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pgaspar's solution

to Space Age in the Ruby Track

Published at Feb 11 2019 · 0 comments
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
  BASE_ORBITAL_PERIOD = 31_557_600

  ORBITAL_PERIOD_RATIOS = {
    earth: 1.0,
    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

  ORBITAL_PERIOD_RATIOS.each do |planet, ratio|
    define_method("on_#{planet}") do
      planet_period = BASE_ORBITAL_PERIOD * ratio
      @seconds / planet_period
    end
  end
end

module BookKeeping
  VERSION = 1
end

Community comments

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pgaspar's Reflection

Meta programming isn't super readable, but I thought this was a nice opportunity to do a bit of it. Let me know what you think and if you have suggestions on how to improve the looks of it! 😊