Initial commit

elixir/language-list/.exercism/config.json

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+{
+  "authors": [
+    "neenjaw"
+  ],
+  "contributors": [
+    "fireproofsocks"
+  ],
+  "files": {
+    "solution": [
+      "lib/language_list.ex"
+    ],
+    "test": [
+      "test/language_list_test.exs"
+    ],
+    "exemplar": [
+      ".meta/exemplar.ex"
+    ]
+  },
+  "language_versions": ">=1.10",
+  "forked_from": [
+    "clojure/tracks-on-tracks-on-tracks"
+  ],
+  "blurb": "Learn about lists by keeping track of the programming languages you're currently learning on Exercism."
+}

elixir/language-list/.exercism/metadata.json

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+{"track":"elixir","exercise":"language-list","id":"1fc6fd5b991141188a10438edd755faa","url":"https://exercism.org/tracks/elixir/exercises/language-list","handle":"negrienko","is_requester":true,"auto_approve":false}

elixir/language-list/.formatter.exs

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

elixir/language-list/.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").
+strings-*.tar
+

elixir/language-list/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/language_list.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/language-list/HINTS.md

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+# Hints
+
+## General
+
+- Use the built-in [(linked) list type][list].
+
+## 1. Define a function to return an empty language list
+
+- The function needs to return `[]`.
+
+## 2. Define a function to add a language to the list
+
+- An element can be prepended to a list using `|`.
+
+## 3. Define a function to remove a language from the list
+
+- Elixir [provides a function][tl] to return a list with the first item removed.
+
+## 4. Define a function to return the first item in the list
+
+- Elixir [provides a function][hd] to get the first item from a list.
+
+## 5. Define a function to return how many languages are in the list
+
+- Elixir [provides a function][length] to count the length of a list.
+
+## 6. Define a function to determine if the list includes a functional language
+
+- Your function should return a boolean value indicating whether `"Elixir"` is a member of the list. Elixir [provides a function][in] to test list membership.
+
+[list]: https://elixir-lang.org/getting-started/basic-types.html#linked-lists
+[hd]: https://hexdocs.pm/elixir/Kernel.html#hd/1
+[tl]: https://hexdocs.pm/elixir/Kernel.html#tl/1
+[length]: https://hexdocs.pm/elixir/Kernel.html#length/1
+[in]: https://hexdocs.pm/elixir/Kernel.html#in/2

elixir/language-list/README.md

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+# Language List
+
+Welcome to Language List on Exercism's Elixir Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+If you get stuck on the exercise, check out `HINTS.md`, but try and solve it without using those first :)
+
+## Introduction
+
+## Lists
+
+Lists are built-in to the Elixir language. They are considered a basic type, denoted by square brackets. Lists may be empty or hold any number of items of any type. For example:
+
+```elixir
+empty_list = []
+one_item_list = [1]
+two_item_list = [1, 2]
+multiple_type_list = [1, :pi, 3.14, "four"]
+```
+
+Elixir implements lists as a linked list, where each node stores two values: the first item and another list with all the remaining items. The first item in the list is referred to as the _head_ and the remaining list of items is called the _tail_. We can use this notation in code:
+
+```elixir
+# [1] represented in [head | tail] notation
+[1 | []]
+
+# [1, 2, 3] represented in [head | tail] notation
+[1 | [2 | [3 | []]]]
+```
+
+We can use _`[head | tail]`_ notation to prepend elements to a list:
+
+```elixir
+# Suppose
+list = [2, 1]
+
+[3, 2, 1] == [3 | list]
+# => true
+```
+
+There are several functions in the `Kernel` module for working with lists, as well as the whole `List` module.
+
+```elixir
+# Check if 1 is a member of the list
+1 in [1, 2, 3, 4]
+# => true
+```
+
+## Instructions
+
+In this exercise you need to implement some functions to manipulate a list of programming languages.
+
+## 1. Define a function to return an empty language list
+
+Define the `new/0` function that takes no arguments and returns an empty list.
+
+```elixir
+LanguageList.new()
+# => []
+```
+
+## 2. Define a function to add a language to the list
+
+Define the `add/2` function that takes 2 arguments (a _language list_ and a string literal of a _language_). It should return the resulting list with the new language prepended to the given list.
+
+```elixir
+language_list = LanguageList.new()
+# => []
+language_list = LanguageList.add(language_list, "Clojure")
+# => ["Clojure"]
+language_list = LanguageList.add(language_list, "Haskell")
+# => ["Haskell", "Clojure"]
+```
+
+## 3. Define a function to remove a language from the list
+
+Define the `remove/1` function that takes 1 argument (a _language list_). It should return the list without the first item. Assume the list will always have at least one item.
+
+```elixir
+language_list = LanguageList.new()
+# => []
+language_list = LanguageList.add(language_list, "Clojure")
+# => ["Clojure"]
+language_list = LanguageList.add(language_list, "Haskell")
+# => ["Haskell", "Clojure"]
+language_list = LanguageList.remove(language_list)
+# => ["Clojure"]
+```
+
+## 4. Define a function to return the first item in the list
+
+Define the `first/1` function that takes 1 argument (a _language list_). It should return the first language in the list. Assume the list will always have at least one item.
+
+```elixir
+language_list = LanguageList.new()
+# => []
+language_list = LanguageList.add(language_list, "Elm")
+# => ["Elm"]
+language_list = LanguageList.add(language_list, "Prolog")
+# => ["Prolog", "Elm"]
+LanguageList.first(language_list)
+# => "Prolog"
+```
+
+## 5. Define a function to return how many languages are in the list
+
+Define the `count/1` function that takes 1 argument (a _language list_). It should return the number of languages in the list.
+
+```elixir
+language_list = LanguageList.new()
+# => []
+language_list = LanguageList.add(language_list, "Elm")
+# => ["Elm"]
+language_list = LanguageList.add(language_list, "Prolog")
+# => ["Prolog", "Elm"]
+LanguageList.count(language_list)
+# => 2
+```
+
+## 6. Define a function to determine if the list includes a functional language
+
+Define the `functional_list?/1` function which takes 1 argument (a _language list_). It should return a boolean value. It should return true if _"Elixir"_ is one of the languages in the list.
+
+```elixir
+language_list = LanguageList.new()
+# => []
+language_list = LanguageList.add(language_list, "Elixir")
+# => ["Elixir"]
+LanguageList.functional_list?(language_list)
+# => true
+```
+
+## Source
+
+### Created by
+
+- @neenjaw
+
+### Contributed to by
+
+- @fireproofsocks

elixir/language-list/lib/language_list.ex

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+defmodule LanguageList do
+  def new(), do: []
+
+  def add(list, language), do: [language | list]
+
+  def remove(list), do: tl(list)
+
+  def first(list), do: hd(list)
+
+  def count(list), do: length(list)
+
+  def functional_list?(list), do: "Elixir" in list
+end

elixir/language-list/mix.exs

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+defmodule LanguageList.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :language_list,
+      version: "0.1.0",
+      # elixir: "~> 1.10",
+      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/language-list/test/language_list_test.exs

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+defmodule LanguageListTest do
+  use ExUnit.Case
+
+  describe "new/0" do
+    @tag task_id: 1
+    test "new list" do
+      assert LanguageList.new() == []
+    end
+  end
+
+  describe "add/2" do
+    @tag task_id: 2
+    test "add a language to a list" do
+      language = "Elixir"
+      list = [language]
+
+      assert LanguageList.new() |> LanguageList.add(language) == list
+    end
+
+    @tag task_id: 2
+    test "add several languages to a list" do
+      list =
+        LanguageList.new()
+        |> LanguageList.add("Clojure")
+        |> LanguageList.add("Haskell")
+        |> LanguageList.add("Erlang")
+        |> LanguageList.add("F#")
+        |> LanguageList.add("Elixir")
+
+      assert list == ["Elixir", "F#", "Erlang", "Haskell", "Clojure"]
+    end
+  end
+
+  describe "remove/1" do
+    @tag task_id: 3
+    test "add then remove results in empty list" do
+      list =
+        LanguageList.new()
+        |> LanguageList.add("Elixir")
+        |> LanguageList.remove()
+
+      assert list == []
+    end
+
+    @tag task_id: 3
+    test "adding two languages, when removed, removes first item" do
+      list =
+        LanguageList.new()
+        |> LanguageList.add("F#")
+        |> LanguageList.add("Elixir")
+        |> LanguageList.remove()
+
+      assert list == ["F#"]
+    end
+  end
+
+  describe "first/1" do
+    @tag task_id: 4
+    test "add one language, then get the first" do
+      assert LanguageList.new() |> LanguageList.add("Elixir") |> LanguageList.first() == "Elixir"
+    end
+
+    @tag task_id: 4
+    test "add a few languages, then get the first" do
+      first =
+        LanguageList.new()
+        |> LanguageList.add("Elixir")
+        |> LanguageList.add("Prolog")
+        |> LanguageList.add("F#")
+        |> LanguageList.first()
+
+      assert first == "F#"
+    end
+  end
+
+  describe "count/1" do
+    @tag task_id: 5
+    test "the count of a new list is 0" do
+      assert LanguageList.new() |> LanguageList.count() == 0
+    end
+
+    @tag task_id: 5
+    test "the count of a one-language list is 1" do
+      count =
+        LanguageList.new()
+        |> LanguageList.add("Elixir")
+        |> LanguageList.count()
+
+      assert count == 1
+    end
+
+    @tag task_id: 5
+    test "the count of a multiple-item list is equal to its length" do
+      count =
+        LanguageList.new()
+        |> LanguageList.add("Elixir")
+        |> LanguageList.add("Prolog")
+        |> LanguageList.add("F#")
+        |> LanguageList.count()
+
+      assert count == 3
+    end
+  end
+
+  describe "functional_list?/1" do
+    @tag task_id: 6
+    test "a functional language list" do
+      assert LanguageList.functional_list?(["Clojure", "Haskell", "Erlang", "F#", "Elixir"])
+    end
+
+    @tag task_id: 6
+    test "not a functional language list" do
+      refute LanguageList.functional_list?(["Java", "C", "JavaScript"])
+    end
+  end
+end

elixir/language-list/test/test_helper.exs

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+ExUnit.start()
+ExUnit.configure(exclude: :pending, trace: true, seed: 0)