Method operator<

src/fl/stl/multi_map.h:483–491

    }

    bool operator<(const MultiMapTree& other) const {
        for (auto it1 = begin(), it2 = other.begin(); it1 != end() && it2 != other.end(); ++it1, ++it2) {
            if (it1->first < it2->first) return true;
            if (it2->first < it1->first) return false;
            if (it1->second < it2->second) return true;
            if (it2->second < it1->second) return false;
        }
        return size() < other.size();
    }

    bool operator<=(const MultiMapTree& other) const {
        return *this < other || *this == other;