/*
          +----------------------------------+                
          |  AList                           |                
          +----------------------------------+                
          | boolean contains(ImageFile that) | 
          +----------------------------------+                
                         |                    
                        / \                   
                        ---                   
                         |                    
           ---------------------------          
           |                         |          
    +-------------+         +-----------------+  
    | MTList      |         | ConsList        |  
    +-------------+         +-----------------+  
    +-------------+     +---| ImageFile first | 
                        |   | AList rest      |   
                        |   +-----------------+ 
	            		v
                +---------------+    
                | ImageFile     |    
                +---------------+    
                | String name   |     
                | int    width  |      
                | int    height |      
                | String kind   |      
                +---------------+    

 */  

//to represent a list of ImageFile objects
interface AList{
  
  // does this list contain that ImageFile
  public boolean contains(ImageFile that);
}