Work 05: Contractors

Due: Wednesday 09/18 10:00am

Submission name: work05.rkt

Function Contracts

A function contract is a way to document a function within your code. Contracts contain the following information:

• Template function call using variables.
• The type of value to be returned by the function.
• The type of value represented by each parameter.
• A description of what the function does.
• One (or more) samples with input values and expected outputs.

Sample contract:

; (hypot a b) --> number
;  a : number
;  b : number
;  Returns the lenght of the hypotenuse of a right traingle with legs of length a and b.
;  (hypot 3 4) --> 5

Write the Following Functions given the contracts.

Paste the contracts into your racket program when starting. Use define and lambda to write your functions. Include test cases with descriptive output.

; (perimFromArea a) --> number
;   a : number
;   Returns the perimeter of that square whose area is a
;   (perimFromArea 25) --> 20
;   (perimFromArea 10) --> 12.649110640673518

; (f_to_c temp) --> number
;   temp : number
;   Returns temp converted from farenheit to celsius
;   (f_to_c 212) --> 100

Tip: \(C = (F-32)\dfrac{5}{9}\)

Write contracts and the functions for the following:

cost

• Returns the cost of a ticket to the Totally Real Not Made Up Amazing Museum of Racket Exercises.
• The cost of admission depends on a base amount and a discount rate.
• Cost is calculated by: base + base * rate.
• Write the function (cost base rate) that will return the cost using the formula above.
• Example:
  • (cost 10 0.25) ==> 12.5

groupCost

• Returns the total cost of the tickets for a school trip to the Totally Real Not Made Up Amazing Museum of Racket Exercises
• The base cost for students is $5, and the discount rate is 0.5.
• The base cost for teachers is $10, and the discount rate is 0.75.
• The base cost for other adults is $10, and the discount rate is 1.
• Write the function (groupCost students teachers adults) that returns the total cost of the tickets given the amounts provided as parameters, using the cost formula.
• Example:
  • (groupCost 34 2 2) ==> 330.0

Submitting your work using GitHub Classroom:

1. Join the GitHub classroom assignment via the correct link:
   • Period 9: https://classroom.github.com/a/pQDHKUhf
   • Period 10: https://classroom.github.com/a/L22rWK5Q
2. After following that link, click “Accept this assignment”
3. After ~1 minute (maybe less), refresh the page.
4. You should see a link that looks something like: https://github.com/stuycs-gh-classrooms/09-fcs-dw-work-jonalf
   • The end of that url will differ based on your GitHub username and the beginning by your class period. Click on that url.
   • This is where you will submit all your work, bookmark this page.
   • This will create a GitHub repository for you, and add a basic README.md file to it.
5. You will be taken to the repository page for your work. You will see the contents of README.md, which should display: “Work For NeXtCS” and then “Name: YOUR NAME HERE”.
6. Edit README.md by clicking on the pencil icon found to the far right of README.md
   • Replace “YOUR NAME HERE” with your full name, first then last (use preferred name if you’d like).
7. Find the “Commit changes” button and click it.
8. When you’ve finished the homework, use the “Add File -> Upload Files” button to upload your work03.rkt file.

Important Notes:

• Use the submission name listed above as the file name for your work.
• Make sure you are using the definitions pane to write your programs, and that you are saving that area when submitting.
• Use the interactions pane to test your code, but you do not submit what is there.
• The CS Dojo starts today! If you want to get a leg up, stop by 307 from 3:45 - 5!
• If you are having difficulty getting DrRacket to work on your computer, you can use this online editor:
  • https://www.wescheme.org/openEditor

Work Task:

• Read chapter 4 of the online textbook.
• Take the 3 formulas from the previous assignment, and make the functions using lambda and define.
• If done correctly, this code should work (as long as you named the functions the same as I did):  

    (triArea 12 5)
    (celToFaran 100)
    (gravity 27 2 3)