darts: Port Darts Exercise (#1019)

* darts: Port Darts Exercise

* add entry to config.json

* Make solution Ruby 2.5 friendly

Co-Authored-By: Victor Goff <[email protected]>

* Improve wording in Darts README

Co-authored-by: Victor Goff <[email protected]>

config.json

@@ -1222,6 +1222,17 @@
       "topics": [
         "loops"
       ]
+    },
+    {
+      "slug": "darts",
+      "uuid": "15b73808-78a4-4854-b7cf-82a478107024",
+      "core": false,
+      "unlocked_by": null,
+      "difficulty": 3,
+      "topics": [
+        "math",
+        "geometry"
+      ]
     }
   ]
 }

exercises/darts/.meta/generator/darts_case.rb

@@ -0,0 +1,10 @@
+require 'generator/exercise_case'
+
+class DartsCase < Generator::ExerciseCase
+  def workload
+    [
+      "darts = Darts.new(#{input["x"]}, #{input["y"]})\n",
+      "assert_equal(#{expected.inspect}, darts.score)\n"
+    ].join
+  end
+end

exercises/darts/.meta/solutions/darts.rb

@@ -0,0 +1,29 @@
+class Darts
+  attr_reader :x, :y
+
+  def initialize(x, y)
+    @x = x
+    @y = y
+  end
+
+  def score
+    scores.detect do |range, _|
+      range.cover? distance_to_bullseye
+    end[1]
+  end
+
+  private
+
+  def scores
+    {
+      0.0..1.0 => 10,
+      1.0..5.0 => 5,
+      5.0..10.0 => 1,
+      10.0..1.0/0 => 0,
+    }
+  end
+
+  def distance_to_bullseye
+    Math.sqrt(x * x + y * y)
+  end
+end

exercises/darts/README.md

@@ -0,0 +1,48 @@
+# Darts
+
+Write a method that returns the earned points in a single toss of a Darts game.
+
+[Darts](https://en.wikipedia.org/wiki/Darts) is a game where players
+throw darts to a [target](https://en.wikipedia.org/wiki/Darts#/media/File:Darts_in_a_dartboard.jpg).
+
+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](http://mathworld.wolfram.com/ConcentricCircles.html)) 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](http://exercism.io/languages/ruby/resources).
+
+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.

exercises/darts/darts_test.rb

@@ -0,0 +1,83 @@
+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