istack.cpp

Think in C++ 第二版源码

//: C16:IStack.cpp
// From Thinking in C++, 2nd Edition
// Available at http://www.BruceEckel.com
// (c) Bruce Eckel 1999
// Copyright notice in Copyright.txt
// Simple integer stack
#include "../require.h"
#include <iostream>
using namespace std;

class IStack {
  static const int ssize = 100;
  int stack[ssize];
  int top;
public:
  IStack() : top(0) { stack[top] = 0; }
  void push(int i) {
    if(top < ssize) stack[top++] = i;
  }
  int pop() {
    return stack[top > 0 ? --top : top];
  }
  friend class IStackIter;
};

// An iterator is a "super-pointer":
class IStackIter {
  IStack& S;
  int index;
public:
  IStackIter(IStack& is)
    : S(is), index(0) {}
  int operator++() { // Prefix form
    if (index < S.top - 1) index++;
    return S.stack[index];
  }
  int operator++(int) { // Postfix form
    int returnval = S.stack[index];
    if (index < S.top - 1) index++;
    return returnval;
  }
};
// For interest, generate Fibonacci numbers:
int fibonacci(int n) {
  const int sz = 100;
  require(n < sz);
  static int f[sz]; // Initialized to zero
  f[0] = f[1] = 1;
  // Scan for unfilled array elements:
  int i;
  for(i = 0; i < sz; i++)
    if(f[i] == 0) break;
  while(i <= n) {
    f[i] = f[i-1] + f[i-2];
    i++;
  }
  return f[n];
}

int main() {
  IStack is;
  for(int i = 0; i < 20; i++)
    is.push(fibonacci(i));
  // Traverse with an iterator:
  IStackIter it(is);
  for(int j = 0; j < 20; j++)
    cout << it++ << endl;
  for(int k = 0; k < 20; k++)
    cout << is.pop() << endl;
} ///:~