Class 21 Objectives

At the end of today's class you should

KNOW:

That map can be used when you need to run some function on every element of a list
That map produces a list with the same number of elements as the original list
That map provides a compact way to write certain functions over lists
Which problems can be solved using map and filter, and which cannot

BE ABLE TO:

Use map to write functions over lists.

Sample Exam Question:

A database of college students staying in residence halls is made up of a list of structs with the following format:

;; Student is a (make-student String Symbol Number String)
(define-struct student(name gender age id))

The college has changed their student-id system, and now all ids must start with the characters "00". Using map, write a function update-ids that consumes a ListOfStudent and produces a ListOfStudent, where the id of each student in the list now has the prefix "00".

(DrRacket has a built-in function called string-append that might be useful. string-append consumes two strings and produces the string obtained by appending the second string to the first.)