//SGI STL以deque作为缺省情况下的stack底部结构,stack没有迭代器，不提供遍历功能

//queue的实现类似stack，也是以deque作为缺省底层结构

template <class T,class Sequence=deque<T>>

class stack

{

    friend bool operator==__STL_NULL_TMPL_ARGS(const stack&, const stack&);

    friend bool operator<__STL_NULL_TMPL_ARGS(const stack&, const stack&);

public:

    typedef typename Sequence::value_type value_type;

    typedef typename Sequence::size_type size_type;

    typedef typename Sequence::reference reference;

    typedef typename Sequence::const_reference const_reference;

protected:

    Sequence c;//底层容器

public:

    bool empty()const{ return c.empty(); }

    size_type size()const{ return c.size() }

    reference top(){ return c.back; }

    const_reference top()const{ return c.back(); }

    void push(const value_type& x){ c.push_back(x); }

    void pop(){ c.pop_back(); }

};

template<class T,class Sequence>

bool operator==(const stack<T, Sequence>&x, const stack<T, Sequence>&y)

{

    return x.c == y.c;

}

template<class T, class Sequence>

bool operator<(const stack<T, Sequence>&x, const stack<T, Sequence>&y)

{

    return x.c < y.c;

}