#include <iostream>
#include <algorithm>
#include <pair.h>
#include <vector>

using namespace std;

int main()
{
    struct comp
    {
        comp(const int& input) : _input(input) {}
        bool operator()(const pair<int, int>& iPair)
        {
            return (iPair.first == _input);
        }
        int _input;
    };

    pair<int, int> pair1(1,3);
    pair<int, int> pair2(2,4);

    vector<pair<int, int> > vec;
    vec.push_back(pair1);
    vec.push_back(pair2);

    vector<pair<int,int> >::iterator it = find(vec.begin(), vec.end(), comp(1));
    if(it != vec.end())
    {
        cout << it->second << endl;
    }

    return 0;

}

In function 'int main()':
Line 27: error: no matching function for call to 'find(__gnu_debug::_Safe_iterator<__gnu_cxx::__normal_iterator<std::pair<int, int>*, __gnu_norm::vector<std::pair<int, int>, std::allocator<std::pair<int, int> > > >, __gnu_debug_def::vector<std::pair<int, int>, std::allocator<std::pair<int, int> > > >, __gnu_debug::_Safe_iterator<__gnu_cxx::__normal_iterator<std::pair<int, int>*, __gnu_norm::vector<std::pair<int, int>, std::allocator<std::pair<int, int> > > >, __gnu_debug_def::vector<std::pair<int, int>, std::allocator<std::pair<int, int> > > >, main()::comp)'
compilation terminated due to -Wfatal-errors.