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### User groups

Example user groups shows the availability of set operations on `interval_maps`.

In the example there is a user group `med_users` of a hospital staff that has the authorisation to handle medical data of patients. User group `admin_users` has access to administrative data like health insurance and financial data.

The membership for each user in one of the user groups has a time interval of validity. The group membership begins and ends.

- Using a union operation `+` we can have an overview over the unified user groups and the membership dates of employees.
- Computing an intersection `&` shows who is member of both med_users and admin_users at what times.

    // The next line includes <boost/gregorian/date.hpp>
    // and a few lines of adapter code.
    #include <boost/icl/gregorian.hpp>
    #include <iostream>
    #include <boost/icl/interval_map.hpp>

    using namespace std;
    using namespace boost::gregorian;
    using namespace boost::icl;

    // Type icl::set<string> collects the names a user group's members. Therefore
    // it needs to implement operator += that performs a set union on overlap of
    // intervals.
    typedef std::set<string> MemberSetT;

    // boost::gregorian::date is the domain type the interval map.
    // It's key values are therefore time intervals: discrete_interval<date>. The content
    // is the set of names: MemberSetT.
    typedef interval_map<date, MemberSetT> MembershipT;

    // Collect user groups for medical and administrative staff and perform
    // union and intersection operations on the collected membership schedules.
    void user_groups()
    {
        MemberSetT mary_harry;
        mary_harry.insert("Mary");
        mary_harry.insert("Harry");

        MemberSetT diana_susan;
        diana_susan.insert("Diana");
        diana_susan.insert("Susan");

        MemberSetT chief_physician;
        chief_physician.insert("Dr.Jekyll");

        MemberSetT director_of_admin;
        director_of_admin.insert("Mr.Hyde");

        //----- Collecting members of user group: med_users -------------------
        MembershipT med_users;

        med_users.add( // add and element
          make_pair(
            discrete_interval<date>::closed(
              from_string("2008-01-01"), from_string("2008-12-31")), mary_harry));

        med_users +=  // element addition can also be done via operator +=
          make_pair(
            discrete_interval<date>::closed(
              from_string("2008-01-15"), from_string("2008-12-31")),
              chief_physician);

        med_users +=
          make_pair(
            discrete_interval<date>::closed(
              from_string("2008-02-01"), from_string("2008-10-15")),
              director_of_admin);

        //----- Collecting members of user group: admin_users ------------------
        MembershipT admin_users;

        admin_users += // element addition can also be done via operator +=
          make_pair(
            discrete_interval<date>::closed(
              from_string("2008-03-20"), from_string("2008-09-30")), diana_susan);

        admin_users +=
          make_pair(
            discrete_interval<date>::closed(
              from_string("2008-01-15"), from_string("2008-12-31")),
              chief_physician);

        admin_users +=
          make_pair(
            discrete_interval<date>::closed(
              from_string("2008-02-01"), from_string("2008-10-15")),
              director_of_admin);

        MembershipT all_users   = med_users + admin_users;

        MembershipT super_users = med_users & admin_users;

        MembershipT::iterator med_ = med_users.begin();
        cout << "----- Membership of medical staff -----------------------------------\n";
        while(med_ != med_users.end())
        {
            discrete_interval<date> when = (*med_).first;
            // Who is member of group med_users within the time interval 'when' ?
            MemberSetT who = (*med_++).second;
            cout << "[" << first(when) << " - " << last(when) << "]"
                 << ": " << who << endl;
        }

        MembershipT::iterator admin_ = admin_users.begin();
        cout << "----- Membership of admin staff -------------------------------------\n";
        while(admin_ != admin_users.end())
        {
            discrete_interval<date> when = (*admin_).first;
            // Who is member of group admin_users within the time interval 'when' ?
            MemberSetT who = (*admin_++).second;
            cout << "[" << first(when) << " - " << last(when) << "]"
                 << ": " << who << endl;
        }

        MembershipT::iterator all_ = all_users.begin();
        cout << "----- Membership of all users (med + admin) -------------------------\n";
        while(all_ != all_users.end())
        {
            discrete_interval<date> when = (*all_).first;
            // Who is member of group med_users OR admin_users ?
            MemberSetT who = (*all_++).second;
            cout << "[" << first(when) << " - " << last(when) << "]"
                 << ": " << who << endl;
        }

        MembershipT::iterator super_ = super_users.begin();
        cout << "----- Membership of super users: intersection(med,admin) ------------\n";
        while(super_ != super_users.end())
        {
            discrete_interval<date> when = (*super_).first;
            // Who is member of group med_users AND admin_users ?
            MemberSetT who = (*super_++).second;
            cout << "[" << first(when) << " - " << last(when) << "]"
                 << ": " << who << endl;
        }

    }

    int main()
    {
        cout << ">>Interval Container Library: Sample user_groups.cpp <<\n";
        cout << "-------------------------------------------------------\n";
        user_groups();
        return 0;
    }

    // Program output:
    /*-----------------------------------------------------------------------------
    >>Interval Container Library: Sample user_groups.cpp <<
    -------------------------------------------------------
    ----- Membership of medical staff -----------------------------------
    [2008-Jan-01 - 2008-Jan-14]: Harry Mary
    [2008-Jan-15 - 2008-Jan-31]: Dr.Jekyll Harry Mary
    [2008-Feb-01 - 2008-Oct-15]: Dr.Jekyll Harry Mary Mr.Hyde
    [2008-Oct-16 - 2008-Dec-31]: Dr.Jekyll Harry Mary
    ----- Membership of admin staff -------------------------------------
    [2008-Jan-15 - 2008-Jan-31]: Dr.Jekyll
    [2008-Feb-01 - 2008-Mar-19]: Dr.Jekyll Mr.Hyde
    [2008-Mar-20 - 2008-Sep-30]: Diana Dr.Jekyll Mr.Hyde Susan
    [2008-Oct-01 - 2008-Oct-15]: Dr.Jekyll Mr.Hyde
    [2008-Oct-16 - 2008-Dec-31]: Dr.Jekyll
    ----- Membership of all users (med + admin) -------------------------
    [2008-Jan-01 - 2008-Jan-14]: Harry Mary
    [2008-Jan-15 - 2008-Jan-31]: Dr.Jekyll Harry Mary
    [2008-Feb-01 - 2008-Mar-19]: Dr.Jekyll Harry Mary Mr.Hyde
    [2008-Mar-20 - 2008-Sep-30]: Diana Dr.Jekyll Harry Mary Mr.Hyde Susan
    [2008-Oct-01 - 2008-Oct-15]: Dr.Jekyll Harry Mary Mr.Hyde
    [2008-Oct-16 - 2008-Dec-31]: Dr.Jekyll Harry Mary
    ----- Membership of super users: intersection(med,admin) ------------
    [2008-Jan-15 - 2008-Jan-31]: Dr.Jekyll
    [2008-Feb-01 - 2008-Oct-15]: Dr.Jekyll Mr.Hyde
    [2008-Oct-16 - 2008-Dec-31]: Dr.Jekyll
    -----------------------------------------------------------------------------*/