct strCmp {
    bool operator()( const char* s1, const char* s2 ) const {
      return strcmp( s1, s2 ) < 0;
    }
  };

  ...

  map<const char*, int, strCmp> ages;
  ages["Homer"] = 38;
  ages["Marge"] = 37;
  ages["Lisa"] = 8;
  ages["Maggie"] = 1;
  ages["Bart"] = 11;

  while( !ages.empty() ) {
    cout << "Erasing: " << (*ages.begin()).first << ", " << (*ages.begin()).second << endl;
    ages.erase( ages.begin() );
  }

When run, the above code displays:

  Erasing: Bart, 11
  Erasing: Homer, 38
  Erasing: Lisa, 8
  Erasing: Maggie, 1
  Erasing: Marge, 37