template<typename T> class Forest {
public:
// functions to do something with the heap,
// but do not leak internals.
void do_something(T const& x) {
    // pick a heap and add an element
    mHeaps[0].push(x);
}

private:
// simple wrapper around STL heap functions
class Heap {
public:
    void push(T const& x) {
        mData.push_back(x);
        std::push_heap(mData.begin(), mData.end());
    }

    T pop() {
        std::pop_heap(mData.begin(), mData.end());
        T const tmp(mData.back());
        mData.pop_back();
    }

    private:
        std::vector<T> mData;
    };

std::vector<Heap> mHeaps;
};