#include <cstdio>

#include <vector>

template <typename T>
class fset : public std::vector<T>
{
public:
    fset<T> operator == (T val) const
    {
        fset<T> nset;
        for (int i = 0; i < std::vector<T>::size(); ++i)
            if ((*this)[i] == val)
                nset.push_back((*this)[i]);
        return nset;
    }
    fset<T> operator != (T val) const
    {
        fset<T> nset;
        for (int i = 0; i < std::vector<T>::size(); ++i)
            if ((*this)[i] != val)
                nset.push_back((*this)[i]);
        return nset;
    }
    fset<T> operator > (T val) const
    {
        fset<T> nset;
        for (int i = 0; i < std::vector<T>::size(); ++i)
            if ((*this)[i] > val)
                nset.push_back((*this)[i]);
        return nset;
    }
    fset<T> operator >= (T val) const
    {
        fset<T> nset;
        for (int i = 0; i < std::vector<T>::size(); ++i)
            if ((*this)[i] >= val)
                nset.push_back((*this)[i]);
        return nset;
    }
    fset<T> operator < (T val) const
    {
        fset<T> nset;
        for (int i = 0; i < std::vector<T>::size(); ++i)
            if ((*this)[i] < val)
                nset.push_back((*this)[i]);
        return nset;
    }
    fset<T> operator <= (T val) const
    {
        fset<T> nset;
        for (int i = 0; i < std::vector<T>::size(); ++i)
            if ((*this)[i] <= val)
                nset.push_back((*this)[i]);
        return nset;
    }

    fset<T> & operator += (T val)
    {
        std::vector<T>::push_back(val);
        return *this;
    }

    T sum () const
    {
        double ssum = 0.0;
        for (int i = 0; i < std::vector<T>::size(); ++i)
            ssum += (*this)[i];
        return ssum;
    }

    T average () const
    {
        return sum() / std::vector<T>::size();
    }
};

int main ()
{
    fset<double> arr;
    arr += 4;
    arr += 5;
    arr += -4;
    arr += -5;

    printf("Average = %f\n",    arr.average());
    printf("Average pos = %f\n",    (arr > 0.0).average());
    printf("Average neg = %f\n",    (arr < 0.0).average());

    return 0;
}