StackInterface.h

//Â  Created by Frank M. Carrano and Timothy M. Henry.
//Â  Copyright (c) 2017 Pearson Education, Hoboken, New Jersey.

/** @file StackInterface.h */

#ifndef STACK_INTERFACE_
#define STACK_INTERFACE_

template<class ItemType>
class StackInterface
{
public:
    /** Sees whether this stack is empty.
     @return True if the stack is empty, or false if not. */
    virtual bool isEmpty() const = 0;

    /** Adds a new entry to the top of this stack.
     @post If the operation was successful, newEntry is at the top of the stack.
     @param newEntry The object to be added as a new entry.
     @return True if the addition is successful or false if not. */
    virtual bool push(const ItemType& newEntry) = 0;

    /** Removes the top of this stack.
     @post If the operation was successful, the top of the stack
     has been removed.
     @return True if the removal is successful or false if not. */
    virtual bool pop() = 0;

    /** Returns the top of this stack.
     @pre The stack is not empty.
     @post The top of the stack has been returned, and
     the stack is unchanged.
     @return The top of the stack. */
    virtual ItemType peek() const = 0;

    /** Destroys object and frees memory allocated by object. */
    virtual ~StackInterface() {  }
}; // end StackInterface
#endif