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Filename : CSTACK.CPP

//----------------------------------------------------------------------
// IMPLEMENTATION FILE (cstack.cpp)
// This module exports an ADT for a stack of characters.
// Stack representation: a vector.
//----------------------------------------------------------------------
#include "cstack.h"

// Private members of class:
// int top; // Subscript of current top item (or -1 if
// // stack is empty)
// char data[MAX_LENG]; // Vector representing the stack
//
// CLASSINV: -1 <= top < MAX_LENG

CharStack::CharStack()
//..................................................................
// Constructor
// POST: top == -1
//..................................................................
{
top = -1;
}

Boolean CharStack::IsEmpty() const
//..................................................................
// POST: FCTVAL == (top == -1)
//..................................................................
{
return (top == -1);
}

Boolean CharStack::IsFull() const
//..................................................................
// POST: FCTVAL == (top == MAX_LENG-1)
//..................................................................
{
return (top == MAX_LENG-1);
}

void CharStack::Push( /* in */ char newItem )
//..................................................................
// PRE: top < MAX_LENG-1 && Assigned(newItem)
// POST: top == top + 1
// && data[top+1] == newItem
//..................................................................
{
data[++top] = newItem;
}

char CharStack::Top() const
//..................................................................
// PRE: top >= 0
// POST: FCTVAL == data[top]
//..................................................................
{
return data[top];
}

void CharStack::Pop()
//..................................................................

// PRE: top >= 0
// POST: top == top - 1
//..................................................................
{
top--;
}