//: C09:Stack4.h
// From Thinking in C++, 2nd Edition
// Available at http://www.BruceEckel.com
// (c) Bruce Eckel 2000
// Copyright notice in Copyright.txt
// With inlines
#ifndef STACK4_H
#define STACK4_H
#include "../require.h"

class Stack {
  struct Link {
    void* data;
    Link* next;
    Link(void* dat, Link* nxt): 
      data(dat), next(nxt) {}
  }* head;
public:
  Stack() : head(0) {}
  ~Stack() {
    require(head == 0, "Stack not empty");
  }
  void push(void* dat) {
    head = new Link(dat, head);
  }
  void* peek() const { 
    return head ? head->data : 0;
  }
  void* pop() {
    if(head == 0) return 0;
    void* result = head->data;
    Link* oldHead = head;
    head = head->next;
    delete oldHead;
    return result;
  }
};
#endif // STACK4_H ///:~