flatten_array

elixir/flatten-array/.exercism/config.json

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+{
+  "authors": [
+    "bernardoamc"
+  ],
+  "contributors": [
+    "angelikatyborska",
+    "Cohen-Carlisle",
+    "devonestes",
+    "jwworth",
+    "lpil",
+    "neenjaw",
+    "parkerl",
+    "sotojuan"
+  ],
+  "files": {
+    "solution": [
+      "lib/flatten_array.ex"
+    ],
+    "test": [
+      "test/flatten_array_test.exs"
+    ],
+    "example": [
+      ".meta/example.ex"
+    ]
+  },
+  "blurb": "Take a nested list and return a single list with all values except nil/null.",
+  "source": "Interview Question",
+  "source_url": "https://reference.wolfram.com/language/ref/Flatten.html"
+}

elixir/flatten-array/.exercism/metadata.json

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+{"track":"elixir","exercise":"flatten-array","id":"639fd9778c30461b89f59d69b0d55de1","url":"https://exercism.org/tracks/elixir/exercises/flatten-array","handle":"negrienko","is_requester":true,"auto_approve":false}

elixir/flatten-array/.formatter.exs

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

elixir/flatten-array/.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").
+flatten_array-*.tar
+

elixir/flatten-array/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/flatten_array.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/flatten-array/README.md

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+# Flatten Array
+
+Welcome to Flatten Array on Exercism's Elixir Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## Instructions
+
+Take a nested list and return a single flattened list with all values except nil/null.
+
+The challenge is to take an arbitrarily-deep nested list-like structure and produce a flattened structure without any nil/null values.
+
+For example:
+
+input: [1,[2,3,null,4],[null],5]
+
+output: [1,2,3,4,5]
+
+## Source
+
+### Created by
+
+- @bernardoamc
+
+### Contributed to by
+
+- @angelikatyborska
+- @Cohen-Carlisle
+- @devonestes
+- @jwworth
+- @lpil
+- @neenjaw
+- @parkerl
+- @sotojuan
+
+### Based on
+
+Interview Question - https://reference.wolfram.com/language/ref/Flatten.html

elixir/flatten-array/lib/flatten_array.ex

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+defmodule FlattenArray do
+  @doc """
+    Accept a list and return the list flattened without nil values.
+
+    ## Examples
+
+      iex> FlattenArray.flatten([1, [2], 3, nil])
+      [1, 2, 3]
+
+      iex> FlattenArray.flatten([nil, nil])
+      []
+
+  """
+
+  @spec flatten(list) :: list
+  def flatten(list) do
+    list
+    |> List.flatten()
+    |> Enum.reject(&is_nil/1)
+  end
+end

elixir/flatten-array/mix.exs

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+defmodule FlattenArray.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :flatten_array,
+      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/flatten-array/test/flatten_array_test.exs

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+defmodule FlattenArrayTest do
+  use ExUnit.Case
+
+  test "empty" do
+    assert FlattenArray.flatten([]) ==
+             []
+  end
+
+  test "no nesting" do
+    assert FlattenArray.flatten([0, 1, 2]) ==
+             [0, 1, 2]
+  end
+
+  test "flattens a nested array" do
+    assert FlattenArray.flatten([[[]]]) ==
+             []
+  end
+
+  test "flattens array with just integers present" do
+    assert FlattenArray.flatten([1, [2, 3, 4, 5, 6, 7], 8]) ==
+             [1, 2, 3, 4, 5, 6, 7, 8]
+  end
+
+  test "5 level nesting" do
+    assert FlattenArray.flatten([0, 2, [[2, 3], 8, 100, 4, [[[50]]]], -2]) ==
+             [0, 2, 2, 3, 8, 100, 4, 50, -2]
+  end
+
+  test "6 level nesting" do
+    assert FlattenArray.flatten([1, [2, [[3]], [4, [[5]]], 6, 7], 8]) ==
+             [1, 2, 3, 4, 5, 6, 7, 8]
+  end
+
+  test "nil values values are omitted from the final result" do
+    assert FlattenArray.flatten([1, 2, nil]) ==
+             [1, 2]
+  end
+
+  test "consecutive nil values at the front of the list are omitted from the final result" do
+    assert FlattenArray.flatten([nil, nil, 3]) ==
+             [3]
+  end
+
+  test "consecutive nil values in the middle of the list are omitted from the final result" do
+    assert FlattenArray.flatten([1, nil, nil, 4]) ==
+             [1, 4]
+  end
+
+  test "6 level nesting with nil values" do
+    assert FlattenArray.flatten([0, 2, [[2, 3], 8, [[100]], nil, [[nil]]], -2]) ==
+             [0, 2, 2, 3, 8, 100, -2]
+  end
+
+  test "all values in nested list are null" do
+    assert FlattenArray.flatten([nil, [[[nil]]], nil, nil, [[nil, nil], nil], nil]) ==
+             []
+  end
+end

elixir/flatten-array/test/test_helper.exs

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