roman-numbers

elixir/roman-numerals/.exercism/config.json

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+{
+  "authors": [
+    "rubysolo"
+  ],
+  "contributors": [
+    "andrewsardone",
+    "angelikatyborska",
+    "cetinajero",
+    "Cohen-Carlisle",
+    "dalexj",
+    "devonestes",
+    "jinyeow",
+    "lpil",
+    "neenjaw",
+    "parkerl",
+    "sotojuan",
+    "Teapane",
+    "waiting-for-dev"
+  ],
+  "files": {
+    "solution": [
+      "lib/roman_numerals.ex"
+    ],
+    "test": [
+      "test/roman_numerals_test.exs"
+    ],
+    "example": [
+      ".meta/example.ex"
+    ]
+  },
+  "blurb": "Convert modern Arabic numbers into Roman numerals.",
+  "source": "The Roman Numeral Kata",
+  "source_url": "https://codingdojo.org/kata/RomanNumerals/"
+}

elixir/roman-numerals/.exercism/metadata.json

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+{"track":"elixir","exercise":"roman-numerals","id":"a78bab796579451fae7b60be21481bff","url":"https://exercism.org/tracks/elixir/exercises/roman-numerals","handle":"negrienko","is_requester":true,"auto_approve":false}

elixir/roman-numerals/.formatter.exs

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

elixir/roman-numerals/.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").
+roman_numerals-*.tar
+

elixir/roman-numerals/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/roman_numerals.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/roman-numerals/README.md

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+# Roman Numerals
+
+Welcome to Roman Numerals on Exercism's Elixir Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## Introduction
+
+Today, most people in the world use Arabic numerals (0–9).
+But if you travelled back two thousand years, you'd find that most Europeans were using Roman numerals instead.
+
+To write a Roman numeral we use the following Latin letters, each of which has a value:
+
+| M    | D   | C   | L   | X   | V   | I   |
+| ---- | --- | --- | --- | --- | --- | --- |
+| 1000 | 500 | 100 | 50  | 10  | 5   | 1   |
+
+A Roman numeral is a sequence of these letters, and its value is the sum of the letters' values.
+For example, `XVIII` has the value 18 (`10 + 5 + 1 + 1 + 1 = 18`).
+
+There's one rule that makes things trickier though, and that's that **the same letter cannot be used more than three times in succession**.
+That means that we can't express numbers such as 4 with the seemingly natural `IIII`.
+Instead, for those numbers, we use a subtraction method between two letters.
+So we think of `4` not as `1 + 1 + 1 + 1` but instead as `5 - 1`.
+And slightly confusingly to our modern thinking, we write the smaller number first.
+This applies only in the following cases: 4 (`IV`), 9 (`IX`), 40 (`XL`), 90 (`XC`), 400 (`CD`) and 900 (`CM`).
+
+Order matters in Roman numerals!
+Letters (and the special compounds above) must be ordered by decreasing value from left to right.
+
+Here are some examples:
+
+```text
+ 105 => CV
+---- => --
+ 100 => C
++  5 =>  V
+```
+
+```text
+ 106 => CVI
+---- => --
+ 100 => C
++  5 =>  V
++  1 =>   I
+```
+
+```text
+ 104 => CIV
+---- => ---
+ 100 => C
++  4 =>  IV
+```
+
+And a final more complex example:
+
+```text
+ 1996 => MCMXCVI
+----- => -------
+ 1000 => M
++ 900 =>  CM
++  90 =>    XC
++   5 =>      V
++   1 =>       I
+```
+
+## Instructions
+
+Your task is to convert a number from Arabic numerals to Roman numerals.
+
+For this exercise, we are only concerned about traditional Roman numerals, in which the largest number is MMMCMXCIX (or 3,999).
+
+~~~~exercism/note
+There are lots of different ways to convert between Arabic and Roman numerals.
+We recommend taking a naive approach first to familiarise yourself with the concept of Roman numerals and then search for more efficient methods.
+
+Make sure to check out our Deep Dive video at the end to explore the different approaches you can take!
+~~~~
+
+## Source
+
+### Created by
+
+- @rubysolo
+
+### Contributed to by
+
+- @andrewsardone
+- @angelikatyborska
+- @cetinajero
+- @Cohen-Carlisle
+- @dalexj
+- @devonestes
+- @jinyeow
+- @lpil
+- @neenjaw
+- @parkerl
+- @sotojuan
+- @Teapane
+- @waiting-for-dev
+
+### Based on
+
+The Roman Numeral Kata - https://codingdojo.org/kata/RomanNumerals/

elixir/roman-numerals/lib/roman_numerals.ex

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+defmodule RomanNumerals do
+  @doc """
+  Convert the number to a roman number.
+  """
+  @romans %{
+    1 => ["I", "X", "C", "M"],
+    2 => ["II", "XX", "CC", "MM"],
+    3 => ["III",  "XXX", "CCC", "MMM"],
+    4 => ["IV",  "XL", "CD"],
+    5 => ["V",  "L", "D"],
+    6 => ["VI",  "LX", "DC"],
+    7 => ["VII",  "LXX", "DCC"],
+    8 => ["VIII",  "LXXX", "DCCC"],
+    9 => ["IX",  "XC", "CM"]
+  }
+
+  @spec numeral(pos_integer) :: String.t()
+  def numeral(number) do
+    number
+    |> Integer.digits()
+    |> Enum.reverse()
+    |> Enum.with_index(&to_roman_digit/2)
+    |> Enum.reverse()
+    |> Enum.join()
+  end
+
+  defp to_roman_digit(0, _index), do: ""
+  defp to_roman_digit(digit, index) do
+    @romans
+    |> Map.fetch!(digit)
+    |> Enum.at(index)
+  end
+end

elixir/roman-numerals/mix.exs

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+defmodule RomanNumerals.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :roman_numerals,
+      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/roman-numerals/test/roman_numerals_test.exs

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+defmodule RomanNumeralsTest do
+  use ExUnit.Case
+
+  test "1" do
+    assert RomanNumerals.numeral(1) == "I"
+  end
+
+  test "2" do
+    assert RomanNumerals.numeral(2) == "II"
+  end
+
+  test "3" do
+    assert RomanNumerals.numeral(3) == "III"
+  end
+
+  test "4" do
+    assert RomanNumerals.numeral(4) == "IV"
+  end
+
+  test "5" do
+    assert RomanNumerals.numeral(5) == "V"
+  end
+
+  test "6" do
+    assert RomanNumerals.numeral(6) == "VI"
+  end
+
+  test "9" do
+    assert RomanNumerals.numeral(9) == "IX"
+  end
+
+  test "16" do
+    assert RomanNumerals.numeral(16) == "XVI"
+  end
+
+  test "27" do
+    assert RomanNumerals.numeral(27) == "XXVII"
+  end
+
+  test "48" do
+    assert RomanNumerals.numeral(48) == "XLVIII"
+  end
+
+  test "59" do
+    assert RomanNumerals.numeral(59) == "LIX"
+  end
+
+  test "66" do
+    assert RomanNumerals.numeral(66) == "LXVI"
+  end
+
+  test "93" do
+    assert RomanNumerals.numeral(93) == "XCIII"
+  end
+
+  test "141" do
+    assert RomanNumerals.numeral(141) == "CXLI"
+  end
+
+  test "163" do
+    assert RomanNumerals.numeral(163) == "CLXIII"
+  end
+
+  test "402" do
+    assert RomanNumerals.numeral(402) == "CDII"
+  end
+
+  test "575" do
+    assert RomanNumerals.numeral(575) == "DLXXV"
+  end
+
+  test "666" do
+    assert RomanNumerals.numeral(666) == "DCLXVI"
+  end
+
+  test "911" do
+    assert RomanNumerals.numeral(911) == "CMXI"
+  end
+
+  test "1024" do
+    assert RomanNumerals.numeral(1024) == "MXXIV"
+  end
+
+  test "1666" do
+    assert RomanNumerals.numeral(1666) == "MDCLXVI"
+  end
+
+  test "3000" do
+    assert RomanNumerals.numeral(3000) == "MMM"
+  end
+
+  test "3001" do
+    assert RomanNumerals.numeral(3001) == "MMMI"
+  end
+
+  test "3888" do
+    assert RomanNumerals.numeral(3888) == "MMMDCCCLXXXVIII"
+  end
+
+  test "3999" do
+    assert RomanNumerals.numeral(3999) == "MMMCMXCIX"
+  end
+end

elixir/roman-numerals/test/test_helper.exs

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