[Tutor] confused by linked queue

[Danny Yoo]

> One of my problems in conecptualizing this is that I thought a linked 
> queue was just a linked list.  Is a linked queue a linked list?  There 
> seems to be a subtle difference...

Hi Chris,

I think you mean to ask:

     Is a "queue" a linked list?


Here's another particular possible queue class that does something 
similar, but with Python's regular lists rather than a linked list:

######################################
class ArrayQueue:
     def __init__(self):
         self.elements = []

     def isEmpty(self):
         return len(self.elements) == 0

     def insert(self, elt):
         self.elements.append(elt)

     def remove(self):
         return self.elements.pop(0)
######################################

This works on a different principle than the linked list queue, but it 
does the same stuff.  The main idea is that a "queue" can be anything, as 
long as it supports three operations:

     * isEmpty
     * insert
     * remove

That is, a queue is an abstract concept, and the LinkedQueue and 
ArrayQueue classes are particular, concrete implementations of that 
abstract concept.

A mechanic is someone who's good with their hands.  MacGyver is a 
particular, concrete mechanic who knows how to blow things up with 
toothpaste.  MacGyver is an implementation of a mechanic.

A "car vehicle" is an abstract concept; a Camry is a particular, concrete 
car that anyone can look at and agree is a car.  We can also look at a 
Prius and also agree that this is a car, even though the engine underneath 
the hood might look weird.


I hope this is making some sort of sense.  *grin*