Work in groups of 2 or 3.
The lab explores lists and recursion.
Examples we have considered in class, with solutions: introduction to lists and list and recursion exercises.
Problems in this task do not require recursion. You may not use any list functions other than first, rest, cons, empty?, list. All functions must have signatures, descriptions, and check-expects.
Question 1 Write a function has-one-element? that, given a list, returns #true if the list has exactly one element and #false otherwise:
(check-expect (has-one-element? (list 2 3 5 6)) #false)
(check-expect (has-one-element? empty) #false)
(check-expect (has-one-element? (list 2)) #true)
Question 2 Write a function has-more-than-one-element? that, given a list, returns #true if the list has more than one element, and #false otherwise:
(check-expect (has-more-than-one-element? (list 2 3 5 6)) #true)
(check-expect (has-more-than-one-element? empty) #false)
(check-expect (has-more-than-one-element? (list 2)) #false)
These problems use recursion. Use the examples we did in class as sample
code. All functions must have signatures, descriptions, and
check-expects (add check-expects as needed).
Note that list function (used in check-expects below)
is an easy way to create a list of several
elements without having to repeat cons many times.
As an example of how it works, (list 2 3) creates
a list (cons 2 (cons 3 empty)).
product that consumes a list of numbers and returns their product. It returns 1 for an empty list.
(check-expect (product (list 2 3 -1)) -6)
(check-expect (product (list 4 6 0 8)) 0)
(check-expect (product empty) 1)
Question 2 (4 points)
Write a function sum-non-negative that adds up all non-negative
numbers in a list.
(check-expect (sum-non-negative (list -2 3 0 -1 5)) 8)
(check-expect (sum-non-negative (list 4 8)) 12)
(check-expect (sum-non-negative (list -1 -2)) 0)
Question 3 (4 points) Write a function count-odd that consumes a list of numbers and returns the number of odd numbers in the list.
(check-expect (count-odds (list 2 3 1 5 0)) 3)
(check-expect (count-odds (list 4 6 8)) 0)
(check-expect (count-odds empty) 0)
Question 4 (5 points) Write a function sum-x-coords that consumes a list of positions and returns the sum of their x coordinates.
(check-expect (sum-x-coords (list (make-posn 10 20) (make-posn 20 50))) 30)
(check-expect (sum-x-coords (list (make-posn 10 -20) (make-posn 10 0))) 20)
(check-expect (sum-x-coords empty) 0)
Question 5 (5 points) Write a function first-odd that consumes a list of numbers and returns the first odd number. Use the predefined function odd? to determine if a number is odd. If no number in the list is odd, return #false.
(check-expect (first-odd (list 2 3 1 5 0)) 3)
(check-expect (first-odd (list 4 6 8)) #false)
(check-expect (first-odd empty) #false)
Make sure that your file is named correctly:
Name your file with the combination of your last names, no spaces, followed by the word "Lab"
and the lab number.
For instance,
if your last names are Smith and Lee, the file name should be SmithLeeLab5.rkt
If there are others in the class with the same name as yours, you your initial in addition
to your last name: MSmithJLeeLab5.rkt
At least one person in the group must submit it via canvas as a file upload (make sure it's that .rkt file).
Make a comment indicating who you worked with. The other person (or people) in the group may submit the same file and also
indicate who was in the group or just make a comment listing all your group members (note: if you don't submit a note listing
your group members,
your work may not be counted, even if your group partners list you as the group member).