// Al declarar un constructor, el compilador ya no genera el que no recibe nada.
class Range {
public:
    Range(int low, int high) : low_(low), high_(high) {}

    int width() const {
        return high_ - low_;
    }

private:
    int low_;
    int high_;
};

int main() {
    Range range;
    return range.width();
}