Fun Formulas

Mix.install([
  {:jason, "~> 1.4"},
  {:kino, "~> 0.8.0", override: true},
  {:youtube, github: "brooklinjazz/youtube"},
  {:hidden_cell, github: "brooklinjazz/hidden_cell"}
])

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Setup

Ensure you type the ea keyboard shortcut to evaluate all Elixir cells before starting. Alternatively you can evaluate the Elixir cells as you read.

Fun Formulas

As developers, it’s our job to translate business requirements into something that the computer understands.

These exercises will have you convert a common formula into an Elixir program.

Loading Bar Percentage

We often need to display loading bars to the user. Loading bars use the current percentage they have finished loading in order to display the loading progress.

You can calculate the percentage with $\frac{actual\ value}{total\ value}\times100$

For example if we complete 7 out of 10 items, we would be 70.0% complete.

7 / 10 # 70.0

Use arithmetic operators to determine the percentage given we have completed 12 out of 42 items.

Example solution

actual = 12
total = 42

actual / total

Enter your solution below.

Rocket Ship

We’re building a rocket ship app to teach people about physics.

Users can enter the mass and acceleration of a ship to visualize the force generated.

Given that ${mass} * {acceleration} = force$, calculate the force when mass is 10 and acceleration is 50.

Example solution

mass = 10
acceleration = 50

mass * acceleration

Enter your solution below.

What Do You Tip?

It’s common in many cultures to leave a tip whenever you buy a meal. It’s common to calculate the tip as a percentage of the meal.

Given the initial cost of a meal is 20, and you want to leave a 15% tip, use arithmetic operators to determine the total cost of the meal.

Example solution

initial_cost = 20
tip_percent = 1.15

initial_cost * tip_percent

Enter your solution below.

Pythagorean Theorum

To calculate the longest side of a triangle we use $a^2 + b^2 = c^2$

Given a triangle where side $a$ is 4, and side $b$ is 10, calculate $c^2$

Example solution

a = 4
b = 10

a ** 2 + b ** 2

Enter your solution below.

Bonus: Square Root

Earlier we calculated $c^2$ for pythagoream theorum. Given $c^2$ is 116 determine the square root of $c^2$ to calculate $c$.

Example solution

c_squared = 116
:math.sqrt(c_squared)

Enter your solution below.

Mark As Completed

file_name = Path.basename(Regex.replace(~r/#.+/, __ENV__.file, ""), ".livemd")

save_name =
  case Path.basename(__DIR__) do
    "reading" -> "fun_formulas_reading"
    "exercises" -> "fun_formulas_exercise"
  end

progress_path = __DIR__ <> "/../progress.json"
existing_progress = File.read!(progress_path) |> Jason.decode!()

default = Map.get(existing_progress, save_name, false)

form =
  Kino.Control.form(
    [
      completed: input = Kino.Input.checkbox("Mark As Completed", default: default)
    ],
    report_changes: true
  )

Task.async(fn ->
  for %{data: %{completed: completed}} <- Kino.Control.stream(form) do
    File.write!(
      progress_path,
      Jason.encode!(Map.put(existing_progress, save_name, completed), pretty: true)
    )
  end
end)

form

Commit Your Progress

Run the following in your command line from the curriculum folder to track and save your progress in a Git commit. Ensure that you do not already have undesired or unrelated changes by running git status or by checking the source control tab in Visual Studio Code.

$ git checkout -b fun-formulas-exercise
$ git add .
$ git commit -m "finish fun formulas exercise"
$ git push origin fun-formulas-exercise

Create a pull request from your fun-formulas-exercise branch to your solutions branch. Please do not create a pull request to the DockYard Academy repository as this will spam our PR tracker.

DockYard Academy Students Only:

Notify your teacher by including @BrooklinJazz in your PR description to get feedback. You (or your teacher) may merge your PR into your solutions branch after review.

If you are interested in joining the next academy cohort, sign up here to receive more news when it is available.

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