求助:stl中 MAP怎么用copy以迭代的方式输出,代码已贴出,无法编译通过

#include <iostream>
#include <string>
#include <map>
#include <algorithm>
#include <iterator>

typedef std::map<int,std::string> map_test;
typedef std::pair<int,std::string> pair_test;
typedef std::ostream_iterator<pair_test> ostream_itor;

namespace std
{
    std::ostream& operator<<( std::ostream& os, const pair_test& obj )
    {
        return os << obj.first << ", " << obj.second;
    }
}

using namespace std;

int main()
{
    map_test te;
    for( size_t i=0; i<5; ++i )
        te.insert( make_pair(i,"abc") );

    copy( te.begin(), te.end(), ostream_itor(cout,"\n") );

    return 0;
}