Please send me all your Racket files as e-mail attachments. My e-mail is elenam at morris.umn.edu. The subject of your e-mail must be "1301 Problem set 4" followed by your initials or name.
Exercise 108.
Exercise 115 at the end of section 6.5. Please read the entire section. For the exercise start with check-error to specify what message you would like to get for calls such as (light=? "red" "purple"). It should be something like: "traffic light expected as second argument, given: purple".
Note that if both values passed to the function are not valid traffic light colors then only the first one of them will be listed in the error message, and that's fine.