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to Darts in the Ruby Track

Published at May 24 2020 · 0 comments
Instructions
Test suite
Solution

Write a method that returns the earned points in a single toss of a Darts game.

Darts is a game where players throw darts to a target.

In our particular instance of the game, the target rewards with 4 different amounts of points, depending on where the dart lands.

If the dart lands:

  • outside the target: 0 points.
  • in the outer circle of the target: 1 point.
  • in the middle circle of the target: 5 points.
  • in the inner circle of the target: 10 points.

The outer circle has a radius of 10 units (This is equivalent to the total radius for the entire target), the middle circle a radius of 5 units, and the inner circle a radius of 1. They are all centered to the same point (That is, the circles are concentric) defined by the coordinates (0, 0).

Write a method that, given a point in the target (defined by its real Cartesian coordinates x and y), returns the correct amount earned by a dart landing in that point.


For installation and learning resources, refer to the Ruby resources page.

For running the tests provided, you will need the Minitest gem. Open a terminal window and run the following command to install minitest:

gem install minitest

If you would like color output, you can require 'minitest/pride' in the test file, or note the alternative instruction, below, for running the test file.

Run the tests from the exercise directory using the following command:

ruby darts_test.rb

To include color from the command line:

ruby -r minitest/pride darts_test.rb

Source

Inspired by an exercise created by a professor Della Paolera in Argentina

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

darts_test.rb

require 'minitest/autorun'
require_relative 'darts'

# Common test data version: 2.2.0 f60c43b
class DartsTest < Minitest::Test
  def test_missed_target
    # skip
    darts = Darts.new(-9, 9)
    assert_equal(0, darts.score)
  end

  def test_on_the_outer_circle
    skip
    darts = Darts.new(0, 10)
    assert_equal(1, darts.score)
  end

  def test_on_the_middle_circle
    skip
    darts = Darts.new(-5, 0)
    assert_equal(5, darts.score)
  end

  def test_on_the_inner_circle
    skip
    darts = Darts.new(0, -1)
    assert_equal(10, darts.score)
  end

  def test_exactly_on_centre
    skip
    darts = Darts.new(0, 0)
    assert_equal(10, darts.score)
  end

  def test_near_the_centre
    skip
    darts = Darts.new(-0.1, -0.1)
    assert_equal(10, darts.score)
  end

  def test_just_within_the_inner_circle
    skip
    darts = Darts.new(0.7, 0.7)
    assert_equal(10, darts.score)
  end

  def test_just_outside_the_inner_circle
    skip
    darts = Darts.new(0.8, -0.8)
    assert_equal(5, darts.score)
  end

  def test_just_within_the_middle_circle
    skip
    darts = Darts.new(-3.5, 3.5)
    assert_equal(5, darts.score)
  end

  def test_just_outside_the_middle_circle
    skip
    darts = Darts.new(-3.6, -3.6)
    assert_equal(1, darts.score)
  end

  def test_just_within_the_outer_circle
    skip
    darts = Darts.new(-7.0, 7.0)
    assert_equal(1, darts.score)
  end

  def test_just_outside_the_outer_circle
    skip
    darts = Darts.new(7.1, -7.1)
    assert_equal(0, darts.score)
  end

  def test_asymmetric_position_between_the_inner_and_middle_circles
    skip
    darts = Darts.new(0.5, -4)
    assert_equal(5, darts.score)
  end
end
class Darts
  CIRCLE_TO_RANGE = {
    inner:  0.0..1.4,
    middle: 1.4..7.0,
    outer:  7.0..14.0
  }.freeze

  POINTS = {
    inner:  10,
    middle: 5,
    outer:  1
  }.freeze

  def initialize(*coordinates)
    @position = coordinates.map(&:abs).sum
  end

  def score
    case @position
    when CIRCLE_TO_RANGE[:inner]  then POINTS[:inner]
    when CIRCLE_TO_RANGE[:middle] then POINTS[:middle]
    when CIRCLE_TO_RANGE[:outer]  then POINTS[:outer]
    else 0
    end
  end
end

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