thekeele's solution to Twelve Days on the Elixir track

Instructions

Test suite

Solution

Note:

This solution was written on an old version of Exercism. The tests below might not correspond to the solution code, and the exercise may have changed since this code was written.

Output the lyrics to 'The Twelve Days of Christmas'.

On the first day of Christmas my true love gave to me, a Partridge in a Pear Tree.

On the second day of Christmas my true love gave to me, two Turtle Doves, and a Partridge in a Pear Tree.

On the third day of Christmas my true love gave to me, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.

On the fourth day of Christmas my true love gave to me, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.

On the fifth day of Christmas my true love gave to me, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.

On the sixth day of Christmas my true love gave to me, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.

On the seventh day of Christmas my true love gave to me, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.

On the eighth day of Christmas my true love gave to me, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.

On the ninth day of Christmas my true love gave to me, nine Ladies Dancing, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.

On the tenth day of Christmas my true love gave to me, ten Lords-a-Leaping, nine Ladies Dancing, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.

On the eleventh day of Christmas my true love gave to me, eleven Pipers Piping, ten Lords-a-Leaping, nine Ladies Dancing, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.

On the twelfth day of Christmas my true love gave to me, twelve Drummers Drumming, eleven Pipers Piping, ten Lords-a-Leaping, nine Ladies Dancing, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.

Running tests

Execute the tests with:

$ elixir twelve_days_test.exs

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:

# @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.

# ExUnit.configure exclude: :pending, trace: true

For more detailed information about the Elixir track, please see the help page.

Source

Wikipedia http://en.wikipedia.org/wiki/The_Twelve_Days_of_Christmas_(song)

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

twelve_days_test.exs

if !System.get_env("EXERCISM_TEST_EXAMPLES") do
  Code.load_file("twelve_days.exs", __DIR__)
end

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

defmodule TwelveDaysTest do
  use ExUnit.Case

  describe "verse" do
    # @tag :pending
    test "first verse" do
      assert TwelveDays.verse(1) ==
               "On the first day of Christmas my true love gave to me, a Partridge in a Pear Tree."
    end

    @tag :pending
    test "sixth verse" do
      assert TwelveDays.verse(6) ==
               "On the sixth day of Christmas my true love gave to me, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree."
    end

    @tag :pending
    test "last verse" do
      assert TwelveDays.verse(12) ==
               "On the twelfth day of Christmas my true love gave to me, twelve Drummers Drumming, eleven Pipers Piping, ten Lords-a-Leaping, nine Ladies Dancing, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree."
    end
  end

  describe "verses" do
    @tag :pending
    test "1-3" do
      assert TwelveDays.verses(1, 3) ==
               """
               On the first day of Christmas my true love gave to me, a Partridge in a Pear Tree.
               On the second day of Christmas my true love gave to me, two Turtle Doves, and a Partridge in a Pear Tree.
               On the third day of Christmas my true love gave to me, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
               """
               |> String.trim()
    end

    @tag :pending
    test "4-6" do
      assert TwelveDays.verses(4, 6) ==
               """
               On the fourth day of Christmas my true love gave to me, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
               On the fifth day of Christmas my true love gave to me, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
               On the sixth day of Christmas my true love gave to me, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
               """
               |> String.trim()
    end

    @tag :pending
    test "1-12" do
      assert TwelveDays.verses(1, 12) ==
               """
               On the first day of Christmas my true love gave to me, a Partridge in a Pear Tree.
               On the second day of Christmas my true love gave to me, two Turtle Doves, and a Partridge in a Pear Tree.
               On the third day of Christmas my true love gave to me, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
               On the fourth day of Christmas my true love gave to me, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
               On the fifth day of Christmas my true love gave to me, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
               On the sixth day of Christmas my true love gave to me, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
               On the seventh day of Christmas my true love gave to me, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
               On the eighth day of Christmas my true love gave to me, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
               On the ninth day of Christmas my true love gave to me, nine Ladies Dancing, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
               On the tenth day of Christmas my true love gave to me, ten Lords-a-Leaping, nine Ladies Dancing, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
               On the eleventh day of Christmas my true love gave to me, eleven Pipers Piping, ten Lords-a-Leaping, nine Ladies Dancing, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
               On the twelfth day of Christmas my true love gave to me, twelve Drummers Drumming, eleven Pipers Piping, ten Lords-a-Leaping, nine Ladies Dancing, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
               """
               |> String.trim()
    end
  end

  describe "sing" do
    @tag :pending
    test "all 12 verses" do
      assert TwelveDays.sing() ==
               """
               On the first day of Christmas my true love gave to me, a Partridge in a Pear Tree.
               On the second day of Christmas my true love gave to me, two Turtle Doves, and a Partridge in a Pear Tree.
               On the third day of Christmas my true love gave to me, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
               On the fourth day of Christmas my true love gave to me, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
               On the fifth day of Christmas my true love gave to me, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
               On the sixth day of Christmas my true love gave to me, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
               On the seventh day of Christmas my true love gave to me, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
               On the eighth day of Christmas my true love gave to me, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
               On the ninth day of Christmas my true love gave to me, nine Ladies Dancing, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
               On the tenth day of Christmas my true love gave to me, ten Lords-a-Leaping, nine Ladies Dancing, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
               On the eleventh day of Christmas my true love gave to me, eleven Pipers Piping, ten Lords-a-Leaping, nine Ladies Dancing, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
               On the twelfth day of Christmas my true love gave to me, twelve Drummers Drumming, eleven Pipers Piping, ten Lords-a-Leaping, nine Ladies Dancing, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
               """
               |> String.trim()
    end
  end
end

defmodule TwelveDays do
  @twelve_days %{
    1 => {"first", "a Partridge in a Pear Tree."},
    2 => {"second", "two Turtle Doves"},
    3 => {"third", "three French Hens"},
    4 => {"fourth", "four Calling Birds"},
    5 => {"fifth", "five Gold Rings"},
    6 => {"sixth", "six Geese-a-Laying"},
    7 => {"seventh", "seven Swans-a-Swimming"},
    8 => {"eighth", "eight Maids-a-Milking"},
    9 => {"ninth", "nine Ladies Dancing"},
    10 => {"tenth", "ten Lords-a-Leaping"},
    11 => {"eleventh", "eleven Pipers Piping"},
    12 => {"twelfth", "twelve Drummers Drumming"}
  }

  @doc """
  Given a `number`, return the song's verse for that specific day, including
  all gifts for previous days in the same line.
  """
  @spec verse(number :: integer) :: String.t()
  def verse(number) when number == 1 do
    {day, verse} = @twelve_days[number]

    start(day) <> verse
  end
  def verse(number) when number > 1 do
    {day, _} = @twelve_days[number]

    for current <- number..1, into: start(day) <> "" do
      {_, verse} = @twelve_days[current]

      unless current == 1 do
        verse <> ", "
      else
        "and " <> verse
      end
    end
  end

  defp start(day) do
    "On the #{day} day of Christmas my true love gave to me, "
  end

  @doc """
  Given a `starting_verse` and an `ending_verse`, return the verses for each
  included day, one per line.
  """
  @spec verses(starting_verse :: integer, ending_verse :: integer) :: String.t()
  def verses(starting_verse, ending_verse) do
    verses =
      for current <- starting_verse..ending_verse, into: "" do
        verse(current) <> "\n"
      end

    String.trim_trailing(verses)
  end

  @doc """
  Sing all 12 verses, in order, one verse per line.
  """
  @spec sing():: String.t()
  def sing do
    verses(1, 12)
  end
end

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thekeele's solution

to Twelve Days in the Elixir Track