resistor_color_trio

elixir/resistor-color-trio/.exercism/config.json

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+{
+  "authors": [
+    "jiegillet"
+  ],
+  "contributors": [
+    "angelikatyborska"
+  ],
+  "files": {
+    "solution": [
+      "lib/resistor_color_trio.ex"
+    ],
+    "test": [
+      "test/resistor_color_trio_test.exs"
+    ],
+    "example": [
+      ".meta/example.ex"
+    ]
+  },
+  "blurb": "Convert color codes, as used on resistors, to a human-readable label.",
+  "source": "Maud de Vries, Erik Schierboom",
+  "source_url": "https://github.com/exercism/problem-specifications/issues/1549"
+}

elixir/resistor-color-trio/.exercism/metadata.json

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+{"track":"elixir","exercise":"resistor-color-trio","id":"3c05c38d4119449a8cb120483b347a29","url":"https://exercism.org/tracks/elixir/exercises/resistor-color-trio","handle":"negrienko","is_requester":true,"auto_approve":false}

elixir/resistor-color-trio/.formatter.exs

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+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

elixir/resistor-color-trio/.gitignore

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+# The directory Mix will write compiled artifacts to.
+/_build/
+
+# If you run "mix test --cover", coverage assets end up here.
+/cover/
+
+# The directory Mix downloads your dependencies sources to.
+/deps/
+
+# Where third-party dependencies like ExDoc output generated docs.
+/doc/
+
+# Ignore .fetch files in case you like to edit your project deps locally.
+/.fetch
+
+# If the VM crashes, it generates a dump, let's ignore it too.
+erl_crash.dump
+
+# Also ignore archive artifacts (built via "mix archive.build").
+*.ez
+
+# Ignore package tarball (built via "mix hex.build").
+resistor_color_trio-*.tar
+

elixir/resistor-color-trio/HELP.md

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+# Help
+
+## Running the tests
+
+From the terminal, change to the base directory of the exercise then execute the tests with:
+
+```bash
+$ mix test
+```
+
+This will execute the test file found in the `test` subfolder -- a file ending in `_test.exs`
+
+Documentation:
+
+* [`mix test` - Elixir's test execution tool](https://hexdocs.pm/mix/Mix.Tasks.Test.html)
+* [`ExUnit` - Elixir's unit test library](https://hexdocs.pm/ex_unit/ExUnit.html)
+
+## Pending tests
+
+In test suites of practice exercises, all but the first test have been tagged to be skipped.
+
+Once you get a test passing, you can unskip the next one by commenting out the relevant `@tag :pending` with a `#` symbol.
+
+For example:
+
+```elixir
+# @tag :pending
+test "shouting" do
+  assert Bob.hey("WATCH OUT!") == "Whoa, chill out!"
+end
+```
+
+If you wish to run all tests at once, you can include all skipped test by using the `--include` flag on the `mix test` command:
+
+```bash
+$ mix test --include pending
+```
+
+Or, you can enable all the tests by commenting out the `ExUnit.configure` line in the file `test/test_helper.exs`.
+
+```elixir
+# ExUnit.configure(exclude: :pending, trace: true)
+```
+
+## Useful `mix test` options
+
+* `test/<FILE>.exs:LINENUM` - runs only a single test, the test from `<FILE>.exs` whose definition is on line `LINENUM`
+* `--failed` - runs only tests that failed the last time they ran
+* `--max-failures` - the suite stops evaluating tests when this number of test failures
+is reached
+* `--seed 0` - disables randomization so the tests in a single file will always be ran
+in the same order they were defined in
+
+## Submitting your solution
+
+You can submit your solution using the `exercism submit lib/resistor_color_trio.ex` command.
+This command will upload your solution to the Exercism website and print the solution page's URL.
+
+It's possible to submit an incomplete solution which allows you to:
+
+- See how others have completed the exercise
+- Request help from a mentor
+
+## Need to get help?
+
+If you'd like help solving the exercise, check the following pages:
+
+- The [Elixir track's documentation](https://exercism.org/docs/tracks/elixir)
+- The [Elixir track's programming category on the forum](https://forum.exercism.org/c/programming/elixir)
+- [Exercism's programming category on the forum](https://forum.exercism.org/c/programming/5)
+- The [Frequently Asked Questions](https://exercism.org/docs/using/faqs)
+
+Should those resources not suffice, you could submit your (incomplete) solution to request mentoring.
+
+If you're stuck on something, it may help to look at some of the [available resources](https://exercism.org/docs/tracks/elixir/resources) out there where answers might be found.

elixir/resistor-color-trio/README.md

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+# Resistor Color Trio
+
+Welcome to Resistor Color Trio on Exercism's Elixir Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## Instructions
+
+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:
+
+- Each resistor has a resistance value.
+- Resistors are small - so small in fact that if you printed the resistance value on them, it would be hard to read.
+  To get around this problem, manufacturers print color-coded bands onto the resistors to denote their resistance values.
+- Each band acts as a digit of a number.
+  For example, if they printed a brown band (value 1) followed by a green band (value 5), it would translate to the number 15.
+  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 3 colors as input, and outputs the correct value, in ohms.
+  The color bands are encoded as follows:
+
+- black: 0
+- brown: 1
+- red: 2
+- orange: 3
+- yellow: 4
+- green: 5
+- blue: 6
+- violet: 7
+- grey: 8
+- white: 9
+
+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:
+
+- orange-orange-black would be 33 and no zeros, which becomes 33 ohms.
+- orange-orange-red would be 33 and 2 zeros, which becomes 3300 ohms.
+- orange-orange-orange would be 33 and 3 zeros, which becomes 33000 ohms.
+
+(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 to larger resistors, a [metric prefix][metric-prefix] is used to indicate a larger magnitude of ohms, such as "kiloohms".
+That is similar to saying "2 kilometers" instead of "2000 meters", or "2 kilograms" for "2000 grams".
+
+For example, an input of `"orange", "orange", "orange"` should return:
+
+> "33 kiloohms"
+
+[metric-prefix]: https://en.wikipedia.org/wiki/Metric_prefix
+
+## Source
+
+### Created by
+
+- @jiegillet
+
+### Contributed to by
+
+- @angelikatyborska
+
+### Based on
+
+Maud de Vries, Erik Schierboom - https://github.com/exercism/problem-specifications/issues/1549

elixir/resistor-color-trio/lib/resistor_color_trio.ex

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+defmodule ResistorColorTrio do
+  @type color :: :black | :brown | :red | :orange | :yellow | :green | :blue | :violet | :grey | :white
+  @type colors :: [color]
+  @type unit :: :ohms | :kiloohms | :megaohms | :gigaohms
+
+  defguardp is_giga(value) when value >= 1_000_000_000
+  defguardp is_mega(value) when value >= 1_000_000
+  defguardp is_kilo(value) when value >= 1_000
+
+  @doc """
+  Calculate the resistance value in ohms from resistor colors
+  """
+  @spec label(colors) :: {number, unit}
+  def label(colors) do
+    colors
+    |> Enum.take(2)
+    |> Enum.map(&code/1)
+    |> Kernel.++(zeros(Enum.at(colors, 2)))
+    |> Integer.undigits()
+    |> with_unit()
+  end
+
+  @spec code(color) :: integer()
+  defp code(:black), do: 0
+  defp code(:brown), do: 1
+  defp code(:red), do: 2
+  defp code(:orange), do: 3
+  defp code(:yellow), do: 4
+  defp code(:green), do: 5
+  defp code(:blue), do: 6
+  defp code(:violet), do: 7
+  defp code(:grey), do: 8
+  defp code(:white), do: 9
+
+  @spec zeros(color) :: list()
+  defp zeros(color), do: List.duplicate(0, code(color))
+  
+  @spec with_unit(integer) :: {integer, unit}
+  defp with_unit(value) when is_giga(value), do: {div(value, 1_000_000_000), :gigaohms}
+  defp with_unit(value) when is_mega(value), do: {div(value, 1_000_000), :megaohms}
+  defp with_unit(value) when is_kilo(value), do: {div(value, 1_000), :kiloohms}
+  defp with_unit(value), do: {value, :ohms}
+end

elixir/resistor-color-trio/mix.exs

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+defmodule ResistorColorTrio.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :resistor_color_trio,
+      version: "0.1.0",
+      # elixir: "~> 1.8",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      extra_applications: [:logger]
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      # {:dep_from_hexpm, "~> 0.3.0"},
+      # {:dep_from_git, git: "https://github.com/elixir-lang/my_dep.git", tag: "0.1.0"}
+    ]
+  end
+end

elixir/resistor-color-trio/test/resistor_color_trio_test.exs

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+defmodule ResistorColorTrioTest do
+  use ExUnit.Case
+
+  test "Orange and orange and black" do
+    colors = [:orange, :orange, :black]
+    output = ResistorColorTrio.label(colors)
+    expected = {33, :ohms}
+
+    assert output == expected
+  end
+
+  test "Blue and grey and brown" do
+    colors = [:blue, :grey, :brown]
+    output = ResistorColorTrio.label(colors)
+    expected = {680, :ohms}
+
+    assert output == expected
+  end
+
+  test "Red and black and red" do
+    colors = [:red, :black, :red]
+    output = ResistorColorTrio.label(colors)
+    expected = {2, :kiloohms}
+
+    assert output == expected
+  end
+
+  test "Green and brown and orange" do
+    colors = [:green, :brown, :orange]
+    output = ResistorColorTrio.label(colors)
+    expected = {51, :kiloohms}
+
+    assert output == expected
+  end
+
+  test "Yellow and violet and yellow" do
+    colors = [:yellow, :violet, :yellow]
+    output = ResistorColorTrio.label(colors)
+    expected = {470, :kiloohms}
+
+    assert output == expected
+  end
+
+  test "Blue and violet and blue" do
+    colors = [:blue, :violet, :blue]
+    output = ResistorColorTrio.label(colors)
+    expected = {67, :megaohms}
+
+    assert output == expected
+  end
+
+  test "Minimum possible value" do
+    colors = [:black, :black, :black]
+    output = ResistorColorTrio.label(colors)
+    expected = {0, :ohms}
+
+    assert output == expected
+  end
+
+  test "Maximum possible value" do
+    colors = [:white, :white, :white]
+    output = ResistorColorTrio.label(colors)
+    expected = {99, :gigaohms}
+
+    assert output == expected
+  end
+
+  test "First two colors make an invalid octal number" do
+    colors = [:black, :grey, :black]
+    output = ResistorColorTrio.label(colors)
+    expected = {8, :ohms}
+
+    assert output == expected
+  end
+
+  test "Ignore extra colors" do
+    colors = [:blue, :green, :yellow, :orange]
+    output = ResistorColorTrio.label(colors)
+    expected = {650, :kiloohms}
+
+    assert output == expected
+  end
+
+  test "Kilo value" do
+    colors = [:brown, :black, :red]
+    output = ResistorColorTrio.label(colors)
+    expected = {1, :kiloohms}
+
+    assert output == expected
+  end
+
+  test "Mega value" do
+    colors = [:brown, :black, :green]
+    output = ResistorColorTrio.label(colors)
+    expected = {1, :megaohms}
+
+    assert output == expected
+  end
+
+  test "Giga value" do
+    colors = [:brown, :black, :grey]
+    output = ResistorColorTrio.label(colors)
+    expected = {1, :gigaohms}
+
+    assert output == expected
+  end
+end

elixir/resistor-color-trio/test/test_helper.exs

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+ExUnit.start()
+ExUnit.configure(exclude: :pending, trace: true)