Lab 10 - Fall 2019

Introducing lambda

Start on lab 10

1. Create a new directory for this lab in your cs101 directory by entering the following at the Linux prompt:
   1. cd
   2. cd cs101
   3. mkdir lab10
   4. cd lab10
2. Launch DrRacket.
3. From the Language menu along DrRacket's menu bar, select Choose Language…. In the left column, make sure the arrow head to the left of How to Design Programs is pointing downwards. If the arrow is not pointing downwards, click on it. This will cause a list of language levels to appear. Click on Intermediate Student with lambda. Select the OK button at the bottom right to save this selection.

Now you are ready to begin our final lab! Remember that you will need to change the language on DrRacket on your own computer, too.

Your first lambda programs

1. Use build-list and lambda to define the following four functions that, respectively:
   1. creates the list (list 0 … (- n 1)) for any natural number n;
   2. creates the list (list 1 … n) for any natural number n;
   3. creates the list (list 1 1/2 … 1/n) for any natural number n;
   4. creates the list of the first n even numbers;
2. Recall that the append function in ISL concatenates the items of two lists or, equivalently, replaces '() at the end of the first list with the second list:

(check-expect (append (list 1 2 3) (list 4 5 6 7 8))

              (list 1 2 3 4 5 6 7 8)) 

1. Use foldr to define append-from-fold.
2. The foldr function is so powerful that you can define almost any list-processing functions with it. Use foldr to define map-via-fold, which simulates map.

You may have one week to finish this lab.

Submitting your work

You may have one week to finish this lab. Submit on Moodle when you are finished.

Log out

When you are done, remember to log out.