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PatrickMcSweeny's solution

to Space Age in the Ruby Track

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Instructions
Test suite
Solution

Given an age in seconds, calculate how old someone would be on:

  • Earth: orbital period 365.25 Earth days, or 31557600 seconds
  • Mercury: orbital period 0.2408467 Earth years
  • Venus: orbital period 0.61519726 Earth years
  • Mars: orbital period 1.8808158 Earth years
  • Jupiter: orbital period 11.862615 Earth years
  • Saturn: orbital period 29.447498 Earth years
  • Uranus: orbital period 84.016846 Earth years
  • Neptune: orbital period 164.79132 Earth years

So if you were told someone were 1,000,000,000 seconds old, you should be able to say that they're 31.69 Earth-years old.

If you're wondering why Pluto didn't make the cut, go watch this youtube video.


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 space_age_test.rb

To include color from the command line:

ruby -r minitest/pride space_age_test.rb

Source

Partially inspired by Chapter 1 in Chris Pine's online Learn to Program tutorial. http://pine.fm/LearnToProgram/?Chapter=01

Submitting Incomplete Solutions

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

space_age_test.rb

require 'minitest/autorun'
require_relative 'space_age'

# Common test data version: 1.1.0 8d4df79
class SpaceAgeTest < Minitest::Test
  # assert_in_delta will pass if the difference
  # between the values being compared is less
  # than the allowed delta
  DELTA = 0.01

  def test_age_on_earth
    # skip
    age = SpaceAge.new(1_000_000_000)
    assert_in_delta 31.69, age.on_earth, DELTA
  end

  def test_age_on_mercury
    skip
    age = SpaceAge.new(2_134_835_688)
    assert_in_delta 280.88, age.on_mercury, DELTA
  end

  def test_age_on_venus
    skip
    age = SpaceAge.new(189_839_836)
    assert_in_delta 9.78, age.on_venus, DELTA
  end

  def test_age_on_mars
    skip
    age = SpaceAge.new(2_329_871_239)
    assert_in_delta 39.25, age.on_mars, DELTA
  end

  def test_age_on_jupiter
    skip
    age = SpaceAge.new(901_876_382)
    assert_in_delta 2.41, age.on_jupiter, DELTA
  end

  def test_age_on_saturn
    skip
    age = SpaceAge.new(3_000_000_000)
    assert_in_delta 3.23, age.on_saturn, DELTA
  end

  def test_age_on_uranus
    skip
    age = SpaceAge.new(3_210_123_456)
    assert_in_delta 1.21, age.on_uranus, DELTA
  end

  def test_age_on_neptune
    skip
    age = SpaceAge.new(8_210_123_456)
    assert_in_delta 1.58, age.on_neptune, DELTA
  end
end
class SpaceAge
  ORBITAL_PERIODS = {
    mercury: 0.2408467,
    venus: 0.61519726,
    mars: 1.8808158,
    jupiter: 11.862615,
    saturn: 29.447498,
    uranus: 84.016846,
    neptune: 164.79132
  }.freeze

  def initialize(seconds)
    @seconds = seconds
  end

  def on_earth
    seconds / 31_557_600.to_f
  end

  ORBITAL_PERIODS.keys.each do |planet|
    define_method("on_#{planet}") do
      on_earth / ORBITAL_PERIODS[planet]
    end
  end

  private

  attr_reader :seconds
end

What can you learn from this solution?

A huge amount can be learnt from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

  • What compromises have been made?
  • Are there new concepts here that I could read more about to develop my understanding?