Is there a standard C++ function object for taking apart a std::pair?

Question

Does anyone know if there\'s a de-facto standard (i.e., TR1 or Boost) C++ function object for accessing the elements of a std::pair? Twice in the past 24 hours I\'ve wished

Answer 1

What about using combinations of different containers.

For example when I wanted to partition a vector into items contained in a supplemental map and items that where not contained in the supplemental map I used the following:

typedef int DWORD; 
typedef std::pair user_info; 
typedef std::map USER_MAP; 
typedef std::vector VEC_STAFF; 

VEC_STAFF::iterator it = std::partition(Staff.begin(), Staff.end(), (bind(&USER_MAP::find, m_Users, _1) != m_Users.end()));

Now I have a second problem - during the running of the application the status bool of user_info can change, and later on I want to re-partition the vector with items that have a status bool of true rather than just being contained in the supplemental map.

However I seem to have a problem accessing the second item of a nested pair.

I tried the following but I cannot seem to access the nested pair!

CActiveUsers::VEC_STAFF::const_iterator itCurEnd = partition(Staff.begin(), Staff.end(), bind(&USER_MAP::value_type::second::second, bind(&USER_MAP::find, &m_Users, _1)) == true);