重載 && 重載遞增遞和減運算符

class Rule
{
private:
    double m_Length;
public:
    explicit Rule(double lg = 1.0) :m_Length{ lg }{}

    Rule &operator++();
    const Rule operator++(int);

    Rule &operator--();
    const Rule& operator--(int);

    void showRuleLength()
    {
        cout <<"長度："<< this->m_Length << endl;
    }
};

inline Rule& Rule::operator++()
{
    ++(this->m_Length);
    return *this;
}

inline const Rule Rule::operator++(int)　　//返回常量對象，不允許改變
{
    Rule rule{*this};　　　　 //利用複製構造函數建立對象

    ++*this;　　　　　　　　　　//因為首碼++已經重載了
    return rule;　　　　　　　 //返回對象的副本
}

inline Rule& Rule::operator--()
{
    --(this->m_Length);
    return (*this);
}

inline const Rule& Rule::operator--(int)
{
    Rule rule(*this);
    --*this;
    return rule;
}

int main()
{
    Rule a{ 4.0 };
    Rule b;
    b = a++;
    b.showRuleLength();
}