/*
 *        File: stack.cpp
 *        Author: Leonid Reyzin (with thanks to David Metcalf)
 *        Date:  January 2002
 *        Class: CS112B1
 *        Assignment: Implementation of stack module
 * -----------------------------------------------------
 */

//#include <iostream.h>
#include "stack.h"      /* declarations of public functions */

/*------------------------------------------------------------*/

        /* Stack::Stack  constructor
        * creates stack and initializes it
        */

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

/*------------------------------------------------------------*/

       /* Stack::Init:
        * Usage:  stack.Init();
        * Initializes a stack.
        */
bool Stack::Init()
{
  count=0;
  return true;
}

/*------------------------------------------------------------*/

       /* Stack::IsEmpty:
        * Usage:  if(stack.IsEmpty()) {...}
        * checks whether a stack is empty.
        */
bool Stack::IsEmpty()
{
  return (count==0);
}

/*------------------------------------------------------------*/

       /* Stack::IsFull:
        * Usage:  if(stack.IsFull()) {...}
        * checks whether a stack is full.
        */
bool Stack::IsFull()
{ 
  return (count==MAXSTACKSIZE);
}

/*------------------------------------------------------------*/

       /* Stack::Push:
        * Usage:  flag= stack.Push(item);
        * pushes item onto stack.
        * returns true if successful.
        */

bool Stack::Push(ItemType item)
{
  if (IsFull())
    return false;
  data[count++]=item;
  return true;
}

/*------------------------------------------------------------*/

       /* Stack::Pop:
        * Usage:  flag= stack.Pop(item);
        * Pops top item off stac; returns true unless
	* the stack is empty and there is nothing to pop
	* (i.e., returns false in case of stack underflow).
        */

bool Stack::Pop(ItemType &item)
{
  if (IsEmpty())
    return false;
  item=data[--count];
  return true;
}

/* ----------- END OF FILE: stack.cpp ---------- */