Implement roman-numerals in Elixir

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`.
+
+## Instructions
+
+Write a function to convert from normal numbers to Roman Numerals.
+
+The Romans were a clever bunch.
+They conquered most of Europe and ruled it for hundreds of years.
+They invented concrete and straight roads and even bikinis.
+One thing they never discovered though was the number zero.
+This made writing and dating extensive histories of their exploits slightly more challenging, but the system of numbers they came up with is still in use today.
+For example the BBC uses Roman numerals to date their programs.
+
+The Romans wrote numbers using letters - I, V, X, L, C, D, M.
+(notice these letters have lots of straight lines and are hence easy to hack into stone tablets).
+
+```text
+ 1 => I
+10 => X
+ 7 => VII
+```
+
+The maximum number supported by this notation is 3,999.
+(The Romans themselves didn't tend to go any higher)
+
+Wikipedia says: Modern Roman numerals ... are written by expressing each digit separately starting with the left most digit and skipping any digit with a value of zero.
+
+To see this in practice, consider the example of 1990.
+
+In Roman numerals 1990 is MCMXC:
+
+1000=M
+900=CM
+90=XC
+
+2008 is written as MMVIII:
+
+2000=MM
+8=VIII
+
+Learn more about [Roman numerals on Wikipedia][roman-numerals].
+
+[roman-numerals]: https://wiki.imperivm-romanvm.com/wiki/Roman_Numerals
+
+## 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.
+ """
+ @spec numeral(pos_integer) :: String.t()
+ def numeral(number) do
+ result =
+ [1000, 500, 100, 50, 10, 5, 1]
+ |> Enum.reduce({"", number}, fn cur, {result, num} ->
+ case round(:math.floor(num / cur)) do
+ 0 ->
+ {result, num}
+
+ amount ->
+ result =
+ result <>
+ (Range.to_list(1..amount) |> Enum.map(fn _ -> to_literal(cur) end) |> Enum.join())
+
+ {result, num - amount * cur}
+ end
+ end)
+ |> then(fn {result, _} -> result end)
+
+ Enum.reduce(
+ [
+ {"DCCCC", "CM"},
+ {"CCCC", "CD"},
+ {"LXXXX", "XC"},
+ {"XXXX", "XL"},
+ {"VIIII", "IX"},
+ {"IIII", "IV"}
+ ],
+ result,
+ fn {src, dest}, acc ->
+ String.replace(acc, src, dest)
+ end
+ )
+ end
+
+ defp to_literal(1), do: "I"
+ defp to_literal(5), do: "V"
+ defp to_literal(10), do: "X"
+ defp to_literal(50), do: "L"
+ defp to_literal(100), do: "C"
+ defp to_literal(500), do: "D"
+ defp to_literal(1000), do: "M"
+ defp to_literal(_), do: ""
+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 "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 "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 "911" do
+ assert RomanNumerals.numeral(911) == "CMXI"
+ end
+
+ test "1024" do
+ assert RomanNumerals.numeral(1024) == "MXXIV"
+ end
+
+ test "3000" do
+ assert RomanNumerals.numeral(3000) == "MMM"
+ end
+
+ test "16" do
+ assert RomanNumerals.numeral(16) == "XVI"
+ end
+
+ test "66" do
+ assert RomanNumerals.numeral(66) == "LXVI"
+ end
+
+ test "166" do
+ assert RomanNumerals.numeral(166) == "CLXVI"
+ end
+
+ test "666" do
+ assert RomanNumerals.numeral(666) == "DCLXVI"
+ end
+
+ test "1666" do
+ assert RomanNumerals.numeral(1666) == "MDCLXVI"
+ end
+
+ test "3001" do
+ assert RomanNumerals.numeral(3001) == "MMMI"
+ 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)