triangle

elixir/triangle/.exercism/config.json

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+{
+  "authors": [
+    "rubysolo"
+  ],
+  "contributors": [
+    "andrewsardone",
+    "angelikatyborska",
+    "Cohen-Carlisle",
+    "dalexj",
+    "devonestes",
+    "jinyeow",
+    "lpil",
+    "neenjaw",
+    "parkerl",
+    "ryanzidago",
+    "sotojuan",
+    "Teapane",
+    "waiting-for-dev"
+  ],
+  "files": {
+    "solution": [
+      "lib/triangle.ex"
+    ],
+    "test": [
+      "test/triangle_test.exs"
+    ],
+    "example": [
+      ".meta/example.ex"
+    ]
+  },
+  "blurb": "Determine if a triangle is equilateral, isosceles, or scalene.",
+  "source": "The Ruby Koans triangle project, parts 1 & 2",
+  "source_url": "https://web.archive.org/web/20220831105330/http://rubykoans.com"
+}

elixir/triangle/.exercism/metadata.json

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+{"track":"elixir","exercise":"triangle","id":"4438c1b9c97b462a976fc55154458a8f","url":"https://exercism.org/tracks/elixir/exercises/triangle","handle":"negrienko","is_requester":true,"auto_approve":false}

elixir/triangle/.formatter.exs

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

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

elixir/triangle/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/triangle.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/triangle/README.md

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+# Triangle
+
+Welcome to Triangle on Exercism's Elixir Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## Instructions
+
+Determine if a triangle is equilateral, isosceles, or scalene.
+
+An _equilateral_ triangle has all three sides the same length.
+
+An _isosceles_ triangle has at least two sides the same length.
+(It is sometimes specified as having exactly two sides the same length, but for the purposes of this exercise we'll say at least two.)
+
+A _scalene_ triangle has all sides of different lengths.
+
+## Note
+
+For a shape to be a triangle at all, all sides have to be of length > 0, and the sum of the lengths of any two sides must be greater than or equal to the length of the third side.
+
+In equations:
+
+Let `a`, `b`, and `c` be sides of the triangle.
+Then all three of the following expressions must be true:
+
+```text
+a + b ≥ c
+b + c ≥ a
+a + c ≥ b
+```
+
+See [Triangle Inequality][triangle-inequality]
+
+[triangle-inequality]: https://en.wikipedia.org/wiki/Triangle_inequality
+
+## Source
+
+### Created by
+
+- @rubysolo
+
+### Contributed to by
+
+- @andrewsardone
+- @angelikatyborska
+- @Cohen-Carlisle
+- @dalexj
+- @devonestes
+- @jinyeow
+- @lpil
+- @neenjaw
+- @parkerl
+- @ryanzidago
+- @sotojuan
+- @Teapane
+- @waiting-for-dev
+
+### Based on
+
+The Ruby Koans triangle project, parts 1 & 2 - https://web.archive.org/web/20220831105330/http://rubykoans.com

elixir/triangle/lib/triangle.ex

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+defmodule Triangle do
+  @type kind :: :equilateral | :isosceles | :scalene
+
+  @doc """
+  Return the kind of triangle of a triangle with 'a', 'b' and 'c' as lengths.
+  """
+  @spec kind(number, number, number) :: {:ok, kind} | {:error, String.t()}
+  def kind(a, b, c) when a <= 0 or b <= 0 or c <= 0, do: {:error, "all side lengths must be positive"}
+  def kind(a, b, c) when a + b <= c or a + c <= b or b + c <= a, do: {:error, "side lengths violate triangle inequality"}
+  def kind(a, a, a), do: {:ok, :equilateral}
+  def kind(a, b, c) when a == b or b == c or c == a, do: {:ok, :isosceles}
+  def kind(_a, _b, _c), do: {:ok, :scalene}
+end

elixir/triangle/mix.exs

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+defmodule Triangle.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :triangle,
+      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/triangle/test/test_helper.exs

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

elixir/triangle/test/triangle_test.exs

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+defmodule TriangleTest do
+  use ExUnit.Case
+
+  test "equilateral triangles have equal sides" do
+    assert Triangle.kind(2, 2, 2) == {:ok, :equilateral}
+  end
+
+  test "larger equilateral triangles also have equal sides" do
+    assert Triangle.kind(10, 10, 10) == {:ok, :equilateral}
+  end
+
+  test "equilateral triangles can have float sides" do
+    assert Triangle.kind(0.5, 0.5, 0.5) == {:ok, :equilateral}
+  end
+
+  test "isosceles triangles have last two sides equal" do
+    assert Triangle.kind(3, 4, 4) == {:ok, :isosceles}
+  end
+
+  test "isosceles triangles have first and last sides equal" do
+    assert Triangle.kind(4, 3, 4) == {:ok, :isosceles}
+  end
+
+  test "isosceles triangles have two first sides equal" do
+    assert Triangle.kind(4, 4, 3) == {:ok, :isosceles}
+  end
+
+  test "isosceles triangles have in fact exactly two sides equal" do
+    assert Triangle.kind(10, 10, 2) == {:ok, :isosceles}
+  end
+
+  test "isosceles triangles can have float sides" do
+    assert Triangle.kind(0.5, 0.4, 0.5) == {:ok, :isosceles}
+  end
+
+  test "scalene triangles have no equal sides" do
+    assert Triangle.kind(3, 4, 5) == {:ok, :scalene}
+  end
+
+  test "scalene triangles have no equal sides at a larger scale too" do
+    assert Triangle.kind(10, 11, 12) == {:ok, :scalene}
+  end
+
+  test "scalene triangles have no equal sides in descending order either" do
+    assert Triangle.kind(5, 4, 2) == {:ok, :scalene}
+  end
+
+  test "scalene triangles can have float sides" do
+    assert Triangle.kind(0.4, 0.6, 0.3) == {:ok, :scalene}
+  end
+
+  test "triangles with no size are illegal" do
+    assert Triangle.kind(0, 0, 0) == {:error, "all side lengths must be positive"}
+  end
+
+  test "triangles with negative sides are illegal" do
+    assert Triangle.kind(3, 4, -5) == {:error, "all side lengths must be positive"}
+  end
+
+  test "first triangle inequality violation" do
+    assert Triangle.kind(1, 1, 3) == {:error, "side lengths violate triangle inequality"}
+  end
+
+  test "second triangle inequality violation" do
+    assert Triangle.kind(1, 3, 1) == {:error, "side lengths violate triangle inequality"}
+  end
+
+  test "third triangle inequality violation" do
+    assert Triangle.kind(3, 1, 1) == {:error, "side lengths violate triangle inequality"}
+  end
+
+  test "another triangle inequality violation" do
+    assert Triangle.kind(7, 3, 2) == {:error, "side lengths violate triangle inequality"}
+  end
+end