C++クラスで簡単なスタックを実現

             ，      ：

1.ヘッダファイルstack.h

// stack.h -- class definition for the stack ADT
#ifndef STACK_H_
#define STACK_H_

typedef unsigned long Item;

class Stack
{
private:
    enum {MAX = 10};
    Item items[MAX];
    int top;
public:
    Stack();
    bool isempty() const;
    bool isfull() const;
    // push() returns false if stack already is full, ture otherwise
    bool push(const Item & item);   // add item to stack
    // pop() returns false if stack already is empty, ture otherwise
    bool pop(Item & item);
};

#endif

2.クラス関数定義stack.cpp

// stack.cpp -- Stack member functions
#include "stack.h"

Stack::Stack()
{
    top = 0;
}

bool Stack::isempty() const
{
    return 0 == top;
}

bool Stack::isfull() const
{
    return MAX == top;
}

bool Stack::push(const Item & item)
{
    if(top < MAX)
    {
        items[top++] = item;
        return true;
    }
    else
        return false;
}

bool Stack::pop(Item & item)
{
    if(top > 0)
    {
        item = items[--top];
        return true;
    }
    else
        return false;
}

3.テスト、販売員の行動をシミュレートする——バスケットの一番上のものを先に処理する

// stacker.cpp -- testing the Stack class
#include <stdio.h> //    c        
#include <ctype.h> // or cctype for c++
#include <stdlib.h>
#include "stack.h"

int main()
{
    Stack st;
    char ch;
    unsigned long po;
    printf("Please enter A to add a purchase order,
");
    printf("P to process a PO, or Q to quit.
");
    while((1 == scanf("%c", &ch)) && ch != 'Q' && ch != 'q')
    {
        if(!isalpha(ch))
        {
            printf("\aOrder: P or Q !
");
            continue;
        }
        switch(ch)
        {
            case 'A':
            case 'a':
                printf("Enter a PO number to add: ");
                scanf("%d", &po);
                if(st.isfull())
                    printf("Stack already full
");
                else
                    st.push(po);
                break;
            case 'P':
            case 'p':
                if(st.isempty())
                    printf("stack already empty
");
                else
                {
                    st.pop(po);
                    printf("PO #%d popped
", po);
                }
                break;
        }
        //       ，      ，  swith    ，      
        while(getchar() != '
')
            continue;
        printf("Please enter A to add a purchase order,
");
        printf("P to process a PD, or Q to quit.
");
    }
    printf("Bye!
");
    system("pause");
    return 0;
}