If you want to build something using a Raspberry Pi, you'll probably use resistors. For this exercise, you need to know only three things about them:
Black - Brown - Red - Orange - Yellow - Green - Blue - Violet - Grey - White
In resistor-color duo
you decoded the first two colors. For instance: orange-orange got the main value 33
.
The third color stands for how many zeros need to be added to the main value. The main value plus the zeros gives us a value in ohms.
For the exercise it doesn't matter what ohms really are.
For example:
(If Math is your thing, you may want to think of the zeros as exponents of 10. If Math is not your thing, go with the zeros. It really is the same thing, just in plain English instead of Math lingo.)
This exercise is about translating the colors into a label:
"... ohms"
So an input of "orange", "orange", "black"
should return:
"33 ohms"
When we get more than a thousand ohms, we say "kiloohms". That's similar to saying "kilometer" for 1000 meters, and "kilograms" for 1000 grams.
So an input of "orange", "orange", "orange"
should return:
"33 kiloohms"
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 resistor_color_trio_test.rb
To include color from the command line:
ruby -r minitest/pride resistor_color_trio_test.rb
Maud de Vries, Erik Schierboom https://github.com/exercism/problem-specifications/issues/1549
It's possible to submit an incomplete solution so you can see how others have completed the exercise.
require 'minitest/autorun'
require_relative 'resistor_color_trio'
# Common test data version: 1.1.0 2c41a51
class ResistorColorTrioTest < Minitest::Test
def test_orange_and_orange_and_black
# skip
assert_equal "Resistor value: 33 ohms", ResistorColorTrio.new(["orange", "orange", "black"]).label
end
def test_blue_and_grey_and_brown
skip
assert_equal "Resistor value: 680 ohms", ResistorColorTrio.new(["blue", "grey", "brown"]).label
end
def test_red_and_black_and_red
skip
assert_equal "Resistor value: 2 kiloohms", ResistorColorTrio.new(["red", "black", "red"]).label
end
def test_green_and_brown_and_orange
skip
assert_equal "Resistor value: 51 kiloohms", ResistorColorTrio.new(["green", "brown", "orange"]).label
end
def test_yellow_and_violet_and_yellow
skip
assert_equal "Resistor value: 470 kiloohms", ResistorColorTrio.new(["yellow", "violet", "yellow"]).label
end
def test_invalid_color
skip
assert_raises(ArgumentError) do
ResistorColorTrio.new(["yellow", "purple", "black"]).label
end
end
end
class ResistorColorTrio
COLORS = %w(black brown red orange yellow green blue violet grey white)
private
attr_reader :color_names
attr_reader :zeros
def initialize(color_names = [])
@color_names = color_names
@zeros = 0
end
def ohms
color_names.first(2).map do |v|
raise ArgumentError if COLORS.index(v).nil?
COLORS.index(v)
end.join
end
def zeros
'0' * COLORS.index(color_names[2])
end
def resistor_value
(ohms + zeros).to_i
end
def format
(resistor_value >= 1000) ? "#{resistor_value / 1000} kiloohms" : "#{resistor_value} ohms"
end
public
def label
"Resistor value: #{format}"
end
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.
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