CS 1101 - Aterm 12

Homework 3 - Unions and Simple List Processing

Due: Tuesday, September 11 at 5pm

Assignment Goals

• To make sure you can define unions and write programs over unions
• To make sure you can define simple lists and write programs over lists

The Assignment

Writing Data Definitions for Unions

A storm can be any one of the following:

• hurricane Information required for a hurricane consists of the name of the hurricane, the category (a number between 1 and 5, inclusive), the maximum sustained winds in miles per hour, the velocity of the storm in miles per hour, and the storm's heading (for example, NNW).
• tornado The information required for a tornado consists of the latitude and longitude of the location where the tornado touched down, the severity of the tornado (using the Fujita index), the velocity of the tornado, and its heading. The possible values for the Fujita index are F0, F1, F2, F3, F4, and F5. The latitude and longitude can be represented in this assignment as whole numbers (0 - 90 for latitude, 0 - 180 for longitude) followed by a designation of north or south, east or west (so, for example, Worcester is at 42 N, 71 W).
• thunderstorm The definition of a thunderstorm consists of the number of inches of rainfall, the maximum wind gust in miles per hour, the velocity of the storm in miles per hour, and its heading.

Writing Programs for Unions

1. Develop a data definition for each type of storm described above, and one for storms in general. Provide at least one example for each kind of storm.

2. Provide the template for each data definition you made in Problem 1.

3. Write a function fast-moving-storm? that consumes a storm and produces a boolean. The function returns true if the velocity of the storm exceeds 30 mph, otherwise it returns false.

4. Write a function warning that consumes a storm and produces a string. The string that is produced is as follows:
   • "stay inside" if the storm is a thunderstorm with maximum wind gusts less than or equal to 30 mph
   • "seek shelter" if the storm is a thunderstorm with maximum wind gusts in excess of 30 mph, if the storm is a tornado, or if the storm is a hurricane of category 1, 2, or 3
   • "evacuate" if the storm is a hurricane of category 4 or 5

5. Write a function upgrade-category that consumes a storm and produces a storm. The storm is returned unchanged if the given storm is a thunderstorm, a tornado of severity F5, or a hurricane of category 5. Otherwise, the storm that's produced is a storm the same as the original, except that the severity or category of the new storm is at the next higher level.

Writing Programs for Simple Lists

6. Write the data definition for a list-of-string. Provide examples of list-of-string.

7. Write the template for functions over a list-of-string

8. Write a function character-count that consumes a list-of-string and counts the total number of characters in all strings in the list.

9. Write a function all-alphabetic? that consumes a list-of-string and produces true if all characters in all strings in the list are alphabetic characters. Otherwise, the function produces false. (Hint: check the DrRacket help desk for the function string-alphabetic?)

What to Turn In

Using web-based turnin, turn in a single file containing all code and documentation for this assignment. Name your file according to the naming conventions for files. Make sure both partners' names and login names appear at the top of the file in a comment.