text: //
  //  MGQueue.h
  //  Study
  //
  //  Created by Mark Gage on 2017-07-27.
  //  Copyright © 2017 Mark Gage. All rights reserved.
  //
  
  #import <Foundation/Foundation.h>
  
  @protocol MGQueue <NSObject>
  - (void)enqueue:(id)item;
  - (id)dequeue;
  - (BOOL)isEmpty;
  - (void)display;
  @end
  