21. Worksheet C

You are going to create a new struct np that remembers both a number and a posn.

1. Data definition: write a human-understandable description for np.

2. Write the Racket code to define the np structure.

3. Write two check-expect to verify that you get out the same information that you put in to the structure.

4. Design and test np-set-num: np(old) number -> np(new) that sets the number in a given number-position structure.

5. Design and test np-set-posn: np(old) posn -> np(new) that makes the posn of the np into the given posn.

6. Go do Exercise 21.6.3 using the idea from this worksheet.