LINQ (WIP)

// Compiled with g++ 4.7
#include <algorithm>
#include <iostream>
#include <iterator>
#include <vector>
#include <list>
#include <functional>

namespace linq
{
    template <typename ContType>
    class linq_impl {
    public:
        typedef typename ContType::value_type value_type;
        typedef typename ContType::const_reference const_reference;
    private:
        typedef std::vector<typename ContType::iterator> inner_cont_type;
        typedef typename inner_cont_type::const_reference inner_cref;

    public:
        class iterator: std::iterator<std::random_access_iterator_tag, value_type> {
            // TODO
        };

    public:
        linq_impl(ContType& cont): vec() {
            this->vec.reserve(cont.size());
            for (auto it = cont.begin(); it != cont.end(); ++it)
                vec.push_back(it);
        }

        template <typename Func = std::less<value_type> >
        linq_impl& orderby(Func func = Func()) {
            std::sort(this->vec.begin(), this->vec.end(), [=] (inner_cref v1, inner_cref v2) {
                return func(*v1, *v2);
            });
            return *this;
        }

        template <typename Func = std::greater<value_type> >
        linq_impl& orderby_descending(Func func = Func()) {
            return orderby(func);
        }

        template <typename Func>
        linq_impl& where(Func func) {
            vec.erase(std::remove_if(this->vec.begin(), this->vec.end(), [=] (inner_cref val) {
                return !func(*val);
            }), this->vec.end());
            return *this;
        }

    public:
        std::vector<value_type> to_vector() {
            // TODO: Use linq_impl::iterator to do this
            std::vector<value_type> result;
            result.reserve(this->vec.size());
            for (auto it = this->vec.begin(); it != this->vec.end(); ++it)
                result.push_back(**it);
            return result;
        }

        std::list<value_type> to_list() {
            // TODO: Use linq_impl::iterator to do this
            std::list<value_type> result;
            for (auto it = this->vec.begin(); it != this->vec.end(); ++it)
                result.push_back(**it);
            return result;
        }

    private:
        inner_cont_type vec;
    };

    template <typename ContType>
    linq_impl<ContType> from(ContType& cont) {
        return linq_impl<ContType>(cont);
    }
}

int main(int argc, char* argv[])
{
    using namespace std;
    int arr[] = { 5, 2, 6, 2, 3, 1, 4 };
    vector<int> vec(begin(arr), end(arr));
    auto query = linq::from(vec)
                      .where([] (int x) { return x % 2 == 0; })
                      .orderby();
    for (auto&& i : query.to_vector())
        cout << i;
}