mcrmfc's solution to Wordy on the Ruby 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.

Parse and evaluate simple math word problems returning the answer as an integer.

Iteration 1 — Addition

Add two numbers together.

What is 5 plus 13?

Evaluates to 18.

Handle large numbers and negative numbers.

Iteration 2 — Subtraction, Multiplication and Division

Now, perform the other three operations.

What is 7 minus 5?

What is 6 multiplied by 4?

What is 25 divided by 5?

Iteration 3 — Multiple Operations

Handle a set of operations, in sequence.

Since these are verbal word problems, evaluate the expression from left-to-right, ignoring the typical order of operations.

What is 5 plus 13 plus 6?

What is 3 plus 2 multiplied by 3?

15 (i.e. not 9)

Bonus — Exponentials

If you'd like, handle exponentials.

What is 2 raised to the 5th power?

For installation and learning resources, refer to the exercism help page.

For running the tests provided, you will need the Minitest gem. Open a terminal window and run the following command to install minitest:

gem install minitest

If you would like color output, you can require 'minitest/pride' in the test file, or note the alternative instruction, below, for running the test file.

Run the tests from the exercise directory using the following command:

ruby wordy_test.rb

To include color from the command line:

ruby -r minitest/pride wordy_test.rb

Source

Inspired by one of the generated questions in 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.

wordy_test.rb

require 'minitest/autorun'
require_relative 'wordy'

# Common test data version: 1.0.0 5b8ad58
class WordyTest < Minitest::Test
  def test_addition
    # skip
    question = 'What is 1 plus 1?'
    assert_equal(2, WordProblem.new(question).answer)
  end

  def test_more_addition
    skip
    question = 'What is 53 plus 2?'
    assert_equal(55, WordProblem.new(question).answer)
  end

  def test_addition_with_negative_numbers
    skip
    question = 'What is -1 plus -10?'
    assert_equal(-11, WordProblem.new(question).answer)
  end

  def test_large_addition
    skip
    question = 'What is 123 plus 45678?'
    assert_equal(45801, WordProblem.new(question).answer)
  end

  def test_subtraction
    skip
    question = 'What is 4 minus -12?'
    assert_equal(16, WordProblem.new(question).answer)
  end

  def test_multiplication
    skip
    question = 'What is -3 multiplied by 25?'
    assert_equal(-75, WordProblem.new(question).answer)
  end

  def test_division
    skip
    question = 'What is 33 divided by -3?'
    assert_equal(-11, WordProblem.new(question).answer)
  end

  def test_multiple_additions
    skip
    question = 'What is 1 plus 1 plus 1?'
    assert_equal(3, WordProblem.new(question).answer)
  end

  def test_addition_and_subtraction
    skip
    question = 'What is 1 plus 5 minus -2?'
    assert_equal(8, WordProblem.new(question).answer)
  end

  def test_multiple_subtraction
    skip
    question = 'What is 20 minus 4 minus 13?'
    assert_equal(3, WordProblem.new(question).answer)
  end

  def test_subtraction_then_addition
    skip
    question = 'What is 17 minus 6 plus 3?'
    assert_equal(14, WordProblem.new(question).answer)
  end

  def test_multiple_multiplication
    skip
    question = 'What is 2 multiplied by -2 multiplied by 3?'
    assert_equal(-12, WordProblem.new(question).answer)
  end

  def test_addition_and_multiplication
    skip
    question = 'What is -3 plus 7 multiplied by -2?'
    answer = WordProblem.new(question).answer
    message = "You should ignore order of precedence. -3 + 7 * -2 = -8, not #{answer}"
    assert_equal(-8, answer, message)
  end

  def test_multiple_division
    skip
    question = 'What is -12 divided by 2 divided by -3?'
    assert_equal(2, WordProblem.new(question).answer)
  end

  def test_unknown_operation
    skip
    question = 'What is 52 cubed?'
    assert_raises ArgumentError do
      WordProblem.new(question).answer
    end
  end

  def test_non_math_question
    skip
    question = 'Who is the President of the United States?'
    assert_raises ArgumentError do
      WordProblem.new(question).answer
    end
  end

  # Problems in exercism evolve over time, as we find better ways to ask
  # questions.
  # The version number refers to the version of the problem you solved,
  # not your solution.
  #
  # Define a constant named VERSION inside of the top level BookKeeping
  # module, which may be placed near the end of your file.
  #
  # In your file, it will look like this:
  #
  # module BookKeeping
  #   VERSION = 1 # Where the version number matches the one in the test.
  # end
  #
  # If you are curious, read more about constants on RubyDoc:
  # http://ruby-doc.org/docs/ruby-doc-bundle/UsersGuide/rg/constants.html

  def test_bookkeeping
    skip
    assert_equal 1, BookKeeping::VERSION
  end
end

# construct calculation from english
class WordProblem
  attr_reader :answer

  OP_MAP = {
    'plus'       => '+',
    'minus'      => '-',
    'multiplied' => '*',
    'divided'    => '/'
  }

  def initialize(str)
    ops = operations(str)
    @answer = calculate(str, ops)
  end

  def operations(str)
    operations = Regexp.new(OP_MAP.keys.join('|'))
    fail ArgumentError unless str =~ Regexp.new(operations)
    str.scan(operations).map { |o| OP_MAP[o] }
  end

  def calculate(str, ops)
    nums = str.scan(/-?\d+/).map(&:to_i)
    ops.each_with_index
      .reduce(nums.first) { |a, (e, i)| a.send(e, nums[i + 1]) }
  end
end

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mcrmfc's solution

to Wordy in the Ruby Track