[Boost-users] How to bind the first of a pair?

I have a map with key is a pair: typedef map < pair, string> pairMapString; pair key(1,3); map[key] = "one"; How can I create a binary function using boost lamba which check the first value of the pair of the key of the map? void add(pairMapString;& myMap, int x) { iterator& itr = find_if(myMap.begin(), myMap.end(), bind(equal_to < int >(), bind(&BlockDataPairMap::value_type::first::value_type::first, _1 ) , x) ); }