ITEC 380 2017fall ibarland

home—lectures—recipe—exams—hws—D2L—breeze (snow day; distance)

union-types
working with a union type
hw03b

Due: Sep.25 (Mon) 15:00 (hardcopy and D2L)
(but try to have it mostly-completed by Friday evening)
Your submitted file should be named “hw03.rkt”.
Note: There are also some D2L questions under a quiz named “hw03a”.

We wish to write code about whether or not the Radford Highlanders won their soccer game, this last weekend. We want to capture whether: they won/lost, or tied, or there wasn't any game this weekend, or (if the game is still in-progress) what the name of the team currently being played is.

1. (5pts) Complete steps 1-3 of the-design-recipe—the design recipe: final version for representing this information, which we'll name “game-result”.

   Hint: To represent whether they won or lost, a boolean seems appropriate. What types seem appropriate for each of the other variants?

2. (5pts) Write a function payout which takes in the amount of a bet¹ placed that the Highlanders’ would win their game (non-negative) and a game-result and returns how much money is to be repaid:
   • If the Highlanders win, twice the money is repaid, minus a 10% house cut.
   • If the Highlanders lose, $0 is repaid.
   • If the Highlanders are still playing, nothing ($0) is repaid (yet).
   • If the Highlanders tie, the amount of the bet is repaid, minus a 10% house cut.
   • If the Highlanders didn't play, then the amount of the bet is fully refunded.
3. (5pts) Write a function game-result->string which returns a user-friendly message similar to one of the following, as appropriate:
   • "The Radford Highlanders won!" (or, “lost :-(”)
   • "The Radford Highlanders tied their last game."
   • "The Radford Highlanders are still playing The Wytheville Wallabies."

     Hint: Of course, it is not “as appropriate” to return a string mentioning the Wytheville Wallabies when we're actually playing the Dublin Dingoes, or the Pulaski Pangolins! Recall from our data-definition in #1, a game-result should capable of representing, among other things, the name of a team (which therefore means that the game must be in-progress). (Moreover, this means your function does not need to be given any additional information, since the game-result already represents the info you need.)

   • "The Radford Highlanders did not play this week."
   (You will, of course, follow the applicable steps 4,5,7,8 of the-design-recipe—the design recipe: final version.)

Standard instructions for all homeworks (unless instructed otherwise):

• Your name, the assignment-number, and the URL of this assignment must be in a comment at the start of the file.
• Test cases may be worth half the points or perhaps even more. Don't comment-out tests cases that don't pass (unless they cause an error, preventing the rest of the program from running).
• Any code which results in syntax errors will generally not earn more than 50% of the points-possible. For grading, I will ignore any commented-out code.
• Format well (in particular, each open-paren should be preceded by a space²).

home—lectures—recipe—exams—hws—D2L—breeze (snow day; distance)

©2017, Ian Barland, Radford University Last modified 2017.Sep.23 (Sat)

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