Stack

#include<iostream>#include<string>#include<cassert>using namespace std;template <class T>class Stack{public:enum { DefaultStack = 50, EmptyStack = -1 };Stack();Stack(int);~Stack();void push(const T&);T pop();T topNoPop() const;bool empty() const;bool full() const;private:T *elements;int top;int size;void allocate(){elements = new T[size];top = EmptyStack;}void msg(const char* m) const{cout << "***" << m << "***" << endl;}friend ostream& operator<<(ostream&, const Stack<T>&);};template <class T>Stack<T>::Stack(){size = DefaultStack;allocate();}template <class T>Stack<T>::Stack(int s){if (s < 0)//判断为负数{s*=-1；}else if (0==s){s = DefaultStack;}size = s;allocate();}template <class T>Stack<T>::~Stack(){delete[] elements;}template <class T>void Stack<T>::push(const T& e){assert(!full());if (!full())elements[++top] = s;else{msg("Stack full!");}}template <class T>T Stack<T>::pop(){assert(!empty());if (!empty()){return elements[--top];}else{msg("Stack empty!");T dummy_value;return dummy_value;}}template <class T>T Stack<T>::topNoPop() const{assert(top > EmptyStack);if (!empty())return elements[top];else{msg("Stack Empty!");T dummy_value;return dummy_value;}}template <class T>bool Stack<T>::empty() const{return top <= EmptyStack;}template <class T>bool Stack<T>::full() const{return top + 1 >= size;}template <class T>ostream& operator<<(ostream& os, const Stack<T>& s){s.msg("Stack content:");int t = s.top;while (t>s.EmptyStack){cout << s.elements[t--] << endl;return os;}}