CSCI3136 Assignment 10
Instructor: Alex Brodsky
Due: 9:00am, Monday, July 27, 2020
1. [5 marks] In one of the examples for Lecture 20, we saw how to implement a closure that can be used with the list-visitor function to compute the average of a list. Using the example as a starting point, implement a function called new-range, which returns a closure that can be used with the list-visitor function to compute the range of a list of numbers.
Recall that the range of a list of numbers is defined as
range (L) = max (L) − min (L)
Write the new-range function in a file called range-visitor.scm.
2. [5 marks] In Java we can instantiate an iterator of a list. Each time the iterator is called, it returns the next item in a list. Implement a function called new-abs-iterator that takes a list of numbers as an argument and returns an iterator (implemented using a closure) that returns the absolute value of the next item in the list when it is called. Once the list is empty, the boolean #f should be returned. For example
> (define abx (new-abs-iterator ’(-1 2 -3 4)))
> (abx)
1
> (abx)
2
> (abx)
3
> (abx)
4
> (abx)
#f
>
Write the new-abs-iterator function in a file called abs-iterator.scm. Note: Scheme has an abs function that returns the absolute value of a number.
3. [5 marks] Using your code from Question 2 as a starting point, Implement a function called new-positive-iterator that takes a list of numbers as an argument and returns an iterator (implemented using a closure) that returns the next positive item in the list when it is called. Once the list is empty, the boolean #f should be returned. For example
1
CSCI3136 Summer 2020 Assignment 10
> (define pos (new-positive-iterator ’(-1 2 -3 4)))
> (pos)
2
> (pos)
4
> (abx) #f
>
Write the new-positive-iterator function in a file called positive-iterator.scm.
4. [5 marks] Rewrite the following code as a tail-recursive function, called max-tr. Write the
max-tr function in a file called max.scm.
(define max-nt (lambda (L)
(if (null? (cdr L))
(car L)
(max (car L) (max-nt (cdr L)))
)
) )
5. [Bonus 5 marks] Using the code in bst.scm as a starting point implement a function called new-bst-iterator that takes a BST as an argument and returns an iterator (implemented using a closure) that returns the next item in an in-order traversal of the BST when it is called. Once the traversal is complete, the boolean #f should be returned.
Write the new-bst-iterator function in the file bst.scm. Marking Scheme
1. Marking scheme for Questions 1, 2, 3, 4, and 5 (Bonus).
2. Marking scheme for overall code clarity.
3 points
2 points
1 point
0 points
Solution
Solution looks correct and covers all cases
Solution looks mostly correct and covers some cases
Solution represents a good attempt
No solution provided
Functionality
Solution works on test input
Solution works on some test inputs
Solution does not work
2 points
1 point
0 points
Understandability
Code is easy to understand
Code is a little hard to un- derstand
Code is unintelligible or not submitted
Formatting
Code is well formatted and indented
Code is inconsistently for- matted
Code is poorly formatted or not submitted
Commenting
Comments are used where appropriate
No comments present or no code submitted
2
CSCI3136: Assignment 10
Summer 2020
Student Name
Login ID
Student Number
Student Signature
Mark
Question 1 Question 2 Question 3 Question 4
Bonus Question 4 Overall code clarity
/5
/5
/5
/5
/5
/5
Total
/25
Comments:
Assignments are due by 9:00am on the due date. Assignments must be submitted elec- tronically via Brightspace. Please submit a zip (.zip) file of your code. Please do not use another archiving format as the markers may not be able to open it.
Plagiarism in assignment answers will not be tolerated. By submitting their answers to this assignment, the authors named above declare that its content is their original work and that they did not use any sources for its preparation other than the class notes, the text- book, and ones explicitly acknowledged in the answers. Any suspected act of plagiarism will be reported to the Facultys Academic Integrity Officer and possibly to the Senate Discipline Committee. The penalty for academic dishonesty may range from failing the course to ex- pulsion from the university, in accordance with Dalhousie University’s regulations regarding academic integrity.