matrix

elixir/matrix/.exercism/config.json

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+{
+  "authors": [
+    "DoggettCK"
+  ],
+  "contributors": [
+    "angelikatyborska",
+    "Cohen-Carlisle",
+    "devonestes",
+    "neenjaw",
+    "sotojuan"
+  ],
+  "files": {
+    "solution": [
+      "lib/matrix.ex"
+    ],
+    "test": [
+      "test/matrix_test.exs"
+    ],
+    "example": [
+      ".meta/example.ex"
+    ]
+  },
+  "blurb": "Given a string representing a matrix of numbers, return the rows and columns of that matrix.",
+  "source": "Exercise by the JumpstartLab team for students at The Turing School of Software and Design.",
+  "source_url": "https://turing.edu"
+}

elixir/matrix/.exercism/metadata.json

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+{"track":"elixir","exercise":"matrix","id":"fe0c39c0c4124236a5ff391451e0c59d","url":"https://exercism.org/tracks/elixir/exercises/matrix","handle":"negrienko","is_requester":true,"auto_approve":false}

elixir/matrix/.formatter.exs

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

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

elixir/matrix/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/matrix.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/matrix/README.md

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+# Matrix
+
+Welcome to Matrix on Exercism's Elixir Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## Instructions
+
+Given a string representing a matrix of numbers, return the rows and columns of that matrix.
+
+So given a string with embedded newlines like:
+
+```text
+9 8 7
+5 3 2
+6 6 7
+```
+
+representing this matrix:
+
+```text
+    1  2  3
+  |---------
+1 | 9  8  7
+2 | 5  3  2
+3 | 6  6  7
+```
+
+your code should be able to spit out:
+
+- A list of the rows, reading each row left-to-right while moving top-to-bottom across the rows,
+- A list of the columns, reading each column top-to-bottom while moving from left-to-right.
+
+The rows for our example matrix:
+
+- 9, 8, 7
+- 5, 3, 2
+- 6, 6, 7
+
+And its columns:
+
+- 9, 5, 6
+- 8, 3, 6
+- 7, 2, 7
+
+## Source
+
+### Created by
+
+- @DoggettCK
+
+### Contributed to by
+
+- @angelikatyborska
+- @Cohen-Carlisle
+- @devonestes
+- @neenjaw
+- @sotojuan
+
+### Based on
+
+Exercise by the JumpstartLab team for students at The Turing School of Software and Design. - https://turing.edu

elixir/matrix/lib/matrix.ex

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+defmodule Matrix do
+  defstruct ~w(rows columns)a
+
+  defp at(list, index), do: Enum.at(list, index - 1)
+
+  defp transpose(list), do: Enum.zip_with(list, &Function.identity/1)
+
+  defp parse_columns(string), do: String.split(string, "\n")
+
+  defp parse_row(row) do
+    row
+    |> String.split(" ")
+    |> Enum.map(&String.to_integer/1)
+  end
+
+  @doc """
+  Convert an `input` string, with rows separated by newlines and values
+  separated by single spaces, into a `Matrix` struct.
+  """
+  @spec from_string(input :: String.t()) :: %Matrix{}
+  def from_string(input) do
+    matrix =
+      input
+      |> parse_columns()
+      |> Enum.map(&parse_row/1)
+
+    struct(__MODULE__, rows: matrix, columns: transpose(matrix))
+  end
+
+  @doc """
+  Write the `matrix` out as a string, with rows separated by newlines and
+  values separated by single spaces.
+  """
+  @spec to_string(matrix :: %Matrix{}) :: String.t()
+  def to_string(matrix), do: Enum.map_join(matrix.rows, "\n", &Enum.join(&1, " "))
+
+  @doc """
+  Given a `matrix`, return its rows as a list of lists of integers.
+  """
+  @spec rows(matrix :: %Matrix{}) :: list(list(integer))
+  def rows(matrix), do: matrix.rows
+
+  @doc """
+  Given a `matrix` and `index`, return the row at `index`.
+  """
+  @spec row(matrix :: %Matrix{}, index :: integer) :: list(integer)
+  def row(matrix, index), do: at(matrix.rows, index)
+
+  @doc """
+  Given a `matrix`, return its columns as a list of lists of integers.
+  """
+  @spec columns(matrix :: %Matrix{}) :: list(list(integer))
+  def columns(matrix), do: matrix.columns
+
+  @doc """
+  Given a `matrix` and `index`, return the column at `index`.
+  """
+  @spec column(matrix :: %Matrix{}, index :: integer) :: list(integer)
+  def column(matrix, index), do: at(matrix.columns, index)
+end

elixir/matrix/mix.exs

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+defmodule Matrix.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :matrix,
+      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/matrix/test/matrix_test.exs

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+defmodule MatrixTest do
+  use ExUnit.Case
+
+  describe "row" do
+    test "extract row from one number matrix" do
+      matrix = Matrix.from_string("1")
+      assert Matrix.row(matrix, 1) == [1]
+    end
+
+    test "can extract row" do
+      matrix = Matrix.from_string("1 2\n3 4")
+      assert Matrix.row(matrix, 2) == [3, 4]
+    end
+
+    test "extract row where numbers have different widths" do
+      matrix = Matrix.from_string("1 2\n10 20")
+      assert Matrix.row(matrix, 2) == [10, 20]
+    end
+
+    test "can extract row from non-square matrix with no corresponding column" do
+      matrix = Matrix.from_string("1 2 3\n4 5 6\n7 8 9\n8 7 6")
+      assert Matrix.row(matrix, 4) == [8, 7, 6]
+    end
+  end
+
+  describe "rows" do
+    test "rows should return nested lists regardless of internal structure" do
+      matrix = Matrix.from_string("1 2 3\n4 5 6\n7 8 9")
+
+      assert Matrix.rows(matrix) == [
+               [1, 2, 3],
+               [4, 5, 6],
+               [7, 8, 9]
+             ]
+    end
+  end
+
+  describe "column" do
+    test "extract column from one number matrix" do
+      matrix = Matrix.from_string("1")
+      assert Matrix.column(matrix, 1) == [1]
+    end
+
+    test "can extract column" do
+      matrix = Matrix.from_string("1 2 3\n4 5 6\n7 8 9")
+      assert Matrix.column(matrix, 3) == [3, 6, 9]
+    end
+
+    test "can extract column from non-square matrix with no corresponding row" do
+      matrix = Matrix.from_string("1 2 3 4\n5 6 7 8\n9 8 7 6")
+      assert Matrix.column(matrix, 4) == [4, 8, 6]
+    end
+
+    test "extract column where numbers have different widths" do
+      matrix = Matrix.from_string("89 1903 3\n18 3 1\n9 4 800")
+      assert Matrix.column(matrix, 2) == [1903, 3, 4]
+    end
+  end
+
+  describe "columns" do
+    test "columns should return nested lists regardless of internal structure" do
+      matrix = Matrix.from_string("1 2 3\n4 5 6\n7 8 9")
+
+      assert Matrix.columns(matrix) == [
+               [1, 4, 7],
+               [2, 5, 8],
+               [3, 6, 9]
+             ]
+    end
+  end
+
+  describe "to_string" do
+    test "writing to string" do
+      matrix = Matrix.from_string("1 2 3\n4 5 6\n7 8 9")
+      assert Matrix.to_string(matrix) == "1 2 3\n4 5 6\n7 8 9"
+    end
+  end
+end

elixir/matrix/test/test_helper.exs

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