#lang racket
; Returns the length of a list.
(define (list-length xs)
  (if (null? xs)
      0
      (+ 1 (list-length (cdr xs)))))

  
  
  
  
  
; Returns the sum of a list of numbers.
(define (sum xs) 0)

  
  
  
  
  
; Returns a list with consecutive integers in order from lo to hi.
(define (range lo hi) null)

  
  
  
  
  
; Returns a list where each element is the square
; of the corresponding element in xs.
(define (squares xs) null)

  
  
  
  
  
; Returns a list containing only even numbers in xs, in order.
(define (evens xs) null)

  
  
  
  
  
  
; Returns #t if the list ys contains element x and #f otherwise.
(define (contains? x ys) #f)

  
  
  
  
  
  
; Returns a new list containing all the elements of ys, in order,
; except x.
(define (remove x ys) null)

  
  
  
  
  
  
  
  
; Returns #t if the list is in sorted order and #f otherwise.
(define (sorted? xs) #f)

  
  
  
  
  
  
  
  
; Returns a list containing all of the elements of xs, but
; with no duplicates.
(define (dedup xs) null)