hamming

elixir/hamming/.exercism/config.json

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+{
+  "authors": [
+    "Teapane"
+  ],
+  "contributors": [
+    "angelikatyborska",
+    "Cohen-Carlisle",
+    "dalexj",
+    "devonestes",
+    "jedschneider",
+    "lpil",
+    "neenjaw",
+    "parkerl",
+    "percygrunwald",
+    "sotojuan",
+    "veelenga",
+    "waiting-for-dev"
+  ],
+  "files": {
+    "solution": [
+      "lib/hamming.ex"
+    ],
+    "test": [
+      "test/hamming_test.exs"
+    ],
+    "example": [
+      ".meta/example.ex"
+    ]
+  },
+  "blurb": "Calculate the Hamming difference between two DNA strands.",
+  "source": "The Calculating Point Mutations problem at Rosalind",
+  "source_url": "https://rosalind.info/problems/hamm/"
+}

elixir/hamming/.exercism/metadata.json

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+{"track":"elixir","exercise":"hamming","id":"834311640e76451ab99f7b24cbe83404","url":"https://exercism.org/tracks/elixir/exercises/hamming","handle":"negrienko","is_requester":true,"auto_approve":false}

elixir/hamming/.formatter.exs

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

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

elixir/hamming/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/hamming.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/hamming/README.md

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+# Hamming
+
+Welcome to Hamming on Exercism's Elixir Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## Instructions
+
+Calculate the Hamming Distance between two DNA strands.
+
+Your body is made up of cells that contain DNA.
+Those cells regularly wear out and need replacing, which they achieve by dividing into daughter cells.
+In fact, the average human body experiences about 10 quadrillion cell divisions in a lifetime!
+
+When cells divide, their DNA replicates too.
+Sometimes during this process mistakes happen and single pieces of DNA get encoded with the incorrect information.
+If we compare two strands of DNA and count the differences between them we can see how many mistakes occurred.
+This is known as the "Hamming Distance".
+
+We read DNA using the letters C,A,G and T.
+Two strands might look like this:
+
+    GAGCCTACTAACGGGAT
+    CATCGTAATGACGGCCT
+    ^ ^ ^  ^ ^    ^^
+
+They have 7 differences, and therefore the Hamming Distance is 7.
+
+The Hamming Distance is useful for lots of things in science, not just biology, so it's a nice phrase to be familiar with :)
+
+## Implementation notes
+
+The Hamming distance is only defined for sequences of equal length, so an attempt to calculate it between sequences of different lengths should not work.
+
+## Source
+
+### Created by
+
+- @Teapane
+
+### Contributed to by
+
+- @angelikatyborska
+- @Cohen-Carlisle
+- @dalexj
+- @devonestes
+- @jedschneider
+- @lpil
+- @neenjaw
+- @parkerl
+- @percygrunwald
+- @sotojuan
+- @veelenga
+- @waiting-for-dev
+
+### Based on
+
+The Calculating Point Mutations problem at Rosalind - https://rosalind.info/problems/hamm/

elixir/hamming/lib/hamming.ex

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+defmodule Hamming do
+  @doc """
+  Returns number of differences between two strands of DNA, known as the Hamming Distance.
+
+  ## Examples
+
+  iex> Hamming.hamming_distance(~c"AAGTCATA", ~c"TAGCGATC")
+  {:ok, 4}
+  """
+  @spec hamming_distance([char], [char]) :: {:ok, non_neg_integer} | {:error, String.t()}
+  def hamming_distance(strand1, strand2) when length(strand1) != length(strand2), do: {:error, "strands must be of equal length"}
+  def hamming_distance(strand1, strand2) do
+    {:ok, Enum.count(Enum.zip(strand1, strand2), fn {s1, s2} -> s1 != s2 end)}
+  end
+end

elixir/hamming/mix.exs

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+defmodule Hamming.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :hamming,
+      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/hamming/test/hamming_test.exs

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+defmodule HammingTest do
+  use ExUnit.Case
+
+  test "empty strands" do
+    assert Hamming.hamming_distance(~c"", ~c"") == {:ok, 0}
+  end
+
+  test "single letter identical strands" do
+    assert Hamming.hamming_distance(~c"A", ~c"A") == {:ok, 0}
+  end
+
+  test "single letter different strands" do
+    assert Hamming.hamming_distance(~c"G", ~c"T") == {:ok, 1}
+  end
+
+  test "long identical strands" do
+    assert Hamming.hamming_distance(~c"GGACTGAAATCTG", ~c"GGACTGAAATCTG") == {:ok, 0}
+  end
+
+  test "long different strands" do
+    assert Hamming.hamming_distance(~c"GGACGGATTCTG", ~c"AGGACGGATTCT") == {:ok, 9}
+  end
+
+  test "disallow first strand longer" do
+    assert {:error, "strands must be of equal length"} =
+             Hamming.hamming_distance(~c"AATG", ~c"AAA")
+  end
+
+  test "disallow second strand longer" do
+    assert {:error, "strands must be of equal length"} =
+             Hamming.hamming_distance(~c"ATA", ~c"AGTG")
+  end
+
+  test "disallow empty first strand" do
+    assert {:error, "strands must be of equal length"} = Hamming.hamming_distance(~c"", ~c"G")
+  end
+
+  test "disallow empty second strand" do
+    assert {:error, "strands must be of equal length"} = Hamming.hamming_distance(~c"G", ~c"")
+  end
+end

elixir/hamming/test/test_helper.exs

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