grains

elixir/grains/.exercism/config.json

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+{
+  "authors": [
+    "rubysolo"
+  ],
+  "contributors": [
+    "andrewsardone",
+    "angelikatyborska",
+    "bunnymatic",
+    "Cohen-Carlisle",
+    "dalexj",
+    "devonestes",
+    "elasticdog",
+    "henrik",
+    "herminiotorres",
+    "jinyeow",
+    "lpil",
+    "neenjaw",
+    "parkerl",
+    "petehuang",
+    "pminten",
+    "sotojuan",
+    "Teapane",
+    "waiting-for-dev"
+  ],
+  "files": {
+    "solution": [
+      "lib/grains.ex"
+    ],
+    "test": [
+      "test/grains_test.exs"
+    ],
+    "example": [
+      ".meta/example.ex"
+    ]
+  },
+  "blurb": "Calculate the number of grains of wheat on a chessboard given that the number on each square doubles.",
+  "source": "The CodeRanch Cattle Drive, Assignment 6",
+  "source_url": "https://coderanch.com/wiki/718824/Grains"
+}

elixir/grains/.exercism/metadata.json

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+{"track":"elixir","exercise":"grains","id":"cfa89389b43c46c79214bc6e2ad0038c","url":"https://exercism.org/tracks/elixir/exercises/grains","handle":"negrienko","is_requester":true,"auto_approve":false}

elixir/grains/.formatter.exs

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

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

elixir/grains/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/grains.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/grains/README.md

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+# Grains
+
+Welcome to Grains on Exercism's Elixir Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## Instructions
+
+Calculate the number of grains of wheat on a chessboard given that the number on each square doubles.
+
+There once was a wise servant who saved the life of a prince.
+The king promised to pay whatever the servant could dream up.
+Knowing that the king loved chess, the servant told the king he would like to have grains of wheat.
+One grain on the first square of a chess board, with the number of grains doubling on each successive square.
+
+There are 64 squares on a chessboard (where square 1 has one grain, square 2 has two grains, and so on).
+
+Write code that shows:
+
+- how many grains were on a given square, and
+- the total number of grains on the chessboard
+
+## Source
+
+### Created by
+
+- @rubysolo
+
+### Contributed to by
+
+- @andrewsardone
+- @angelikatyborska
+- @bunnymatic
+- @Cohen-Carlisle
+- @dalexj
+- @devonestes
+- @elasticdog
+- @henrik
+- @herminiotorres
+- @jinyeow
+- @lpil
+- @neenjaw
+- @parkerl
+- @petehuang
+- @pminten
+- @sotojuan
+- @Teapane
+- @waiting-for-dev
+
+### Based on
+
+The CodeRanch Cattle Drive, Assignment 6 - https://coderanch.com/wiki/718824/Grains

elixir/grains/lib/grains.ex

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+defmodule Grains do
+  @doc """
+  Calculate two to the power of the input minus one.
+  """
+  @spec square(pos_integer()) :: {:ok, pos_integer()} | {:error, String.t()}
+  def square(number) when number > 64 or number < 1, do: {:error, "The requested square must be between 1 and 64 (inclusive)"}
+  def square(number), do: {:ok, 2 ** (number - 1)}
+
+  @doc """
+  Adds square of each number from 1 to 64.
+  """
+  @spec total :: {:ok, pos_integer()}
+  def total, do: {:ok, 2 ** 64 - 1}
+end

elixir/grains/mix.exs

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+defmodule Grains.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :grains,
+      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/grains/test/grains_test.exs

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+defmodule GrainsTest do
+  use ExUnit.Case
+
+  test "square 1" do
+    assert Grains.square(1) === {:ok, 1}
+  end
+
+  test "square 2" do
+    assert Grains.square(2) === {:ok, 2}
+  end
+
+  test "square 3" do
+    assert Grains.square(3) === {:ok, 4}
+  end
+
+  test "square 4" do
+    assert Grains.square(4) === {:ok, 8}
+  end
+
+  test "square 16" do
+    assert Grains.square(16) === {:ok, 32768}
+  end
+
+  test "square 32" do
+    assert Grains.square(32) === {:ok, 2_147_483_648}
+  end
+
+  test "square 64" do
+    assert Grains.square(64) === {:ok, 9_223_372_036_854_775_808}
+  end
+
+  test "total grains" do
+    assert Grains.total() === {:ok, 18_446_744_073_709_551_615}
+  end
+
+  test "square greater than 64 returns an error" do
+    assert Grains.square(65) ===
+             {:error, "The requested square must be between 1 and 64 (inclusive)"}
+  end
+
+  test "negative square returns an error" do
+    assert Grains.square(-1) ===
+             {:error, "The requested square must be between 1 and 64 (inclusive)"}
+  end
+
+  test "square 0 returns an error" do
+    assert Grains.square(0) ===
+             {:error, "The requested square must be between 1 and 64 (inclusive)"}
+  end
+end

elixir/grains/test/test_helper.exs

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