stl类stack

template<class T,class Container=deque<T>>
class stack
{
	public:
		explicit stack(const Container &cnt =Container());
		//default constructor ;initializes an empty stack
		//precondition :none
		//postcondition :an empty array exist
		bool empty()const;
		//determines whether the stack is empty
		//precondition :none
		//postcondition :returns true if the stack is emtpy
		//otherwise returns false
		size_type size()const;
		//determinate the size of the stack.the return type
		//size_type is an integral type
		//precondition :none
		//postcondition :returns the number of items that
		//are currents in the stack
		T &top();
		//returns a reference to the top of the stack
		//precondition None;
		//postcondition :the item remains on the stack;
		void pop();
		//removes the top item in the stack
		//precondition :none
		//postcondition :the items most recently added
		//is removed from the stack
		void push();
		//adds an items to the top of the stack
		//precondition :none
		//postcondition :Item x is the top of the stack
};