Published at Jul 13 2018
·
1 comment

Instructions

Test suite

Solution

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.

- 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 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 raindrops_test.rb
```

To include color from the command line:

```
ruby -r minitest/pride raindrops_test.rb
```

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

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

```
require 'minitest/autorun'
require_relative 'raindrops'
# Common test data version: 1.1.0 99de15d
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
end
```

```
class Raindrops
def self.convert(num)
output = NOISES.map { |factor, noise| noise if num % factor == 0 }
# trick: nils (from above) are falsey, and "arr.any?" means
# "arr.any? { |elt| elt.truthy? }", NOT "arr.size > 0"!
return output.any? ? output.join : num.to_s
end
private
NOISES = { 3 => "Pling", 5 => "Plang", 7 => "Plong" }
end
```

A huge amount can be learned 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 you could read more about to improve your understanding?

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## Community comments

One tradeoff was the use of a NOISES hash rather than repeating an "if" statement. I chose the hash (could have used an array of two-element arrays, whatever) as that would make the actual processing much clearer, and enable it to be expanded to cover more numbers and noises with less addition than the "if" approach. Such additions would also be in the private section, out of the way of those looking at the public stuff, which is more likely to be looked at.

What drove me in this direction is the natural progression from the initial smartass answer of just returning "1" unless the number was a multiple of one of the noise numbers, then came the possibility of having to return multiple noises strung together, and finally a different number than 1, capped off by the refactoring mentioned above in Tradeoffs. That was so far down the list that I thought perhaps it would not get around to changing the non-noised number, and I was going to comment on that here!