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## to Raindrops in the Crystal Track

Published at Jul 13 2018 · 1 comment
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".

## Setup

Follow the setup instructions for Crystal here:

http://exercism.io/languages/crystal

More help installing can be found here:

http://crystal-lang.org/docs/installation/index.html

## Making the Test Suit Pass

Execute the tests with:

``````\$ crystal spec
``````

In each test suite all but the first test have been skipped.

Once you get a test passing, you can unskip the next one by changing `pending` to `it`.

## 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_spec.cr

``````require "spec"
require "../src/*"

describe "Raindrops" do
describe "#drops" do
it "converts 1 to 1" do
Raindrops.drops(1).should eq "1"
end

pending "converts 3 to Pling" do
Raindrops.drops(3).should eq "Pling"
end

pending "converts 5 to Plang" do
Raindrops.drops(5).should eq "Plang"
end

pending "converts 7 to Plong" do
Raindrops.drops(7).should eq "Plong"
end

pending "converts 35 to PlangPlong" do
Raindrops.drops(35).should eq "PlangPlong"
end

pending "converts 52 to 52" do
Raindrops.drops(52).should eq "52"
end

pending "converts 105 to PlingPlangPlong" do
Raindrops.drops(105).should eq "PlingPlangPlong"
end
end
end``````
``````class Raindrops
def self.drops(number)
String.build do |output|
factors = { 3 => "Pling", 5 => "Plang", 7 => "Plong" }
factors.each do |factor, value|
case {number % factor}
when { 0 }
output << value
end
end
output  << number.to_s if output.empty?
end

end
end`````` 