ITEC380 working with a union type

working with a union type
hw03

Due: Sep.21 (Fri) 15:00 (hardcopy and D2L)
Your submitted file should be named “hw03.rkt”.

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. (Oddly, we will not track the opposing team's name when the game isn't in progress ¹. Perhaps we don't care about such details once a game is over?)

(5pts) Complete steps 1-3 of the design recipe 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?

(5pts) Write a function payout which takes in the amount of a bet ² 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.

(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.)

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 space ³).

¹ Certainly it is natural to want to always know the opposing-team-name even for the other situations (won/lost, tied, etc.). But since we haven't yet introduced compound types (“structs”/“records”/“objects”), we don't know how to do this. So: Don't. Only keep track of the opposing-team-name in the event of game-in-progress.

(And on further thought, we'll also note that while opposing-team-name could conceivably be information worth tracking for several cases, it wouldn't make sense for no-game-this-week. This complicates a correct data-representation; more on that in class.)

↩

² A perfectly perfecty legal bet on a game of skill, with no luck involved whatsoever. ↩

³ The only exception to open-paren-preceded-by-space (or, at the start of a line) is any “[(”s occuring in a cond. Though we'll have a few other exceptions in the future: let* expressions, and (very occasionally) when calling higher-order functions. ↩

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working with a union type hw03

working with a union type
hw03