template <class T, double(T::*Accessor)(void)const>
    struct Compare {
        bool operator()(const T &a, const T &b) {
            return (a.*Accessor)() < (b.*Accessor)();
        }
    };

    struct NormalizeStruct {
        double min;
        double diff;

        NormalizeStruct(double min,
                        double diff) : min(min), diff(diff)
            { /* empty */ }
    };

    template <class T, double(T::*Accessor)(void)const>
    NormalizeStruct normalize_one_cat(const std::vector<T> &vec_for_normalization) {
        Compare<T, Accessor> cmp;
        double max_el = ((*max_element(vec_for_normalization.begin(),
                                       vec_for_normalization.end(),
                                       cmp)).*Accessor)();
        double min_el = ((*min_element(vec_for_normalization.begin(),
                                       vec_for_normalization.end(),
                                       cmp)).*Accessor)();

        double diff_el = max_el - min_el;

        return NormalizeStruct(min_el, diff_el);
    }

    std::vector<SpamString> normalize(const std::vector<SpamString> &spam_strings) {
        std::vector<SpamString> normalize_strings;

        NormalizeStruct all = normalize_one_cat<SpamString,
                                                &SpamString::getAll>(spam_strings);

        NormalizeStruct uppers_all = normalize_one_cat<SpamString,
                                                       &SpamString::getUppersAll>(spam_strings);

        NormalizeStruct marks_all = normalize_one_cat<SpamString,
                                                      &SpamString::getMarksAll>(spam_strings);

        NormalizeStruct tabs_all = normalize_one_cat<SpamString,
                                                     &SpamString::getTabsAll>(spam_strings);

        NormalizeStruct nums_all = normalize_one_cat<SpamString,
                                                     &SpamString::getNumsAll>(spam_strings);

        for(vector<SpamString>::const_iterator it = spam_strings.begin();
            it != spam_strings.end(); ++it)
            normalize_strings.push_back(
                SpamString((it->getAll()-all.min)/all.diff,
                           (it->getUppersAll()-uppers_all.min)/uppers_all.diff,
                           (it->getMarksAll()-marks_all.min)/marks_all.diff,
                           (it->getTabsAll()-tabs_all.min)/tabs_all.diff,
                           (it->getNumsAll()-nums_all.min)/nums_all.diff,
                           it->getType()));

        return normalize_strings;
    }