If you want to build something using a Raspberry Pi, you'll probably use resistors. For this exercise, you need to know two things about them:
In this exercise, you are going to create a helpful program so that you don't have to remember the values of the bands. The program will take two colors as input, and output the correct number.
The band colors are encoded as follows:
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:
To include color from the command line:
ruby -r minitest/pride resistor_color_duo_test.rb
Maud de Vries, Erik Schierboom https://github.com/exercism/problem-specifications/issues/1464
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_duo' # Common test data version: 2.0.0 8b44ce1 class ResistorColorDuoTest < Minitest::Test def test_brown_and_black # skip assert_equal 10, ResistorColorDuo.value(["brown", "black"]) end def test_blue_and_grey skip assert_equal 68, ResistorColorDuo.value(["blue", "grey"]) end def test_yellow_and_violet skip assert_equal 47, ResistorColorDuo.value(["yellow", "violet"]) end def test_orange_and_orange skip assert_equal 33, ResistorColorDuo.value(["orange", "orange"]) end end
# frozen_string_literal: true module ResistorColorDuo COLORS = %w[ black brown red orange yellow green blue violet grey white ].freeze private_constant :COLORS module_function def value(bands) bands.reduce(0, &method(:add_resistor_value)) end def add_resistor_value(acc, band) acc * 10 + COLORS.index(band) end private_class_method :add_resistor_value 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.