#include <boost/iterator/transform_iterator.hpp>

#include <functional>
#include <iostream>
#include <string>
#include <utility>
#include <vector>
 
 
template <class PairT>
struct select1st
	: public std::unary_function<PairT,
				     typename PairT::first_type &>
{
	typename PairT::first_type &
	operator()(PairT & pair) const { return pair.first; }
};

template <class PairT>
struct select1st<PairT const>
	: public std::unary_function<PairT const,
				     typename PairT::first_type const &>
{
	typename PairT::first_type const &
	operator()(PairT const& pair) const { return pair.first; }
};


class store {
private:
	typedef std::pair<int, std::string> data_type;
	typedef std::vector<data_type> vector_type;

public:
	store() {
		data.push_back(std::make_pair(1, "angus"));
		data.push_back(std::make_pair(2, "brendan"));
		data.push_back(std::make_pair(3, "chris"));
		data.push_back(std::make_pair(4, "david"));
	}

	typedef boost::transform_iterator<select1st<data_type>,
					  vector_type::iterator>
	first_iterator;

	typedef boost::transform_iterator<select1st<data_type const>,
					  vector_type::const_iterator>
	const_first_iterator;

	first_iterator begin_first() 
	{
		return boost::make_transform_iterator(
			data.begin(),
			select1st<data_type>());
	}

	first_iterator end_first()
	{
		return boost::make_transform_iterator(
			data.end(),
			select1st<data_type>());
	}

	const_first_iterator begin_first() const
	{
		return boost::make_transform_iterator(
			data.begin(),
			select1st<data_type const>());
	}

        const_first_iterator end_first() const
	{
		return boost::make_transform_iterator(
			data.end(),
			select1st<data_type const>());
	}

private:
	typedef std::pair<int, std::string> data_type;
	std::vector<data_type> data;
};

int main() {
	store my_store;
	store const & my_const_store = my_store;
	store::const_first_iterator const begin = my_const_store.begin_first();
	store::const_first_iterator const end = my_const_store.end_first();
	for (store::const_first_iterator it = begin; it != end; ++it) {
		std::cout << *it << '\n';
	}
	std::flush(std::cout);
	return 0;
}