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C:/temp/src/j2k/DataType/Parenth.Frd/Stack.cpp

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// Stack.cpp - Stack Class using single-link Implementation 
#include "Stack.hpp"

Stack::Stack() {                        // Default Constructor
   top  = NULL;
   size = 0;
}

Stack::Stack( DBase* item ) {           // First item Constructor
    top  = new Link( item, NULL );
    size = 1;
}

Stack::Stack( const Stack& stk ) {      // Copy Constructor
    Link* fromCurr = stk.top;
    Link* toCurr   = new Link( *fromCurr );

   top = toCurr;                       // Setting the top pointer
    size = 1;

    while ( fromCurr->next != NULL ) {  // Is it the end of the from Stack ?

        fromCurr = fromCurr->next;      // Move forward in the reading stack

        toCurr->next = new Link( *fromCurr ); // Copy the next Link content

        toCurr = toCurr->next;          // Move forward in the writing stack
        size++;                         // We just added a new Link
    }

    if ( size != stk.size ) {
        cout << "An error occured while copying the Stack to a new Stack\n";
    }
}

void Stack::push( DBase* item ) {   // Insert an item at the top
    top = new Link( item, top );
    size++;
}

DBase* Stack::pop() {               // Remove an item from the top

   if ( isEmpty() )
      return NULL;

    DBase* dtemp = top->element;
    Link* ltemp = top->next;

    delete top;
    top = ltemp;
    size--;

    return dtemp;
}

void Stack::clear() {               // Clear the stack
      if ( isEmpty() )           // If it's empty then get out.
      return;

   while( top != NULL ) {
        Link* temp = top;
        top = top->next;
        delete temp;
        size--;
    }

    assert( top == NULL );
}

DBase& Stack::topValue() const {    // What's the top Value ?
    assert( !isEmpty() );
    return *top->element;
}

void Stack::display() const {
    Link* curr = top;

   if ( isEmpty() )           // If it's empty then get out.
      return;

   while ( curr->next != NULL ) {  // Is it the end of the from Stack ?

      curr->element->display();
        curr = curr->next;       // Move forward in the reading stack
    }

}

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