raindrops.rb

# Raindrops

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".

* * * *

Solution:

module Raindrops
  SOUNDS={ 3 => 'Pling',
           5 => 'Plang',
           7 => 'Plong'}

  def self.convert(drop_count)
    make_sounds(drop_count)
  end

  def self.make_sounds(drop_count)
    total_sounds = SOUNDS.map do |num, sound|
      sound if (drop_count % num).zero?
    end.compact.join
    total_sounds.empty? ? drop_count.to_s : total_sounds
  end
end

* * * *

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