secret_handshake

elixir/secret-handshake/.exercism/config.json

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+{
+  "authors": [
+    "DoggettCK"
+  ],
+  "contributors": [
+    "angelikatyborska",
+    "Cohen-Carlisle",
+    "devonestes",
+    "mlopes",
+    "neenjaw",
+    "sotojuan"
+  ],
+  "files": {
+    "solution": [
+      "lib/secret_handshake.ex"
+    ],
+    "test": [
+      "test/secret_handshake_test.exs"
+    ],
+    "example": [
+      ".meta/example.ex"
+    ]
+  },
+  "blurb": "Given a decimal number, convert it to the appropriate sequence of events for a secret handshake.",
+  "source": "Bert, in Mary Poppins",
+  "source_url": "https://www.imdb.com/title/tt0058331/quotes/?item=qt0437047"
+}

elixir/secret-handshake/.exercism/metadata.json

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+{"track":"elixir","exercise":"secret-handshake","id":"a6cee5c3d5854a26823d4e65de58e330","url":"https://exercism.org/tracks/elixir/exercises/secret-handshake","handle":"negrienko","is_requester":true,"auto_approve":false}

elixir/secret-handshake/.formatter.exs

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

elixir/secret-handshake/.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").
+secret_handshake-*.tar
+

elixir/secret-handshake/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/secret_handshake.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/secret-handshake/HINTS.md

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+# Hints
+
+## General
+
+- Use `Bitwise` (or div/rem).
+- If you use `Bitwise`, an easy way to see if a particular bit is set is to compare
+the binary AND (`&&&`) of a set of bits with the particular bit pattern you
+want to check, and determine if the result is the same as the pattern you're
+checking.

elixir/secret-handshake/README.md

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+# Secret Handshake
+
+Welcome to Secret Handshake 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
+
+You are starting a secret coding club with some friends and friends-of-friends.
+Not everyone knows each other, so you and your friends have decided to create a secret handshake that you can use to recognize that someone is a member.
+You don't want anyone who isn't in the know to be able to crack the code.
+
+You've designed the code so that one person says a number between 1 and 31, and the other person turns it into a series of actions.
+
+## Instructions
+
+Your task is to convert a number between 1 and 31 to a sequence of actions in the secret handshake.
+
+The sequence of actions is chosen by looking at the rightmost five digits of the number once it's been converted to binary.
+Start at the right-most digit and move left.
+
+The actions for each number place are:
+
+```plaintext
+00001 = wink
+00010 = double blink
+00100 = close your eyes
+01000 = jump
+10000 = Reverse the order of the operations in the secret handshake.
+```
+
+Let's use the number `9` as an example:
+
+- 9 in binary is `1001`.
+- The digit that is farthest to the right is 1, so the first action is `wink`.
+- Going left, the next digit is 0, so there is no double-blink.
+- Going left again, the next digit is 0, so you leave your eyes open.
+- Going left again, the next digit is 1, so you jump.
+
+That was the last digit, so the final code is:
+
+```plaintext
+wink, jump
+```
+
+Given the number 26, which is `11010` in binary, we get the following actions:
+
+- double blink
+- jump
+- reverse actions
+
+The secret handshake for 26 is therefore:
+
+```plaintext
+jump, double blink
+```
+
+~~~~exercism/note
+If you aren't sure what binary is or how it works, check out [this binary tutorial][intro-to-binary].
+
+[intro-to-binary]: https://medium.com/basecs/bits-bytes-building-with-binary-13cb4289aafa
+~~~~
+
+## Source
+
+### Created by
+
+- @DoggettCK
+
+### Contributed to by
+
+- @angelikatyborska
+- @Cohen-Carlisle
+- @devonestes
+- @mlopes
+- @neenjaw
+- @sotojuan
+
+### Based on
+
+Bert, in Mary Poppins - https://www.imdb.com/title/tt0058331/quotes/?item=qt0437047

elixir/secret-handshake/lib/secret_handshake.ex

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+defmodule SecretHandshake do
+  @doc """
+  Determine the actions of a secret handshake based on the binary
+  representation of the given `code`.
+
+  If the following bits are set, include the corresponding action in your list
+  of commands, in order from lowest to highest.
+
+  1 1 = wink
+  2 10 = double blink
+  4 100 = close your eyes
+  8 1000 = jump
+
+  16 10000 = Reverse the order of the operations in the secret handshake
+  """
+
+  @coms %{
+    1 => "wink",
+    2 => "double blink",
+    4 => "close your eyes",
+    8 => "jump",
+    16 => "reverse"
+  }
+
+  @spec commands(code :: integer) :: list(String.t())
+  def commands(code) do
+    @coms
+    |> Map.keys()
+    |> Enum.reduce([], &if(Bitwise.band(code, &1) == &1, do: [@coms[&1] | &2], else: &2))
+    |> case do
+      ["reverse" | tail] -> tail
+      reversed_list -> Enum.reverse(reversed_list)
+    end
+  end
+end

elixir/secret-handshake/mix.exs

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+defmodule SecretHandshake.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :secret_handshake,
+      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/secret-handshake/test/secret_handshake_test.exs

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+defmodule SecretHandshakeTest do
+  use ExUnit.Case
+
+  describe "Create a handshake for a number" do
+    #@tag :pending
+    test "wink for 1" do
+      assert SecretHandshake.commands(1) == ["wink"]
+    end
+
+    #@tag :pending
+    test "double blink for 10" do
+      assert SecretHandshake.commands(2) == ["double blink"]
+    end
+
+    #@tag :pending
+    test "close your eyes for 100" do
+      assert SecretHandshake.commands(4) == ["close your eyes"]
+    end
+
+    #@tag :pending
+    test "jump for 1000" do
+      assert SecretHandshake.commands(8) == ["jump"]
+    end
+
+    #@tag :pending
+    test "combine two actions" do
+      assert SecretHandshake.commands(3) == ["wink", "double blink"]
+    end
+
+    #@tag :pending
+    test "reverse two actions" do
+      assert SecretHandshake.commands(19) == ["double blink", "wink"]
+    end
+
+    #@tag :pending
+    test "reversing one action gives the same action" do
+      assert SecretHandshake.commands(24) == ["jump"]
+    end
+
+    #@tag :pending
+    test "reversing no actions still gives no actions" do
+      assert SecretHandshake.commands(16) == []
+    end
+
+    #@tag :pending
+    test "all possible actions" do
+      assert SecretHandshake.commands(15) == ["wink", "double blink", "close your eyes", "jump"]
+    end
+
+    #@tag :pending
+    test "reverse all possible actions" do
+      assert SecretHandshake.commands(31) == ["jump", "close your eyes", "double blink", "wink"]
+    end
+
+    #@tag :pending
+    test "do nothing for zero" do
+      assert SecretHandshake.commands(0) == []
+    end
+
+    #@tag :pending
+    test "do nothing if lower 5 bits not set" do
+      assert SecretHandshake.commands(32) == []
+    end
+  end
+end

elixir/secret-handshake/test/test_helper.exs

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