如何在复合类型上使用Boost.Bind？

map

pair

first

int

second

pair

it

it->second.first

min_element

second.first

typedef std::pair<short, float> val_type;
typedef std::map<int, val_type> map_type;
map_type m;

operator<

#include <boost/bind.hpp>
#include <boost/lambda/lambda.hpp>
using boost::bind;

// Comparison is (_1.second.first < _2.second.first)
std::cout <<
  std::min_element(m.begin(), m.end(),
    bind(&val_type::first, bind(&map_type::iterator::value_type::second, _1))
    <
    bind(&val_type::first, bind(&map_type::iterator::value_type::second, _2))
  )->second.first;

boost::lambda::bind

min_element(map.begin(), map.end(),
            compose2(less<short>(),
                     compose1(select1st<pair<short, float> >(),
                              select2nd<map<int, pair<short, float>
                                           >::value_type>()),
                     compose1(select1st<pair<short, float> >(),
                              select2nd<map<int, pair<short, float>
                                           >::value_type>()))
           ).second.first;

bind

first

second

template <typename F, typename S>
struct select_first : std::binary_function<std::pair<F, S>&, F&>
{
    F& operator()(std::pair<F, S>& toConvert)
    {
        return toConvert.first;
    }
};