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SergiiVlasiuk's solution

to Darts in the Scala Track

Published at Aug 18 2019 · 0 comments
Instructions
Test suite
Solution

Write a function 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, player earns no points (0 points).
  • If the dart lands in the outer circle of the target, player earns 1 point.
  • If the dart lands in the middle circle of the target, player earns 5 points.
  • If the dart lands in the inner circle of the target, player earns 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. Of course, they are all centered to the same point (That is, the circles are concentric) defined by the coordinates (0, 0).

Write a function 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. The Scala exercises assume an SBT project scheme. The exercise solution source should be placed within the exercise directory/src/main/scala. The exercise unit tests can be found within the exercise directory/src/test/scala.

To run the tests simply run the command sbt test in the exercise directory.

For more detailed info about the Scala track see the help page.

Source

Inspired by an excersie 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.

DartsTest.scala

import org.scalatest.{Matchers, FunSuite}

/** @version 1.0.0 */
class DartsTest extends FunSuite with Matchers {

  test("A dart lands outside the target") {
    Darts.score(15.3, 13.2) should be (0)
  }

  test("A dart lands just in the border of the target") {
    pending
    Darts.score(10, 0) should be (1)
  }

  test("A dart lands in the middle circle") {
    pending
    Darts.score(3, 3.7) should be (5)
  }

  test("A dart lands right in the border between outside and middle circles") {
    pending
    Darts.score(0, 5) should be (5)
  }

  test("A dart lands in the inner circle") {
    pending
    Darts.score(0, 0) should be (10)
  }
}
object Darts {
  def score(x: Double, y: Double): Int = math.hypot(x, y) match {
    case res if res <= 1 => 10
    case res if res <= 5 => 5
    case res if res <= 10 => 1
    case _ => 0
  }
}

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