DSSL2 DRRACKET write, Constructs an empty ListStack. Construct an empty ListQueue. Enqueue five songs of your choice to the given queue, then return the first song that should play.

#lang dssl2 #lang dssl2

# HW2: Stacks and Queues

import ring_buffer

interface STACK[T]: def push(self, element: T) -> NoneC def pop(self) -> T def empty?(self) -> bool?

# Defined in the `ring_buffer` library; copied here for reference. # Do not uncomment! or you'll get errors. # interface QUEUE[T]: # def enqueue(self, element: T) -> NoneC # def dequeue(self) -> T # def empty?(self) -> bool?

# Linked-list node struct (implementation detail): struct _cons: let data let next: OrC(_cons?, NoneC)

### ### ListStack ###

class ListStack[T] (STACK):

# Any fields you may need can go here.

# Constructs an empty ListStack. def __init__ (self): pass # ^ YOUR CODE GOES HERE

# Other methods you may need can go here.

test "woefully insufficient": let s = ListStack() s.push(2) assert s.pop() == 2

### ### ListQueue ###

class ListQueue[T] (QUEUE):

# Any fields you may need can go here.

# Constructs an empty ListQueue. def __init__ (self): pass # ^ YOUR CODE GOES HERE

# Other methods you may need can go here.

test "woefully insufficient, part 2": let q = ListQueue() q.enqueue(2) assert q.dequeue() == 2

### ### Playlists ###

struct song: let title: str? let artist: str? let album: str?

# Enqueue five songs of your choice to the given queue, then return the first # song that should play. def fill_playlist (q: QUEUE!): pass # ^ YOUR CODE GOES HERE

test "ListQueue playlist": pass

# To construct a RingBuffer: RingBuffer(capacity) test "RingBuffer playlist": pass