pgaspar's solution to Raindrops on the Ruby track

Instructions

Test suite

Solution

Note:

This solution was written on an old version of Exercism. The tests below might not correspond to the solution code, and the exercise may have changed since this code was written.

Convert a number to a string, the contents of which depend on the number's factors.

If the number has 3 as a factor, output 'Pling'.
If the number has 5 as a factor, output 'Plang'.
If the number has 7 as a factor, output 'Plong'.
If the number does not have 3, 5, or 7 as a factor, just pass the number's digits straight through.

Examples

28's factors are 1, 2, 4, 7, 14, 28.
- In raindrop-speak, this would be a simple "Plong".
30's factors are 1, 2, 3, 5, 6, 10, 15, 30.
- In raindrop-speak, this would be a "PlingPlang".
34 has four factors: 1, 2, 17, and 34.
- In raindrop-speak, this would be "34".

For installation and learning resources, refer to the exercism help 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 raindrops_test.rb

To include color from the command line:

ruby -r minitest/pride raindrops_test.rb

Source

A variation on a famous interview question intended to weed out potential candidates. http://jumpstartlab.com

Submitting Incomplete Solutions

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

raindrops_test.rb

require 'minitest/autorun'
require_relative 'raindrops'

# Common test data version: 1.0.0 9db5371
class RaindropsTest < Minitest::Test
  def test_the_sound_for_1_is_1
    # skip
    assert_equal "1", Raindrops.convert(1)
  end

  def test_the_sound_for_3_is_pling
    skip
    assert_equal "Pling", Raindrops.convert(3)
  end

  def test_the_sound_for_5_is_plang
    skip
    assert_equal "Plang", Raindrops.convert(5)
  end

  def test_the_sound_for_7_is_plong
    skip
    assert_equal "Plong", Raindrops.convert(7)
  end

  def test_the_sound_for_6_is_pling_as_it_has_a_factor_3
    skip
    assert_equal "Pling", Raindrops.convert(6)
  end

  def test_2_to_the_power_3_does_not_make_a_raindrop_sound_as_3_is_the_exponent_not_the_base
    skip
    assert_equal "8", Raindrops.convert(8)
  end

  def test_the_sound_for_9_is_pling_as_it_has_a_factor_3
    skip
    assert_equal "Pling", Raindrops.convert(9)
  end

  def test_the_sound_for_10_is_plang_as_it_has_a_factor_5
    skip
    assert_equal "Plang", Raindrops.convert(10)
  end

  def test_the_sound_for_14_is_plong_as_it_has_a_factor_of_7
    skip
    assert_equal "Plong", Raindrops.convert(14)
  end

  def test_the_sound_for_15_is_plingplang_as_it_has_factors_3_and_5
    skip
    assert_equal "PlingPlang", Raindrops.convert(15)
  end

  def test_the_sound_for_21_is_plingplong_as_it_has_factors_3_and_7
    skip
    assert_equal "PlingPlong", Raindrops.convert(21)
  end

  def test_the_sound_for_25_is_plang_as_it_has_a_factor_5
    skip
    assert_equal "Plang", Raindrops.convert(25)
  end

  def test_the_sound_for_27_is_pling_as_it_has_a_factor_3
    skip
    assert_equal "Pling", Raindrops.convert(27)
  end

  def test_the_sound_for_35_is_plangplong_as_it_has_factors_5_and_7
    skip
    assert_equal "PlangPlong", Raindrops.convert(35)
  end

  def test_the_sound_for_49_is_plong_as_it_has_a_factor_7
    skip
    assert_equal "Plong", Raindrops.convert(49)
  end

  def test_the_sound_for_52_is_52
    skip
    assert_equal "52", Raindrops.convert(52)
  end

  def test_the_sound_for_105_is_plingplangplong_as_it_has_factors_3_5_and_7
    skip
    assert_equal "PlingPlangPlong", Raindrops.convert(105)
  end

  def test_the_sound_for_3125_is_plang_as_it_has_a_factor_5
    skip
    assert_equal "Plang", Raindrops.convert(3125)
  end

  # Problems in exercism evolve over time, as we find better ways to ask
  # questions.
  # The version number refers to the version of the problem you solved,
  # not your solution.
  #
  # Define a constant named VERSION inside of the top level BookKeeping
  # module, which may be placed near the end of your file.
  #
  # In your file, it will look like this:
  #
  # module BookKeeping
  #   VERSION = 1 # Where the version number matches the one in the test.
  # end
  #
  # If you are curious, read more about constants on RubyDoc:
  # http://ruby-doc.org/docs/ruby-doc-bundle/UsersGuide/rg/constants.html

  def test_bookkeeping
    skip
    assert_equal 3, BookKeeping::VERSION
  end
end

class Raindrops
  FACTORS = {
    3 => 'Pling',
    5 => 'Plang',
    7 => 'Plong'
  }

  def self.convert(number)
    output = apply_factors_to(number)
    output.empty? ? number.to_s : output
  end

  class << self
    private

    def apply_factors_to(number)
      FACTORS.select { |factor, _| factor_of?(number, factor) }.values.join
    end

    def factor_of?(number, factor)
      (number % factor).zero?
    end
  end
end

module BookKeeping
  VERSION = 3
end

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pgaspar's solution

to Raindrops in the Ruby Track