proverb

elixir/proverb/.exercism/config.json

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+{
+  "authors": [
+    "jiegillet"
+  ],
+  "contributors": [
+    "angelikatyborska"
+  ],
+  "files": {
+    "solution": [
+      "lib/proverb.ex"
+    ],
+    "test": [
+      "test/proverb_test.exs"
+    ],
+    "example": [
+      ".meta/example.ex"
+    ]
+  },
+  "blurb": "For want of a horseshoe nail, a kingdom was lost, or so the saying goes. Output the full text of this proverbial rhyme.",
+  "source": "Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/For_Want_of_a_Nail"
+}

elixir/proverb/.exercism/metadata.json

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+{"track":"elixir","exercise":"proverb","id":"ea1c76c464144259a45e86a6fa8b920b","url":"https://exercism.org/tracks/elixir/exercises/proverb","handle":"negrienko","is_requester":true,"auto_approve":false}

elixir/proverb/.formatter.exs

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

elixir/proverb/.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").
+proverb-*.tar
+

elixir/proverb/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/proverb.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/proverb/README.md

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+# Proverb
+
+Welcome to Proverb on Exercism's Elixir Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## Instructions
+
+For want of a horseshoe nail, a kingdom was lost, or so the saying goes.
+
+Given a list of inputs, generate the relevant proverb.
+For example, given the list `["nail", "shoe", "horse", "rider", "message", "battle", "kingdom"]`, you will output the full text of this proverbial rhyme:
+
+```text
+For want of a nail the shoe was lost.
+For want of a shoe the horse was lost.
+For want of a horse the rider was lost.
+For want of a rider the message was lost.
+For want of a message the battle was lost.
+For want of a battle the kingdom was lost.
+And all for the want of a nail.
+```
+
+Note that the list of inputs may vary; your solution should be able to handle lists of arbitrary length and content.
+No line of the output text should be a static, unchanging string; all should vary according to the input given.
+
+## Source
+
+### Created by
+
+- @jiegillet
+
+### Contributed to by
+
+- @angelikatyborska
+
+### Based on
+
+Wikipedia - https://en.wikipedia.org/wiki/For_Want_of_a_Nail

elixir/proverb/lib/proverb.ex

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+defmodule Proverb do
+  @doc """
+  Generate a proverb from a list of strings.
+  """
+  @spec recite(strings :: [String.t()]) :: String.t()
+  def recite([]), do: ""
+  def recite([one]), do: first_in_the_end(one)
+  def recite([head | tail]), do: Enum.join([first(head), recite_proverb(tail), first_in_the_end(head)])
+    
+  defp recite_proverb([last]), do: last(last)
+  defp recite_proverb([middle | tail]), do: middle(middle) <> " " <> recite_proverb(tail)
+
+  defp first(first), do: "For want of a #{first} "
+  defp middle(middle), do: "the #{middle} was lost.\nFor want of a #{middle}"
+  defp last(last), do: "the #{last} was lost.\n"
+  defp first_in_the_end(first), do: "And all for the want of a #{first}.\n"
+end

elixir/proverb/mix.exs

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+defmodule Proverb.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :proverb,
+      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/proverb/test/proverb_test.exs

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+defmodule ProverbTest do
+  use ExUnit.Case
+
+  test "zero pieces" do
+    strings = []
+    output = Proverb.recite(strings)
+    expected = ""
+
+    assert output == expected
+  end
+
+  test "one piece" do
+    strings = ["nail"]
+    output = Proverb.recite(strings)
+
+    expected = """
+    And all for the want of a nail.
+    """
+
+    assert output == expected
+  end
+
+  test "two pieces" do
+    strings = ["nail", "shoe"]
+    output = Proverb.recite(strings)
+
+    expected = """
+    For want of a nail the shoe was lost.
+    And all for the want of a nail.
+    """
+
+    assert output == expected
+  end
+
+  test "three pieces" do
+    strings = ["nail", "shoe", "horse"]
+    output = Proverb.recite(strings)
+
+    expected = """
+    For want of a nail the shoe was lost.
+    For want of a shoe the horse was lost.
+    And all for the want of a nail.
+    """
+
+    assert output == expected
+  end
+
+  test "full proverb" do
+    strings = ["nail", "shoe", "horse", "rider", "message", "battle", "kingdom"]
+    output = Proverb.recite(strings)
+
+    expected = """
+    For want of a nail the shoe was lost.
+    For want of a shoe the horse was lost.
+    For want of a horse the rider was lost.
+    For want of a rider the message was lost.
+    For want of a message the battle was lost.
+    For want of a battle the kingdom was lost.
+    And all for the want of a nail.
+    """
+
+    assert output == expected
+  end
+
+  test "four pieces modernized" do
+    strings = ["pin", "gun", "soldier", "battle"]
+    output = Proverb.recite(strings)
+
+    expected = """
+    For want of a pin the gun was lost.
+    For want of a gun the soldier was lost.
+    For want of a soldier the battle was lost.
+    And all for the want of a pin.
+    """
+
+    assert output == expected
+  end
+end

elixir/proverb/test/test_helper.exs

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