Rock Paper Scissors Pattern Matching

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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Rock Paper Scissors Using Pattern Matching

You’re going to recreate/refactor your rock paper scissors game using pattern matching.

RockPaperScissors.play(:rock, :paper)
"paper beats rock!"

RockPaperScissors.play(:rock, :rock)
"draw!"

Example Solution

Using multiple function clauses.

defmodule RockPaperScissorsPatternMatching do
  def play(:rock, :scissors), do: "rock beats scissors!"
  def play(:paper, :rock), do: "paper beats rock!"
  def play(:scissors, :paper), do: "scissors beats paper!"
  def play(:rock, :paper), do: "paper beats rock!"
  def play(:paper, :scissors), do: "scissors beats paper!"
  def play(:scissors, :rock), do: "rock beats scissors!"
  def play(_same, _same), do: "draw!"
end

Here’s how we might accomplish the same thing using case.

defmodule RockPaperScissorsPatternMatching do
  def play(guess1, guess2) do
    case {guess1, guess2} do
      {:rock, :scissors} -> "rock beats scissors!"
      {:paper, :rock} -> "paper beats rock!"
      {:scissors, :paper} -> "scissors beats paper!"
      {:rock, :paper} -> "paper beats rock!"
      {:paper, :scissors} -> "scissors beats paper!"
      {:scissors, :rock} -> "rock beats scissors!"
      {_same, _same} -> "draw!"
    end
  end
end

Implement the RockPaperScissorsPatternMatching module as documented below.

defmodule RockPaperScissorsPatternMatching do
  @moduledoc """
  Documentation for `RockPaperScissorsPatternMatching`
  """

  @doc """
  Play rock paper scissors. Returns a string to describe who won the game.

  ## Examples

    iex> RockPaperScissorsPatternMatching.play(:rock, :scissors)
    "rock beats scissors!"

    iex> RockPaperScissorsPatternMatching.play(:paper, :rock)
    "paper beats rock!"

    iex> RockPaperScissorsPatternMatching.play(:scissors, :paper)
    "scissors beats paper!"

    iex> RockPaperScissorsPatternMatching.play(:rock, :paper)
    "paper beats rock!"

    iex> RockPaperScissorsPatternMatching.play(:paper, :scissors)
    "scissors beats paper!"

    iex> RockPaperScissorsPatternMatching.play(:scissors, :rock)
    "rock beats scissors!"

    iex> RockPaperScissorsPatternMatching.play(:rock, :rock)
    "draw!"

    iex> RockPaperScissorsPatternMatching.play(:paper, :paper)
    "draw!"

    iex> RockPaperScissorsPatternMatching.play(:scissors, :scissors)
    "draw!"
  """
  def play(guess1, guess2) do
  end
end

Mark As Completed

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

save_name =
  case Path.basename(__DIR__) do
    "reading" -> "rps_pattern_matching_reading"
    "exercises" -> "rps_pattern_matching_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 rps-pattern-matching-exercise
$ git add .
$ git commit -m "finish rps pattern matching exercise"
$ git push origin rps-pattern-matching-exercise

Create a pull request from your rps-pattern-matching-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.

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