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to Scrabble Score in the Elixir Track

Published at Jul 13 2018 · 0 comments
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.

Given a word, compute the scrabble score for that word.

Letter Values

You'll need these:

Letter                           Value
A, E, I, O, U, L, N, R, S, T       1
D, G                               2
B, C, M, P                         3
F, H, V, W, Y                      4
K                                  5
J, X                               8
Q, Z                               10

Examples

"cabbage" should be scored as worth 14 points:

  • 3 points for C
  • 1 point for A, twice
  • 3 points for B, twice
  • 2 points for G
  • 1 point for E

And to total:

  • 3 + 2*1 + 2*3 + 2 + 1
  • = 3 + 2 + 6 + 3
  • = 5 + 9
  • = 14

Extensions

  • You can play a double or a triple letter.
  • You can play a double or a triple word.

Running tests

Execute the tests with:

$ elixir scrabble_score_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

Inspired by the Extreme Startup game https://github.com/rchatley/extreme_startup

Submitting Incomplete Solutions

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

scrabble_score_test.exs

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

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

defmodule ScrabbleScoreTest do
  use ExUnit.Case

  # @tag :pending
  test "empty word scores zero" do
    assert Scrabble.score("") == 0
  end

  @tag :pending
  test "whitespace scores zero" do
    assert Scrabble.score(" \t\n") == 0
  end

  @tag :pending
  test "scores very short word" do
    assert Scrabble.score("a") == 1
  end

  @tag :pending
  test "scores other very short word" do
    assert Scrabble.score("f") == 4
  end

  @tag :pending
  test "simple word scores the number of letters" do
    assert Scrabble.score("street") == 6
  end

  @tag :pending
  test "complicated word scores more" do
    assert Scrabble.score("quirky") == 22
  end

  @tag :pending
  test "scores are case insensitive" do
    assert Scrabble.score("OXYPHENBUTAZONE") == 41
  end

  @tag :pending
  test "convenient scoring" do
    assert Scrabble.score("alacrity") == 13
  end
end
defmodule Scrabble do

  # COULD map value to array of letters, or string, but that would
  # make code more complex, and updates more cumbersome.
  @letter_values %{
    "A" =>   1,
    "B" =>   3,
    "C" =>   3,
    "D" =>   2,
    "E" =>   1,
    "F" =>   4,
    "G" =>   2,
    "H" =>   4,
    "I" =>   1,
    "J" =>   8,
    "K" =>   5,
    "L" =>   1,
    "M" =>   3,
    "N" =>   1,
    "O" =>   1,
    "P" =>   3,
    "Q" =>  10,
    "R" =>   1,
    "S" =>   1,
    "T" =>   1,
    "U" =>   1,
    "V" =>   4,
    "W" =>   4,
    "X" =>   8,
    "Y" =>   4,
    "Z" =>  10
  }

  @doc """
  Calculate the scrabble score for the word.
  """
  @spec score(String.t) :: non_neg_integer
  def score(word) do
    word
    |> String.upcase
    |> String.graphemes
    |> Enum.map(&letter_value/1)
    |> Enum.sum
  end

  # COULD have inlined this, but extracting it
  # makes score/1 easier to grok
  # by staying closer to same level of abstraction
  defp letter_value(letter) do
    Map.get(@letter_values, letter, 0)
  end

end

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