=====equal_range=====
Syntax:

<code>
    #include <map>
    pair<iterator, iterator> equal_range( const key_type& key );
    pair<const_iterator, const_iterator> equal_range( const key_type& key ) const;
</code>

The function equal_range() returns two iterators - one to the first element
that contains key, another to a point just after the last element that contains
key.

For example, here is a hypothetical input-configuration loader using multimaps,
strings and equal_range():

<code>
  multimap<string,pair<int,int> > input_config;
  
  // read configuration from file "input.conf" to input_config
  readConfigFile( input_config, "input.conf" ); 
  
  pair<multimap<string,pair<int,int> >::iterator,multimap<string,pair<int,int> >::iterator> ii;
  multimap<string,pair<int,int> >::iterator i;
  
  ii = input_config.equal_range("key");         // keyboard key-bindings
  // we can iterate over a range just like with begin() and end()  
  for( i = ii.first; i != ii.second; ++i ) {
    // add a key binding with this key and output
    bindkey(i->second.first, i->second.second); 
  }

  ii = input_config.equal_range("joyb");        // joystick button key-bindings
  for( i = ii.first; i != ii.second; ++i ) {
    // add a key binding with this joystick button and output
    bindjoyb(i->second.first, i->second.second);
  }
  
</code>