DNA -> RNA transformation

elixir/rna-transcription/README.md

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+# RNA Transcription
+
+Given a DNA strand, return its RNA complement (per RNA transcription).
+
+Both DNA and RNA strands are a sequence of nucleotides.
+
+The four nucleotides found in DNA are adenine (**A**), cytosine (**C**),
+guanine (**G**) and thymine (**T**).
+
+The four nucleotides found in RNA are adenine (**A**), cytosine (**C**),
+guanine (**G**) and uracil (**U**).
+
+Given a DNA strand, its transcribed RNA strand is formed by replacing
+each nucleotide with its complement:
+
+* `G` -> `C`
+* `C` -> `G`
+* `T` -> `A`
+* `A` -> `U`
+
+## 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
+
+Hyperphysics [http://hyperphysics.phy-astr.gsu.edu/hbase/Organic/transcription.html](http://hyperphysics.phy-astr.gsu.edu/hbase/Organic/transcription.html)
+
+## Submitting Incomplete Solutions
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.

elixir/rna-transcription/lib/rna_transcription.ex

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+defmodule RnaTranscription do
+  @doc """
+  Transcribes a character list representing DNA nucleotides to RNA
+
+  ## Examples
+
+  iex> RnaTranscription.to_rna('ACTG')
+  'UGAC'
+  """
+  @spec to_rna([char]) :: [char]
+  def to_rna(dna) do
+    Enum.map(dna, &(dna_to_rna(&1)))
+  end
+
+  @spec dna_to_rna(char) :: char
+  def dna_to_rna(strand) do
+    case strand do
+      ?A -> ?U
+      ?C -> ?G
+      ?T -> ?A
+      ?G -> ?C
+    end
+  end
+end

elixir/rna-transcription/mix.exs

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+defmodule RnaTranscription.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :rna_transcription,
+      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/rna-transcription/test/rna_transcription_test.exs

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+defmodule RnaTranscriptionTest do
+  use ExUnit.Case
+
+  # @tag :pending
+  test "transcribes guanine to cytosine" do
+    assert RnaTranscription.to_rna('G') == 'C'
+  end
+
+  # @tag :pending
+  test "transcribes cytosine to guanine" do
+    assert RnaTranscription.to_rna('C') == 'G'
+  end
+
+  # @tag :pending
+  test "transcribes thymidine to adenine" do
+    assert RnaTranscription.to_rna('T') == 'A'
+  end
+
+  # @tag :pending
+  test "transcribes adenine to uracil" do
+    assert RnaTranscription.to_rna('A') == 'U'
+  end
+
+  # @tag :pending
+  test "it transcribes all dna nucleotides to rna equivalents" do
+    assert RnaTranscription.to_rna('ACGTGGTCTTAA') == 'UGCACCAGAAUU'
+  end
+end

elixir/rna-transcription/test/test_helper.exs

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