armstrong_number

elixir/armstrong-numbers/.exercism/config.json

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+{
+  "authors": [
+    "Bscruz19"
+  ],
+  "contributors": [
+    "angelikatyborska",
+    "Br1ght0ne",
+    "Cohen-Carlisle",
+    "devonestes",
+    "neenjaw",
+    "tsuka"
+  ],
+  "files": {
+    "solution": [
+      "lib/armstrong_number.ex"
+    ],
+    "test": [
+      "test/armstrong_number_test.exs"
+    ],
+    "example": [
+      ".meta/example.ex"
+    ]
+  },
+  "blurb": "Determine if a number is an Armstrong number.",
+  "source": "Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/Narcissistic_number"
+}

elixir/armstrong-numbers/.exercism/metadata.json

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+{"track":"elixir","exercise":"armstrong-numbers","id":"87b5aa5429664271a572c9f3ac0722d1","url":"https://exercism.org/tracks/elixir/exercises/armstrong-numbers","handle":"negrienko","is_requester":true,"auto_approve":false}

elixir/armstrong-numbers/.formatter.exs

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

elixir/armstrong-numbers/.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").
+armstrong_numbers-*.tar
+

elixir/armstrong-numbers/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/armstrong_number.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/armstrong-numbers/README.md

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+# Armstrong Numbers
+
+Welcome to Armstrong Numbers on Exercism's Elixir Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## Instructions
+
+An [Armstrong number][armstrong-number] is a number that is the sum of its own digits each raised to the power of the number of digits.
+
+For example:
+
+- 9 is an Armstrong number, because `9 = 9^1 = 9`
+- 10 is _not_ an Armstrong number, because `10 != 1^2 + 0^2 = 1`
+- 153 is an Armstrong number, because: `153 = 1^3 + 5^3 + 3^3 = 1 + 125 + 27 = 153`
+- 154 is _not_ an Armstrong number, because: `154 != 1^3 + 5^3 + 4^3 = 1 + 125 + 64 = 190`
+
+Write some code to determine whether a number is an Armstrong number.
+
+[armstrong-number]: https://en.wikipedia.org/wiki/Narcissistic_number
+
+## Source
+
+### Created by
+
+- @Bscruz19
+
+### Contributed to by
+
+- @angelikatyborska
+- @Br1ght0ne
+- @Cohen-Carlisle
+- @devonestes
+- @neenjaw
+- @tsuka
+
+### Based on
+
+Wikipedia - https://en.wikipedia.org/wiki/Narcissistic_number

elixir/armstrong-numbers/lib/armstrong_number.ex

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+defmodule ArmstrongNumber do
+  @moduledoc """
+  Provides a way to validate whether or not a number is an Armstrong number
+  """
+
+  @spec valid?(integer) :: boolean
+  def valid?(number) do
+    digits = Integer.digits(number)
+    power = length(digits)
+
+    Enum.reduce(digits, 0, &(&1 ** power + &2)) == number
+  end
+end

elixir/armstrong-numbers/mix.exs

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+defmodule ArmstrongNumber.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :armstrong_number,
+      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/armstrong-numbers/test/armstrong_number_test.exs

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+defmodule ArmstrongNumberTest do
+  use ExUnit.Case
+
+  test "Zero is an Armstrong number" do
+    assert ArmstrongNumber.valid?(0)
+  end
+
+  test "Single digit numbers are Armstrong numbers" do
+    assert ArmstrongNumber.valid?(5)
+  end
+
+  test "There are no two-digit Armstrong Numbers" do
+    refute ArmstrongNumber.valid?(10)
+  end
+
+  test "Three-digit number that is an Armstrong number" do
+    assert ArmstrongNumber.valid?(153)
+  end
+
+  test "Three-digit number that is not an Armstrong number" do
+    refute ArmstrongNumber.valid?(100)
+  end
+
+  test "Four-digit number that is an Armstrong number" do
+    assert ArmstrongNumber.valid?(9474)
+  end
+
+  test "Four-digit number that is not an Armstrong number" do
+    refute ArmstrongNumber.valid?(9475)
+  end
+
+  test "Seven-digit number that is an Armstrong number" do
+    assert ArmstrongNumber.valid?(9_926_315)
+  end
+
+  test "Seven-digit number that is not an Armstrong number" do
+    refute ArmstrongNumber.valid?(9_926_134)
+  end
+
+  test "Armstrong number containing seven zeroes" do
+    assert ArmstrongNumber.valid?(186_709_961_001_538_790_100_634_132_976_990)
+  end
+
+  test "The largest and last Armstrong number" do
+    assert ArmstrongNumber.valid?(115_132_219_018_763_992_565_095_597_973_971_522_401)
+  end
+end

elixir/armstrong-numbers/test/test_helper.exs

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