rotational-cipher

roman-numerals/lib/roman_numerals.ex

@@ -52,8 +52,7 @@ defmodule RomanNumerals do
   def numeral(number) do
     number
     |> Integer.to_string
-    |> String.split("")
-    |> Enum.reject(fn n -> n == "" end)
+    |> String.graphemes
     |> Enum.reverse
     |> Enum.with_index
     |> Enum.map(&(val(&1)))

rotational-cipher/.exercism/metadata.json

@@ -0,0 +1 @@
+{"track":"elixir","exercise":"rotational-cipher","id":"138e013b55404c058e2011d383b14c1d","url":"https://exercism.io/my/solutions/138e013b55404c058e2011d383b14c1d","handle":"jnaomi","is_requester":true,"auto_approve":false}

rotational-cipher/.formatter.exs

@@ -0,0 +1,4 @@
+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

rotational-cipher/.gitignore

@@ -0,0 +1,24 @@
+# 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").
+rotational_cipher-*.tar
+

rotational-cipher/README.md

@@ -0,0 +1,73 @@
+# Rotational Cipher
+
+Create an implementation of the rotational cipher, also sometimes called the Caesar cipher.
+
+The Caesar cipher is a simple shift cipher that relies on
+transposing all the letters in the alphabet using an integer key
+between `0` and `26`. Using a key of `0` or `26` will always yield
+the same output due to modular arithmetic. The letter is shifted
+for as many values as the value of the key.
+
+The general notation for rotational ciphers is `ROT + <key>`.
+The most commonly used rotational cipher is `ROT13`.
+
+A `ROT13` on the Latin alphabet would be as follows:
+
+```text
+Plain:  abcdefghijklmnopqrstuvwxyz
+Cipher: nopqrstuvwxyzabcdefghijklm
+```
+
+It is stronger than the Atbash cipher because it has 27 possible keys, and 25 usable keys.
+
+Ciphertext is written out in the same formatting as the input including spaces and punctuation.
+
+## Examples
+
+- ROT5  `omg` gives `trl`
+- ROT0  `c` gives `c`
+- ROT26 `Cool` gives `Cool`
+- ROT13 `The quick brown fox jumps over the lazy dog.` gives `Gur dhvpx oebja sbk whzcf bire gur ynml qbt.`
+- ROT13 `Gur dhvpx oebja sbk whzcf bire gur ynml qbt.` gives `The quick brown fox jumps over the lazy dog.`
+
+## Running tests
+
+Execute the tests with:
+
+```bash
+$ mix test
+```
+
+### Pending tests
+
+In the test suites, all but the first test have been 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
+```
+
+Or, you can enable all the tests by commenting out the
+`ExUnit.configure` line in the test suite.
+
+```elixir
+# ExUnit.configure exclude: :pending, trace: true
+```
+
+If you're stuck on something, it may help to look at some of
+the [available resources](https://exercism.io/tracks/elixir/resources)
+out there where answers might be found.
+
+## Source
+
+Wikipedia [https://en.wikipedia.org/wiki/Caesar_cipher](https://en.wikipedia.org/wiki/Caesar_cipher)
+
+## Submitting Incomplete Solutions
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.

rotational-cipher/lib/rotational_cipher.ex

@@ -0,0 +1,33 @@
+defmodule RotationalCipher do
+  @doc """
+  Given a plaintext and amount to shift by, return a rotated string.
+
+  Example:
+  iex> RotationalCipher.rotate("Attack at dawn", 13)
+  "Nggnpx ng qnja"
+  """
+  @letters "abcdefghijklmnopqrstuvwxyz" 
+  @capital "ABCDEFGHIJKLMNOPQRSTUVWXYZ" 
+
+  @spec rotate(text :: String.t(), shift :: integer) :: String.t()
+  def rotate(text, shift) do
+    text
+    |> String.graphemes
+    |> Enum.map(fn x -> 
+      cond do
+        String.contains?(@letters, x) -> rotate_element(@letters, x, shift)
+        String.contains?(@capital, x) -> rotate_element(@capital, x, shift)
+        true -> x
+      end
+    end)
+    |> Enum.join
+
+  end
+
+  def rotate_element(alphabet, element, shift) do
+    {el_idx, _} = :binary.match(alphabet, element)
+    new_idx = rem(el_idx + shift, alphabet |> String.length)
+
+    String.at(alphabet, new_idx)
+  end
+end

rotational-cipher/mix.exs

@@ -0,0 +1,28 @@
+defmodule RotationalCipher.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :rotational_cipher,
+      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

rotational-cipher/test/rotational_cipher_test.exs

@@ -0,0 +1,75 @@
+defmodule RotationalCipherTest do
+  use ExUnit.Case
+
+  # @tag :pending
+  test "rotate a by 1" do
+    plaintext = "a"
+    shift = 1
+    assert RotationalCipher.rotate(plaintext, shift) == "b"
+  end
+
+  # @tag :pending
+  test "rotate a by 26, same output as input" do
+    plaintext = "a"
+    shift = 26
+    assert RotationalCipher.rotate(plaintext, shift) == "a"
+  end
+
+  # @tag :pending
+  test "rotate a by 0, same output as input" do
+    plaintext = "a"
+    shift = 0
+    assert RotationalCipher.rotate(plaintext, shift) == "a"
+  end
+
+  # @tag :pending
+  test "rotate m by 13" do
+    plaintext = "m"
+    shift = 13
+    assert RotationalCipher.rotate(plaintext, shift) == "z"
+  end
+
+  # @tag :pending
+  test "rotate n by 13 with wrap around alphabet" do
+    plaintext = "n"
+    shift = 13
+    assert RotationalCipher.rotate(plaintext, shift) == "a"
+  end
+
+  # @tag :pending
+  test "rotate capital letters" do
+    plaintext = "OMG"
+    shift = 5
+    assert RotationalCipher.rotate(plaintext, shift) == "TRL"
+  end
+
+  # @tag :pending
+  test "rotate spaces" do
+    plaintext = "O M G"
+    shift = 5
+    assert RotationalCipher.rotate(plaintext, shift) == "T R L"
+  end
+
+  # @tag :pending
+  test "rotate numbers" do
+    plaintext = "Testing 1 2 3 testing"
+    shift = 4
+    assert RotationalCipher.rotate(plaintext, shift) == "Xiwxmrk 1 2 3 xiwxmrk"
+  end
+
+  # @tag :pending
+  test "rotate punctuation" do
+    plaintext = "Let's eat, Grandma!"
+    shift = 21
+    assert RotationalCipher.rotate(plaintext, shift) == "Gzo'n zvo, Bmviyhv!"
+  end
+
+  # @tag :pending
+  test "rotate all letters" do
+    plaintext = "The quick brown fox jumps over the lazy dog."
+    shift = 13
+
+    assert RotationalCipher.rotate(plaintext, shift) ==
+             "Gur dhvpx oebja sbk whzcf bire gur ynml qbt."
+  end
+end

rotational-cipher/test/test_helper.exs

@@ -0,0 +1,2 @@
+ExUnit.start()
+ExUnit.configure(exclude: :pending, trace: true)