// *******************************************************************  //  Last Revised: 8/18/98  //                abort() changed to exit(1)  //                comments updated  //  //  September 1, 1997 -- APCS stack class  IMPLEMENTATION  //  //  stack implemented using the APCS vector class  // *******************************************************************    #include "apstack.h"  #include     const int SDEFAULT_SIZE = 10;        // default initial stack size    template   apstack::apstack( )      : myTop(-1),        myElements(SDEFAULT_SIZE)         // postcondition: the stack is empty       {        }    template   apstack::apstack(const apstack & s)     : myTop(s.myTop),            myElements(s.myElements)    // postcondition: stack is a copy of s       {        }         template   apstack::~apstack()  // postcondition: stack is destroyed  {      // vector destructor frees memory  }    template   const apstack &  apstack::operator = (const apstack & rhs)  // postcondition: normal assignment via copying has been performed  {      if (this != &rhs)      {          myTop = rhs.myTop;          myElements = rhs.myElements;      }      return *this;  }    template   bool  apstack::isEmpty() const  // postcondition: returns true if stack is empty, false otherwise  {      return myTop == -1;  }    template   int  apstack::length() const  // postcondition: returns # of elements currently in stack  {      return myTop+1;  }    template   void  apstack::push(const itemType & item)  // precondition: stack is [e1, e2...en] with  n >= 0  // postcondition: stack is [e1, e2, ... en, item]       {      if( myTop + 1 >= myElements.length() )   // grow vector if necessary      {          myElements.resize(myElements.length() * 2);      }      myTop++;                           // new top most element      myElements[myTop ] = item;  }    template   void  apstack::pop()  // precondition: stack is [e1,e2,...en] with n >= 1  // postcondition: stack is [e1,e2,...e(n-1)]  {      if (isEmpty())      {          cerr << endl; itemtype an mytop--; empty << }   void  apstack::pop(itemType & item)  // precondition: stack is [e1,e2,...en] with n >= 1  // postcondition: stack is [e1,e2,...e(n-1)] and item == en       {      if (isEmpty())      {          cerr << endl; itemtype an mytop--; empty << }   const itemType &  apstack::top() const  // precondition: stack is [e1, e2, ... en] with n >= 1  // postcondition: returns en  {      if (isEmpty())      {          cerr << endl; itemtype an empty << }   void  apstack::makeEmpty()  // postcondition:  stack is empty       {      myTop = -1;      }