CS 61A: Homework 8

Due by 11:59pm on Wednesday, 4/15

Instructions

Download hw08.zip. Inside the archive, you will find a file called hw08.scm, along with a copy of the OK autograder.

Submission: When you are done, submit with python3 ok --submit. You may submit more than once before the deadline; only the final submission will be scored.

Using OK

The ok program helps you test your code and track your progress. The first time you run the autograder, you will be asked to log in with your @berkeley.edu account using your web browser. Please do so. Each time you run ok, it will back up your work and progress on our servers. You can run all the doctests with the following command:

python3 ok

To test a specific question, use the -q option with the name of the function:

python3 ok -q <function>

By default, only tests that fail will appear. If you want to see how you did on all tests, you can use the -v option:

python3 ok -v

If you do not want to send your progress to our server or you have any problems logging in, add the --local flag to block all communication:

python3 ok --local

When you are ready to submit, run ok with the --submit option:

python3 ok --submit

Readings: You might find the following references useful:

Table of Contents

The Scheme interpreter is included in the starter ZIP archive. To run the Scheme interpreter, use the following command:

python3 scheme

To load a file (such as hw08.scm), use

python3 scheme -load hw08.scm

You can also use our online Scheme interpreter.

Question 1

Write the function deep-map, which takes a function fn and a list s that may contain numbers or other lists. It returns a list with identical structure to s, but replacing each non-list element by the result of applying fn on it, even for elements within sub-lists. Assume that the input has no dotted (malformed) lists.

(define (deep-map fn s)
  ; YOUR-CODE-HERE
  nil
)

Hint: You can use the predicate list? to check if a value is a list.

To see examples and test your implementation, run

python3 ok -u -q deep-map

Question 2

Write a procedure substitute that takes three arguments: a list s, an old word, and a new word. It returns a list with the elements of s, but with every occurrence of old replaced by new, even within sub-lists.

(define (substitute s old new)
  ; YOUR-CODE-HERE
  nil
)

To see examples and test your implementation, run

python3 ok -u -q substitute

Question 3

Write sub-all, which takes a list s, a list of old words, and a list of new words; the last two lists must be the same length. It returns a list with the elements of s, but with each word that occurs in the second argument replaced by the corresponding word of the third argument.

(define (sub-all s olds news)
  ; YOUR-CODE-HERE
  nil
)

To see examples and test your implementation, run

python3 ok -u -q sub-all